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 @node Interrupted System Calls
5868 @subsection Interrupted System Calls
5870 @cindex thread breakpoints and system calls
5871 @cindex system calls and thread breakpoints
5872 @cindex premature return from system calls
5873 There is an unfortunate side effect when using @value{GDBN} to debug
5874 multi-threaded programs. If one thread stops for a
5875 breakpoint, or for some other reason, and another thread is blocked in a
5876 system call, then the system call may return prematurely. This is a
5877 consequence of the interaction between multiple threads and the signals
5878 that @value{GDBN} uses to implement breakpoints and other events that
5881 To handle this problem, your program should check the return value of
5882 each system call and react appropriately. This is good programming
5885 For example, do not write code like this:
5891 The call to @code{sleep} will return early if a different thread stops
5892 at a breakpoint or for some other reason.
5894 Instead, write this:
5899 unslept = sleep (unslept);
5902 A system call is allowed to return early, so the system is still
5903 conforming to its specification. But @value{GDBN} does cause your
5904 multi-threaded program to behave differently than it would without
5907 Also, @value{GDBN} uses internal breakpoints in the thread library to
5908 monitor certain events such as thread creation and thread destruction.
5909 When such an event happens, a system call in another thread may return
5910 prematurely, even though your program does not appear to stop.
5913 @subsection Observer Mode
5915 If you want to build on non-stop mode and observe program behavior
5916 without any chance of disruption by @value{GDBN}, you can set
5917 variables to disable all of the debugger's attempts to modify state,
5918 whether by writing memory, inserting breakpoints, etc. These operate
5919 at a low level, intercepting operations from all commands.
5921 When all of these are set to @code{off}, then @value{GDBN} is said to
5922 be @dfn{observer mode}. As a convenience, the variable
5923 @code{observer} can be set to disable these, plus enable non-stop
5926 Note that @value{GDBN} will not prevent you from making nonsensical
5927 combinations of these settings. For instance, if you have enabled
5928 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5929 then breakpoints that work by writing trap instructions into the code
5930 stream will still not be able to be placed.
5935 @item set observer on
5936 @itemx set observer off
5937 When set to @code{on}, this disables all the permission variables
5938 below (except for @code{insert-fast-tracepoints}), plus enables
5939 non-stop debugging. Setting this to @code{off} switches back to
5940 normal debugging, though remaining in non-stop mode.
5943 Show whether observer mode is on or off.
5945 @kindex may-write-registers
5946 @item set may-write-registers on
5947 @itemx set may-write-registers off
5948 This controls whether @value{GDBN} will attempt to alter the values of
5949 registers, such as with assignment expressions in @code{print}, or the
5950 @code{jump} command. It defaults to @code{on}.
5952 @item show may-write-registers
5953 Show the current permission to write registers.
5955 @kindex may-write-memory
5956 @item set may-write-memory on
5957 @itemx set may-write-memory off
5958 This controls whether @value{GDBN} will attempt to alter the contents
5959 of memory, such as with assignment expressions in @code{print}. It
5960 defaults to @code{on}.
5962 @item show may-write-memory
5963 Show the current permission to write memory.
5965 @kindex may-insert-breakpoints
5966 @item set may-insert-breakpoints on
5967 @itemx set may-insert-breakpoints off
5968 This controls whether @value{GDBN} will attempt to insert breakpoints.
5969 This affects all breakpoints, including internal breakpoints defined
5970 by @value{GDBN}. It defaults to @code{on}.
5972 @item show may-insert-breakpoints
5973 Show the current permission to insert breakpoints.
5975 @kindex may-insert-tracepoints
5976 @item set may-insert-tracepoints on
5977 @itemx set may-insert-tracepoints off
5978 This controls whether @value{GDBN} will attempt to insert (regular)
5979 tracepoints at the beginning of a tracing experiment. It affects only
5980 non-fast tracepoints, fast tracepoints being under the control of
5981 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5983 @item show may-insert-tracepoints
5984 Show the current permission to insert tracepoints.
5986 @kindex may-insert-fast-tracepoints
5987 @item set may-insert-fast-tracepoints on
5988 @itemx set may-insert-fast-tracepoints off
5989 This controls whether @value{GDBN} will attempt to insert fast
5990 tracepoints at the beginning of a tracing experiment. It affects only
5991 fast tracepoints, regular (non-fast) tracepoints being under the
5992 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5994 @item show may-insert-fast-tracepoints
5995 Show the current permission to insert fast tracepoints.
5997 @kindex may-interrupt
5998 @item set may-interrupt on
5999 @itemx set may-interrupt off
6000 This controls whether @value{GDBN} will attempt to interrupt or stop
6001 program execution. When this variable is @code{off}, the
6002 @code{interrupt} command will have no effect, nor will
6003 @kbd{Ctrl-c}. It defaults to @code{on}.
6005 @item show may-interrupt
6006 Show the current permission to interrupt or stop the program.
6010 @node Reverse Execution
6011 @chapter Running programs backward
6012 @cindex reverse execution
6013 @cindex running programs backward
6015 When you are debugging a program, it is not unusual to realize that
6016 you have gone too far, and some event of interest has already happened.
6017 If the target environment supports it, @value{GDBN} can allow you to
6018 ``rewind'' the program by running it backward.
6020 A target environment that supports reverse execution should be able
6021 to ``undo'' the changes in machine state that have taken place as the
6022 program was executing normally. Variables, registers etc.@: should
6023 revert to their previous values. Obviously this requires a great
6024 deal of sophistication on the part of the target environment; not
6025 all target environments can support reverse execution.
6027 When a program is executed in reverse, the instructions that
6028 have most recently been executed are ``un-executed'', in reverse
6029 order. The program counter runs backward, following the previous
6030 thread of execution in reverse. As each instruction is ``un-executed'',
6031 the values of memory and/or registers that were changed by that
6032 instruction are reverted to their previous states. After executing
6033 a piece of source code in reverse, all side effects of that code
6034 should be ``undone'', and all variables should be returned to their
6035 prior values@footnote{
6036 Note that some side effects are easier to undo than others. For instance,
6037 memory and registers are relatively easy, but device I/O is hard. Some
6038 targets may be able undo things like device I/O, and some may not.
6040 The contract between @value{GDBN} and the reverse executing target
6041 requires only that the target do something reasonable when
6042 @value{GDBN} tells it to execute backwards, and then report the
6043 results back to @value{GDBN}. Whatever the target reports back to
6044 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
6045 assumes that the memory and registers that the target reports are in a
6046 consistant state, but @value{GDBN} accepts whatever it is given.
6049 If you are debugging in a target environment that supports
6050 reverse execution, @value{GDBN} provides the following commands.
6053 @kindex reverse-continue
6054 @kindex rc @r{(@code{reverse-continue})}
6055 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6056 @itemx rc @r{[}@var{ignore-count}@r{]}
6057 Beginning at the point where your program last stopped, start executing
6058 in reverse. Reverse execution will stop for breakpoints and synchronous
6059 exceptions (signals), just like normal execution. Behavior of
6060 asynchronous signals depends on the target environment.
6062 @kindex reverse-step
6063 @kindex rs @r{(@code{step})}
6064 @item reverse-step @r{[}@var{count}@r{]}
6065 Run the program backward until control reaches the start of a
6066 different source line; then stop it, and return control to @value{GDBN}.
6068 Like the @code{step} command, @code{reverse-step} will only stop
6069 at the beginning of a source line. It ``un-executes'' the previously
6070 executed source line. If the previous source line included calls to
6071 debuggable functions, @code{reverse-step} will step (backward) into
6072 the called function, stopping at the beginning of the @emph{last}
6073 statement in the called function (typically a return statement).
6075 Also, as with the @code{step} command, if non-debuggable functions are
6076 called, @code{reverse-step} will run thru them backward without stopping.
6078 @kindex reverse-stepi
6079 @kindex rsi @r{(@code{reverse-stepi})}
6080 @item reverse-stepi @r{[}@var{count}@r{]}
6081 Reverse-execute one machine instruction. Note that the instruction
6082 to be reverse-executed is @emph{not} the one pointed to by the program
6083 counter, but the instruction executed prior to that one. For instance,
6084 if the last instruction was a jump, @code{reverse-stepi} will take you
6085 back from the destination of the jump to the jump instruction itself.
6087 @kindex reverse-next
6088 @kindex rn @r{(@code{reverse-next})}
6089 @item reverse-next @r{[}@var{count}@r{]}
6090 Run backward to the beginning of the previous line executed in
6091 the current (innermost) stack frame. If the line contains function
6092 calls, they will be ``un-executed'' without stopping. Starting from
6093 the first line of a function, @code{reverse-next} will take you back
6094 to the caller of that function, @emph{before} the function was called,
6095 just as the normal @code{next} command would take you from the last
6096 line of a function back to its return to its caller
6097 @footnote{Unless the code is too heavily optimized.}.
6099 @kindex reverse-nexti
6100 @kindex rni @r{(@code{reverse-nexti})}
6101 @item reverse-nexti @r{[}@var{count}@r{]}
6102 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6103 in reverse, except that called functions are ``un-executed'' atomically.
6104 That is, if the previously executed instruction was a return from
6105 another function, @code{reverse-nexti} will continue to execute
6106 in reverse until the call to that function (from the current stack
6109 @kindex reverse-finish
6110 @item reverse-finish
6111 Just as the @code{finish} command takes you to the point where the
6112 current function returns, @code{reverse-finish} takes you to the point
6113 where it was called. Instead of ending up at the end of the current
6114 function invocation, you end up at the beginning.
6116 @kindex set exec-direction
6117 @item set exec-direction
6118 Set the direction of target execution.
6119 @item set exec-direction reverse
6120 @cindex execute forward or backward in time
6121 @value{GDBN} will perform all execution commands in reverse, until the
6122 exec-direction mode is changed to ``forward''. Affected commands include
6123 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6124 command cannot be used in reverse mode.
6125 @item set exec-direction forward
6126 @value{GDBN} will perform all execution commands in the normal fashion.
6127 This is the default.
6131 @node Process Record and Replay
6132 @chapter Recording Inferior's Execution and Replaying It
6133 @cindex process record and replay
6134 @cindex recording inferior's execution and replaying it
6136 On some platforms, @value{GDBN} provides a special @dfn{process record
6137 and replay} target that can record a log of the process execution, and
6138 replay it later with both forward and reverse execution commands.
6141 When this target is in use, if the execution log includes the record
6142 for the next instruction, @value{GDBN} will debug in @dfn{replay
6143 mode}. In the replay mode, the inferior does not really execute code
6144 instructions. Instead, all the events that normally happen during
6145 code execution are taken from the execution log. While code is not
6146 really executed in replay mode, the values of registers (including the
6147 program counter register) and the memory of the inferior are still
6148 changed as they normally would. Their contents are taken from the
6152 If the record for the next instruction is not in the execution log,
6153 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6154 inferior executes normally, and @value{GDBN} records the execution log
6157 The process record and replay target supports reverse execution
6158 (@pxref{Reverse Execution}), even if the platform on which the
6159 inferior runs does not. However, the reverse execution is limited in
6160 this case by the range of the instructions recorded in the execution
6161 log. In other words, reverse execution on platforms that don't
6162 support it directly can only be done in the replay mode.
6164 When debugging in the reverse direction, @value{GDBN} will work in
6165 replay mode as long as the execution log includes the record for the
6166 previous instruction; otherwise, it will work in record mode, if the
6167 platform supports reverse execution, or stop if not.
6169 For architecture environments that support process record and replay,
6170 @value{GDBN} provides the following commands:
6173 @kindex target record
6174 @kindex target record-full
6175 @kindex target record-btrace
6178 @kindex record btrace
6182 @item record @var{method}
6183 This command starts the process record and replay target. The
6184 recording method can be specified as parameter. Without a parameter
6185 the command uses the @code{full} recording method. The following
6186 recording methods are available:
6190 Full record/replay recording using @value{GDBN}'s software record and
6191 replay implementation. This method allows replaying and reverse
6195 Hardware-supported instruction recording. This method does not allow
6196 replaying and reverse execution.
6198 This recording method may not be available on all processors.
6201 The process record and replay target can only debug a process that is
6202 already running. Therefore, you need first to start the process with
6203 the @kbd{run} or @kbd{start} commands, and then start the recording
6204 with the @kbd{record @var{method}} command.
6206 Both @code{record @var{method}} and @code{rec @var{method}} are
6207 aliases of @code{target record-@var{method}}.
6209 @cindex displaced stepping, and process record and replay
6210 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6211 will be automatically disabled when process record and replay target
6212 is started. That's because the process record and replay target
6213 doesn't support displaced stepping.
6215 @cindex non-stop mode, and process record and replay
6216 @cindex asynchronous execution, and process record and replay
6217 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6218 the asynchronous execution mode (@pxref{Background Execution}), not
6219 all recording methods are available. The @code{full} recording method
6220 does not support these two modes.
6225 Stop the process record and replay target. When process record and
6226 replay target stops, the entire execution log will be deleted and the
6227 inferior will either be terminated, or will remain in its final state.
6229 When you stop the process record and replay target in record mode (at
6230 the end of the execution log), the inferior will be stopped at the
6231 next instruction that would have been recorded. In other words, if
6232 you record for a while and then stop recording, the inferior process
6233 will be left in the same state as if the recording never happened.
6235 On the other hand, if the process record and replay target is stopped
6236 while in replay mode (that is, not at the end of the execution log,
6237 but at some earlier point), the inferior process will become ``live''
6238 at that earlier state, and it will then be possible to continue the
6239 usual ``live'' debugging of the process from that state.
6241 When the inferior process exits, or @value{GDBN} detaches from it,
6242 process record and replay target will automatically stop itself.
6246 Go to a specific location in the execution log. There are several
6247 ways to specify the location to go to:
6250 @item record goto begin
6251 @itemx record goto start
6252 Go to the beginning of the execution log.
6254 @item record goto end
6255 Go to the end of the execution log.
6257 @item record goto @var{n}
6258 Go to instruction number @var{n} in the execution log.
6262 @item record save @var{filename}
6263 Save the execution log to a file @file{@var{filename}}.
6264 Default filename is @file{gdb_record.@var{process_id}}, where
6265 @var{process_id} is the process ID of the inferior.
6267 This command may not be available for all recording methods.
6269 @kindex record restore
6270 @item record restore @var{filename}
6271 Restore the execution log from a file @file{@var{filename}}.
6272 File must have been created with @code{record save}.
6274 @kindex set record full
6275 @item set record full insn-number-max @var{limit}
6276 @itemx set record full insn-number-max unlimited
6277 Set the limit of instructions to be recorded for the @code{full}
6278 recording method. Default value is 200000.
6280 If @var{limit} is a positive number, then @value{GDBN} will start
6281 deleting instructions from the log once the number of the record
6282 instructions becomes greater than @var{limit}. For every new recorded
6283 instruction, @value{GDBN} will delete the earliest recorded
6284 instruction to keep the number of recorded instructions at the limit.
6285 (Since deleting recorded instructions loses information, @value{GDBN}
6286 lets you control what happens when the limit is reached, by means of
6287 the @code{stop-at-limit} option, described below.)
6289 If @var{limit} is @code{unlimited} or zero, @value{GDBN} will never
6290 delete recorded instructions from the execution log. The number of
6291 recorded instructions is limited only by the available memory.
6293 @kindex show record full
6294 @item show record full insn-number-max
6295 Show the limit of instructions to be recorded with the @code{full}
6298 @item set record full stop-at-limit
6299 Control the behavior of the @code{full} recording method when the
6300 number of recorded instructions reaches the limit. If ON (the
6301 default), @value{GDBN} will stop when the limit is reached for the
6302 first time and ask you whether you want to stop the inferior or
6303 continue running it and recording the execution log. If you decide
6304 to continue recording, each new recorded instruction will cause the
6305 oldest one to be deleted.
6307 If this option is OFF, @value{GDBN} will automatically delete the
6308 oldest record to make room for each new one, without asking.
6310 @item show record full stop-at-limit
6311 Show the current setting of @code{stop-at-limit}.
6313 @item set record full memory-query
6314 Control the behavior when @value{GDBN} is unable to record memory
6315 changes caused by an instruction for the @code{full} recording method.
6316 If ON, @value{GDBN} will query whether to stop the inferior in that
6319 If this option is OFF (the default), @value{GDBN} will automatically
6320 ignore the effect of such instructions on memory. Later, when
6321 @value{GDBN} replays this execution log, it will mark the log of this
6322 instruction as not accessible, and it will not affect the replay
6325 @item show record full memory-query
6326 Show the current setting of @code{memory-query}.
6330 Show various statistics about the recording depending on the recording
6335 For the @code{full} recording method, it shows the state of process
6336 record and its in-memory execution log buffer, including:
6340 Whether in record mode or replay mode.
6342 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6344 Highest recorded instruction number.
6346 Current instruction about to be replayed (if in replay mode).
6348 Number of instructions contained in the execution log.
6350 Maximum number of instructions that may be contained in the execution log.
6354 For the @code{btrace} recording method, it shows the number of
6355 instructions that have been recorded and the number of blocks of
6356 sequential control-flow that is formed by the recorded instructions.
6359 @kindex record delete
6362 When record target runs in replay mode (``in the past''), delete the
6363 subsequent execution log and begin to record a new execution log starting
6364 from the current address. This means you will abandon the previously
6365 recorded ``future'' and begin recording a new ``future''.
6367 @kindex record instruction-history
6368 @kindex rec instruction-history
6369 @item record instruction-history
6370 Disassembles instructions from the recorded execution log. By
6371 default, ten instructions are disassembled. This can be changed using
6372 the @code{set record instruction-history-size} command. Instructions
6373 are printed in execution order. There are several ways to specify
6374 what part of the execution log to disassemble:
6377 @item record instruction-history @var{insn}
6378 Disassembles ten instructions starting from instruction number
6381 @item record instruction-history @var{insn}, +/-@var{n}
6382 Disassembles @var{n} instructions around instruction number
6383 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6384 @var{n} instructions after instruction number @var{insn}. If
6385 @var{n} is preceded with @code{-}, disassembles @var{n}
6386 instructions before instruction number @var{insn}.
6388 @item record instruction-history
6389 Disassembles ten more instructions after the last disassembly.
6391 @item record instruction-history -
6392 Disassembles ten more instructions before the last disassembly.
6394 @item record instruction-history @var{begin} @var{end}
6395 Disassembles instructions beginning with instruction number
6396 @var{begin} until instruction number @var{end}. The instruction
6397 number @var{end} is not included.
6400 This command may not be available for all recording methods.
6403 @item set record instruction-history-size @var{size}
6404 @itemx set record instruction-history-size unlimited
6405 Define how many instructions to disassemble in the @code{record
6406 instruction-history} command. The default value is 10.
6407 A @var{size} of @code{unlimited} means unlimited instructions.
6410 @item show record instruction-history-size
6411 Show how many instructions to disassemble in the @code{record
6412 instruction-history} command.
6414 @kindex record function-call-history
6415 @kindex rec function-call-history
6416 @item record function-call-history
6417 Prints the execution history at function granularity. It prints one
6418 line for each sequence of instructions that belong to the same
6419 function giving the name of that function, the source lines
6420 for this instruction sequence (if the @code{/l} modifier is
6421 specified), and the instructions numbers that form the sequence (if
6422 the @code{/i} modifier is specified).
6425 (@value{GDBP}) @b{list 1, 10}
6436 (@value{GDBP}) @b{record function-call-history /l}
6442 By default, ten lines are printed. This can be changed using the
6443 @code{set record function-call-history-size} command. Functions are
6444 printed in execution order. There are several ways to specify what
6448 @item record function-call-history @var{func}
6449 Prints ten functions starting from function number @var{func}.
6451 @item record function-call-history @var{func}, +/-@var{n}
6452 Prints @var{n} functions around function number @var{func}. If
6453 @var{n} is preceded with @code{+}, prints @var{n} functions after
6454 function number @var{func}. If @var{n} is preceded with @code{-},
6455 prints @var{n} functions before function number @var{func}.
6457 @item record function-call-history
6458 Prints ten more functions after the last ten-line print.
6460 @item record function-call-history -
6461 Prints ten more functions before the last ten-line print.
6463 @item record function-call-history @var{begin} @var{end}
6464 Prints functions beginning with function number @var{begin} until
6465 function number @var{end}. The function number @var{end} is not
6469 This command may not be available for all recording methods.
6471 @item set record function-call-history-size @var{size}
6472 @itemx set record function-call-history-size unlimited
6473 Define how many lines to print in the
6474 @code{record function-call-history} command. The default value is 10.
6475 A size of @code{unlimited} means unlimited lines.
6477 @item show record function-call-history-size
6478 Show how many lines to print in the
6479 @code{record function-call-history} command.
6484 @chapter Examining the Stack
6486 When your program has stopped, the first thing you need to know is where it
6487 stopped and how it got there.
6490 Each time your program performs a function call, information about the call
6492 That information includes the location of the call in your program,
6493 the arguments of the call,
6494 and the local variables of the function being called.
6495 The information is saved in a block of data called a @dfn{stack frame}.
6496 The stack frames are allocated in a region of memory called the @dfn{call
6499 When your program stops, the @value{GDBN} commands for examining the
6500 stack allow you to see all of this information.
6502 @cindex selected frame
6503 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6504 @value{GDBN} commands refer implicitly to the selected frame. In
6505 particular, whenever you ask @value{GDBN} for the value of a variable in
6506 your program, the value is found in the selected frame. There are
6507 special @value{GDBN} commands to select whichever frame you are
6508 interested in. @xref{Selection, ,Selecting a Frame}.
6510 When your program stops, @value{GDBN} automatically selects the
6511 currently executing frame and describes it briefly, similar to the
6512 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6515 * Frames:: Stack frames
6516 * Backtrace:: Backtraces
6517 * Frame Filter Management:: Managing frame filters
6518 * Selection:: Selecting a frame
6519 * Frame Info:: Information on a frame
6524 @section Stack Frames
6526 @cindex frame, definition
6528 The call stack is divided up into contiguous pieces called @dfn{stack
6529 frames}, or @dfn{frames} for short; each frame is the data associated
6530 with one call to one function. The frame contains the arguments given
6531 to the function, the function's local variables, and the address at
6532 which the function is executing.
6534 @cindex initial frame
6535 @cindex outermost frame
6536 @cindex innermost frame
6537 When your program is started, the stack has only one frame, that of the
6538 function @code{main}. This is called the @dfn{initial} frame or the
6539 @dfn{outermost} frame. Each time a function is called, a new frame is
6540 made. Each time a function returns, the frame for that function invocation
6541 is eliminated. If a function is recursive, there can be many frames for
6542 the same function. The frame for the function in which execution is
6543 actually occurring is called the @dfn{innermost} frame. This is the most
6544 recently created of all the stack frames that still exist.
6546 @cindex frame pointer
6547 Inside your program, stack frames are identified by their addresses. A
6548 stack frame consists of many bytes, each of which has its own address; each
6549 kind of computer has a convention for choosing one byte whose
6550 address serves as the address of the frame. Usually this address is kept
6551 in a register called the @dfn{frame pointer register}
6552 (@pxref{Registers, $fp}) while execution is going on in that frame.
6554 @cindex frame number
6555 @value{GDBN} assigns numbers to all existing stack frames, starting with
6556 zero for the innermost frame, one for the frame that called it,
6557 and so on upward. These numbers do not really exist in your program;
6558 they are assigned by @value{GDBN} to give you a way of designating stack
6559 frames in @value{GDBN} commands.
6561 @c The -fomit-frame-pointer below perennially causes hbox overflow
6562 @c underflow problems.
6563 @cindex frameless execution
6564 Some compilers provide a way to compile functions so that they operate
6565 without stack frames. (For example, the @value{NGCC} option
6567 @samp{-fomit-frame-pointer}
6569 generates functions without a frame.)
6570 This is occasionally done with heavily used library functions to save
6571 the frame setup time. @value{GDBN} has limited facilities for dealing
6572 with these function invocations. If the innermost function invocation
6573 has no stack frame, @value{GDBN} nevertheless regards it as though
6574 it had a separate frame, which is numbered zero as usual, allowing
6575 correct tracing of the function call chain. However, @value{GDBN} has
6576 no provision for frameless functions elsewhere in the stack.
6579 @kindex frame@r{, command}
6580 @cindex current stack frame
6581 @item frame @var{args}
6582 The @code{frame} command allows you to move from one stack frame to another,
6583 and to print the stack frame you select. @var{args} may be either the
6584 address of the frame or the stack frame number. Without an argument,
6585 @code{frame} prints the current stack frame.
6587 @kindex select-frame
6588 @cindex selecting frame silently
6590 The @code{select-frame} command allows you to move from one stack frame
6591 to another without printing the frame. This is the silent version of
6599 @cindex call stack traces
6600 A backtrace is a summary of how your program got where it is. It shows one
6601 line per frame, for many frames, starting with the currently executing
6602 frame (frame zero), followed by its caller (frame one), and on up the
6605 @anchor{backtrace-command}
6608 @kindex bt @r{(@code{backtrace})}
6611 Print a backtrace of the entire stack: one line per frame for all
6612 frames in the stack.
6614 You can stop the backtrace at any time by typing the system interrupt
6615 character, normally @kbd{Ctrl-c}.
6617 @item backtrace @var{n}
6619 Similar, but print only the innermost @var{n} frames.
6621 @item backtrace -@var{n}
6623 Similar, but print only the outermost @var{n} frames.
6625 @item backtrace full
6627 @itemx bt full @var{n}
6628 @itemx bt full -@var{n}
6629 Print the values of the local variables also. @var{n} specifies the
6630 number of frames to print, as described above.
6632 @item backtrace no-filters
6633 @itemx bt no-filters
6634 @itemx bt no-filters @var{n}
6635 @itemx bt no-filters -@var{n}
6636 @itemx bt no-filters full
6637 @itemx bt no-filters full @var{n}
6638 @itemx bt no-filters full -@var{n}
6639 Do not run Python frame filters on this backtrace. @xref{Frame
6640 Filter API}, for more information. Additionally use @ref{disable
6641 frame-filter all} to turn off all frame filters. This is only
6642 relevant when @value{GDBN} has been configured with @code{Python}
6648 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6649 are additional aliases for @code{backtrace}.
6651 @cindex multiple threads, backtrace
6652 In a multi-threaded program, @value{GDBN} by default shows the
6653 backtrace only for the current thread. To display the backtrace for
6654 several or all of the threads, use the command @code{thread apply}
6655 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6656 apply all backtrace}, @value{GDBN} will display the backtrace for all
6657 the threads; this is handy when you debug a core dump of a
6658 multi-threaded program.
6660 Each line in the backtrace shows the frame number and the function name.
6661 The program counter value is also shown---unless you use @code{set
6662 print address off}. The backtrace also shows the source file name and
6663 line number, as well as the arguments to the function. The program
6664 counter value is omitted if it is at the beginning of the code for that
6667 Here is an example of a backtrace. It was made with the command
6668 @samp{bt 3}, so it shows the innermost three frames.
6672 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6674 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6675 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6677 (More stack frames follow...)
6682 The display for frame zero does not begin with a program counter
6683 value, indicating that your program has stopped at the beginning of the
6684 code for line @code{993} of @code{builtin.c}.
6687 The value of parameter @code{data} in frame 1 has been replaced by
6688 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6689 only if it is a scalar (integer, pointer, enumeration, etc). See command
6690 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6691 on how to configure the way function parameter values are printed.
6693 @cindex optimized out, in backtrace
6694 @cindex function call arguments, optimized out
6695 If your program was compiled with optimizations, some compilers will
6696 optimize away arguments passed to functions if those arguments are
6697 never used after the call. Such optimizations generate code that
6698 passes arguments through registers, but doesn't store those arguments
6699 in the stack frame. @value{GDBN} has no way of displaying such
6700 arguments in stack frames other than the innermost one. Here's what
6701 such a backtrace might look like:
6705 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6707 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6708 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6710 (More stack frames follow...)
6715 The values of arguments that were not saved in their stack frames are
6716 shown as @samp{<optimized out>}.
6718 If you need to display the values of such optimized-out arguments,
6719 either deduce that from other variables whose values depend on the one
6720 you are interested in, or recompile without optimizations.
6722 @cindex backtrace beyond @code{main} function
6723 @cindex program entry point
6724 @cindex startup code, and backtrace
6725 Most programs have a standard user entry point---a place where system
6726 libraries and startup code transition into user code. For C this is
6727 @code{main}@footnote{
6728 Note that embedded programs (the so-called ``free-standing''
6729 environment) are not required to have a @code{main} function as the
6730 entry point. They could even have multiple entry points.}.
6731 When @value{GDBN} finds the entry function in a backtrace
6732 it will terminate the backtrace, to avoid tracing into highly
6733 system-specific (and generally uninteresting) code.
6735 If you need to examine the startup code, or limit the number of levels
6736 in a backtrace, you can change this behavior:
6739 @item set backtrace past-main
6740 @itemx set backtrace past-main on
6741 @kindex set backtrace
6742 Backtraces will continue past the user entry point.
6744 @item set backtrace past-main off
6745 Backtraces will stop when they encounter the user entry point. This is the
6748 @item show backtrace past-main
6749 @kindex show backtrace
6750 Display the current user entry point backtrace policy.
6752 @item set backtrace past-entry
6753 @itemx set backtrace past-entry on
6754 Backtraces will continue past the internal entry point of an application.
6755 This entry point is encoded by the linker when the application is built,
6756 and is likely before the user entry point @code{main} (or equivalent) is called.
6758 @item set backtrace past-entry off
6759 Backtraces will stop when they encounter the internal entry point of an
6760 application. This is the default.
6762 @item show backtrace past-entry
6763 Display the current internal entry point backtrace policy.
6765 @item set backtrace limit @var{n}
6766 @itemx set backtrace limit 0
6767 @itemx set backtrace limit unlimited
6768 @cindex backtrace limit
6769 Limit the backtrace to @var{n} levels. A value of @code{unlimited}
6770 or zero means unlimited levels.
6772 @item show backtrace limit
6773 Display the current limit on backtrace levels.
6776 You can control how file names are displayed.
6779 @item set filename-display
6780 @itemx set filename-display relative
6781 @cindex filename-display
6782 Display file names relative to the compilation directory. This is the default.
6784 @item set filename-display basename
6785 Display only basename of a filename.
6787 @item set filename-display absolute
6788 Display an absolute filename.
6790 @item show filename-display
6791 Show the current way to display filenames.
6794 @node Frame Filter Management
6795 @section Management of Frame Filters.
6796 @cindex managing frame filters
6798 Frame filters are Python based utilities to manage and decorate the
6799 output of frames. @xref{Frame Filter API}, for further information.
6801 Managing frame filters is performed by several commands available
6802 within @value{GDBN}, detailed here.
6805 @kindex info frame-filter
6806 @item info frame-filter
6807 Print a list of installed frame filters from all dictionaries, showing
6808 their name, priority and enabled status.
6810 @kindex disable frame-filter
6811 @anchor{disable frame-filter all}
6812 @item disable frame-filter @var{filter-dictionary} @var{filter-name}
6813 Disable a frame filter in the dictionary matching
6814 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6815 @var{filter-dictionary} may be @code{all}, @code{global},
6816 @code{progspace} or the name of the object file where the frame filter
6817 dictionary resides. When @code{all} is specified, all frame filters
6818 across all dictionaries are disabled. @var{filter-name} is the name
6819 of the frame filter and is used when @code{all} is not the option for
6820 @var{filter-dictionary}. A disabled frame-filter is not deleted, it
6821 may be enabled again later.
6823 @kindex enable frame-filter
6824 @item enable frame-filter @var{filter-dictionary} @var{filter-name}
6825 Enable a frame filter in the dictionary matching
6826 @var{filter-dictionary}, or @code{all}, and @var{filter-name}.
6827 @var{filter-dictionary} may be @code{all}, @code{global},
6828 @code{progspace} or the name of the object file where the frame filter
6829 dictionary resides. When @code{all} is specified, all frame filters across
6830 all dictionaries are enabled. @var{filter-name} is the name of the frame
6831 filter and is used when @code{all} is not the option for
6832 @var{filter-dictionary}.
6837 (gdb) info frame-filter
6839 global frame-filters:
6840 Priority Enabled Name
6841 1000 No PrimaryFunctionFilter
6844 progspace /build/test frame-filters:
6845 Priority Enabled Name
6846 100 Yes ProgspaceFilter
6848 objfile /build/test frame-filters:
6849 Priority Enabled Name
6850 999 Yes BuildProgra Filter
6852 (gdb) disable frame-filter /build/test BuildProgramFilter
6853 (gdb) info frame-filter
6855 global frame-filters:
6856 Priority Enabled Name
6857 1000 No PrimaryFunctionFilter
6860 progspace /build/test frame-filters:
6861 Priority Enabled Name
6862 100 Yes ProgspaceFilter
6864 objfile /build/test frame-filters:
6865 Priority Enabled Name
6866 999 No BuildProgramFilter
6868 (gdb) enable frame-filter global PrimaryFunctionFilter
6869 (gdb) info frame-filter
6871 global frame-filters:
6872 Priority Enabled Name
6873 1000 Yes PrimaryFunctionFilter
6876 progspace /build/test frame-filters:
6877 Priority Enabled Name
6878 100 Yes ProgspaceFilter
6880 objfile /build/test frame-filters:
6881 Priority Enabled Name
6882 999 No BuildProgramFilter
6885 @kindex set frame-filter priority
6886 @item set frame-filter priority @var{filter-dictionary} @var{filter-name} @var{priority}
6887 Set the @var{priority} of a frame filter in the dictionary matching
6888 @var{filter-dictionary}, and the frame filter name matching
6889 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6890 @code{progspace} or the name of the object file where the frame filter
6891 dictionary resides. @var{priority} is an integer.
6893 @kindex show frame-filter priority
6894 @item show frame-filter priority @var{filter-dictionary} @var{filter-name}
6895 Show the @var{priority} of a frame filter in the dictionary matching
6896 @var{filter-dictionary}, and the frame filter name matching
6897 @var{filter-name}. @var{filter-dictionary} may be @code{global},
6898 @code{progspace} or the name of the object file where the frame filter
6904 (gdb) info frame-filter
6906 global frame-filters:
6907 Priority Enabled Name
6908 1000 Yes PrimaryFunctionFilter
6911 progspace /build/test frame-filters:
6912 Priority Enabled Name
6913 100 Yes ProgspaceFilter
6915 objfile /build/test frame-filters:
6916 Priority Enabled Name
6917 999 No BuildProgramFilter
6919 (gdb) set frame-filter priority global Reverse 50
6920 (gdb) info frame-filter
6922 global frame-filters:
6923 Priority Enabled Name
6924 1000 Yes PrimaryFunctionFilter
6927 progspace /build/test frame-filters:
6928 Priority Enabled Name
6929 100 Yes ProgspaceFilter
6931 objfile /build/test frame-filters:
6932 Priority Enabled Name
6933 999 No BuildProgramFilter
6938 @section Selecting a Frame
6940 Most commands for examining the stack and other data in your program work on
6941 whichever stack frame is selected at the moment. Here are the commands for
6942 selecting a stack frame; all of them finish by printing a brief description
6943 of the stack frame just selected.
6946 @kindex frame@r{, selecting}
6947 @kindex f @r{(@code{frame})}
6950 Select frame number @var{n}. Recall that frame zero is the innermost
6951 (currently executing) frame, frame one is the frame that called the
6952 innermost one, and so on. The highest-numbered frame is the one for
6955 @item frame @var{addr}
6957 Select the frame at address @var{addr}. This is useful mainly if the
6958 chaining of stack frames has been damaged by a bug, making it
6959 impossible for @value{GDBN} to assign numbers properly to all frames. In
6960 addition, this can be useful when your program has multiple stacks and
6961 switches between them.
6963 On the SPARC architecture, @code{frame} needs two addresses to
6964 select an arbitrary frame: a frame pointer and a stack pointer.
6966 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6967 pointer and a program counter.
6969 On the 29k architecture, it needs three addresses: a register stack
6970 pointer, a program counter, and a memory stack pointer.
6974 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6975 advances toward the outermost frame, to higher frame numbers, to frames
6976 that have existed longer. @var{n} defaults to one.
6979 @kindex do @r{(@code{down})}
6981 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6982 advances toward the innermost frame, to lower frame numbers, to frames
6983 that were created more recently. @var{n} defaults to one. You may
6984 abbreviate @code{down} as @code{do}.
6987 All of these commands end by printing two lines of output describing the
6988 frame. The first line shows the frame number, the function name, the
6989 arguments, and the source file and line number of execution in that
6990 frame. The second line shows the text of that source line.
6998 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
7000 10 read_input_file (argv[i]);
7004 After such a printout, the @code{list} command with no arguments
7005 prints ten lines centered on the point of execution in the frame.
7006 You can also edit the program at the point of execution with your favorite
7007 editing program by typing @code{edit}.
7008 @xref{List, ,Printing Source Lines},
7012 @kindex down-silently
7014 @item up-silently @var{n}
7015 @itemx down-silently @var{n}
7016 These two commands are variants of @code{up} and @code{down},
7017 respectively; they differ in that they do their work silently, without
7018 causing display of the new frame. They are intended primarily for use
7019 in @value{GDBN} command scripts, where the output might be unnecessary and
7024 @section Information About a Frame
7026 There are several other commands to print information about the selected
7032 When used without any argument, this command does not change which
7033 frame is selected, but prints a brief description of the currently
7034 selected stack frame. It can be abbreviated @code{f}. With an
7035 argument, this command is used to select a stack frame.
7036 @xref{Selection, ,Selecting a Frame}.
7039 @kindex info f @r{(@code{info frame})}
7042 This command prints a verbose description of the selected stack frame,
7047 the address of the frame
7049 the address of the next frame down (called by this frame)
7051 the address of the next frame up (caller of this frame)
7053 the language in which the source code corresponding to this frame is written
7055 the address of the frame's arguments
7057 the address of the frame's local variables
7059 the program counter saved in it (the address of execution in the caller frame)
7061 which registers were saved in the frame
7064 @noindent The verbose description is useful when
7065 something has gone wrong that has made the stack format fail to fit
7066 the usual conventions.
7068 @item info frame @var{addr}
7069 @itemx info f @var{addr}
7070 Print a verbose description of the frame at address @var{addr}, without
7071 selecting that frame. The selected frame remains unchanged by this
7072 command. This requires the same kind of address (more than one for some
7073 architectures) that you specify in the @code{frame} command.
7074 @xref{Selection, ,Selecting a Frame}.
7078 Print the arguments of the selected frame, each on a separate line.
7082 Print the local variables of the selected frame, each on a separate
7083 line. These are all variables (declared either static or automatic)
7084 accessible at the point of execution of the selected frame.
7090 @chapter Examining Source Files
7092 @value{GDBN} can print parts of your program's source, since the debugging
7093 information recorded in the program tells @value{GDBN} what source files were
7094 used to build it. When your program stops, @value{GDBN} spontaneously prints
7095 the line where it stopped. Likewise, when you select a stack frame
7096 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
7097 execution in that frame has stopped. You can print other portions of
7098 source files by explicit command.
7100 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
7101 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
7102 @value{GDBN} under @sc{gnu} Emacs}.
7105 * List:: Printing source lines
7106 * Specify Location:: How to specify code locations
7107 * Edit:: Editing source files
7108 * Search:: Searching source files
7109 * Source Path:: Specifying source directories
7110 * Machine Code:: Source and machine code
7114 @section Printing Source Lines
7117 @kindex l @r{(@code{list})}
7118 To print lines from a source file, use the @code{list} command
7119 (abbreviated @code{l}). By default, ten lines are printed.
7120 There are several ways to specify what part of the file you want to
7121 print; see @ref{Specify Location}, for the full list.
7123 Here are the forms of the @code{list} command most commonly used:
7126 @item list @var{linenum}
7127 Print lines centered around line number @var{linenum} in the
7128 current source file.
7130 @item list @var{function}
7131 Print lines centered around the beginning of function
7135 Print more lines. If the last lines printed were printed with a
7136 @code{list} command, this prints lines following the last lines
7137 printed; however, if the last line printed was a solitary line printed
7138 as part of displaying a stack frame (@pxref{Stack, ,Examining the
7139 Stack}), this prints lines centered around that line.
7142 Print lines just before the lines last printed.
7145 @cindex @code{list}, how many lines to display
7146 By default, @value{GDBN} prints ten source lines with any of these forms of
7147 the @code{list} command. You can change this using @code{set listsize}:
7150 @kindex set listsize
7151 @item set listsize @var{count}
7152 @itemx set listsize unlimited
7153 Make the @code{list} command display @var{count} source lines (unless
7154 the @code{list} argument explicitly specifies some other number).
7155 Setting @var{count} to @code{unlimited} or 0 means there's no limit.
7157 @kindex show listsize
7159 Display the number of lines that @code{list} prints.
7162 Repeating a @code{list} command with @key{RET} discards the argument,
7163 so it is equivalent to typing just @code{list}. This is more useful
7164 than listing the same lines again. An exception is made for an
7165 argument of @samp{-}; that argument is preserved in repetition so that
7166 each repetition moves up in the source file.
7168 In general, the @code{list} command expects you to supply zero, one or two
7169 @dfn{linespecs}. Linespecs specify source lines; there are several ways
7170 of writing them (@pxref{Specify Location}), but the effect is always
7171 to specify some source line.
7173 Here is a complete description of the possible arguments for @code{list}:
7176 @item list @var{linespec}
7177 Print lines centered around the line specified by @var{linespec}.
7179 @item list @var{first},@var{last}
7180 Print lines from @var{first} to @var{last}. Both arguments are
7181 linespecs. When a @code{list} command has two linespecs, and the
7182 source file of the second linespec is omitted, this refers to
7183 the same source file as the first linespec.
7185 @item list ,@var{last}
7186 Print lines ending with @var{last}.
7188 @item list @var{first},
7189 Print lines starting with @var{first}.
7192 Print lines just after the lines last printed.
7195 Print lines just before the lines last printed.
7198 As described in the preceding table.
7201 @node Specify Location
7202 @section Specifying a Location
7203 @cindex specifying location
7206 Several @value{GDBN} commands accept arguments that specify a location
7207 of your program's code. Since @value{GDBN} is a source-level
7208 debugger, a location usually specifies some line in the source code;
7209 for that reason, locations are also known as @dfn{linespecs}.
7211 Here are all the different ways of specifying a code location that
7212 @value{GDBN} understands:
7216 Specifies the line number @var{linenum} of the current source file.
7219 @itemx +@var{offset}
7220 Specifies the line @var{offset} lines before or after the @dfn{current
7221 line}. For the @code{list} command, the current line is the last one
7222 printed; for the breakpoint commands, this is the line at which
7223 execution stopped in the currently selected @dfn{stack frame}
7224 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
7225 used as the second of the two linespecs in a @code{list} command,
7226 this specifies the line @var{offset} lines up or down from the first
7229 @item @var{filename}:@var{linenum}
7230 Specifies the line @var{linenum} in the source file @var{filename}.
7231 If @var{filename} is a relative file name, then it will match any
7232 source file name with the same trailing components. For example, if
7233 @var{filename} is @samp{gcc/expr.c}, then it will match source file
7234 name of @file{/build/trunk/gcc/expr.c}, but not
7235 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7237 @item @var{function}
7238 Specifies the line that begins the body of the function @var{function}.
7239 For example, in C, this is the line with the open brace.
7241 @item @var{function}:@var{label}
7242 Specifies the line where @var{label} appears in @var{function}.
7244 @item @var{filename}:@var{function}
7245 Specifies the line that begins the body of the function @var{function}
7246 in the file @var{filename}. You only need the file name with a
7247 function name to avoid ambiguity when there are identically named
7248 functions in different source files.
7251 Specifies the line at which the label named @var{label} appears.
7252 @value{GDBN} searches for the label in the function corresponding to
7253 the currently selected stack frame. If there is no current selected
7254 stack frame (for instance, if the inferior is not running), then
7255 @value{GDBN} will not search for a label.
7257 @item *@var{address}
7258 Specifies the program address @var{address}. For line-oriented
7259 commands, such as @code{list} and @code{edit}, this specifies a source
7260 line that contains @var{address}. For @code{break} and other
7261 breakpoint oriented commands, this can be used to set breakpoints in
7262 parts of your program which do not have debugging information or
7265 Here @var{address} may be any expression valid in the current working
7266 language (@pxref{Languages, working language}) that specifies a code
7267 address. In addition, as a convenience, @value{GDBN} extends the
7268 semantics of expressions used in locations to cover the situations
7269 that frequently happen during debugging. Here are the various forms
7273 @item @var{expression}
7274 Any expression valid in the current working language.
7276 @item @var{funcaddr}
7277 An address of a function or procedure derived from its name. In C,
7278 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7279 simply the function's name @var{function} (and actually a special case
7280 of a valid expression). In Pascal and Modula-2, this is
7281 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7282 (although the Pascal form also works).
7284 This form specifies the address of the function's first instruction,
7285 before the stack frame and arguments have been set up.
7287 @item '@var{filename}'::@var{funcaddr}
7288 Like @var{funcaddr} above, but also specifies the name of the source
7289 file explicitly. This is useful if the name of the function does not
7290 specify the function unambiguously, e.g., if there are several
7291 functions with identical names in different source files.
7294 @cindex breakpoint at static probe point
7295 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7296 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7297 applications to embed static probes. @xref{Static Probe Points}, for more
7298 information on finding and using static probes. This form of linespec
7299 specifies the location of such a static probe.
7301 If @var{objfile} is given, only probes coming from that shared library
7302 or executable matching @var{objfile} as a regular expression are considered.
7303 If @var{provider} is given, then only probes from that provider are considered.
7304 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7305 each one of those probes.
7311 @section Editing Source Files
7312 @cindex editing source files
7315 @kindex e @r{(@code{edit})}
7316 To edit the lines in a source file, use the @code{edit} command.
7317 The editing program of your choice
7318 is invoked with the current line set to
7319 the active line in the program.
7320 Alternatively, there are several ways to specify what part of the file you
7321 want to print if you want to see other parts of the program:
7324 @item edit @var{location}
7325 Edit the source file specified by @code{location}. Editing starts at
7326 that @var{location}, e.g., at the specified source line of the
7327 specified file. @xref{Specify Location}, for all the possible forms
7328 of the @var{location} argument; here are the forms of the @code{edit}
7329 command most commonly used:
7332 @item edit @var{number}
7333 Edit the current source file with @var{number} as the active line number.
7335 @item edit @var{function}
7336 Edit the file containing @var{function} at the beginning of its definition.
7341 @subsection Choosing your Editor
7342 You can customize @value{GDBN} to use any editor you want
7344 The only restriction is that your editor (say @code{ex}), recognizes the
7345 following command-line syntax:
7347 ex +@var{number} file
7349 The optional numeric value +@var{number} specifies the number of the line in
7350 the file where to start editing.}.
7351 By default, it is @file{@value{EDITOR}}, but you can change this
7352 by setting the environment variable @code{EDITOR} before using
7353 @value{GDBN}. For example, to configure @value{GDBN} to use the
7354 @code{vi} editor, you could use these commands with the @code{sh} shell:
7360 or in the @code{csh} shell,
7362 setenv EDITOR /usr/bin/vi
7367 @section Searching Source Files
7368 @cindex searching source files
7370 There are two commands for searching through the current source file for a
7375 @kindex forward-search
7376 @kindex fo @r{(@code{forward-search})}
7377 @item forward-search @var{regexp}
7378 @itemx search @var{regexp}
7379 The command @samp{forward-search @var{regexp}} checks each line,
7380 starting with the one following the last line listed, for a match for
7381 @var{regexp}. It lists the line that is found. You can use the
7382 synonym @samp{search @var{regexp}} or abbreviate the command name as
7385 @kindex reverse-search
7386 @item reverse-search @var{regexp}
7387 The command @samp{reverse-search @var{regexp}} checks each line, starting
7388 with the one before the last line listed and going backward, for a match
7389 for @var{regexp}. It lists the line that is found. You can abbreviate
7390 this command as @code{rev}.
7394 @section Specifying Source Directories
7397 @cindex directories for source files
7398 Executable programs sometimes do not record the directories of the source
7399 files from which they were compiled, just the names. Even when they do,
7400 the directories could be moved between the compilation and your debugging
7401 session. @value{GDBN} has a list of directories to search for source files;
7402 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7403 it tries all the directories in the list, in the order they are present
7404 in the list, until it finds a file with the desired name.
7406 For example, suppose an executable references the file
7407 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7408 @file{/mnt/cross}. The file is first looked up literally; if this
7409 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7410 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7411 message is printed. @value{GDBN} does not look up the parts of the
7412 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7413 Likewise, the subdirectories of the source path are not searched: if
7414 the source path is @file{/mnt/cross}, and the binary refers to
7415 @file{foo.c}, @value{GDBN} would not find it under
7416 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7418 Plain file names, relative file names with leading directories, file
7419 names containing dots, etc.@: are all treated as described above; for
7420 instance, if the source path is @file{/mnt/cross}, and the source file
7421 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7422 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7423 that---@file{/mnt/cross/foo.c}.
7425 Note that the executable search path is @emph{not} used to locate the
7428 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7429 any information it has cached about where source files are found and where
7430 each line is in the file.
7434 When you start @value{GDBN}, its source path includes only @samp{cdir}
7435 and @samp{cwd}, in that order.
7436 To add other directories, use the @code{directory} command.
7438 The search path is used to find both program source files and @value{GDBN}
7439 script files (read using the @samp{-command} option and @samp{source} command).
7441 In addition to the source path, @value{GDBN} provides a set of commands
7442 that manage a list of source path substitution rules. A @dfn{substitution
7443 rule} specifies how to rewrite source directories stored in the program's
7444 debug information in case the sources were moved to a different
7445 directory between compilation and debugging. A rule is made of
7446 two strings, the first specifying what needs to be rewritten in
7447 the path, and the second specifying how it should be rewritten.
7448 In @ref{set substitute-path}, we name these two parts @var{from} and
7449 @var{to} respectively. @value{GDBN} does a simple string replacement
7450 of @var{from} with @var{to} at the start of the directory part of the
7451 source file name, and uses that result instead of the original file
7452 name to look up the sources.
7454 Using the previous example, suppose the @file{foo-1.0} tree has been
7455 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7456 @value{GDBN} to replace @file{/usr/src} in all source path names with
7457 @file{/mnt/cross}. The first lookup will then be
7458 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7459 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7460 substitution rule, use the @code{set substitute-path} command
7461 (@pxref{set substitute-path}).
7463 To avoid unexpected substitution results, a rule is applied only if the
7464 @var{from} part of the directory name ends at a directory separator.
7465 For instance, a rule substituting @file{/usr/source} into
7466 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7467 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7468 is applied only at the beginning of the directory name, this rule will
7469 not be applied to @file{/root/usr/source/baz.c} either.
7471 In many cases, you can achieve the same result using the @code{directory}
7472 command. However, @code{set substitute-path} can be more efficient in
7473 the case where the sources are organized in a complex tree with multiple
7474 subdirectories. With the @code{directory} command, you need to add each
7475 subdirectory of your project. If you moved the entire tree while
7476 preserving its internal organization, then @code{set substitute-path}
7477 allows you to direct the debugger to all the sources with one single
7480 @code{set substitute-path} is also more than just a shortcut command.
7481 The source path is only used if the file at the original location no
7482 longer exists. On the other hand, @code{set substitute-path} modifies
7483 the debugger behavior to look at the rewritten location instead. So, if
7484 for any reason a source file that is not relevant to your executable is
7485 located at the original location, a substitution rule is the only
7486 method available to point @value{GDBN} at the new location.
7488 @cindex @samp{--with-relocated-sources}
7489 @cindex default source path substitution
7490 You can configure a default source path substitution rule by
7491 configuring @value{GDBN} with the
7492 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7493 should be the name of a directory under @value{GDBN}'s configured
7494 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7495 directory names in debug information under @var{dir} will be adjusted
7496 automatically if the installed @value{GDBN} is moved to a new
7497 location. This is useful if @value{GDBN}, libraries or executables
7498 with debug information and corresponding source code are being moved
7502 @item directory @var{dirname} @dots{}
7503 @item dir @var{dirname} @dots{}
7504 Add directory @var{dirname} to the front of the source path. Several
7505 directory names may be given to this command, separated by @samp{:}
7506 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7507 part of absolute file names) or
7508 whitespace. You may specify a directory that is already in the source
7509 path; this moves it forward, so @value{GDBN} searches it sooner.
7513 @vindex $cdir@r{, convenience variable}
7514 @vindex $cwd@r{, convenience variable}
7515 @cindex compilation directory
7516 @cindex current directory
7517 @cindex working directory
7518 @cindex directory, current
7519 @cindex directory, compilation
7520 You can use the string @samp{$cdir} to refer to the compilation
7521 directory (if one is recorded), and @samp{$cwd} to refer to the current
7522 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7523 tracks the current working directory as it changes during your @value{GDBN}
7524 session, while the latter is immediately expanded to the current
7525 directory at the time you add an entry to the source path.
7528 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7530 @c RET-repeat for @code{directory} is explicitly disabled, but since
7531 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7533 @item set directories @var{path-list}
7534 @kindex set directories
7535 Set the source path to @var{path-list}.
7536 @samp{$cdir:$cwd} are added if missing.
7538 @item show directories
7539 @kindex show directories
7540 Print the source path: show which directories it contains.
7542 @anchor{set substitute-path}
7543 @item set substitute-path @var{from} @var{to}
7544 @kindex set substitute-path
7545 Define a source path substitution rule, and add it at the end of the
7546 current list of existing substitution rules. If a rule with the same
7547 @var{from} was already defined, then the old rule is also deleted.
7549 For example, if the file @file{/foo/bar/baz.c} was moved to
7550 @file{/mnt/cross/baz.c}, then the command
7553 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7557 will tell @value{GDBN} to replace @samp{/usr/src} with
7558 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7559 @file{baz.c} even though it was moved.
7561 In the case when more than one substitution rule have been defined,
7562 the rules are evaluated one by one in the order where they have been
7563 defined. The first one matching, if any, is selected to perform
7566 For instance, if we had entered the following commands:
7569 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7570 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7574 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7575 @file{/mnt/include/defs.h} by using the first rule. However, it would
7576 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7577 @file{/mnt/src/lib/foo.c}.
7580 @item unset substitute-path [path]
7581 @kindex unset substitute-path
7582 If a path is specified, search the current list of substitution rules
7583 for a rule that would rewrite that path. Delete that rule if found.
7584 A warning is emitted by the debugger if no rule could be found.
7586 If no path is specified, then all substitution rules are deleted.
7588 @item show substitute-path [path]
7589 @kindex show substitute-path
7590 If a path is specified, then print the source path substitution rule
7591 which would rewrite that path, if any.
7593 If no path is specified, then print all existing source path substitution
7598 If your source path is cluttered with directories that are no longer of
7599 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7600 versions of source. You can correct the situation as follows:
7604 Use @code{directory} with no argument to reset the source path to its default value.
7607 Use @code{directory} with suitable arguments to reinstall the
7608 directories you want in the source path. You can add all the
7609 directories in one command.
7613 @section Source and Machine Code
7614 @cindex source line and its code address
7616 You can use the command @code{info line} to map source lines to program
7617 addresses (and vice versa), and the command @code{disassemble} to display
7618 a range of addresses as machine instructions. You can use the command
7619 @code{set disassemble-next-line} to set whether to disassemble next
7620 source line when execution stops. When run under @sc{gnu} Emacs
7621 mode, the @code{info line} command causes the arrow to point to the
7622 line specified. Also, @code{info line} prints addresses in symbolic form as
7627 @item info line @var{linespec}
7628 Print the starting and ending addresses of the compiled code for
7629 source line @var{linespec}. You can specify source lines in any of
7630 the ways documented in @ref{Specify Location}.
7633 For example, we can use @code{info line} to discover the location of
7634 the object code for the first line of function
7635 @code{m4_changequote}:
7637 @c FIXME: I think this example should also show the addresses in
7638 @c symbolic form, as they usually would be displayed.
7640 (@value{GDBP}) info line m4_changequote
7641 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7645 @cindex code address and its source line
7646 We can also inquire (using @code{*@var{addr}} as the form for
7647 @var{linespec}) what source line covers a particular address:
7649 (@value{GDBP}) info line *0x63ff
7650 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7653 @cindex @code{$_} and @code{info line}
7654 @cindex @code{x} command, default address
7655 @kindex x@r{(examine), and} info line
7656 After @code{info line}, the default address for the @code{x} command
7657 is changed to the starting address of the line, so that @samp{x/i} is
7658 sufficient to begin examining the machine code (@pxref{Memory,
7659 ,Examining Memory}). Also, this address is saved as the value of the
7660 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7665 @cindex assembly instructions
7666 @cindex instructions, assembly
7667 @cindex machine instructions
7668 @cindex listing machine instructions
7670 @itemx disassemble /m
7671 @itemx disassemble /r
7672 This specialized command dumps a range of memory as machine
7673 instructions. It can also print mixed source+disassembly by specifying
7674 the @code{/m} modifier and print the raw instructions in hex as well as
7675 in symbolic form by specifying the @code{/r}.
7676 The default memory range is the function surrounding the
7677 program counter of the selected frame. A single argument to this
7678 command is a program counter value; @value{GDBN} dumps the function
7679 surrounding this value. When two arguments are given, they should
7680 be separated by a comma, possibly surrounded by whitespace. The
7681 arguments specify a range of addresses to dump, in one of two forms:
7684 @item @var{start},@var{end}
7685 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7686 @item @var{start},+@var{length}
7687 the addresses from @var{start} (inclusive) to
7688 @code{@var{start}+@var{length}} (exclusive).
7692 When 2 arguments are specified, the name of the function is also
7693 printed (since there could be several functions in the given range).
7695 The argument(s) can be any expression yielding a numeric value, such as
7696 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7698 If the range of memory being disassembled contains current program counter,
7699 the instruction at that location is shown with a @code{=>} marker.
7702 The following example shows the disassembly of a range of addresses of
7703 HP PA-RISC 2.0 code:
7706 (@value{GDBP}) disas 0x32c4, 0x32e4
7707 Dump of assembler code from 0x32c4 to 0x32e4:
7708 0x32c4 <main+204>: addil 0,dp
7709 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7710 0x32cc <main+212>: ldil 0x3000,r31
7711 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7712 0x32d4 <main+220>: ldo 0(r31),rp
7713 0x32d8 <main+224>: addil -0x800,dp
7714 0x32dc <main+228>: ldo 0x588(r1),r26
7715 0x32e0 <main+232>: ldil 0x3000,r31
7716 End of assembler dump.
7719 Here is an example showing mixed source+assembly for Intel x86, when the
7720 program is stopped just after function prologue:
7723 (@value{GDBP}) disas /m main
7724 Dump of assembler code for function main:
7726 0x08048330 <+0>: push %ebp
7727 0x08048331 <+1>: mov %esp,%ebp
7728 0x08048333 <+3>: sub $0x8,%esp
7729 0x08048336 <+6>: and $0xfffffff0,%esp
7730 0x08048339 <+9>: sub $0x10,%esp
7732 6 printf ("Hello.\n");
7733 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7734 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7738 0x08048348 <+24>: mov $0x0,%eax
7739 0x0804834d <+29>: leave
7740 0x0804834e <+30>: ret
7742 End of assembler dump.
7745 Here is another example showing raw instructions in hex for AMD x86-64,
7748 (gdb) disas /r 0x400281,+10
7749 Dump of assembler code from 0x400281 to 0x40028b:
7750 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7751 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7752 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7753 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7754 End of assembler dump.
7757 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7758 So, for example, if you want to disassemble function @code{bar}
7759 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7760 and not @samp{disassemble foo.c:bar}.
7762 Some architectures have more than one commonly-used set of instruction
7763 mnemonics or other syntax.
7765 For programs that were dynamically linked and use shared libraries,
7766 instructions that call functions or branch to locations in the shared
7767 libraries might show a seemingly bogus location---it's actually a
7768 location of the relocation table. On some architectures, @value{GDBN}
7769 might be able to resolve these to actual function names.
7772 @kindex set disassembly-flavor
7773 @cindex Intel disassembly flavor
7774 @cindex AT&T disassembly flavor
7775 @item set disassembly-flavor @var{instruction-set}
7776 Select the instruction set to use when disassembling the
7777 program via the @code{disassemble} or @code{x/i} commands.
7779 Currently this command is only defined for the Intel x86 family. You
7780 can set @var{instruction-set} to either @code{intel} or @code{att}.
7781 The default is @code{att}, the AT&T flavor used by default by Unix
7782 assemblers for x86-based targets.
7784 @kindex show disassembly-flavor
7785 @item show disassembly-flavor
7786 Show the current setting of the disassembly flavor.
7790 @kindex set disassemble-next-line
7791 @kindex show disassemble-next-line
7792 @item set disassemble-next-line
7793 @itemx show disassemble-next-line
7794 Control whether or not @value{GDBN} will disassemble the next source
7795 line or instruction when execution stops. If ON, @value{GDBN} will
7796 display disassembly of the next source line when execution of the
7797 program being debugged stops. This is @emph{in addition} to
7798 displaying the source line itself, which @value{GDBN} always does if
7799 possible. If the next source line cannot be displayed for some reason
7800 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7801 info in the debug info), @value{GDBN} will display disassembly of the
7802 next @emph{instruction} instead of showing the next source line. If
7803 AUTO, @value{GDBN} will display disassembly of next instruction only
7804 if the source line cannot be displayed. This setting causes
7805 @value{GDBN} to display some feedback when you step through a function
7806 with no line info or whose source file is unavailable. The default is
7807 OFF, which means never display the disassembly of the next line or
7813 @chapter Examining Data
7815 @cindex printing data
7816 @cindex examining data
7819 The usual way to examine data in your program is with the @code{print}
7820 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7821 evaluates and prints the value of an expression of the language your
7822 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7823 Different Languages}). It may also print the expression using a
7824 Python-based pretty-printer (@pxref{Pretty Printing}).
7827 @item print @var{expr}
7828 @itemx print /@var{f} @var{expr}
7829 @var{expr} is an expression (in the source language). By default the
7830 value of @var{expr} is printed in a format appropriate to its data type;
7831 you can choose a different format by specifying @samp{/@var{f}}, where
7832 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7836 @itemx print /@var{f}
7837 @cindex reprint the last value
7838 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7839 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7840 conveniently inspect the same value in an alternative format.
7843 A more low-level way of examining data is with the @code{x} command.
7844 It examines data in memory at a specified address and prints it in a
7845 specified format. @xref{Memory, ,Examining Memory}.
7847 If you are interested in information about types, or about how the
7848 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7849 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7852 @cindex exploring hierarchical data structures
7854 Another way of examining values of expressions and type information is
7855 through the Python extension command @code{explore} (available only if
7856 the @value{GDBN} build is configured with @code{--with-python}). It
7857 offers an interactive way to start at the highest level (or, the most
7858 abstract level) of the data type of an expression (or, the data type
7859 itself) and explore all the way down to leaf scalar values/fields
7860 embedded in the higher level data types.
7863 @item explore @var{arg}
7864 @var{arg} is either an expression (in the source language), or a type
7865 visible in the current context of the program being debugged.
7868 The working of the @code{explore} command can be illustrated with an
7869 example. If a data type @code{struct ComplexStruct} is defined in your
7879 struct ComplexStruct
7881 struct SimpleStruct *ss_p;
7887 followed by variable declarations as
7890 struct SimpleStruct ss = @{ 10, 1.11 @};
7891 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7895 then, the value of the variable @code{cs} can be explored using the
7896 @code{explore} command as follows.
7900 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7901 the following fields:
7903 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7904 arr = <Enter 1 to explore this field of type `int [10]'>
7906 Enter the field number of choice:
7910 Since the fields of @code{cs} are not scalar values, you are being
7911 prompted to chose the field you want to explore. Let's say you choose
7912 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7913 pointer, you will be asked if it is pointing to a single value. From
7914 the declaration of @code{cs} above, it is indeed pointing to a single
7915 value, hence you enter @code{y}. If you enter @code{n}, then you will
7916 be asked if it were pointing to an array of values, in which case this
7917 field will be explored as if it were an array.
7920 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7921 Continue exploring it as a pointer to a single value [y/n]: y
7922 The value of `*(cs.ss_p)' is a struct/class of type `struct
7923 SimpleStruct' with the following fields:
7925 i = 10 .. (Value of type `int')
7926 d = 1.1100000000000001 .. (Value of type `double')
7928 Press enter to return to parent value:
7932 If the field @code{arr} of @code{cs} was chosen for exploration by
7933 entering @code{1} earlier, then since it is as array, you will be
7934 prompted to enter the index of the element in the array that you want
7938 `cs.arr' is an array of `int'.
7939 Enter the index of the element you want to explore in `cs.arr': 5
7941 `(cs.arr)[5]' is a scalar value of type `int'.
7945 Press enter to return to parent value:
7948 In general, at any stage of exploration, you can go deeper towards the
7949 leaf values by responding to the prompts appropriately, or hit the
7950 return key to return to the enclosing data structure (the @i{higher}
7951 level data structure).
7953 Similar to exploring values, you can use the @code{explore} command to
7954 explore types. Instead of specifying a value (which is typically a
7955 variable name or an expression valid in the current context of the
7956 program being debugged), you specify a type name. If you consider the
7957 same example as above, your can explore the type
7958 @code{struct ComplexStruct} by passing the argument
7959 @code{struct ComplexStruct} to the @code{explore} command.
7962 (gdb) explore struct ComplexStruct
7966 By responding to the prompts appropriately in the subsequent interactive
7967 session, you can explore the type @code{struct ComplexStruct} in a
7968 manner similar to how the value @code{cs} was explored in the above
7971 The @code{explore} command also has two sub-commands,
7972 @code{explore value} and @code{explore type}. The former sub-command is
7973 a way to explicitly specify that value exploration of the argument is
7974 being invoked, while the latter is a way to explicitly specify that type
7975 exploration of the argument is being invoked.
7978 @item explore value @var{expr}
7979 @cindex explore value
7980 This sub-command of @code{explore} explores the value of the
7981 expression @var{expr} (if @var{expr} is an expression valid in the
7982 current context of the program being debugged). The behavior of this
7983 command is identical to that of the behavior of the @code{explore}
7984 command being passed the argument @var{expr}.
7986 @item explore type @var{arg}
7987 @cindex explore type
7988 This sub-command of @code{explore} explores the type of @var{arg} (if
7989 @var{arg} is a type visible in the current context of program being
7990 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7991 is an expression valid in the current context of the program being
7992 debugged). If @var{arg} is a type, then the behavior of this command is
7993 identical to that of the @code{explore} command being passed the
7994 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7995 this command will be identical to that of the @code{explore} command
7996 being passed the type of @var{arg} as the argument.
8000 * Expressions:: Expressions
8001 * Ambiguous Expressions:: Ambiguous Expressions
8002 * Variables:: Program variables
8003 * Arrays:: Artificial arrays
8004 * Output Formats:: Output formats
8005 * Memory:: Examining memory
8006 * Auto Display:: Automatic display
8007 * Print Settings:: Print settings
8008 * Pretty Printing:: Python pretty printing
8009 * Value History:: Value history
8010 * Convenience Vars:: Convenience variables
8011 * Convenience Funs:: Convenience functions
8012 * Registers:: Registers
8013 * Floating Point Hardware:: Floating point hardware
8014 * Vector Unit:: Vector Unit
8015 * OS Information:: Auxiliary data provided by operating system
8016 * Memory Region Attributes:: Memory region attributes
8017 * Dump/Restore Files:: Copy between memory and a file
8018 * Core File Generation:: Cause a program dump its core
8019 * Character Sets:: Debugging programs that use a different
8020 character set than GDB does
8021 * Caching Remote Data:: Data caching for remote targets
8022 * Searching Memory:: Searching memory for a sequence of bytes
8026 @section Expressions
8029 @code{print} and many other @value{GDBN} commands accept an expression and
8030 compute its value. Any kind of constant, variable or operator defined
8031 by the programming language you are using is valid in an expression in
8032 @value{GDBN}. This includes conditional expressions, function calls,
8033 casts, and string constants. It also includes preprocessor macros, if
8034 you compiled your program to include this information; see
8037 @cindex arrays in expressions
8038 @value{GDBN} supports array constants in expressions input by
8039 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
8040 you can use the command @code{print @{1, 2, 3@}} to create an array
8041 of three integers. If you pass an array to a function or assign it
8042 to a program variable, @value{GDBN} copies the array to memory that
8043 is @code{malloc}ed in the target program.
8045 Because C is so widespread, most of the expressions shown in examples in
8046 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
8047 Languages}, for information on how to use expressions in other
8050 In this section, we discuss operators that you can use in @value{GDBN}
8051 expressions regardless of your programming language.
8053 @cindex casts, in expressions
8054 Casts are supported in all languages, not just in C, because it is so
8055 useful to cast a number into a pointer in order to examine a structure
8056 at that address in memory.
8057 @c FIXME: casts supported---Mod2 true?
8059 @value{GDBN} supports these operators, in addition to those common
8060 to programming languages:
8064 @samp{@@} is a binary operator for treating parts of memory as arrays.
8065 @xref{Arrays, ,Artificial Arrays}, for more information.
8068 @samp{::} allows you to specify a variable in terms of the file or
8069 function where it is defined. @xref{Variables, ,Program Variables}.
8071 @cindex @{@var{type}@}
8072 @cindex type casting memory
8073 @cindex memory, viewing as typed object
8074 @cindex casts, to view memory
8075 @item @{@var{type}@} @var{addr}
8076 Refers to an object of type @var{type} stored at address @var{addr} in
8077 memory. @var{addr} may be any expression whose value is an integer or
8078 pointer (but parentheses are required around binary operators, just as in
8079 a cast). This construct is allowed regardless of what kind of data is
8080 normally supposed to reside at @var{addr}.
8083 @node Ambiguous Expressions
8084 @section Ambiguous Expressions
8085 @cindex ambiguous expressions
8087 Expressions can sometimes contain some ambiguous elements. For instance,
8088 some programming languages (notably Ada, C@t{++} and Objective-C) permit
8089 a single function name to be defined several times, for application in
8090 different contexts. This is called @dfn{overloading}. Another example
8091 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
8092 templates and is typically instantiated several times, resulting in
8093 the same function name being defined in different contexts.
8095 In some cases and depending on the language, it is possible to adjust
8096 the expression to remove the ambiguity. For instance in C@t{++}, you
8097 can specify the signature of the function you want to break on, as in
8098 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
8099 qualified name of your function often makes the expression unambiguous
8102 When an ambiguity that needs to be resolved is detected, the debugger
8103 has the capability to display a menu of numbered choices for each
8104 possibility, and then waits for the selection with the prompt @samp{>}.
8105 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
8106 aborts the current command. If the command in which the expression was
8107 used allows more than one choice to be selected, the next option in the
8108 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
8111 For example, the following session excerpt shows an attempt to set a
8112 breakpoint at the overloaded symbol @code{String::after}.
8113 We choose three particular definitions of that function name:
8115 @c FIXME! This is likely to change to show arg type lists, at least
8118 (@value{GDBP}) b String::after
8121 [2] file:String.cc; line number:867
8122 [3] file:String.cc; line number:860
8123 [4] file:String.cc; line number:875
8124 [5] file:String.cc; line number:853
8125 [6] file:String.cc; line number:846
8126 [7] file:String.cc; line number:735
8128 Breakpoint 1 at 0xb26c: file String.cc, line 867.
8129 Breakpoint 2 at 0xb344: file String.cc, line 875.
8130 Breakpoint 3 at 0xafcc: file String.cc, line 846.
8131 Multiple breakpoints were set.
8132 Use the "delete" command to delete unwanted
8139 @kindex set multiple-symbols
8140 @item set multiple-symbols @var{mode}
8141 @cindex multiple-symbols menu
8143 This option allows you to adjust the debugger behavior when an expression
8146 By default, @var{mode} is set to @code{all}. If the command with which
8147 the expression is used allows more than one choice, then @value{GDBN}
8148 automatically selects all possible choices. For instance, inserting
8149 a breakpoint on a function using an ambiguous name results in a breakpoint
8150 inserted on each possible match. However, if a unique choice must be made,
8151 then @value{GDBN} uses the menu to help you disambiguate the expression.
8152 For instance, printing the address of an overloaded function will result
8153 in the use of the menu.
8155 When @var{mode} is set to @code{ask}, the debugger always uses the menu
8156 when an ambiguity is detected.
8158 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
8159 an error due to the ambiguity and the command is aborted.
8161 @kindex show multiple-symbols
8162 @item show multiple-symbols
8163 Show the current value of the @code{multiple-symbols} setting.
8167 @section Program Variables
8169 The most common kind of expression to use is the name of a variable
8172 Variables in expressions are understood in the selected stack frame
8173 (@pxref{Selection, ,Selecting a Frame}); they must be either:
8177 global (or file-static)
8184 visible according to the scope rules of the
8185 programming language from the point of execution in that frame
8188 @noindent This means that in the function
8203 you can examine and use the variable @code{a} whenever your program is
8204 executing within the function @code{foo}, but you can only use or
8205 examine the variable @code{b} while your program is executing inside
8206 the block where @code{b} is declared.
8208 @cindex variable name conflict
8209 There is an exception: you can refer to a variable or function whose
8210 scope is a single source file even if the current execution point is not
8211 in this file. But it is possible to have more than one such variable or
8212 function with the same name (in different source files). If that
8213 happens, referring to that name has unpredictable effects. If you wish,
8214 you can specify a static variable in a particular function or file by
8215 using the colon-colon (@code{::}) notation:
8217 @cindex colon-colon, context for variables/functions
8219 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
8220 @cindex @code{::}, context for variables/functions
8223 @var{file}::@var{variable}
8224 @var{function}::@var{variable}
8228 Here @var{file} or @var{function} is the name of the context for the
8229 static @var{variable}. In the case of file names, you can use quotes to
8230 make sure @value{GDBN} parses the file name as a single word---for example,
8231 to print a global value of @code{x} defined in @file{f2.c}:
8234 (@value{GDBP}) p 'f2.c'::x
8237 The @code{::} notation is normally used for referring to
8238 static variables, since you typically disambiguate uses of local variables
8239 in functions by selecting the appropriate frame and using the
8240 simple name of the variable. However, you may also use this notation
8241 to refer to local variables in frames enclosing the selected frame:
8250 process (a); /* Stop here */
8261 For example, if there is a breakpoint at the commented line,
8262 here is what you might see
8263 when the program stops after executing the call @code{bar(0)}:
8268 (@value{GDBP}) p bar::a
8271 #2 0x080483d0 in foo (a=5) at foobar.c:12
8274 (@value{GDBP}) p bar::a
8278 @cindex C@t{++} scope resolution
8279 These uses of @samp{::} are very rarely in conflict with the very similar
8280 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8281 scope resolution operator in @value{GDBN} expressions.
8282 @c FIXME: Um, so what happens in one of those rare cases where it's in
8285 @cindex wrong values
8286 @cindex variable values, wrong
8287 @cindex function entry/exit, wrong values of variables
8288 @cindex optimized code, wrong values of variables
8290 @emph{Warning:} Occasionally, a local variable may appear to have the
8291 wrong value at certain points in a function---just after entry to a new
8292 scope, and just before exit.
8294 You may see this problem when you are stepping by machine instructions.
8295 This is because, on most machines, it takes more than one instruction to
8296 set up a stack frame (including local variable definitions); if you are
8297 stepping by machine instructions, variables may appear to have the wrong
8298 values until the stack frame is completely built. On exit, it usually
8299 also takes more than one machine instruction to destroy a stack frame;
8300 after you begin stepping through that group of instructions, local
8301 variable definitions may be gone.
8303 This may also happen when the compiler does significant optimizations.
8304 To be sure of always seeing accurate values, turn off all optimization
8307 @cindex ``No symbol "foo" in current context''
8308 Another possible effect of compiler optimizations is to optimize
8309 unused variables out of existence, or assign variables to registers (as
8310 opposed to memory addresses). Depending on the support for such cases
8311 offered by the debug info format used by the compiler, @value{GDBN}
8312 might not be able to display values for such local variables. If that
8313 happens, @value{GDBN} will print a message like this:
8316 No symbol "foo" in current context.
8319 To solve such problems, either recompile without optimizations, or use a
8320 different debug info format, if the compiler supports several such
8321 formats. @xref{Compilation}, for more information on choosing compiler
8322 options. @xref{C, ,C and C@t{++}}, for more information about debug
8323 info formats that are best suited to C@t{++} programs.
8325 If you ask to print an object whose contents are unknown to
8326 @value{GDBN}, e.g., because its data type is not completely specified
8327 by the debug information, @value{GDBN} will say @samp{<incomplete
8328 type>}. @xref{Symbols, incomplete type}, for more about this.
8330 If you append @kbd{@@entry} string to a function parameter name you get its
8331 value at the time the function got called. If the value is not available an
8332 error message is printed. Entry values are available only with some compilers.
8333 Entry values are normally also printed at the function parameter list according
8334 to @ref{set print entry-values}.
8337 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8343 (gdb) print i@@entry
8347 Strings are identified as arrays of @code{char} values without specified
8348 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8349 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8350 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8351 defines literal string type @code{"char"} as @code{char} without a sign.
8356 signed char var1[] = "A";
8359 You get during debugging
8364 $2 = @{65 'A', 0 '\0'@}
8368 @section Artificial Arrays
8370 @cindex artificial array
8372 @kindex @@@r{, referencing memory as an array}
8373 It is often useful to print out several successive objects of the
8374 same type in memory; a section of an array, or an array of
8375 dynamically determined size for which only a pointer exists in the
8378 You can do this by referring to a contiguous span of memory as an
8379 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8380 operand of @samp{@@} should be the first element of the desired array
8381 and be an individual object. The right operand should be the desired length
8382 of the array. The result is an array value whose elements are all of
8383 the type of the left argument. The first element is actually the left
8384 argument; the second element comes from bytes of memory immediately
8385 following those that hold the first element, and so on. Here is an
8386 example. If a program says
8389 int *array = (int *) malloc (len * sizeof (int));
8393 you can print the contents of @code{array} with
8399 The left operand of @samp{@@} must reside in memory. Array values made
8400 with @samp{@@} in this way behave just like other arrays in terms of
8401 subscripting, and are coerced to pointers when used in expressions.
8402 Artificial arrays most often appear in expressions via the value history
8403 (@pxref{Value History, ,Value History}), after printing one out.
8405 Another way to create an artificial array is to use a cast.
8406 This re-interprets a value as if it were an array.
8407 The value need not be in memory:
8409 (@value{GDBP}) p/x (short[2])0x12345678
8410 $1 = @{0x1234, 0x5678@}
8413 As a convenience, if you leave the array length out (as in
8414 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8415 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8417 (@value{GDBP}) p/x (short[])0x12345678
8418 $2 = @{0x1234, 0x5678@}
8421 Sometimes the artificial array mechanism is not quite enough; in
8422 moderately complex data structures, the elements of interest may not
8423 actually be adjacent---for example, if you are interested in the values
8424 of pointers in an array. One useful work-around in this situation is
8425 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8426 Variables}) as a counter in an expression that prints the first
8427 interesting value, and then repeat that expression via @key{RET}. For
8428 instance, suppose you have an array @code{dtab} of pointers to
8429 structures, and you are interested in the values of a field @code{fv}
8430 in each structure. Here is an example of what you might type:
8440 @node Output Formats
8441 @section Output Formats
8443 @cindex formatted output
8444 @cindex output formats
8445 By default, @value{GDBN} prints a value according to its data type. Sometimes
8446 this is not what you want. For example, you might want to print a number
8447 in hex, or a pointer in decimal. Or you might want to view data in memory
8448 at a certain address as a character string or as an instruction. To do
8449 these things, specify an @dfn{output format} when you print a value.
8451 The simplest use of output formats is to say how to print a value
8452 already computed. This is done by starting the arguments of the
8453 @code{print} command with a slash and a format letter. The format
8454 letters supported are:
8458 Regard the bits of the value as an integer, and print the integer in
8462 Print as integer in signed decimal.
8465 Print as integer in unsigned decimal.
8468 Print as integer in octal.
8471 Print as integer in binary. The letter @samp{t} stands for ``two''.
8472 @footnote{@samp{b} cannot be used because these format letters are also
8473 used with the @code{x} command, where @samp{b} stands for ``byte'';
8474 see @ref{Memory,,Examining Memory}.}
8477 @cindex unknown address, locating
8478 @cindex locate address
8479 Print as an address, both absolute in hexadecimal and as an offset from
8480 the nearest preceding symbol. You can use this format used to discover
8481 where (in what function) an unknown address is located:
8484 (@value{GDBP}) p/a 0x54320
8485 $3 = 0x54320 <_initialize_vx+396>
8489 The command @code{info symbol 0x54320} yields similar results.
8490 @xref{Symbols, info symbol}.
8493 Regard as an integer and print it as a character constant. This
8494 prints both the numerical value and its character representation. The
8495 character representation is replaced with the octal escape @samp{\nnn}
8496 for characters outside the 7-bit @sc{ascii} range.
8498 Without this format, @value{GDBN} displays @code{char},
8499 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8500 constants. Single-byte members of vectors are displayed as integer
8504 Regard the bits of the value as a floating point number and print
8505 using typical floating point syntax.
8508 @cindex printing strings
8509 @cindex printing byte arrays
8510 Regard as a string, if possible. With this format, pointers to single-byte
8511 data are displayed as null-terminated strings and arrays of single-byte data
8512 are displayed as fixed-length strings. Other values are displayed in their
8515 Without this format, @value{GDBN} displays pointers to and arrays of
8516 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8517 strings. Single-byte members of a vector are displayed as an integer
8521 Like @samp{x} formatting, the value is treated as an integer and
8522 printed as hexadecimal, but leading zeros are printed to pad the value
8523 to the size of the integer type.
8526 @cindex raw printing
8527 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8528 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8529 Printing}). This typically results in a higher-level display of the
8530 value's contents. The @samp{r} format bypasses any Python
8531 pretty-printer which might exist.
8534 For example, to print the program counter in hex (@pxref{Registers}), type
8541 Note that no space is required before the slash; this is because command
8542 names in @value{GDBN} cannot contain a slash.
8544 To reprint the last value in the value history with a different format,
8545 you can use the @code{print} command with just a format and no
8546 expression. For example, @samp{p/x} reprints the last value in hex.
8549 @section Examining Memory
8551 You can use the command @code{x} (for ``examine'') to examine memory in
8552 any of several formats, independently of your program's data types.
8554 @cindex examining memory
8556 @kindex x @r{(examine memory)}
8557 @item x/@var{nfu} @var{addr}
8560 Use the @code{x} command to examine memory.
8563 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8564 much memory to display and how to format it; @var{addr} is an
8565 expression giving the address where you want to start displaying memory.
8566 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8567 Several commands set convenient defaults for @var{addr}.
8570 @item @var{n}, the repeat count
8571 The repeat count is a decimal integer; the default is 1. It specifies
8572 how much memory (counting by units @var{u}) to display.
8573 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8576 @item @var{f}, the display format
8577 The display format is one of the formats used by @code{print}
8578 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8579 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8580 The default is @samp{x} (hexadecimal) initially. The default changes
8581 each time you use either @code{x} or @code{print}.
8583 @item @var{u}, the unit size
8584 The unit size is any of
8590 Halfwords (two bytes).
8592 Words (four bytes). This is the initial default.
8594 Giant words (eight bytes).
8597 Each time you specify a unit size with @code{x}, that size becomes the
8598 default unit the next time you use @code{x}. For the @samp{i} format,
8599 the unit size is ignored and is normally not written. For the @samp{s} format,
8600 the unit size defaults to @samp{b}, unless it is explicitly given.
8601 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8602 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8603 Note that the results depend on the programming language of the
8604 current compilation unit. If the language is C, the @samp{s}
8605 modifier will use the UTF-16 encoding while @samp{w} will use
8606 UTF-32. The encoding is set by the programming language and cannot
8609 @item @var{addr}, starting display address
8610 @var{addr} is the address where you want @value{GDBN} to begin displaying
8611 memory. The expression need not have a pointer value (though it may);
8612 it is always interpreted as an integer address of a byte of memory.
8613 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8614 @var{addr} is usually just after the last address examined---but several
8615 other commands also set the default address: @code{info breakpoints} (to
8616 the address of the last breakpoint listed), @code{info line} (to the
8617 starting address of a line), and @code{print} (if you use it to display
8618 a value from memory).
8621 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8622 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8623 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8624 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8625 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8627 Since the letters indicating unit sizes are all distinct from the
8628 letters specifying output formats, you do not have to remember whether
8629 unit size or format comes first; either order works. The output
8630 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8631 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8633 Even though the unit size @var{u} is ignored for the formats @samp{s}
8634 and @samp{i}, you might still want to use a count @var{n}; for example,
8635 @samp{3i} specifies that you want to see three machine instructions,
8636 including any operands. For convenience, especially when used with
8637 the @code{display} command, the @samp{i} format also prints branch delay
8638 slot instructions, if any, beyond the count specified, which immediately
8639 follow the last instruction that is within the count. The command
8640 @code{disassemble} gives an alternative way of inspecting machine
8641 instructions; see @ref{Machine Code,,Source and Machine Code}.
8643 All the defaults for the arguments to @code{x} are designed to make it
8644 easy to continue scanning memory with minimal specifications each time
8645 you use @code{x}. For example, after you have inspected three machine
8646 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8647 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8648 the repeat count @var{n} is used again; the other arguments default as
8649 for successive uses of @code{x}.
8651 When examining machine instructions, the instruction at current program
8652 counter is shown with a @code{=>} marker. For example:
8655 (@value{GDBP}) x/5i $pc-6
8656 0x804837f <main+11>: mov %esp,%ebp
8657 0x8048381 <main+13>: push %ecx
8658 0x8048382 <main+14>: sub $0x4,%esp
8659 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8660 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8663 @cindex @code{$_}, @code{$__}, and value history
8664 The addresses and contents printed by the @code{x} command are not saved
8665 in the value history because there is often too much of them and they
8666 would get in the way. Instead, @value{GDBN} makes these values available for
8667 subsequent use in expressions as values of the convenience variables
8668 @code{$_} and @code{$__}. After an @code{x} command, the last address
8669 examined is available for use in expressions in the convenience variable
8670 @code{$_}. The contents of that address, as examined, are available in
8671 the convenience variable @code{$__}.
8673 If the @code{x} command has a repeat count, the address and contents saved
8674 are from the last memory unit printed; this is not the same as the last
8675 address printed if several units were printed on the last line of output.
8677 @cindex remote memory comparison
8678 @cindex verify remote memory image
8679 When you are debugging a program running on a remote target machine
8680 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8681 remote machine's memory against the executable file you downloaded to
8682 the target. The @code{compare-sections} command is provided for such
8686 @kindex compare-sections
8687 @item compare-sections @r{[}@var{section-name}@r{]}
8688 Compare the data of a loadable section @var{section-name} in the
8689 executable file of the program being debugged with the same section in
8690 the remote machine's memory, and report any mismatches. With no
8691 arguments, compares all loadable sections. This command's
8692 availability depends on the target's support for the @code{"qCRC"}
8697 @section Automatic Display
8698 @cindex automatic display
8699 @cindex display of expressions
8701 If you find that you want to print the value of an expression frequently
8702 (to see how it changes), you might want to add it to the @dfn{automatic
8703 display list} so that @value{GDBN} prints its value each time your program stops.
8704 Each expression added to the list is given a number to identify it;
8705 to remove an expression from the list, you specify that number.
8706 The automatic display looks like this:
8710 3: bar[5] = (struct hack *) 0x3804
8714 This display shows item numbers, expressions and their current values. As with
8715 displays you request manually using @code{x} or @code{print}, you can
8716 specify the output format you prefer; in fact, @code{display} decides
8717 whether to use @code{print} or @code{x} depending your format
8718 specification---it uses @code{x} if you specify either the @samp{i}
8719 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8723 @item display @var{expr}
8724 Add the expression @var{expr} to the list of expressions to display
8725 each time your program stops. @xref{Expressions, ,Expressions}.
8727 @code{display} does not repeat if you press @key{RET} again after using it.
8729 @item display/@var{fmt} @var{expr}
8730 For @var{fmt} specifying only a display format and not a size or
8731 count, add the expression @var{expr} to the auto-display list but
8732 arrange to display it each time in the specified format @var{fmt}.
8733 @xref{Output Formats,,Output Formats}.
8735 @item display/@var{fmt} @var{addr}
8736 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8737 number of units, add the expression @var{addr} as a memory address to
8738 be examined each time your program stops. Examining means in effect
8739 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8742 For example, @samp{display/i $pc} can be helpful, to see the machine
8743 instruction about to be executed each time execution stops (@samp{$pc}
8744 is a common name for the program counter; @pxref{Registers, ,Registers}).
8747 @kindex delete display
8749 @item undisplay @var{dnums}@dots{}
8750 @itemx delete display @var{dnums}@dots{}
8751 Remove items from the list of expressions to display. Specify the
8752 numbers of the displays that you want affected with the command
8753 argument @var{dnums}. It can be a single display number, one of the
8754 numbers shown in the first field of the @samp{info display} display;
8755 or it could be a range of display numbers, as in @code{2-4}.
8757 @code{undisplay} does not repeat if you press @key{RET} after using it.
8758 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8760 @kindex disable display
8761 @item disable display @var{dnums}@dots{}
8762 Disable the display of item numbers @var{dnums}. A disabled display
8763 item is not printed automatically, but is not forgotten. It may be
8764 enabled again later. Specify the numbers of the displays that you
8765 want affected with the command argument @var{dnums}. It can be a
8766 single display number, one of the numbers shown in the first field of
8767 the @samp{info display} display; or it could be a range of display
8768 numbers, as in @code{2-4}.
8770 @kindex enable display
8771 @item enable display @var{dnums}@dots{}
8772 Enable display of item numbers @var{dnums}. It becomes effective once
8773 again in auto display of its expression, until you specify otherwise.
8774 Specify the numbers of the displays that you want affected with the
8775 command argument @var{dnums}. It can be a single display number, one
8776 of the numbers shown in the first field of the @samp{info display}
8777 display; or it could be a range of display numbers, as in @code{2-4}.
8780 Display the current values of the expressions on the list, just as is
8781 done when your program stops.
8783 @kindex info display
8785 Print the list of expressions previously set up to display
8786 automatically, each one with its item number, but without showing the
8787 values. This includes disabled expressions, which are marked as such.
8788 It also includes expressions which would not be displayed right now
8789 because they refer to automatic variables not currently available.
8792 @cindex display disabled out of scope
8793 If a display expression refers to local variables, then it does not make
8794 sense outside the lexical context for which it was set up. Such an
8795 expression is disabled when execution enters a context where one of its
8796 variables is not defined. For example, if you give the command
8797 @code{display last_char} while inside a function with an argument
8798 @code{last_char}, @value{GDBN} displays this argument while your program
8799 continues to stop inside that function. When it stops elsewhere---where
8800 there is no variable @code{last_char}---the display is disabled
8801 automatically. The next time your program stops where @code{last_char}
8802 is meaningful, you can enable the display expression once again.
8804 @node Print Settings
8805 @section Print Settings
8807 @cindex format options
8808 @cindex print settings
8809 @value{GDBN} provides the following ways to control how arrays, structures,
8810 and symbols are printed.
8813 These settings are useful for debugging programs in any language:
8817 @item set print address
8818 @itemx set print address on
8819 @cindex print/don't print memory addresses
8820 @value{GDBN} prints memory addresses showing the location of stack
8821 traces, structure values, pointer values, breakpoints, and so forth,
8822 even when it also displays the contents of those addresses. The default
8823 is @code{on}. For example, this is what a stack frame display looks like with
8824 @code{set print address on}:
8829 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8831 530 if (lquote != def_lquote)
8835 @item set print address off
8836 Do not print addresses when displaying their contents. For example,
8837 this is the same stack frame displayed with @code{set print address off}:
8841 (@value{GDBP}) set print addr off
8843 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8844 530 if (lquote != def_lquote)
8848 You can use @samp{set print address off} to eliminate all machine
8849 dependent displays from the @value{GDBN} interface. For example, with
8850 @code{print address off}, you should get the same text for backtraces on
8851 all machines---whether or not they involve pointer arguments.
8854 @item show print address
8855 Show whether or not addresses are to be printed.
8858 When @value{GDBN} prints a symbolic address, it normally prints the
8859 closest earlier symbol plus an offset. If that symbol does not uniquely
8860 identify the address (for example, it is a name whose scope is a single
8861 source file), you may need to clarify. One way to do this is with
8862 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8863 you can set @value{GDBN} to print the source file and line number when
8864 it prints a symbolic address:
8867 @item set print symbol-filename on
8868 @cindex source file and line of a symbol
8869 @cindex symbol, source file and line
8870 Tell @value{GDBN} to print the source file name and line number of a
8871 symbol in the symbolic form of an address.
8873 @item set print symbol-filename off
8874 Do not print source file name and line number of a symbol. This is the
8877 @item show print symbol-filename
8878 Show whether or not @value{GDBN} will print the source file name and
8879 line number of a symbol in the symbolic form of an address.
8882 Another situation where it is helpful to show symbol filenames and line
8883 numbers is when disassembling code; @value{GDBN} shows you the line
8884 number and source file that corresponds to each instruction.
8886 Also, you may wish to see the symbolic form only if the address being
8887 printed is reasonably close to the closest earlier symbol:
8890 @item set print max-symbolic-offset @var{max-offset}
8891 @itemx set print max-symbolic-offset unlimited
8892 @cindex maximum value for offset of closest symbol
8893 Tell @value{GDBN} to only display the symbolic form of an address if the
8894 offset between the closest earlier symbol and the address is less than
8895 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8896 to always print the symbolic form of an address if any symbol precedes
8897 it. Zero is equivalent to @code{unlimited}.
8899 @item show print max-symbolic-offset
8900 Ask how large the maximum offset is that @value{GDBN} prints in a
8904 @cindex wild pointer, interpreting
8905 @cindex pointer, finding referent
8906 If you have a pointer and you are not sure where it points, try
8907 @samp{set print symbol-filename on}. Then you can determine the name
8908 and source file location of the variable where it points, using
8909 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8910 For example, here @value{GDBN} shows that a variable @code{ptt} points
8911 at another variable @code{t}, defined in @file{hi2.c}:
8914 (@value{GDBP}) set print symbol-filename on
8915 (@value{GDBP}) p/a ptt
8916 $4 = 0xe008 <t in hi2.c>
8920 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8921 does not show the symbol name and filename of the referent, even with
8922 the appropriate @code{set print} options turned on.
8925 You can also enable @samp{/a}-like formatting all the time using
8926 @samp{set print symbol on}:
8929 @item set print symbol on
8930 Tell @value{GDBN} to print the symbol corresponding to an address, if
8933 @item set print symbol off
8934 Tell @value{GDBN} not to print the symbol corresponding to an
8935 address. In this mode, @value{GDBN} will still print the symbol
8936 corresponding to pointers to functions. This is the default.
8938 @item show print symbol
8939 Show whether @value{GDBN} will display the symbol corresponding to an
8943 Other settings control how different kinds of objects are printed:
8946 @item set print array
8947 @itemx set print array on
8948 @cindex pretty print arrays
8949 Pretty print arrays. This format is more convenient to read,
8950 but uses more space. The default is off.
8952 @item set print array off
8953 Return to compressed format for arrays.
8955 @item show print array
8956 Show whether compressed or pretty format is selected for displaying
8959 @cindex print array indexes
8960 @item set print array-indexes
8961 @itemx set print array-indexes on
8962 Print the index of each element when displaying arrays. May be more
8963 convenient to locate a given element in the array or quickly find the
8964 index of a given element in that printed array. The default is off.
8966 @item set print array-indexes off
8967 Stop printing element indexes when displaying arrays.
8969 @item show print array-indexes
8970 Show whether the index of each element is printed when displaying
8973 @item set print elements @var{number-of-elements}
8974 @itemx set print elements unlimited
8975 @cindex number of array elements to print
8976 @cindex limit on number of printed array elements
8977 Set a limit on how many elements of an array @value{GDBN} will print.
8978 If @value{GDBN} is printing a large array, it stops printing after it has
8979 printed the number of elements set by the @code{set print elements} command.
8980 This limit also applies to the display of strings.
8981 When @value{GDBN} starts, this limit is set to 200.
8982 Setting @var{number-of-elements} to @code{unlimited} or zero means
8983 that the number of elements to print is unlimited.
8985 @item show print elements
8986 Display the number of elements of a large array that @value{GDBN} will print.
8987 If the number is 0, then the printing is unlimited.
8989 @item set print frame-arguments @var{value}
8990 @kindex set print frame-arguments
8991 @cindex printing frame argument values
8992 @cindex print all frame argument values
8993 @cindex print frame argument values for scalars only
8994 @cindex do not print frame argument values
8995 This command allows to control how the values of arguments are printed
8996 when the debugger prints a frame (@pxref{Frames}). The possible
9001 The values of all arguments are printed.
9004 Print the value of an argument only if it is a scalar. The value of more
9005 complex arguments such as arrays, structures, unions, etc, is replaced
9006 by @code{@dots{}}. This is the default. Here is an example where
9007 only scalar arguments are shown:
9010 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9015 None of the argument values are printed. Instead, the value of each argument
9016 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9019 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9024 By default, only scalar arguments are printed. This command can be used
9025 to configure the debugger to print the value of all arguments, regardless
9026 of their type. However, it is often advantageous to not print the value
9027 of more complex parameters. For instance, it reduces the amount of
9028 information printed in each frame, making the backtrace more readable.
9029 Also, it improves performance when displaying Ada frames, because
9030 the computation of large arguments can sometimes be CPU-intensive,
9031 especially in large applications. Setting @code{print frame-arguments}
9032 to @code{scalars} (the default) or @code{none} avoids this computation,
9033 thus speeding up the display of each Ada frame.
9035 @item show print frame-arguments
9036 Show how the value of arguments should be displayed when printing a frame.
9038 @item set print raw frame-arguments on
9039 Print frame arguments in raw, non pretty-printed, form.
9041 @item set print raw frame-arguments off
9042 Print frame arguments in pretty-printed form, if there is a pretty-printer
9043 for the value (@pxref{Pretty Printing}),
9044 otherwise print the value in raw form.
9045 This is the default.
9047 @item show print raw frame-arguments
9048 Show whether to print frame arguments in raw form.
9050 @anchor{set print entry-values}
9051 @item set print entry-values @var{value}
9052 @kindex set print entry-values
9053 Set printing of frame argument values at function entry. In some cases
9054 @value{GDBN} can determine the value of function argument which was passed by
9055 the function caller, even if the value was modified inside the called function
9056 and therefore is different. With optimized code, the current value could be
9057 unavailable, but the entry value may still be known.
9059 The default value is @code{default} (see below for its description). Older
9060 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9061 this feature will behave in the @code{default} setting the same way as with the
9064 This functionality is currently supported only by DWARF 2 debugging format and
9065 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9066 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9069 The @var{value} parameter can be one of the following:
9073 Print only actual parameter values, never print values from function entry
9077 #0 different (val=6)
9078 #0 lost (val=<optimized out>)
9080 #0 invalid (val=<optimized out>)
9084 Print only parameter values from function entry point. The actual parameter
9085 values are never printed.
9087 #0 equal (val@@entry=5)
9088 #0 different (val@@entry=5)
9089 #0 lost (val@@entry=5)
9090 #0 born (val@@entry=<optimized out>)
9091 #0 invalid (val@@entry=<optimized out>)
9095 Print only parameter values from function entry point. If value from function
9096 entry point is not known while the actual value is known, print the actual
9097 value for such parameter.
9099 #0 equal (val@@entry=5)
9100 #0 different (val@@entry=5)
9101 #0 lost (val@@entry=5)
9103 #0 invalid (val@@entry=<optimized out>)
9107 Print actual parameter values. If actual parameter value is not known while
9108 value from function entry point is known, print the entry point value for such
9112 #0 different (val=6)
9113 #0 lost (val@@entry=5)
9115 #0 invalid (val=<optimized out>)
9119 Always print both the actual parameter value and its value from function entry
9120 point, even if values of one or both are not available due to compiler
9123 #0 equal (val=5, val@@entry=5)
9124 #0 different (val=6, val@@entry=5)
9125 #0 lost (val=<optimized out>, val@@entry=5)
9126 #0 born (val=10, val@@entry=<optimized out>)
9127 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9131 Print the actual parameter value if it is known and also its value from
9132 function entry point if it is known. If neither is known, print for the actual
9133 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9134 values are known and identical, print the shortened
9135 @code{param=param@@entry=VALUE} notation.
9137 #0 equal (val=val@@entry=5)
9138 #0 different (val=6, val@@entry=5)
9139 #0 lost (val@@entry=5)
9141 #0 invalid (val=<optimized out>)
9145 Always print the actual parameter value. Print also its value from function
9146 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9147 if both values are known and identical, print the shortened
9148 @code{param=param@@entry=VALUE} notation.
9150 #0 equal (val=val@@entry=5)
9151 #0 different (val=6, val@@entry=5)
9152 #0 lost (val=<optimized out>, val@@entry=5)
9154 #0 invalid (val=<optimized out>)
9158 For analysis messages on possible failures of frame argument values at function
9159 entry resolution see @ref{set debug entry-values}.
9161 @item show print entry-values
9162 Show the method being used for printing of frame argument values at function
9165 @item set print repeats @var{number-of-repeats}
9166 @itemx set print repeats unlimited
9167 @cindex repeated array elements
9168 Set the threshold for suppressing display of repeated array
9169 elements. When the number of consecutive identical elements of an
9170 array exceeds the threshold, @value{GDBN} prints the string
9171 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9172 identical repetitions, instead of displaying the identical elements
9173 themselves. Setting the threshold to @code{unlimited} or zero will
9174 cause all elements to be individually printed. The default threshold
9177 @item show print repeats
9178 Display the current threshold for printing repeated identical
9181 @item set print null-stop
9182 @cindex @sc{null} elements in arrays
9183 Cause @value{GDBN} to stop printing the characters of an array when the first
9184 @sc{null} is encountered. This is useful when large arrays actually
9185 contain only short strings.
9188 @item show print null-stop
9189 Show whether @value{GDBN} stops printing an array on the first
9190 @sc{null} character.
9192 @item set print pretty on
9193 @cindex print structures in indented form
9194 @cindex indentation in structure display
9195 Cause @value{GDBN} to print structures in an indented format with one member
9196 per line, like this:
9211 @item set print pretty off
9212 Cause @value{GDBN} to print structures in a compact format, like this:
9216 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9217 meat = 0x54 "Pork"@}
9222 This is the default format.
9224 @item show print pretty
9225 Show which format @value{GDBN} is using to print structures.
9227 @item set print sevenbit-strings on
9228 @cindex eight-bit characters in strings
9229 @cindex octal escapes in strings
9230 Print using only seven-bit characters; if this option is set,
9231 @value{GDBN} displays any eight-bit characters (in strings or
9232 character values) using the notation @code{\}@var{nnn}. This setting is
9233 best if you are working in English (@sc{ascii}) and you use the
9234 high-order bit of characters as a marker or ``meta'' bit.
9236 @item set print sevenbit-strings off
9237 Print full eight-bit characters. This allows the use of more
9238 international character sets, and is the default.
9240 @item show print sevenbit-strings
9241 Show whether or not @value{GDBN} is printing only seven-bit characters.
9243 @item set print union on
9244 @cindex unions in structures, printing
9245 Tell @value{GDBN} to print unions which are contained in structures
9246 and other unions. This is the default setting.
9248 @item set print union off
9249 Tell @value{GDBN} not to print unions which are contained in
9250 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9253 @item show print union
9254 Ask @value{GDBN} whether or not it will print unions which are contained in
9255 structures and other unions.
9257 For example, given the declarations
9260 typedef enum @{Tree, Bug@} Species;
9261 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9262 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9273 struct thing foo = @{Tree, @{Acorn@}@};
9277 with @code{set print union on} in effect @samp{p foo} would print
9280 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9284 and with @code{set print union off} in effect it would print
9287 $1 = @{it = Tree, form = @{...@}@}
9291 @code{set print union} affects programs written in C-like languages
9297 These settings are of interest when debugging C@t{++} programs:
9300 @cindex demangling C@t{++} names
9301 @item set print demangle
9302 @itemx set print demangle on
9303 Print C@t{++} names in their source form rather than in the encoded
9304 (``mangled'') form passed to the assembler and linker for type-safe
9305 linkage. The default is on.
9307 @item show print demangle
9308 Show whether C@t{++} names are printed in mangled or demangled form.
9310 @item set print asm-demangle
9311 @itemx set print asm-demangle on
9312 Print C@t{++} names in their source form rather than their mangled form, even
9313 in assembler code printouts such as instruction disassemblies.
9316 @item show print asm-demangle
9317 Show whether C@t{++} names in assembly listings are printed in mangled
9320 @cindex C@t{++} symbol decoding style
9321 @cindex symbol decoding style, C@t{++}
9322 @kindex set demangle-style
9323 @item set demangle-style @var{style}
9324 Choose among several encoding schemes used by different compilers to
9325 represent C@t{++} names. The choices for @var{style} are currently:
9329 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9330 This is the default.
9333 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9336 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9339 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9342 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9343 @strong{Warning:} this setting alone is not sufficient to allow
9344 debugging @code{cfront}-generated executables. @value{GDBN} would
9345 require further enhancement to permit that.
9348 If you omit @var{style}, you will see a list of possible formats.
9350 @item show demangle-style
9351 Display the encoding style currently in use for decoding C@t{++} symbols.
9353 @item set print object
9354 @itemx set print object on
9355 @cindex derived type of an object, printing
9356 @cindex display derived types
9357 When displaying a pointer to an object, identify the @emph{actual}
9358 (derived) type of the object rather than the @emph{declared} type, using
9359 the virtual function table. Note that the virtual function table is
9360 required---this feature can only work for objects that have run-time
9361 type identification; a single virtual method in the object's declared
9362 type is sufficient. Note that this setting is also taken into account when
9363 working with variable objects via MI (@pxref{GDB/MI}).
9365 @item set print object off
9366 Display only the declared type of objects, without reference to the
9367 virtual function table. This is the default setting.
9369 @item show print object
9370 Show whether actual, or declared, object types are displayed.
9372 @item set print static-members
9373 @itemx set print static-members on
9374 @cindex static members of C@t{++} objects
9375 Print static members when displaying a C@t{++} object. The default is on.
9377 @item set print static-members off
9378 Do not print static members when displaying a C@t{++} object.
9380 @item show print static-members
9381 Show whether C@t{++} static members are printed or not.
9383 @item set print pascal_static-members
9384 @itemx set print pascal_static-members on
9385 @cindex static members of Pascal objects
9386 @cindex Pascal objects, static members display
9387 Print static members when displaying a Pascal object. The default is on.
9389 @item set print pascal_static-members off
9390 Do not print static members when displaying a Pascal object.
9392 @item show print pascal_static-members
9393 Show whether Pascal static members are printed or not.
9395 @c These don't work with HP ANSI C++ yet.
9396 @item set print vtbl
9397 @itemx set print vtbl on
9398 @cindex pretty print C@t{++} virtual function tables
9399 @cindex virtual functions (C@t{++}) display
9400 @cindex VTBL display
9401 Pretty print C@t{++} virtual function tables. The default is off.
9402 (The @code{vtbl} commands do not work on programs compiled with the HP
9403 ANSI C@t{++} compiler (@code{aCC}).)
9405 @item set print vtbl off
9406 Do not pretty print C@t{++} virtual function tables.
9408 @item show print vtbl
9409 Show whether C@t{++} virtual function tables are pretty printed, or not.
9412 @node Pretty Printing
9413 @section Pretty Printing
9415 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9416 Python code. It greatly simplifies the display of complex objects. This
9417 mechanism works for both MI and the CLI.
9420 * Pretty-Printer Introduction:: Introduction to pretty-printers
9421 * Pretty-Printer Example:: An example pretty-printer
9422 * Pretty-Printer Commands:: Pretty-printer commands
9425 @node Pretty-Printer Introduction
9426 @subsection Pretty-Printer Introduction
9428 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9429 registered for the value. If there is then @value{GDBN} invokes the
9430 pretty-printer to print the value. Otherwise the value is printed normally.
9432 Pretty-printers are normally named. This makes them easy to manage.
9433 The @samp{info pretty-printer} command will list all the installed
9434 pretty-printers with their names.
9435 If a pretty-printer can handle multiple data types, then its
9436 @dfn{subprinters} are the printers for the individual data types.
9437 Each such subprinter has its own name.
9438 The format of the name is @var{printer-name};@var{subprinter-name}.
9440 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9441 Typically they are automatically loaded and registered when the corresponding
9442 debug information is loaded, thus making them available without having to
9443 do anything special.
9445 There are three places where a pretty-printer can be registered.
9449 Pretty-printers registered globally are available when debugging
9453 Pretty-printers registered with a program space are available only
9454 when debugging that program.
9455 @xref{Progspaces In Python}, for more details on program spaces in Python.
9458 Pretty-printers registered with an objfile are loaded and unloaded
9459 with the corresponding objfile (e.g., shared library).
9460 @xref{Objfiles In Python}, for more details on objfiles in Python.
9463 @xref{Selecting Pretty-Printers}, for further information on how
9464 pretty-printers are selected,
9466 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9469 @node Pretty-Printer Example
9470 @subsection Pretty-Printer Example
9472 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9475 (@value{GDBP}) print s
9477 static npos = 4294967295,
9479 <std::allocator<char>> = @{
9480 <__gnu_cxx::new_allocator<char>> = @{
9481 <No data fields>@}, <No data fields>
9483 members of std::basic_string<char, std::char_traits<char>,
9484 std::allocator<char> >::_Alloc_hider:
9485 _M_p = 0x804a014 "abcd"
9490 With a pretty-printer for @code{std::string} only the contents are printed:
9493 (@value{GDBP}) print s
9497 @node Pretty-Printer Commands
9498 @subsection Pretty-Printer Commands
9499 @cindex pretty-printer commands
9502 @kindex info pretty-printer
9503 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9504 Print the list of installed pretty-printers.
9505 This includes disabled pretty-printers, which are marked as such.
9507 @var{object-regexp} is a regular expression matching the objects
9508 whose pretty-printers to list.
9509 Objects can be @code{global}, the program space's file
9510 (@pxref{Progspaces In Python}),
9511 and the object files within that program space (@pxref{Objfiles In Python}).
9512 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9513 looks up a printer from these three objects.
9515 @var{name-regexp} is a regular expression matching the name of the printers
9518 @kindex disable pretty-printer
9519 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9520 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9521 A disabled pretty-printer is not forgotten, it may be enabled again later.
9523 @kindex enable pretty-printer
9524 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9525 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9530 Suppose we have three pretty-printers installed: one from library1.so
9531 named @code{foo} that prints objects of type @code{foo}, and
9532 another from library2.so named @code{bar} that prints two types of objects,
9533 @code{bar1} and @code{bar2}.
9536 (gdb) info pretty-printer
9543 (gdb) info pretty-printer library2
9548 (gdb) disable pretty-printer library1
9550 2 of 3 printers enabled
9551 (gdb) info pretty-printer
9558 (gdb) disable pretty-printer library2 bar:bar1
9560 1 of 3 printers enabled
9561 (gdb) info pretty-printer library2
9568 (gdb) disable pretty-printer library2 bar
9570 0 of 3 printers enabled
9571 (gdb) info pretty-printer library2
9580 Note that for @code{bar} the entire printer can be disabled,
9581 as can each individual subprinter.
9584 @section Value History
9586 @cindex value history
9587 @cindex history of values printed by @value{GDBN}
9588 Values printed by the @code{print} command are saved in the @value{GDBN}
9589 @dfn{value history}. This allows you to refer to them in other expressions.
9590 Values are kept until the symbol table is re-read or discarded
9591 (for example with the @code{file} or @code{symbol-file} commands).
9592 When the symbol table changes, the value history is discarded,
9593 since the values may contain pointers back to the types defined in the
9598 @cindex history number
9599 The values printed are given @dfn{history numbers} by which you can
9600 refer to them. These are successive integers starting with one.
9601 @code{print} shows you the history number assigned to a value by
9602 printing @samp{$@var{num} = } before the value; here @var{num} is the
9605 To refer to any previous value, use @samp{$} followed by the value's
9606 history number. The way @code{print} labels its output is designed to
9607 remind you of this. Just @code{$} refers to the most recent value in
9608 the history, and @code{$$} refers to the value before that.
9609 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9610 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9611 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9613 For example, suppose you have just printed a pointer to a structure and
9614 want to see the contents of the structure. It suffices to type
9620 If you have a chain of structures where the component @code{next} points
9621 to the next one, you can print the contents of the next one with this:
9628 You can print successive links in the chain by repeating this
9629 command---which you can do by just typing @key{RET}.
9631 Note that the history records values, not expressions. If the value of
9632 @code{x} is 4 and you type these commands:
9640 then the value recorded in the value history by the @code{print} command
9641 remains 4 even though the value of @code{x} has changed.
9646 Print the last ten values in the value history, with their item numbers.
9647 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9648 values} does not change the history.
9650 @item show values @var{n}
9651 Print ten history values centered on history item number @var{n}.
9654 Print ten history values just after the values last printed. If no more
9655 values are available, @code{show values +} produces no display.
9658 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9659 same effect as @samp{show values +}.
9661 @node Convenience Vars
9662 @section Convenience Variables
9664 @cindex convenience variables
9665 @cindex user-defined variables
9666 @value{GDBN} provides @dfn{convenience variables} that you can use within
9667 @value{GDBN} to hold on to a value and refer to it later. These variables
9668 exist entirely within @value{GDBN}; they are not part of your program, and
9669 setting a convenience variable has no direct effect on further execution
9670 of your program. That is why you can use them freely.
9672 Convenience variables are prefixed with @samp{$}. Any name preceded by
9673 @samp{$} can be used for a convenience variable, unless it is one of
9674 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9675 (Value history references, in contrast, are @emph{numbers} preceded
9676 by @samp{$}. @xref{Value History, ,Value History}.)
9678 You can save a value in a convenience variable with an assignment
9679 expression, just as you would set a variable in your program.
9683 set $foo = *object_ptr
9687 would save in @code{$foo} the value contained in the object pointed to by
9690 Using a convenience variable for the first time creates it, but its
9691 value is @code{void} until you assign a new value. You can alter the
9692 value with another assignment at any time.
9694 Convenience variables have no fixed types. You can assign a convenience
9695 variable any type of value, including structures and arrays, even if
9696 that variable already has a value of a different type. The convenience
9697 variable, when used as an expression, has the type of its current value.
9700 @kindex show convenience
9701 @cindex show all user variables and functions
9702 @item show convenience
9703 Print a list of convenience variables used so far, and their values,
9704 as well as a list of the convenience functions.
9705 Abbreviated @code{show conv}.
9707 @kindex init-if-undefined
9708 @cindex convenience variables, initializing
9709 @item init-if-undefined $@var{variable} = @var{expression}
9710 Set a convenience variable if it has not already been set. This is useful
9711 for user-defined commands that keep some state. It is similar, in concept,
9712 to using local static variables with initializers in C (except that
9713 convenience variables are global). It can also be used to allow users to
9714 override default values used in a command script.
9716 If the variable is already defined then the expression is not evaluated so
9717 any side-effects do not occur.
9720 One of the ways to use a convenience variable is as a counter to be
9721 incremented or a pointer to be advanced. For example, to print
9722 a field from successive elements of an array of structures:
9726 print bar[$i++]->contents
9730 Repeat that command by typing @key{RET}.
9732 Some convenience variables are created automatically by @value{GDBN} and given
9733 values likely to be useful.
9736 @vindex $_@r{, convenience variable}
9738 The variable @code{$_} is automatically set by the @code{x} command to
9739 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9740 commands which provide a default address for @code{x} to examine also
9741 set @code{$_} to that address; these commands include @code{info line}
9742 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9743 except when set by the @code{x} command, in which case it is a pointer
9744 to the type of @code{$__}.
9746 @vindex $__@r{, convenience variable}
9748 The variable @code{$__} is automatically set by the @code{x} command
9749 to the value found in the last address examined. Its type is chosen
9750 to match the format in which the data was printed.
9753 @vindex $_exitcode@r{, convenience variable}
9754 The variable @code{$_exitcode} is automatically set to the exit code when
9755 the program being debugged terminates.
9758 The variable @code{$_exception} is set to the exception object being
9759 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9762 @itemx $_probe_arg0@dots{}$_probe_arg11
9763 Arguments to a static probe. @xref{Static Probe Points}.
9766 @vindex $_sdata@r{, inspect, convenience variable}
9767 The variable @code{$_sdata} contains extra collected static tracepoint
9768 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9769 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9770 if extra static tracepoint data has not been collected.
9773 @vindex $_siginfo@r{, convenience variable}
9774 The variable @code{$_siginfo} contains extra signal information
9775 (@pxref{extra signal information}). Note that @code{$_siginfo}
9776 could be empty, if the application has not yet received any signals.
9777 For example, it will be empty before you execute the @code{run} command.
9780 @vindex $_tlb@r{, convenience variable}
9781 The variable @code{$_tlb} is automatically set when debugging
9782 applications running on MS-Windows in native mode or connected to
9783 gdbserver that supports the @code{qGetTIBAddr} request.
9784 @xref{General Query Packets}.
9785 This variable contains the address of the thread information block.
9789 On HP-UX systems, if you refer to a function or variable name that
9790 begins with a dollar sign, @value{GDBN} searches for a user or system
9791 name first, before it searches for a convenience variable.
9793 @node Convenience Funs
9794 @section Convenience Functions
9796 @cindex convenience functions
9797 @value{GDBN} also supplies some @dfn{convenience functions}. These
9798 have a syntax similar to convenience variables. A convenience
9799 function can be used in an expression just like an ordinary function;
9800 however, a convenience function is implemented internally to
9803 These functions do not require @value{GDBN} to be configured with
9804 @code{Python} support, which means that they are always available.
9808 @item $_isvoid (@var{expr})
9809 @findex $_isvoid@r{, convenience function}
9810 Return one if the expression @var{expr} is @code{void}. Otherwise it
9813 A @code{void} expression is an expression where the type of the result
9814 is @code{void}. For example, you can examine a convenience variable
9815 (see @ref{Convenience Vars,, Convenience Variables}) to check whether
9819 (@value{GDBP}) print $_exitcode
9821 (@value{GDBP}) print $_isvoid ($_exitcode)
9824 Starting program: ./a.out
9825 [Inferior 1 (process 29572) exited normally]
9826 (@value{GDBP}) print $_exitcode
9828 (@value{GDBP}) print $_isvoid ($_exitcode)
9832 In the example above, we used @code{$_isvoid} to check whether
9833 @code{$_exitcode} is @code{void} before and after the execution of the
9834 program being debugged. Before the execution there is no exit code to
9835 be examined, therefore @code{$_exitcode} is @code{void}. After the
9836 execution the program being debugged returned zero, therefore
9837 @code{$_exitcode} is zero, which means that it is not @code{void}
9840 The @code{void} expression can also be a call of a function from the
9841 program being debugged. For example, given the following function:
9850 The result of calling it inside @value{GDBN} is @code{void}:
9853 (@value{GDBP}) print foo ()
9855 (@value{GDBP}) print $_isvoid (foo ())
9857 (@value{GDBP}) set $v = foo ()
9858 (@value{GDBP}) print $v
9860 (@value{GDBP}) print $_isvoid ($v)
9866 These functions require @value{GDBN} to be configured with
9867 @code{Python} support.
9871 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9872 @findex $_memeq@r{, convenience function}
9873 Returns one if the @var{length} bytes at the addresses given by
9874 @var{buf1} and @var{buf2} are equal.
9875 Otherwise it returns zero.
9877 @item $_regex(@var{str}, @var{regex})
9878 @findex $_regex@r{, convenience function}
9879 Returns one if the string @var{str} matches the regular expression
9880 @var{regex}. Otherwise it returns zero.
9881 The syntax of the regular expression is that specified by @code{Python}'s
9882 regular expression support.
9884 @item $_streq(@var{str1}, @var{str2})
9885 @findex $_streq@r{, convenience function}
9886 Returns one if the strings @var{str1} and @var{str2} are equal.
9887 Otherwise it returns zero.
9889 @item $_strlen(@var{str})
9890 @findex $_strlen@r{, convenience function}
9891 Returns the length of string @var{str}.
9895 @value{GDBN} provides the ability to list and get help on
9896 convenience functions.
9900 @kindex help function
9901 @cindex show all convenience functions
9902 Print a list of all convenience functions.
9909 You can refer to machine register contents, in expressions, as variables
9910 with names starting with @samp{$}. The names of registers are different
9911 for each machine; use @code{info registers} to see the names used on
9915 @kindex info registers
9916 @item info registers
9917 Print the names and values of all registers except floating-point
9918 and vector registers (in the selected stack frame).
9920 @kindex info all-registers
9921 @cindex floating point registers
9922 @item info all-registers
9923 Print the names and values of all registers, including floating-point
9924 and vector registers (in the selected stack frame).
9926 @item info registers @var{regname} @dots{}
9927 Print the @dfn{relativized} value of each specified register @var{regname}.
9928 As discussed in detail below, register values are normally relative to
9929 the selected stack frame. @var{regname} may be any register name valid on
9930 the machine you are using, with or without the initial @samp{$}.
9933 @cindex stack pointer register
9934 @cindex program counter register
9935 @cindex process status register
9936 @cindex frame pointer register
9937 @cindex standard registers
9938 @value{GDBN} has four ``standard'' register names that are available (in
9939 expressions) on most machines---whenever they do not conflict with an
9940 architecture's canonical mnemonics for registers. The register names
9941 @code{$pc} and @code{$sp} are used for the program counter register and
9942 the stack pointer. @code{$fp} is used for a register that contains a
9943 pointer to the current stack frame, and @code{$ps} is used for a
9944 register that contains the processor status. For example,
9945 you could print the program counter in hex with
9952 or print the instruction to be executed next with
9959 or add four to the stack pointer@footnote{This is a way of removing
9960 one word from the stack, on machines where stacks grow downward in
9961 memory (most machines, nowadays). This assumes that the innermost
9962 stack frame is selected; setting @code{$sp} is not allowed when other
9963 stack frames are selected. To pop entire frames off the stack,
9964 regardless of machine architecture, use @code{return};
9965 see @ref{Returning, ,Returning from a Function}.} with
9971 Whenever possible, these four standard register names are available on
9972 your machine even though the machine has different canonical mnemonics,
9973 so long as there is no conflict. The @code{info registers} command
9974 shows the canonical names. For example, on the SPARC, @code{info
9975 registers} displays the processor status register as @code{$psr} but you
9976 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9977 is an alias for the @sc{eflags} register.
9979 @value{GDBN} always considers the contents of an ordinary register as an
9980 integer when the register is examined in this way. Some machines have
9981 special registers which can hold nothing but floating point; these
9982 registers are considered to have floating point values. There is no way
9983 to refer to the contents of an ordinary register as floating point value
9984 (although you can @emph{print} it as a floating point value with
9985 @samp{print/f $@var{regname}}).
9987 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9988 means that the data format in which the register contents are saved by
9989 the operating system is not the same one that your program normally
9990 sees. For example, the registers of the 68881 floating point
9991 coprocessor are always saved in ``extended'' (raw) format, but all C
9992 programs expect to work with ``double'' (virtual) format. In such
9993 cases, @value{GDBN} normally works with the virtual format only (the format
9994 that makes sense for your program), but the @code{info registers} command
9995 prints the data in both formats.
9997 @cindex SSE registers (x86)
9998 @cindex MMX registers (x86)
9999 Some machines have special registers whose contents can be interpreted
10000 in several different ways. For example, modern x86-based machines
10001 have SSE and MMX registers that can hold several values packed
10002 together in several different formats. @value{GDBN} refers to such
10003 registers in @code{struct} notation:
10006 (@value{GDBP}) print $xmm1
10008 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
10009 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
10010 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
10011 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
10012 v4_int32 = @{0, 20657912, 11, 13@},
10013 v2_int64 = @{88725056443645952, 55834574859@},
10014 uint128 = 0x0000000d0000000b013b36f800000000
10019 To set values of such registers, you need to tell @value{GDBN} which
10020 view of the register you wish to change, as if you were assigning
10021 value to a @code{struct} member:
10024 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
10027 Normally, register values are relative to the selected stack frame
10028 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
10029 value that the register would contain if all stack frames farther in
10030 were exited and their saved registers restored. In order to see the
10031 true contents of hardware registers, you must select the innermost
10032 frame (with @samp{frame 0}).
10034 However, @value{GDBN} must deduce where registers are saved, from the machine
10035 code generated by your compiler. If some registers are not saved, or if
10036 @value{GDBN} is unable to locate the saved registers, the selected stack
10037 frame makes no difference.
10039 @node Floating Point Hardware
10040 @section Floating Point Hardware
10041 @cindex floating point
10043 Depending on the configuration, @value{GDBN} may be able to give
10044 you more information about the status of the floating point hardware.
10049 Display hardware-dependent information about the floating
10050 point unit. The exact contents and layout vary depending on the
10051 floating point chip. Currently, @samp{info float} is supported on
10052 the ARM and x86 machines.
10056 @section Vector Unit
10057 @cindex vector unit
10059 Depending on the configuration, @value{GDBN} may be able to give you
10060 more information about the status of the vector unit.
10063 @kindex info vector
10065 Display information about the vector unit. The exact contents and
10066 layout vary depending on the hardware.
10069 @node OS Information
10070 @section Operating System Auxiliary Information
10071 @cindex OS information
10073 @value{GDBN} provides interfaces to useful OS facilities that can help
10074 you debug your program.
10076 @cindex auxiliary vector
10077 @cindex vector, auxiliary
10078 Some operating systems supply an @dfn{auxiliary vector} to programs at
10079 startup. This is akin to the arguments and environment that you
10080 specify for a program, but contains a system-dependent variety of
10081 binary values that tell system libraries important details about the
10082 hardware, operating system, and process. Each value's purpose is
10083 identified by an integer tag; the meanings are well-known but system-specific.
10084 Depending on the configuration and operating system facilities,
10085 @value{GDBN} may be able to show you this information. For remote
10086 targets, this functionality may further depend on the remote stub's
10087 support of the @samp{qXfer:auxv:read} packet, see
10088 @ref{qXfer auxiliary vector read}.
10093 Display the auxiliary vector of the inferior, which can be either a
10094 live process or a core dump file. @value{GDBN} prints each tag value
10095 numerically, and also shows names and text descriptions for recognized
10096 tags. Some values in the vector are numbers, some bit masks, and some
10097 pointers to strings or other data. @value{GDBN} displays each value in the
10098 most appropriate form for a recognized tag, and in hexadecimal for
10099 an unrecognized tag.
10102 On some targets, @value{GDBN} can access operating system-specific
10103 information and show it to you. The types of information available
10104 will differ depending on the type of operating system running on the
10105 target. The mechanism used to fetch the data is described in
10106 @ref{Operating System Information}. For remote targets, this
10107 functionality depends on the remote stub's support of the
10108 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10112 @item info os @var{infotype}
10114 Display OS information of the requested type.
10116 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10118 @anchor{linux info os infotypes}
10120 @kindex info os processes
10122 Display the list of processes on the target. For each process,
10123 @value{GDBN} prints the process identifier, the name of the user, the
10124 command corresponding to the process, and the list of processor cores
10125 that the process is currently running on. (To understand what these
10126 properties mean, for this and the following info types, please consult
10127 the general @sc{gnu}/Linux documentation.)
10129 @kindex info os procgroups
10131 Display the list of process groups on the target. For each process,
10132 @value{GDBN} prints the identifier of the process group that it belongs
10133 to, the command corresponding to the process group leader, the process
10134 identifier, and the command line of the process. The list is sorted
10135 first by the process group identifier, then by the process identifier,
10136 so that processes belonging to the same process group are grouped together
10137 and the process group leader is listed first.
10139 @kindex info os threads
10141 Display the list of threads running on the target. For each thread,
10142 @value{GDBN} prints the identifier of the process that the thread
10143 belongs to, the command of the process, the thread identifier, and the
10144 processor core that it is currently running on. The main thread of a
10145 process is not listed.
10147 @kindex info os files
10149 Display the list of open file descriptors on the target. For each
10150 file descriptor, @value{GDBN} prints the identifier of the process
10151 owning the descriptor, the command of the owning process, the value
10152 of the descriptor, and the target of the descriptor.
10154 @kindex info os sockets
10156 Display the list of Internet-domain sockets on the target. For each
10157 socket, @value{GDBN} prints the address and port of the local and
10158 remote endpoints, the current state of the connection, the creator of
10159 the socket, the IP address family of the socket, and the type of the
10162 @kindex info os shm
10164 Display the list of all System V shared-memory regions on the target.
10165 For each shared-memory region, @value{GDBN} prints the region key,
10166 the shared-memory identifier, the access permissions, the size of the
10167 region, the process that created the region, the process that last
10168 attached to or detached from the region, the current number of live
10169 attaches to the region, and the times at which the region was last
10170 attached to, detach from, and changed.
10172 @kindex info os semaphores
10174 Display the list of all System V semaphore sets on the target. For each
10175 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10176 set identifier, the access permissions, the number of semaphores in the
10177 set, the user and group of the owner and creator of the semaphore set,
10178 and the times at which the semaphore set was operated upon and changed.
10180 @kindex info os msg
10182 Display the list of all System V message queues on the target. For each
10183 message queue, @value{GDBN} prints the message queue key, the message
10184 queue identifier, the access permissions, the current number of bytes
10185 on the queue, the current number of messages on the queue, the processes
10186 that last sent and received a message on the queue, the user and group
10187 of the owner and creator of the message queue, the times at which a
10188 message was last sent and received on the queue, and the time at which
10189 the message queue was last changed.
10191 @kindex info os modules
10193 Display the list of all loaded kernel modules on the target. For each
10194 module, @value{GDBN} prints the module name, the size of the module in
10195 bytes, the number of times the module is used, the dependencies of the
10196 module, the status of the module, and the address of the loaded module
10201 If @var{infotype} is omitted, then list the possible values for
10202 @var{infotype} and the kind of OS information available for each
10203 @var{infotype}. If the target does not return a list of possible
10204 types, this command will report an error.
10207 @node Memory Region Attributes
10208 @section Memory Region Attributes
10209 @cindex memory region attributes
10211 @dfn{Memory region attributes} allow you to describe special handling
10212 required by regions of your target's memory. @value{GDBN} uses
10213 attributes to determine whether to allow certain types of memory
10214 accesses; whether to use specific width accesses; and whether to cache
10215 target memory. By default the description of memory regions is
10216 fetched from the target (if the current target supports this), but the
10217 user can override the fetched regions.
10219 Defined memory regions can be individually enabled and disabled. When a
10220 memory region is disabled, @value{GDBN} uses the default attributes when
10221 accessing memory in that region. Similarly, if no memory regions have
10222 been defined, @value{GDBN} uses the default attributes when accessing
10225 When a memory region is defined, it is given a number to identify it;
10226 to enable, disable, or remove a memory region, you specify that number.
10230 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10231 Define a memory region bounded by @var{lower} and @var{upper} with
10232 attributes @var{attributes}@dots{}, and add it to the list of regions
10233 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10234 case: it is treated as the target's maximum memory address.
10235 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10238 Discard any user changes to the memory regions and use target-supplied
10239 regions, if available, or no regions if the target does not support.
10242 @item delete mem @var{nums}@dots{}
10243 Remove memory regions @var{nums}@dots{} from the list of regions
10244 monitored by @value{GDBN}.
10246 @kindex disable mem
10247 @item disable mem @var{nums}@dots{}
10248 Disable monitoring of memory regions @var{nums}@dots{}.
10249 A disabled memory region is not forgotten.
10250 It may be enabled again later.
10253 @item enable mem @var{nums}@dots{}
10254 Enable monitoring of memory regions @var{nums}@dots{}.
10258 Print a table of all defined memory regions, with the following columns
10262 @item Memory Region Number
10263 @item Enabled or Disabled.
10264 Enabled memory regions are marked with @samp{y}.
10265 Disabled memory regions are marked with @samp{n}.
10268 The address defining the inclusive lower bound of the memory region.
10271 The address defining the exclusive upper bound of the memory region.
10274 The list of attributes set for this memory region.
10279 @subsection Attributes
10281 @subsubsection Memory Access Mode
10282 The access mode attributes set whether @value{GDBN} may make read or
10283 write accesses to a memory region.
10285 While these attributes prevent @value{GDBN} from performing invalid
10286 memory accesses, they do nothing to prevent the target system, I/O DMA,
10287 etc.@: from accessing memory.
10291 Memory is read only.
10293 Memory is write only.
10295 Memory is read/write. This is the default.
10298 @subsubsection Memory Access Size
10299 The access size attribute tells @value{GDBN} to use specific sized
10300 accesses in the memory region. Often memory mapped device registers
10301 require specific sized accesses. If no access size attribute is
10302 specified, @value{GDBN} may use accesses of any size.
10306 Use 8 bit memory accesses.
10308 Use 16 bit memory accesses.
10310 Use 32 bit memory accesses.
10312 Use 64 bit memory accesses.
10315 @c @subsubsection Hardware/Software Breakpoints
10316 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10317 @c will use hardware or software breakpoints for the internal breakpoints
10318 @c used by the step, next, finish, until, etc. commands.
10322 @c Always use hardware breakpoints
10323 @c @item swbreak (default)
10326 @subsubsection Data Cache
10327 The data cache attributes set whether @value{GDBN} will cache target
10328 memory. While this generally improves performance by reducing debug
10329 protocol overhead, it can lead to incorrect results because @value{GDBN}
10330 does not know about volatile variables or memory mapped device
10335 Enable @value{GDBN} to cache target memory.
10337 Disable @value{GDBN} from caching target memory. This is the default.
10340 @subsection Memory Access Checking
10341 @value{GDBN} can be instructed to refuse accesses to memory that is
10342 not explicitly described. This can be useful if accessing such
10343 regions has undesired effects for a specific target, or to provide
10344 better error checking. The following commands control this behaviour.
10347 @kindex set mem inaccessible-by-default
10348 @item set mem inaccessible-by-default [on|off]
10349 If @code{on} is specified, make @value{GDBN} treat memory not
10350 explicitly described by the memory ranges as non-existent and refuse accesses
10351 to such memory. The checks are only performed if there's at least one
10352 memory range defined. If @code{off} is specified, make @value{GDBN}
10353 treat the memory not explicitly described by the memory ranges as RAM.
10354 The default value is @code{on}.
10355 @kindex show mem inaccessible-by-default
10356 @item show mem inaccessible-by-default
10357 Show the current handling of accesses to unknown memory.
10361 @c @subsubsection Memory Write Verification
10362 @c The memory write verification attributes set whether @value{GDBN}
10363 @c will re-reads data after each write to verify the write was successful.
10367 @c @item noverify (default)
10370 @node Dump/Restore Files
10371 @section Copy Between Memory and a File
10372 @cindex dump/restore files
10373 @cindex append data to a file
10374 @cindex dump data to a file
10375 @cindex restore data from a file
10377 You can use the commands @code{dump}, @code{append}, and
10378 @code{restore} to copy data between target memory and a file. The
10379 @code{dump} and @code{append} commands write data to a file, and the
10380 @code{restore} command reads data from a file back into the inferior's
10381 memory. Files may be in binary, Motorola S-record, Intel hex, or
10382 Tektronix Hex format; however, @value{GDBN} can only append to binary
10388 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10389 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10390 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10391 or the value of @var{expr}, to @var{filename} in the given format.
10393 The @var{format} parameter may be any one of:
10400 Motorola S-record format.
10402 Tektronix Hex format.
10405 @value{GDBN} uses the same definitions of these formats as the
10406 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10407 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10411 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10412 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10413 Append the contents of memory from @var{start_addr} to @var{end_addr},
10414 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10415 (@value{GDBN} can only append data to files in raw binary form.)
10418 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10419 Restore the contents of file @var{filename} into memory. The
10420 @code{restore} command can automatically recognize any known @sc{bfd}
10421 file format, except for raw binary. To restore a raw binary file you
10422 must specify the optional keyword @code{binary} after the filename.
10424 If @var{bias} is non-zero, its value will be added to the addresses
10425 contained in the file. Binary files always start at address zero, so
10426 they will be restored at address @var{bias}. Other bfd files have
10427 a built-in location; they will be restored at offset @var{bias}
10428 from that location.
10430 If @var{start} and/or @var{end} are non-zero, then only data between
10431 file offset @var{start} and file offset @var{end} will be restored.
10432 These offsets are relative to the addresses in the file, before
10433 the @var{bias} argument is applied.
10437 @node Core File Generation
10438 @section How to Produce a Core File from Your Program
10439 @cindex dump core from inferior
10441 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10442 image of a running process and its process status (register values
10443 etc.). Its primary use is post-mortem debugging of a program that
10444 crashed while it ran outside a debugger. A program that crashes
10445 automatically produces a core file, unless this feature is disabled by
10446 the user. @xref{Files}, for information on invoking @value{GDBN} in
10447 the post-mortem debugging mode.
10449 Occasionally, you may wish to produce a core file of the program you
10450 are debugging in order to preserve a snapshot of its state.
10451 @value{GDBN} has a special command for that.
10455 @kindex generate-core-file
10456 @item generate-core-file [@var{file}]
10457 @itemx gcore [@var{file}]
10458 Produce a core dump of the inferior process. The optional argument
10459 @var{file} specifies the file name where to put the core dump. If not
10460 specified, the file name defaults to @file{core.@var{pid}}, where
10461 @var{pid} is the inferior process ID.
10463 Note that this command is implemented only for some systems (as of
10464 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10467 @node Character Sets
10468 @section Character Sets
10469 @cindex character sets
10471 @cindex translating between character sets
10472 @cindex host character set
10473 @cindex target character set
10475 If the program you are debugging uses a different character set to
10476 represent characters and strings than the one @value{GDBN} uses itself,
10477 @value{GDBN} can automatically translate between the character sets for
10478 you. The character set @value{GDBN} uses we call the @dfn{host
10479 character set}; the one the inferior program uses we call the
10480 @dfn{target character set}.
10482 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10483 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10484 remote protocol (@pxref{Remote Debugging}) to debug a program
10485 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10486 then the host character set is Latin-1, and the target character set is
10487 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10488 target-charset EBCDIC-US}, then @value{GDBN} translates between
10489 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10490 character and string literals in expressions.
10492 @value{GDBN} has no way to automatically recognize which character set
10493 the inferior program uses; you must tell it, using the @code{set
10494 target-charset} command, described below.
10496 Here are the commands for controlling @value{GDBN}'s character set
10500 @item set target-charset @var{charset}
10501 @kindex set target-charset
10502 Set the current target character set to @var{charset}. To display the
10503 list of supported target character sets, type
10504 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10506 @item set host-charset @var{charset}
10507 @kindex set host-charset
10508 Set the current host character set to @var{charset}.
10510 By default, @value{GDBN} uses a host character set appropriate to the
10511 system it is running on; you can override that default using the
10512 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10513 automatically determine the appropriate host character set. In this
10514 case, @value{GDBN} uses @samp{UTF-8}.
10516 @value{GDBN} can only use certain character sets as its host character
10517 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10518 @value{GDBN} will list the host character sets it supports.
10520 @item set charset @var{charset}
10521 @kindex set charset
10522 Set the current host and target character sets to @var{charset}. As
10523 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10524 @value{GDBN} will list the names of the character sets that can be used
10525 for both host and target.
10528 @kindex show charset
10529 Show the names of the current host and target character sets.
10531 @item show host-charset
10532 @kindex show host-charset
10533 Show the name of the current host character set.
10535 @item show target-charset
10536 @kindex show target-charset
10537 Show the name of the current target character set.
10539 @item set target-wide-charset @var{charset}
10540 @kindex set target-wide-charset
10541 Set the current target's wide character set to @var{charset}. This is
10542 the character set used by the target's @code{wchar_t} type. To
10543 display the list of supported wide character sets, type
10544 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10546 @item show target-wide-charset
10547 @kindex show target-wide-charset
10548 Show the name of the current target's wide character set.
10551 Here is an example of @value{GDBN}'s character set support in action.
10552 Assume that the following source code has been placed in the file
10553 @file{charset-test.c}:
10559 = @{72, 101, 108, 108, 111, 44, 32, 119,
10560 111, 114, 108, 100, 33, 10, 0@};
10561 char ibm1047_hello[]
10562 = @{200, 133, 147, 147, 150, 107, 64, 166,
10563 150, 153, 147, 132, 90, 37, 0@};
10567 printf ("Hello, world!\n");
10571 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10572 containing the string @samp{Hello, world!} followed by a newline,
10573 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10575 We compile the program, and invoke the debugger on it:
10578 $ gcc -g charset-test.c -o charset-test
10579 $ gdb -nw charset-test
10580 GNU gdb 2001-12-19-cvs
10581 Copyright 2001 Free Software Foundation, Inc.
10586 We can use the @code{show charset} command to see what character sets
10587 @value{GDBN} is currently using to interpret and display characters and
10591 (@value{GDBP}) show charset
10592 The current host and target character set is `ISO-8859-1'.
10596 For the sake of printing this manual, let's use @sc{ascii} as our
10597 initial character set:
10599 (@value{GDBP}) set charset ASCII
10600 (@value{GDBP}) show charset
10601 The current host and target character set is `ASCII'.
10605 Let's assume that @sc{ascii} is indeed the correct character set for our
10606 host system --- in other words, let's assume that if @value{GDBN} prints
10607 characters using the @sc{ascii} character set, our terminal will display
10608 them properly. Since our current target character set is also
10609 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10612 (@value{GDBP}) print ascii_hello
10613 $1 = 0x401698 "Hello, world!\n"
10614 (@value{GDBP}) print ascii_hello[0]
10619 @value{GDBN} uses the target character set for character and string
10620 literals you use in expressions:
10623 (@value{GDBP}) print '+'
10628 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10631 @value{GDBN} relies on the user to tell it which character set the
10632 target program uses. If we print @code{ibm1047_hello} while our target
10633 character set is still @sc{ascii}, we get jibberish:
10636 (@value{GDBP}) print ibm1047_hello
10637 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10638 (@value{GDBP}) print ibm1047_hello[0]
10643 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10644 @value{GDBN} tells us the character sets it supports:
10647 (@value{GDBP}) set target-charset
10648 ASCII EBCDIC-US IBM1047 ISO-8859-1
10649 (@value{GDBP}) set target-charset
10652 We can select @sc{ibm1047} as our target character set, and examine the
10653 program's strings again. Now the @sc{ascii} string is wrong, but
10654 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10655 target character set, @sc{ibm1047}, to the host character set,
10656 @sc{ascii}, and they display correctly:
10659 (@value{GDBP}) set target-charset IBM1047
10660 (@value{GDBP}) show charset
10661 The current host character set is `ASCII'.
10662 The current target character set is `IBM1047'.
10663 (@value{GDBP}) print ascii_hello
10664 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10665 (@value{GDBP}) print ascii_hello[0]
10667 (@value{GDBP}) print ibm1047_hello
10668 $8 = 0x4016a8 "Hello, world!\n"
10669 (@value{GDBP}) print ibm1047_hello[0]
10674 As above, @value{GDBN} uses the target character set for character and
10675 string literals you use in expressions:
10678 (@value{GDBP}) print '+'
10683 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10686 @node Caching Remote Data
10687 @section Caching Data of Remote Targets
10688 @cindex caching data of remote targets
10690 @value{GDBN} caches data exchanged between the debugger and a
10691 remote target (@pxref{Remote Debugging}). Such caching generally improves
10692 performance, because it reduces the overhead of the remote protocol by
10693 bundling memory reads and writes into large chunks. Unfortunately, simply
10694 caching everything would lead to incorrect results, since @value{GDBN}
10695 does not necessarily know anything about volatile values, memory-mapped I/O
10696 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10697 memory can be changed @emph{while} a gdb command is executing.
10698 Therefore, by default, @value{GDBN} only caches data
10699 known to be on the stack@footnote{In non-stop mode, it is moderately
10700 rare for a running thread to modify the stack of a stopped thread
10701 in a way that would interfere with a backtrace, and caching of
10702 stack reads provides a significant speed up of remote backtraces.}.
10703 Other regions of memory can be explicitly marked as
10704 cacheable; see @pxref{Memory Region Attributes}.
10707 @kindex set remotecache
10708 @item set remotecache on
10709 @itemx set remotecache off
10710 This option no longer does anything; it exists for compatibility
10713 @kindex show remotecache
10714 @item show remotecache
10715 Show the current state of the obsolete remotecache flag.
10717 @kindex set stack-cache
10718 @item set stack-cache on
10719 @itemx set stack-cache off
10720 Enable or disable caching of stack accesses. When @code{ON}, use
10721 caching. By default, this option is @code{ON}.
10723 @kindex show stack-cache
10724 @item show stack-cache
10725 Show the current state of data caching for memory accesses.
10727 @kindex info dcache
10728 @item info dcache @r{[}line@r{]}
10729 Print the information about the data cache performance. The
10730 information displayed includes the dcache width and depth, and for
10731 each cache line, its number, address, and how many times it was
10732 referenced. This command is useful for debugging the data cache
10735 If a line number is specified, the contents of that line will be
10738 @item set dcache size @var{size}
10739 @cindex dcache size
10740 @kindex set dcache size
10741 Set maximum number of entries in dcache (dcache depth above).
10743 @item set dcache line-size @var{line-size}
10744 @cindex dcache line-size
10745 @kindex set dcache line-size
10746 Set number of bytes each dcache entry caches (dcache width above).
10747 Must be a power of 2.
10749 @item show dcache size
10750 @kindex show dcache size
10751 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10753 @item show dcache line-size
10754 @kindex show dcache line-size
10755 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10759 @node Searching Memory
10760 @section Search Memory
10761 @cindex searching memory
10763 Memory can be searched for a particular sequence of bytes with the
10764 @code{find} command.
10768 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10769 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10770 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10771 etc. The search begins at address @var{start_addr} and continues for either
10772 @var{len} bytes or through to @var{end_addr} inclusive.
10775 @var{s} and @var{n} are optional parameters.
10776 They may be specified in either order, apart or together.
10779 @item @var{s}, search query size
10780 The size of each search query value.
10786 halfwords (two bytes)
10790 giant words (eight bytes)
10793 All values are interpreted in the current language.
10794 This means, for example, that if the current source language is C/C@t{++}
10795 then searching for the string ``hello'' includes the trailing '\0'.
10797 If the value size is not specified, it is taken from the
10798 value's type in the current language.
10799 This is useful when one wants to specify the search
10800 pattern as a mixture of types.
10801 Note that this means, for example, that in the case of C-like languages
10802 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10803 which is typically four bytes.
10805 @item @var{n}, maximum number of finds
10806 The maximum number of matches to print. The default is to print all finds.
10809 You can use strings as search values. Quote them with double-quotes
10811 The string value is copied into the search pattern byte by byte,
10812 regardless of the endianness of the target and the size specification.
10814 The address of each match found is printed as well as a count of the
10815 number of matches found.
10817 The address of the last value found is stored in convenience variable
10819 A count of the number of matches is stored in @samp{$numfound}.
10821 For example, if stopped at the @code{printf} in this function:
10827 static char hello[] = "hello-hello";
10828 static struct @{ char c; short s; int i; @}
10829 __attribute__ ((packed)) mixed
10830 = @{ 'c', 0x1234, 0x87654321 @};
10831 printf ("%s\n", hello);
10836 you get during debugging:
10839 (gdb) find &hello[0], +sizeof(hello), "hello"
10840 0x804956d <hello.1620+6>
10842 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10843 0x8049567 <hello.1620>
10844 0x804956d <hello.1620+6>
10846 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10847 0x8049567 <hello.1620>
10849 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10850 0x8049560 <mixed.1625>
10852 (gdb) print $numfound
10855 $2 = (void *) 0x8049560
10858 @node Optimized Code
10859 @chapter Debugging Optimized Code
10860 @cindex optimized code, debugging
10861 @cindex debugging optimized code
10863 Almost all compilers support optimization. With optimization
10864 disabled, the compiler generates assembly code that corresponds
10865 directly to your source code, in a simplistic way. As the compiler
10866 applies more powerful optimizations, the generated assembly code
10867 diverges from your original source code. With help from debugging
10868 information generated by the compiler, @value{GDBN} can map from
10869 the running program back to constructs from your original source.
10871 @value{GDBN} is more accurate with optimization disabled. If you
10872 can recompile without optimization, it is easier to follow the
10873 progress of your program during debugging. But, there are many cases
10874 where you may need to debug an optimized version.
10876 When you debug a program compiled with @samp{-g -O}, remember that the
10877 optimizer has rearranged your code; the debugger shows you what is
10878 really there. Do not be too surprised when the execution path does not
10879 exactly match your source file! An extreme example: if you define a
10880 variable, but never use it, @value{GDBN} never sees that
10881 variable---because the compiler optimizes it out of existence.
10883 Some things do not work as well with @samp{-g -O} as with just
10884 @samp{-g}, particularly on machines with instruction scheduling. If in
10885 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10886 please report it to us as a bug (including a test case!).
10887 @xref{Variables}, for more information about debugging optimized code.
10890 * Inline Functions:: How @value{GDBN} presents inlining
10891 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10894 @node Inline Functions
10895 @section Inline Functions
10896 @cindex inline functions, debugging
10898 @dfn{Inlining} is an optimization that inserts a copy of the function
10899 body directly at each call site, instead of jumping to a shared
10900 routine. @value{GDBN} displays inlined functions just like
10901 non-inlined functions. They appear in backtraces. You can view their
10902 arguments and local variables, step into them with @code{step}, skip
10903 them with @code{next}, and escape from them with @code{finish}.
10904 You can check whether a function was inlined by using the
10905 @code{info frame} command.
10907 For @value{GDBN} to support inlined functions, the compiler must
10908 record information about inlining in the debug information ---
10909 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10910 other compilers do also. @value{GDBN} only supports inlined functions
10911 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10912 do not emit two required attributes (@samp{DW_AT_call_file} and
10913 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10914 function calls with earlier versions of @value{NGCC}. It instead
10915 displays the arguments and local variables of inlined functions as
10916 local variables in the caller.
10918 The body of an inlined function is directly included at its call site;
10919 unlike a non-inlined function, there are no instructions devoted to
10920 the call. @value{GDBN} still pretends that the call site and the
10921 start of the inlined function are different instructions. Stepping to
10922 the call site shows the call site, and then stepping again shows
10923 the first line of the inlined function, even though no additional
10924 instructions are executed.
10926 This makes source-level debugging much clearer; you can see both the
10927 context of the call and then the effect of the call. Only stepping by
10928 a single instruction using @code{stepi} or @code{nexti} does not do
10929 this; single instruction steps always show the inlined body.
10931 There are some ways that @value{GDBN} does not pretend that inlined
10932 function calls are the same as normal calls:
10936 Setting breakpoints at the call site of an inlined function may not
10937 work, because the call site does not contain any code. @value{GDBN}
10938 may incorrectly move the breakpoint to the next line of the enclosing
10939 function, after the call. This limitation will be removed in a future
10940 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10941 or inside the inlined function instead.
10944 @value{GDBN} cannot locate the return value of inlined calls after
10945 using the @code{finish} command. This is a limitation of compiler-generated
10946 debugging information; after @code{finish}, you can step to the next line
10947 and print a variable where your program stored the return value.
10951 @node Tail Call Frames
10952 @section Tail Call Frames
10953 @cindex tail call frames, debugging
10955 Function @code{B} can call function @code{C} in its very last statement. In
10956 unoptimized compilation the call of @code{C} is immediately followed by return
10957 instruction at the end of @code{B} code. Optimizing compiler may replace the
10958 call and return in function @code{B} into one jump to function @code{C}
10959 instead. Such use of a jump instruction is called @dfn{tail call}.
10961 During execution of function @code{C}, there will be no indication in the
10962 function call stack frames that it was tail-called from @code{B}. If function
10963 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10964 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10965 some cases @value{GDBN} can determine that @code{C} was tail-called from
10966 @code{B}, and it will then create fictitious call frame for that, with the
10967 return address set up as if @code{B} called @code{C} normally.
10969 This functionality is currently supported only by DWARF 2 debugging format and
10970 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10971 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10974 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10975 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10979 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10981 Stack level 1, frame at 0x7fffffffda30:
10982 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10983 tail call frame, caller of frame at 0x7fffffffda30
10984 source language c++.
10985 Arglist at unknown address.
10986 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10989 The detection of all the possible code path executions can find them ambiguous.
10990 There is no execution history stored (possible @ref{Reverse Execution} is never
10991 used for this purpose) and the last known caller could have reached the known
10992 callee by multiple different jump sequences. In such case @value{GDBN} still
10993 tries to show at least all the unambiguous top tail callers and all the
10994 unambiguous bottom tail calees, if any.
10997 @anchor{set debug entry-values}
10998 @item set debug entry-values
10999 @kindex set debug entry-values
11000 When set to on, enables printing of analysis messages for both frame argument
11001 values at function entry and tail calls. It will show all the possible valid
11002 tail calls code paths it has considered. It will also print the intersection
11003 of them with the final unambiguous (possibly partial or even empty) code path
11006 @item show debug entry-values
11007 @kindex show debug entry-values
11008 Show the current state of analysis messages printing for both frame argument
11009 values at function entry and tail calls.
11012 The analysis messages for tail calls can for example show why the virtual tail
11013 call frame for function @code{c} has not been recognized (due to the indirect
11014 reference by variable @code{x}):
11017 static void __attribute__((noinline, noclone)) c (void);
11018 void (*x) (void) = c;
11019 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11020 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
11021 int main (void) @{ x (); return 0; @}
11023 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
11024 DW_TAG_GNU_call_site 0x40039a in main
11026 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
11029 #1 0x000000000040039a in main () at t.c:5
11032 Another possibility is an ambiguous virtual tail call frames resolution:
11036 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
11037 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
11038 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
11039 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
11040 static void __attribute__((noinline, noclone)) b (void)
11041 @{ if (i) c (); else e (); @}
11042 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
11043 int main (void) @{ a (); return 0; @}
11045 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
11046 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
11047 tailcall: reduced: 0x4004d2(a) |
11050 #1 0x00000000004004d2 in a () at t.c:8
11051 #2 0x0000000000400395 in main () at t.c:9
11054 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
11055 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
11057 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
11058 @ifset HAVE_MAKEINFO_CLICK
11059 @set ARROW @click{}
11060 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
11061 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
11063 @ifclear HAVE_MAKEINFO_CLICK
11065 @set CALLSEQ1B @value{CALLSEQ1A}
11066 @set CALLSEQ2B @value{CALLSEQ2A}
11069 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11070 The code can have possible execution paths @value{CALLSEQ1B} or
11071 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11073 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11074 has found. It then finds another possible calling sequcen - that one is
11075 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11076 printed as the @code{reduced:} calling sequence. That one could have many
11077 futher @code{compare:} and @code{reduced:} statements as long as there remain
11078 any non-ambiguous sequence entries.
11080 For the frame of function @code{b} in both cases there are different possible
11081 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11082 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11083 therefore this one is displayed to the user while the ambiguous frames are
11086 There can be also reasons why printing of frame argument values at function
11091 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11092 static void __attribute__((noinline, noclone)) a (int i);
11093 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11094 static void __attribute__((noinline, noclone)) a (int i)
11095 @{ if (i) b (i - 1); else c (0); @}
11096 int main (void) @{ a (5); return 0; @}
11099 #0 c (i=i@@entry=0) at t.c:2
11100 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11101 function "a" at 0x400420 can call itself via tail calls
11102 i=<optimized out>) at t.c:6
11103 #2 0x000000000040036e in main () at t.c:7
11106 @value{GDBN} cannot find out from the inferior state if and how many times did
11107 function @code{a} call itself (via function @code{b}) as these calls would be
11108 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11109 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11110 prints @code{<optimized out>} instead.
11113 @chapter C Preprocessor Macros
11115 Some languages, such as C and C@t{++}, provide a way to define and invoke
11116 ``preprocessor macros'' which expand into strings of tokens.
11117 @value{GDBN} can evaluate expressions containing macro invocations, show
11118 the result of macro expansion, and show a macro's definition, including
11119 where it was defined.
11121 You may need to compile your program specially to provide @value{GDBN}
11122 with information about preprocessor macros. Most compilers do not
11123 include macros in their debugging information, even when you compile
11124 with the @option{-g} flag. @xref{Compilation}.
11126 A program may define a macro at one point, remove that definition later,
11127 and then provide a different definition after that. Thus, at different
11128 points in the program, a macro may have different definitions, or have
11129 no definition at all. If there is a current stack frame, @value{GDBN}
11130 uses the macros in scope at that frame's source code line. Otherwise,
11131 @value{GDBN} uses the macros in scope at the current listing location;
11134 Whenever @value{GDBN} evaluates an expression, it always expands any
11135 macro invocations present in the expression. @value{GDBN} also provides
11136 the following commands for working with macros explicitly.
11140 @kindex macro expand
11141 @cindex macro expansion, showing the results of preprocessor
11142 @cindex preprocessor macro expansion, showing the results of
11143 @cindex expanding preprocessor macros
11144 @item macro expand @var{expression}
11145 @itemx macro exp @var{expression}
11146 Show the results of expanding all preprocessor macro invocations in
11147 @var{expression}. Since @value{GDBN} simply expands macros, but does
11148 not parse the result, @var{expression} need not be a valid expression;
11149 it can be any string of tokens.
11152 @item macro expand-once @var{expression}
11153 @itemx macro exp1 @var{expression}
11154 @cindex expand macro once
11155 @i{(This command is not yet implemented.)} Show the results of
11156 expanding those preprocessor macro invocations that appear explicitly in
11157 @var{expression}. Macro invocations appearing in that expansion are
11158 left unchanged. This command allows you to see the effect of a
11159 particular macro more clearly, without being confused by further
11160 expansions. Since @value{GDBN} simply expands macros, but does not
11161 parse the result, @var{expression} need not be a valid expression; it
11162 can be any string of tokens.
11165 @cindex macro definition, showing
11166 @cindex definition of a macro, showing
11167 @cindex macros, from debug info
11168 @item info macro [-a|-all] [--] @var{macro}
11169 Show the current definition or all definitions of the named @var{macro},
11170 and describe the source location or compiler command-line where that
11171 definition was established. The optional double dash is to signify the end of
11172 argument processing and the beginning of @var{macro} for non C-like macros where
11173 the macro may begin with a hyphen.
11175 @kindex info macros
11176 @item info macros @var{linespec}
11177 Show all macro definitions that are in effect at the location specified
11178 by @var{linespec}, and describe the source location or compiler
11179 command-line where those definitions were established.
11181 @kindex macro define
11182 @cindex user-defined macros
11183 @cindex defining macros interactively
11184 @cindex macros, user-defined
11185 @item macro define @var{macro} @var{replacement-list}
11186 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11187 Introduce a definition for a preprocessor macro named @var{macro},
11188 invocations of which are replaced by the tokens given in
11189 @var{replacement-list}. The first form of this command defines an
11190 ``object-like'' macro, which takes no arguments; the second form
11191 defines a ``function-like'' macro, which takes the arguments given in
11194 A definition introduced by this command is in scope in every
11195 expression evaluated in @value{GDBN}, until it is removed with the
11196 @code{macro undef} command, described below. The definition overrides
11197 all definitions for @var{macro} present in the program being debugged,
11198 as well as any previous user-supplied definition.
11200 @kindex macro undef
11201 @item macro undef @var{macro}
11202 Remove any user-supplied definition for the macro named @var{macro}.
11203 This command only affects definitions provided with the @code{macro
11204 define} command, described above; it cannot remove definitions present
11205 in the program being debugged.
11209 List all the macros defined using the @code{macro define} command.
11212 @cindex macros, example of debugging with
11213 Here is a transcript showing the above commands in action. First, we
11214 show our source files:
11219 #include "sample.h"
11222 #define ADD(x) (M + x)
11227 printf ("Hello, world!\n");
11229 printf ("We're so creative.\n");
11231 printf ("Goodbye, world!\n");
11238 Now, we compile the program using the @sc{gnu} C compiler,
11239 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11240 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11241 and @option{-gdwarf-4}; we recommend always choosing the most recent
11242 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11243 includes information about preprocessor macros in the debugging
11247 $ gcc -gdwarf-2 -g3 sample.c -o sample
11251 Now, we start @value{GDBN} on our sample program:
11255 GNU gdb 2002-05-06-cvs
11256 Copyright 2002 Free Software Foundation, Inc.
11257 GDB is free software, @dots{}
11261 We can expand macros and examine their definitions, even when the
11262 program is not running. @value{GDBN} uses the current listing position
11263 to decide which macro definitions are in scope:
11266 (@value{GDBP}) list main
11269 5 #define ADD(x) (M + x)
11274 10 printf ("Hello, world!\n");
11276 12 printf ("We're so creative.\n");
11277 (@value{GDBP}) info macro ADD
11278 Defined at /home/jimb/gdb/macros/play/sample.c:5
11279 #define ADD(x) (M + x)
11280 (@value{GDBP}) info macro Q
11281 Defined at /home/jimb/gdb/macros/play/sample.h:1
11282 included at /home/jimb/gdb/macros/play/sample.c:2
11284 (@value{GDBP}) macro expand ADD(1)
11285 expands to: (42 + 1)
11286 (@value{GDBP}) macro expand-once ADD(1)
11287 expands to: once (M + 1)
11291 In the example above, note that @code{macro expand-once} expands only
11292 the macro invocation explicit in the original text --- the invocation of
11293 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11294 which was introduced by @code{ADD}.
11296 Once the program is running, @value{GDBN} uses the macro definitions in
11297 force at the source line of the current stack frame:
11300 (@value{GDBP}) break main
11301 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11303 Starting program: /home/jimb/gdb/macros/play/sample
11305 Breakpoint 1, main () at sample.c:10
11306 10 printf ("Hello, world!\n");
11310 At line 10, the definition of the macro @code{N} at line 9 is in force:
11313 (@value{GDBP}) info macro N
11314 Defined at /home/jimb/gdb/macros/play/sample.c:9
11316 (@value{GDBP}) macro expand N Q M
11317 expands to: 28 < 42
11318 (@value{GDBP}) print N Q M
11323 As we step over directives that remove @code{N}'s definition, and then
11324 give it a new definition, @value{GDBN} finds the definition (or lack
11325 thereof) in force at each point:
11328 (@value{GDBP}) next
11330 12 printf ("We're so creative.\n");
11331 (@value{GDBP}) info macro N
11332 The symbol `N' has no definition as a C/C++ preprocessor macro
11333 at /home/jimb/gdb/macros/play/sample.c:12
11334 (@value{GDBP}) next
11336 14 printf ("Goodbye, world!\n");
11337 (@value{GDBP}) info macro N
11338 Defined at /home/jimb/gdb/macros/play/sample.c:13
11340 (@value{GDBP}) macro expand N Q M
11341 expands to: 1729 < 42
11342 (@value{GDBP}) print N Q M
11347 In addition to source files, macros can be defined on the compilation command
11348 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11349 such a way, @value{GDBN} displays the location of their definition as line zero
11350 of the source file submitted to the compiler.
11353 (@value{GDBP}) info macro __STDC__
11354 Defined at /home/jimb/gdb/macros/play/sample.c:0
11361 @chapter Tracepoints
11362 @c This chapter is based on the documentation written by Michael
11363 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11365 @cindex tracepoints
11366 In some applications, it is not feasible for the debugger to interrupt
11367 the program's execution long enough for the developer to learn
11368 anything helpful about its behavior. If the program's correctness
11369 depends on its real-time behavior, delays introduced by a debugger
11370 might cause the program to change its behavior drastically, or perhaps
11371 fail, even when the code itself is correct. It is useful to be able
11372 to observe the program's behavior without interrupting it.
11374 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11375 specify locations in the program, called @dfn{tracepoints}, and
11376 arbitrary expressions to evaluate when those tracepoints are reached.
11377 Later, using the @code{tfind} command, you can examine the values
11378 those expressions had when the program hit the tracepoints. The
11379 expressions may also denote objects in memory---structures or arrays,
11380 for example---whose values @value{GDBN} should record; while visiting
11381 a particular tracepoint, you may inspect those objects as if they were
11382 in memory at that moment. However, because @value{GDBN} records these
11383 values without interacting with you, it can do so quickly and
11384 unobtrusively, hopefully not disturbing the program's behavior.
11386 The tracepoint facility is currently available only for remote
11387 targets. @xref{Targets}. In addition, your remote target must know
11388 how to collect trace data. This functionality is implemented in the
11389 remote stub; however, none of the stubs distributed with @value{GDBN}
11390 support tracepoints as of this writing. The format of the remote
11391 packets used to implement tracepoints are described in @ref{Tracepoint
11394 It is also possible to get trace data from a file, in a manner reminiscent
11395 of corefiles; you specify the filename, and use @code{tfind} to search
11396 through the file. @xref{Trace Files}, for more details.
11398 This chapter describes the tracepoint commands and features.
11401 * Set Tracepoints::
11402 * Analyze Collected Data::
11403 * Tracepoint Variables::
11407 @node Set Tracepoints
11408 @section Commands to Set Tracepoints
11410 Before running such a @dfn{trace experiment}, an arbitrary number of
11411 tracepoints can be set. A tracepoint is actually a special type of
11412 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11413 standard breakpoint commands. For instance, as with breakpoints,
11414 tracepoint numbers are successive integers starting from one, and many
11415 of the commands associated with tracepoints take the tracepoint number
11416 as their argument, to identify which tracepoint to work on.
11418 For each tracepoint, you can specify, in advance, some arbitrary set
11419 of data that you want the target to collect in the trace buffer when
11420 it hits that tracepoint. The collected data can include registers,
11421 local variables, or global data. Later, you can use @value{GDBN}
11422 commands to examine the values these data had at the time the
11423 tracepoint was hit.
11425 Tracepoints do not support every breakpoint feature. Ignore counts on
11426 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11427 commands when they are hit. Tracepoints may not be thread-specific
11430 @cindex fast tracepoints
11431 Some targets may support @dfn{fast tracepoints}, which are inserted in
11432 a different way (such as with a jump instead of a trap), that is
11433 faster but possibly restricted in where they may be installed.
11435 @cindex static tracepoints
11436 @cindex markers, static tracepoints
11437 @cindex probing markers, static tracepoints
11438 Regular and fast tracepoints are dynamic tracing facilities, meaning
11439 that they can be used to insert tracepoints at (almost) any location
11440 in the target. Some targets may also support controlling @dfn{static
11441 tracepoints} from @value{GDBN}. With static tracing, a set of
11442 instrumentation points, also known as @dfn{markers}, are embedded in
11443 the target program, and can be activated or deactivated by name or
11444 address. These are usually placed at locations which facilitate
11445 investigating what the target is actually doing. @value{GDBN}'s
11446 support for static tracing includes being able to list instrumentation
11447 points, and attach them with @value{GDBN} defined high level
11448 tracepoints that expose the whole range of convenience of
11449 @value{GDBN}'s tracepoints support. Namely, support for collecting
11450 registers values and values of global or local (to the instrumentation
11451 point) variables; tracepoint conditions and trace state variables.
11452 The act of installing a @value{GDBN} static tracepoint on an
11453 instrumentation point, or marker, is referred to as @dfn{probing} a
11454 static tracepoint marker.
11456 @code{gdbserver} supports tracepoints on some target systems.
11457 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11459 This section describes commands to set tracepoints and associated
11460 conditions and actions.
11463 * Create and Delete Tracepoints::
11464 * Enable and Disable Tracepoints::
11465 * Tracepoint Passcounts::
11466 * Tracepoint Conditions::
11467 * Trace State Variables::
11468 * Tracepoint Actions::
11469 * Listing Tracepoints::
11470 * Listing Static Tracepoint Markers::
11471 * Starting and Stopping Trace Experiments::
11472 * Tracepoint Restrictions::
11475 @node Create and Delete Tracepoints
11476 @subsection Create and Delete Tracepoints
11479 @cindex set tracepoint
11481 @item trace @var{location}
11482 The @code{trace} command is very similar to the @code{break} command.
11483 Its argument @var{location} can be a source line, a function name, or
11484 an address in the target program. @xref{Specify Location}. The
11485 @code{trace} command defines a tracepoint, which is a point in the
11486 target program where the debugger will briefly stop, collect some
11487 data, and then allow the program to continue. Setting a tracepoint or
11488 changing its actions takes effect immediately if the remote stub
11489 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11491 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11492 these changes don't take effect until the next @code{tstart}
11493 command, and once a trace experiment is running, further changes will
11494 not have any effect until the next trace experiment starts. In addition,
11495 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11496 address is not yet resolved. (This is similar to pending breakpoints.)
11497 Pending tracepoints are not downloaded to the target and not installed
11498 until they are resolved. The resolution of pending tracepoints requires
11499 @value{GDBN} support---when debugging with the remote target, and
11500 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11501 tracing}), pending tracepoints can not be resolved (and downloaded to
11502 the remote stub) while @value{GDBN} is disconnected.
11504 Here are some examples of using the @code{trace} command:
11507 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11509 (@value{GDBP}) @b{trace +2} // 2 lines forward
11511 (@value{GDBP}) @b{trace my_function} // first source line of function
11513 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11515 (@value{GDBP}) @b{trace *0x2117c4} // an address
11519 You can abbreviate @code{trace} as @code{tr}.
11521 @item trace @var{location} if @var{cond}
11522 Set a tracepoint with condition @var{cond}; evaluate the expression
11523 @var{cond} each time the tracepoint is reached, and collect data only
11524 if the value is nonzero---that is, if @var{cond} evaluates as true.
11525 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11526 information on tracepoint conditions.
11528 @item ftrace @var{location} [ if @var{cond} ]
11529 @cindex set fast tracepoint
11530 @cindex fast tracepoints, setting
11532 The @code{ftrace} command sets a fast tracepoint. For targets that
11533 support them, fast tracepoints will use a more efficient but possibly
11534 less general technique to trigger data collection, such as a jump
11535 instruction instead of a trap, or some sort of hardware support. It
11536 may not be possible to create a fast tracepoint at the desired
11537 location, in which case the command will exit with an explanatory
11540 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11543 On 32-bit x86-architecture systems, fast tracepoints normally need to
11544 be placed at an instruction that is 5 bytes or longer, but can be
11545 placed at 4-byte instructions if the low 64K of memory of the target
11546 program is available to install trampolines. Some Unix-type systems,
11547 such as @sc{gnu}/Linux, exclude low addresses from the program's
11548 address space; but for instance with the Linux kernel it is possible
11549 to let @value{GDBN} use this area by doing a @command{sysctl} command
11550 to set the @code{mmap_min_addr} kernel parameter, as in
11553 sudo sysctl -w vm.mmap_min_addr=32768
11557 which sets the low address to 32K, which leaves plenty of room for
11558 trampolines. The minimum address should be set to a page boundary.
11560 @item strace @var{location} [ if @var{cond} ]
11561 @cindex set static tracepoint
11562 @cindex static tracepoints, setting
11563 @cindex probe static tracepoint marker
11565 The @code{strace} command sets a static tracepoint. For targets that
11566 support it, setting a static tracepoint probes a static
11567 instrumentation point, or marker, found at @var{location}. It may not
11568 be possible to set a static tracepoint at the desired location, in
11569 which case the command will exit with an explanatory message.
11571 @value{GDBN} handles arguments to @code{strace} exactly as for
11572 @code{trace}, with the addition that the user can also specify
11573 @code{-m @var{marker}} as @var{location}. This probes the marker
11574 identified by the @var{marker} string identifier. This identifier
11575 depends on the static tracepoint backend library your program is
11576 using. You can find all the marker identifiers in the @samp{ID} field
11577 of the @code{info static-tracepoint-markers} command output.
11578 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11579 Markers}. For example, in the following small program using the UST
11585 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11590 the marker id is composed of joining the first two arguments to the
11591 @code{trace_mark} call with a slash, which translates to:
11594 (@value{GDBP}) info static-tracepoint-markers
11595 Cnt Enb ID Address What
11596 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11602 so you may probe the marker above with:
11605 (@value{GDBP}) strace -m ust/bar33
11608 Static tracepoints accept an extra collect action --- @code{collect
11609 $_sdata}. This collects arbitrary user data passed in the probe point
11610 call to the tracing library. In the UST example above, you'll see
11611 that the third argument to @code{trace_mark} is a printf-like format
11612 string. The user data is then the result of running that formating
11613 string against the following arguments. Note that @code{info
11614 static-tracepoint-markers} command output lists that format string in
11615 the @samp{Data:} field.
11617 You can inspect this data when analyzing the trace buffer, by printing
11618 the $_sdata variable like any other variable available to
11619 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11622 @cindex last tracepoint number
11623 @cindex recent tracepoint number
11624 @cindex tracepoint number
11625 The convenience variable @code{$tpnum} records the tracepoint number
11626 of the most recently set tracepoint.
11628 @kindex delete tracepoint
11629 @cindex tracepoint deletion
11630 @item delete tracepoint @r{[}@var{num}@r{]}
11631 Permanently delete one or more tracepoints. With no argument, the
11632 default is to delete all tracepoints. Note that the regular
11633 @code{delete} command can remove tracepoints also.
11638 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11640 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11644 You can abbreviate this command as @code{del tr}.
11647 @node Enable and Disable Tracepoints
11648 @subsection Enable and Disable Tracepoints
11650 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11653 @kindex disable tracepoint
11654 @item disable tracepoint @r{[}@var{num}@r{]}
11655 Disable tracepoint @var{num}, or all tracepoints if no argument
11656 @var{num} is given. A disabled tracepoint will have no effect during
11657 a trace experiment, but it is not forgotten. You can re-enable
11658 a disabled tracepoint using the @code{enable tracepoint} command.
11659 If the command is issued during a trace experiment and the debug target
11660 has support for disabling tracepoints during a trace experiment, then the
11661 change will be effective immediately. Otherwise, it will be applied to the
11662 next trace experiment.
11664 @kindex enable tracepoint
11665 @item enable tracepoint @r{[}@var{num}@r{]}
11666 Enable tracepoint @var{num}, or all tracepoints. If this command is
11667 issued during a trace experiment and the debug target supports enabling
11668 tracepoints during a trace experiment, then the enabled tracepoints will
11669 become effective immediately. Otherwise, they will become effective the
11670 next time a trace experiment is run.
11673 @node Tracepoint Passcounts
11674 @subsection Tracepoint Passcounts
11678 @cindex tracepoint pass count
11679 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11680 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11681 automatically stop a trace experiment. If a tracepoint's passcount is
11682 @var{n}, then the trace experiment will be automatically stopped on
11683 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11684 @var{num} is not specified, the @code{passcount} command sets the
11685 passcount of the most recently defined tracepoint. If no passcount is
11686 given, the trace experiment will run until stopped explicitly by the
11692 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11693 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11695 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11696 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11697 (@value{GDBP}) @b{trace foo}
11698 (@value{GDBP}) @b{pass 3}
11699 (@value{GDBP}) @b{trace bar}
11700 (@value{GDBP}) @b{pass 2}
11701 (@value{GDBP}) @b{trace baz}
11702 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11703 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11704 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11705 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11709 @node Tracepoint Conditions
11710 @subsection Tracepoint Conditions
11711 @cindex conditional tracepoints
11712 @cindex tracepoint conditions
11714 The simplest sort of tracepoint collects data every time your program
11715 reaches a specified place. You can also specify a @dfn{condition} for
11716 a tracepoint. A condition is just a Boolean expression in your
11717 programming language (@pxref{Expressions, ,Expressions}). A
11718 tracepoint with a condition evaluates the expression each time your
11719 program reaches it, and data collection happens only if the condition
11722 Tracepoint conditions can be specified when a tracepoint is set, by
11723 using @samp{if} in the arguments to the @code{trace} command.
11724 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11725 also be set or changed at any time with the @code{condition} command,
11726 just as with breakpoints.
11728 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11729 the conditional expression itself. Instead, @value{GDBN} encodes the
11730 expression into an agent expression (@pxref{Agent Expressions})
11731 suitable for execution on the target, independently of @value{GDBN}.
11732 Global variables become raw memory locations, locals become stack
11733 accesses, and so forth.
11735 For instance, suppose you have a function that is usually called
11736 frequently, but should not be called after an error has occurred. You
11737 could use the following tracepoint command to collect data about calls
11738 of that function that happen while the error code is propagating
11739 through the program; an unconditional tracepoint could end up
11740 collecting thousands of useless trace frames that you would have to
11744 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11747 @node Trace State Variables
11748 @subsection Trace State Variables
11749 @cindex trace state variables
11751 A @dfn{trace state variable} is a special type of variable that is
11752 created and managed by target-side code. The syntax is the same as
11753 that for GDB's convenience variables (a string prefixed with ``$''),
11754 but they are stored on the target. They must be created explicitly,
11755 using a @code{tvariable} command. They are always 64-bit signed
11758 Trace state variables are remembered by @value{GDBN}, and downloaded
11759 to the target along with tracepoint information when the trace
11760 experiment starts. There are no intrinsic limits on the number of
11761 trace state variables, beyond memory limitations of the target.
11763 @cindex convenience variables, and trace state variables
11764 Although trace state variables are managed by the target, you can use
11765 them in print commands and expressions as if they were convenience
11766 variables; @value{GDBN} will get the current value from the target
11767 while the trace experiment is running. Trace state variables share
11768 the same namespace as other ``$'' variables, which means that you
11769 cannot have trace state variables with names like @code{$23} or
11770 @code{$pc}, nor can you have a trace state variable and a convenience
11771 variable with the same name.
11775 @item tvariable $@var{name} [ = @var{expression} ]
11777 The @code{tvariable} command creates a new trace state variable named
11778 @code{$@var{name}}, and optionally gives it an initial value of
11779 @var{expression}. @var{expression} is evaluated when this command is
11780 entered; the result will be converted to an integer if possible,
11781 otherwise @value{GDBN} will report an error. A subsequent
11782 @code{tvariable} command specifying the same name does not create a
11783 variable, but instead assigns the supplied initial value to the
11784 existing variable of that name, overwriting any previous initial
11785 value. The default initial value is 0.
11787 @item info tvariables
11788 @kindex info tvariables
11789 List all the trace state variables along with their initial values.
11790 Their current values may also be displayed, if the trace experiment is
11793 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11794 @kindex delete tvariable
11795 Delete the given trace state variables, or all of them if no arguments
11800 @node Tracepoint Actions
11801 @subsection Tracepoint Action Lists
11805 @cindex tracepoint actions
11806 @item actions @r{[}@var{num}@r{]}
11807 This command will prompt for a list of actions to be taken when the
11808 tracepoint is hit. If the tracepoint number @var{num} is not
11809 specified, this command sets the actions for the one that was most
11810 recently defined (so that you can define a tracepoint and then say
11811 @code{actions} without bothering about its number). You specify the
11812 actions themselves on the following lines, one action at a time, and
11813 terminate the actions list with a line containing just @code{end}. So
11814 far, the only defined actions are @code{collect}, @code{teval}, and
11815 @code{while-stepping}.
11817 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11818 Commands, ,Breakpoint Command Lists}), except that only the defined
11819 actions are allowed; any other @value{GDBN} command is rejected.
11821 @cindex remove actions from a tracepoint
11822 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11823 and follow it immediately with @samp{end}.
11826 (@value{GDBP}) @b{collect @var{data}} // collect some data
11828 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11830 (@value{GDBP}) @b{end} // signals the end of actions.
11833 In the following example, the action list begins with @code{collect}
11834 commands indicating the things to be collected when the tracepoint is
11835 hit. Then, in order to single-step and collect additional data
11836 following the tracepoint, a @code{while-stepping} command is used,
11837 followed by the list of things to be collected after each step in a
11838 sequence of single steps. The @code{while-stepping} command is
11839 terminated by its own separate @code{end} command. Lastly, the action
11840 list is terminated by an @code{end} command.
11843 (@value{GDBP}) @b{trace foo}
11844 (@value{GDBP}) @b{actions}
11845 Enter actions for tracepoint 1, one per line:
11848 > while-stepping 12
11849 > collect $pc, arr[i]
11854 @kindex collect @r{(tracepoints)}
11855 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11856 Collect values of the given expressions when the tracepoint is hit.
11857 This command accepts a comma-separated list of any valid expressions.
11858 In addition to global, static, or local variables, the following
11859 special arguments are supported:
11863 Collect all registers.
11866 Collect all function arguments.
11869 Collect all local variables.
11872 Collect the return address. This is helpful if you want to see more
11876 Collects the number of arguments from the static probe at which the
11877 tracepoint is located.
11878 @xref{Static Probe Points}.
11880 @item $_probe_arg@var{n}
11881 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11882 from the static probe at which the tracepoint is located.
11883 @xref{Static Probe Points}.
11886 @vindex $_sdata@r{, collect}
11887 Collect static tracepoint marker specific data. Only available for
11888 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11889 Lists}. On the UST static tracepoints library backend, an
11890 instrumentation point resembles a @code{printf} function call. The
11891 tracing library is able to collect user specified data formatted to a
11892 character string using the format provided by the programmer that
11893 instrumented the program. Other backends have similar mechanisms.
11894 Here's an example of a UST marker call:
11897 const char master_name[] = "$your_name";
11898 trace_mark(channel1, marker1, "hello %s", master_name)
11901 In this case, collecting @code{$_sdata} collects the string
11902 @samp{hello $yourname}. When analyzing the trace buffer, you can
11903 inspect @samp{$_sdata} like any other variable available to
11907 You can give several consecutive @code{collect} commands, each one
11908 with a single argument, or one @code{collect} command with several
11909 arguments separated by commas; the effect is the same.
11911 The optional @var{mods} changes the usual handling of the arguments.
11912 @code{s} requests that pointers to chars be handled as strings, in
11913 particular collecting the contents of the memory being pointed at, up
11914 to the first zero. The upper bound is by default the value of the
11915 @code{print elements} variable; if @code{s} is followed by a decimal
11916 number, that is the upper bound instead. So for instance
11917 @samp{collect/s25 mystr} collects as many as 25 characters at
11920 The command @code{info scope} (@pxref{Symbols, info scope}) is
11921 particularly useful for figuring out what data to collect.
11923 @kindex teval @r{(tracepoints)}
11924 @item teval @var{expr1}, @var{expr2}, @dots{}
11925 Evaluate the given expressions when the tracepoint is hit. This
11926 command accepts a comma-separated list of expressions. The results
11927 are discarded, so this is mainly useful for assigning values to trace
11928 state variables (@pxref{Trace State Variables}) without adding those
11929 values to the trace buffer, as would be the case if the @code{collect}
11932 @kindex while-stepping @r{(tracepoints)}
11933 @item while-stepping @var{n}
11934 Perform @var{n} single-step instruction traces after the tracepoint,
11935 collecting new data after each step. The @code{while-stepping}
11936 command is followed by the list of what to collect while stepping
11937 (followed by its own @code{end} command):
11940 > while-stepping 12
11941 > collect $regs, myglobal
11947 Note that @code{$pc} is not automatically collected by
11948 @code{while-stepping}; you need to explicitly collect that register if
11949 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11952 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11953 @kindex set default-collect
11954 @cindex default collection action
11955 This variable is a list of expressions to collect at each tracepoint
11956 hit. It is effectively an additional @code{collect} action prepended
11957 to every tracepoint action list. The expressions are parsed
11958 individually for each tracepoint, so for instance a variable named
11959 @code{xyz} may be interpreted as a global for one tracepoint, and a
11960 local for another, as appropriate to the tracepoint's location.
11962 @item show default-collect
11963 @kindex show default-collect
11964 Show the list of expressions that are collected by default at each
11969 @node Listing Tracepoints
11970 @subsection Listing Tracepoints
11973 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11974 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11975 @cindex information about tracepoints
11976 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11977 Display information about the tracepoint @var{num}. If you don't
11978 specify a tracepoint number, displays information about all the
11979 tracepoints defined so far. The format is similar to that used for
11980 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11981 command, simply restricting itself to tracepoints.
11983 A tracepoint's listing may include additional information specific to
11988 its passcount as given by the @code{passcount @var{n}} command
11991 the state about installed on target of each location
11995 (@value{GDBP}) @b{info trace}
11996 Num Type Disp Enb Address What
11997 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11999 collect globfoo, $regs
12004 2 tracepoint keep y <MULTIPLE>
12006 2.1 y 0x0804859c in func4 at change-loc.h:35
12007 installed on target
12008 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
12009 installed on target
12010 2.3 y <PENDING> set_tracepoint
12011 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
12012 not installed on target
12017 This command can be abbreviated @code{info tp}.
12020 @node Listing Static Tracepoint Markers
12021 @subsection Listing Static Tracepoint Markers
12024 @kindex info static-tracepoint-markers
12025 @cindex information about static tracepoint markers
12026 @item info static-tracepoint-markers
12027 Display information about all static tracepoint markers defined in the
12030 For each marker, the following columns are printed:
12034 An incrementing counter, output to help readability. This is not a
12037 The marker ID, as reported by the target.
12038 @item Enabled or Disabled
12039 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
12040 that are not enabled.
12042 Where the marker is in your program, as a memory address.
12044 Where the marker is in the source for your program, as a file and line
12045 number. If the debug information included in the program does not
12046 allow @value{GDBN} to locate the source of the marker, this column
12047 will be left blank.
12051 In addition, the following information may be printed for each marker:
12055 User data passed to the tracing library by the marker call. In the
12056 UST backend, this is the format string passed as argument to the
12058 @item Static tracepoints probing the marker
12059 The list of static tracepoints attached to the marker.
12063 (@value{GDBP}) info static-tracepoint-markers
12064 Cnt ID Enb Address What
12065 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
12066 Data: number1 %d number2 %d
12067 Probed by static tracepoints: #2
12068 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12074 @node Starting and Stopping Trace Experiments
12075 @subsection Starting and Stopping Trace Experiments
12078 @kindex tstart [ @var{notes} ]
12079 @cindex start a new trace experiment
12080 @cindex collected data discarded
12082 This command starts the trace experiment, and begins collecting data.
12083 It has the side effect of discarding all the data collected in the
12084 trace buffer during the previous trace experiment. If any arguments
12085 are supplied, they are taken as a note and stored with the trace
12086 experiment's state. The notes may be arbitrary text, and are
12087 especially useful with disconnected tracing in a multi-user context;
12088 the notes can explain what the trace is doing, supply user contact
12089 information, and so forth.
12091 @kindex tstop [ @var{notes} ]
12092 @cindex stop a running trace experiment
12094 This command stops the trace experiment. If any arguments are
12095 supplied, they are recorded with the experiment as a note. This is
12096 useful if you are stopping a trace started by someone else, for
12097 instance if the trace is interfering with the system's behavior and
12098 needs to be stopped quickly.
12100 @strong{Note}: a trace experiment and data collection may stop
12101 automatically if any tracepoint's passcount is reached
12102 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12105 @cindex status of trace data collection
12106 @cindex trace experiment, status of
12108 This command displays the status of the current trace data
12112 Here is an example of the commands we described so far:
12115 (@value{GDBP}) @b{trace gdb_c_test}
12116 (@value{GDBP}) @b{actions}
12117 Enter actions for tracepoint #1, one per line.
12118 > collect $regs,$locals,$args
12119 > while-stepping 11
12123 (@value{GDBP}) @b{tstart}
12124 [time passes @dots{}]
12125 (@value{GDBP}) @b{tstop}
12128 @anchor{disconnected tracing}
12129 @cindex disconnected tracing
12130 You can choose to continue running the trace experiment even if
12131 @value{GDBN} disconnects from the target, voluntarily or
12132 involuntarily. For commands such as @code{detach}, the debugger will
12133 ask what you want to do with the trace. But for unexpected
12134 terminations (@value{GDBN} crash, network outage), it would be
12135 unfortunate to lose hard-won trace data, so the variable
12136 @code{disconnected-tracing} lets you decide whether the trace should
12137 continue running without @value{GDBN}.
12140 @item set disconnected-tracing on
12141 @itemx set disconnected-tracing off
12142 @kindex set disconnected-tracing
12143 Choose whether a tracing run should continue to run if @value{GDBN}
12144 has disconnected from the target. Note that @code{detach} or
12145 @code{quit} will ask you directly what to do about a running trace no
12146 matter what this variable's setting, so the variable is mainly useful
12147 for handling unexpected situations, such as loss of the network.
12149 @item show disconnected-tracing
12150 @kindex show disconnected-tracing
12151 Show the current choice for disconnected tracing.
12155 When you reconnect to the target, the trace experiment may or may not
12156 still be running; it might have filled the trace buffer in the
12157 meantime, or stopped for one of the other reasons. If it is running,
12158 it will continue after reconnection.
12160 Upon reconnection, the target will upload information about the
12161 tracepoints in effect. @value{GDBN} will then compare that
12162 information to the set of tracepoints currently defined, and attempt
12163 to match them up, allowing for the possibility that the numbers may
12164 have changed due to creation and deletion in the meantime. If one of
12165 the target's tracepoints does not match any in @value{GDBN}, the
12166 debugger will create a new tracepoint, so that you have a number with
12167 which to specify that tracepoint. This matching-up process is
12168 necessarily heuristic, and it may result in useless tracepoints being
12169 created; you may simply delete them if they are of no use.
12171 @cindex circular trace buffer
12172 If your target agent supports a @dfn{circular trace buffer}, then you
12173 can run a trace experiment indefinitely without filling the trace
12174 buffer; when space runs out, the agent deletes already-collected trace
12175 frames, oldest first, until there is enough room to continue
12176 collecting. This is especially useful if your tracepoints are being
12177 hit too often, and your trace gets terminated prematurely because the
12178 buffer is full. To ask for a circular trace buffer, simply set
12179 @samp{circular-trace-buffer} to on. You can set this at any time,
12180 including during tracing; if the agent can do it, it will change
12181 buffer handling on the fly, otherwise it will not take effect until
12185 @item set circular-trace-buffer on
12186 @itemx set circular-trace-buffer off
12187 @kindex set circular-trace-buffer
12188 Choose whether a tracing run should use a linear or circular buffer
12189 for trace data. A linear buffer will not lose any trace data, but may
12190 fill up prematurely, while a circular buffer will discard old trace
12191 data, but it will have always room for the latest tracepoint hits.
12193 @item show circular-trace-buffer
12194 @kindex show circular-trace-buffer
12195 Show the current choice for the trace buffer. Note that this may not
12196 match the agent's current buffer handling, nor is it guaranteed to
12197 match the setting that might have been in effect during a past run,
12198 for instance if you are looking at frames from a trace file.
12203 @item set trace-buffer-size @var{n}
12204 @itemx set trace-buffer-size unlimited
12205 @kindex set trace-buffer-size
12206 Request that the target use a trace buffer of @var{n} bytes. Not all
12207 targets will honor the request; they may have a compiled-in size for
12208 the trace buffer, or some other limitation. Set to a value of
12209 @code{unlimited} or @code{-1} to let the target use whatever size it
12210 likes. This is also the default.
12212 @item show trace-buffer-size
12213 @kindex show trace-buffer-size
12214 Show the current requested size for the trace buffer. Note that this
12215 will only match the actual size if the target supports size-setting,
12216 and was able to handle the requested size. For instance, if the
12217 target can only change buffer size between runs, this variable will
12218 not reflect the change until the next run starts. Use @code{tstatus}
12219 to get a report of the actual buffer size.
12223 @item set trace-user @var{text}
12224 @kindex set trace-user
12226 @item show trace-user
12227 @kindex show trace-user
12229 @item set trace-notes @var{text}
12230 @kindex set trace-notes
12231 Set the trace run's notes.
12233 @item show trace-notes
12234 @kindex show trace-notes
12235 Show the trace run's notes.
12237 @item set trace-stop-notes @var{text}
12238 @kindex set trace-stop-notes
12239 Set the trace run's stop notes. The handling of the note is as for
12240 @code{tstop} arguments; the set command is convenient way to fix a
12241 stop note that is mistaken or incomplete.
12243 @item show trace-stop-notes
12244 @kindex show trace-stop-notes
12245 Show the trace run's stop notes.
12249 @node Tracepoint Restrictions
12250 @subsection Tracepoint Restrictions
12252 @cindex tracepoint restrictions
12253 There are a number of restrictions on the use of tracepoints. As
12254 described above, tracepoint data gathering occurs on the target
12255 without interaction from @value{GDBN}. Thus the full capabilities of
12256 the debugger are not available during data gathering, and then at data
12257 examination time, you will be limited by only having what was
12258 collected. The following items describe some common problems, but it
12259 is not exhaustive, and you may run into additional difficulties not
12265 Tracepoint expressions are intended to gather objects (lvalues). Thus
12266 the full flexibility of GDB's expression evaluator is not available.
12267 You cannot call functions, cast objects to aggregate types, access
12268 convenience variables or modify values (except by assignment to trace
12269 state variables). Some language features may implicitly call
12270 functions (for instance Objective-C fields with accessors), and therefore
12271 cannot be collected either.
12274 Collection of local variables, either individually or in bulk with
12275 @code{$locals} or @code{$args}, during @code{while-stepping} may
12276 behave erratically. The stepping action may enter a new scope (for
12277 instance by stepping into a function), or the location of the variable
12278 may change (for instance it is loaded into a register). The
12279 tracepoint data recorded uses the location information for the
12280 variables that is correct for the tracepoint location. When the
12281 tracepoint is created, it is not possible, in general, to determine
12282 where the steps of a @code{while-stepping} sequence will advance the
12283 program---particularly if a conditional branch is stepped.
12286 Collection of an incompletely-initialized or partially-destroyed object
12287 may result in something that @value{GDBN} cannot display, or displays
12288 in a misleading way.
12291 When @value{GDBN} displays a pointer to character it automatically
12292 dereferences the pointer to also display characters of the string
12293 being pointed to. However, collecting the pointer during tracing does
12294 not automatically collect the string. You need to explicitly
12295 dereference the pointer and provide size information if you want to
12296 collect not only the pointer, but the memory pointed to. For example,
12297 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12301 It is not possible to collect a complete stack backtrace at a
12302 tracepoint. Instead, you may collect the registers and a few hundred
12303 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12304 (adjust to use the name of the actual stack pointer register on your
12305 target architecture, and the amount of stack you wish to capture).
12306 Then the @code{backtrace} command will show a partial backtrace when
12307 using a trace frame. The number of stack frames that can be examined
12308 depends on the sizes of the frames in the collected stack. Note that
12309 if you ask for a block so large that it goes past the bottom of the
12310 stack, the target agent may report an error trying to read from an
12314 If you do not collect registers at a tracepoint, @value{GDBN} can
12315 infer that the value of @code{$pc} must be the same as the address of
12316 the tracepoint and use that when you are looking at a trace frame
12317 for that tracepoint. However, this cannot work if the tracepoint has
12318 multiple locations (for instance if it was set in a function that was
12319 inlined), or if it has a @code{while-stepping} loop. In those cases
12320 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12325 @node Analyze Collected Data
12326 @section Using the Collected Data
12328 After the tracepoint experiment ends, you use @value{GDBN} commands
12329 for examining the trace data. The basic idea is that each tracepoint
12330 collects a trace @dfn{snapshot} every time it is hit and another
12331 snapshot every time it single-steps. All these snapshots are
12332 consecutively numbered from zero and go into a buffer, and you can
12333 examine them later. The way you examine them is to @dfn{focus} on a
12334 specific trace snapshot. When the remote stub is focused on a trace
12335 snapshot, it will respond to all @value{GDBN} requests for memory and
12336 registers by reading from the buffer which belongs to that snapshot,
12337 rather than from @emph{real} memory or registers of the program being
12338 debugged. This means that @strong{all} @value{GDBN} commands
12339 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12340 behave as if we were currently debugging the program state as it was
12341 when the tracepoint occurred. Any requests for data that are not in
12342 the buffer will fail.
12345 * tfind:: How to select a trace snapshot
12346 * tdump:: How to display all data for a snapshot
12347 * save tracepoints:: How to save tracepoints for a future run
12351 @subsection @code{tfind @var{n}}
12354 @cindex select trace snapshot
12355 @cindex find trace snapshot
12356 The basic command for selecting a trace snapshot from the buffer is
12357 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12358 counting from zero. If no argument @var{n} is given, the next
12359 snapshot is selected.
12361 Here are the various forms of using the @code{tfind} command.
12365 Find the first snapshot in the buffer. This is a synonym for
12366 @code{tfind 0} (since 0 is the number of the first snapshot).
12369 Stop debugging trace snapshots, resume @emph{live} debugging.
12372 Same as @samp{tfind none}.
12375 No argument means find the next trace snapshot.
12378 Find the previous trace snapshot before the current one. This permits
12379 retracing earlier steps.
12381 @item tfind tracepoint @var{num}
12382 Find the next snapshot associated with tracepoint @var{num}. Search
12383 proceeds forward from the last examined trace snapshot. If no
12384 argument @var{num} is given, it means find the next snapshot collected
12385 for the same tracepoint as the current snapshot.
12387 @item tfind pc @var{addr}
12388 Find the next snapshot associated with the value @var{addr} of the
12389 program counter. Search proceeds forward from the last examined trace
12390 snapshot. If no argument @var{addr} is given, it means find the next
12391 snapshot with the same value of PC as the current snapshot.
12393 @item tfind outside @var{addr1}, @var{addr2}
12394 Find the next snapshot whose PC is outside the given range of
12395 addresses (exclusive).
12397 @item tfind range @var{addr1}, @var{addr2}
12398 Find the next snapshot whose PC is between @var{addr1} and
12399 @var{addr2} (inclusive).
12401 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12402 Find the next snapshot associated with the source line @var{n}. If
12403 the optional argument @var{file} is given, refer to line @var{n} in
12404 that source file. Search proceeds forward from the last examined
12405 trace snapshot. If no argument @var{n} is given, it means find the
12406 next line other than the one currently being examined; thus saying
12407 @code{tfind line} repeatedly can appear to have the same effect as
12408 stepping from line to line in a @emph{live} debugging session.
12411 The default arguments for the @code{tfind} commands are specifically
12412 designed to make it easy to scan through the trace buffer. For
12413 instance, @code{tfind} with no argument selects the next trace
12414 snapshot, and @code{tfind -} with no argument selects the previous
12415 trace snapshot. So, by giving one @code{tfind} command, and then
12416 simply hitting @key{RET} repeatedly you can examine all the trace
12417 snapshots in order. Or, by saying @code{tfind -} and then hitting
12418 @key{RET} repeatedly you can examine the snapshots in reverse order.
12419 The @code{tfind line} command with no argument selects the snapshot
12420 for the next source line executed. The @code{tfind pc} command with
12421 no argument selects the next snapshot with the same program counter
12422 (PC) as the current frame. The @code{tfind tracepoint} command with
12423 no argument selects the next trace snapshot collected by the same
12424 tracepoint as the current one.
12426 In addition to letting you scan through the trace buffer manually,
12427 these commands make it easy to construct @value{GDBN} scripts that
12428 scan through the trace buffer and print out whatever collected data
12429 you are interested in. Thus, if we want to examine the PC, FP, and SP
12430 registers from each trace frame in the buffer, we can say this:
12433 (@value{GDBP}) @b{tfind start}
12434 (@value{GDBP}) @b{while ($trace_frame != -1)}
12435 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12436 $trace_frame, $pc, $sp, $fp
12440 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12441 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12442 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12443 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12444 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12445 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12446 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12447 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12448 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12449 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12450 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12453 Or, if we want to examine the variable @code{X} at each source line in
12457 (@value{GDBP}) @b{tfind start}
12458 (@value{GDBP}) @b{while ($trace_frame != -1)}
12459 > printf "Frame %d, X == %d\n", $trace_frame, X
12469 @subsection @code{tdump}
12471 @cindex dump all data collected at tracepoint
12472 @cindex tracepoint data, display
12474 This command takes no arguments. It prints all the data collected at
12475 the current trace snapshot.
12478 (@value{GDBP}) @b{trace 444}
12479 (@value{GDBP}) @b{actions}
12480 Enter actions for tracepoint #2, one per line:
12481 > collect $regs, $locals, $args, gdb_long_test
12484 (@value{GDBP}) @b{tstart}
12486 (@value{GDBP}) @b{tfind line 444}
12487 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12489 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12491 (@value{GDBP}) @b{tdump}
12492 Data collected at tracepoint 2, trace frame 1:
12493 d0 0xc4aa0085 -995491707
12497 d4 0x71aea3d 119204413
12500 d7 0x380035 3670069
12501 a0 0x19e24a 1696330
12502 a1 0x3000668 50333288
12504 a3 0x322000 3284992
12505 a4 0x3000698 50333336
12506 a5 0x1ad3cc 1758156
12507 fp 0x30bf3c 0x30bf3c
12508 sp 0x30bf34 0x30bf34
12510 pc 0x20b2c8 0x20b2c8
12514 p = 0x20e5b4 "gdb-test"
12521 gdb_long_test = 17 '\021'
12526 @code{tdump} works by scanning the tracepoint's current collection
12527 actions and printing the value of each expression listed. So
12528 @code{tdump} can fail, if after a run, you change the tracepoint's
12529 actions to mention variables that were not collected during the run.
12531 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12532 uses the collected value of @code{$pc} to distinguish between trace
12533 frames that were collected at the tracepoint hit, and frames that were
12534 collected while stepping. This allows it to correctly choose whether
12535 to display the basic list of collections, or the collections from the
12536 body of the while-stepping loop. However, if @code{$pc} was not collected,
12537 then @code{tdump} will always attempt to dump using the basic collection
12538 list, and may fail if a while-stepping frame does not include all the
12539 same data that is collected at the tracepoint hit.
12540 @c This is getting pretty arcane, example would be good.
12542 @node save tracepoints
12543 @subsection @code{save tracepoints @var{filename}}
12544 @kindex save tracepoints
12545 @kindex save-tracepoints
12546 @cindex save tracepoints for future sessions
12548 This command saves all current tracepoint definitions together with
12549 their actions and passcounts, into a file @file{@var{filename}}
12550 suitable for use in a later debugging session. To read the saved
12551 tracepoint definitions, use the @code{source} command (@pxref{Command
12552 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12553 alias for @w{@code{save tracepoints}}
12555 @node Tracepoint Variables
12556 @section Convenience Variables for Tracepoints
12557 @cindex tracepoint variables
12558 @cindex convenience variables for tracepoints
12561 @vindex $trace_frame
12562 @item (int) $trace_frame
12563 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12564 snapshot is selected.
12566 @vindex $tracepoint
12567 @item (int) $tracepoint
12568 The tracepoint for the current trace snapshot.
12570 @vindex $trace_line
12571 @item (int) $trace_line
12572 The line number for the current trace snapshot.
12574 @vindex $trace_file
12575 @item (char []) $trace_file
12576 The source file for the current trace snapshot.
12578 @vindex $trace_func
12579 @item (char []) $trace_func
12580 The name of the function containing @code{$tracepoint}.
12583 Note: @code{$trace_file} is not suitable for use in @code{printf},
12584 use @code{output} instead.
12586 Here's a simple example of using these convenience variables for
12587 stepping through all the trace snapshots and printing some of their
12588 data. Note that these are not the same as trace state variables,
12589 which are managed by the target.
12592 (@value{GDBP}) @b{tfind start}
12594 (@value{GDBP}) @b{while $trace_frame != -1}
12595 > output $trace_file
12596 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12602 @section Using Trace Files
12603 @cindex trace files
12605 In some situations, the target running a trace experiment may no
12606 longer be available; perhaps it crashed, or the hardware was needed
12607 for a different activity. To handle these cases, you can arrange to
12608 dump the trace data into a file, and later use that file as a source
12609 of trace data, via the @code{target tfile} command.
12614 @item tsave [ -r ] @var{filename}
12615 @itemx tsave [-ctf] @var{dirname}
12616 Save the trace data to @var{filename}. By default, this command
12617 assumes that @var{filename} refers to the host filesystem, so if
12618 necessary @value{GDBN} will copy raw trace data up from the target and
12619 then save it. If the target supports it, you can also supply the
12620 optional argument @code{-r} (``remote'') to direct the target to save
12621 the data directly into @var{filename} in its own filesystem, which may be
12622 more efficient if the trace buffer is very large. (Note, however, that
12623 @code{target tfile} can only read from files accessible to the host.)
12624 By default, this command will save trace frame in tfile format.
12625 You can supply the optional argument @code{-ctf} to save date in CTF
12626 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12627 that can be shared by multiple debugging and tracing tools. Please go to
12628 @indicateurl{http://www.efficios.com/ctf} to get more information.
12630 @kindex target tfile
12634 @item target tfile @var{filename}
12635 @itemx target ctf @var{dirname}
12636 Use the file named @var{filename} or directory named @var{dirname} as
12637 a source of trace data. Commands that examine data work as they do with
12638 a live target, but it is not possible to run any new trace experiments.
12639 @code{tstatus} will report the state of the trace run at the moment
12640 the data was saved, as well as the current trace frame you are examining.
12641 @var{filename} or @var{dirname} must be on a filesystem accessible to
12645 (@value{GDBP}) target ctf ctf.ctf
12646 (@value{GDBP}) tfind
12647 Found trace frame 0, tracepoint 2
12648 39 ++a; /* set tracepoint 1 here */
12649 (@value{GDBP}) tdump
12650 Data collected at tracepoint 2, trace frame 0:
12654 c = @{"123", "456", "789", "123", "456", "789"@}
12655 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12663 @chapter Debugging Programs That Use Overlays
12666 If your program is too large to fit completely in your target system's
12667 memory, you can sometimes use @dfn{overlays} to work around this
12668 problem. @value{GDBN} provides some support for debugging programs that
12672 * How Overlays Work:: A general explanation of overlays.
12673 * Overlay Commands:: Managing overlays in @value{GDBN}.
12674 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12675 mapped by asking the inferior.
12676 * Overlay Sample Program:: A sample program using overlays.
12679 @node How Overlays Work
12680 @section How Overlays Work
12681 @cindex mapped overlays
12682 @cindex unmapped overlays
12683 @cindex load address, overlay's
12684 @cindex mapped address
12685 @cindex overlay area
12687 Suppose you have a computer whose instruction address space is only 64
12688 kilobytes long, but which has much more memory which can be accessed by
12689 other means: special instructions, segment registers, or memory
12690 management hardware, for example. Suppose further that you want to
12691 adapt a program which is larger than 64 kilobytes to run on this system.
12693 One solution is to identify modules of your program which are relatively
12694 independent, and need not call each other directly; call these modules
12695 @dfn{overlays}. Separate the overlays from the main program, and place
12696 their machine code in the larger memory. Place your main program in
12697 instruction memory, but leave at least enough space there to hold the
12698 largest overlay as well.
12700 Now, to call a function located in an overlay, you must first copy that
12701 overlay's machine code from the large memory into the space set aside
12702 for it in the instruction memory, and then jump to its entry point
12705 @c NB: In the below the mapped area's size is greater or equal to the
12706 @c size of all overlays. This is intentional to remind the developer
12707 @c that overlays don't necessarily need to be the same size.
12711 Data Instruction Larger
12712 Address Space Address Space Address Space
12713 +-----------+ +-----------+ +-----------+
12715 +-----------+ +-----------+ +-----------+<-- overlay 1
12716 | program | | main | .----| overlay 1 | load address
12717 | variables | | program | | +-----------+
12718 | and heap | | | | | |
12719 +-----------+ | | | +-----------+<-- overlay 2
12720 | | +-----------+ | | | load address
12721 +-----------+ | | | .-| overlay 2 |
12723 mapped --->+-----------+ | | +-----------+
12724 address | | | | | |
12725 | overlay | <-' | | |
12726 | area | <---' +-----------+<-- overlay 3
12727 | | <---. | | load address
12728 +-----------+ `--| overlay 3 |
12735 @anchor{A code overlay}A code overlay
12739 The diagram (@pxref{A code overlay}) shows a system with separate data
12740 and instruction address spaces. To map an overlay, the program copies
12741 its code from the larger address space to the instruction address space.
12742 Since the overlays shown here all use the same mapped address, only one
12743 may be mapped at a time. For a system with a single address space for
12744 data and instructions, the diagram would be similar, except that the
12745 program variables and heap would share an address space with the main
12746 program and the overlay area.
12748 An overlay loaded into instruction memory and ready for use is called a
12749 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12750 instruction memory. An overlay not present (or only partially present)
12751 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12752 is its address in the larger memory. The mapped address is also called
12753 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12754 called the @dfn{load memory address}, or @dfn{LMA}.
12756 Unfortunately, overlays are not a completely transparent way to adapt a
12757 program to limited instruction memory. They introduce a new set of
12758 global constraints you must keep in mind as you design your program:
12763 Before calling or returning to a function in an overlay, your program
12764 must make sure that overlay is actually mapped. Otherwise, the call or
12765 return will transfer control to the right address, but in the wrong
12766 overlay, and your program will probably crash.
12769 If the process of mapping an overlay is expensive on your system, you
12770 will need to choose your overlays carefully to minimize their effect on
12771 your program's performance.
12774 The executable file you load onto your system must contain each
12775 overlay's instructions, appearing at the overlay's load address, not its
12776 mapped address. However, each overlay's instructions must be relocated
12777 and its symbols defined as if the overlay were at its mapped address.
12778 You can use GNU linker scripts to specify different load and relocation
12779 addresses for pieces of your program; see @ref{Overlay Description,,,
12780 ld.info, Using ld: the GNU linker}.
12783 The procedure for loading executable files onto your system must be able
12784 to load their contents into the larger address space as well as the
12785 instruction and data spaces.
12789 The overlay system described above is rather simple, and could be
12790 improved in many ways:
12795 If your system has suitable bank switch registers or memory management
12796 hardware, you could use those facilities to make an overlay's load area
12797 contents simply appear at their mapped address in instruction space.
12798 This would probably be faster than copying the overlay to its mapped
12799 area in the usual way.
12802 If your overlays are small enough, you could set aside more than one
12803 overlay area, and have more than one overlay mapped at a time.
12806 You can use overlays to manage data, as well as instructions. In
12807 general, data overlays are even less transparent to your design than
12808 code overlays: whereas code overlays only require care when you call or
12809 return to functions, data overlays require care every time you access
12810 the data. Also, if you change the contents of a data overlay, you
12811 must copy its contents back out to its load address before you can copy a
12812 different data overlay into the same mapped area.
12817 @node Overlay Commands
12818 @section Overlay Commands
12820 To use @value{GDBN}'s overlay support, each overlay in your program must
12821 correspond to a separate section of the executable file. The section's
12822 virtual memory address and load memory address must be the overlay's
12823 mapped and load addresses. Identifying overlays with sections allows
12824 @value{GDBN} to determine the appropriate address of a function or
12825 variable, depending on whether the overlay is mapped or not.
12827 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12828 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12833 Disable @value{GDBN}'s overlay support. When overlay support is
12834 disabled, @value{GDBN} assumes that all functions and variables are
12835 always present at their mapped addresses. By default, @value{GDBN}'s
12836 overlay support is disabled.
12838 @item overlay manual
12839 @cindex manual overlay debugging
12840 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12841 relies on you to tell it which overlays are mapped, and which are not,
12842 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12843 commands described below.
12845 @item overlay map-overlay @var{overlay}
12846 @itemx overlay map @var{overlay}
12847 @cindex map an overlay
12848 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12849 be the name of the object file section containing the overlay. When an
12850 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12851 functions and variables at their mapped addresses. @value{GDBN} assumes
12852 that any other overlays whose mapped ranges overlap that of
12853 @var{overlay} are now unmapped.
12855 @item overlay unmap-overlay @var{overlay}
12856 @itemx overlay unmap @var{overlay}
12857 @cindex unmap an overlay
12858 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12859 must be the name of the object file section containing the overlay.
12860 When an overlay is unmapped, @value{GDBN} assumes it can find the
12861 overlay's functions and variables at their load addresses.
12864 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12865 consults a data structure the overlay manager maintains in the inferior
12866 to see which overlays are mapped. For details, see @ref{Automatic
12867 Overlay Debugging}.
12869 @item overlay load-target
12870 @itemx overlay load
12871 @cindex reloading the overlay table
12872 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12873 re-reads the table @value{GDBN} automatically each time the inferior
12874 stops, so this command should only be necessary if you have changed the
12875 overlay mapping yourself using @value{GDBN}. This command is only
12876 useful when using automatic overlay debugging.
12878 @item overlay list-overlays
12879 @itemx overlay list
12880 @cindex listing mapped overlays
12881 Display a list of the overlays currently mapped, along with their mapped
12882 addresses, load addresses, and sizes.
12886 Normally, when @value{GDBN} prints a code address, it includes the name
12887 of the function the address falls in:
12890 (@value{GDBP}) print main
12891 $3 = @{int ()@} 0x11a0 <main>
12894 When overlay debugging is enabled, @value{GDBN} recognizes code in
12895 unmapped overlays, and prints the names of unmapped functions with
12896 asterisks around them. For example, if @code{foo} is a function in an
12897 unmapped overlay, @value{GDBN} prints it this way:
12900 (@value{GDBP}) overlay list
12901 No sections are mapped.
12902 (@value{GDBP}) print foo
12903 $5 = @{int (int)@} 0x100000 <*foo*>
12906 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12910 (@value{GDBP}) overlay list
12911 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12912 mapped at 0x1016 - 0x104a
12913 (@value{GDBP}) print foo
12914 $6 = @{int (int)@} 0x1016 <foo>
12917 When overlay debugging is enabled, @value{GDBN} can find the correct
12918 address for functions and variables in an overlay, whether or not the
12919 overlay is mapped. This allows most @value{GDBN} commands, like
12920 @code{break} and @code{disassemble}, to work normally, even on unmapped
12921 code. However, @value{GDBN}'s breakpoint support has some limitations:
12925 @cindex breakpoints in overlays
12926 @cindex overlays, setting breakpoints in
12927 You can set breakpoints in functions in unmapped overlays, as long as
12928 @value{GDBN} can write to the overlay at its load address.
12930 @value{GDBN} can not set hardware or simulator-based breakpoints in
12931 unmapped overlays. However, if you set a breakpoint at the end of your
12932 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12933 you are using manual overlay management), @value{GDBN} will re-set its
12934 breakpoints properly.
12938 @node Automatic Overlay Debugging
12939 @section Automatic Overlay Debugging
12940 @cindex automatic overlay debugging
12942 @value{GDBN} can automatically track which overlays are mapped and which
12943 are not, given some simple co-operation from the overlay manager in the
12944 inferior. If you enable automatic overlay debugging with the
12945 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12946 looks in the inferior's memory for certain variables describing the
12947 current state of the overlays.
12949 Here are the variables your overlay manager must define to support
12950 @value{GDBN}'s automatic overlay debugging:
12954 @item @code{_ovly_table}:
12955 This variable must be an array of the following structures:
12960 /* The overlay's mapped address. */
12963 /* The size of the overlay, in bytes. */
12964 unsigned long size;
12966 /* The overlay's load address. */
12969 /* Non-zero if the overlay is currently mapped;
12971 unsigned long mapped;
12975 @item @code{_novlys}:
12976 This variable must be a four-byte signed integer, holding the total
12977 number of elements in @code{_ovly_table}.
12981 To decide whether a particular overlay is mapped or not, @value{GDBN}
12982 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12983 @code{lma} members equal the VMA and LMA of the overlay's section in the
12984 executable file. When @value{GDBN} finds a matching entry, it consults
12985 the entry's @code{mapped} member to determine whether the overlay is
12988 In addition, your overlay manager may define a function called
12989 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12990 will silently set a breakpoint there. If the overlay manager then
12991 calls this function whenever it has changed the overlay table, this
12992 will enable @value{GDBN} to accurately keep track of which overlays
12993 are in program memory, and update any breakpoints that may be set
12994 in overlays. This will allow breakpoints to work even if the
12995 overlays are kept in ROM or other non-writable memory while they
12996 are not being executed.
12998 @node Overlay Sample Program
12999 @section Overlay Sample Program
13000 @cindex overlay example program
13002 When linking a program which uses overlays, you must place the overlays
13003 at their load addresses, while relocating them to run at their mapped
13004 addresses. To do this, you must write a linker script (@pxref{Overlay
13005 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
13006 since linker scripts are specific to a particular host system, target
13007 architecture, and target memory layout, this manual cannot provide
13008 portable sample code demonstrating @value{GDBN}'s overlay support.
13010 However, the @value{GDBN} source distribution does contain an overlaid
13011 program, with linker scripts for a few systems, as part of its test
13012 suite. The program consists of the following files from
13013 @file{gdb/testsuite/gdb.base}:
13017 The main program file.
13019 A simple overlay manager, used by @file{overlays.c}.
13024 Overlay modules, loaded and used by @file{overlays.c}.
13027 Linker scripts for linking the test program on the @code{d10v-elf}
13028 and @code{m32r-elf} targets.
13031 You can build the test program using the @code{d10v-elf} GCC
13032 cross-compiler like this:
13035 $ d10v-elf-gcc -g -c overlays.c
13036 $ d10v-elf-gcc -g -c ovlymgr.c
13037 $ d10v-elf-gcc -g -c foo.c
13038 $ d10v-elf-gcc -g -c bar.c
13039 $ d10v-elf-gcc -g -c baz.c
13040 $ d10v-elf-gcc -g -c grbx.c
13041 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
13042 baz.o grbx.o -Wl,-Td10v.ld -o overlays
13045 The build process is identical for any other architecture, except that
13046 you must substitute the appropriate compiler and linker script for the
13047 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
13051 @chapter Using @value{GDBN} with Different Languages
13054 Although programming languages generally have common aspects, they are
13055 rarely expressed in the same manner. For instance, in ANSI C,
13056 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
13057 Modula-2, it is accomplished by @code{p^}. Values can also be
13058 represented (and displayed) differently. Hex numbers in C appear as
13059 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
13061 @cindex working language
13062 Language-specific information is built into @value{GDBN} for some languages,
13063 allowing you to express operations like the above in your program's
13064 native language, and allowing @value{GDBN} to output values in a manner
13065 consistent with the syntax of your program's native language. The
13066 language you use to build expressions is called the @dfn{working
13070 * Setting:: Switching between source languages
13071 * Show:: Displaying the language
13072 * Checks:: Type and range checks
13073 * Supported Languages:: Supported languages
13074 * Unsupported Languages:: Unsupported languages
13078 @section Switching Between Source Languages
13080 There are two ways to control the working language---either have @value{GDBN}
13081 set it automatically, or select it manually yourself. You can use the
13082 @code{set language} command for either purpose. On startup, @value{GDBN}
13083 defaults to setting the language automatically. The working language is
13084 used to determine how expressions you type are interpreted, how values
13087 In addition to the working language, every source file that
13088 @value{GDBN} knows about has its own working language. For some object
13089 file formats, the compiler might indicate which language a particular
13090 source file is in. However, most of the time @value{GDBN} infers the
13091 language from the name of the file. The language of a source file
13092 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13093 show each frame appropriately for its own language. There is no way to
13094 set the language of a source file from within @value{GDBN}, but you can
13095 set the language associated with a filename extension. @xref{Show, ,
13096 Displaying the Language}.
13098 This is most commonly a problem when you use a program, such
13099 as @code{cfront} or @code{f2c}, that generates C but is written in
13100 another language. In that case, make the
13101 program use @code{#line} directives in its C output; that way
13102 @value{GDBN} will know the correct language of the source code of the original
13103 program, and will display that source code, not the generated C code.
13106 * Filenames:: Filename extensions and languages.
13107 * Manually:: Setting the working language manually
13108 * Automatically:: Having @value{GDBN} infer the source language
13112 @subsection List of Filename Extensions and Languages
13114 If a source file name ends in one of the following extensions, then
13115 @value{GDBN} infers that its language is the one indicated.
13133 C@t{++} source file
13139 Objective-C source file
13143 Fortran source file
13146 Modula-2 source file
13150 Assembler source file. This actually behaves almost like C, but
13151 @value{GDBN} does not skip over function prologues when stepping.
13154 In addition, you may set the language associated with a filename
13155 extension. @xref{Show, , Displaying the Language}.
13158 @subsection Setting the Working Language
13160 If you allow @value{GDBN} to set the language automatically,
13161 expressions are interpreted the same way in your debugging session and
13164 @kindex set language
13165 If you wish, you may set the language manually. To do this, issue the
13166 command @samp{set language @var{lang}}, where @var{lang} is the name of
13167 a language, such as
13168 @code{c} or @code{modula-2}.
13169 For a list of the supported languages, type @samp{set language}.
13171 Setting the language manually prevents @value{GDBN} from updating the working
13172 language automatically. This can lead to confusion if you try
13173 to debug a program when the working language is not the same as the
13174 source language, when an expression is acceptable to both
13175 languages---but means different things. For instance, if the current
13176 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13184 might not have the effect you intended. In C, this means to add
13185 @code{b} and @code{c} and place the result in @code{a}. The result
13186 printed would be the value of @code{a}. In Modula-2, this means to compare
13187 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13189 @node Automatically
13190 @subsection Having @value{GDBN} Infer the Source Language
13192 To have @value{GDBN} set the working language automatically, use
13193 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13194 then infers the working language. That is, when your program stops in a
13195 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13196 working language to the language recorded for the function in that
13197 frame. If the language for a frame is unknown (that is, if the function
13198 or block corresponding to the frame was defined in a source file that
13199 does not have a recognized extension), the current working language is
13200 not changed, and @value{GDBN} issues a warning.
13202 This may not seem necessary for most programs, which are written
13203 entirely in one source language. However, program modules and libraries
13204 written in one source language can be used by a main program written in
13205 a different source language. Using @samp{set language auto} in this
13206 case frees you from having to set the working language manually.
13209 @section Displaying the Language
13211 The following commands help you find out which language is the
13212 working language, and also what language source files were written in.
13215 @item show language
13216 @kindex show language
13217 Display the current working language. This is the
13218 language you can use with commands such as @code{print} to
13219 build and compute expressions that may involve variables in your program.
13222 @kindex info frame@r{, show the source language}
13223 Display the source language for this frame. This language becomes the
13224 working language if you use an identifier from this frame.
13225 @xref{Frame Info, ,Information about a Frame}, to identify the other
13226 information listed here.
13229 @kindex info source@r{, show the source language}
13230 Display the source language of this source file.
13231 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13232 information listed here.
13235 In unusual circumstances, you may have source files with extensions
13236 not in the standard list. You can then set the extension associated
13237 with a language explicitly:
13240 @item set extension-language @var{ext} @var{language}
13241 @kindex set extension-language
13242 Tell @value{GDBN} that source files with extension @var{ext} are to be
13243 assumed as written in the source language @var{language}.
13245 @item info extensions
13246 @kindex info extensions
13247 List all the filename extensions and the associated languages.
13251 @section Type and Range Checking
13253 Some languages are designed to guard you against making seemingly common
13254 errors through a series of compile- and run-time checks. These include
13255 checking the type of arguments to functions and operators and making
13256 sure mathematical overflows are caught at run time. Checks such as
13257 these help to ensure a program's correctness once it has been compiled
13258 by eliminating type mismatches and providing active checks for range
13259 errors when your program is running.
13261 By default @value{GDBN} checks for these errors according to the
13262 rules of the current source language. Although @value{GDBN} does not check
13263 the statements in your program, it can check expressions entered directly
13264 into @value{GDBN} for evaluation via the @code{print} command, for example.
13267 * Type Checking:: An overview of type checking
13268 * Range Checking:: An overview of range checking
13271 @cindex type checking
13272 @cindex checks, type
13273 @node Type Checking
13274 @subsection An Overview of Type Checking
13276 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13277 arguments to operators and functions have to be of the correct type,
13278 otherwise an error occurs. These checks prevent type mismatch
13279 errors from ever causing any run-time problems. For example,
13282 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13284 (@value{GDBP}) print obj.my_method (0)
13287 (@value{GDBP}) print obj.my_method (0x1234)
13288 Cannot resolve method klass::my_method to any overloaded instance
13291 The second example fails because in C@t{++} the integer constant
13292 @samp{0x1234} is not type-compatible with the pointer parameter type.
13294 For the expressions you use in @value{GDBN} commands, you can tell
13295 @value{GDBN} to not enforce strict type checking or
13296 to treat any mismatches as errors and abandon the expression;
13297 When type checking is disabled, @value{GDBN} successfully evaluates
13298 expressions like the second example above.
13300 Even if type checking is off, there may be other reasons
13301 related to type that prevent @value{GDBN} from evaluating an expression.
13302 For instance, @value{GDBN} does not know how to add an @code{int} and
13303 a @code{struct foo}. These particular type errors have nothing to do
13304 with the language in use and usually arise from expressions which make
13305 little sense to evaluate anyway.
13307 @value{GDBN} provides some additional commands for controlling type checking:
13309 @kindex set check type
13310 @kindex show check type
13312 @item set check type on
13313 @itemx set check type off
13314 Set strict type checking on or off. If any type mismatches occur in
13315 evaluating an expression while type checking is on, @value{GDBN} prints a
13316 message and aborts evaluation of the expression.
13318 @item show check type
13319 Show the current setting of type checking and whether @value{GDBN}
13320 is enforcing strict type checking rules.
13323 @cindex range checking
13324 @cindex checks, range
13325 @node Range Checking
13326 @subsection An Overview of Range Checking
13328 In some languages (such as Modula-2), it is an error to exceed the
13329 bounds of a type; this is enforced with run-time checks. Such range
13330 checking is meant to ensure program correctness by making sure
13331 computations do not overflow, or indices on an array element access do
13332 not exceed the bounds of the array.
13334 For expressions you use in @value{GDBN} commands, you can tell
13335 @value{GDBN} to treat range errors in one of three ways: ignore them,
13336 always treat them as errors and abandon the expression, or issue
13337 warnings but evaluate the expression anyway.
13339 A range error can result from numerical overflow, from exceeding an
13340 array index bound, or when you type a constant that is not a member
13341 of any type. Some languages, however, do not treat overflows as an
13342 error. In many implementations of C, mathematical overflow causes the
13343 result to ``wrap around'' to lower values---for example, if @var{m} is
13344 the largest integer value, and @var{s} is the smallest, then
13347 @var{m} + 1 @result{} @var{s}
13350 This, too, is specific to individual languages, and in some cases
13351 specific to individual compilers or machines. @xref{Supported Languages, ,
13352 Supported Languages}, for further details on specific languages.
13354 @value{GDBN} provides some additional commands for controlling the range checker:
13356 @kindex set check range
13357 @kindex show check range
13359 @item set check range auto
13360 Set range checking on or off based on the current working language.
13361 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13364 @item set check range on
13365 @itemx set check range off
13366 Set range checking on or off, overriding the default setting for the
13367 current working language. A warning is issued if the setting does not
13368 match the language default. If a range error occurs and range checking is on,
13369 then a message is printed and evaluation of the expression is aborted.
13371 @item set check range warn
13372 Output messages when the @value{GDBN} range checker detects a range error,
13373 but attempt to evaluate the expression anyway. Evaluating the
13374 expression may still be impossible for other reasons, such as accessing
13375 memory that the process does not own (a typical example from many Unix
13379 Show the current setting of the range checker, and whether or not it is
13380 being set automatically by @value{GDBN}.
13383 @node Supported Languages
13384 @section Supported Languages
13386 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13387 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13388 @c This is false ...
13389 Some @value{GDBN} features may be used in expressions regardless of the
13390 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13391 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13392 ,Expressions}) can be used with the constructs of any supported
13395 The following sections detail to what degree each source language is
13396 supported by @value{GDBN}. These sections are not meant to be language
13397 tutorials or references, but serve only as a reference guide to what the
13398 @value{GDBN} expression parser accepts, and what input and output
13399 formats should look like for different languages. There are many good
13400 books written on each of these languages; please look to these for a
13401 language reference or tutorial.
13404 * C:: C and C@t{++}
13407 * Objective-C:: Objective-C
13408 * OpenCL C:: OpenCL C
13409 * Fortran:: Fortran
13411 * Modula-2:: Modula-2
13416 @subsection C and C@t{++}
13418 @cindex C and C@t{++}
13419 @cindex expressions in C or C@t{++}
13421 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13422 to both languages. Whenever this is the case, we discuss those languages
13426 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13427 @cindex @sc{gnu} C@t{++}
13428 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13429 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13430 effectively, you must compile your C@t{++} programs with a supported
13431 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13432 compiler (@code{aCC}).
13435 * C Operators:: C and C@t{++} operators
13436 * C Constants:: C and C@t{++} constants
13437 * C Plus Plus Expressions:: C@t{++} expressions
13438 * C Defaults:: Default settings for C and C@t{++}
13439 * C Checks:: C and C@t{++} type and range checks
13440 * Debugging C:: @value{GDBN} and C
13441 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13442 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13446 @subsubsection C and C@t{++} Operators
13448 @cindex C and C@t{++} operators
13450 Operators must be defined on values of specific types. For instance,
13451 @code{+} is defined on numbers, but not on structures. Operators are
13452 often defined on groups of types.
13454 For the purposes of C and C@t{++}, the following definitions hold:
13459 @emph{Integral types} include @code{int} with any of its storage-class
13460 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13463 @emph{Floating-point types} include @code{float}, @code{double}, and
13464 @code{long double} (if supported by the target platform).
13467 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13470 @emph{Scalar types} include all of the above.
13475 The following operators are supported. They are listed here
13476 in order of increasing precedence:
13480 The comma or sequencing operator. Expressions in a comma-separated list
13481 are evaluated from left to right, with the result of the entire
13482 expression being the last expression evaluated.
13485 Assignment. The value of an assignment expression is the value
13486 assigned. Defined on scalar types.
13489 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13490 and translated to @w{@code{@var{a} = @var{a op b}}}.
13491 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13492 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13493 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13496 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13497 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13501 Logical @sc{or}. Defined on integral types.
13504 Logical @sc{and}. Defined on integral types.
13507 Bitwise @sc{or}. Defined on integral types.
13510 Bitwise exclusive-@sc{or}. Defined on integral types.
13513 Bitwise @sc{and}. Defined on integral types.
13516 Equality and inequality. Defined on scalar types. The value of these
13517 expressions is 0 for false and non-zero for true.
13519 @item <@r{, }>@r{, }<=@r{, }>=
13520 Less than, greater than, less than or equal, greater than or equal.
13521 Defined on scalar types. The value of these expressions is 0 for false
13522 and non-zero for true.
13525 left shift, and right shift. Defined on integral types.
13528 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13531 Addition and subtraction. Defined on integral types, floating-point types and
13534 @item *@r{, }/@r{, }%
13535 Multiplication, division, and modulus. Multiplication and division are
13536 defined on integral and floating-point types. Modulus is defined on
13540 Increment and decrement. When appearing before a variable, the
13541 operation is performed before the variable is used in an expression;
13542 when appearing after it, the variable's value is used before the
13543 operation takes place.
13546 Pointer dereferencing. Defined on pointer types. Same precedence as
13550 Address operator. Defined on variables. Same precedence as @code{++}.
13552 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13553 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13554 to examine the address
13555 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13559 Negative. Defined on integral and floating-point types. Same
13560 precedence as @code{++}.
13563 Logical negation. Defined on integral types. Same precedence as
13567 Bitwise complement operator. Defined on integral types. Same precedence as
13572 Structure member, and pointer-to-structure member. For convenience,
13573 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13574 pointer based on the stored type information.
13575 Defined on @code{struct} and @code{union} data.
13578 Dereferences of pointers to members.
13581 Array indexing. @code{@var{a}[@var{i}]} is defined as
13582 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13585 Function parameter list. Same precedence as @code{->}.
13588 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13589 and @code{class} types.
13592 Doubled colons also represent the @value{GDBN} scope operator
13593 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13597 If an operator is redefined in the user code, @value{GDBN} usually
13598 attempts to invoke the redefined version instead of using the operator's
13599 predefined meaning.
13602 @subsubsection C and C@t{++} Constants
13604 @cindex C and C@t{++} constants
13606 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13611 Integer constants are a sequence of digits. Octal constants are
13612 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13613 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13614 @samp{l}, specifying that the constant should be treated as a
13618 Floating point constants are a sequence of digits, followed by a decimal
13619 point, followed by a sequence of digits, and optionally followed by an
13620 exponent. An exponent is of the form:
13621 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13622 sequence of digits. The @samp{+} is optional for positive exponents.
13623 A floating-point constant may also end with a letter @samp{f} or
13624 @samp{F}, specifying that the constant should be treated as being of
13625 the @code{float} (as opposed to the default @code{double}) type; or with
13626 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13630 Enumerated constants consist of enumerated identifiers, or their
13631 integral equivalents.
13634 Character constants are a single character surrounded by single quotes
13635 (@code{'}), or a number---the ordinal value of the corresponding character
13636 (usually its @sc{ascii} value). Within quotes, the single character may
13637 be represented by a letter or by @dfn{escape sequences}, which are of
13638 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13639 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13640 @samp{@var{x}} is a predefined special character---for example,
13641 @samp{\n} for newline.
13643 Wide character constants can be written by prefixing a character
13644 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13645 form of @samp{x}. The target wide character set is used when
13646 computing the value of this constant (@pxref{Character Sets}).
13649 String constants are a sequence of character constants surrounded by
13650 double quotes (@code{"}). Any valid character constant (as described
13651 above) may appear. Double quotes within the string must be preceded by
13652 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13655 Wide string constants can be written by prefixing a string constant
13656 with @samp{L}, as in C. The target wide character set is used when
13657 computing the value of this constant (@pxref{Character Sets}).
13660 Pointer constants are an integral value. You can also write pointers
13661 to constants using the C operator @samp{&}.
13664 Array constants are comma-separated lists surrounded by braces @samp{@{}
13665 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13666 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13667 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13670 @node C Plus Plus Expressions
13671 @subsubsection C@t{++} Expressions
13673 @cindex expressions in C@t{++}
13674 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13676 @cindex debugging C@t{++} programs
13677 @cindex C@t{++} compilers
13678 @cindex debug formats and C@t{++}
13679 @cindex @value{NGCC} and C@t{++}
13681 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13682 the proper compiler and the proper debug format. Currently,
13683 @value{GDBN} works best when debugging C@t{++} code that is compiled
13684 with the most recent version of @value{NGCC} possible. The DWARF
13685 debugging format is preferred; @value{NGCC} defaults to this on most
13686 popular platforms. Other compilers and/or debug formats are likely to
13687 work badly or not at all when using @value{GDBN} to debug C@t{++}
13688 code. @xref{Compilation}.
13693 @cindex member functions
13695 Member function calls are allowed; you can use expressions like
13698 count = aml->GetOriginal(x, y)
13701 @vindex this@r{, inside C@t{++} member functions}
13702 @cindex namespace in C@t{++}
13704 While a member function is active (in the selected stack frame), your
13705 expressions have the same namespace available as the member function;
13706 that is, @value{GDBN} allows implicit references to the class instance
13707 pointer @code{this} following the same rules as C@t{++}. @code{using}
13708 declarations in the current scope are also respected by @value{GDBN}.
13710 @cindex call overloaded functions
13711 @cindex overloaded functions, calling
13712 @cindex type conversions in C@t{++}
13714 You can call overloaded functions; @value{GDBN} resolves the function
13715 call to the right definition, with some restrictions. @value{GDBN} does not
13716 perform overload resolution involving user-defined type conversions,
13717 calls to constructors, or instantiations of templates that do not exist
13718 in the program. It also cannot handle ellipsis argument lists or
13721 It does perform integral conversions and promotions, floating-point
13722 promotions, arithmetic conversions, pointer conversions, conversions of
13723 class objects to base classes, and standard conversions such as those of
13724 functions or arrays to pointers; it requires an exact match on the
13725 number of function arguments.
13727 Overload resolution is always performed, unless you have specified
13728 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13729 ,@value{GDBN} Features for C@t{++}}.
13731 You must specify @code{set overload-resolution off} in order to use an
13732 explicit function signature to call an overloaded function, as in
13734 p 'foo(char,int)'('x', 13)
13737 The @value{GDBN} command-completion facility can simplify this;
13738 see @ref{Completion, ,Command Completion}.
13740 @cindex reference declarations
13742 @value{GDBN} understands variables declared as C@t{++} references; you can use
13743 them in expressions just as you do in C@t{++} source---they are automatically
13746 In the parameter list shown when @value{GDBN} displays a frame, the values of
13747 reference variables are not displayed (unlike other variables); this
13748 avoids clutter, since references are often used for large structures.
13749 The @emph{address} of a reference variable is always shown, unless
13750 you have specified @samp{set print address off}.
13753 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13754 expressions can use it just as expressions in your program do. Since
13755 one scope may be defined in another, you can use @code{::} repeatedly if
13756 necessary, for example in an expression like
13757 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13758 resolving name scope by reference to source files, in both C and C@t{++}
13759 debugging (@pxref{Variables, ,Program Variables}).
13762 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13767 @subsubsection C and C@t{++} Defaults
13769 @cindex C and C@t{++} defaults
13771 If you allow @value{GDBN} to set range checking automatically, it
13772 defaults to @code{off} whenever the working language changes to
13773 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13774 selects the working language.
13776 If you allow @value{GDBN} to set the language automatically, it
13777 recognizes source files whose names end with @file{.c}, @file{.C}, or
13778 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13779 these files, it sets the working language to C or C@t{++}.
13780 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13781 for further details.
13784 @subsubsection C and C@t{++} Type and Range Checks
13786 @cindex C and C@t{++} checks
13788 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13789 checking is used. However, if you turn type checking off, @value{GDBN}
13790 will allow certain non-standard conversions, such as promoting integer
13791 constants to pointers.
13793 Range checking, if turned on, is done on mathematical operations. Array
13794 indices are not checked, since they are often used to index a pointer
13795 that is not itself an array.
13798 @subsubsection @value{GDBN} and C
13800 The @code{set print union} and @code{show print union} commands apply to
13801 the @code{union} type. When set to @samp{on}, any @code{union} that is
13802 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13803 appears as @samp{@{...@}}.
13805 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13806 with pointers and a memory allocation function. @xref{Expressions,
13809 @node Debugging C Plus Plus
13810 @subsubsection @value{GDBN} Features for C@t{++}
13812 @cindex commands for C@t{++}
13814 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13815 designed specifically for use with C@t{++}. Here is a summary:
13818 @cindex break in overloaded functions
13819 @item @r{breakpoint menus}
13820 When you want a breakpoint in a function whose name is overloaded,
13821 @value{GDBN} has the capability to display a menu of possible breakpoint
13822 locations to help you specify which function definition you want.
13823 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13825 @cindex overloading in C@t{++}
13826 @item rbreak @var{regex}
13827 Setting breakpoints using regular expressions is helpful for setting
13828 breakpoints on overloaded functions that are not members of any special
13830 @xref{Set Breaks, ,Setting Breakpoints}.
13832 @cindex C@t{++} exception handling
13834 @itemx catch rethrow
13836 Debug C@t{++} exception handling using these commands. @xref{Set
13837 Catchpoints, , Setting Catchpoints}.
13839 @cindex inheritance
13840 @item ptype @var{typename}
13841 Print inheritance relationships as well as other information for type
13843 @xref{Symbols, ,Examining the Symbol Table}.
13845 @item info vtbl @var{expression}.
13846 The @code{info vtbl} command can be used to display the virtual
13847 method tables of the object computed by @var{expression}. This shows
13848 one entry per virtual table; there may be multiple virtual tables when
13849 multiple inheritance is in use.
13851 @cindex C@t{++} symbol display
13852 @item set print demangle
13853 @itemx show print demangle
13854 @itemx set print asm-demangle
13855 @itemx show print asm-demangle
13856 Control whether C@t{++} symbols display in their source form, both when
13857 displaying code as C@t{++} source and when displaying disassemblies.
13858 @xref{Print Settings, ,Print Settings}.
13860 @item set print object
13861 @itemx show print object
13862 Choose whether to print derived (actual) or declared types of objects.
13863 @xref{Print Settings, ,Print Settings}.
13865 @item set print vtbl
13866 @itemx show print vtbl
13867 Control the format for printing virtual function tables.
13868 @xref{Print Settings, ,Print Settings}.
13869 (The @code{vtbl} commands do not work on programs compiled with the HP
13870 ANSI C@t{++} compiler (@code{aCC}).)
13872 @kindex set overload-resolution
13873 @cindex overloaded functions, overload resolution
13874 @item set overload-resolution on
13875 Enable overload resolution for C@t{++} expression evaluation. The default
13876 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13877 and searches for a function whose signature matches the argument types,
13878 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13879 Expressions, ,C@t{++} Expressions}, for details).
13880 If it cannot find a match, it emits a message.
13882 @item set overload-resolution off
13883 Disable overload resolution for C@t{++} expression evaluation. For
13884 overloaded functions that are not class member functions, @value{GDBN}
13885 chooses the first function of the specified name that it finds in the
13886 symbol table, whether or not its arguments are of the correct type. For
13887 overloaded functions that are class member functions, @value{GDBN}
13888 searches for a function whose signature @emph{exactly} matches the
13891 @kindex show overload-resolution
13892 @item show overload-resolution
13893 Show the current setting of overload resolution.
13895 @item @r{Overloaded symbol names}
13896 You can specify a particular definition of an overloaded symbol, using
13897 the same notation that is used to declare such symbols in C@t{++}: type
13898 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13899 also use the @value{GDBN} command-line word completion facilities to list the
13900 available choices, or to finish the type list for you.
13901 @xref{Completion,, Command Completion}, for details on how to do this.
13904 @node Decimal Floating Point
13905 @subsubsection Decimal Floating Point format
13906 @cindex decimal floating point format
13908 @value{GDBN} can examine, set and perform computations with numbers in
13909 decimal floating point format, which in the C language correspond to the
13910 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13911 specified by the extension to support decimal floating-point arithmetic.
13913 There are two encodings in use, depending on the architecture: BID (Binary
13914 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13915 PowerPC and S/390. @value{GDBN} will use the appropriate encoding for the
13918 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13919 to manipulate decimal floating point numbers, it is not possible to convert
13920 (using a cast, for example) integers wider than 32-bit to decimal float.
13922 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13923 point computations, error checking in decimal float operations ignores
13924 underflow, overflow and divide by zero exceptions.
13926 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13927 to inspect @code{_Decimal128} values stored in floating point registers.
13928 See @ref{PowerPC,,PowerPC} for more details.
13934 @value{GDBN} can be used to debug programs written in D and compiled with
13935 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13936 specific feature --- dynamic arrays.
13941 @cindex Go (programming language)
13942 @value{GDBN} can be used to debug programs written in Go and compiled with
13943 @file{gccgo} or @file{6g} compilers.
13945 Here is a summary of the Go-specific features and restrictions:
13948 @cindex current Go package
13949 @item The current Go package
13950 The name of the current package does not need to be specified when
13951 specifying global variables and functions.
13953 For example, given the program:
13957 var myglob = "Shall we?"
13963 When stopped inside @code{main} either of these work:
13967 (gdb) p main.myglob
13970 @cindex builtin Go types
13971 @item Builtin Go types
13972 The @code{string} type is recognized by @value{GDBN} and is printed
13975 @cindex builtin Go functions
13976 @item Builtin Go functions
13977 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13978 function and handles it internally.
13980 @cindex restrictions on Go expressions
13981 @item Restrictions on Go expressions
13982 All Go operators are supported except @code{&^}.
13983 The Go @code{_} ``blank identifier'' is not supported.
13984 Automatic dereferencing of pointers is not supported.
13988 @subsection Objective-C
13990 @cindex Objective-C
13991 This section provides information about some commands and command
13992 options that are useful for debugging Objective-C code. See also
13993 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13994 few more commands specific to Objective-C support.
13997 * Method Names in Commands::
13998 * The Print Command with Objective-C::
14001 @node Method Names in Commands
14002 @subsubsection Method Names in Commands
14004 The following commands have been extended to accept Objective-C method
14005 names as line specifications:
14007 @kindex clear@r{, and Objective-C}
14008 @kindex break@r{, and Objective-C}
14009 @kindex info line@r{, and Objective-C}
14010 @kindex jump@r{, and Objective-C}
14011 @kindex list@r{, and Objective-C}
14015 @item @code{info line}
14020 A fully qualified Objective-C method name is specified as
14023 -[@var{Class} @var{methodName}]
14026 where the minus sign is used to indicate an instance method and a
14027 plus sign (not shown) is used to indicate a class method. The class
14028 name @var{Class} and method name @var{methodName} are enclosed in
14029 brackets, similar to the way messages are specified in Objective-C
14030 source code. For example, to set a breakpoint at the @code{create}
14031 instance method of class @code{Fruit} in the program currently being
14035 break -[Fruit create]
14038 To list ten program lines around the @code{initialize} class method,
14042 list +[NSText initialize]
14045 In the current version of @value{GDBN}, the plus or minus sign is
14046 required. In future versions of @value{GDBN}, the plus or minus
14047 sign will be optional, but you can use it to narrow the search. It
14048 is also possible to specify just a method name:
14054 You must specify the complete method name, including any colons. If
14055 your program's source files contain more than one @code{create} method,
14056 you'll be presented with a numbered list of classes that implement that
14057 method. Indicate your choice by number, or type @samp{0} to exit if
14060 As another example, to clear a breakpoint established at the
14061 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
14064 clear -[NSWindow makeKeyAndOrderFront:]
14067 @node The Print Command with Objective-C
14068 @subsubsection The Print Command With Objective-C
14069 @cindex Objective-C, print objects
14070 @kindex print-object
14071 @kindex po @r{(@code{print-object})}
14073 The print command has also been extended to accept methods. For example:
14076 print -[@var{object} hash]
14079 @cindex print an Objective-C object description
14080 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14082 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14083 and print the result. Also, an additional command has been added,
14084 @code{print-object} or @code{po} for short, which is meant to print
14085 the description of an object. However, this command may only work
14086 with certain Objective-C libraries that have a particular hook
14087 function, @code{_NSPrintForDebugger}, defined.
14090 @subsection OpenCL C
14093 This section provides information about @value{GDBN}s OpenCL C support.
14096 * OpenCL C Datatypes::
14097 * OpenCL C Expressions::
14098 * OpenCL C Operators::
14101 @node OpenCL C Datatypes
14102 @subsubsection OpenCL C Datatypes
14104 @cindex OpenCL C Datatypes
14105 @value{GDBN} supports the builtin scalar and vector datatypes specified
14106 by OpenCL 1.1. In addition the half- and double-precision floating point
14107 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14108 extensions are also known to @value{GDBN}.
14110 @node OpenCL C Expressions
14111 @subsubsection OpenCL C Expressions
14113 @cindex OpenCL C Expressions
14114 @value{GDBN} supports accesses to vector components including the access as
14115 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14116 supported by @value{GDBN} can be used as well.
14118 @node OpenCL C Operators
14119 @subsubsection OpenCL C Operators
14121 @cindex OpenCL C Operators
14122 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14126 @subsection Fortran
14127 @cindex Fortran-specific support in @value{GDBN}
14129 @value{GDBN} can be used to debug programs written in Fortran, but it
14130 currently supports only the features of Fortran 77 language.
14132 @cindex trailing underscore, in Fortran symbols
14133 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14134 among them) append an underscore to the names of variables and
14135 functions. When you debug programs compiled by those compilers, you
14136 will need to refer to variables and functions with a trailing
14140 * Fortran Operators:: Fortran operators and expressions
14141 * Fortran Defaults:: Default settings for Fortran
14142 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14145 @node Fortran Operators
14146 @subsubsection Fortran Operators and Expressions
14148 @cindex Fortran operators and expressions
14150 Operators must be defined on values of specific types. For instance,
14151 @code{+} is defined on numbers, but not on characters or other non-
14152 arithmetic types. Operators are often defined on groups of types.
14156 The exponentiation operator. It raises the first operand to the power
14160 The range operator. Normally used in the form of array(low:high) to
14161 represent a section of array.
14164 The access component operator. Normally used to access elements in derived
14165 types. Also suitable for unions. As unions aren't part of regular Fortran,
14166 this can only happen when accessing a register that uses a gdbarch-defined
14170 @node Fortran Defaults
14171 @subsubsection Fortran Defaults
14173 @cindex Fortran Defaults
14175 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14176 default uses case-insensitive matches for Fortran symbols. You can
14177 change that with the @samp{set case-insensitive} command, see
14178 @ref{Symbols}, for the details.
14180 @node Special Fortran Commands
14181 @subsubsection Special Fortran Commands
14183 @cindex Special Fortran commands
14185 @value{GDBN} has some commands to support Fortran-specific features,
14186 such as displaying common blocks.
14189 @cindex @code{COMMON} blocks, Fortran
14190 @kindex info common
14191 @item info common @r{[}@var{common-name}@r{]}
14192 This command prints the values contained in the Fortran @code{COMMON}
14193 block whose name is @var{common-name}. With no argument, the names of
14194 all @code{COMMON} blocks visible at the current program location are
14201 @cindex Pascal support in @value{GDBN}, limitations
14202 Debugging Pascal programs which use sets, subranges, file variables, or
14203 nested functions does not currently work. @value{GDBN} does not support
14204 entering expressions, printing values, or similar features using Pascal
14207 The Pascal-specific command @code{set print pascal_static-members}
14208 controls whether static members of Pascal objects are displayed.
14209 @xref{Print Settings, pascal_static-members}.
14212 @subsection Modula-2
14214 @cindex Modula-2, @value{GDBN} support
14216 The extensions made to @value{GDBN} to support Modula-2 only support
14217 output from the @sc{gnu} Modula-2 compiler (which is currently being
14218 developed). Other Modula-2 compilers are not currently supported, and
14219 attempting to debug executables produced by them is most likely
14220 to give an error as @value{GDBN} reads in the executable's symbol
14223 @cindex expressions in Modula-2
14225 * M2 Operators:: Built-in operators
14226 * Built-In Func/Proc:: Built-in functions and procedures
14227 * M2 Constants:: Modula-2 constants
14228 * M2 Types:: Modula-2 types
14229 * M2 Defaults:: Default settings for Modula-2
14230 * Deviations:: Deviations from standard Modula-2
14231 * M2 Checks:: Modula-2 type and range checks
14232 * M2 Scope:: The scope operators @code{::} and @code{.}
14233 * GDB/M2:: @value{GDBN} and Modula-2
14237 @subsubsection Operators
14238 @cindex Modula-2 operators
14240 Operators must be defined on values of specific types. For instance,
14241 @code{+} is defined on numbers, but not on structures. Operators are
14242 often defined on groups of types. For the purposes of Modula-2, the
14243 following definitions hold:
14248 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14252 @emph{Character types} consist of @code{CHAR} and its subranges.
14255 @emph{Floating-point types} consist of @code{REAL}.
14258 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14262 @emph{Scalar types} consist of all of the above.
14265 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14268 @emph{Boolean types} consist of @code{BOOLEAN}.
14272 The following operators are supported, and appear in order of
14273 increasing precedence:
14277 Function argument or array index separator.
14280 Assignment. The value of @var{var} @code{:=} @var{value} is
14284 Less than, greater than on integral, floating-point, or enumerated
14288 Less than or equal to, greater than or equal to
14289 on integral, floating-point and enumerated types, or set inclusion on
14290 set types. Same precedence as @code{<}.
14292 @item =@r{, }<>@r{, }#
14293 Equality and two ways of expressing inequality, valid on scalar types.
14294 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14295 available for inequality, since @code{#} conflicts with the script
14299 Set membership. Defined on set types and the types of their members.
14300 Same precedence as @code{<}.
14303 Boolean disjunction. Defined on boolean types.
14306 Boolean conjunction. Defined on boolean types.
14309 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14312 Addition and subtraction on integral and floating-point types, or union
14313 and difference on set types.
14316 Multiplication on integral and floating-point types, or set intersection
14320 Division on floating-point types, or symmetric set difference on set
14321 types. Same precedence as @code{*}.
14324 Integer division and remainder. Defined on integral types. Same
14325 precedence as @code{*}.
14328 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14331 Pointer dereferencing. Defined on pointer types.
14334 Boolean negation. Defined on boolean types. Same precedence as
14338 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14339 precedence as @code{^}.
14342 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14345 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14349 @value{GDBN} and Modula-2 scope operators.
14353 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14354 treats the use of the operator @code{IN}, or the use of operators
14355 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14356 @code{<=}, and @code{>=} on sets as an error.
14360 @node Built-In Func/Proc
14361 @subsubsection Built-in Functions and Procedures
14362 @cindex Modula-2 built-ins
14364 Modula-2 also makes available several built-in procedures and functions.
14365 In describing these, the following metavariables are used:
14370 represents an @code{ARRAY} variable.
14373 represents a @code{CHAR} constant or variable.
14376 represents a variable or constant of integral type.
14379 represents an identifier that belongs to a set. Generally used in the
14380 same function with the metavariable @var{s}. The type of @var{s} should
14381 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14384 represents a variable or constant of integral or floating-point type.
14387 represents a variable or constant of floating-point type.
14393 represents a variable.
14396 represents a variable or constant of one of many types. See the
14397 explanation of the function for details.
14400 All Modula-2 built-in procedures also return a result, described below.
14404 Returns the absolute value of @var{n}.
14407 If @var{c} is a lower case letter, it returns its upper case
14408 equivalent, otherwise it returns its argument.
14411 Returns the character whose ordinal value is @var{i}.
14414 Decrements the value in the variable @var{v} by one. Returns the new value.
14416 @item DEC(@var{v},@var{i})
14417 Decrements the value in the variable @var{v} by @var{i}. Returns the
14420 @item EXCL(@var{m},@var{s})
14421 Removes the element @var{m} from the set @var{s}. Returns the new
14424 @item FLOAT(@var{i})
14425 Returns the floating point equivalent of the integer @var{i}.
14427 @item HIGH(@var{a})
14428 Returns the index of the last member of @var{a}.
14431 Increments the value in the variable @var{v} by one. Returns the new value.
14433 @item INC(@var{v},@var{i})
14434 Increments the value in the variable @var{v} by @var{i}. Returns the
14437 @item INCL(@var{m},@var{s})
14438 Adds the element @var{m} to the set @var{s} if it is not already
14439 there. Returns the new set.
14442 Returns the maximum value of the type @var{t}.
14445 Returns the minimum value of the type @var{t}.
14448 Returns boolean TRUE if @var{i} is an odd number.
14451 Returns the ordinal value of its argument. For example, the ordinal
14452 value of a character is its @sc{ascii} value (on machines supporting the
14453 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14454 integral, character and enumerated types.
14456 @item SIZE(@var{x})
14457 Returns the size of its argument. @var{x} can be a variable or a type.
14459 @item TRUNC(@var{r})
14460 Returns the integral part of @var{r}.
14462 @item TSIZE(@var{x})
14463 Returns the size of its argument. @var{x} can be a variable or a type.
14465 @item VAL(@var{t},@var{i})
14466 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14470 @emph{Warning:} Sets and their operations are not yet supported, so
14471 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14475 @cindex Modula-2 constants
14477 @subsubsection Constants
14479 @value{GDBN} allows you to express the constants of Modula-2 in the following
14485 Integer constants are simply a sequence of digits. When used in an
14486 expression, a constant is interpreted to be type-compatible with the
14487 rest of the expression. Hexadecimal integers are specified by a
14488 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14491 Floating point constants appear as a sequence of digits, followed by a
14492 decimal point and another sequence of digits. An optional exponent can
14493 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14494 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14495 digits of the floating point constant must be valid decimal (base 10)
14499 Character constants consist of a single character enclosed by a pair of
14500 like quotes, either single (@code{'}) or double (@code{"}). They may
14501 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14502 followed by a @samp{C}.
14505 String constants consist of a sequence of characters enclosed by a
14506 pair of like quotes, either single (@code{'}) or double (@code{"}).
14507 Escape sequences in the style of C are also allowed. @xref{C
14508 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14512 Enumerated constants consist of an enumerated identifier.
14515 Boolean constants consist of the identifiers @code{TRUE} and
14519 Pointer constants consist of integral values only.
14522 Set constants are not yet supported.
14526 @subsubsection Modula-2 Types
14527 @cindex Modula-2 types
14529 Currently @value{GDBN} can print the following data types in Modula-2
14530 syntax: array types, record types, set types, pointer types, procedure
14531 types, enumerated types, subrange types and base types. You can also
14532 print the contents of variables declared using these type.
14533 This section gives a number of simple source code examples together with
14534 sample @value{GDBN} sessions.
14536 The first example contains the following section of code:
14545 and you can request @value{GDBN} to interrogate the type and value of
14546 @code{r} and @code{s}.
14549 (@value{GDBP}) print s
14551 (@value{GDBP}) ptype s
14553 (@value{GDBP}) print r
14555 (@value{GDBP}) ptype r
14560 Likewise if your source code declares @code{s} as:
14564 s: SET ['A'..'Z'] ;
14568 then you may query the type of @code{s} by:
14571 (@value{GDBP}) ptype s
14572 type = SET ['A'..'Z']
14576 Note that at present you cannot interactively manipulate set
14577 expressions using the debugger.
14579 The following example shows how you might declare an array in Modula-2
14580 and how you can interact with @value{GDBN} to print its type and contents:
14584 s: ARRAY [-10..10] OF CHAR ;
14588 (@value{GDBP}) ptype s
14589 ARRAY [-10..10] OF CHAR
14592 Note that the array handling is not yet complete and although the type
14593 is printed correctly, expression handling still assumes that all
14594 arrays have a lower bound of zero and not @code{-10} as in the example
14597 Here are some more type related Modula-2 examples:
14601 colour = (blue, red, yellow, green) ;
14602 t = [blue..yellow] ;
14610 The @value{GDBN} interaction shows how you can query the data type
14611 and value of a variable.
14614 (@value{GDBP}) print s
14616 (@value{GDBP}) ptype t
14617 type = [blue..yellow]
14621 In this example a Modula-2 array is declared and its contents
14622 displayed. Observe that the contents are written in the same way as
14623 their @code{C} counterparts.
14627 s: ARRAY [1..5] OF CARDINAL ;
14633 (@value{GDBP}) print s
14634 $1 = @{1, 0, 0, 0, 0@}
14635 (@value{GDBP}) ptype s
14636 type = ARRAY [1..5] OF CARDINAL
14639 The Modula-2 language interface to @value{GDBN} also understands
14640 pointer types as shown in this example:
14644 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14651 and you can request that @value{GDBN} describes the type of @code{s}.
14654 (@value{GDBP}) ptype s
14655 type = POINTER TO ARRAY [1..5] OF CARDINAL
14658 @value{GDBN} handles compound types as we can see in this example.
14659 Here we combine array types, record types, pointer types and subrange
14670 myarray = ARRAY myrange OF CARDINAL ;
14671 myrange = [-2..2] ;
14673 s: POINTER TO ARRAY myrange OF foo ;
14677 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14681 (@value{GDBP}) ptype s
14682 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14685 f3 : ARRAY [-2..2] OF CARDINAL;
14690 @subsubsection Modula-2 Defaults
14691 @cindex Modula-2 defaults
14693 If type and range checking are set automatically by @value{GDBN}, they
14694 both default to @code{on} whenever the working language changes to
14695 Modula-2. This happens regardless of whether you or @value{GDBN}
14696 selected the working language.
14698 If you allow @value{GDBN} to set the language automatically, then entering
14699 code compiled from a file whose name ends with @file{.mod} sets the
14700 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14701 Infer the Source Language}, for further details.
14704 @subsubsection Deviations from Standard Modula-2
14705 @cindex Modula-2, deviations from
14707 A few changes have been made to make Modula-2 programs easier to debug.
14708 This is done primarily via loosening its type strictness:
14712 Unlike in standard Modula-2, pointer constants can be formed by
14713 integers. This allows you to modify pointer variables during
14714 debugging. (In standard Modula-2, the actual address contained in a
14715 pointer variable is hidden from you; it can only be modified
14716 through direct assignment to another pointer variable or expression that
14717 returned a pointer.)
14720 C escape sequences can be used in strings and characters to represent
14721 non-printable characters. @value{GDBN} prints out strings with these
14722 escape sequences embedded. Single non-printable characters are
14723 printed using the @samp{CHR(@var{nnn})} format.
14726 The assignment operator (@code{:=}) returns the value of its right-hand
14730 All built-in procedures both modify @emph{and} return their argument.
14734 @subsubsection Modula-2 Type and Range Checks
14735 @cindex Modula-2 checks
14738 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14741 @c FIXME remove warning when type/range checks added
14743 @value{GDBN} considers two Modula-2 variables type equivalent if:
14747 They are of types that have been declared equivalent via a @code{TYPE
14748 @var{t1} = @var{t2}} statement
14751 They have been declared on the same line. (Note: This is true of the
14752 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14755 As long as type checking is enabled, any attempt to combine variables
14756 whose types are not equivalent is an error.
14758 Range checking is done on all mathematical operations, assignment, array
14759 index bounds, and all built-in functions and procedures.
14762 @subsubsection The Scope Operators @code{::} and @code{.}
14764 @cindex @code{.}, Modula-2 scope operator
14765 @cindex colon, doubled as scope operator
14767 @vindex colon-colon@r{, in Modula-2}
14768 @c Info cannot handle :: but TeX can.
14771 @vindex ::@r{, in Modula-2}
14774 There are a few subtle differences between the Modula-2 scope operator
14775 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14780 @var{module} . @var{id}
14781 @var{scope} :: @var{id}
14785 where @var{scope} is the name of a module or a procedure,
14786 @var{module} the name of a module, and @var{id} is any declared
14787 identifier within your program, except another module.
14789 Using the @code{::} operator makes @value{GDBN} search the scope
14790 specified by @var{scope} for the identifier @var{id}. If it is not
14791 found in the specified scope, then @value{GDBN} searches all scopes
14792 enclosing the one specified by @var{scope}.
14794 Using the @code{.} operator makes @value{GDBN} search the current scope for
14795 the identifier specified by @var{id} that was imported from the
14796 definition module specified by @var{module}. With this operator, it is
14797 an error if the identifier @var{id} was not imported from definition
14798 module @var{module}, or if @var{id} is not an identifier in
14802 @subsubsection @value{GDBN} and Modula-2
14804 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14805 Five subcommands of @code{set print} and @code{show print} apply
14806 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14807 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14808 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14809 analogue in Modula-2.
14811 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14812 with any language, is not useful with Modula-2. Its
14813 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14814 created in Modula-2 as they can in C or C@t{++}. However, because an
14815 address can be specified by an integral constant, the construct
14816 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14818 @cindex @code{#} in Modula-2
14819 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14820 interpreted as the beginning of a comment. Use @code{<>} instead.
14826 The extensions made to @value{GDBN} for Ada only support
14827 output from the @sc{gnu} Ada (GNAT) compiler.
14828 Other Ada compilers are not currently supported, and
14829 attempting to debug executables produced by them is most likely
14833 @cindex expressions in Ada
14835 * Ada Mode Intro:: General remarks on the Ada syntax
14836 and semantics supported by Ada mode
14838 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14839 * Additions to Ada:: Extensions of the Ada expression syntax.
14840 * Stopping Before Main Program:: Debugging the program during elaboration.
14841 * Ada Tasks:: Listing and setting breakpoints in tasks.
14842 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14843 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14845 * Ada Glitches:: Known peculiarities of Ada mode.
14848 @node Ada Mode Intro
14849 @subsubsection Introduction
14850 @cindex Ada mode, general
14852 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14853 syntax, with some extensions.
14854 The philosophy behind the design of this subset is
14858 That @value{GDBN} should provide basic literals and access to operations for
14859 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14860 leaving more sophisticated computations to subprograms written into the
14861 program (which therefore may be called from @value{GDBN}).
14864 That type safety and strict adherence to Ada language restrictions
14865 are not particularly important to the @value{GDBN} user.
14868 That brevity is important to the @value{GDBN} user.
14871 Thus, for brevity, the debugger acts as if all names declared in
14872 user-written packages are directly visible, even if they are not visible
14873 according to Ada rules, thus making it unnecessary to fully qualify most
14874 names with their packages, regardless of context. Where this causes
14875 ambiguity, @value{GDBN} asks the user's intent.
14877 The debugger will start in Ada mode if it detects an Ada main program.
14878 As for other languages, it will enter Ada mode when stopped in a program that
14879 was translated from an Ada source file.
14881 While in Ada mode, you may use `@t{--}' for comments. This is useful
14882 mostly for documenting command files. The standard @value{GDBN} comment
14883 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14884 middle (to allow based literals).
14886 The debugger supports limited overloading. Given a subprogram call in which
14887 the function symbol has multiple definitions, it will use the number of
14888 actual parameters and some information about their types to attempt to narrow
14889 the set of definitions. It also makes very limited use of context, preferring
14890 procedures to functions in the context of the @code{call} command, and
14891 functions to procedures elsewhere.
14893 @node Omissions from Ada
14894 @subsubsection Omissions from Ada
14895 @cindex Ada, omissions from
14897 Here are the notable omissions from the subset:
14901 Only a subset of the attributes are supported:
14905 @t{'First}, @t{'Last}, and @t{'Length}
14906 on array objects (not on types and subtypes).
14909 @t{'Min} and @t{'Max}.
14912 @t{'Pos} and @t{'Val}.
14918 @t{'Range} on array objects (not subtypes), but only as the right
14919 operand of the membership (@code{in}) operator.
14922 @t{'Access}, @t{'Unchecked_Access}, and
14923 @t{'Unrestricted_Access} (a GNAT extension).
14931 @code{Characters.Latin_1} are not available and
14932 concatenation is not implemented. Thus, escape characters in strings are
14933 not currently available.
14936 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14937 equality of representations. They will generally work correctly
14938 for strings and arrays whose elements have integer or enumeration types.
14939 They may not work correctly for arrays whose element
14940 types have user-defined equality, for arrays of real values
14941 (in particular, IEEE-conformant floating point, because of negative
14942 zeroes and NaNs), and for arrays whose elements contain unused bits with
14943 indeterminate values.
14946 The other component-by-component array operations (@code{and}, @code{or},
14947 @code{xor}, @code{not}, and relational tests other than equality)
14948 are not implemented.
14951 @cindex array aggregates (Ada)
14952 @cindex record aggregates (Ada)
14953 @cindex aggregates (Ada)
14954 There is limited support for array and record aggregates. They are
14955 permitted only on the right sides of assignments, as in these examples:
14958 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14959 (@value{GDBP}) set An_Array := (1, others => 0)
14960 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14961 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14962 (@value{GDBP}) set A_Record := (1, "Peter", True);
14963 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14967 discriminant's value by assigning an aggregate has an
14968 undefined effect if that discriminant is used within the record.
14969 However, you can first modify discriminants by directly assigning to
14970 them (which normally would not be allowed in Ada), and then performing an
14971 aggregate assignment. For example, given a variable @code{A_Rec}
14972 declared to have a type such as:
14975 type Rec (Len : Small_Integer := 0) is record
14977 Vals : IntArray (1 .. Len);
14981 you can assign a value with a different size of @code{Vals} with two
14985 (@value{GDBP}) set A_Rec.Len := 4
14986 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14989 As this example also illustrates, @value{GDBN} is very loose about the usual
14990 rules concerning aggregates. You may leave out some of the
14991 components of an array or record aggregate (such as the @code{Len}
14992 component in the assignment to @code{A_Rec} above); they will retain their
14993 original values upon assignment. You may freely use dynamic values as
14994 indices in component associations. You may even use overlapping or
14995 redundant component associations, although which component values are
14996 assigned in such cases is not defined.
14999 Calls to dispatching subprograms are not implemented.
15002 The overloading algorithm is much more limited (i.e., less selective)
15003 than that of real Ada. It makes only limited use of the context in
15004 which a subexpression appears to resolve its meaning, and it is much
15005 looser in its rules for allowing type matches. As a result, some
15006 function calls will be ambiguous, and the user will be asked to choose
15007 the proper resolution.
15010 The @code{new} operator is not implemented.
15013 Entry calls are not implemented.
15016 Aside from printing, arithmetic operations on the native VAX floating-point
15017 formats are not supported.
15020 It is not possible to slice a packed array.
15023 The names @code{True} and @code{False}, when not part of a qualified name,
15024 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
15026 Should your program
15027 redefine these names in a package or procedure (at best a dubious practice),
15028 you will have to use fully qualified names to access their new definitions.
15031 @node Additions to Ada
15032 @subsubsection Additions to Ada
15033 @cindex Ada, deviations from
15035 As it does for other languages, @value{GDBN} makes certain generic
15036 extensions to Ada (@pxref{Expressions}):
15040 If the expression @var{E} is a variable residing in memory (typically
15041 a local variable or array element) and @var{N} is a positive integer,
15042 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
15043 @var{N}-1 adjacent variables following it in memory as an array. In
15044 Ada, this operator is generally not necessary, since its prime use is
15045 in displaying parts of an array, and slicing will usually do this in
15046 Ada. However, there are occasional uses when debugging programs in
15047 which certain debugging information has been optimized away.
15050 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
15051 appears in function or file @var{B}.'' When @var{B} is a file name,
15052 you must typically surround it in single quotes.
15055 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
15056 @var{type} that appears at address @var{addr}.''
15059 A name starting with @samp{$} is a convenience variable
15060 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
15063 In addition, @value{GDBN} provides a few other shortcuts and outright
15064 additions specific to Ada:
15068 The assignment statement is allowed as an expression, returning
15069 its right-hand operand as its value. Thus, you may enter
15072 (@value{GDBP}) set x := y + 3
15073 (@value{GDBP}) print A(tmp := y + 1)
15077 The semicolon is allowed as an ``operator,'' returning as its value
15078 the value of its right-hand operand.
15079 This allows, for example,
15080 complex conditional breaks:
15083 (@value{GDBP}) break f
15084 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15088 Rather than use catenation and symbolic character names to introduce special
15089 characters into strings, one may instead use a special bracket notation,
15090 which is also used to print strings. A sequence of characters of the form
15091 @samp{["@var{XX}"]} within a string or character literal denotes the
15092 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15093 sequence of characters @samp{["""]} also denotes a single quotation mark
15094 in strings. For example,
15096 "One line.["0a"]Next line.["0a"]"
15099 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15103 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15104 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15108 (@value{GDBP}) print 'max(x, y)
15112 When printing arrays, @value{GDBN} uses positional notation when the
15113 array has a lower bound of 1, and uses a modified named notation otherwise.
15114 For example, a one-dimensional array of three integers with a lower bound
15115 of 3 might print as
15122 That is, in contrast to valid Ada, only the first component has a @code{=>}
15126 You may abbreviate attributes in expressions with any unique,
15127 multi-character subsequence of
15128 their names (an exact match gets preference).
15129 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15130 in place of @t{a'length}.
15133 @cindex quoting Ada internal identifiers
15134 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15135 to lower case. The GNAT compiler uses upper-case characters for
15136 some of its internal identifiers, which are normally of no interest to users.
15137 For the rare occasions when you actually have to look at them,
15138 enclose them in angle brackets to avoid the lower-case mapping.
15141 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15145 Printing an object of class-wide type or dereferencing an
15146 access-to-class-wide value will display all the components of the object's
15147 specific type (as indicated by its run-time tag). Likewise, component
15148 selection on such a value will operate on the specific type of the
15153 @node Stopping Before Main Program
15154 @subsubsection Stopping at the Very Beginning
15156 @cindex breakpointing Ada elaboration code
15157 It is sometimes necessary to debug the program during elaboration, and
15158 before reaching the main procedure.
15159 As defined in the Ada Reference
15160 Manual, the elaboration code is invoked from a procedure called
15161 @code{adainit}. To run your program up to the beginning of
15162 elaboration, simply use the following two commands:
15163 @code{tbreak adainit} and @code{run}.
15166 @subsubsection Extensions for Ada Tasks
15167 @cindex Ada, tasking
15169 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15170 @value{GDBN} provides the following task-related commands:
15175 This command shows a list of current Ada tasks, as in the following example:
15182 (@value{GDBP}) info tasks
15183 ID TID P-ID Pri State Name
15184 1 8088000 0 15 Child Activation Wait main_task
15185 2 80a4000 1 15 Accept Statement b
15186 3 809a800 1 15 Child Activation Wait a
15187 * 4 80ae800 3 15 Runnable c
15192 In this listing, the asterisk before the last task indicates it to be the
15193 task currently being inspected.
15197 Represents @value{GDBN}'s internal task number.
15203 The parent's task ID (@value{GDBN}'s internal task number).
15206 The base priority of the task.
15209 Current state of the task.
15213 The task has been created but has not been activated. It cannot be
15217 The task is not blocked for any reason known to Ada. (It may be waiting
15218 for a mutex, though.) It is conceptually "executing" in normal mode.
15221 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15222 that were waiting on terminate alternatives have been awakened and have
15223 terminated themselves.
15225 @item Child Activation Wait
15226 The task is waiting for created tasks to complete activation.
15228 @item Accept Statement
15229 The task is waiting on an accept or selective wait statement.
15231 @item Waiting on entry call
15232 The task is waiting on an entry call.
15234 @item Async Select Wait
15235 The task is waiting to start the abortable part of an asynchronous
15239 The task is waiting on a select statement with only a delay
15242 @item Child Termination Wait
15243 The task is sleeping having completed a master within itself, and is
15244 waiting for the tasks dependent on that master to become terminated or
15245 waiting on a terminate Phase.
15247 @item Wait Child in Term Alt
15248 The task is sleeping waiting for tasks on terminate alternatives to
15249 finish terminating.
15251 @item Accepting RV with @var{taskno}
15252 The task is accepting a rendez-vous with the task @var{taskno}.
15256 Name of the task in the program.
15260 @kindex info task @var{taskno}
15261 @item info task @var{taskno}
15262 This command shows detailled informations on the specified task, as in
15263 the following example:
15268 (@value{GDBP}) info tasks
15269 ID TID P-ID Pri State Name
15270 1 8077880 0 15 Child Activation Wait main_task
15271 * 2 807c468 1 15 Runnable task_1
15272 (@value{GDBP}) info task 2
15273 Ada Task: 0x807c468
15276 Parent: 1 (main_task)
15282 @kindex task@r{ (Ada)}
15283 @cindex current Ada task ID
15284 This command prints the ID of the current task.
15290 (@value{GDBP}) info tasks
15291 ID TID P-ID Pri State Name
15292 1 8077870 0 15 Child Activation Wait main_task
15293 * 2 807c458 1 15 Runnable t
15294 (@value{GDBP}) task
15295 [Current task is 2]
15298 @item task @var{taskno}
15299 @cindex Ada task switching
15300 This command is like the @code{thread @var{threadno}}
15301 command (@pxref{Threads}). It switches the context of debugging
15302 from the current task to the given task.
15308 (@value{GDBP}) info tasks
15309 ID TID P-ID Pri State Name
15310 1 8077870 0 15 Child Activation Wait main_task
15311 * 2 807c458 1 15 Runnable t
15312 (@value{GDBP}) task 1
15313 [Switching to task 1]
15314 #0 0x8067726 in pthread_cond_wait ()
15316 #0 0x8067726 in pthread_cond_wait ()
15317 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15318 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15319 #3 0x806153e in system.tasking.stages.activate_tasks ()
15320 #4 0x804aacc in un () at un.adb:5
15323 @item break @var{linespec} task @var{taskno}
15324 @itemx break @var{linespec} task @var{taskno} if @dots{}
15325 @cindex breakpoints and tasks, in Ada
15326 @cindex task breakpoints, in Ada
15327 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15328 These commands are like the @code{break @dots{} thread @dots{}}
15329 command (@pxref{Thread Stops}).
15330 @var{linespec} specifies source lines, as described
15331 in @ref{Specify Location}.
15333 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15334 to specify that you only want @value{GDBN} to stop the program when a
15335 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15336 numeric task identifiers assigned by @value{GDBN}, shown in the first
15337 column of the @samp{info tasks} display.
15339 If you do not specify @samp{task @var{taskno}} when you set a
15340 breakpoint, the breakpoint applies to @emph{all} tasks of your
15343 You can use the @code{task} qualifier on conditional breakpoints as
15344 well; in this case, place @samp{task @var{taskno}} before the
15345 breakpoint condition (before the @code{if}).
15353 (@value{GDBP}) info tasks
15354 ID TID P-ID Pri State Name
15355 1 140022020 0 15 Child Activation Wait main_task
15356 2 140045060 1 15 Accept/Select Wait t2
15357 3 140044840 1 15 Runnable t1
15358 * 4 140056040 1 15 Runnable t3
15359 (@value{GDBP}) b 15 task 2
15360 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15361 (@value{GDBP}) cont
15366 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15368 (@value{GDBP}) info tasks
15369 ID TID P-ID Pri State Name
15370 1 140022020 0 15 Child Activation Wait main_task
15371 * 2 140045060 1 15 Runnable t2
15372 3 140044840 1 15 Runnable t1
15373 4 140056040 1 15 Delay Sleep t3
15377 @node Ada Tasks and Core Files
15378 @subsubsection Tasking Support when Debugging Core Files
15379 @cindex Ada tasking and core file debugging
15381 When inspecting a core file, as opposed to debugging a live program,
15382 tasking support may be limited or even unavailable, depending on
15383 the platform being used.
15384 For instance, on x86-linux, the list of tasks is available, but task
15385 switching is not supported. On Tru64, however, task switching will work
15388 On certain platforms, including Tru64, the debugger needs to perform some
15389 memory writes in order to provide Ada tasking support. When inspecting
15390 a core file, this means that the core file must be opened with read-write
15391 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15392 Under these circumstances, you should make a backup copy of the core
15393 file before inspecting it with @value{GDBN}.
15395 @node Ravenscar Profile
15396 @subsubsection Tasking Support when using the Ravenscar Profile
15397 @cindex Ravenscar Profile
15399 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15400 specifically designed for systems with safety-critical real-time
15404 @kindex set ravenscar task-switching on
15405 @cindex task switching with program using Ravenscar Profile
15406 @item set ravenscar task-switching on
15407 Allows task switching when debugging a program that uses the Ravenscar
15408 Profile. This is the default.
15410 @kindex set ravenscar task-switching off
15411 @item set ravenscar task-switching off
15412 Turn off task switching when debugging a program that uses the Ravenscar
15413 Profile. This is mostly intended to disable the code that adds support
15414 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15415 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15416 To be effective, this command should be run before the program is started.
15418 @kindex show ravenscar task-switching
15419 @item show ravenscar task-switching
15420 Show whether it is possible to switch from task to task in a program
15421 using the Ravenscar Profile.
15426 @subsubsection Known Peculiarities of Ada Mode
15427 @cindex Ada, problems
15429 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15430 we know of several problems with and limitations of Ada mode in
15432 some of which will be fixed with planned future releases of the debugger
15433 and the GNU Ada compiler.
15437 Static constants that the compiler chooses not to materialize as objects in
15438 storage are invisible to the debugger.
15441 Named parameter associations in function argument lists are ignored (the
15442 argument lists are treated as positional).
15445 Many useful library packages are currently invisible to the debugger.
15448 Fixed-point arithmetic, conversions, input, and output is carried out using
15449 floating-point arithmetic, and may give results that only approximate those on
15453 The GNAT compiler never generates the prefix @code{Standard} for any of
15454 the standard symbols defined by the Ada language. @value{GDBN} knows about
15455 this: it will strip the prefix from names when you use it, and will never
15456 look for a name you have so qualified among local symbols, nor match against
15457 symbols in other packages or subprograms. If you have
15458 defined entities anywhere in your program other than parameters and
15459 local variables whose simple names match names in @code{Standard},
15460 GNAT's lack of qualification here can cause confusion. When this happens,
15461 you can usually resolve the confusion
15462 by qualifying the problematic names with package
15463 @code{Standard} explicitly.
15466 Older versions of the compiler sometimes generate erroneous debugging
15467 information, resulting in the debugger incorrectly printing the value
15468 of affected entities. In some cases, the debugger is able to work
15469 around an issue automatically. In other cases, the debugger is able
15470 to work around the issue, but the work-around has to be specifically
15473 @kindex set ada trust-PAD-over-XVS
15474 @kindex show ada trust-PAD-over-XVS
15477 @item set ada trust-PAD-over-XVS on
15478 Configure GDB to strictly follow the GNAT encoding when computing the
15479 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15480 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15481 a complete description of the encoding used by the GNAT compiler).
15482 This is the default.
15484 @item set ada trust-PAD-over-XVS off
15485 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15486 sometimes prints the wrong value for certain entities, changing @code{ada
15487 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15488 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15489 @code{off}, but this incurs a slight performance penalty, so it is
15490 recommended to leave this setting to @code{on} unless necessary.
15494 @node Unsupported Languages
15495 @section Unsupported Languages
15497 @cindex unsupported languages
15498 @cindex minimal language
15499 In addition to the other fully-supported programming languages,
15500 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15501 It does not represent a real programming language, but provides a set
15502 of capabilities close to what the C or assembly languages provide.
15503 This should allow most simple operations to be performed while debugging
15504 an application that uses a language currently not supported by @value{GDBN}.
15506 If the language is set to @code{auto}, @value{GDBN} will automatically
15507 select this language if the current frame corresponds to an unsupported
15511 @chapter Examining the Symbol Table
15513 The commands described in this chapter allow you to inquire about the
15514 symbols (names of variables, functions and types) defined in your
15515 program. This information is inherent in the text of your program and
15516 does not change as your program executes. @value{GDBN} finds it in your
15517 program's symbol table, in the file indicated when you started @value{GDBN}
15518 (@pxref{File Options, ,Choosing Files}), or by one of the
15519 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15521 @cindex symbol names
15522 @cindex names of symbols
15523 @cindex quoting names
15524 Occasionally, you may need to refer to symbols that contain unusual
15525 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15526 most frequent case is in referring to static variables in other
15527 source files (@pxref{Variables,,Program Variables}). File names
15528 are recorded in object files as debugging symbols, but @value{GDBN} would
15529 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15530 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15531 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15538 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15541 @cindex case-insensitive symbol names
15542 @cindex case sensitivity in symbol names
15543 @kindex set case-sensitive
15544 @item set case-sensitive on
15545 @itemx set case-sensitive off
15546 @itemx set case-sensitive auto
15547 Normally, when @value{GDBN} looks up symbols, it matches their names
15548 with case sensitivity determined by the current source language.
15549 Occasionally, you may wish to control that. The command @code{set
15550 case-sensitive} lets you do that by specifying @code{on} for
15551 case-sensitive matches or @code{off} for case-insensitive ones. If
15552 you specify @code{auto}, case sensitivity is reset to the default
15553 suitable for the source language. The default is case-sensitive
15554 matches for all languages except for Fortran, for which the default is
15555 case-insensitive matches.
15557 @kindex show case-sensitive
15558 @item show case-sensitive
15559 This command shows the current setting of case sensitivity for symbols
15562 @kindex set print type methods
15563 @item set print type methods
15564 @itemx set print type methods on
15565 @itemx set print type methods off
15566 Normally, when @value{GDBN} prints a class, it displays any methods
15567 declared in that class. You can control this behavior either by
15568 passing the appropriate flag to @code{ptype}, or using @command{set
15569 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15570 display the methods; this is the default. Specifying @code{off} will
15571 cause @value{GDBN} to omit the methods.
15573 @kindex show print type methods
15574 @item show print type methods
15575 This command shows the current setting of method display when printing
15578 @kindex set print type typedefs
15579 @item set print type typedefs
15580 @itemx set print type typedefs on
15581 @itemx set print type typedefs off
15583 Normally, when @value{GDBN} prints a class, it displays any typedefs
15584 defined in that class. You can control this behavior either by
15585 passing the appropriate flag to @code{ptype}, or using @command{set
15586 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15587 display the typedef definitions; this is the default. Specifying
15588 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15589 Note that this controls whether the typedef definition itself is
15590 printed, not whether typedef names are substituted when printing other
15593 @kindex show print type typedefs
15594 @item show print type typedefs
15595 This command shows the current setting of typedef display when
15598 @kindex info address
15599 @cindex address of a symbol
15600 @item info address @var{symbol}
15601 Describe where the data for @var{symbol} is stored. For a register
15602 variable, this says which register it is kept in. For a non-register
15603 local variable, this prints the stack-frame offset at which the variable
15606 Note the contrast with @samp{print &@var{symbol}}, which does not work
15607 at all for a register variable, and for a stack local variable prints
15608 the exact address of the current instantiation of the variable.
15610 @kindex info symbol
15611 @cindex symbol from address
15612 @cindex closest symbol and offset for an address
15613 @item info symbol @var{addr}
15614 Print the name of a symbol which is stored at the address @var{addr}.
15615 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15616 nearest symbol and an offset from it:
15619 (@value{GDBP}) info symbol 0x54320
15620 _initialize_vx + 396 in section .text
15624 This is the opposite of the @code{info address} command. You can use
15625 it to find out the name of a variable or a function given its address.
15627 For dynamically linked executables, the name of executable or shared
15628 library containing the symbol is also printed:
15631 (@value{GDBP}) info symbol 0x400225
15632 _start + 5 in section .text of /tmp/a.out
15633 (@value{GDBP}) info symbol 0x2aaaac2811cf
15634 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15638 @item whatis[/@var{flags}] [@var{arg}]
15639 Print the data type of @var{arg}, which can be either an expression
15640 or a name of a data type. With no argument, print the data type of
15641 @code{$}, the last value in the value history.
15643 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15644 is not actually evaluated, and any side-effecting operations (such as
15645 assignments or function calls) inside it do not take place.
15647 If @var{arg} is a variable or an expression, @code{whatis} prints its
15648 literal type as it is used in the source code. If the type was
15649 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15650 the data type underlying the @code{typedef}. If the type of the
15651 variable or the expression is a compound data type, such as
15652 @code{struct} or @code{class}, @code{whatis} never prints their
15653 fields or methods. It just prints the @code{struct}/@code{class}
15654 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15655 such a compound data type, use @code{ptype}.
15657 If @var{arg} is a type name that was defined using @code{typedef},
15658 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15659 Unrolling means that @code{whatis} will show the underlying type used
15660 in the @code{typedef} declaration of @var{arg}. However, if that
15661 underlying type is also a @code{typedef}, @code{whatis} will not
15664 For C code, the type names may also have the form @samp{class
15665 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15666 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15668 @var{flags} can be used to modify how the type is displayed.
15669 Available flags are:
15673 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15674 parameters and typedefs defined in a class when printing the class'
15675 members. The @code{/r} flag disables this.
15678 Do not print methods defined in the class.
15681 Print methods defined in the class. This is the default, but the flag
15682 exists in case you change the default with @command{set print type methods}.
15685 Do not print typedefs defined in the class. Note that this controls
15686 whether the typedef definition itself is printed, not whether typedef
15687 names are substituted when printing other types.
15690 Print typedefs defined in the class. This is the default, but the flag
15691 exists in case you change the default with @command{set print type typedefs}.
15695 @item ptype[/@var{flags}] [@var{arg}]
15696 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15697 detailed description of the type, instead of just the name of the type.
15698 @xref{Expressions, ,Expressions}.
15700 Contrary to @code{whatis}, @code{ptype} always unrolls any
15701 @code{typedef}s in its argument declaration, whether the argument is
15702 a variable, expression, or a data type. This means that @code{ptype}
15703 of a variable or an expression will not print literally its type as
15704 present in the source code---use @code{whatis} for that. @code{typedef}s at
15705 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15706 fields, methods and inner @code{class typedef}s of @code{struct}s,
15707 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15709 For example, for this variable declaration:
15712 typedef double real_t;
15713 struct complex @{ real_t real; double imag; @};
15714 typedef struct complex complex_t;
15716 real_t *real_pointer_var;
15720 the two commands give this output:
15724 (@value{GDBP}) whatis var
15726 (@value{GDBP}) ptype var
15727 type = struct complex @{
15731 (@value{GDBP}) whatis complex_t
15732 type = struct complex
15733 (@value{GDBP}) whatis struct complex
15734 type = struct complex
15735 (@value{GDBP}) ptype struct complex
15736 type = struct complex @{
15740 (@value{GDBP}) whatis real_pointer_var
15742 (@value{GDBP}) ptype real_pointer_var
15748 As with @code{whatis}, using @code{ptype} without an argument refers to
15749 the type of @code{$}, the last value in the value history.
15751 @cindex incomplete type
15752 Sometimes, programs use opaque data types or incomplete specifications
15753 of complex data structure. If the debug information included in the
15754 program does not allow @value{GDBN} to display a full declaration of
15755 the data type, it will say @samp{<incomplete type>}. For example,
15756 given these declarations:
15760 struct foo *fooptr;
15764 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15767 (@value{GDBP}) ptype foo
15768 $1 = <incomplete type>
15772 ``Incomplete type'' is C terminology for data types that are not
15773 completely specified.
15776 @item info types @var{regexp}
15778 Print a brief description of all types whose names match the regular
15779 expression @var{regexp} (or all types in your program, if you supply
15780 no argument). Each complete typename is matched as though it were a
15781 complete line; thus, @samp{i type value} gives information on all
15782 types in your program whose names include the string @code{value}, but
15783 @samp{i type ^value$} gives information only on types whose complete
15784 name is @code{value}.
15786 This command differs from @code{ptype} in two ways: first, like
15787 @code{whatis}, it does not print a detailed description; second, it
15788 lists all source files where a type is defined.
15790 @kindex info type-printers
15791 @item info type-printers
15792 Versions of @value{GDBN} that ship with Python scripting enabled may
15793 have ``type printers'' available. When using @command{ptype} or
15794 @command{whatis}, these printers are consulted when the name of a type
15795 is needed. @xref{Type Printing API}, for more information on writing
15798 @code{info type-printers} displays all the available type printers.
15800 @kindex enable type-printer
15801 @kindex disable type-printer
15802 @item enable type-printer @var{name}@dots{}
15803 @item disable type-printer @var{name}@dots{}
15804 These commands can be used to enable or disable type printers.
15807 @cindex local variables
15808 @item info scope @var{location}
15809 List all the variables local to a particular scope. This command
15810 accepts a @var{location} argument---a function name, a source line, or
15811 an address preceded by a @samp{*}, and prints all the variables local
15812 to the scope defined by that location. (@xref{Specify Location}, for
15813 details about supported forms of @var{location}.) For example:
15816 (@value{GDBP}) @b{info scope command_line_handler}
15817 Scope for command_line_handler:
15818 Symbol rl is an argument at stack/frame offset 8, length 4.
15819 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15820 Symbol linelength is in static storage at address 0x150a1c, length 4.
15821 Symbol p is a local variable in register $esi, length 4.
15822 Symbol p1 is a local variable in register $ebx, length 4.
15823 Symbol nline is a local variable in register $edx, length 4.
15824 Symbol repeat is a local variable at frame offset -8, length 4.
15828 This command is especially useful for determining what data to collect
15829 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15832 @kindex info source
15834 Show information about the current source file---that is, the source file for
15835 the function containing the current point of execution:
15838 the name of the source file, and the directory containing it,
15840 the directory it was compiled in,
15842 its length, in lines,
15844 which programming language it is written in,
15846 whether the executable includes debugging information for that file, and
15847 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15849 whether the debugging information includes information about
15850 preprocessor macros.
15854 @kindex info sources
15856 Print the names of all source files in your program for which there is
15857 debugging information, organized into two lists: files whose symbols
15858 have already been read, and files whose symbols will be read when needed.
15860 @kindex info functions
15861 @item info functions
15862 Print the names and data types of all defined functions.
15864 @item info functions @var{regexp}
15865 Print the names and data types of all defined functions
15866 whose names contain a match for regular expression @var{regexp}.
15867 Thus, @samp{info fun step} finds all functions whose names
15868 include @code{step}; @samp{info fun ^step} finds those whose names
15869 start with @code{step}. If a function name contains characters
15870 that conflict with the regular expression language (e.g.@:
15871 @samp{operator*()}), they may be quoted with a backslash.
15873 @kindex info variables
15874 @item info variables
15875 Print the names and data types of all variables that are defined
15876 outside of functions (i.e.@: excluding local variables).
15878 @item info variables @var{regexp}
15879 Print the names and data types of all variables (except for local
15880 variables) whose names contain a match for regular expression
15883 @kindex info classes
15884 @cindex Objective-C, classes and selectors
15886 @itemx info classes @var{regexp}
15887 Display all Objective-C classes in your program, or
15888 (with the @var{regexp} argument) all those matching a particular regular
15891 @kindex info selectors
15892 @item info selectors
15893 @itemx info selectors @var{regexp}
15894 Display all Objective-C selectors in your program, or
15895 (with the @var{regexp} argument) all those matching a particular regular
15899 This was never implemented.
15900 @kindex info methods
15902 @itemx info methods @var{regexp}
15903 The @code{info methods} command permits the user to examine all defined
15904 methods within C@t{++} program, or (with the @var{regexp} argument) a
15905 specific set of methods found in the various C@t{++} classes. Many
15906 C@t{++} classes provide a large number of methods. Thus, the output
15907 from the @code{ptype} command can be overwhelming and hard to use. The
15908 @code{info-methods} command filters the methods, printing only those
15909 which match the regular-expression @var{regexp}.
15912 @cindex opaque data types
15913 @kindex set opaque-type-resolution
15914 @item set opaque-type-resolution on
15915 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15916 declared as a pointer to a @code{struct}, @code{class}, or
15917 @code{union}---for example, @code{struct MyType *}---that is used in one
15918 source file although the full declaration of @code{struct MyType} is in
15919 another source file. The default is on.
15921 A change in the setting of this subcommand will not take effect until
15922 the next time symbols for a file are loaded.
15924 @item set opaque-type-resolution off
15925 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15926 is printed as follows:
15928 @{<no data fields>@}
15931 @kindex show opaque-type-resolution
15932 @item show opaque-type-resolution
15933 Show whether opaque types are resolved or not.
15935 @kindex maint print symbols
15936 @cindex symbol dump
15937 @kindex maint print psymbols
15938 @cindex partial symbol dump
15939 @kindex maint print msymbols
15940 @cindex minimal symbol dump
15941 @item maint print symbols @var{filename}
15942 @itemx maint print psymbols @var{filename}
15943 @itemx maint print msymbols @var{filename}
15944 Write a dump of debugging symbol data into the file @var{filename}.
15945 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15946 symbols with debugging data are included. If you use @samp{maint print
15947 symbols}, @value{GDBN} includes all the symbols for which it has already
15948 collected full details: that is, @var{filename} reflects symbols for
15949 only those files whose symbols @value{GDBN} has read. You can use the
15950 command @code{info sources} to find out which files these are. If you
15951 use @samp{maint print psymbols} instead, the dump shows information about
15952 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15953 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15954 @samp{maint print msymbols} dumps just the minimal symbol information
15955 required for each object file from which @value{GDBN} has read some symbols.
15956 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15957 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15959 @kindex maint info symtabs
15960 @kindex maint info psymtabs
15961 @cindex listing @value{GDBN}'s internal symbol tables
15962 @cindex symbol tables, listing @value{GDBN}'s internal
15963 @cindex full symbol tables, listing @value{GDBN}'s internal
15964 @cindex partial symbol tables, listing @value{GDBN}'s internal
15965 @item maint info symtabs @r{[} @var{regexp} @r{]}
15966 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15968 List the @code{struct symtab} or @code{struct partial_symtab}
15969 structures whose names match @var{regexp}. If @var{regexp} is not
15970 given, list them all. The output includes expressions which you can
15971 copy into a @value{GDBN} debugging this one to examine a particular
15972 structure in more detail. For example:
15975 (@value{GDBP}) maint info psymtabs dwarf2read
15976 @{ objfile /home/gnu/build/gdb/gdb
15977 ((struct objfile *) 0x82e69d0)
15978 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15979 ((struct partial_symtab *) 0x8474b10)
15982 text addresses 0x814d3c8 -- 0x8158074
15983 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15984 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15985 dependencies (none)
15988 (@value{GDBP}) maint info symtabs
15992 We see that there is one partial symbol table whose filename contains
15993 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15994 and we see that @value{GDBN} has not read in any symtabs yet at all.
15995 If we set a breakpoint on a function, that will cause @value{GDBN} to
15996 read the symtab for the compilation unit containing that function:
15999 (@value{GDBP}) break dwarf2_psymtab_to_symtab
16000 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
16002 (@value{GDBP}) maint info symtabs
16003 @{ objfile /home/gnu/build/gdb/gdb
16004 ((struct objfile *) 0x82e69d0)
16005 @{ symtab /home/gnu/src/gdb/dwarf2read.c
16006 ((struct symtab *) 0x86c1f38)
16009 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
16010 linetable ((struct linetable *) 0x8370fa0)
16011 debugformat DWARF 2
16020 @chapter Altering Execution
16022 Once you think you have found an error in your program, you might want to
16023 find out for certain whether correcting the apparent error would lead to
16024 correct results in the rest of the run. You can find the answer by
16025 experiment, using the @value{GDBN} features for altering execution of the
16028 For example, you can store new values into variables or memory
16029 locations, give your program a signal, restart it at a different
16030 address, or even return prematurely from a function.
16033 * Assignment:: Assignment to variables
16034 * Jumping:: Continuing at a different address
16035 * Signaling:: Giving your program a signal
16036 * Returning:: Returning from a function
16037 * Calling:: Calling your program's functions
16038 * Patching:: Patching your program
16042 @section Assignment to Variables
16045 @cindex setting variables
16046 To alter the value of a variable, evaluate an assignment expression.
16047 @xref{Expressions, ,Expressions}. For example,
16054 stores the value 4 into the variable @code{x}, and then prints the
16055 value of the assignment expression (which is 4).
16056 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
16057 information on operators in supported languages.
16059 @kindex set variable
16060 @cindex variables, setting
16061 If you are not interested in seeing the value of the assignment, use the
16062 @code{set} command instead of the @code{print} command. @code{set} is
16063 really the same as @code{print} except that the expression's value is
16064 not printed and is not put in the value history (@pxref{Value History,
16065 ,Value History}). The expression is evaluated only for its effects.
16067 If the beginning of the argument string of the @code{set} command
16068 appears identical to a @code{set} subcommand, use the @code{set
16069 variable} command instead of just @code{set}. This command is identical
16070 to @code{set} except for its lack of subcommands. For example, if your
16071 program has a variable @code{width}, you get an error if you try to set
16072 a new value with just @samp{set width=13}, because @value{GDBN} has the
16073 command @code{set width}:
16076 (@value{GDBP}) whatis width
16078 (@value{GDBP}) p width
16080 (@value{GDBP}) set width=47
16081 Invalid syntax in expression.
16085 The invalid expression, of course, is @samp{=47}. In
16086 order to actually set the program's variable @code{width}, use
16089 (@value{GDBP}) set var width=47
16092 Because the @code{set} command has many subcommands that can conflict
16093 with the names of program variables, it is a good idea to use the
16094 @code{set variable} command instead of just @code{set}. For example, if
16095 your program has a variable @code{g}, you run into problems if you try
16096 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16097 the command @code{set gnutarget}, abbreviated @code{set g}:
16101 (@value{GDBP}) whatis g
16105 (@value{GDBP}) set g=4
16109 The program being debugged has been started already.
16110 Start it from the beginning? (y or n) y
16111 Starting program: /home/smith/cc_progs/a.out
16112 "/home/smith/cc_progs/a.out": can't open to read symbols:
16113 Invalid bfd target.
16114 (@value{GDBP}) show g
16115 The current BFD target is "=4".
16120 The program variable @code{g} did not change, and you silently set the
16121 @code{gnutarget} to an invalid value. In order to set the variable
16125 (@value{GDBP}) set var g=4
16128 @value{GDBN} allows more implicit conversions in assignments than C; you can
16129 freely store an integer value into a pointer variable or vice versa,
16130 and you can convert any structure to any other structure that is the
16131 same length or shorter.
16132 @comment FIXME: how do structs align/pad in these conversions?
16133 @comment /doc@cygnus.com 18dec1990
16135 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16136 construct to generate a value of specified type at a specified address
16137 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16138 to memory location @code{0x83040} as an integer (which implies a certain size
16139 and representation in memory), and
16142 set @{int@}0x83040 = 4
16146 stores the value 4 into that memory location.
16149 @section Continuing at a Different Address
16151 Ordinarily, when you continue your program, you do so at the place where
16152 it stopped, with the @code{continue} command. You can instead continue at
16153 an address of your own choosing, with the following commands:
16157 @kindex j @r{(@code{jump})}
16158 @item jump @var{linespec}
16159 @itemx j @var{linespec}
16160 @itemx jump @var{location}
16161 @itemx j @var{location}
16162 Resume execution at line @var{linespec} or at address given by
16163 @var{location}. Execution stops again immediately if there is a
16164 breakpoint there. @xref{Specify Location}, for a description of the
16165 different forms of @var{linespec} and @var{location}. It is common
16166 practice to use the @code{tbreak} command in conjunction with
16167 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16169 The @code{jump} command does not change the current stack frame, or
16170 the stack pointer, or the contents of any memory location or any
16171 register other than the program counter. If line @var{linespec} is in
16172 a different function from the one currently executing, the results may
16173 be bizarre if the two functions expect different patterns of arguments or
16174 of local variables. For this reason, the @code{jump} command requests
16175 confirmation if the specified line is not in the function currently
16176 executing. However, even bizarre results are predictable if you are
16177 well acquainted with the machine-language code of your program.
16180 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16181 On many systems, you can get much the same effect as the @code{jump}
16182 command by storing a new value into the register @code{$pc}. The
16183 difference is that this does not start your program running; it only
16184 changes the address of where it @emph{will} run when you continue. For
16192 makes the next @code{continue} command or stepping command execute at
16193 address @code{0x485}, rather than at the address where your program stopped.
16194 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16196 The most common occasion to use the @code{jump} command is to back
16197 up---perhaps with more breakpoints set---over a portion of a program
16198 that has already executed, in order to examine its execution in more
16203 @section Giving your Program a Signal
16204 @cindex deliver a signal to a program
16208 @item signal @var{signal}
16209 Resume execution where your program stopped, but immediately give it the
16210 signal @var{signal}. @var{signal} can be the name or the number of a
16211 signal. For example, on many systems @code{signal 2} and @code{signal
16212 SIGINT} are both ways of sending an interrupt signal.
16214 Alternatively, if @var{signal} is zero, continue execution without
16215 giving a signal. This is useful when your program stopped on account of
16216 a signal and would ordinarily see the signal when resumed with the
16217 @code{continue} command; @samp{signal 0} causes it to resume without a
16220 @code{signal} does not repeat when you press @key{RET} a second time
16221 after executing the command.
16225 Invoking the @code{signal} command is not the same as invoking the
16226 @code{kill} utility from the shell. Sending a signal with @code{kill}
16227 causes @value{GDBN} to decide what to do with the signal depending on
16228 the signal handling tables (@pxref{Signals}). The @code{signal} command
16229 passes the signal directly to your program.
16233 @section Returning from a Function
16236 @cindex returning from a function
16239 @itemx return @var{expression}
16240 You can cancel execution of a function call with the @code{return}
16241 command. If you give an
16242 @var{expression} argument, its value is used as the function's return
16246 When you use @code{return}, @value{GDBN} discards the selected stack frame
16247 (and all frames within it). You can think of this as making the
16248 discarded frame return prematurely. If you wish to specify a value to
16249 be returned, give that value as the argument to @code{return}.
16251 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16252 Frame}), and any other frames inside of it, leaving its caller as the
16253 innermost remaining frame. That frame becomes selected. The
16254 specified value is stored in the registers used for returning values
16257 The @code{return} command does not resume execution; it leaves the
16258 program stopped in the state that would exist if the function had just
16259 returned. In contrast, the @code{finish} command (@pxref{Continuing
16260 and Stepping, ,Continuing and Stepping}) resumes execution until the
16261 selected stack frame returns naturally.
16263 @value{GDBN} needs to know how the @var{expression} argument should be set for
16264 the inferior. The concrete registers assignment depends on the OS ABI and the
16265 type being returned by the selected stack frame. For example it is common for
16266 OS ABI to return floating point values in FPU registers while integer values in
16267 CPU registers. Still some ABIs return even floating point values in CPU
16268 registers. Larger integer widths (such as @code{long long int}) also have
16269 specific placement rules. @value{GDBN} already knows the OS ABI from its
16270 current target so it needs to find out also the type being returned to make the
16271 assignment into the right register(s).
16273 Normally, the selected stack frame has debug info. @value{GDBN} will always
16274 use the debug info instead of the implicit type of @var{expression} when the
16275 debug info is available. For example, if you type @kbd{return -1}, and the
16276 function in the current stack frame is declared to return a @code{long long
16277 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16278 into a @code{long long int}:
16281 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16283 (@value{GDBP}) return -1
16284 Make func return now? (y or n) y
16285 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16286 43 printf ("result=%lld\n", func ());
16290 However, if the selected stack frame does not have a debug info, e.g., if the
16291 function was compiled without debug info, @value{GDBN} has to find out the type
16292 to return from user. Specifying a different type by mistake may set the value
16293 in different inferior registers than the caller code expects. For example,
16294 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16295 of a @code{long long int} result for a debug info less function (on 32-bit
16296 architectures). Therefore the user is required to specify the return type by
16297 an appropriate cast explicitly:
16300 Breakpoint 2, 0x0040050b in func ()
16301 (@value{GDBP}) return -1
16302 Return value type not available for selected stack frame.
16303 Please use an explicit cast of the value to return.
16304 (@value{GDBP}) return (long long int) -1
16305 Make selected stack frame return now? (y or n) y
16306 #0 0x00400526 in main ()
16311 @section Calling Program Functions
16314 @cindex calling functions
16315 @cindex inferior functions, calling
16316 @item print @var{expr}
16317 Evaluate the expression @var{expr} and display the resulting value.
16318 @var{expr} may include calls to functions in the program being
16322 @item call @var{expr}
16323 Evaluate the expression @var{expr} without displaying @code{void}
16326 You can use this variant of the @code{print} command if you want to
16327 execute a function from your program that does not return anything
16328 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16329 with @code{void} returned values that @value{GDBN} will otherwise
16330 print. If the result is not void, it is printed and saved in the
16334 It is possible for the function you call via the @code{print} or
16335 @code{call} command to generate a signal (e.g., if there's a bug in
16336 the function, or if you passed it incorrect arguments). What happens
16337 in that case is controlled by the @code{set unwindonsignal} command.
16339 Similarly, with a C@t{++} program it is possible for the function you
16340 call via the @code{print} or @code{call} command to generate an
16341 exception that is not handled due to the constraints of the dummy
16342 frame. In this case, any exception that is raised in the frame, but has
16343 an out-of-frame exception handler will not be found. GDB builds a
16344 dummy-frame for the inferior function call, and the unwinder cannot
16345 seek for exception handlers outside of this dummy-frame. What happens
16346 in that case is controlled by the
16347 @code{set unwind-on-terminating-exception} command.
16350 @item set unwindonsignal
16351 @kindex set unwindonsignal
16352 @cindex unwind stack in called functions
16353 @cindex call dummy stack unwinding
16354 Set unwinding of the stack if a signal is received while in a function
16355 that @value{GDBN} called in the program being debugged. If set to on,
16356 @value{GDBN} unwinds the stack it created for the call and restores
16357 the context to what it was before the call. If set to off (the
16358 default), @value{GDBN} stops in the frame where the signal was
16361 @item show unwindonsignal
16362 @kindex show unwindonsignal
16363 Show the current setting of stack unwinding in the functions called by
16366 @item set unwind-on-terminating-exception
16367 @kindex set unwind-on-terminating-exception
16368 @cindex unwind stack in called functions with unhandled exceptions
16369 @cindex call dummy stack unwinding on unhandled exception.
16370 Set unwinding of the stack if a C@t{++} exception is raised, but left
16371 unhandled while in a function that @value{GDBN} called in the program being
16372 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16373 it created for the call and restores the context to what it was before
16374 the call. If set to off, @value{GDBN} the exception is delivered to
16375 the default C@t{++} exception handler and the inferior terminated.
16377 @item show unwind-on-terminating-exception
16378 @kindex show unwind-on-terminating-exception
16379 Show the current setting of stack unwinding in the functions called by
16384 @cindex weak alias functions
16385 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16386 for another function. In such case, @value{GDBN} might not pick up
16387 the type information, including the types of the function arguments,
16388 which causes @value{GDBN} to call the inferior function incorrectly.
16389 As a result, the called function will function erroneously and may
16390 even crash. A solution to that is to use the name of the aliased
16394 @section Patching Programs
16396 @cindex patching binaries
16397 @cindex writing into executables
16398 @cindex writing into corefiles
16400 By default, @value{GDBN} opens the file containing your program's
16401 executable code (or the corefile) read-only. This prevents accidental
16402 alterations to machine code; but it also prevents you from intentionally
16403 patching your program's binary.
16405 If you'd like to be able to patch the binary, you can specify that
16406 explicitly with the @code{set write} command. For example, you might
16407 want to turn on internal debugging flags, or even to make emergency
16413 @itemx set write off
16414 If you specify @samp{set write on}, @value{GDBN} opens executable and
16415 core files for both reading and writing; if you specify @kbd{set write
16416 off} (the default), @value{GDBN} opens them read-only.
16418 If you have already loaded a file, you must load it again (using the
16419 @code{exec-file} or @code{core-file} command) after changing @code{set
16420 write}, for your new setting to take effect.
16424 Display whether executable files and core files are opened for writing
16425 as well as reading.
16429 @chapter @value{GDBN} Files
16431 @value{GDBN} needs to know the file name of the program to be debugged,
16432 both in order to read its symbol table and in order to start your
16433 program. To debug a core dump of a previous run, you must also tell
16434 @value{GDBN} the name of the core dump file.
16437 * Files:: Commands to specify files
16438 * Separate Debug Files:: Debugging information in separate files
16439 * MiniDebugInfo:: Debugging information in a special section
16440 * Index Files:: Index files speed up GDB
16441 * Symbol Errors:: Errors reading symbol files
16442 * Data Files:: GDB data files
16446 @section Commands to Specify Files
16448 @cindex symbol table
16449 @cindex core dump file
16451 You may want to specify executable and core dump file names. The usual
16452 way to do this is at start-up time, using the arguments to
16453 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16454 Out of @value{GDBN}}).
16456 Occasionally it is necessary to change to a different file during a
16457 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16458 specify a file you want to use. Or you are debugging a remote target
16459 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16460 Program}). In these situations the @value{GDBN} commands to specify
16461 new files are useful.
16464 @cindex executable file
16466 @item file @var{filename}
16467 Use @var{filename} as the program to be debugged. It is read for its
16468 symbols and for the contents of pure memory. It is also the program
16469 executed when you use the @code{run} command. If you do not specify a
16470 directory and the file is not found in the @value{GDBN} working directory,
16471 @value{GDBN} uses the environment variable @code{PATH} as a list of
16472 directories to search, just as the shell does when looking for a program
16473 to run. You can change the value of this variable, for both @value{GDBN}
16474 and your program, using the @code{path} command.
16476 @cindex unlinked object files
16477 @cindex patching object files
16478 You can load unlinked object @file{.o} files into @value{GDBN} using
16479 the @code{file} command. You will not be able to ``run'' an object
16480 file, but you can disassemble functions and inspect variables. Also,
16481 if the underlying BFD functionality supports it, you could use
16482 @kbd{gdb -write} to patch object files using this technique. Note
16483 that @value{GDBN} can neither interpret nor modify relocations in this
16484 case, so branches and some initialized variables will appear to go to
16485 the wrong place. But this feature is still handy from time to time.
16488 @code{file} with no argument makes @value{GDBN} discard any information it
16489 has on both executable file and the symbol table.
16492 @item exec-file @r{[} @var{filename} @r{]}
16493 Specify that the program to be run (but not the symbol table) is found
16494 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16495 if necessary to locate your program. Omitting @var{filename} means to
16496 discard information on the executable file.
16498 @kindex symbol-file
16499 @item symbol-file @r{[} @var{filename} @r{]}
16500 Read symbol table information from file @var{filename}. @code{PATH} is
16501 searched when necessary. Use the @code{file} command to get both symbol
16502 table and program to run from the same file.
16504 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16505 program's symbol table.
16507 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16508 some breakpoints and auto-display expressions. This is because they may
16509 contain pointers to the internal data recording symbols and data types,
16510 which are part of the old symbol table data being discarded inside
16513 @code{symbol-file} does not repeat if you press @key{RET} again after
16516 When @value{GDBN} is configured for a particular environment, it
16517 understands debugging information in whatever format is the standard
16518 generated for that environment; you may use either a @sc{gnu} compiler, or
16519 other compilers that adhere to the local conventions.
16520 Best results are usually obtained from @sc{gnu} compilers; for example,
16521 using @code{@value{NGCC}} you can generate debugging information for
16524 For most kinds of object files, with the exception of old SVR3 systems
16525 using COFF, the @code{symbol-file} command does not normally read the
16526 symbol table in full right away. Instead, it scans the symbol table
16527 quickly to find which source files and which symbols are present. The
16528 details are read later, one source file at a time, as they are needed.
16530 The purpose of this two-stage reading strategy is to make @value{GDBN}
16531 start up faster. For the most part, it is invisible except for
16532 occasional pauses while the symbol table details for a particular source
16533 file are being read. (The @code{set verbose} command can turn these
16534 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16535 Warnings and Messages}.)
16537 We have not implemented the two-stage strategy for COFF yet. When the
16538 symbol table is stored in COFF format, @code{symbol-file} reads the
16539 symbol table data in full right away. Note that ``stabs-in-COFF''
16540 still does the two-stage strategy, since the debug info is actually
16544 @cindex reading symbols immediately
16545 @cindex symbols, reading immediately
16546 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16547 @itemx file @r{[} -readnow @r{]} @var{filename}
16548 You can override the @value{GDBN} two-stage strategy for reading symbol
16549 tables by using the @samp{-readnow} option with any of the commands that
16550 load symbol table information, if you want to be sure @value{GDBN} has the
16551 entire symbol table available.
16553 @c FIXME: for now no mention of directories, since this seems to be in
16554 @c flux. 13mar1992 status is that in theory GDB would look either in
16555 @c current dir or in same dir as myprog; but issues like competing
16556 @c GDB's, or clutter in system dirs, mean that in practice right now
16557 @c only current dir is used. FFish says maybe a special GDB hierarchy
16558 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16562 @item core-file @r{[}@var{filename}@r{]}
16564 Specify the whereabouts of a core dump file to be used as the ``contents
16565 of memory''. Traditionally, core files contain only some parts of the
16566 address space of the process that generated them; @value{GDBN} can access the
16567 executable file itself for other parts.
16569 @code{core-file} with no argument specifies that no core file is
16572 Note that the core file is ignored when your program is actually running
16573 under @value{GDBN}. So, if you have been running your program and you
16574 wish to debug a core file instead, you must kill the subprocess in which
16575 the program is running. To do this, use the @code{kill} command
16576 (@pxref{Kill Process, ,Killing the Child Process}).
16578 @kindex add-symbol-file
16579 @cindex dynamic linking
16580 @item add-symbol-file @var{filename} @var{address}
16581 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16582 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16583 The @code{add-symbol-file} command reads additional symbol table
16584 information from the file @var{filename}. You would use this command
16585 when @var{filename} has been dynamically loaded (by some other means)
16586 into the program that is running. @var{address} should be the memory
16587 address at which the file has been loaded; @value{GDBN} cannot figure
16588 this out for itself. You can additionally specify an arbitrary number
16589 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16590 section name and base address for that section. You can specify any
16591 @var{address} as an expression.
16593 The symbol table of the file @var{filename} is added to the symbol table
16594 originally read with the @code{symbol-file} command. You can use the
16595 @code{add-symbol-file} command any number of times; the new symbol data
16596 thus read keeps adding to the old. To discard all old symbol data
16597 instead, use the @code{symbol-file} command without any arguments.
16599 @cindex relocatable object files, reading symbols from
16600 @cindex object files, relocatable, reading symbols from
16601 @cindex reading symbols from relocatable object files
16602 @cindex symbols, reading from relocatable object files
16603 @cindex @file{.o} files, reading symbols from
16604 Although @var{filename} is typically a shared library file, an
16605 executable file, or some other object file which has been fully
16606 relocated for loading into a process, you can also load symbolic
16607 information from relocatable @file{.o} files, as long as:
16611 the file's symbolic information refers only to linker symbols defined in
16612 that file, not to symbols defined by other object files,
16614 every section the file's symbolic information refers to has actually
16615 been loaded into the inferior, as it appears in the file, and
16617 you can determine the address at which every section was loaded, and
16618 provide these to the @code{add-symbol-file} command.
16622 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16623 relocatable files into an already running program; such systems
16624 typically make the requirements above easy to meet. However, it's
16625 important to recognize that many native systems use complex link
16626 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16627 assembly, for example) that make the requirements difficult to meet. In
16628 general, one cannot assume that using @code{add-symbol-file} to read a
16629 relocatable object file's symbolic information will have the same effect
16630 as linking the relocatable object file into the program in the normal
16633 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16635 @kindex add-symbol-file-from-memory
16636 @cindex @code{syscall DSO}
16637 @cindex load symbols from memory
16638 @item add-symbol-file-from-memory @var{address}
16639 Load symbols from the given @var{address} in a dynamically loaded
16640 object file whose image is mapped directly into the inferior's memory.
16641 For example, the Linux kernel maps a @code{syscall DSO} into each
16642 process's address space; this DSO provides kernel-specific code for
16643 some system calls. The argument can be any expression whose
16644 evaluation yields the address of the file's shared object file header.
16645 For this command to work, you must have used @code{symbol-file} or
16646 @code{exec-file} commands in advance.
16648 @kindex add-shared-symbol-files
16650 @item add-shared-symbol-files @var{library-file}
16651 @itemx assf @var{library-file}
16652 The @code{add-shared-symbol-files} command can currently be used only
16653 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16654 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16655 @value{GDBN} automatically looks for shared libraries, however if
16656 @value{GDBN} does not find yours, you can invoke
16657 @code{add-shared-symbol-files}. It takes one argument: the shared
16658 library's file name. @code{assf} is a shorthand alias for
16659 @code{add-shared-symbol-files}.
16662 @item section @var{section} @var{addr}
16663 The @code{section} command changes the base address of the named
16664 @var{section} of the exec file to @var{addr}. This can be used if the
16665 exec file does not contain section addresses, (such as in the
16666 @code{a.out} format), or when the addresses specified in the file
16667 itself are wrong. Each section must be changed separately. The
16668 @code{info files} command, described below, lists all the sections and
16672 @kindex info target
16675 @code{info files} and @code{info target} are synonymous; both print the
16676 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16677 including the names of the executable and core dump files currently in
16678 use by @value{GDBN}, and the files from which symbols were loaded. The
16679 command @code{help target} lists all possible targets rather than
16682 @kindex maint info sections
16683 @item maint info sections
16684 Another command that can give you extra information about program sections
16685 is @code{maint info sections}. In addition to the section information
16686 displayed by @code{info files}, this command displays the flags and file
16687 offset of each section in the executable and core dump files. In addition,
16688 @code{maint info sections} provides the following command options (which
16689 may be arbitrarily combined):
16693 Display sections for all loaded object files, including shared libraries.
16694 @item @var{sections}
16695 Display info only for named @var{sections}.
16696 @item @var{section-flags}
16697 Display info only for sections for which @var{section-flags} are true.
16698 The section flags that @value{GDBN} currently knows about are:
16701 Section will have space allocated in the process when loaded.
16702 Set for all sections except those containing debug information.
16704 Section will be loaded from the file into the child process memory.
16705 Set for pre-initialized code and data, clear for @code{.bss} sections.
16707 Section needs to be relocated before loading.
16709 Section cannot be modified by the child process.
16711 Section contains executable code only.
16713 Section contains data only (no executable code).
16715 Section will reside in ROM.
16717 Section contains data for constructor/destructor lists.
16719 Section is not empty.
16721 An instruction to the linker to not output the section.
16722 @item COFF_SHARED_LIBRARY
16723 A notification to the linker that the section contains
16724 COFF shared library information.
16726 Section contains common symbols.
16729 @kindex set trust-readonly-sections
16730 @cindex read-only sections
16731 @item set trust-readonly-sections on
16732 Tell @value{GDBN} that readonly sections in your object file
16733 really are read-only (i.e.@: that their contents will not change).
16734 In that case, @value{GDBN} can fetch values from these sections
16735 out of the object file, rather than from the target program.
16736 For some targets (notably embedded ones), this can be a significant
16737 enhancement to debugging performance.
16739 The default is off.
16741 @item set trust-readonly-sections off
16742 Tell @value{GDBN} not to trust readonly sections. This means that
16743 the contents of the section might change while the program is running,
16744 and must therefore be fetched from the target when needed.
16746 @item show trust-readonly-sections
16747 Show the current setting of trusting readonly sections.
16750 All file-specifying commands allow both absolute and relative file names
16751 as arguments. @value{GDBN} always converts the file name to an absolute file
16752 name and remembers it that way.
16754 @cindex shared libraries
16755 @anchor{Shared Libraries}
16756 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16757 and IBM RS/6000 AIX shared libraries.
16759 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16760 shared libraries. @xref{Expat}.
16762 @value{GDBN} automatically loads symbol definitions from shared libraries
16763 when you use the @code{run} command, or when you examine a core file.
16764 (Before you issue the @code{run} command, @value{GDBN} does not understand
16765 references to a function in a shared library, however---unless you are
16766 debugging a core file).
16768 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16769 automatically loads the symbols at the time of the @code{shl_load} call.
16771 @c FIXME: some @value{GDBN} release may permit some refs to undef
16772 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16773 @c FIXME...lib; check this from time to time when updating manual
16775 There are times, however, when you may wish to not automatically load
16776 symbol definitions from shared libraries, such as when they are
16777 particularly large or there are many of them.
16779 To control the automatic loading of shared library symbols, use the
16783 @kindex set auto-solib-add
16784 @item set auto-solib-add @var{mode}
16785 If @var{mode} is @code{on}, symbols from all shared object libraries
16786 will be loaded automatically when the inferior begins execution, you
16787 attach to an independently started inferior, or when the dynamic linker
16788 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16789 is @code{off}, symbols must be loaded manually, using the
16790 @code{sharedlibrary} command. The default value is @code{on}.
16792 @cindex memory used for symbol tables
16793 If your program uses lots of shared libraries with debug info that
16794 takes large amounts of memory, you can decrease the @value{GDBN}
16795 memory footprint by preventing it from automatically loading the
16796 symbols from shared libraries. To that end, type @kbd{set
16797 auto-solib-add off} before running the inferior, then load each
16798 library whose debug symbols you do need with @kbd{sharedlibrary
16799 @var{regexp}}, where @var{regexp} is a regular expression that matches
16800 the libraries whose symbols you want to be loaded.
16802 @kindex show auto-solib-add
16803 @item show auto-solib-add
16804 Display the current autoloading mode.
16807 @cindex load shared library
16808 To explicitly load shared library symbols, use the @code{sharedlibrary}
16812 @kindex info sharedlibrary
16814 @item info share @var{regex}
16815 @itemx info sharedlibrary @var{regex}
16816 Print the names of the shared libraries which are currently loaded
16817 that match @var{regex}. If @var{regex} is omitted then print
16818 all shared libraries that are loaded.
16820 @kindex sharedlibrary
16822 @item sharedlibrary @var{regex}
16823 @itemx share @var{regex}
16824 Load shared object library symbols for files matching a
16825 Unix regular expression.
16826 As with files loaded automatically, it only loads shared libraries
16827 required by your program for a core file or after typing @code{run}. If
16828 @var{regex} is omitted all shared libraries required by your program are
16831 @item nosharedlibrary
16832 @kindex nosharedlibrary
16833 @cindex unload symbols from shared libraries
16834 Unload all shared object library symbols. This discards all symbols
16835 that have been loaded from all shared libraries. Symbols from shared
16836 libraries that were loaded by explicit user requests are not
16840 Sometimes you may wish that @value{GDBN} stops and gives you control
16841 when any of shared library events happen. The best way to do this is
16842 to use @code{catch load} and @code{catch unload} (@pxref{Set
16845 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16846 command for this. This command exists for historical reasons. It is
16847 less useful than setting a catchpoint, because it does not allow for
16848 conditions or commands as a catchpoint does.
16851 @item set stop-on-solib-events
16852 @kindex set stop-on-solib-events
16853 This command controls whether @value{GDBN} should give you control
16854 when the dynamic linker notifies it about some shared library event.
16855 The most common event of interest is loading or unloading of a new
16858 @item show stop-on-solib-events
16859 @kindex show stop-on-solib-events
16860 Show whether @value{GDBN} stops and gives you control when shared
16861 library events happen.
16864 Shared libraries are also supported in many cross or remote debugging
16865 configurations. @value{GDBN} needs to have access to the target's libraries;
16866 this can be accomplished either by providing copies of the libraries
16867 on the host system, or by asking @value{GDBN} to automatically retrieve the
16868 libraries from the target. If copies of the target libraries are
16869 provided, they need to be the same as the target libraries, although the
16870 copies on the target can be stripped as long as the copies on the host are
16873 @cindex where to look for shared libraries
16874 For remote debugging, you need to tell @value{GDBN} where the target
16875 libraries are, so that it can load the correct copies---otherwise, it
16876 may try to load the host's libraries. @value{GDBN} has two variables
16877 to specify the search directories for target libraries.
16880 @cindex prefix for shared library file names
16881 @cindex system root, alternate
16882 @kindex set solib-absolute-prefix
16883 @kindex set sysroot
16884 @item set sysroot @var{path}
16885 Use @var{path} as the system root for the program being debugged. Any
16886 absolute shared library paths will be prefixed with @var{path}; many
16887 runtime loaders store the absolute paths to the shared library in the
16888 target program's memory. If you use @code{set sysroot} to find shared
16889 libraries, they need to be laid out in the same way that they are on
16890 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16893 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16894 retrieve the target libraries from the remote system. This is only
16895 supported when using a remote target that supports the @code{remote get}
16896 command (@pxref{File Transfer,,Sending files to a remote system}).
16897 The part of @var{path} following the initial @file{remote:}
16898 (if present) is used as system root prefix on the remote file system.
16899 @footnote{If you want to specify a local system root using a directory
16900 that happens to be named @file{remote:}, you need to use some equivalent
16901 variant of the name like @file{./remote:}.}
16903 For targets with an MS-DOS based filesystem, such as MS-Windows and
16904 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16905 absolute file name with @var{path}. But first, on Unix hosts,
16906 @value{GDBN} converts all backslash directory separators into forward
16907 slashes, because the backslash is not a directory separator on Unix:
16910 c:\foo\bar.dll @result{} c:/foo/bar.dll
16913 Then, @value{GDBN} attempts prefixing the target file name with
16914 @var{path}, and looks for the resulting file name in the host file
16918 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16921 If that does not find the shared library, @value{GDBN} tries removing
16922 the @samp{:} character from the drive spec, both for convenience, and,
16923 for the case of the host file system not supporting file names with
16927 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16930 This makes it possible to have a system root that mirrors a target
16931 with more than one drive. E.g., you may want to setup your local
16932 copies of the target system shared libraries like so (note @samp{c} vs
16936 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16937 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16938 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16942 and point the system root at @file{/path/to/sysroot}, so that
16943 @value{GDBN} can find the correct copies of both
16944 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16946 If that still does not find the shared library, @value{GDBN} tries
16947 removing the whole drive spec from the target file name:
16950 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16953 This last lookup makes it possible to not care about the drive name,
16954 if you don't want or need to.
16956 The @code{set solib-absolute-prefix} command is an alias for @code{set
16959 @cindex default system root
16960 @cindex @samp{--with-sysroot}
16961 You can set the default system root by using the configure-time
16962 @samp{--with-sysroot} option. If the system root is inside
16963 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16964 @samp{--exec-prefix}), then the default system root will be updated
16965 automatically if the installed @value{GDBN} is moved to a new
16968 @kindex show sysroot
16970 Display the current shared library prefix.
16972 @kindex set solib-search-path
16973 @item set solib-search-path @var{path}
16974 If this variable is set, @var{path} is a colon-separated list of
16975 directories to search for shared libraries. @samp{solib-search-path}
16976 is used after @samp{sysroot} fails to locate the library, or if the
16977 path to the library is relative instead of absolute. If you want to
16978 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16979 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16980 finding your host's libraries. @samp{sysroot} is preferred; setting
16981 it to a nonexistent directory may interfere with automatic loading
16982 of shared library symbols.
16984 @kindex show solib-search-path
16985 @item show solib-search-path
16986 Display the current shared library search path.
16988 @cindex DOS file-name semantics of file names.
16989 @kindex set target-file-system-kind (unix|dos-based|auto)
16990 @kindex show target-file-system-kind
16991 @item set target-file-system-kind @var{kind}
16992 Set assumed file system kind for target reported file names.
16994 Shared library file names as reported by the target system may not
16995 make sense as is on the system @value{GDBN} is running on. For
16996 example, when remote debugging a target that has MS-DOS based file
16997 system semantics, from a Unix host, the target may be reporting to
16998 @value{GDBN} a list of loaded shared libraries with file names such as
16999 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
17000 drive letters, so the @samp{c:\} prefix is not normally understood as
17001 indicating an absolute file name, and neither is the backslash
17002 normally considered a directory separator character. In that case,
17003 the native file system would interpret this whole absolute file name
17004 as a relative file name with no directory components. This would make
17005 it impossible to point @value{GDBN} at a copy of the remote target's
17006 shared libraries on the host using @code{set sysroot}, and impractical
17007 with @code{set solib-search-path}. Setting
17008 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
17009 to interpret such file names similarly to how the target would, and to
17010 map them to file names valid on @value{GDBN}'s native file system
17011 semantics. The value of @var{kind} can be @code{"auto"}, in addition
17012 to one of the supported file system kinds. In that case, @value{GDBN}
17013 tries to determine the appropriate file system variant based on the
17014 current target's operating system (@pxref{ABI, ,Configuring the
17015 Current ABI}). The supported file system settings are:
17019 Instruct @value{GDBN} to assume the target file system is of Unix
17020 kind. Only file names starting the forward slash (@samp{/}) character
17021 are considered absolute, and the directory separator character is also
17025 Instruct @value{GDBN} to assume the target file system is DOS based.
17026 File names starting with either a forward slash, or a drive letter
17027 followed by a colon (e.g., @samp{c:}), are considered absolute, and
17028 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
17029 considered directory separators.
17032 Instruct @value{GDBN} to use the file system kind associated with the
17033 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
17034 This is the default.
17038 @cindex file name canonicalization
17039 @cindex base name differences
17040 When processing file names provided by the user, @value{GDBN}
17041 frequently needs to compare them to the file names recorded in the
17042 program's debug info. Normally, @value{GDBN} compares just the
17043 @dfn{base names} of the files as strings, which is reasonably fast
17044 even for very large programs. (The base name of a file is the last
17045 portion of its name, after stripping all the leading directories.)
17046 This shortcut in comparison is based upon the assumption that files
17047 cannot have more than one base name. This is usually true, but
17048 references to files that use symlinks or similar filesystem
17049 facilities violate that assumption. If your program records files
17050 using such facilities, or if you provide file names to @value{GDBN}
17051 using symlinks etc., you can set @code{basenames-may-differ} to
17052 @code{true} to instruct @value{GDBN} to completely canonicalize each
17053 pair of file names it needs to compare. This will make file-name
17054 comparisons accurate, but at a price of a significant slowdown.
17057 @item set basenames-may-differ
17058 @kindex set basenames-may-differ
17059 Set whether a source file may have multiple base names.
17061 @item show basenames-may-differ
17062 @kindex show basenames-may-differ
17063 Show whether a source file may have multiple base names.
17066 @node Separate Debug Files
17067 @section Debugging Information in Separate Files
17068 @cindex separate debugging information files
17069 @cindex debugging information in separate files
17070 @cindex @file{.debug} subdirectories
17071 @cindex debugging information directory, global
17072 @cindex global debugging information directories
17073 @cindex build ID, and separate debugging files
17074 @cindex @file{.build-id} directory
17076 @value{GDBN} allows you to put a program's debugging information in a
17077 file separate from the executable itself, in a way that allows
17078 @value{GDBN} to find and load the debugging information automatically.
17079 Since debugging information can be very large---sometimes larger
17080 than the executable code itself---some systems distribute debugging
17081 information for their executables in separate files, which users can
17082 install only when they need to debug a problem.
17084 @value{GDBN} supports two ways of specifying the separate debug info
17089 The executable contains a @dfn{debug link} that specifies the name of
17090 the separate debug info file. The separate debug file's name is
17091 usually @file{@var{executable}.debug}, where @var{executable} is the
17092 name of the corresponding executable file without leading directories
17093 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17094 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17095 checksum for the debug file, which @value{GDBN} uses to validate that
17096 the executable and the debug file came from the same build.
17099 The executable contains a @dfn{build ID}, a unique bit string that is
17100 also present in the corresponding debug info file. (This is supported
17101 only on some operating systems, notably those which use the ELF format
17102 for binary files and the @sc{gnu} Binutils.) For more details about
17103 this feature, see the description of the @option{--build-id}
17104 command-line option in @ref{Options, , Command Line Options, ld.info,
17105 The GNU Linker}. The debug info file's name is not specified
17106 explicitly by the build ID, but can be computed from the build ID, see
17110 Depending on the way the debug info file is specified, @value{GDBN}
17111 uses two different methods of looking for the debug file:
17115 For the ``debug link'' method, @value{GDBN} looks up the named file in
17116 the directory of the executable file, then in a subdirectory of that
17117 directory named @file{.debug}, and finally under each one of the global debug
17118 directories, in a subdirectory whose name is identical to the leading
17119 directories of the executable's absolute file name.
17122 For the ``build ID'' method, @value{GDBN} looks in the
17123 @file{.build-id} subdirectory of each one of the global debug directories for
17124 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17125 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17126 are the rest of the bit string. (Real build ID strings are 32 or more
17127 hex characters, not 10.)
17130 So, for example, suppose you ask @value{GDBN} to debug
17131 @file{/usr/bin/ls}, which has a debug link that specifies the
17132 file @file{ls.debug}, and a build ID whose value in hex is
17133 @code{abcdef1234}. If the list of the global debug directories includes
17134 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17135 debug information files, in the indicated order:
17139 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17141 @file{/usr/bin/ls.debug}
17143 @file{/usr/bin/.debug/ls.debug}
17145 @file{/usr/lib/debug/usr/bin/ls.debug}.
17148 @anchor{debug-file-directory}
17149 Global debugging info directories default to what is set by @value{GDBN}
17150 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17151 you can also set the global debugging info directories, and view the list
17152 @value{GDBN} is currently using.
17156 @kindex set debug-file-directory
17157 @item set debug-file-directory @var{directories}
17158 Set the directories which @value{GDBN} searches for separate debugging
17159 information files to @var{directory}. Multiple path components can be set
17160 concatenating them by a path separator.
17162 @kindex show debug-file-directory
17163 @item show debug-file-directory
17164 Show the directories @value{GDBN} searches for separate debugging
17169 @cindex @code{.gnu_debuglink} sections
17170 @cindex debug link sections
17171 A debug link is a special section of the executable file named
17172 @code{.gnu_debuglink}. The section must contain:
17176 A filename, with any leading directory components removed, followed by
17179 zero to three bytes of padding, as needed to reach the next four-byte
17180 boundary within the section, and
17182 a four-byte CRC checksum, stored in the same endianness used for the
17183 executable file itself. The checksum is computed on the debugging
17184 information file's full contents by the function given below, passing
17185 zero as the @var{crc} argument.
17188 Any executable file format can carry a debug link, as long as it can
17189 contain a section named @code{.gnu_debuglink} with the contents
17192 @cindex @code{.note.gnu.build-id} sections
17193 @cindex build ID sections
17194 The build ID is a special section in the executable file (and in other
17195 ELF binary files that @value{GDBN} may consider). This section is
17196 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17197 It contains unique identification for the built files---the ID remains
17198 the same across multiple builds of the same build tree. The default
17199 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17200 content for the build ID string. The same section with an identical
17201 value is present in the original built binary with symbols, in its
17202 stripped variant, and in the separate debugging information file.
17204 The debugging information file itself should be an ordinary
17205 executable, containing a full set of linker symbols, sections, and
17206 debugging information. The sections of the debugging information file
17207 should have the same names, addresses, and sizes as the original file,
17208 but they need not contain any data---much like a @code{.bss} section
17209 in an ordinary executable.
17211 The @sc{gnu} binary utilities (Binutils) package includes the
17212 @samp{objcopy} utility that can produce
17213 the separated executable / debugging information file pairs using the
17214 following commands:
17217 @kbd{objcopy --only-keep-debug foo foo.debug}
17222 These commands remove the debugging
17223 information from the executable file @file{foo} and place it in the file
17224 @file{foo.debug}. You can use the first, second or both methods to link the
17229 The debug link method needs the following additional command to also leave
17230 behind a debug link in @file{foo}:
17233 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17236 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17237 a version of the @code{strip} command such that the command @kbd{strip foo -f
17238 foo.debug} has the same functionality as the two @code{objcopy} commands and
17239 the @code{ln -s} command above, together.
17242 Build ID gets embedded into the main executable using @code{ld --build-id} or
17243 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17244 compatibility fixes for debug files separation are present in @sc{gnu} binary
17245 utilities (Binutils) package since version 2.18.
17250 @cindex CRC algorithm definition
17251 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17252 IEEE 802.3 using the polynomial:
17254 @c TexInfo requires naked braces for multi-digit exponents for Tex
17255 @c output, but this causes HTML output to barf. HTML has to be set using
17256 @c raw commands. So we end up having to specify this equation in 2
17261 <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>
17262 + <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
17268 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17269 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17273 The function is computed byte at a time, taking the least
17274 significant bit of each byte first. The initial pattern
17275 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17276 the final result is inverted to ensure trailing zeros also affect the
17279 @emph{Note:} This is the same CRC polynomial as used in handling the
17280 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17281 , @value{GDBN} Remote Serial Protocol}). However in the
17282 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17283 significant bit first, and the result is not inverted, so trailing
17284 zeros have no effect on the CRC value.
17286 To complete the description, we show below the code of the function
17287 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17288 initially supplied @code{crc} argument means that an initial call to
17289 this function passing in zero will start computing the CRC using
17292 @kindex gnu_debuglink_crc32
17295 gnu_debuglink_crc32 (unsigned long crc,
17296 unsigned char *buf, size_t len)
17298 static const unsigned long crc32_table[256] =
17300 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17301 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17302 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17303 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17304 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17305 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17306 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17307 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17308 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17309 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17310 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17311 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17312 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17313 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17314 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17315 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17316 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17317 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17318 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17319 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17320 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17321 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17322 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17323 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17324 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17325 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17326 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17327 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17328 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17329 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17330 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17331 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17332 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17333 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17334 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17335 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17336 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17337 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17338 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17339 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17340 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17341 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17342 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17343 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17344 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17345 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17346 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17347 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17348 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17349 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17350 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17353 unsigned char *end;
17355 crc = ~crc & 0xffffffff;
17356 for (end = buf + len; buf < end; ++buf)
17357 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17358 return ~crc & 0xffffffff;
17363 This computation does not apply to the ``build ID'' method.
17365 @node MiniDebugInfo
17366 @section Debugging information in a special section
17367 @cindex separate debug sections
17368 @cindex @samp{.gnu_debugdata} section
17370 Some systems ship pre-built executables and libraries that have a
17371 special @samp{.gnu_debugdata} section. This feature is called
17372 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17373 is used to supply extra symbols for backtraces.
17375 The intent of this section is to provide extra minimal debugging
17376 information for use in simple backtraces. It is not intended to be a
17377 replacement for full separate debugging information (@pxref{Separate
17378 Debug Files}). The example below shows the intended use; however,
17379 @value{GDBN} does not currently put restrictions on what sort of
17380 debugging information might be included in the section.
17382 @value{GDBN} has support for this extension. If the section exists,
17383 then it is used provided that no other source of debugging information
17384 can be found, and that @value{GDBN} was configured with LZMA support.
17386 This section can be easily created using @command{objcopy} and other
17387 standard utilities:
17390 # Extract the dynamic symbols from the main binary, there is no need
17391 # to also have these in the normal symbol table.
17392 nm -D @var{binary} --format=posix --defined-only \
17393 | awk '@{ print $1 @}' | sort > dynsyms
17395 # Extract all the text (i.e. function) symbols from the debuginfo.
17396 # (Note that we actually also accept "D" symbols, for the benefit
17397 # of platforms like PowerPC64 that use function descriptors.)
17398 nm @var{binary} --format=posix --defined-only \
17399 | awk '@{ if ($2 == "T" || $2 == "t" || $2 == "D") print $1 @}' \
17402 # Keep all the function symbols not already in the dynamic symbol
17404 comm -13 dynsyms funcsyms > keep_symbols
17406 # Separate full debug info into debug binary.
17407 objcopy --only-keep-debug @var{binary} debug
17409 # Copy the full debuginfo, keeping only a minimal set of symbols and
17410 # removing some unnecessary sections.
17411 objcopy -S --remove-section .gdb_index --remove-section .comment \
17412 --keep-symbols=keep_symbols debug mini_debuginfo
17414 # Drop the full debug info from the original binary.
17415 strip --strip-all -R .comment @var{binary}
17417 # Inject the compressed data into the .gnu_debugdata section of the
17420 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17424 @section Index Files Speed Up @value{GDBN}
17425 @cindex index files
17426 @cindex @samp{.gdb_index} section
17428 When @value{GDBN} finds a symbol file, it scans the symbols in the
17429 file in order to construct an internal symbol table. This lets most
17430 @value{GDBN} operations work quickly---at the cost of a delay early
17431 on. For large programs, this delay can be quite lengthy, so
17432 @value{GDBN} provides a way to build an index, which speeds up
17435 The index is stored as a section in the symbol file. @value{GDBN} can
17436 write the index to a file, then you can put it into the symbol file
17437 using @command{objcopy}.
17439 To create an index file, use the @code{save gdb-index} command:
17442 @item save gdb-index @var{directory}
17443 @kindex save gdb-index
17444 Create an index file for each symbol file currently known by
17445 @value{GDBN}. Each file is named after its corresponding symbol file,
17446 with @samp{.gdb-index} appended, and is written into the given
17450 Once you have created an index file you can merge it into your symbol
17451 file, here named @file{symfile}, using @command{objcopy}:
17454 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17455 --set-section-flags .gdb_index=readonly symfile symfile
17458 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17459 sections that have been deprecated. Usually they are deprecated because
17460 they are missing a new feature or have performance issues.
17461 To tell @value{GDBN} to use a deprecated index section anyway
17462 specify @code{set use-deprecated-index-sections on}.
17463 The default is @code{off}.
17464 This can speed up startup, but may result in some functionality being lost.
17465 @xref{Index Section Format}.
17467 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17468 must be done before gdb reads the file. The following will not work:
17471 $ gdb -ex "set use-deprecated-index-sections on" <program>
17474 Instead you must do, for example,
17477 $ gdb -iex "set use-deprecated-index-sections on" <program>
17480 There are currently some limitation on indices. They only work when
17481 for DWARF debugging information, not stabs. And, they do not
17482 currently work for programs using Ada.
17484 @node Symbol Errors
17485 @section Errors Reading Symbol Files
17487 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17488 such as symbol types it does not recognize, or known bugs in compiler
17489 output. By default, @value{GDBN} does not notify you of such problems, since
17490 they are relatively common and primarily of interest to people
17491 debugging compilers. If you are interested in seeing information
17492 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17493 only one message about each such type of problem, no matter how many
17494 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17495 to see how many times the problems occur, with the @code{set
17496 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17499 The messages currently printed, and their meanings, include:
17502 @item inner block not inside outer block in @var{symbol}
17504 The symbol information shows where symbol scopes begin and end
17505 (such as at the start of a function or a block of statements). This
17506 error indicates that an inner scope block is not fully contained
17507 in its outer scope blocks.
17509 @value{GDBN} circumvents the problem by treating the inner block as if it had
17510 the same scope as the outer block. In the error message, @var{symbol}
17511 may be shown as ``@code{(don't know)}'' if the outer block is not a
17514 @item block at @var{address} out of order
17516 The symbol information for symbol scope blocks should occur in
17517 order of increasing addresses. This error indicates that it does not
17520 @value{GDBN} does not circumvent this problem, and has trouble
17521 locating symbols in the source file whose symbols it is reading. (You
17522 can often determine what source file is affected by specifying
17523 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17526 @item bad block start address patched
17528 The symbol information for a symbol scope block has a start address
17529 smaller than the address of the preceding source line. This is known
17530 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17532 @value{GDBN} circumvents the problem by treating the symbol scope block as
17533 starting on the previous source line.
17535 @item bad string table offset in symbol @var{n}
17538 Symbol number @var{n} contains a pointer into the string table which is
17539 larger than the size of the string table.
17541 @value{GDBN} circumvents the problem by considering the symbol to have the
17542 name @code{foo}, which may cause other problems if many symbols end up
17545 @item unknown symbol type @code{0x@var{nn}}
17547 The symbol information contains new data types that @value{GDBN} does
17548 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17549 uncomprehended information, in hexadecimal.
17551 @value{GDBN} circumvents the error by ignoring this symbol information.
17552 This usually allows you to debug your program, though certain symbols
17553 are not accessible. If you encounter such a problem and feel like
17554 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17555 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17556 and examine @code{*bufp} to see the symbol.
17558 @item stub type has NULL name
17560 @value{GDBN} could not find the full definition for a struct or class.
17562 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17563 The symbol information for a C@t{++} member function is missing some
17564 information that recent versions of the compiler should have output for
17567 @item info mismatch between compiler and debugger
17569 @value{GDBN} could not parse a type specification output by the compiler.
17574 @section GDB Data Files
17576 @cindex prefix for data files
17577 @value{GDBN} will sometimes read an auxiliary data file. These files
17578 are kept in a directory known as the @dfn{data directory}.
17580 You can set the data directory's name, and view the name @value{GDBN}
17581 is currently using.
17584 @kindex set data-directory
17585 @item set data-directory @var{directory}
17586 Set the directory which @value{GDBN} searches for auxiliary data files
17587 to @var{directory}.
17589 @kindex show data-directory
17590 @item show data-directory
17591 Show the directory @value{GDBN} searches for auxiliary data files.
17594 @cindex default data directory
17595 @cindex @samp{--with-gdb-datadir}
17596 You can set the default data directory by using the configure-time
17597 @samp{--with-gdb-datadir} option. If the data directory is inside
17598 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17599 @samp{--exec-prefix}), then the default data directory will be updated
17600 automatically if the installed @value{GDBN} is moved to a new
17603 The data directory may also be specified with the
17604 @code{--data-directory} command line option.
17605 @xref{Mode Options}.
17608 @chapter Specifying a Debugging Target
17610 @cindex debugging target
17611 A @dfn{target} is the execution environment occupied by your program.
17613 Often, @value{GDBN} runs in the same host environment as your program;
17614 in that case, the debugging target is specified as a side effect when
17615 you use the @code{file} or @code{core} commands. When you need more
17616 flexibility---for example, running @value{GDBN} on a physically separate
17617 host, or controlling a standalone system over a serial port or a
17618 realtime system over a TCP/IP connection---you can use the @code{target}
17619 command to specify one of the target types configured for @value{GDBN}
17620 (@pxref{Target Commands, ,Commands for Managing Targets}).
17622 @cindex target architecture
17623 It is possible to build @value{GDBN} for several different @dfn{target
17624 architectures}. When @value{GDBN} is built like that, you can choose
17625 one of the available architectures with the @kbd{set architecture}
17629 @kindex set architecture
17630 @kindex show architecture
17631 @item set architecture @var{arch}
17632 This command sets the current target architecture to @var{arch}. The
17633 value of @var{arch} can be @code{"auto"}, in addition to one of the
17634 supported architectures.
17636 @item show architecture
17637 Show the current target architecture.
17639 @item set processor
17641 @kindex set processor
17642 @kindex show processor
17643 These are alias commands for, respectively, @code{set architecture}
17644 and @code{show architecture}.
17648 * Active Targets:: Active targets
17649 * Target Commands:: Commands for managing targets
17650 * Byte Order:: Choosing target byte order
17653 @node Active Targets
17654 @section Active Targets
17656 @cindex stacking targets
17657 @cindex active targets
17658 @cindex multiple targets
17660 There are multiple classes of targets such as: processes, executable files or
17661 recording sessions. Core files belong to the process class, making core file
17662 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17663 on multiple active targets, one in each class. This allows you to (for
17664 example) start a process and inspect its activity, while still having access to
17665 the executable file after the process finishes. Or if you start process
17666 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17667 presented a virtual layer of the recording target, while the process target
17668 remains stopped at the chronologically last point of the process execution.
17670 Use the @code{core-file} and @code{exec-file} commands to select a new core
17671 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17672 specify as a target a process that is already running, use the @code{attach}
17673 command (@pxref{Attach, ,Debugging an Already-running Process}).
17675 @node Target Commands
17676 @section Commands for Managing Targets
17679 @item target @var{type} @var{parameters}
17680 Connects the @value{GDBN} host environment to a target machine or
17681 process. A target is typically a protocol for talking to debugging
17682 facilities. You use the argument @var{type} to specify the type or
17683 protocol of the target machine.
17685 Further @var{parameters} are interpreted by the target protocol, but
17686 typically include things like device names or host names to connect
17687 with, process numbers, and baud rates.
17689 The @code{target} command does not repeat if you press @key{RET} again
17690 after executing the command.
17692 @kindex help target
17694 Displays the names of all targets available. To display targets
17695 currently selected, use either @code{info target} or @code{info files}
17696 (@pxref{Files, ,Commands to Specify Files}).
17698 @item help target @var{name}
17699 Describe a particular target, including any parameters necessary to
17702 @kindex set gnutarget
17703 @item set gnutarget @var{args}
17704 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17705 knows whether it is reading an @dfn{executable},
17706 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17707 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17708 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17711 @emph{Warning:} To specify a file format with @code{set gnutarget},
17712 you must know the actual BFD name.
17716 @xref{Files, , Commands to Specify Files}.
17718 @kindex show gnutarget
17719 @item show gnutarget
17720 Use the @code{show gnutarget} command to display what file format
17721 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17722 @value{GDBN} will determine the file format for each file automatically,
17723 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17726 @cindex common targets
17727 Here are some common targets (available, or not, depending on the GDB
17732 @item target exec @var{program}
17733 @cindex executable file target
17734 An executable file. @samp{target exec @var{program}} is the same as
17735 @samp{exec-file @var{program}}.
17737 @item target core @var{filename}
17738 @cindex core dump file target
17739 A core dump file. @samp{target core @var{filename}} is the same as
17740 @samp{core-file @var{filename}}.
17742 @item target remote @var{medium}
17743 @cindex remote target
17744 A remote system connected to @value{GDBN} via a serial line or network
17745 connection. This command tells @value{GDBN} to use its own remote
17746 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17748 For example, if you have a board connected to @file{/dev/ttya} on the
17749 machine running @value{GDBN}, you could say:
17752 target remote /dev/ttya
17755 @code{target remote} supports the @code{load} command. This is only
17756 useful if you have some other way of getting the stub to the target
17757 system, and you can put it somewhere in memory where it won't get
17758 clobbered by the download.
17760 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17761 @cindex built-in simulator target
17762 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17770 works; however, you cannot assume that a specific memory map, device
17771 drivers, or even basic I/O is available, although some simulators do
17772 provide these. For info about any processor-specific simulator details,
17773 see the appropriate section in @ref{Embedded Processors, ,Embedded
17778 Different targets are available on different configurations of @value{GDBN};
17779 your configuration may have more or fewer targets.
17781 Many remote targets require you to download the executable's code once
17782 you've successfully established a connection. You may wish to control
17783 various aspects of this process.
17788 @kindex set hash@r{, for remote monitors}
17789 @cindex hash mark while downloading
17790 This command controls whether a hash mark @samp{#} is displayed while
17791 downloading a file to the remote monitor. If on, a hash mark is
17792 displayed after each S-record is successfully downloaded to the
17796 @kindex show hash@r{, for remote monitors}
17797 Show the current status of displaying the hash mark.
17799 @item set debug monitor
17800 @kindex set debug monitor
17801 @cindex display remote monitor communications
17802 Enable or disable display of communications messages between
17803 @value{GDBN} and the remote monitor.
17805 @item show debug monitor
17806 @kindex show debug monitor
17807 Show the current status of displaying communications between
17808 @value{GDBN} and the remote monitor.
17813 @kindex load @var{filename}
17814 @item load @var{filename}
17816 Depending on what remote debugging facilities are configured into
17817 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17818 is meant to make @var{filename} (an executable) available for debugging
17819 on the remote system---by downloading, or dynamic linking, for example.
17820 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17821 the @code{add-symbol-file} command.
17823 If your @value{GDBN} does not have a @code{load} command, attempting to
17824 execute it gets the error message ``@code{You can't do that when your
17825 target is @dots{}}''
17827 The file is loaded at whatever address is specified in the executable.
17828 For some object file formats, you can specify the load address when you
17829 link the program; for other formats, like a.out, the object file format
17830 specifies a fixed address.
17831 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17833 Depending on the remote side capabilities, @value{GDBN} may be able to
17834 load programs into flash memory.
17836 @code{load} does not repeat if you press @key{RET} again after using it.
17840 @section Choosing Target Byte Order
17842 @cindex choosing target byte order
17843 @cindex target byte order
17845 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17846 offer the ability to run either big-endian or little-endian byte
17847 orders. Usually the executable or symbol will include a bit to
17848 designate the endian-ness, and you will not need to worry about
17849 which to use. However, you may still find it useful to adjust
17850 @value{GDBN}'s idea of processor endian-ness manually.
17854 @item set endian big
17855 Instruct @value{GDBN} to assume the target is big-endian.
17857 @item set endian little
17858 Instruct @value{GDBN} to assume the target is little-endian.
17860 @item set endian auto
17861 Instruct @value{GDBN} to use the byte order associated with the
17865 Display @value{GDBN}'s current idea of the target byte order.
17869 Note that these commands merely adjust interpretation of symbolic
17870 data on the host, and that they have absolutely no effect on the
17874 @node Remote Debugging
17875 @chapter Debugging Remote Programs
17876 @cindex remote debugging
17878 If you are trying to debug a program running on a machine that cannot run
17879 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17880 For example, you might use remote debugging on an operating system kernel,
17881 or on a small system which does not have a general purpose operating system
17882 powerful enough to run a full-featured debugger.
17884 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17885 to make this work with particular debugging targets. In addition,
17886 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17887 but not specific to any particular target system) which you can use if you
17888 write the remote stubs---the code that runs on the remote system to
17889 communicate with @value{GDBN}.
17891 Other remote targets may be available in your
17892 configuration of @value{GDBN}; use @code{help target} to list them.
17895 * Connecting:: Connecting to a remote target
17896 * File Transfer:: Sending files to a remote system
17897 * Server:: Using the gdbserver program
17898 * Remote Configuration:: Remote configuration
17899 * Remote Stub:: Implementing a remote stub
17903 @section Connecting to a Remote Target
17905 On the @value{GDBN} host machine, you will need an unstripped copy of
17906 your program, since @value{GDBN} needs symbol and debugging information.
17907 Start up @value{GDBN} as usual, using the name of the local copy of your
17908 program as the first argument.
17910 @cindex @code{target remote}
17911 @value{GDBN} can communicate with the target over a serial line, or
17912 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17913 each case, @value{GDBN} uses the same protocol for debugging your
17914 program; only the medium carrying the debugging packets varies. The
17915 @code{target remote} command establishes a connection to the target.
17916 Its arguments indicate which medium to use:
17920 @item target remote @var{serial-device}
17921 @cindex serial line, @code{target remote}
17922 Use @var{serial-device} to communicate with the target. For example,
17923 to use a serial line connected to the device named @file{/dev/ttyb}:
17926 target remote /dev/ttyb
17929 If you're using a serial line, you may want to give @value{GDBN} the
17930 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17931 (@pxref{Remote Configuration, set remotebaud}) before the
17932 @code{target} command.
17934 @item target remote @code{@var{host}:@var{port}}
17935 @itemx target remote @code{tcp:@var{host}:@var{port}}
17936 @cindex @acronym{TCP} port, @code{target remote}
17937 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17938 The @var{host} may be either a host name or a numeric @acronym{IP}
17939 address; @var{port} must be a decimal number. The @var{host} could be
17940 the target machine itself, if it is directly connected to the net, or
17941 it might be a terminal server which in turn has a serial line to the
17944 For example, to connect to port 2828 on a terminal server named
17948 target remote manyfarms:2828
17951 If your remote target is actually running on the same machine as your
17952 debugger session (e.g.@: a simulator for your target running on the
17953 same host), you can omit the hostname. For example, to connect to
17954 port 1234 on your local machine:
17957 target remote :1234
17961 Note that the colon is still required here.
17963 @item target remote @code{udp:@var{host}:@var{port}}
17964 @cindex @acronym{UDP} port, @code{target remote}
17965 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17966 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17969 target remote udp:manyfarms:2828
17972 When using a @acronym{UDP} connection for remote debugging, you should
17973 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17974 can silently drop packets on busy or unreliable networks, which will
17975 cause havoc with your debugging session.
17977 @item target remote | @var{command}
17978 @cindex pipe, @code{target remote} to
17979 Run @var{command} in the background and communicate with it using a
17980 pipe. The @var{command} is a shell command, to be parsed and expanded
17981 by the system's command shell, @code{/bin/sh}; it should expect remote
17982 protocol packets on its standard input, and send replies on its
17983 standard output. You could use this to run a stand-alone simulator
17984 that speaks the remote debugging protocol, to make net connections
17985 using programs like @code{ssh}, or for other similar tricks.
17987 If @var{command} closes its standard output (perhaps by exiting),
17988 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17989 program has already exited, this will have no effect.)
17993 Once the connection has been established, you can use all the usual
17994 commands to examine and change data. The remote program is already
17995 running; you can use @kbd{step} and @kbd{continue}, and you do not
17996 need to use @kbd{run}.
17998 @cindex interrupting remote programs
17999 @cindex remote programs, interrupting
18000 Whenever @value{GDBN} is waiting for the remote program, if you type the
18001 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
18002 program. This may or may not succeed, depending in part on the hardware
18003 and the serial drivers the remote system uses. If you type the
18004 interrupt character once again, @value{GDBN} displays this prompt:
18007 Interrupted while waiting for the program.
18008 Give up (and stop debugging it)? (y or n)
18011 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
18012 (If you decide you want to try again later, you can use @samp{target
18013 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
18014 goes back to waiting.
18017 @kindex detach (remote)
18019 When you have finished debugging the remote program, you can use the
18020 @code{detach} command to release it from @value{GDBN} control.
18021 Detaching from the target normally resumes its execution, but the results
18022 will depend on your particular remote stub. After the @code{detach}
18023 command, @value{GDBN} is free to connect to another target.
18027 The @code{disconnect} command behaves like @code{detach}, except that
18028 the target is generally not resumed. It will wait for @value{GDBN}
18029 (this instance or another one) to connect and continue debugging. After
18030 the @code{disconnect} command, @value{GDBN} is again free to connect to
18033 @cindex send command to remote monitor
18034 @cindex extend @value{GDBN} for remote targets
18035 @cindex add new commands for external monitor
18037 @item monitor @var{cmd}
18038 This command allows you to send arbitrary commands directly to the
18039 remote monitor. Since @value{GDBN} doesn't care about the commands it
18040 sends like this, this command is the way to extend @value{GDBN}---you
18041 can add new commands that only the external monitor will understand
18045 @node File Transfer
18046 @section Sending files to a remote system
18047 @cindex remote target, file transfer
18048 @cindex file transfer
18049 @cindex sending files to remote systems
18051 Some remote targets offer the ability to transfer files over the same
18052 connection used to communicate with @value{GDBN}. This is convenient
18053 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
18054 running @code{gdbserver} over a network interface. For other targets,
18055 e.g.@: embedded devices with only a single serial port, this may be
18056 the only way to upload or download files.
18058 Not all remote targets support these commands.
18062 @item remote put @var{hostfile} @var{targetfile}
18063 Copy file @var{hostfile} from the host system (the machine running
18064 @value{GDBN}) to @var{targetfile} on the target system.
18067 @item remote get @var{targetfile} @var{hostfile}
18068 Copy file @var{targetfile} from the target system to @var{hostfile}
18069 on the host system.
18071 @kindex remote delete
18072 @item remote delete @var{targetfile}
18073 Delete @var{targetfile} from the target system.
18078 @section Using the @code{gdbserver} Program
18081 @cindex remote connection without stubs
18082 @code{gdbserver} is a control program for Unix-like systems, which
18083 allows you to connect your program with a remote @value{GDBN} via
18084 @code{target remote}---but without linking in the usual debugging stub.
18086 @code{gdbserver} is not a complete replacement for the debugging stubs,
18087 because it requires essentially the same operating-system facilities
18088 that @value{GDBN} itself does. In fact, a system that can run
18089 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18090 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18091 because it is a much smaller program than @value{GDBN} itself. It is
18092 also easier to port than all of @value{GDBN}, so you may be able to get
18093 started more quickly on a new system by using @code{gdbserver}.
18094 Finally, if you develop code for real-time systems, you may find that
18095 the tradeoffs involved in real-time operation make it more convenient to
18096 do as much development work as possible on another system, for example
18097 by cross-compiling. You can use @code{gdbserver} to make a similar
18098 choice for debugging.
18100 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18101 or a TCP connection, using the standard @value{GDBN} remote serial
18105 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18106 Do not run @code{gdbserver} connected to any public network; a
18107 @value{GDBN} connection to @code{gdbserver} provides access to the
18108 target system with the same privileges as the user running
18112 @subsection Running @code{gdbserver}
18113 @cindex arguments, to @code{gdbserver}
18114 @cindex @code{gdbserver}, command-line arguments
18116 Run @code{gdbserver} on the target system. You need a copy of the
18117 program you want to debug, including any libraries it requires.
18118 @code{gdbserver} does not need your program's symbol table, so you can
18119 strip the program if necessary to save space. @value{GDBN} on the host
18120 system does all the symbol handling.
18122 To use the server, you must tell it how to communicate with @value{GDBN};
18123 the name of your program; and the arguments for your program. The usual
18127 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18130 @var{comm} is either a device name (to use a serial line), or a TCP
18131 hostname and portnumber, or @code{-} or @code{stdio} to use
18132 stdin/stdout of @code{gdbserver}.
18133 For example, to debug Emacs with the argument
18134 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18138 target> gdbserver /dev/com1 emacs foo.txt
18141 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18144 To use a TCP connection instead of a serial line:
18147 target> gdbserver host:2345 emacs foo.txt
18150 The only difference from the previous example is the first argument,
18151 specifying that you are communicating with the host @value{GDBN} via
18152 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18153 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18154 (Currently, the @samp{host} part is ignored.) You can choose any number
18155 you want for the port number as long as it does not conflict with any
18156 TCP ports already in use on the target system (for example, @code{23} is
18157 reserved for @code{telnet}).@footnote{If you choose a port number that
18158 conflicts with another service, @code{gdbserver} prints an error message
18159 and exits.} You must use the same port number with the host @value{GDBN}
18160 @code{target remote} command.
18162 The @code{stdio} connection is useful when starting @code{gdbserver}
18166 (gdb) target remote | ssh -T hostname gdbserver - hello
18169 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18170 and we don't want escape-character handling. Ssh does this by default when
18171 a command is provided, the flag is provided to make it explicit.
18172 You could elide it if you want to.
18174 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18175 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18176 display through a pipe connected to gdbserver.
18177 Both @code{stdout} and @code{stderr} use the same pipe.
18179 @subsubsection Attaching to a Running Program
18180 @cindex attach to a program, @code{gdbserver}
18181 @cindex @option{--attach}, @code{gdbserver} option
18183 On some targets, @code{gdbserver} can also attach to running programs.
18184 This is accomplished via the @code{--attach} argument. The syntax is:
18187 target> gdbserver --attach @var{comm} @var{pid}
18190 @var{pid} is the process ID of a currently running process. It isn't necessary
18191 to point @code{gdbserver} at a binary for the running process.
18194 You can debug processes by name instead of process ID if your target has the
18195 @code{pidof} utility:
18198 target> gdbserver --attach @var{comm} `pidof @var{program}`
18201 In case more than one copy of @var{program} is running, or @var{program}
18202 has multiple threads, most versions of @code{pidof} support the
18203 @code{-s} option to only return the first process ID.
18205 @subsubsection Multi-Process Mode for @code{gdbserver}
18206 @cindex @code{gdbserver}, multiple processes
18207 @cindex multiple processes with @code{gdbserver}
18209 When you connect to @code{gdbserver} using @code{target remote},
18210 @code{gdbserver} debugs the specified program only once. When the
18211 program exits, or you detach from it, @value{GDBN} closes the connection
18212 and @code{gdbserver} exits.
18214 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18215 enters multi-process mode. When the debugged program exits, or you
18216 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18217 though no program is running. The @code{run} and @code{attach}
18218 commands instruct @code{gdbserver} to run or attach to a new program.
18219 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18220 remote exec-file}) to select the program to run. Command line
18221 arguments are supported, except for wildcard expansion and I/O
18222 redirection (@pxref{Arguments}).
18224 @cindex @option{--multi}, @code{gdbserver} option
18225 To start @code{gdbserver} without supplying an initial command to run
18226 or process ID to attach, use the @option{--multi} command line option.
18227 Then you can connect using @kbd{target extended-remote} and start
18228 the program you want to debug.
18230 In multi-process mode @code{gdbserver} does not automatically exit unless you
18231 use the option @option{--once}. You can terminate it by using
18232 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18233 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18234 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18235 @option{--multi} option to @code{gdbserver} has no influence on that.
18237 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18239 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18241 @code{gdbserver} normally terminates after all of its debugged processes have
18242 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18243 extended-remote}, @code{gdbserver} stays running even with no processes left.
18244 @value{GDBN} normally terminates the spawned debugged process on its exit,
18245 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18246 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18247 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18248 stays running even in the @kbd{target remote} mode.
18250 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18251 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18252 completeness, at most one @value{GDBN} can be connected at a time.
18254 @cindex @option{--once}, @code{gdbserver} option
18255 By default, @code{gdbserver} keeps the listening TCP port open, so that
18256 subsequent connections are possible. However, if you start @code{gdbserver}
18257 with the @option{--once} option, it will stop listening for any further
18258 connection attempts after connecting to the first @value{GDBN} session. This
18259 means no further connections to @code{gdbserver} will be possible after the
18260 first one. It also means @code{gdbserver} will terminate after the first
18261 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18262 connections and even in the @kbd{target extended-remote} mode. The
18263 @option{--once} option allows reusing the same port number for connecting to
18264 multiple instances of @code{gdbserver} running on the same host, since each
18265 instance closes its port after the first connection.
18267 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18269 @cindex @option{--debug}, @code{gdbserver} option
18270 The @option{--debug} option tells @code{gdbserver} to display extra
18271 status information about the debugging process.
18272 @cindex @option{--remote-debug}, @code{gdbserver} option
18273 The @option{--remote-debug} option tells @code{gdbserver} to display
18274 remote protocol debug output. These options are intended for
18275 @code{gdbserver} development and for bug reports to the developers.
18277 @cindex @option{--wrapper}, @code{gdbserver} option
18278 The @option{--wrapper} option specifies a wrapper to launch programs
18279 for debugging. The option should be followed by the name of the
18280 wrapper, then any command-line arguments to pass to the wrapper, then
18281 @kbd{--} indicating the end of the wrapper arguments.
18283 @code{gdbserver} runs the specified wrapper program with a combined
18284 command line including the wrapper arguments, then the name of the
18285 program to debug, then any arguments to the program. The wrapper
18286 runs until it executes your program, and then @value{GDBN} gains control.
18288 You can use any program that eventually calls @code{execve} with
18289 its arguments as a wrapper. Several standard Unix utilities do
18290 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18291 with @code{exec "$@@"} will also work.
18293 For example, you can use @code{env} to pass an environment variable to
18294 the debugged program, without setting the variable in @code{gdbserver}'s
18298 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18301 @subsection Connecting to @code{gdbserver}
18303 Run @value{GDBN} on the host system.
18305 First make sure you have the necessary symbol files. Load symbols for
18306 your application using the @code{file} command before you connect. Use
18307 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18308 was compiled with the correct sysroot using @code{--with-sysroot}).
18310 The symbol file and target libraries must exactly match the executable
18311 and libraries on the target, with one exception: the files on the host
18312 system should not be stripped, even if the files on the target system
18313 are. Mismatched or missing files will lead to confusing results
18314 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18315 files may also prevent @code{gdbserver} from debugging multi-threaded
18318 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18319 For TCP connections, you must start up @code{gdbserver} prior to using
18320 the @code{target remote} command. Otherwise you may get an error whose
18321 text depends on the host system, but which usually looks something like
18322 @samp{Connection refused}. Don't use the @code{load}
18323 command in @value{GDBN} when using @code{gdbserver}, since the program is
18324 already on the target.
18326 @subsection Monitor Commands for @code{gdbserver}
18327 @cindex monitor commands, for @code{gdbserver}
18328 @anchor{Monitor Commands for gdbserver}
18330 During a @value{GDBN} session using @code{gdbserver}, you can use the
18331 @code{monitor} command to send special requests to @code{gdbserver}.
18332 Here are the available commands.
18336 List the available monitor commands.
18338 @item monitor set debug 0
18339 @itemx monitor set debug 1
18340 Disable or enable general debugging messages.
18342 @item monitor set remote-debug 0
18343 @itemx monitor set remote-debug 1
18344 Disable or enable specific debugging messages associated with the remote
18345 protocol (@pxref{Remote Protocol}).
18347 @item monitor set libthread-db-search-path [PATH]
18348 @cindex gdbserver, search path for @code{libthread_db}
18349 When this command is issued, @var{path} is a colon-separated list of
18350 directories to search for @code{libthread_db} (@pxref{Threads,,set
18351 libthread-db-search-path}). If you omit @var{path},
18352 @samp{libthread-db-search-path} will be reset to its default value.
18354 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18355 not supported in @code{gdbserver}.
18358 Tell gdbserver to exit immediately. This command should be followed by
18359 @code{disconnect} to close the debugging session. @code{gdbserver} will
18360 detach from any attached processes and kill any processes it created.
18361 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18362 of a multi-process mode debug session.
18366 @subsection Tracepoints support in @code{gdbserver}
18367 @cindex tracepoints support in @code{gdbserver}
18369 On some targets, @code{gdbserver} supports tracepoints, fast
18370 tracepoints and static tracepoints.
18372 For fast or static tracepoints to work, a special library called the
18373 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18374 This library is built and distributed as an integral part of
18375 @code{gdbserver}. In addition, support for static tracepoints
18376 requires building the in-process agent library with static tracepoints
18377 support. At present, the UST (LTTng Userspace Tracer,
18378 @url{http://lttng.org/ust}) tracing engine is supported. This support
18379 is automatically available if UST development headers are found in the
18380 standard include path when @code{gdbserver} is built, or if
18381 @code{gdbserver} was explicitly configured using @option{--with-ust}
18382 to point at such headers. You can explicitly disable the support
18383 using @option{--with-ust=no}.
18385 There are several ways to load the in-process agent in your program:
18388 @item Specifying it as dependency at link time
18390 You can link your program dynamically with the in-process agent
18391 library. On most systems, this is accomplished by adding
18392 @code{-linproctrace} to the link command.
18394 @item Using the system's preloading mechanisms
18396 You can force loading the in-process agent at startup time by using
18397 your system's support for preloading shared libraries. Many Unixes
18398 support the concept of preloading user defined libraries. In most
18399 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18400 in the environment. See also the description of @code{gdbserver}'s
18401 @option{--wrapper} command line option.
18403 @item Using @value{GDBN} to force loading the agent at run time
18405 On some systems, you can force the inferior to load a shared library,
18406 by calling a dynamic loader function in the inferior that takes care
18407 of dynamically looking up and loading a shared library. On most Unix
18408 systems, the function is @code{dlopen}. You'll use the @code{call}
18409 command for that. For example:
18412 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18415 Note that on most Unix systems, for the @code{dlopen} function to be
18416 available, the program needs to be linked with @code{-ldl}.
18419 On systems that have a userspace dynamic loader, like most Unix
18420 systems, when you connect to @code{gdbserver} using @code{target
18421 remote}, you'll find that the program is stopped at the dynamic
18422 loader's entry point, and no shared library has been loaded in the
18423 program's address space yet, including the in-process agent. In that
18424 case, before being able to use any of the fast or static tracepoints
18425 features, you need to let the loader run and load the shared
18426 libraries. The simplest way to do that is to run the program to the
18427 main procedure. E.g., if debugging a C or C@t{++} program, start
18428 @code{gdbserver} like so:
18431 $ gdbserver :9999 myprogram
18434 Start GDB and connect to @code{gdbserver} like so, and run to main:
18438 (@value{GDBP}) target remote myhost:9999
18439 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18440 (@value{GDBP}) b main
18441 (@value{GDBP}) continue
18444 The in-process tracing agent library should now be loaded into the
18445 process; you can confirm it with the @code{info sharedlibrary}
18446 command, which will list @file{libinproctrace.so} as loaded in the
18447 process. You are now ready to install fast tracepoints, list static
18448 tracepoint markers, probe static tracepoints markers, and start
18451 @node Remote Configuration
18452 @section Remote Configuration
18455 @kindex show remote
18456 This section documents the configuration options available when
18457 debugging remote programs. For the options related to the File I/O
18458 extensions of the remote protocol, see @ref{system,
18459 system-call-allowed}.
18462 @item set remoteaddresssize @var{bits}
18463 @cindex address size for remote targets
18464 @cindex bits in remote address
18465 Set the maximum size of address in a memory packet to the specified
18466 number of bits. @value{GDBN} will mask off the address bits above
18467 that number, when it passes addresses to the remote target. The
18468 default value is the number of bits in the target's address.
18470 @item show remoteaddresssize
18471 Show the current value of remote address size in bits.
18473 @item set remotebaud @var{n}
18474 @cindex baud rate for remote targets
18475 Set the baud rate for the remote serial I/O to @var{n} baud. The
18476 value is used to set the speed of the serial port used for debugging
18479 @item show remotebaud
18480 Show the current speed of the remote connection.
18482 @item set remotebreak
18483 @cindex interrupt remote programs
18484 @cindex BREAK signal instead of Ctrl-C
18485 @anchor{set remotebreak}
18486 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18487 when you type @kbd{Ctrl-c} to interrupt the program running
18488 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18489 character instead. The default is off, since most remote systems
18490 expect to see @samp{Ctrl-C} as the interrupt signal.
18492 @item show remotebreak
18493 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18494 interrupt the remote program.
18496 @item set remoteflow on
18497 @itemx set remoteflow off
18498 @kindex set remoteflow
18499 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18500 on the serial port used to communicate to the remote target.
18502 @item show remoteflow
18503 @kindex show remoteflow
18504 Show the current setting of hardware flow control.
18506 @item set remotelogbase @var{base}
18507 Set the base (a.k.a.@: radix) of logging serial protocol
18508 communications to @var{base}. Supported values of @var{base} are:
18509 @code{ascii}, @code{octal}, and @code{hex}. The default is
18512 @item show remotelogbase
18513 Show the current setting of the radix for logging remote serial
18516 @item set remotelogfile @var{file}
18517 @cindex record serial communications on file
18518 Record remote serial communications on the named @var{file}. The
18519 default is not to record at all.
18521 @item show remotelogfile.
18522 Show the current setting of the file name on which to record the
18523 serial communications.
18525 @item set remotetimeout @var{num}
18526 @cindex timeout for serial communications
18527 @cindex remote timeout
18528 Set the timeout limit to wait for the remote target to respond to
18529 @var{num} seconds. The default is 2 seconds.
18531 @item show remotetimeout
18532 Show the current number of seconds to wait for the remote target
18535 @cindex limit hardware breakpoints and watchpoints
18536 @cindex remote target, limit break- and watchpoints
18537 @anchor{set remote hardware-watchpoint-limit}
18538 @anchor{set remote hardware-breakpoint-limit}
18539 @item set remote hardware-watchpoint-limit @var{limit}
18540 @itemx set remote hardware-breakpoint-limit @var{limit}
18541 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18542 watchpoints. A limit of -1, the default, is treated as unlimited.
18544 @cindex limit hardware watchpoints length
18545 @cindex remote target, limit watchpoints length
18546 @anchor{set remote hardware-watchpoint-length-limit}
18547 @item set remote hardware-watchpoint-length-limit @var{limit}
18548 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18549 a remote hardware watchpoint. A limit of -1, the default, is treated
18552 @item show remote hardware-watchpoint-length-limit
18553 Show the current limit (in bytes) of the maximum length of
18554 a remote hardware watchpoint.
18556 @item set remote exec-file @var{filename}
18557 @itemx show remote exec-file
18558 @anchor{set remote exec-file}
18559 @cindex executable file, for remote target
18560 Select the file used for @code{run} with @code{target
18561 extended-remote}. This should be set to a filename valid on the
18562 target system. If it is not set, the target will use a default
18563 filename (e.g.@: the last program run).
18565 @item set remote interrupt-sequence
18566 @cindex interrupt remote programs
18567 @cindex select Ctrl-C, BREAK or BREAK-g
18568 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18569 @samp{BREAK-g} as the
18570 sequence to the remote target in order to interrupt the execution.
18571 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18572 is high level of serial line for some certain time.
18573 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18574 It is @code{BREAK} signal followed by character @code{g}.
18576 @item show interrupt-sequence
18577 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18578 is sent by @value{GDBN} to interrupt the remote program.
18579 @code{BREAK-g} is BREAK signal followed by @code{g} and
18580 also known as Magic SysRq g.
18582 @item set remote interrupt-on-connect
18583 @cindex send interrupt-sequence on start
18584 Specify whether interrupt-sequence is sent to remote target when
18585 @value{GDBN} connects to it. This is mostly needed when you debug
18586 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18587 which is known as Magic SysRq g in order to connect @value{GDBN}.
18589 @item show interrupt-on-connect
18590 Show whether interrupt-sequence is sent
18591 to remote target when @value{GDBN} connects to it.
18595 @item set tcp auto-retry on
18596 @cindex auto-retry, for remote TCP target
18597 Enable auto-retry for remote TCP connections. This is useful if the remote
18598 debugging agent is launched in parallel with @value{GDBN}; there is a race
18599 condition because the agent may not become ready to accept the connection
18600 before @value{GDBN} attempts to connect. When auto-retry is
18601 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18602 to establish the connection using the timeout specified by
18603 @code{set tcp connect-timeout}.
18605 @item set tcp auto-retry off
18606 Do not auto-retry failed TCP connections.
18608 @item show tcp auto-retry
18609 Show the current auto-retry setting.
18611 @item set tcp connect-timeout @var{seconds}
18612 @itemx set tcp connect-timeout unlimited
18613 @cindex connection timeout, for remote TCP target
18614 @cindex timeout, for remote target connection
18615 Set the timeout for establishing a TCP connection to the remote target to
18616 @var{seconds}. The timeout affects both polling to retry failed connections
18617 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18618 that are merely slow to complete, and represents an approximate cumulative
18619 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18620 @value{GDBN} will keep attempting to establish a connection forever,
18621 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18623 @item show tcp connect-timeout
18624 Show the current connection timeout setting.
18627 @cindex remote packets, enabling and disabling
18628 The @value{GDBN} remote protocol autodetects the packets supported by
18629 your debugging stub. If you need to override the autodetection, you
18630 can use these commands to enable or disable individual packets. Each
18631 packet can be set to @samp{on} (the remote target supports this
18632 packet), @samp{off} (the remote target does not support this packet),
18633 or @samp{auto} (detect remote target support for this packet). They
18634 all default to @samp{auto}. For more information about each packet,
18635 see @ref{Remote Protocol}.
18637 During normal use, you should not have to use any of these commands.
18638 If you do, that may be a bug in your remote debugging stub, or a bug
18639 in @value{GDBN}. You may want to report the problem to the
18640 @value{GDBN} developers.
18642 For each packet @var{name}, the command to enable or disable the
18643 packet is @code{set remote @var{name}-packet}. The available settings
18646 @multitable @columnfractions 0.28 0.32 0.25
18649 @tab Related Features
18651 @item @code{fetch-register}
18653 @tab @code{info registers}
18655 @item @code{set-register}
18659 @item @code{binary-download}
18661 @tab @code{load}, @code{set}
18663 @item @code{read-aux-vector}
18664 @tab @code{qXfer:auxv:read}
18665 @tab @code{info auxv}
18667 @item @code{symbol-lookup}
18668 @tab @code{qSymbol}
18669 @tab Detecting multiple threads
18671 @item @code{attach}
18672 @tab @code{vAttach}
18675 @item @code{verbose-resume}
18677 @tab Stepping or resuming multiple threads
18683 @item @code{software-breakpoint}
18687 @item @code{hardware-breakpoint}
18691 @item @code{write-watchpoint}
18695 @item @code{read-watchpoint}
18699 @item @code{access-watchpoint}
18703 @item @code{target-features}
18704 @tab @code{qXfer:features:read}
18705 @tab @code{set architecture}
18707 @item @code{library-info}
18708 @tab @code{qXfer:libraries:read}
18709 @tab @code{info sharedlibrary}
18711 @item @code{memory-map}
18712 @tab @code{qXfer:memory-map:read}
18713 @tab @code{info mem}
18715 @item @code{read-sdata-object}
18716 @tab @code{qXfer:sdata:read}
18717 @tab @code{print $_sdata}
18719 @item @code{read-spu-object}
18720 @tab @code{qXfer:spu:read}
18721 @tab @code{info spu}
18723 @item @code{write-spu-object}
18724 @tab @code{qXfer:spu:write}
18725 @tab @code{info spu}
18727 @item @code{read-siginfo-object}
18728 @tab @code{qXfer:siginfo:read}
18729 @tab @code{print $_siginfo}
18731 @item @code{write-siginfo-object}
18732 @tab @code{qXfer:siginfo:write}
18733 @tab @code{set $_siginfo}
18735 @item @code{threads}
18736 @tab @code{qXfer:threads:read}
18737 @tab @code{info threads}
18739 @item @code{get-thread-local-@*storage-address}
18740 @tab @code{qGetTLSAddr}
18741 @tab Displaying @code{__thread} variables
18743 @item @code{get-thread-information-block-address}
18744 @tab @code{qGetTIBAddr}
18745 @tab Display MS-Windows Thread Information Block.
18747 @item @code{search-memory}
18748 @tab @code{qSearch:memory}
18751 @item @code{supported-packets}
18752 @tab @code{qSupported}
18753 @tab Remote communications parameters
18755 @item @code{pass-signals}
18756 @tab @code{QPassSignals}
18757 @tab @code{handle @var{signal}}
18759 @item @code{program-signals}
18760 @tab @code{QProgramSignals}
18761 @tab @code{handle @var{signal}}
18763 @item @code{hostio-close-packet}
18764 @tab @code{vFile:close}
18765 @tab @code{remote get}, @code{remote put}
18767 @item @code{hostio-open-packet}
18768 @tab @code{vFile:open}
18769 @tab @code{remote get}, @code{remote put}
18771 @item @code{hostio-pread-packet}
18772 @tab @code{vFile:pread}
18773 @tab @code{remote get}, @code{remote put}
18775 @item @code{hostio-pwrite-packet}
18776 @tab @code{vFile:pwrite}
18777 @tab @code{remote get}, @code{remote put}
18779 @item @code{hostio-unlink-packet}
18780 @tab @code{vFile:unlink}
18781 @tab @code{remote delete}
18783 @item @code{hostio-readlink-packet}
18784 @tab @code{vFile:readlink}
18787 @item @code{noack-packet}
18788 @tab @code{QStartNoAckMode}
18789 @tab Packet acknowledgment
18791 @item @code{osdata}
18792 @tab @code{qXfer:osdata:read}
18793 @tab @code{info os}
18795 @item @code{query-attached}
18796 @tab @code{qAttached}
18797 @tab Querying remote process attach state.
18799 @item @code{trace-buffer-size}
18800 @tab @code{QTBuffer:size}
18801 @tab @code{set trace-buffer-size}
18803 @item @code{trace-status}
18804 @tab @code{qTStatus}
18805 @tab @code{tstatus}
18807 @item @code{traceframe-info}
18808 @tab @code{qXfer:traceframe-info:read}
18809 @tab Traceframe info
18811 @item @code{install-in-trace}
18812 @tab @code{InstallInTrace}
18813 @tab Install tracepoint in tracing
18815 @item @code{disable-randomization}
18816 @tab @code{QDisableRandomization}
18817 @tab @code{set disable-randomization}
18819 @item @code{conditional-breakpoints-packet}
18820 @tab @code{Z0 and Z1}
18821 @tab @code{Support for target-side breakpoint condition evaluation}
18825 @section Implementing a Remote Stub
18827 @cindex debugging stub, example
18828 @cindex remote stub, example
18829 @cindex stub example, remote debugging
18830 The stub files provided with @value{GDBN} implement the target side of the
18831 communication protocol, and the @value{GDBN} side is implemented in the
18832 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18833 these subroutines to communicate, and ignore the details. (If you're
18834 implementing your own stub file, you can still ignore the details: start
18835 with one of the existing stub files. @file{sparc-stub.c} is the best
18836 organized, and therefore the easiest to read.)
18838 @cindex remote serial debugging, overview
18839 To debug a program running on another machine (the debugging
18840 @dfn{target} machine), you must first arrange for all the usual
18841 prerequisites for the program to run by itself. For example, for a C
18846 A startup routine to set up the C runtime environment; these usually
18847 have a name like @file{crt0}. The startup routine may be supplied by
18848 your hardware supplier, or you may have to write your own.
18851 A C subroutine library to support your program's
18852 subroutine calls, notably managing input and output.
18855 A way of getting your program to the other machine---for example, a
18856 download program. These are often supplied by the hardware
18857 manufacturer, but you may have to write your own from hardware
18861 The next step is to arrange for your program to use a serial port to
18862 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18863 machine). In general terms, the scheme looks like this:
18867 @value{GDBN} already understands how to use this protocol; when everything
18868 else is set up, you can simply use the @samp{target remote} command
18869 (@pxref{Targets,,Specifying a Debugging Target}).
18871 @item On the target,
18872 you must link with your program a few special-purpose subroutines that
18873 implement the @value{GDBN} remote serial protocol. The file containing these
18874 subroutines is called a @dfn{debugging stub}.
18876 On certain remote targets, you can use an auxiliary program
18877 @code{gdbserver} instead of linking a stub into your program.
18878 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18881 The debugging stub is specific to the architecture of the remote
18882 machine; for example, use @file{sparc-stub.c} to debug programs on
18885 @cindex remote serial stub list
18886 These working remote stubs are distributed with @value{GDBN}:
18891 @cindex @file{i386-stub.c}
18894 For Intel 386 and compatible architectures.
18897 @cindex @file{m68k-stub.c}
18898 @cindex Motorola 680x0
18900 For Motorola 680x0 architectures.
18903 @cindex @file{sh-stub.c}
18906 For Renesas SH architectures.
18909 @cindex @file{sparc-stub.c}
18911 For @sc{sparc} architectures.
18913 @item sparcl-stub.c
18914 @cindex @file{sparcl-stub.c}
18917 For Fujitsu @sc{sparclite} architectures.
18921 The @file{README} file in the @value{GDBN} distribution may list other
18922 recently added stubs.
18925 * Stub Contents:: What the stub can do for you
18926 * Bootstrapping:: What you must do for the stub
18927 * Debug Session:: Putting it all together
18930 @node Stub Contents
18931 @subsection What the Stub Can Do for You
18933 @cindex remote serial stub
18934 The debugging stub for your architecture supplies these three
18938 @item set_debug_traps
18939 @findex set_debug_traps
18940 @cindex remote serial stub, initialization
18941 This routine arranges for @code{handle_exception} to run when your
18942 program stops. You must call this subroutine explicitly in your
18943 program's startup code.
18945 @item handle_exception
18946 @findex handle_exception
18947 @cindex remote serial stub, main routine
18948 This is the central workhorse, but your program never calls it
18949 explicitly---the setup code arranges for @code{handle_exception} to
18950 run when a trap is triggered.
18952 @code{handle_exception} takes control when your program stops during
18953 execution (for example, on a breakpoint), and mediates communications
18954 with @value{GDBN} on the host machine. This is where the communications
18955 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18956 representative on the target machine. It begins by sending summary
18957 information on the state of your program, then continues to execute,
18958 retrieving and transmitting any information @value{GDBN} needs, until you
18959 execute a @value{GDBN} command that makes your program resume; at that point,
18960 @code{handle_exception} returns control to your own code on the target
18964 @cindex @code{breakpoint} subroutine, remote
18965 Use this auxiliary subroutine to make your program contain a
18966 breakpoint. Depending on the particular situation, this may be the only
18967 way for @value{GDBN} to get control. For instance, if your target
18968 machine has some sort of interrupt button, you won't need to call this;
18969 pressing the interrupt button transfers control to
18970 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18971 simply receiving characters on the serial port may also trigger a trap;
18972 again, in that situation, you don't need to call @code{breakpoint} from
18973 your own program---simply running @samp{target remote} from the host
18974 @value{GDBN} session gets control.
18976 Call @code{breakpoint} if none of these is true, or if you simply want
18977 to make certain your program stops at a predetermined point for the
18978 start of your debugging session.
18981 @node Bootstrapping
18982 @subsection What You Must Do for the Stub
18984 @cindex remote stub, support routines
18985 The debugging stubs that come with @value{GDBN} are set up for a particular
18986 chip architecture, but they have no information about the rest of your
18987 debugging target machine.
18989 First of all you need to tell the stub how to communicate with the
18993 @item int getDebugChar()
18994 @findex getDebugChar
18995 Write this subroutine to read a single character from the serial port.
18996 It may be identical to @code{getchar} for your target system; a
18997 different name is used to allow you to distinguish the two if you wish.
18999 @item void putDebugChar(int)
19000 @findex putDebugChar
19001 Write this subroutine to write a single character to the serial port.
19002 It may be identical to @code{putchar} for your target system; a
19003 different name is used to allow you to distinguish the two if you wish.
19006 @cindex control C, and remote debugging
19007 @cindex interrupting remote targets
19008 If you want @value{GDBN} to be able to stop your program while it is
19009 running, you need to use an interrupt-driven serial driver, and arrange
19010 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
19011 character). That is the character which @value{GDBN} uses to tell the
19012 remote system to stop.
19014 Getting the debugging target to return the proper status to @value{GDBN}
19015 probably requires changes to the standard stub; one quick and dirty way
19016 is to just execute a breakpoint instruction (the ``dirty'' part is that
19017 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
19019 Other routines you need to supply are:
19022 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
19023 @findex exceptionHandler
19024 Write this function to install @var{exception_address} in the exception
19025 handling tables. You need to do this because the stub does not have any
19026 way of knowing what the exception handling tables on your target system
19027 are like (for example, the processor's table might be in @sc{rom},
19028 containing entries which point to a table in @sc{ram}).
19029 @var{exception_number} is the exception number which should be changed;
19030 its meaning is architecture-dependent (for example, different numbers
19031 might represent divide by zero, misaligned access, etc). When this
19032 exception occurs, control should be transferred directly to
19033 @var{exception_address}, and the processor state (stack, registers,
19034 and so on) should be just as it is when a processor exception occurs. So if
19035 you want to use a jump instruction to reach @var{exception_address}, it
19036 should be a simple jump, not a jump to subroutine.
19038 For the 386, @var{exception_address} should be installed as an interrupt
19039 gate so that interrupts are masked while the handler runs. The gate
19040 should be at privilege level 0 (the most privileged level). The
19041 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
19042 help from @code{exceptionHandler}.
19044 @item void flush_i_cache()
19045 @findex flush_i_cache
19046 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
19047 instruction cache, if any, on your target machine. If there is no
19048 instruction cache, this subroutine may be a no-op.
19050 On target machines that have instruction caches, @value{GDBN} requires this
19051 function to make certain that the state of your program is stable.
19055 You must also make sure this library routine is available:
19058 @item void *memset(void *, int, int)
19060 This is the standard library function @code{memset} that sets an area of
19061 memory to a known value. If you have one of the free versions of
19062 @code{libc.a}, @code{memset} can be found there; otherwise, you must
19063 either obtain it from your hardware manufacturer, or write your own.
19066 If you do not use the GNU C compiler, you may need other standard
19067 library subroutines as well; this varies from one stub to another,
19068 but in general the stubs are likely to use any of the common library
19069 subroutines which @code{@value{NGCC}} generates as inline code.
19072 @node Debug Session
19073 @subsection Putting it All Together
19075 @cindex remote serial debugging summary
19076 In summary, when your program is ready to debug, you must follow these
19081 Make sure you have defined the supporting low-level routines
19082 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19084 @code{getDebugChar}, @code{putDebugChar},
19085 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19089 Insert these lines in your program's startup code, before the main
19090 procedure is called:
19097 On some machines, when a breakpoint trap is raised, the hardware
19098 automatically makes the PC point to the instruction after the
19099 breakpoint. If your machine doesn't do that, you may need to adjust
19100 @code{handle_exception} to arrange for it to return to the instruction
19101 after the breakpoint on this first invocation, so that your program
19102 doesn't keep hitting the initial breakpoint instead of making
19106 For the 680x0 stub only, you need to provide a variable called
19107 @code{exceptionHook}. Normally you just use:
19110 void (*exceptionHook)() = 0;
19114 but if before calling @code{set_debug_traps}, you set it to point to a
19115 function in your program, that function is called when
19116 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19117 error). The function indicated by @code{exceptionHook} is called with
19118 one parameter: an @code{int} which is the exception number.
19121 Compile and link together: your program, the @value{GDBN} debugging stub for
19122 your target architecture, and the supporting subroutines.
19125 Make sure you have a serial connection between your target machine and
19126 the @value{GDBN} host, and identify the serial port on the host.
19129 @c The "remote" target now provides a `load' command, so we should
19130 @c document that. FIXME.
19131 Download your program to your target machine (or get it there by
19132 whatever means the manufacturer provides), and start it.
19135 Start @value{GDBN} on the host, and connect to the target
19136 (@pxref{Connecting,,Connecting to a Remote Target}).
19140 @node Configurations
19141 @chapter Configuration-Specific Information
19143 While nearly all @value{GDBN} commands are available for all native and
19144 cross versions of the debugger, there are some exceptions. This chapter
19145 describes things that are only available in certain configurations.
19147 There are three major categories of configurations: native
19148 configurations, where the host and target are the same, embedded
19149 operating system configurations, which are usually the same for several
19150 different processor architectures, and bare embedded processors, which
19151 are quite different from each other.
19156 * Embedded Processors::
19163 This section describes details specific to particular native
19168 * BSD libkvm Interface:: Debugging BSD kernel memory images
19169 * SVR4 Process Information:: SVR4 process information
19170 * DJGPP Native:: Features specific to the DJGPP port
19171 * Cygwin Native:: Features specific to the Cygwin port
19172 * Hurd Native:: Features specific to @sc{gnu} Hurd
19173 * Darwin:: Features specific to Darwin
19179 On HP-UX systems, if you refer to a function or variable name that
19180 begins with a dollar sign, @value{GDBN} searches for a user or system
19181 name first, before it searches for a convenience variable.
19184 @node BSD libkvm Interface
19185 @subsection BSD libkvm Interface
19188 @cindex kernel memory image
19189 @cindex kernel crash dump
19191 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19192 interface that provides a uniform interface for accessing kernel virtual
19193 memory images, including live systems and crash dumps. @value{GDBN}
19194 uses this interface to allow you to debug live kernels and kernel crash
19195 dumps on many native BSD configurations. This is implemented as a
19196 special @code{kvm} debugging target. For debugging a live system, load
19197 the currently running kernel into @value{GDBN} and connect to the
19201 (@value{GDBP}) @b{target kvm}
19204 For debugging crash dumps, provide the file name of the crash dump as an
19208 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19211 Once connected to the @code{kvm} target, the following commands are
19217 Set current context from the @dfn{Process Control Block} (PCB) address.
19220 Set current context from proc address. This command isn't available on
19221 modern FreeBSD systems.
19224 @node SVR4 Process Information
19225 @subsection SVR4 Process Information
19227 @cindex examine process image
19228 @cindex process info via @file{/proc}
19230 Many versions of SVR4 and compatible systems provide a facility called
19231 @samp{/proc} that can be used to examine the image of a running
19232 process using file-system subroutines.
19234 If @value{GDBN} is configured for an operating system with this
19235 facility, the command @code{info proc} is available to report
19236 information about the process running your program, or about any
19237 process running on your system. This includes, as of this writing,
19238 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19239 not HP-UX, for example.
19241 This command may also work on core files that were created on a system
19242 that has the @samp{/proc} facility.
19248 @itemx info proc @var{process-id}
19249 Summarize available information about any running process. If a
19250 process ID is specified by @var{process-id}, display information about
19251 that process; otherwise display information about the program being
19252 debugged. The summary includes the debugged process ID, the command
19253 line used to invoke it, its current working directory, and its
19254 executable file's absolute file name.
19256 On some systems, @var{process-id} can be of the form
19257 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19258 within a process. If the optional @var{pid} part is missing, it means
19259 a thread from the process being debugged (the leading @samp{/} still
19260 needs to be present, or else @value{GDBN} will interpret the number as
19261 a process ID rather than a thread ID).
19263 @item info proc cmdline
19264 @cindex info proc cmdline
19265 Show the original command line of the process. This command is
19266 specific to @sc{gnu}/Linux.
19268 @item info proc cwd
19269 @cindex info proc cwd
19270 Show the current working directory of the process. This command is
19271 specific to @sc{gnu}/Linux.
19273 @item info proc exe
19274 @cindex info proc exe
19275 Show the name of executable of the process. This command is specific
19278 @item info proc mappings
19279 @cindex memory address space mappings
19280 Report the memory address space ranges accessible in the program, with
19281 information on whether the process has read, write, or execute access
19282 rights to each range. On @sc{gnu}/Linux systems, each memory range
19283 includes the object file which is mapped to that range, instead of the
19284 memory access rights to that range.
19286 @item info proc stat
19287 @itemx info proc status
19288 @cindex process detailed status information
19289 These subcommands are specific to @sc{gnu}/Linux systems. They show
19290 the process-related information, including the user ID and group ID;
19291 how many threads are there in the process; its virtual memory usage;
19292 the signals that are pending, blocked, and ignored; its TTY; its
19293 consumption of system and user time; its stack size; its @samp{nice}
19294 value; etc. For more information, see the @samp{proc} man page
19295 (type @kbd{man 5 proc} from your shell prompt).
19297 @item info proc all
19298 Show all the information about the process described under all of the
19299 above @code{info proc} subcommands.
19302 @comment These sub-options of 'info proc' were not included when
19303 @comment procfs.c was re-written. Keep their descriptions around
19304 @comment against the day when someone finds the time to put them back in.
19305 @kindex info proc times
19306 @item info proc times
19307 Starting time, user CPU time, and system CPU time for your program and
19310 @kindex info proc id
19312 Report on the process IDs related to your program: its own process ID,
19313 the ID of its parent, the process group ID, and the session ID.
19316 @item set procfs-trace
19317 @kindex set procfs-trace
19318 @cindex @code{procfs} API calls
19319 This command enables and disables tracing of @code{procfs} API calls.
19321 @item show procfs-trace
19322 @kindex show procfs-trace
19323 Show the current state of @code{procfs} API call tracing.
19325 @item set procfs-file @var{file}
19326 @kindex set procfs-file
19327 Tell @value{GDBN} to write @code{procfs} API trace to the named
19328 @var{file}. @value{GDBN} appends the trace info to the previous
19329 contents of the file. The default is to display the trace on the
19332 @item show procfs-file
19333 @kindex show procfs-file
19334 Show the file to which @code{procfs} API trace is written.
19336 @item proc-trace-entry
19337 @itemx proc-trace-exit
19338 @itemx proc-untrace-entry
19339 @itemx proc-untrace-exit
19340 @kindex proc-trace-entry
19341 @kindex proc-trace-exit
19342 @kindex proc-untrace-entry
19343 @kindex proc-untrace-exit
19344 These commands enable and disable tracing of entries into and exits
19345 from the @code{syscall} interface.
19348 @kindex info pidlist
19349 @cindex process list, QNX Neutrino
19350 For QNX Neutrino only, this command displays the list of all the
19351 processes and all the threads within each process.
19354 @kindex info meminfo
19355 @cindex mapinfo list, QNX Neutrino
19356 For QNX Neutrino only, this command displays the list of all mapinfos.
19360 @subsection Features for Debugging @sc{djgpp} Programs
19361 @cindex @sc{djgpp} debugging
19362 @cindex native @sc{djgpp} debugging
19363 @cindex MS-DOS-specific commands
19366 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19367 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19368 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19369 top of real-mode DOS systems and their emulations.
19371 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19372 defines a few commands specific to the @sc{djgpp} port. This
19373 subsection describes those commands.
19378 This is a prefix of @sc{djgpp}-specific commands which print
19379 information about the target system and important OS structures.
19382 @cindex MS-DOS system info
19383 @cindex free memory information (MS-DOS)
19384 @item info dos sysinfo
19385 This command displays assorted information about the underlying
19386 platform: the CPU type and features, the OS version and flavor, the
19387 DPMI version, and the available conventional and DPMI memory.
19392 @cindex segment descriptor tables
19393 @cindex descriptor tables display
19395 @itemx info dos ldt
19396 @itemx info dos idt
19397 These 3 commands display entries from, respectively, Global, Local,
19398 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19399 tables are data structures which store a descriptor for each segment
19400 that is currently in use. The segment's selector is an index into a
19401 descriptor table; the table entry for that index holds the
19402 descriptor's base address and limit, and its attributes and access
19405 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19406 segment (used for both data and the stack), and a DOS segment (which
19407 allows access to DOS/BIOS data structures and absolute addresses in
19408 conventional memory). However, the DPMI host will usually define
19409 additional segments in order to support the DPMI environment.
19411 @cindex garbled pointers
19412 These commands allow to display entries from the descriptor tables.
19413 Without an argument, all entries from the specified table are
19414 displayed. An argument, which should be an integer expression, means
19415 display a single entry whose index is given by the argument. For
19416 example, here's a convenient way to display information about the
19417 debugged program's data segment:
19420 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19421 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19425 This comes in handy when you want to see whether a pointer is outside
19426 the data segment's limit (i.e.@: @dfn{garbled}).
19428 @cindex page tables display (MS-DOS)
19430 @itemx info dos pte
19431 These two commands display entries from, respectively, the Page
19432 Directory and the Page Tables. Page Directories and Page Tables are
19433 data structures which control how virtual memory addresses are mapped
19434 into physical addresses. A Page Table includes an entry for every
19435 page of memory that is mapped into the program's address space; there
19436 may be several Page Tables, each one holding up to 4096 entries. A
19437 Page Directory has up to 4096 entries, one each for every Page Table
19438 that is currently in use.
19440 Without an argument, @kbd{info dos pde} displays the entire Page
19441 Directory, and @kbd{info dos pte} displays all the entries in all of
19442 the Page Tables. An argument, an integer expression, given to the
19443 @kbd{info dos pde} command means display only that entry from the Page
19444 Directory table. An argument given to the @kbd{info dos pte} command
19445 means display entries from a single Page Table, the one pointed to by
19446 the specified entry in the Page Directory.
19448 @cindex direct memory access (DMA) on MS-DOS
19449 These commands are useful when your program uses @dfn{DMA} (Direct
19450 Memory Access), which needs physical addresses to program the DMA
19453 These commands are supported only with some DPMI servers.
19455 @cindex physical address from linear address
19456 @item info dos address-pte @var{addr}
19457 This command displays the Page Table entry for a specified linear
19458 address. The argument @var{addr} is a linear address which should
19459 already have the appropriate segment's base address added to it,
19460 because this command accepts addresses which may belong to @emph{any}
19461 segment. For example, here's how to display the Page Table entry for
19462 the page where a variable @code{i} is stored:
19465 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19466 @exdent @code{Page Table entry for address 0x11a00d30:}
19467 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19471 This says that @code{i} is stored at offset @code{0xd30} from the page
19472 whose physical base address is @code{0x02698000}, and shows all the
19473 attributes of that page.
19475 Note that you must cast the addresses of variables to a @code{char *},
19476 since otherwise the value of @code{__djgpp_base_address}, the base
19477 address of all variables and functions in a @sc{djgpp} program, will
19478 be added using the rules of C pointer arithmetics: if @code{i} is
19479 declared an @code{int}, @value{GDBN} will add 4 times the value of
19480 @code{__djgpp_base_address} to the address of @code{i}.
19482 Here's another example, it displays the Page Table entry for the
19486 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19487 @exdent @code{Page Table entry for address 0x29110:}
19488 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19492 (The @code{+ 3} offset is because the transfer buffer's address is the
19493 3rd member of the @code{_go32_info_block} structure.) The output
19494 clearly shows that this DPMI server maps the addresses in conventional
19495 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19496 linear (@code{0x29110}) addresses are identical.
19498 This command is supported only with some DPMI servers.
19501 @cindex DOS serial data link, remote debugging
19502 In addition to native debugging, the DJGPP port supports remote
19503 debugging via a serial data link. The following commands are specific
19504 to remote serial debugging in the DJGPP port of @value{GDBN}.
19507 @kindex set com1base
19508 @kindex set com1irq
19509 @kindex set com2base
19510 @kindex set com2irq
19511 @kindex set com3base
19512 @kindex set com3irq
19513 @kindex set com4base
19514 @kindex set com4irq
19515 @item set com1base @var{addr}
19516 This command sets the base I/O port address of the @file{COM1} serial
19519 @item set com1irq @var{irq}
19520 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19521 for the @file{COM1} serial port.
19523 There are similar commands @samp{set com2base}, @samp{set com3irq},
19524 etc.@: for setting the port address and the @code{IRQ} lines for the
19527 @kindex show com1base
19528 @kindex show com1irq
19529 @kindex show com2base
19530 @kindex show com2irq
19531 @kindex show com3base
19532 @kindex show com3irq
19533 @kindex show com4base
19534 @kindex show com4irq
19535 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19536 display the current settings of the base address and the @code{IRQ}
19537 lines used by the COM ports.
19540 @kindex info serial
19541 @cindex DOS serial port status
19542 This command prints the status of the 4 DOS serial ports. For each
19543 port, it prints whether it's active or not, its I/O base address and
19544 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19545 counts of various errors encountered so far.
19549 @node Cygwin Native
19550 @subsection Features for Debugging MS Windows PE Executables
19551 @cindex MS Windows debugging
19552 @cindex native Cygwin debugging
19553 @cindex Cygwin-specific commands
19555 @value{GDBN} supports native debugging of MS Windows programs, including
19556 DLLs with and without symbolic debugging information.
19558 @cindex Ctrl-BREAK, MS-Windows
19559 @cindex interrupt debuggee on MS-Windows
19560 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19561 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19562 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19563 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19564 sequence, which can be used to interrupt the debuggee even if it
19567 There are various additional Cygwin-specific commands, described in
19568 this section. Working with DLLs that have no debugging symbols is
19569 described in @ref{Non-debug DLL Symbols}.
19574 This is a prefix of MS Windows-specific commands which print
19575 information about the target system and important OS structures.
19577 @item info w32 selector
19578 This command displays information returned by
19579 the Win32 API @code{GetThreadSelectorEntry} function.
19580 It takes an optional argument that is evaluated to
19581 a long value to give the information about this given selector.
19582 Without argument, this command displays information
19583 about the six segment registers.
19585 @item info w32 thread-information-block
19586 This command displays thread specific information stored in the
19587 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19588 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19592 This is a Cygwin-specific alias of @code{info shared}.
19594 @kindex dll-symbols
19596 This command loads symbols from a dll similarly to
19597 add-sym command but without the need to specify a base address.
19599 @kindex set cygwin-exceptions
19600 @cindex debugging the Cygwin DLL
19601 @cindex Cygwin DLL, debugging
19602 @item set cygwin-exceptions @var{mode}
19603 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19604 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19605 @value{GDBN} will delay recognition of exceptions, and may ignore some
19606 exceptions which seem to be caused by internal Cygwin DLL
19607 ``bookkeeping''. This option is meant primarily for debugging the
19608 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19609 @value{GDBN} users with false @code{SIGSEGV} signals.
19611 @kindex show cygwin-exceptions
19612 @item show cygwin-exceptions
19613 Displays whether @value{GDBN} will break on exceptions that happen
19614 inside the Cygwin DLL itself.
19616 @kindex set new-console
19617 @item set new-console @var{mode}
19618 If @var{mode} is @code{on} the debuggee will
19619 be started in a new console on next start.
19620 If @var{mode} is @code{off}, the debuggee will
19621 be started in the same console as the debugger.
19623 @kindex show new-console
19624 @item show new-console
19625 Displays whether a new console is used
19626 when the debuggee is started.
19628 @kindex set new-group
19629 @item set new-group @var{mode}
19630 This boolean value controls whether the debuggee should
19631 start a new group or stay in the same group as the debugger.
19632 This affects the way the Windows OS handles
19635 @kindex show new-group
19636 @item show new-group
19637 Displays current value of new-group boolean.
19639 @kindex set debugevents
19640 @item set debugevents
19641 This boolean value adds debug output concerning kernel events related
19642 to the debuggee seen by the debugger. This includes events that
19643 signal thread and process creation and exit, DLL loading and
19644 unloading, console interrupts, and debugging messages produced by the
19645 Windows @code{OutputDebugString} API call.
19647 @kindex set debugexec
19648 @item set debugexec
19649 This boolean value adds debug output concerning execute events
19650 (such as resume thread) seen by the debugger.
19652 @kindex set debugexceptions
19653 @item set debugexceptions
19654 This boolean value adds debug output concerning exceptions in the
19655 debuggee seen by the debugger.
19657 @kindex set debugmemory
19658 @item set debugmemory
19659 This boolean value adds debug output concerning debuggee memory reads
19660 and writes by the debugger.
19664 This boolean values specifies whether the debuggee is called
19665 via a shell or directly (default value is on).
19669 Displays if the debuggee will be started with a shell.
19674 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19677 @node Non-debug DLL Symbols
19678 @subsubsection Support for DLLs without Debugging Symbols
19679 @cindex DLLs with no debugging symbols
19680 @cindex Minimal symbols and DLLs
19682 Very often on windows, some of the DLLs that your program relies on do
19683 not include symbolic debugging information (for example,
19684 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19685 symbols in a DLL, it relies on the minimal amount of symbolic
19686 information contained in the DLL's export table. This section
19687 describes working with such symbols, known internally to @value{GDBN} as
19688 ``minimal symbols''.
19690 Note that before the debugged program has started execution, no DLLs
19691 will have been loaded. The easiest way around this problem is simply to
19692 start the program --- either by setting a breakpoint or letting the
19693 program run once to completion. It is also possible to force
19694 @value{GDBN} to load a particular DLL before starting the executable ---
19695 see the shared library information in @ref{Files}, or the
19696 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19697 explicitly loading symbols from a DLL with no debugging information will
19698 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19699 which may adversely affect symbol lookup performance.
19701 @subsubsection DLL Name Prefixes
19703 In keeping with the naming conventions used by the Microsoft debugging
19704 tools, DLL export symbols are made available with a prefix based on the
19705 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19706 also entered into the symbol table, so @code{CreateFileA} is often
19707 sufficient. In some cases there will be name clashes within a program
19708 (particularly if the executable itself includes full debugging symbols)
19709 necessitating the use of the fully qualified name when referring to the
19710 contents of the DLL. Use single-quotes around the name to avoid the
19711 exclamation mark (``!'') being interpreted as a language operator.
19713 Note that the internal name of the DLL may be all upper-case, even
19714 though the file name of the DLL is lower-case, or vice-versa. Since
19715 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19716 some confusion. If in doubt, try the @code{info functions} and
19717 @code{info variables} commands or even @code{maint print msymbols}
19718 (@pxref{Symbols}). Here's an example:
19721 (@value{GDBP}) info function CreateFileA
19722 All functions matching regular expression "CreateFileA":
19724 Non-debugging symbols:
19725 0x77e885f4 CreateFileA
19726 0x77e885f4 KERNEL32!CreateFileA
19730 (@value{GDBP}) info function !
19731 All functions matching regular expression "!":
19733 Non-debugging symbols:
19734 0x6100114c cygwin1!__assert
19735 0x61004034 cygwin1!_dll_crt0@@0
19736 0x61004240 cygwin1!dll_crt0(per_process *)
19740 @subsubsection Working with Minimal Symbols
19742 Symbols extracted from a DLL's export table do not contain very much
19743 type information. All that @value{GDBN} can do is guess whether a symbol
19744 refers to a function or variable depending on the linker section that
19745 contains the symbol. Also note that the actual contents of the memory
19746 contained in a DLL are not available unless the program is running. This
19747 means that you cannot examine the contents of a variable or disassemble
19748 a function within a DLL without a running program.
19750 Variables are generally treated as pointers and dereferenced
19751 automatically. For this reason, it is often necessary to prefix a
19752 variable name with the address-of operator (``&'') and provide explicit
19753 type information in the command. Here's an example of the type of
19757 (@value{GDBP}) print 'cygwin1!__argv'
19762 (@value{GDBP}) x 'cygwin1!__argv'
19763 0x10021610: "\230y\""
19766 And two possible solutions:
19769 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19770 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19774 (@value{GDBP}) x/2x &'cygwin1!__argv'
19775 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19776 (@value{GDBP}) x/x 0x10021608
19777 0x10021608: 0x0022fd98
19778 (@value{GDBP}) x/s 0x0022fd98
19779 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19782 Setting a break point within a DLL is possible even before the program
19783 starts execution. However, under these circumstances, @value{GDBN} can't
19784 examine the initial instructions of the function in order to skip the
19785 function's frame set-up code. You can work around this by using ``*&''
19786 to set the breakpoint at a raw memory address:
19789 (@value{GDBP}) break *&'python22!PyOS_Readline'
19790 Breakpoint 1 at 0x1e04eff0
19793 The author of these extensions is not entirely convinced that setting a
19794 break point within a shared DLL like @file{kernel32.dll} is completely
19798 @subsection Commands Specific to @sc{gnu} Hurd Systems
19799 @cindex @sc{gnu} Hurd debugging
19801 This subsection describes @value{GDBN} commands specific to the
19802 @sc{gnu} Hurd native debugging.
19807 @kindex set signals@r{, Hurd command}
19808 @kindex set sigs@r{, Hurd command}
19809 This command toggles the state of inferior signal interception by
19810 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19811 affected by this command. @code{sigs} is a shorthand alias for
19816 @kindex show signals@r{, Hurd command}
19817 @kindex show sigs@r{, Hurd command}
19818 Show the current state of intercepting inferior's signals.
19820 @item set signal-thread
19821 @itemx set sigthread
19822 @kindex set signal-thread
19823 @kindex set sigthread
19824 This command tells @value{GDBN} which thread is the @code{libc} signal
19825 thread. That thread is run when a signal is delivered to a running
19826 process. @code{set sigthread} is the shorthand alias of @code{set
19829 @item show signal-thread
19830 @itemx show sigthread
19831 @kindex show signal-thread
19832 @kindex show sigthread
19833 These two commands show which thread will run when the inferior is
19834 delivered a signal.
19837 @kindex set stopped@r{, Hurd command}
19838 This commands tells @value{GDBN} that the inferior process is stopped,
19839 as with the @code{SIGSTOP} signal. The stopped process can be
19840 continued by delivering a signal to it.
19843 @kindex show stopped@r{, Hurd command}
19844 This command shows whether @value{GDBN} thinks the debuggee is
19847 @item set exceptions
19848 @kindex set exceptions@r{, Hurd command}
19849 Use this command to turn off trapping of exceptions in the inferior.
19850 When exception trapping is off, neither breakpoints nor
19851 single-stepping will work. To restore the default, set exception
19854 @item show exceptions
19855 @kindex show exceptions@r{, Hurd command}
19856 Show the current state of trapping exceptions in the inferior.
19858 @item set task pause
19859 @kindex set task@r{, Hurd commands}
19860 @cindex task attributes (@sc{gnu} Hurd)
19861 @cindex pause current task (@sc{gnu} Hurd)
19862 This command toggles task suspension when @value{GDBN} has control.
19863 Setting it to on takes effect immediately, and the task is suspended
19864 whenever @value{GDBN} gets control. Setting it to off will take
19865 effect the next time the inferior is continued. If this option is set
19866 to off, you can use @code{set thread default pause on} or @code{set
19867 thread pause on} (see below) to pause individual threads.
19869 @item show task pause
19870 @kindex show task@r{, Hurd commands}
19871 Show the current state of task suspension.
19873 @item set task detach-suspend-count
19874 @cindex task suspend count
19875 @cindex detach from task, @sc{gnu} Hurd
19876 This command sets the suspend count the task will be left with when
19877 @value{GDBN} detaches from it.
19879 @item show task detach-suspend-count
19880 Show the suspend count the task will be left with when detaching.
19882 @item set task exception-port
19883 @itemx set task excp
19884 @cindex task exception port, @sc{gnu} Hurd
19885 This command sets the task exception port to which @value{GDBN} will
19886 forward exceptions. The argument should be the value of the @dfn{send
19887 rights} of the task. @code{set task excp} is a shorthand alias.
19889 @item set noninvasive
19890 @cindex noninvasive task options
19891 This command switches @value{GDBN} to a mode that is the least
19892 invasive as far as interfering with the inferior is concerned. This
19893 is the same as using @code{set task pause}, @code{set exceptions}, and
19894 @code{set signals} to values opposite to the defaults.
19896 @item info send-rights
19897 @itemx info receive-rights
19898 @itemx info port-rights
19899 @itemx info port-sets
19900 @itemx info dead-names
19903 @cindex send rights, @sc{gnu} Hurd
19904 @cindex receive rights, @sc{gnu} Hurd
19905 @cindex port rights, @sc{gnu} Hurd
19906 @cindex port sets, @sc{gnu} Hurd
19907 @cindex dead names, @sc{gnu} Hurd
19908 These commands display information about, respectively, send rights,
19909 receive rights, port rights, port sets, and dead names of a task.
19910 There are also shorthand aliases: @code{info ports} for @code{info
19911 port-rights} and @code{info psets} for @code{info port-sets}.
19913 @item set thread pause
19914 @kindex set thread@r{, Hurd command}
19915 @cindex thread properties, @sc{gnu} Hurd
19916 @cindex pause current thread (@sc{gnu} Hurd)
19917 This command toggles current thread suspension when @value{GDBN} has
19918 control. Setting it to on takes effect immediately, and the current
19919 thread is suspended whenever @value{GDBN} gets control. Setting it to
19920 off will take effect the next time the inferior is continued.
19921 Normally, this command has no effect, since when @value{GDBN} has
19922 control, the whole task is suspended. However, if you used @code{set
19923 task pause off} (see above), this command comes in handy to suspend
19924 only the current thread.
19926 @item show thread pause
19927 @kindex show thread@r{, Hurd command}
19928 This command shows the state of current thread suspension.
19930 @item set thread run
19931 This command sets whether the current thread is allowed to run.
19933 @item show thread run
19934 Show whether the current thread is allowed to run.
19936 @item set thread detach-suspend-count
19937 @cindex thread suspend count, @sc{gnu} Hurd
19938 @cindex detach from thread, @sc{gnu} Hurd
19939 This command sets the suspend count @value{GDBN} will leave on a
19940 thread when detaching. This number is relative to the suspend count
19941 found by @value{GDBN} when it notices the thread; use @code{set thread
19942 takeover-suspend-count} to force it to an absolute value.
19944 @item show thread detach-suspend-count
19945 Show the suspend count @value{GDBN} will leave on the thread when
19948 @item set thread exception-port
19949 @itemx set thread excp
19950 Set the thread exception port to which to forward exceptions. This
19951 overrides the port set by @code{set task exception-port} (see above).
19952 @code{set thread excp} is the shorthand alias.
19954 @item set thread takeover-suspend-count
19955 Normally, @value{GDBN}'s thread suspend counts are relative to the
19956 value @value{GDBN} finds when it notices each thread. This command
19957 changes the suspend counts to be absolute instead.
19959 @item set thread default
19960 @itemx show thread default
19961 @cindex thread default settings, @sc{gnu} Hurd
19962 Each of the above @code{set thread} commands has a @code{set thread
19963 default} counterpart (e.g., @code{set thread default pause}, @code{set
19964 thread default exception-port}, etc.). The @code{thread default}
19965 variety of commands sets the default thread properties for all
19966 threads; you can then change the properties of individual threads with
19967 the non-default commands.
19974 @value{GDBN} provides the following commands specific to the Darwin target:
19977 @item set debug darwin @var{num}
19978 @kindex set debug darwin
19979 When set to a non zero value, enables debugging messages specific to
19980 the Darwin support. Higher values produce more verbose output.
19982 @item show debug darwin
19983 @kindex show debug darwin
19984 Show the current state of Darwin messages.
19986 @item set debug mach-o @var{num}
19987 @kindex set debug mach-o
19988 When set to a non zero value, enables debugging messages while
19989 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19990 file format used on Darwin for object and executable files.) Higher
19991 values produce more verbose output. This is a command to diagnose
19992 problems internal to @value{GDBN} and should not be needed in normal
19995 @item show debug mach-o
19996 @kindex show debug mach-o
19997 Show the current state of Mach-O file messages.
19999 @item set mach-exceptions on
20000 @itemx set mach-exceptions off
20001 @kindex set mach-exceptions
20002 On Darwin, faults are first reported as a Mach exception and are then
20003 mapped to a Posix signal. Use this command to turn on trapping of
20004 Mach exceptions in the inferior. This might be sometimes useful to
20005 better understand the cause of a fault. The default is off.
20007 @item show mach-exceptions
20008 @kindex show mach-exceptions
20009 Show the current state of exceptions trapping.
20014 @section Embedded Operating Systems
20016 This section describes configurations involving the debugging of
20017 embedded operating systems that are available for several different
20021 * VxWorks:: Using @value{GDBN} with VxWorks
20024 @value{GDBN} includes the ability to debug programs running on
20025 various real-time operating systems.
20028 @subsection Using @value{GDBN} with VxWorks
20034 @kindex target vxworks
20035 @item target vxworks @var{machinename}
20036 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
20037 is the target system's machine name or IP address.
20041 On VxWorks, @code{load} links @var{filename} dynamically on the
20042 current target system as well as adding its symbols in @value{GDBN}.
20044 @value{GDBN} enables developers to spawn and debug tasks running on networked
20045 VxWorks targets from a Unix host. Already-running tasks spawned from
20046 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
20047 both the Unix host and on the VxWorks target. The program
20048 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
20049 installed with the name @code{vxgdb}, to distinguish it from a
20050 @value{GDBN} for debugging programs on the host itself.)
20053 @item VxWorks-timeout @var{args}
20054 @kindex vxworks-timeout
20055 All VxWorks-based targets now support the option @code{vxworks-timeout}.
20056 This option is set by the user, and @var{args} represents the number of
20057 seconds @value{GDBN} waits for responses to rpc's. You might use this if
20058 your VxWorks target is a slow software simulator or is on the far side
20059 of a thin network line.
20062 The following information on connecting to VxWorks was current when
20063 this manual was produced; newer releases of VxWorks may use revised
20066 @findex INCLUDE_RDB
20067 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
20068 to include the remote debugging interface routines in the VxWorks
20069 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
20070 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
20071 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
20072 source debugging task @code{tRdbTask} when VxWorks is booted. For more
20073 information on configuring and remaking VxWorks, see the manufacturer's
20075 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20077 Once you have included @file{rdb.a} in your VxWorks system image and set
20078 your Unix execution search path to find @value{GDBN}, you are ready to
20079 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20080 @code{vxgdb}, depending on your installation).
20082 @value{GDBN} comes up showing the prompt:
20089 * VxWorks Connection:: Connecting to VxWorks
20090 * VxWorks Download:: VxWorks download
20091 * VxWorks Attach:: Running tasks
20094 @node VxWorks Connection
20095 @subsubsection Connecting to VxWorks
20097 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20098 network. To connect to a target whose host name is ``@code{tt}'', type:
20101 (vxgdb) target vxworks tt
20105 @value{GDBN} displays messages like these:
20108 Attaching remote machine across net...
20113 @value{GDBN} then attempts to read the symbol tables of any object modules
20114 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20115 these files by searching the directories listed in the command search
20116 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20117 to find an object file, it displays a message such as:
20120 prog.o: No such file or directory.
20123 When this happens, add the appropriate directory to the search path with
20124 the @value{GDBN} command @code{path}, and execute the @code{target}
20127 @node VxWorks Download
20128 @subsubsection VxWorks Download
20130 @cindex download to VxWorks
20131 If you have connected to the VxWorks target and you want to debug an
20132 object that has not yet been loaded, you can use the @value{GDBN}
20133 @code{load} command to download a file from Unix to VxWorks
20134 incrementally. The object file given as an argument to the @code{load}
20135 command is actually opened twice: first by the VxWorks target in order
20136 to download the code, then by @value{GDBN} in order to read the symbol
20137 table. This can lead to problems if the current working directories on
20138 the two systems differ. If both systems have NFS mounted the same
20139 filesystems, you can avoid these problems by using absolute paths.
20140 Otherwise, it is simplest to set the working directory on both systems
20141 to the directory in which the object file resides, and then to reference
20142 the file by its name, without any path. For instance, a program
20143 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20144 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20145 program, type this on VxWorks:
20148 -> cd "@var{vxpath}/vw/demo/rdb"
20152 Then, in @value{GDBN}, type:
20155 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20156 (vxgdb) load prog.o
20159 @value{GDBN} displays a response similar to this:
20162 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20165 You can also use the @code{load} command to reload an object module
20166 after editing and recompiling the corresponding source file. Note that
20167 this makes @value{GDBN} delete all currently-defined breakpoints,
20168 auto-displays, and convenience variables, and to clear the value
20169 history. (This is necessary in order to preserve the integrity of
20170 debugger's data structures that reference the target system's symbol
20173 @node VxWorks Attach
20174 @subsubsection Running Tasks
20176 @cindex running VxWorks tasks
20177 You can also attach to an existing task using the @code{attach} command as
20181 (vxgdb) attach @var{task}
20185 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20186 or suspended when you attach to it. Running tasks are suspended at
20187 the time of attachment.
20189 @node Embedded Processors
20190 @section Embedded Processors
20192 This section goes into details specific to particular embedded
20195 @cindex send command to simulator
20196 Whenever a specific embedded processor has a simulator, @value{GDBN}
20197 allows to send an arbitrary command to the simulator.
20200 @item sim @var{command}
20201 @kindex sim@r{, a command}
20202 Send an arbitrary @var{command} string to the simulator. Consult the
20203 documentation for the specific simulator in use for information about
20204 acceptable commands.
20210 * M32R/D:: Renesas M32R/D
20211 * M68K:: Motorola M68K
20212 * MicroBlaze:: Xilinx MicroBlaze
20213 * MIPS Embedded:: MIPS Embedded
20214 * PowerPC Embedded:: PowerPC Embedded
20215 * PA:: HP PA Embedded
20216 * Sparclet:: Tsqware Sparclet
20217 * Sparclite:: Fujitsu Sparclite
20218 * Z8000:: Zilog Z8000
20221 * Super-H:: Renesas Super-H
20230 @item target rdi @var{dev}
20231 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20232 use this target to communicate with both boards running the Angel
20233 monitor, or with the EmbeddedICE JTAG debug device.
20236 @item target rdp @var{dev}
20241 @value{GDBN} provides the following ARM-specific commands:
20244 @item set arm disassembler
20246 This commands selects from a list of disassembly styles. The
20247 @code{"std"} style is the standard style.
20249 @item show arm disassembler
20251 Show the current disassembly style.
20253 @item set arm apcs32
20254 @cindex ARM 32-bit mode
20255 This command toggles ARM operation mode between 32-bit and 26-bit.
20257 @item show arm apcs32
20258 Display the current usage of the ARM 32-bit mode.
20260 @item set arm fpu @var{fputype}
20261 This command sets the ARM floating-point unit (FPU) type. The
20262 argument @var{fputype} can be one of these:
20266 Determine the FPU type by querying the OS ABI.
20268 Software FPU, with mixed-endian doubles on little-endian ARM
20271 GCC-compiled FPA co-processor.
20273 Software FPU with pure-endian doubles.
20279 Show the current type of the FPU.
20282 This command forces @value{GDBN} to use the specified ABI.
20285 Show the currently used ABI.
20287 @item set arm fallback-mode (arm|thumb|auto)
20288 @value{GDBN} uses the symbol table, when available, to determine
20289 whether instructions are ARM or Thumb. This command controls
20290 @value{GDBN}'s default behavior when the symbol table is not
20291 available. The default is @samp{auto}, which causes @value{GDBN} to
20292 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20295 @item show arm fallback-mode
20296 Show the current fallback instruction mode.
20298 @item set arm force-mode (arm|thumb|auto)
20299 This command overrides use of the symbol table to determine whether
20300 instructions are ARM or Thumb. The default is @samp{auto}, which
20301 causes @value{GDBN} to use the symbol table and then the setting
20302 of @samp{set arm fallback-mode}.
20304 @item show arm force-mode
20305 Show the current forced instruction mode.
20307 @item set debug arm
20308 Toggle whether to display ARM-specific debugging messages from the ARM
20309 target support subsystem.
20311 @item show debug arm
20312 Show whether ARM-specific debugging messages are enabled.
20315 The following commands are available when an ARM target is debugged
20316 using the RDI interface:
20319 @item rdilogfile @r{[}@var{file}@r{]}
20321 @cindex ADP (Angel Debugger Protocol) logging
20322 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20323 With an argument, sets the log file to the specified @var{file}. With
20324 no argument, show the current log file name. The default log file is
20327 @item rdilogenable @r{[}@var{arg}@r{]}
20328 @kindex rdilogenable
20329 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20330 enables logging, with an argument 0 or @code{"no"} disables it. With
20331 no arguments displays the current setting. When logging is enabled,
20332 ADP packets exchanged between @value{GDBN} and the RDI target device
20333 are logged to a file.
20335 @item set rdiromatzero
20336 @kindex set rdiromatzero
20337 @cindex ROM at zero address, RDI
20338 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20339 vector catching is disabled, so that zero address can be used. If off
20340 (the default), vector catching is enabled. For this command to take
20341 effect, it needs to be invoked prior to the @code{target rdi} command.
20343 @item show rdiromatzero
20344 @kindex show rdiromatzero
20345 Show the current setting of ROM at zero address.
20347 @item set rdiheartbeat
20348 @kindex set rdiheartbeat
20349 @cindex RDI heartbeat
20350 Enable or disable RDI heartbeat packets. It is not recommended to
20351 turn on this option, since it confuses ARM and EPI JTAG interface, as
20352 well as the Angel monitor.
20354 @item show rdiheartbeat
20355 @kindex show rdiheartbeat
20356 Show the setting of RDI heartbeat packets.
20360 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20361 The @value{GDBN} ARM simulator accepts the following optional arguments.
20364 @item --swi-support=@var{type}
20365 Tell the simulator which SWI interfaces to support.
20366 @var{type} may be a comma separated list of the following values.
20367 The default value is @code{all}.
20380 @subsection Renesas M32R/D and M32R/SDI
20383 @kindex target m32r
20384 @item target m32r @var{dev}
20385 Renesas M32R/D ROM monitor.
20387 @kindex target m32rsdi
20388 @item target m32rsdi @var{dev}
20389 Renesas M32R SDI server, connected via parallel port to the board.
20392 The following @value{GDBN} commands are specific to the M32R monitor:
20395 @item set download-path @var{path}
20396 @kindex set download-path
20397 @cindex find downloadable @sc{srec} files (M32R)
20398 Set the default path for finding downloadable @sc{srec} files.
20400 @item show download-path
20401 @kindex show download-path
20402 Show the default path for downloadable @sc{srec} files.
20404 @item set board-address @var{addr}
20405 @kindex set board-address
20406 @cindex M32-EVA target board address
20407 Set the IP address for the M32R-EVA target board.
20409 @item show board-address
20410 @kindex show board-address
20411 Show the current IP address of the target board.
20413 @item set server-address @var{addr}
20414 @kindex set server-address
20415 @cindex download server address (M32R)
20416 Set the IP address for the download server, which is the @value{GDBN}'s
20419 @item show server-address
20420 @kindex show server-address
20421 Display the IP address of the download server.
20423 @item upload @r{[}@var{file}@r{]}
20424 @kindex upload@r{, M32R}
20425 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20426 upload capability. If no @var{file} argument is given, the current
20427 executable file is uploaded.
20429 @item tload @r{[}@var{file}@r{]}
20430 @kindex tload@r{, M32R}
20431 Test the @code{upload} command.
20434 The following commands are available for M32R/SDI:
20439 @cindex reset SDI connection, M32R
20440 This command resets the SDI connection.
20444 This command shows the SDI connection status.
20447 @kindex debug_chaos
20448 @cindex M32R/Chaos debugging
20449 Instructs the remote that M32R/Chaos debugging is to be used.
20451 @item use_debug_dma
20452 @kindex use_debug_dma
20453 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20456 @kindex use_mon_code
20457 Instructs the remote to use the MON_CODE method of accessing memory.
20460 @kindex use_ib_break
20461 Instructs the remote to set breakpoints by IB break.
20463 @item use_dbt_break
20464 @kindex use_dbt_break
20465 Instructs the remote to set breakpoints by DBT.
20471 The Motorola m68k configuration includes ColdFire support, and a
20472 target command for the following ROM monitor.
20476 @kindex target dbug
20477 @item target dbug @var{dev}
20478 dBUG ROM monitor for Motorola ColdFire.
20483 @subsection MicroBlaze
20484 @cindex Xilinx MicroBlaze
20485 @cindex XMD, Xilinx Microprocessor Debugger
20487 The MicroBlaze is a soft-core processor supported on various Xilinx
20488 FPGAs, such as Spartan or Virtex series. Boards with these processors
20489 usually have JTAG ports which connect to a host system running the Xilinx
20490 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20491 This host system is used to download the configuration bitstream to
20492 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20493 communicates with the target board using the JTAG interface and
20494 presents a @code{gdbserver} interface to the board. By default
20495 @code{xmd} uses port @code{1234}. (While it is possible to change
20496 this default port, it requires the use of undocumented @code{xmd}
20497 commands. Contact Xilinx support if you need to do this.)
20499 Use these GDB commands to connect to the MicroBlaze target processor.
20502 @item target remote :1234
20503 Use this command to connect to the target if you are running @value{GDBN}
20504 on the same system as @code{xmd}.
20506 @item target remote @var{xmd-host}:1234
20507 Use this command to connect to the target if it is connected to @code{xmd}
20508 running on a different system named @var{xmd-host}.
20511 Use this command to download a program to the MicroBlaze target.
20513 @item set debug microblaze @var{n}
20514 Enable MicroBlaze-specific debugging messages if non-zero.
20516 @item show debug microblaze @var{n}
20517 Show MicroBlaze-specific debugging level.
20520 @node MIPS Embedded
20521 @subsection @acronym{MIPS} Embedded
20523 @cindex @acronym{MIPS} boards
20524 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20525 @acronym{MIPS} board attached to a serial line. This is available when
20526 you configure @value{GDBN} with @samp{--target=mips-elf}.
20529 Use these @value{GDBN} commands to specify the connection to your target board:
20532 @item target mips @var{port}
20533 @kindex target mips @var{port}
20534 To run a program on the board, start up @code{@value{GDBP}} with the
20535 name of your program as the argument. To connect to the board, use the
20536 command @samp{target mips @var{port}}, where @var{port} is the name of
20537 the serial port connected to the board. If the program has not already
20538 been downloaded to the board, you may use the @code{load} command to
20539 download it. You can then use all the usual @value{GDBN} commands.
20541 For example, this sequence connects to the target board through a serial
20542 port, and loads and runs a program called @var{prog} through the
20546 host$ @value{GDBP} @var{prog}
20547 @value{GDBN} is free software and @dots{}
20548 (@value{GDBP}) target mips /dev/ttyb
20549 (@value{GDBP}) load @var{prog}
20553 @item target mips @var{hostname}:@var{portnumber}
20554 On some @value{GDBN} host configurations, you can specify a TCP
20555 connection (for instance, to a serial line managed by a terminal
20556 concentrator) instead of a serial port, using the syntax
20557 @samp{@var{hostname}:@var{portnumber}}.
20559 @item target pmon @var{port}
20560 @kindex target pmon @var{port}
20563 @item target ddb @var{port}
20564 @kindex target ddb @var{port}
20565 NEC's DDB variant of PMON for Vr4300.
20567 @item target lsi @var{port}
20568 @kindex target lsi @var{port}
20569 LSI variant of PMON.
20571 @kindex target r3900
20572 @item target r3900 @var{dev}
20573 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20575 @kindex target array
20576 @item target array @var{dev}
20577 Array Tech LSI33K RAID controller board.
20583 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20586 @item set mipsfpu double
20587 @itemx set mipsfpu single
20588 @itemx set mipsfpu none
20589 @itemx set mipsfpu auto
20590 @itemx show mipsfpu
20591 @kindex set mipsfpu
20592 @kindex show mipsfpu
20593 @cindex @acronym{MIPS} remote floating point
20594 @cindex floating point, @acronym{MIPS} remote
20595 If your target board does not support the @acronym{MIPS} floating point
20596 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20597 need this, you may wish to put the command in your @value{GDBN} init
20598 file). This tells @value{GDBN} how to find the return value of
20599 functions which return floating point values. It also allows
20600 @value{GDBN} to avoid saving the floating point registers when calling
20601 functions on the board. If you are using a floating point coprocessor
20602 with only single precision floating point support, as on the @sc{r4650}
20603 processor, use the command @samp{set mipsfpu single}. The default
20604 double precision floating point coprocessor may be selected using
20605 @samp{set mipsfpu double}.
20607 In previous versions the only choices were double precision or no
20608 floating point, so @samp{set mipsfpu on} will select double precision
20609 and @samp{set mipsfpu off} will select no floating point.
20611 As usual, you can inquire about the @code{mipsfpu} variable with
20612 @samp{show mipsfpu}.
20614 @item set timeout @var{seconds}
20615 @itemx set retransmit-timeout @var{seconds}
20616 @itemx show timeout
20617 @itemx show retransmit-timeout
20618 @cindex @code{timeout}, @acronym{MIPS} protocol
20619 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20620 @kindex set timeout
20621 @kindex show timeout
20622 @kindex set retransmit-timeout
20623 @kindex show retransmit-timeout
20624 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20625 remote protocol, with the @code{set timeout @var{seconds}} command. The
20626 default is 5 seconds. Similarly, you can control the timeout used while
20627 waiting for an acknowledgment of a packet with the @code{set
20628 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20629 You can inspect both values with @code{show timeout} and @code{show
20630 retransmit-timeout}. (These commands are @emph{only} available when
20631 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20633 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20634 is waiting for your program to stop. In that case, @value{GDBN} waits
20635 forever because it has no way of knowing how long the program is going
20636 to run before stopping.
20638 @item set syn-garbage-limit @var{num}
20639 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20640 @cindex synchronize with remote @acronym{MIPS} target
20641 Limit the maximum number of characters @value{GDBN} should ignore when
20642 it tries to synchronize with the remote target. The default is 10
20643 characters. Setting the limit to -1 means there's no limit.
20645 @item show syn-garbage-limit
20646 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20647 Show the current limit on the number of characters to ignore when
20648 trying to synchronize with the remote system.
20650 @item set monitor-prompt @var{prompt}
20651 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20652 @cindex remote monitor prompt
20653 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20654 remote monitor. The default depends on the target:
20664 @item show monitor-prompt
20665 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20666 Show the current strings @value{GDBN} expects as the prompt from the
20669 @item set monitor-warnings
20670 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20671 Enable or disable monitor warnings about hardware breakpoints. This
20672 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20673 display warning messages whose codes are returned by the @code{lsi}
20674 PMON monitor for breakpoint commands.
20676 @item show monitor-warnings
20677 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20678 Show the current setting of printing monitor warnings.
20680 @item pmon @var{command}
20681 @kindex pmon@r{, @acronym{MIPS} remote}
20682 @cindex send PMON command
20683 This command allows sending an arbitrary @var{command} string to the
20684 monitor. The monitor must be in debug mode for this to work.
20687 @node PowerPC Embedded
20688 @subsection PowerPC Embedded
20690 @cindex DVC register
20691 @value{GDBN} supports using the DVC (Data Value Compare) register to
20692 implement in hardware simple hardware watchpoint conditions of the form:
20695 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20696 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20699 The DVC register will be automatically used when @value{GDBN} detects
20700 such pattern in a condition expression, and the created watchpoint uses one
20701 debug register (either the @code{exact-watchpoints} option is on and the
20702 variable is scalar, or the variable has a length of one byte). This feature
20703 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20706 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20707 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20708 in which case watchpoints using only one debug register are created when
20709 watching variables of scalar types.
20711 You can create an artificial array to watch an arbitrary memory
20712 region using one of the following commands (@pxref{Expressions}):
20715 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20716 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20719 PowerPC embedded processors support masked watchpoints. See the discussion
20720 about the @code{mask} argument in @ref{Set Watchpoints}.
20722 @cindex ranged breakpoint
20723 PowerPC embedded processors support hardware accelerated
20724 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20725 the inferior whenever it executes an instruction at any address within
20726 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20727 use the @code{break-range} command.
20729 @value{GDBN} provides the following PowerPC-specific commands:
20732 @kindex break-range
20733 @item break-range @var{start-location}, @var{end-location}
20734 Set a breakpoint for an address range.
20735 @var{start-location} and @var{end-location} can specify a function name,
20736 a line number, an offset of lines from the current line or from the start
20737 location, or an address of an instruction (see @ref{Specify Location},
20738 for a list of all the possible ways to specify a @var{location}.)
20739 The breakpoint will stop execution of the inferior whenever it
20740 executes an instruction at any address within the specified range,
20741 (including @var{start-location} and @var{end-location}.)
20743 @kindex set powerpc
20744 @item set powerpc soft-float
20745 @itemx show powerpc soft-float
20746 Force @value{GDBN} to use (or not use) a software floating point calling
20747 convention. By default, @value{GDBN} selects the calling convention based
20748 on the selected architecture and the provided executable file.
20750 @item set powerpc vector-abi
20751 @itemx show powerpc vector-abi
20752 Force @value{GDBN} to use the specified calling convention for vector
20753 arguments and return values. The valid options are @samp{auto};
20754 @samp{generic}, to avoid vector registers even if they are present;
20755 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20756 registers. By default, @value{GDBN} selects the calling convention
20757 based on the selected architecture and the provided executable file.
20759 @item set powerpc exact-watchpoints
20760 @itemx show powerpc exact-watchpoints
20761 Allow @value{GDBN} to use only one debug register when watching a variable
20762 of scalar type, thus assuming that the variable is accessed through the
20763 address of its first byte.
20765 @kindex target dink32
20766 @item target dink32 @var{dev}
20767 DINK32 ROM monitor.
20769 @kindex target ppcbug
20770 @item target ppcbug @var{dev}
20771 @kindex target ppcbug1
20772 @item target ppcbug1 @var{dev}
20773 PPCBUG ROM monitor for PowerPC.
20776 @item target sds @var{dev}
20777 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20780 @cindex SDS protocol
20781 The following commands specific to the SDS protocol are supported
20785 @item set sdstimeout @var{nsec}
20786 @kindex set sdstimeout
20787 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20788 default is 2 seconds.
20790 @item show sdstimeout
20791 @kindex show sdstimeout
20792 Show the current value of the SDS timeout.
20794 @item sds @var{command}
20795 @kindex sds@r{, a command}
20796 Send the specified @var{command} string to the SDS monitor.
20801 @subsection HP PA Embedded
20805 @kindex target op50n
20806 @item target op50n @var{dev}
20807 OP50N monitor, running on an OKI HPPA board.
20809 @kindex target w89k
20810 @item target w89k @var{dev}
20811 W89K monitor, running on a Winbond HPPA board.
20816 @subsection Tsqware Sparclet
20820 @value{GDBN} enables developers to debug tasks running on
20821 Sparclet targets from a Unix host.
20822 @value{GDBN} uses code that runs on
20823 both the Unix host and on the Sparclet target. The program
20824 @code{@value{GDBP}} is installed and executed on the Unix host.
20827 @item remotetimeout @var{args}
20828 @kindex remotetimeout
20829 @value{GDBN} supports the option @code{remotetimeout}.
20830 This option is set by the user, and @var{args} represents the number of
20831 seconds @value{GDBN} waits for responses.
20834 @cindex compiling, on Sparclet
20835 When compiling for debugging, include the options @samp{-g} to get debug
20836 information and @samp{-Ttext} to relocate the program to where you wish to
20837 load it on the target. You may also want to add the options @samp{-n} or
20838 @samp{-N} in order to reduce the size of the sections. Example:
20841 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20844 You can use @code{objdump} to verify that the addresses are what you intended:
20847 sparclet-aout-objdump --headers --syms prog
20850 @cindex running, on Sparclet
20852 your Unix execution search path to find @value{GDBN}, you are ready to
20853 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20854 (or @code{sparclet-aout-gdb}, depending on your installation).
20856 @value{GDBN} comes up showing the prompt:
20863 * Sparclet File:: Setting the file to debug
20864 * Sparclet Connection:: Connecting to Sparclet
20865 * Sparclet Download:: Sparclet download
20866 * Sparclet Execution:: Running and debugging
20869 @node Sparclet File
20870 @subsubsection Setting File to Debug
20872 The @value{GDBN} command @code{file} lets you choose with program to debug.
20875 (gdbslet) file prog
20879 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20880 @value{GDBN} locates
20881 the file by searching the directories listed in the command search
20883 If the file was compiled with debug information (option @samp{-g}), source
20884 files will be searched as well.
20885 @value{GDBN} locates
20886 the source files by searching the directories listed in the directory search
20887 path (@pxref{Environment, ,Your Program's Environment}).
20889 to find a file, it displays a message such as:
20892 prog: No such file or directory.
20895 When this happens, add the appropriate directories to the search paths with
20896 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20897 @code{target} command again.
20899 @node Sparclet Connection
20900 @subsubsection Connecting to Sparclet
20902 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20903 To connect to a target on serial port ``@code{ttya}'', type:
20906 (gdbslet) target sparclet /dev/ttya
20907 Remote target sparclet connected to /dev/ttya
20908 main () at ../prog.c:3
20912 @value{GDBN} displays messages like these:
20918 @node Sparclet Download
20919 @subsubsection Sparclet Download
20921 @cindex download to Sparclet
20922 Once connected to the Sparclet target,
20923 you can use the @value{GDBN}
20924 @code{load} command to download the file from the host to the target.
20925 The file name and load offset should be given as arguments to the @code{load}
20927 Since the file format is aout, the program must be loaded to the starting
20928 address. You can use @code{objdump} to find out what this value is. The load
20929 offset is an offset which is added to the VMA (virtual memory address)
20930 of each of the file's sections.
20931 For instance, if the program
20932 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20933 and bss at 0x12010170, in @value{GDBN}, type:
20936 (gdbslet) load prog 0x12010000
20937 Loading section .text, size 0xdb0 vma 0x12010000
20940 If the code is loaded at a different address then what the program was linked
20941 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20942 to tell @value{GDBN} where to map the symbol table.
20944 @node Sparclet Execution
20945 @subsubsection Running and Debugging
20947 @cindex running and debugging Sparclet programs
20948 You can now begin debugging the task using @value{GDBN}'s execution control
20949 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20950 manual for the list of commands.
20954 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20956 Starting program: prog
20957 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20958 3 char *symarg = 0;
20960 4 char *execarg = "hello!";
20965 @subsection Fujitsu Sparclite
20969 @kindex target sparclite
20970 @item target sparclite @var{dev}
20971 Fujitsu sparclite boards, used only for the purpose of loading.
20972 You must use an additional command to debug the program.
20973 For example: target remote @var{dev} using @value{GDBN} standard
20979 @subsection Zilog Z8000
20982 @cindex simulator, Z8000
20983 @cindex Zilog Z8000 simulator
20985 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20988 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20989 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20990 segmented variant). The simulator recognizes which architecture is
20991 appropriate by inspecting the object code.
20994 @item target sim @var{args}
20996 @kindex target sim@r{, with Z8000}
20997 Debug programs on a simulated CPU. If the simulator supports setup
20998 options, specify them via @var{args}.
21002 After specifying this target, you can debug programs for the simulated
21003 CPU in the same style as programs for your host computer; use the
21004 @code{file} command to load a new program image, the @code{run} command
21005 to run your program, and so on.
21007 As well as making available all the usual machine registers
21008 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
21009 additional items of information as specially named registers:
21014 Counts clock-ticks in the simulator.
21017 Counts instructions run in the simulator.
21020 Execution time in 60ths of a second.
21024 You can refer to these values in @value{GDBN} expressions with the usual
21025 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
21026 conditional breakpoint that suspends only after at least 5000
21027 simulated clock ticks.
21030 @subsection Atmel AVR
21033 When configured for debugging the Atmel AVR, @value{GDBN} supports the
21034 following AVR-specific commands:
21037 @item info io_registers
21038 @kindex info io_registers@r{, AVR}
21039 @cindex I/O registers (Atmel AVR)
21040 This command displays information about the AVR I/O registers. For
21041 each register, @value{GDBN} prints its number and value.
21048 When configured for debugging CRIS, @value{GDBN} provides the
21049 following CRIS-specific commands:
21052 @item set cris-version @var{ver}
21053 @cindex CRIS version
21054 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
21055 The CRIS version affects register names and sizes. This command is useful in
21056 case autodetection of the CRIS version fails.
21058 @item show cris-version
21059 Show the current CRIS version.
21061 @item set cris-dwarf2-cfi
21062 @cindex DWARF-2 CFI and CRIS
21063 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
21064 Change to @samp{off} when using @code{gcc-cris} whose version is below
21067 @item show cris-dwarf2-cfi
21068 Show the current state of using DWARF-2 CFI.
21070 @item set cris-mode @var{mode}
21072 Set the current CRIS mode to @var{mode}. It should only be changed when
21073 debugging in guru mode, in which case it should be set to
21074 @samp{guru} (the default is @samp{normal}).
21076 @item show cris-mode
21077 Show the current CRIS mode.
21081 @subsection Renesas Super-H
21084 For the Renesas Super-H processor, @value{GDBN} provides these
21088 @item set sh calling-convention @var{convention}
21089 @kindex set sh calling-convention
21090 Set the calling-convention used when calling functions from @value{GDBN}.
21091 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21092 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21093 convention. If the DWARF-2 information of the called function specifies
21094 that the function follows the Renesas calling convention, the function
21095 is called using the Renesas calling convention. If the calling convention
21096 is set to @samp{renesas}, the Renesas calling convention is always used,
21097 regardless of the DWARF-2 information. This can be used to override the
21098 default of @samp{gcc} if debug information is missing, or the compiler
21099 does not emit the DWARF-2 calling convention entry for a function.
21101 @item show sh calling-convention
21102 @kindex show sh calling-convention
21103 Show the current calling convention setting.
21108 @node Architectures
21109 @section Architectures
21111 This section describes characteristics of architectures that affect
21112 all uses of @value{GDBN} with the architecture, both native and cross.
21119 * HPPA:: HP PA architecture
21120 * SPU:: Cell Broadband Engine SPU architecture
21126 @subsection AArch64
21127 @cindex AArch64 support
21129 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21130 following special commands:
21133 @item set debug aarch64
21134 @kindex set debug aarch64
21135 This command determines whether AArch64 architecture-specific debugging
21136 messages are to be displayed.
21138 @item show debug aarch64
21139 Show whether AArch64 debugging messages are displayed.
21144 @subsection x86 Architecture-specific Issues
21147 @item set struct-convention @var{mode}
21148 @kindex set struct-convention
21149 @cindex struct return convention
21150 @cindex struct/union returned in registers
21151 Set the convention used by the inferior to return @code{struct}s and
21152 @code{union}s from functions to @var{mode}. Possible values of
21153 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21154 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21155 are returned on the stack, while @code{"reg"} means that a
21156 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21157 be returned in a register.
21159 @item show struct-convention
21160 @kindex show struct-convention
21161 Show the current setting of the convention to return @code{struct}s
21168 See the following section.
21171 @subsection @acronym{MIPS}
21173 @cindex stack on Alpha
21174 @cindex stack on @acronym{MIPS}
21175 @cindex Alpha stack
21176 @cindex @acronym{MIPS} stack
21177 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21178 sometimes requires @value{GDBN} to search backward in the object code to
21179 find the beginning of a function.
21181 @cindex response time, @acronym{MIPS} debugging
21182 To improve response time (especially for embedded applications, where
21183 @value{GDBN} may be restricted to a slow serial line for this search)
21184 you may want to limit the size of this search, using one of these
21188 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21189 @item set heuristic-fence-post @var{limit}
21190 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21191 search for the beginning of a function. A value of @var{0} (the
21192 default) means there is no limit. However, except for @var{0}, the
21193 larger the limit the more bytes @code{heuristic-fence-post} must search
21194 and therefore the longer it takes to run. You should only need to use
21195 this command when debugging a stripped executable.
21197 @item show heuristic-fence-post
21198 Display the current limit.
21202 These commands are available @emph{only} when @value{GDBN} is configured
21203 for debugging programs on Alpha or @acronym{MIPS} processors.
21205 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21209 @item set mips abi @var{arg}
21210 @kindex set mips abi
21211 @cindex set ABI for @acronym{MIPS}
21212 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21213 values of @var{arg} are:
21217 The default ABI associated with the current binary (this is the
21227 @item show mips abi
21228 @kindex show mips abi
21229 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21231 @item set mips compression @var{arg}
21232 @kindex set mips compression
21233 @cindex code compression, @acronym{MIPS}
21234 Tell @value{GDBN} which @acronym{MIPS} compressed
21235 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21236 inferior. @value{GDBN} uses this for code disassembly and other
21237 internal interpretation purposes. This setting is only referred to
21238 when no executable has been associated with the debugging session or
21239 the executable does not provide information about the encoding it uses.
21240 Otherwise this setting is automatically updated from information
21241 provided by the executable.
21243 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21244 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21245 executables containing @acronym{MIPS16} code frequently are not
21246 identified as such.
21248 This setting is ``sticky''; that is, it retains its value across
21249 debugging sessions until reset either explicitly with this command or
21250 implicitly from an executable.
21252 The compiler and/or assembler typically add symbol table annotations to
21253 identify functions compiled for the @acronym{MIPS16} or
21254 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21255 are present, @value{GDBN} uses them in preference to the global
21256 compressed @acronym{ISA} encoding setting.
21258 @item show mips compression
21259 @kindex show mips compression
21260 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21261 @value{GDBN} to debug the inferior.
21264 @itemx show mipsfpu
21265 @xref{MIPS Embedded, set mipsfpu}.
21267 @item set mips mask-address @var{arg}
21268 @kindex set mips mask-address
21269 @cindex @acronym{MIPS} addresses, masking
21270 This command determines whether the most-significant 32 bits of 64-bit
21271 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21272 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21273 setting, which lets @value{GDBN} determine the correct value.
21275 @item show mips mask-address
21276 @kindex show mips mask-address
21277 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21280 @item set remote-mips64-transfers-32bit-regs
21281 @kindex set remote-mips64-transfers-32bit-regs
21282 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21283 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21284 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21285 and 64 bits for other registers, set this option to @samp{on}.
21287 @item show remote-mips64-transfers-32bit-regs
21288 @kindex show remote-mips64-transfers-32bit-regs
21289 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21291 @item set debug mips
21292 @kindex set debug mips
21293 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21294 target code in @value{GDBN}.
21296 @item show debug mips
21297 @kindex show debug mips
21298 Show the current setting of @acronym{MIPS} debugging messages.
21304 @cindex HPPA support
21306 When @value{GDBN} is debugging the HP PA architecture, it provides the
21307 following special commands:
21310 @item set debug hppa
21311 @kindex set debug hppa
21312 This command determines whether HPPA architecture-specific debugging
21313 messages are to be displayed.
21315 @item show debug hppa
21316 Show whether HPPA debugging messages are displayed.
21318 @item maint print unwind @var{address}
21319 @kindex maint print unwind@r{, HPPA}
21320 This command displays the contents of the unwind table entry at the
21321 given @var{address}.
21327 @subsection Cell Broadband Engine SPU architecture
21328 @cindex Cell Broadband Engine
21331 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21332 it provides the following special commands:
21335 @item info spu event
21337 Display SPU event facility status. Shows current event mask
21338 and pending event status.
21340 @item info spu signal
21341 Display SPU signal notification facility status. Shows pending
21342 signal-control word and signal notification mode of both signal
21343 notification channels.
21345 @item info spu mailbox
21346 Display SPU mailbox facility status. Shows all pending entries,
21347 in order of processing, in each of the SPU Write Outbound,
21348 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21351 Display MFC DMA status. Shows all pending commands in the MFC
21352 DMA queue. For each entry, opcode, tag, class IDs, effective
21353 and local store addresses and transfer size are shown.
21355 @item info spu proxydma
21356 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21357 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21358 and local store addresses and transfer size are shown.
21362 When @value{GDBN} is debugging a combined PowerPC/SPU application
21363 on the Cell Broadband Engine, it provides in addition the following
21367 @item set spu stop-on-load @var{arg}
21369 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21370 will give control to the user when a new SPE thread enters its @code{main}
21371 function. The default is @code{off}.
21373 @item show spu stop-on-load
21375 Show whether to stop for new SPE threads.
21377 @item set spu auto-flush-cache @var{arg}
21378 Set whether to automatically flush the software-managed cache. When set to
21379 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21380 cache to be flushed whenever SPE execution stops. This provides a consistent
21381 view of PowerPC memory that is accessed via the cache. If an application
21382 does not use the software-managed cache, this option has no effect.
21384 @item show spu auto-flush-cache
21385 Show whether to automatically flush the software-managed cache.
21390 @subsection PowerPC
21391 @cindex PowerPC architecture
21393 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21394 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21395 numbers stored in the floating point registers. These values must be stored
21396 in two consecutive registers, always starting at an even register like
21397 @code{f0} or @code{f2}.
21399 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21400 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21401 @code{f2} and @code{f3} for @code{$dl1} and so on.
21403 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21404 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21407 @subsection Nios II
21408 @cindex Nios II architecture
21410 When @value{GDBN} is debugging the Nios II architecture,
21411 it provides the following special commands:
21415 @item set debug nios2
21416 @kindex set debug nios2
21417 This command turns on and off debugging messages for the Nios II
21418 target code in @value{GDBN}.
21420 @item show debug nios2
21421 @kindex show debug nios2
21422 Show the current setting of Nios II debugging messages.
21425 @node Controlling GDB
21426 @chapter Controlling @value{GDBN}
21428 You can alter the way @value{GDBN} interacts with you by using the
21429 @code{set} command. For commands controlling how @value{GDBN} displays
21430 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21435 * Editing:: Command editing
21436 * Command History:: Command history
21437 * Screen Size:: Screen size
21438 * Numbers:: Numbers
21439 * ABI:: Configuring the current ABI
21440 * Auto-loading:: Automatically loading associated files
21441 * Messages/Warnings:: Optional warnings and messages
21442 * Debugging Output:: Optional messages about internal happenings
21443 * Other Misc Settings:: Other Miscellaneous Settings
21451 @value{GDBN} indicates its readiness to read a command by printing a string
21452 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21453 can change the prompt string with the @code{set prompt} command. For
21454 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21455 the prompt in one of the @value{GDBN} sessions so that you can always tell
21456 which one you are talking to.
21458 @emph{Note:} @code{set prompt} does not add a space for you after the
21459 prompt you set. This allows you to set a prompt which ends in a space
21460 or a prompt that does not.
21464 @item set prompt @var{newprompt}
21465 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21467 @kindex show prompt
21469 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21472 Versions of @value{GDBN} that ship with Python scripting enabled have
21473 prompt extensions. The commands for interacting with these extensions
21477 @kindex set extended-prompt
21478 @item set extended-prompt @var{prompt}
21479 Set an extended prompt that allows for substitutions.
21480 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21481 substitution. Any escape sequences specified as part of the prompt
21482 string are replaced with the corresponding strings each time the prompt
21488 set extended-prompt Current working directory: \w (gdb)
21491 Note that when an extended-prompt is set, it takes control of the
21492 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21494 @kindex show extended-prompt
21495 @item show extended-prompt
21496 Prints the extended prompt. Any escape sequences specified as part of
21497 the prompt string with @code{set extended-prompt}, are replaced with the
21498 corresponding strings each time the prompt is displayed.
21502 @section Command Editing
21504 @cindex command line editing
21506 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21507 @sc{gnu} library provides consistent behavior for programs which provide a
21508 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21509 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21510 substitution, and a storage and recall of command history across
21511 debugging sessions.
21513 You may control the behavior of command line editing in @value{GDBN} with the
21514 command @code{set}.
21517 @kindex set editing
21520 @itemx set editing on
21521 Enable command line editing (enabled by default).
21523 @item set editing off
21524 Disable command line editing.
21526 @kindex show editing
21528 Show whether command line editing is enabled.
21531 @ifset SYSTEM_READLINE
21532 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21534 @ifclear SYSTEM_READLINE
21535 @xref{Command Line Editing},
21537 for more details about the Readline
21538 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21539 encouraged to read that chapter.
21541 @node Command History
21542 @section Command History
21543 @cindex command history
21545 @value{GDBN} can keep track of the commands you type during your
21546 debugging sessions, so that you can be certain of precisely what
21547 happened. Use these commands to manage the @value{GDBN} command
21550 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21551 package, to provide the history facility.
21552 @ifset SYSTEM_READLINE
21553 @xref{Using History Interactively, , , history, GNU History Library},
21555 @ifclear SYSTEM_READLINE
21556 @xref{Using History Interactively},
21558 for the detailed description of the History library.
21560 To issue a command to @value{GDBN} without affecting certain aspects of
21561 the state which is seen by users, prefix it with @samp{server }
21562 (@pxref{Server Prefix}). This
21563 means that this command will not affect the command history, nor will it
21564 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21565 pressed on a line by itself.
21567 @cindex @code{server}, command prefix
21568 The server prefix does not affect the recording of values into the value
21569 history; to print a value without recording it into the value history,
21570 use the @code{output} command instead of the @code{print} command.
21572 Here is the description of @value{GDBN} commands related to command
21576 @cindex history substitution
21577 @cindex history file
21578 @kindex set history filename
21579 @cindex @env{GDBHISTFILE}, environment variable
21580 @item set history filename @var{fname}
21581 Set the name of the @value{GDBN} command history file to @var{fname}.
21582 This is the file where @value{GDBN} reads an initial command history
21583 list, and where it writes the command history from this session when it
21584 exits. You can access this list through history expansion or through
21585 the history command editing characters listed below. This file defaults
21586 to the value of the environment variable @code{GDBHISTFILE}, or to
21587 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21590 @cindex save command history
21591 @kindex set history save
21592 @item set history save
21593 @itemx set history save on
21594 Record command history in a file, whose name may be specified with the
21595 @code{set history filename} command. By default, this option is disabled.
21597 @item set history save off
21598 Stop recording command history in a file.
21600 @cindex history size
21601 @kindex set history size
21602 @cindex @env{HISTSIZE}, environment variable
21603 @item set history size @var{size}
21604 @itemx set history size unlimited
21605 Set the number of commands which @value{GDBN} keeps in its history list.
21606 This defaults to the value of the environment variable
21607 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21608 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21609 history list is unlimited.
21612 History expansion assigns special meaning to the character @kbd{!}.
21613 @ifset SYSTEM_READLINE
21614 @xref{Event Designators, , , history, GNU History Library},
21616 @ifclear SYSTEM_READLINE
21617 @xref{Event Designators},
21621 @cindex history expansion, turn on/off
21622 Since @kbd{!} is also the logical not operator in C, history expansion
21623 is off by default. If you decide to enable history expansion with the
21624 @code{set history expansion on} command, you may sometimes need to
21625 follow @kbd{!} (when it is used as logical not, in an expression) with
21626 a space or a tab to prevent it from being expanded. The readline
21627 history facilities do not attempt substitution on the strings
21628 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21630 The commands to control history expansion are:
21633 @item set history expansion on
21634 @itemx set history expansion
21635 @kindex set history expansion
21636 Enable history expansion. History expansion is off by default.
21638 @item set history expansion off
21639 Disable history expansion.
21642 @kindex show history
21644 @itemx show history filename
21645 @itemx show history save
21646 @itemx show history size
21647 @itemx show history expansion
21648 These commands display the state of the @value{GDBN} history parameters.
21649 @code{show history} by itself displays all four states.
21654 @kindex show commands
21655 @cindex show last commands
21656 @cindex display command history
21657 @item show commands
21658 Display the last ten commands in the command history.
21660 @item show commands @var{n}
21661 Print ten commands centered on command number @var{n}.
21663 @item show commands +
21664 Print ten commands just after the commands last printed.
21668 @section Screen Size
21669 @cindex size of screen
21670 @cindex pauses in output
21672 Certain commands to @value{GDBN} may produce large amounts of
21673 information output to the screen. To help you read all of it,
21674 @value{GDBN} pauses and asks you for input at the end of each page of
21675 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21676 to discard the remaining output. Also, the screen width setting
21677 determines when to wrap lines of output. Depending on what is being
21678 printed, @value{GDBN} tries to break the line at a readable place,
21679 rather than simply letting it overflow onto the following line.
21681 Normally @value{GDBN} knows the size of the screen from the terminal
21682 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21683 together with the value of the @code{TERM} environment variable and the
21684 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21685 you can override it with the @code{set height} and @code{set
21692 @kindex show height
21693 @item set height @var{lpp}
21694 @itemx set height unlimited
21696 @itemx set width @var{cpl}
21697 @itemx set width unlimited
21699 These @code{set} commands specify a screen height of @var{lpp} lines and
21700 a screen width of @var{cpl} characters. The associated @code{show}
21701 commands display the current settings.
21703 If you specify a height of either @code{unlimited} or zero lines,
21704 @value{GDBN} does not pause during output no matter how long the
21705 output is. This is useful if output is to a file or to an editor
21708 Likewise, you can specify @samp{set width unlimited} or @samp{set
21709 width 0} to prevent @value{GDBN} from wrapping its output.
21711 @item set pagination on
21712 @itemx set pagination off
21713 @kindex set pagination
21714 Turn the output pagination on or off; the default is on. Turning
21715 pagination off is the alternative to @code{set height unlimited}. Note that
21716 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21717 Options, -batch}) also automatically disables pagination.
21719 @item show pagination
21720 @kindex show pagination
21721 Show the current pagination mode.
21726 @cindex number representation
21727 @cindex entering numbers
21729 You can always enter numbers in octal, decimal, or hexadecimal in
21730 @value{GDBN} by the usual conventions: octal numbers begin with
21731 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21732 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21733 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21734 10; likewise, the default display for numbers---when no particular
21735 format is specified---is base 10. You can change the default base for
21736 both input and output with the commands described below.
21739 @kindex set input-radix
21740 @item set input-radix @var{base}
21741 Set the default base for numeric input. Supported choices
21742 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21743 specified either unambiguously or using the current input radix; for
21747 set input-radix 012
21748 set input-radix 10.
21749 set input-radix 0xa
21753 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21754 leaves the input radix unchanged, no matter what it was, since
21755 @samp{10}, being without any leading or trailing signs of its base, is
21756 interpreted in the current radix. Thus, if the current radix is 16,
21757 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21760 @kindex set output-radix
21761 @item set output-radix @var{base}
21762 Set the default base for numeric display. Supported choices
21763 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21764 specified either unambiguously or using the current input radix.
21766 @kindex show input-radix
21767 @item show input-radix
21768 Display the current default base for numeric input.
21770 @kindex show output-radix
21771 @item show output-radix
21772 Display the current default base for numeric display.
21774 @item set radix @r{[}@var{base}@r{]}
21778 These commands set and show the default base for both input and output
21779 of numbers. @code{set radix} sets the radix of input and output to
21780 the same base; without an argument, it resets the radix back to its
21781 default value of 10.
21786 @section Configuring the Current ABI
21788 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21789 application automatically. However, sometimes you need to override its
21790 conclusions. Use these commands to manage @value{GDBN}'s view of the
21796 @cindex Newlib OS ABI and its influence on the longjmp handling
21798 One @value{GDBN} configuration can debug binaries for multiple operating
21799 system targets, either via remote debugging or native emulation.
21800 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21801 but you can override its conclusion using the @code{set osabi} command.
21802 One example where this is useful is in debugging of binaries which use
21803 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21804 not have the same identifying marks that the standard C library for your
21807 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21808 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21809 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21810 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21814 Show the OS ABI currently in use.
21817 With no argument, show the list of registered available OS ABI's.
21819 @item set osabi @var{abi}
21820 Set the current OS ABI to @var{abi}.
21823 @cindex float promotion
21825 Generally, the way that an argument of type @code{float} is passed to a
21826 function depends on whether the function is prototyped. For a prototyped
21827 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21828 according to the architecture's convention for @code{float}. For unprototyped
21829 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21830 @code{double} and then passed.
21832 Unfortunately, some forms of debug information do not reliably indicate whether
21833 a function is prototyped. If @value{GDBN} calls a function that is not marked
21834 as prototyped, it consults @kbd{set coerce-float-to-double}.
21837 @kindex set coerce-float-to-double
21838 @item set coerce-float-to-double
21839 @itemx set coerce-float-to-double on
21840 Arguments of type @code{float} will be promoted to @code{double} when passed
21841 to an unprototyped function. This is the default setting.
21843 @item set coerce-float-to-double off
21844 Arguments of type @code{float} will be passed directly to unprototyped
21847 @kindex show coerce-float-to-double
21848 @item show coerce-float-to-double
21849 Show the current setting of promoting @code{float} to @code{double}.
21853 @kindex show cp-abi
21854 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21855 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21856 used to build your application. @value{GDBN} only fully supports
21857 programs with a single C@t{++} ABI; if your program contains code using
21858 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21859 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21860 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21861 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21862 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21863 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21868 Show the C@t{++} ABI currently in use.
21871 With no argument, show the list of supported C@t{++} ABI's.
21873 @item set cp-abi @var{abi}
21874 @itemx set cp-abi auto
21875 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21879 @section Automatically loading associated files
21880 @cindex auto-loading
21882 @value{GDBN} sometimes reads files with commands and settings automatically,
21883 without being explicitly told so by the user. We call this feature
21884 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21885 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21886 results or introduce security risks (e.g., if the file comes from untrusted
21889 Note that loading of these associated files (including the local @file{.gdbinit}
21890 file) requires accordingly configured @code{auto-load safe-path}
21891 (@pxref{Auto-loading safe path}).
21893 For these reasons, @value{GDBN} includes commands and options to let you
21894 control when to auto-load files and which files should be auto-loaded.
21897 @anchor{set auto-load off}
21898 @kindex set auto-load off
21899 @item set auto-load off
21900 Globally disable loading of all auto-loaded files.
21901 You may want to use this command with the @samp{-iex} option
21902 (@pxref{Option -init-eval-command}) such as:
21904 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21907 Be aware that system init file (@pxref{System-wide configuration})
21908 and init files from your home directory (@pxref{Home Directory Init File})
21909 still get read (as they come from generally trusted directories).
21910 To prevent @value{GDBN} from auto-loading even those init files, use the
21911 @option{-nx} option (@pxref{Mode Options}), in addition to
21912 @code{set auto-load no}.
21914 @anchor{show auto-load}
21915 @kindex show auto-load
21916 @item show auto-load
21917 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21921 (gdb) show auto-load
21922 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21923 libthread-db: Auto-loading of inferior specific libthread_db is on.
21924 local-gdbinit: Auto-loading of .gdbinit script from current directory
21926 python-scripts: Auto-loading of Python scripts is on.
21927 safe-path: List of directories from which it is safe to auto-load files
21928 is $debugdir:$datadir/auto-load.
21929 scripts-directory: List of directories from which to load auto-loaded scripts
21930 is $debugdir:$datadir/auto-load.
21933 @anchor{info auto-load}
21934 @kindex info auto-load
21935 @item info auto-load
21936 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21940 (gdb) info auto-load
21943 Yes /home/user/gdb/gdb-gdb.gdb
21944 libthread-db: No auto-loaded libthread-db.
21945 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21949 Yes /home/user/gdb/gdb-gdb.py
21953 These are various kinds of files @value{GDBN} can automatically load:
21957 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21959 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21961 @xref{dotdebug_gdb_scripts section},
21962 controlled by @ref{set auto-load python-scripts}.
21964 @xref{Init File in the Current Directory},
21965 controlled by @ref{set auto-load local-gdbinit}.
21967 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21970 These are @value{GDBN} control commands for the auto-loading:
21972 @multitable @columnfractions .5 .5
21973 @item @xref{set auto-load off}.
21974 @tab Disable auto-loading globally.
21975 @item @xref{show auto-load}.
21976 @tab Show setting of all kinds of files.
21977 @item @xref{info auto-load}.
21978 @tab Show state of all kinds of files.
21979 @item @xref{set auto-load gdb-scripts}.
21980 @tab Control for @value{GDBN} command scripts.
21981 @item @xref{show auto-load gdb-scripts}.
21982 @tab Show setting of @value{GDBN} command scripts.
21983 @item @xref{info auto-load gdb-scripts}.
21984 @tab Show state of @value{GDBN} command scripts.
21985 @item @xref{set auto-load python-scripts}.
21986 @tab Control for @value{GDBN} Python scripts.
21987 @item @xref{show auto-load python-scripts}.
21988 @tab Show setting of @value{GDBN} Python scripts.
21989 @item @xref{info auto-load python-scripts}.
21990 @tab Show state of @value{GDBN} Python scripts.
21991 @item @xref{set auto-load scripts-directory}.
21992 @tab Control for @value{GDBN} auto-loaded scripts location.
21993 @item @xref{show auto-load scripts-directory}.
21994 @tab Show @value{GDBN} auto-loaded scripts location.
21995 @item @xref{set auto-load local-gdbinit}.
21996 @tab Control for init file in the current directory.
21997 @item @xref{show auto-load local-gdbinit}.
21998 @tab Show setting of init file in the current directory.
21999 @item @xref{info auto-load local-gdbinit}.
22000 @tab Show state of init file in the current directory.
22001 @item @xref{set auto-load libthread-db}.
22002 @tab Control for thread debugging library.
22003 @item @xref{show auto-load libthread-db}.
22004 @tab Show setting of thread debugging library.
22005 @item @xref{info auto-load libthread-db}.
22006 @tab Show state of thread debugging library.
22007 @item @xref{set auto-load safe-path}.
22008 @tab Control directories trusted for automatic loading.
22009 @item @xref{show auto-load safe-path}.
22010 @tab Show directories trusted for automatic loading.
22011 @item @xref{add-auto-load-safe-path}.
22012 @tab Add directory trusted for automatic loading.
22016 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
22017 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
22018 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
22019 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
22020 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
22021 @xref{Python Auto-loading}.
22024 @node Init File in the Current Directory
22025 @subsection Automatically loading init file in the current directory
22026 @cindex auto-loading init file in the current directory
22028 By default, @value{GDBN} reads and executes the canned sequences of commands
22029 from init file (if any) in the current working directory,
22030 see @ref{Init File in the Current Directory during Startup}.
22032 Note that loading of this local @file{.gdbinit} file also requires accordingly
22033 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22036 @anchor{set auto-load local-gdbinit}
22037 @kindex set auto-load local-gdbinit
22038 @item set auto-load local-gdbinit [on|off]
22039 Enable or disable the auto-loading of canned sequences of commands
22040 (@pxref{Sequences}) found in init file in the current directory.
22042 @anchor{show auto-load local-gdbinit}
22043 @kindex show auto-load local-gdbinit
22044 @item show auto-load local-gdbinit
22045 Show whether auto-loading of canned sequences of commands from init file in the
22046 current directory is enabled or disabled.
22048 @anchor{info auto-load local-gdbinit}
22049 @kindex info auto-load local-gdbinit
22050 @item info auto-load local-gdbinit
22051 Print whether canned sequences of commands from init file in the
22052 current directory have been auto-loaded.
22055 @node libthread_db.so.1 file
22056 @subsection Automatically loading thread debugging library
22057 @cindex auto-loading libthread_db.so.1
22059 This feature is currently present only on @sc{gnu}/Linux native hosts.
22061 @value{GDBN} reads in some cases thread debugging library from places specific
22062 to the inferior (@pxref{set libthread-db-search-path}).
22064 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
22065 without checking this @samp{set auto-load libthread-db} switch as system
22066 libraries have to be trusted in general. In all other cases of
22067 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
22068 auto-load libthread-db} is enabled before trying to open such thread debugging
22071 Note that loading of this debugging library also requires accordingly configured
22072 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22075 @anchor{set auto-load libthread-db}
22076 @kindex set auto-load libthread-db
22077 @item set auto-load libthread-db [on|off]
22078 Enable or disable the auto-loading of inferior specific thread debugging library.
22080 @anchor{show auto-load libthread-db}
22081 @kindex show auto-load libthread-db
22082 @item show auto-load libthread-db
22083 Show whether auto-loading of inferior specific thread debugging library is
22084 enabled or disabled.
22086 @anchor{info auto-load libthread-db}
22087 @kindex info auto-load libthread-db
22088 @item info auto-load libthread-db
22089 Print the list of all loaded inferior specific thread debugging libraries and
22090 for each such library print list of inferior @var{pid}s using it.
22093 @node objfile-gdb.gdb file
22094 @subsection The @file{@var{objfile}-gdb.gdb} file
22095 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
22097 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
22098 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
22099 auto-load gdb-scripts} is set to @samp{on}.
22101 Note that loading of this script file also requires accordingly configured
22102 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22104 For more background refer to the similar Python scripts auto-loading
22105 description (@pxref{objfile-gdb.py file}).
22108 @anchor{set auto-load gdb-scripts}
22109 @kindex set auto-load gdb-scripts
22110 @item set auto-load gdb-scripts [on|off]
22111 Enable or disable the auto-loading of canned sequences of commands scripts.
22113 @anchor{show auto-load gdb-scripts}
22114 @kindex show auto-load gdb-scripts
22115 @item show auto-load gdb-scripts
22116 Show whether auto-loading of canned sequences of commands scripts is enabled or
22119 @anchor{info auto-load gdb-scripts}
22120 @kindex info auto-load gdb-scripts
22121 @cindex print list of auto-loaded canned sequences of commands scripts
22122 @item info auto-load gdb-scripts [@var{regexp}]
22123 Print the list of all canned sequences of commands scripts that @value{GDBN}
22127 If @var{regexp} is supplied only canned sequences of commands scripts with
22128 matching names are printed.
22130 @node Auto-loading safe path
22131 @subsection Security restriction for auto-loading
22132 @cindex auto-loading safe-path
22134 As the files of inferior can come from untrusted source (such as submitted by
22135 an application user) @value{GDBN} does not always load any files automatically.
22136 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22137 directories trusted for loading files not explicitly requested by user.
22138 Each directory can also be a shell wildcard pattern.
22140 If the path is not set properly you will see a warning and the file will not
22145 Reading symbols from /home/user/gdb/gdb...done.
22146 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22147 declined by your `auto-load safe-path' set
22148 to "$debugdir:$datadir/auto-load".
22149 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22150 declined by your `auto-load safe-path' set
22151 to "$debugdir:$datadir/auto-load".
22155 To instruct @value{GDBN} to go ahead and use the init files anyway,
22156 invoke @value{GDBN} like this:
22159 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22162 The list of trusted directories is controlled by the following commands:
22165 @anchor{set auto-load safe-path}
22166 @kindex set auto-load safe-path
22167 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22168 Set the list of directories (and their subdirectories) trusted for automatic
22169 loading and execution of scripts. You can also enter a specific trusted file.
22170 Each directory can also be a shell wildcard pattern; wildcards do not match
22171 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22172 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22173 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22174 its default value as specified during @value{GDBN} compilation.
22176 The list of directories uses path separator (@samp{:} on GNU and Unix
22177 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22178 to the @env{PATH} environment variable.
22180 @anchor{show auto-load safe-path}
22181 @kindex show auto-load safe-path
22182 @item show auto-load safe-path
22183 Show the list of directories trusted for automatic loading and execution of
22186 @anchor{add-auto-load-safe-path}
22187 @kindex add-auto-load-safe-path
22188 @item add-auto-load-safe-path
22189 Add an entry (or list of entries) the list of directories trusted for automatic
22190 loading and execution of scripts. Multiple entries may be delimited by the
22191 host platform path separator in use.
22194 This variable defaults to what @code{--with-auto-load-dir} has been configured
22195 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22196 substitution applies the same as for @ref{set auto-load scripts-directory}.
22197 The default @code{set auto-load safe-path} value can be also overriden by
22198 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22200 Setting this variable to @file{/} disables this security protection,
22201 corresponding @value{GDBN} configuration option is
22202 @option{--without-auto-load-safe-path}.
22203 This variable is supposed to be set to the system directories writable by the
22204 system superuser only. Users can add their source directories in init files in
22205 their home directories (@pxref{Home Directory Init File}). See also deprecated
22206 init file in the current directory
22207 (@pxref{Init File in the Current Directory during Startup}).
22209 To force @value{GDBN} to load the files it declined to load in the previous
22210 example, you could use one of the following ways:
22213 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22214 Specify this trusted directory (or a file) as additional component of the list.
22215 You have to specify also any existing directories displayed by
22216 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22218 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22219 Specify this directory as in the previous case but just for a single
22220 @value{GDBN} session.
22222 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22223 Disable auto-loading safety for a single @value{GDBN} session.
22224 This assumes all the files you debug during this @value{GDBN} session will come
22225 from trusted sources.
22227 @item @kbd{./configure --without-auto-load-safe-path}
22228 During compilation of @value{GDBN} you may disable any auto-loading safety.
22229 This assumes all the files you will ever debug with this @value{GDBN} come from
22233 On the other hand you can also explicitly forbid automatic files loading which
22234 also suppresses any such warning messages:
22237 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22238 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22240 @item @file{~/.gdbinit}: @samp{set auto-load no}
22241 Disable auto-loading globally for the user
22242 (@pxref{Home Directory Init File}). While it is improbable, you could also
22243 use system init file instead (@pxref{System-wide configuration}).
22246 This setting applies to the file names as entered by user. If no entry matches
22247 @value{GDBN} tries as a last resort to also resolve all the file names into
22248 their canonical form (typically resolving symbolic links) and compare the
22249 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22250 own before starting the comparison so a canonical form of directories is
22251 recommended to be entered.
22253 @node Auto-loading verbose mode
22254 @subsection Displaying files tried for auto-load
22255 @cindex auto-loading verbose mode
22257 For better visibility of all the file locations where you can place scripts to
22258 be auto-loaded with inferior --- or to protect yourself against accidental
22259 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22260 all the files attempted to be loaded. Both existing and non-existing files may
22263 For example the list of directories from which it is safe to auto-load files
22264 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22265 may not be too obvious while setting it up.
22268 (gdb) set debug auto-load on
22269 (gdb) file ~/src/t/true
22270 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22271 for objfile "/tmp/true".
22272 auto-load: Updating directories of "/usr:/opt".
22273 auto-load: Using directory "/usr".
22274 auto-load: Using directory "/opt".
22275 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22276 by your `auto-load safe-path' set to "/usr:/opt".
22280 @anchor{set debug auto-load}
22281 @kindex set debug auto-load
22282 @item set debug auto-load [on|off]
22283 Set whether to print the filenames attempted to be auto-loaded.
22285 @anchor{show debug auto-load}
22286 @kindex show debug auto-load
22287 @item show debug auto-load
22288 Show whether printing of the filenames attempted to be auto-loaded is turned
22292 @node Messages/Warnings
22293 @section Optional Warnings and Messages
22295 @cindex verbose operation
22296 @cindex optional warnings
22297 By default, @value{GDBN} is silent about its inner workings. If you are
22298 running on a slow machine, you may want to use the @code{set verbose}
22299 command. This makes @value{GDBN} tell you when it does a lengthy
22300 internal operation, so you will not think it has crashed.
22302 Currently, the messages controlled by @code{set verbose} are those
22303 which announce that the symbol table for a source file is being read;
22304 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22307 @kindex set verbose
22308 @item set verbose on
22309 Enables @value{GDBN} output of certain informational messages.
22311 @item set verbose off
22312 Disables @value{GDBN} output of certain informational messages.
22314 @kindex show verbose
22316 Displays whether @code{set verbose} is on or off.
22319 By default, if @value{GDBN} encounters bugs in the symbol table of an
22320 object file, it is silent; but if you are debugging a compiler, you may
22321 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22326 @kindex set complaints
22327 @item set complaints @var{limit}
22328 Permits @value{GDBN} to output @var{limit} complaints about each type of
22329 unusual symbols before becoming silent about the problem. Set
22330 @var{limit} to zero to suppress all complaints; set it to a large number
22331 to prevent complaints from being suppressed.
22333 @kindex show complaints
22334 @item show complaints
22335 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22339 @anchor{confirmation requests}
22340 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22341 lot of stupid questions to confirm certain commands. For example, if
22342 you try to run a program which is already running:
22346 The program being debugged has been started already.
22347 Start it from the beginning? (y or n)
22350 If you are willing to unflinchingly face the consequences of your own
22351 commands, you can disable this ``feature'':
22355 @kindex set confirm
22357 @cindex confirmation
22358 @cindex stupid questions
22359 @item set confirm off
22360 Disables confirmation requests. Note that running @value{GDBN} with
22361 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22362 automatically disables confirmation requests.
22364 @item set confirm on
22365 Enables confirmation requests (the default).
22367 @kindex show confirm
22369 Displays state of confirmation requests.
22373 @cindex command tracing
22374 If you need to debug user-defined commands or sourced files you may find it
22375 useful to enable @dfn{command tracing}. In this mode each command will be
22376 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22377 quantity denoting the call depth of each command.
22380 @kindex set trace-commands
22381 @cindex command scripts, debugging
22382 @item set trace-commands on
22383 Enable command tracing.
22384 @item set trace-commands off
22385 Disable command tracing.
22386 @item show trace-commands
22387 Display the current state of command tracing.
22390 @node Debugging Output
22391 @section Optional Messages about Internal Happenings
22392 @cindex optional debugging messages
22394 @value{GDBN} has commands that enable optional debugging messages from
22395 various @value{GDBN} subsystems; normally these commands are of
22396 interest to @value{GDBN} maintainers, or when reporting a bug. This
22397 section documents those commands.
22400 @kindex set exec-done-display
22401 @item set exec-done-display
22402 Turns on or off the notification of asynchronous commands'
22403 completion. When on, @value{GDBN} will print a message when an
22404 asynchronous command finishes its execution. The default is off.
22405 @kindex show exec-done-display
22406 @item show exec-done-display
22407 Displays the current setting of asynchronous command completion
22410 @cindex ARM AArch64
22411 @item set debug aarch64
22412 Turns on or off display of debugging messages related to ARM AArch64.
22413 The default is off.
22415 @item show debug aarch64
22416 Displays the current state of displaying debugging messages related to
22418 @cindex gdbarch debugging info
22419 @cindex architecture debugging info
22420 @item set debug arch
22421 Turns on or off display of gdbarch debugging info. The default is off
22422 @item show debug arch
22423 Displays the current state of displaying gdbarch debugging info.
22424 @item set debug aix-solib
22425 @cindex AIX shared library debugging
22426 Control display of debugging messages from the AIX shared library
22427 support module. The default is off.
22428 @item show debug aix-thread
22429 Show the current state of displaying AIX shared library debugging messages.
22430 @item set debug aix-thread
22431 @cindex AIX threads
22432 Display debugging messages about inner workings of the AIX thread
22434 @item show debug aix-thread
22435 Show the current state of AIX thread debugging info display.
22436 @item set debug check-physname
22438 Check the results of the ``physname'' computation. When reading DWARF
22439 debugging information for C@t{++}, @value{GDBN} attempts to compute
22440 each entity's name. @value{GDBN} can do this computation in two
22441 different ways, depending on exactly what information is present.
22442 When enabled, this setting causes @value{GDBN} to compute the names
22443 both ways and display any discrepancies.
22444 @item show debug check-physname
22445 Show the current state of ``physname'' checking.
22446 @item set debug coff-pe-read
22447 @cindex COFF/PE exported symbols
22448 Control display of debugging messages related to reading of COFF/PE
22449 exported symbols. The default is off.
22450 @item show debug coff-pe-read
22451 Displays the current state of displaying debugging messages related to
22452 reading of COFF/PE exported symbols.
22453 @item set debug dwarf2-die
22454 @cindex DWARF2 DIEs
22455 Dump DWARF2 DIEs after they are read in.
22456 The value is the number of nesting levels to print.
22457 A value of zero turns off the display.
22458 @item show debug dwarf2-die
22459 Show the current state of DWARF2 DIE debugging.
22460 @item set debug dwarf2-read
22461 @cindex DWARF2 Reading
22462 Turns on or off display of debugging messages related to reading
22463 DWARF debug info. The default is off.
22464 @item show debug dwarf2-read
22465 Show the current state of DWARF2 reader debugging.
22466 @item set debug displaced
22467 @cindex displaced stepping debugging info
22468 Turns on or off display of @value{GDBN} debugging info for the
22469 displaced stepping support. The default is off.
22470 @item show debug displaced
22471 Displays the current state of displaying @value{GDBN} debugging info
22472 related to displaced stepping.
22473 @item set debug event
22474 @cindex event debugging info
22475 Turns on or off display of @value{GDBN} event debugging info. The
22477 @item show debug event
22478 Displays the current state of displaying @value{GDBN} event debugging
22480 @item set debug expression
22481 @cindex expression debugging info
22482 Turns on or off display of debugging info about @value{GDBN}
22483 expression parsing. The default is off.
22484 @item show debug expression
22485 Displays the current state of displaying debugging info about
22486 @value{GDBN} expression parsing.
22487 @item set debug frame
22488 @cindex frame debugging info
22489 Turns on or off display of @value{GDBN} frame debugging info. The
22491 @item show debug frame
22492 Displays the current state of displaying @value{GDBN} frame debugging
22494 @item set debug gnu-nat
22495 @cindex @sc{gnu}/Hurd debug messages
22496 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22497 @item show debug gnu-nat
22498 Show the current state of @sc{gnu}/Hurd debugging messages.
22499 @item set debug infrun
22500 @cindex inferior debugging info
22501 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22502 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22503 for implementing operations such as single-stepping the inferior.
22504 @item show debug infrun
22505 Displays the current state of @value{GDBN} inferior debugging.
22506 @item set debug jit
22507 @cindex just-in-time compilation, debugging messages
22508 Turns on or off debugging messages from JIT debug support.
22509 @item show debug jit
22510 Displays the current state of @value{GDBN} JIT debugging.
22511 @item set debug lin-lwp
22512 @cindex @sc{gnu}/Linux LWP debug messages
22513 @cindex Linux lightweight processes
22514 Turns on or off debugging messages from the Linux LWP debug support.
22515 @item show debug lin-lwp
22516 Show the current state of Linux LWP debugging messages.
22517 @item set debug mach-o
22518 @cindex Mach-O symbols processing
22519 Control display of debugging messages related to Mach-O symbols
22520 processing. The default is off.
22521 @item show debug mach-o
22522 Displays the current state of displaying debugging messages related to
22523 reading of COFF/PE exported symbols.
22524 @item set debug notification
22525 @cindex remote async notification debugging info
22526 Turns on or off debugging messages about remote async notification.
22527 The default is off.
22528 @item show debug notification
22529 Displays the current state of remote async notification debugging messages.
22530 @item set debug observer
22531 @cindex observer debugging info
22532 Turns on or off display of @value{GDBN} observer debugging. This
22533 includes info such as the notification of observable events.
22534 @item show debug observer
22535 Displays the current state of observer debugging.
22536 @item set debug overload
22537 @cindex C@t{++} overload debugging info
22538 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22539 info. This includes info such as ranking of functions, etc. The default
22541 @item show debug overload
22542 Displays the current state of displaying @value{GDBN} C@t{++} overload
22544 @cindex expression parser, debugging info
22545 @cindex debug expression parser
22546 @item set debug parser
22547 Turns on or off the display of expression parser debugging output.
22548 Internally, this sets the @code{yydebug} variable in the expression
22549 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22550 details. The default is off.
22551 @item show debug parser
22552 Show the current state of expression parser debugging.
22553 @cindex packets, reporting on stdout
22554 @cindex serial connections, debugging
22555 @cindex debug remote protocol
22556 @cindex remote protocol debugging
22557 @cindex display remote packets
22558 @item set debug remote
22559 Turns on or off display of reports on all packets sent back and forth across
22560 the serial line to the remote machine. The info is printed on the
22561 @value{GDBN} standard output stream. The default is off.
22562 @item show debug remote
22563 Displays the state of display of remote packets.
22564 @item set debug serial
22565 Turns on or off display of @value{GDBN} serial debugging info. The
22567 @item show debug serial
22568 Displays the current state of displaying @value{GDBN} serial debugging
22570 @item set debug solib-frv
22571 @cindex FR-V shared-library debugging
22572 Turns on or off debugging messages for FR-V shared-library code.
22573 @item show debug solib-frv
22574 Display the current state of FR-V shared-library code debugging
22576 @item set debug symfile
22577 @cindex symbol file functions
22578 Turns on or off display of debugging messages related to symbol file functions.
22579 The default is off. @xref{Files}.
22580 @item show debug symfile
22581 Show the current state of symbol file debugging messages.
22582 @item set debug symtab-create
22583 @cindex symbol table creation
22584 Turns on or off display of debugging messages related to symbol table creation.
22585 The default is off.
22586 @item show debug symtab-create
22587 Show the current state of symbol table creation debugging.
22588 @item set debug target
22589 @cindex target debugging info
22590 Turns on or off display of @value{GDBN} target debugging info. This info
22591 includes what is going on at the target level of GDB, as it happens. The
22592 default is 0. Set it to 1 to track events, and to 2 to also track the
22593 value of large memory transfers. Changes to this flag do not take effect
22594 until the next time you connect to a target or use the @code{run} command.
22595 @item show debug target
22596 Displays the current state of displaying @value{GDBN} target debugging
22598 @item set debug timestamp
22599 @cindex timestampping debugging info
22600 Turns on or off display of timestamps with @value{GDBN} debugging info.
22601 When enabled, seconds and microseconds are displayed before each debugging
22603 @item show debug timestamp
22604 Displays the current state of displaying timestamps with @value{GDBN}
22606 @item set debugvarobj
22607 @cindex variable object debugging info
22608 Turns on or off display of @value{GDBN} variable object debugging
22609 info. The default is off.
22610 @item show debugvarobj
22611 Displays the current state of displaying @value{GDBN} variable object
22613 @item set debug xml
22614 @cindex XML parser debugging
22615 Turns on or off debugging messages for built-in XML parsers.
22616 @item show debug xml
22617 Displays the current state of XML debugging messages.
22620 @node Other Misc Settings
22621 @section Other Miscellaneous Settings
22622 @cindex miscellaneous settings
22625 @kindex set interactive-mode
22626 @item set interactive-mode
22627 If @code{on}, forces @value{GDBN} to assume that GDB was started
22628 in a terminal. In practice, this means that @value{GDBN} should wait
22629 for the user to answer queries generated by commands entered at
22630 the command prompt. If @code{off}, forces @value{GDBN} to operate
22631 in the opposite mode, and it uses the default answers to all queries.
22632 If @code{auto} (the default), @value{GDBN} tries to determine whether
22633 its standard input is a terminal, and works in interactive-mode if it
22634 is, non-interactively otherwise.
22636 In the vast majority of cases, the debugger should be able to guess
22637 correctly which mode should be used. But this setting can be useful
22638 in certain specific cases, such as running a MinGW @value{GDBN}
22639 inside a cygwin window.
22641 @kindex show interactive-mode
22642 @item show interactive-mode
22643 Displays whether the debugger is operating in interactive mode or not.
22646 @node Extending GDB
22647 @chapter Extending @value{GDBN}
22648 @cindex extending GDB
22650 @value{GDBN} provides three mechanisms for extension. The first is based
22651 on composition of @value{GDBN} commands, the second is based on the
22652 Python scripting language, and the third is for defining new aliases of
22655 To facilitate the use of the first two extensions, @value{GDBN} is capable
22656 of evaluating the contents of a file. When doing so, @value{GDBN}
22657 can recognize which scripting language is being used by looking at
22658 the filename extension. Files with an unrecognized filename extension
22659 are always treated as a @value{GDBN} Command Files.
22660 @xref{Command Files,, Command files}.
22662 You can control how @value{GDBN} evaluates these files with the following
22666 @kindex set script-extension
22667 @kindex show script-extension
22668 @item set script-extension off
22669 All scripts are always evaluated as @value{GDBN} Command Files.
22671 @item set script-extension soft
22672 The debugger determines the scripting language based on filename
22673 extension. If this scripting language is supported, @value{GDBN}
22674 evaluates the script using that language. Otherwise, it evaluates
22675 the file as a @value{GDBN} Command File.
22677 @item set script-extension strict
22678 The debugger determines the scripting language based on filename
22679 extension, and evaluates the script using that language. If the
22680 language is not supported, then the evaluation fails.
22682 @item show script-extension
22683 Display the current value of the @code{script-extension} option.
22688 * Sequences:: Canned Sequences of Commands
22689 * Python:: Scripting @value{GDBN} using Python
22690 * Aliases:: Creating new spellings of existing commands
22694 @section Canned Sequences of Commands
22696 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22697 Command Lists}), @value{GDBN} provides two ways to store sequences of
22698 commands for execution as a unit: user-defined commands and command
22702 * Define:: How to define your own commands
22703 * Hooks:: Hooks for user-defined commands
22704 * Command Files:: How to write scripts of commands to be stored in a file
22705 * Output:: Commands for controlled output
22709 @subsection User-defined Commands
22711 @cindex user-defined command
22712 @cindex arguments, to user-defined commands
22713 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22714 which you assign a new name as a command. This is done with the
22715 @code{define} command. User commands may accept up to 10 arguments
22716 separated by whitespace. Arguments are accessed within the user command
22717 via @code{$arg0@dots{}$arg9}. A trivial example:
22721 print $arg0 + $arg1 + $arg2
22726 To execute the command use:
22733 This defines the command @code{adder}, which prints the sum of
22734 its three arguments. Note the arguments are text substitutions, so they may
22735 reference variables, use complex expressions, or even perform inferior
22738 @cindex argument count in user-defined commands
22739 @cindex how many arguments (user-defined commands)
22740 In addition, @code{$argc} may be used to find out how many arguments have
22741 been passed. This expands to a number in the range 0@dots{}10.
22746 print $arg0 + $arg1
22749 print $arg0 + $arg1 + $arg2
22757 @item define @var{commandname}
22758 Define a command named @var{commandname}. If there is already a command
22759 by that name, you are asked to confirm that you want to redefine it.
22760 @var{commandname} may be a bare command name consisting of letters,
22761 numbers, dashes, and underscores. It may also start with any predefined
22762 prefix command. For example, @samp{define target my-target} creates
22763 a user-defined @samp{target my-target} command.
22765 The definition of the command is made up of other @value{GDBN} command lines,
22766 which are given following the @code{define} command. The end of these
22767 commands is marked by a line containing @code{end}.
22770 @kindex end@r{ (user-defined commands)}
22771 @item document @var{commandname}
22772 Document the user-defined command @var{commandname}, so that it can be
22773 accessed by @code{help}. The command @var{commandname} must already be
22774 defined. This command reads lines of documentation just as @code{define}
22775 reads the lines of the command definition, ending with @code{end}.
22776 After the @code{document} command is finished, @code{help} on command
22777 @var{commandname} displays the documentation you have written.
22779 You may use the @code{document} command again to change the
22780 documentation of a command. Redefining the command with @code{define}
22781 does not change the documentation.
22783 @kindex dont-repeat
22784 @cindex don't repeat command
22786 Used inside a user-defined command, this tells @value{GDBN} that this
22787 command should not be repeated when the user hits @key{RET}
22788 (@pxref{Command Syntax, repeat last command}).
22790 @kindex help user-defined
22791 @item help user-defined
22792 List all user-defined commands and all python commands defined in class
22793 COMAND_USER. The first line of the documentation or docstring is
22798 @itemx show user @var{commandname}
22799 Display the @value{GDBN} commands used to define @var{commandname} (but
22800 not its documentation). If no @var{commandname} is given, display the
22801 definitions for all user-defined commands.
22802 This does not work for user-defined python commands.
22804 @cindex infinite recursion in user-defined commands
22805 @kindex show max-user-call-depth
22806 @kindex set max-user-call-depth
22807 @item show max-user-call-depth
22808 @itemx set max-user-call-depth
22809 The value of @code{max-user-call-depth} controls how many recursion
22810 levels are allowed in user-defined commands before @value{GDBN} suspects an
22811 infinite recursion and aborts the command.
22812 This does not apply to user-defined python commands.
22815 In addition to the above commands, user-defined commands frequently
22816 use control flow commands, described in @ref{Command Files}.
22818 When user-defined commands are executed, the
22819 commands of the definition are not printed. An error in any command
22820 stops execution of the user-defined command.
22822 If used interactively, commands that would ask for confirmation proceed
22823 without asking when used inside a user-defined command. Many @value{GDBN}
22824 commands that normally print messages to say what they are doing omit the
22825 messages when used in a user-defined command.
22828 @subsection User-defined Command Hooks
22829 @cindex command hooks
22830 @cindex hooks, for commands
22831 @cindex hooks, pre-command
22834 You may define @dfn{hooks}, which are a special kind of user-defined
22835 command. Whenever you run the command @samp{foo}, if the user-defined
22836 command @samp{hook-foo} exists, it is executed (with no arguments)
22837 before that command.
22839 @cindex hooks, post-command
22841 A hook may also be defined which is run after the command you executed.
22842 Whenever you run the command @samp{foo}, if the user-defined command
22843 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22844 that command. Post-execution hooks may exist simultaneously with
22845 pre-execution hooks, for the same command.
22847 It is valid for a hook to call the command which it hooks. If this
22848 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22850 @c It would be nice if hookpost could be passed a parameter indicating
22851 @c if the command it hooks executed properly or not. FIXME!
22853 @kindex stop@r{, a pseudo-command}
22854 In addition, a pseudo-command, @samp{stop} exists. Defining
22855 (@samp{hook-stop}) makes the associated commands execute every time
22856 execution stops in your program: before breakpoint commands are run,
22857 displays are printed, or the stack frame is printed.
22859 For example, to ignore @code{SIGALRM} signals while
22860 single-stepping, but treat them normally during normal execution,
22865 handle SIGALRM nopass
22869 handle SIGALRM pass
22872 define hook-continue
22873 handle SIGALRM pass
22877 As a further example, to hook at the beginning and end of the @code{echo}
22878 command, and to add extra text to the beginning and end of the message,
22886 define hookpost-echo
22890 (@value{GDBP}) echo Hello World
22891 <<<---Hello World--->>>
22896 You can define a hook for any single-word command in @value{GDBN}, but
22897 not for command aliases; you should define a hook for the basic command
22898 name, e.g.@: @code{backtrace} rather than @code{bt}.
22899 @c FIXME! So how does Joe User discover whether a command is an alias
22901 You can hook a multi-word command by adding @code{hook-} or
22902 @code{hookpost-} to the last word of the command, e.g.@:
22903 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22905 If an error occurs during the execution of your hook, execution of
22906 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22907 (before the command that you actually typed had a chance to run).
22909 If you try to define a hook which does not match any known command, you
22910 get a warning from the @code{define} command.
22912 @node Command Files
22913 @subsection Command Files
22915 @cindex command files
22916 @cindex scripting commands
22917 A command file for @value{GDBN} is a text file made of lines that are
22918 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22919 also be included. An empty line in a command file does nothing; it
22920 does not mean to repeat the last command, as it would from the
22923 You can request the execution of a command file with the @code{source}
22924 command. Note that the @code{source} command is also used to evaluate
22925 scripts that are not Command Files. The exact behavior can be configured
22926 using the @code{script-extension} setting.
22927 @xref{Extending GDB,, Extending GDB}.
22931 @cindex execute commands from a file
22932 @item source [-s] [-v] @var{filename}
22933 Execute the command file @var{filename}.
22936 The lines in a command file are generally executed sequentially,
22937 unless the order of execution is changed by one of the
22938 @emph{flow-control commands} described below. The commands are not
22939 printed as they are executed. An error in any command terminates
22940 execution of the command file and control is returned to the console.
22942 @value{GDBN} first searches for @var{filename} in the current directory.
22943 If the file is not found there, and @var{filename} does not specify a
22944 directory, then @value{GDBN} also looks for the file on the source search path
22945 (specified with the @samp{directory} command);
22946 except that @file{$cdir} is not searched because the compilation directory
22947 is not relevant to scripts.
22949 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22950 on the search path even if @var{filename} specifies a directory.
22951 The search is done by appending @var{filename} to each element of the
22952 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22953 and the search path contains @file{/home/user} then @value{GDBN} will
22954 look for the script @file{/home/user/mylib/myscript}.
22955 The search is also done if @var{filename} is an absolute path.
22956 For example, if @var{filename} is @file{/tmp/myscript} and
22957 the search path contains @file{/home/user} then @value{GDBN} will
22958 look for the script @file{/home/user/tmp/myscript}.
22959 For DOS-like systems, if @var{filename} contains a drive specification,
22960 it is stripped before concatenation. For example, if @var{filename} is
22961 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22962 will look for the script @file{c:/tmp/myscript}.
22964 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22965 each command as it is executed. The option must be given before
22966 @var{filename}, and is interpreted as part of the filename anywhere else.
22968 Commands that would ask for confirmation if used interactively proceed
22969 without asking when used in a command file. Many @value{GDBN} commands that
22970 normally print messages to say what they are doing omit the messages
22971 when called from command files.
22973 @value{GDBN} also accepts command input from standard input. In this
22974 mode, normal output goes to standard output and error output goes to
22975 standard error. Errors in a command file supplied on standard input do
22976 not terminate execution of the command file---execution continues with
22980 gdb < cmds > log 2>&1
22983 (The syntax above will vary depending on the shell used.) This example
22984 will execute commands from the file @file{cmds}. All output and errors
22985 would be directed to @file{log}.
22987 Since commands stored on command files tend to be more general than
22988 commands typed interactively, they frequently need to deal with
22989 complicated situations, such as different or unexpected values of
22990 variables and symbols, changes in how the program being debugged is
22991 built, etc. @value{GDBN} provides a set of flow-control commands to
22992 deal with these complexities. Using these commands, you can write
22993 complex scripts that loop over data structures, execute commands
22994 conditionally, etc.
23001 This command allows to include in your script conditionally executed
23002 commands. The @code{if} command takes a single argument, which is an
23003 expression to evaluate. It is followed by a series of commands that
23004 are executed only if the expression is true (its value is nonzero).
23005 There can then optionally be an @code{else} line, followed by a series
23006 of commands that are only executed if the expression was false. The
23007 end of the list is marked by a line containing @code{end}.
23011 This command allows to write loops. Its syntax is similar to
23012 @code{if}: the command takes a single argument, which is an expression
23013 to evaluate, and must be followed by the commands to execute, one per
23014 line, terminated by an @code{end}. These commands are called the
23015 @dfn{body} of the loop. The commands in the body of @code{while} are
23016 executed repeatedly as long as the expression evaluates to true.
23020 This command exits the @code{while} loop in whose body it is included.
23021 Execution of the script continues after that @code{while}s @code{end}
23024 @kindex loop_continue
23025 @item loop_continue
23026 This command skips the execution of the rest of the body of commands
23027 in the @code{while} loop in whose body it is included. Execution
23028 branches to the beginning of the @code{while} loop, where it evaluates
23029 the controlling expression.
23031 @kindex end@r{ (if/else/while commands)}
23033 Terminate the block of commands that are the body of @code{if},
23034 @code{else}, or @code{while} flow-control commands.
23039 @subsection Commands for Controlled Output
23041 During the execution of a command file or a user-defined command, normal
23042 @value{GDBN} output is suppressed; the only output that appears is what is
23043 explicitly printed by the commands in the definition. This section
23044 describes three commands useful for generating exactly the output you
23049 @item echo @var{text}
23050 @c I do not consider backslash-space a standard C escape sequence
23051 @c because it is not in ANSI.
23052 Print @var{text}. Nonprinting characters can be included in
23053 @var{text} using C escape sequences, such as @samp{\n} to print a
23054 newline. @strong{No newline is printed unless you specify one.}
23055 In addition to the standard C escape sequences, a backslash followed
23056 by a space stands for a space. This is useful for displaying a
23057 string with spaces at the beginning or the end, since leading and
23058 trailing spaces are otherwise trimmed from all arguments.
23059 To print @samp{@w{ }and foo =@w{ }}, use the command
23060 @samp{echo \@w{ }and foo = \@w{ }}.
23062 A backslash at the end of @var{text} can be used, as in C, to continue
23063 the command onto subsequent lines. For example,
23066 echo This is some text\n\
23067 which is continued\n\
23068 onto several lines.\n
23071 produces the same output as
23074 echo This is some text\n
23075 echo which is continued\n
23076 echo onto several lines.\n
23080 @item output @var{expression}
23081 Print the value of @var{expression} and nothing but that value: no
23082 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23083 value history either. @xref{Expressions, ,Expressions}, for more information
23086 @item output/@var{fmt} @var{expression}
23087 Print the value of @var{expression} in format @var{fmt}. You can use
23088 the same formats as for @code{print}. @xref{Output Formats,,Output
23089 Formats}, for more information.
23092 @item printf @var{template}, @var{expressions}@dots{}
23093 Print the values of one or more @var{expressions} under the control of
23094 the string @var{template}. To print several values, make
23095 @var{expressions} be a comma-separated list of individual expressions,
23096 which may be either numbers or pointers. Their values are printed as
23097 specified by @var{template}, exactly as a C program would do by
23098 executing the code below:
23101 printf (@var{template}, @var{expressions}@dots{});
23104 As in @code{C} @code{printf}, ordinary characters in @var{template}
23105 are printed verbatim, while @dfn{conversion specification} introduced
23106 by the @samp{%} character cause subsequent @var{expressions} to be
23107 evaluated, their values converted and formatted according to type and
23108 style information encoded in the conversion specifications, and then
23111 For example, you can print two values in hex like this:
23114 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23117 @code{printf} supports all the standard @code{C} conversion
23118 specifications, including the flags and modifiers between the @samp{%}
23119 character and the conversion letter, with the following exceptions:
23123 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23126 The modifier @samp{*} is not supported for specifying precision or
23130 The @samp{'} flag (for separation of digits into groups according to
23131 @code{LC_NUMERIC'}) is not supported.
23134 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23138 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23141 The conversion letters @samp{a} and @samp{A} are not supported.
23145 Note that the @samp{ll} type modifier is supported only if the
23146 underlying @code{C} implementation used to build @value{GDBN} supports
23147 the @code{long long int} type, and the @samp{L} type modifier is
23148 supported only if @code{long double} type is available.
23150 As in @code{C}, @code{printf} supports simple backslash-escape
23151 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23152 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23153 single character. Octal and hexadecimal escape sequences are not
23156 Additionally, @code{printf} supports conversion specifications for DFP
23157 (@dfn{Decimal Floating Point}) types using the following length modifiers
23158 together with a floating point specifier.
23163 @samp{H} for printing @code{Decimal32} types.
23166 @samp{D} for printing @code{Decimal64} types.
23169 @samp{DD} for printing @code{Decimal128} types.
23172 If the underlying @code{C} implementation used to build @value{GDBN} has
23173 support for the three length modifiers for DFP types, other modifiers
23174 such as width and precision will also be available for @value{GDBN} to use.
23176 In case there is no such @code{C} support, no additional modifiers will be
23177 available and the value will be printed in the standard way.
23179 Here's an example of printing DFP types using the above conversion letters:
23181 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23185 @item eval @var{template}, @var{expressions}@dots{}
23186 Convert the values of one or more @var{expressions} under the control of
23187 the string @var{template} to a command line, and call it.
23192 @section Scripting @value{GDBN} using Python
23193 @cindex python scripting
23194 @cindex scripting with python
23196 You can script @value{GDBN} using the @uref{http://www.python.org/,
23197 Python programming language}. This feature is available only if
23198 @value{GDBN} was configured using @option{--with-python}.
23200 @cindex python directory
23201 Python scripts used by @value{GDBN} should be installed in
23202 @file{@var{data-directory}/python}, where @var{data-directory} is
23203 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23204 This directory, known as the @dfn{python directory},
23205 is automatically added to the Python Search Path in order to allow
23206 the Python interpreter to locate all scripts installed at this location.
23208 Additionally, @value{GDBN} commands and convenience functions which
23209 are written in Python and are located in the
23210 @file{@var{data-directory}/python/gdb/command} or
23211 @file{@var{data-directory}/python/gdb/function} directories are
23212 automatically imported when @value{GDBN} starts.
23215 * Python Commands:: Accessing Python from @value{GDBN}.
23216 * Python API:: Accessing @value{GDBN} from Python.
23217 * Python Auto-loading:: Automatically loading Python code.
23218 * Python modules:: Python modules provided by @value{GDBN}.
23221 @node Python Commands
23222 @subsection Python Commands
23223 @cindex python commands
23224 @cindex commands to access python
23226 @value{GDBN} provides two commands for accessing the Python interpreter,
23227 and one related setting:
23230 @kindex python-interactive
23232 @item python-interactive @r{[}@var{command}@r{]}
23233 @itemx pi @r{[}@var{command}@r{]}
23234 Without an argument, the @code{python-interactive} command can be used
23235 to start an interactive Python prompt. To return to @value{GDBN},
23236 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23238 Alternatively, a single-line Python command can be given as an
23239 argument and evaluated. If the command is an expression, the result
23240 will be printed; otherwise, nothing will be printed. For example:
23243 (@value{GDBP}) python-interactive 2 + 3
23249 @item python @r{[}@var{command}@r{]}
23250 @itemx py @r{[}@var{command}@r{]}
23251 The @code{python} command can be used to evaluate Python code.
23253 If given an argument, the @code{python} command will evaluate the
23254 argument as a Python command. For example:
23257 (@value{GDBP}) python print 23
23261 If you do not provide an argument to @code{python}, it will act as a
23262 multi-line command, like @code{define}. In this case, the Python
23263 script is made up of subsequent command lines, given after the
23264 @code{python} command. This command list is terminated using a line
23265 containing @code{end}. For example:
23268 (@value{GDBP}) python
23270 End with a line saying just "end".
23276 @kindex set python print-stack
23277 @item set python print-stack
23278 By default, @value{GDBN} will print only the message component of a
23279 Python exception when an error occurs in a Python script. This can be
23280 controlled using @code{set python print-stack}: if @code{full}, then
23281 full Python stack printing is enabled; if @code{none}, then Python stack
23282 and message printing is disabled; if @code{message}, the default, only
23283 the message component of the error is printed.
23286 It is also possible to execute a Python script from the @value{GDBN}
23290 @item source @file{script-name}
23291 The script name must end with @samp{.py} and @value{GDBN} must be configured
23292 to recognize the script language based on filename extension using
23293 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23295 @item python execfile ("script-name")
23296 This method is based on the @code{execfile} Python built-in function,
23297 and thus is always available.
23301 @subsection Python API
23303 @cindex programming in python
23305 You can get quick online help for @value{GDBN}'s Python API by issuing
23306 the command @w{@kbd{python help (gdb)}}.
23308 Functions and methods which have two or more optional arguments allow
23309 them to be specified using keyword syntax. This allows passing some
23310 optional arguments while skipping others. Example:
23311 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23314 * Basic Python:: Basic Python Functions.
23315 * Exception Handling:: How Python exceptions are translated.
23316 * Values From Inferior:: Python representation of values.
23317 * Types In Python:: Python representation of types.
23318 * Pretty Printing API:: Pretty-printing values.
23319 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23320 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23321 * Type Printing API:: Pretty-printing types.
23322 * Frame Filter API:: Filtering Frames.
23323 * Frame Decorator API:: Decorating Frames.
23324 * Writing a Frame Filter:: Writing a Frame Filter.
23325 * Inferiors In Python:: Python representation of inferiors (processes)
23326 * Events In Python:: Listening for events from @value{GDBN}.
23327 * Threads In Python:: Accessing inferior threads from Python.
23328 * Commands In Python:: Implementing new commands in Python.
23329 * Parameters In Python:: Adding new @value{GDBN} parameters.
23330 * Functions In Python:: Writing new convenience functions.
23331 * Progspaces In Python:: Program spaces.
23332 * Objfiles In Python:: Object files.
23333 * Frames In Python:: Accessing inferior stack frames from Python.
23334 * Blocks In Python:: Accessing blocks from Python.
23335 * Symbols In Python:: Python representation of symbols.
23336 * Symbol Tables In Python:: Python representation of symbol tables.
23337 * Breakpoints In Python:: Manipulating breakpoints using Python.
23338 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23340 * Lazy Strings In Python:: Python representation of lazy strings.
23341 * Architectures In Python:: Python representation of architectures.
23345 @subsubsection Basic Python
23347 @cindex python stdout
23348 @cindex python pagination
23349 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23350 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23351 A Python program which outputs to one of these streams may have its
23352 output interrupted by the user (@pxref{Screen Size}). In this
23353 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23355 Some care must be taken when writing Python code to run in
23356 @value{GDBN}. Two things worth noting in particular:
23360 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23361 Python code must not override these, or even change the options using
23362 @code{sigaction}. If your program changes the handling of these
23363 signals, @value{GDBN} will most likely stop working correctly. Note
23364 that it is unfortunately common for GUI toolkits to install a
23365 @code{SIGCHLD} handler.
23368 @value{GDBN} takes care to mark its internal file descriptors as
23369 close-on-exec. However, this cannot be done in a thread-safe way on
23370 all platforms. Your Python programs should be aware of this and
23371 should both create new file descriptors with the close-on-exec flag
23372 set and arrange to close unneeded file descriptors before starting a
23376 @cindex python functions
23377 @cindex python module
23379 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23380 methods and classes added by @value{GDBN} are placed in this module.
23381 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23382 use in all scripts evaluated by the @code{python} command.
23384 @findex gdb.PYTHONDIR
23385 @defvar gdb.PYTHONDIR
23386 A string containing the python directory (@pxref{Python}).
23389 @findex gdb.execute
23390 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23391 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23392 If a GDB exception happens while @var{command} runs, it is
23393 translated as described in @ref{Exception Handling,,Exception Handling}.
23395 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23396 command as having originated from the user invoking it interactively.
23397 It must be a boolean value. If omitted, it defaults to @code{False}.
23399 By default, any output produced by @var{command} is sent to
23400 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23401 @code{True}, then output will be collected by @code{gdb.execute} and
23402 returned as a string. The default is @code{False}, in which case the
23403 return value is @code{None}. If @var{to_string} is @code{True}, the
23404 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23405 and height, and its pagination will be disabled; @pxref{Screen Size}.
23408 @findex gdb.breakpoints
23409 @defun gdb.breakpoints ()
23410 Return a sequence holding all of @value{GDBN}'s breakpoints.
23411 @xref{Breakpoints In Python}, for more information.
23414 @findex gdb.parameter
23415 @defun gdb.parameter (parameter)
23416 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23417 string naming the parameter to look up; @var{parameter} may contain
23418 spaces if the parameter has a multi-part name. For example,
23419 @samp{print object} is a valid parameter name.
23421 If the named parameter does not exist, this function throws a
23422 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23423 parameter's value is converted to a Python value of the appropriate
23424 type, and returned.
23427 @findex gdb.history
23428 @defun gdb.history (number)
23429 Return a value from @value{GDBN}'s value history (@pxref{Value
23430 History}). @var{number} indicates which history element to return.
23431 If @var{number} is negative, then @value{GDBN} will take its absolute value
23432 and count backward from the last element (i.e., the most recent element) to
23433 find the value to return. If @var{number} is zero, then @value{GDBN} will
23434 return the most recent element. If the element specified by @var{number}
23435 doesn't exist in the value history, a @code{gdb.error} exception will be
23438 If no exception is raised, the return value is always an instance of
23439 @code{gdb.Value} (@pxref{Values From Inferior}).
23442 @findex gdb.parse_and_eval
23443 @defun gdb.parse_and_eval (expression)
23444 Parse @var{expression} as an expression in the current language,
23445 evaluate it, and return the result as a @code{gdb.Value}.
23446 @var{expression} must be a string.
23448 This function can be useful when implementing a new command
23449 (@pxref{Commands In Python}), as it provides a way to parse the
23450 command's argument as an expression. It is also useful simply to
23451 compute values, for example, it is the only way to get the value of a
23452 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23455 @findex gdb.find_pc_line
23456 @defun gdb.find_pc_line (pc)
23457 Return the @code{gdb.Symtab_and_line} object corresponding to the
23458 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23459 value of @var{pc} is passed as an argument, then the @code{symtab} and
23460 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23461 will be @code{None} and 0 respectively.
23464 @findex gdb.post_event
23465 @defun gdb.post_event (event)
23466 Put @var{event}, a callable object taking no arguments, into
23467 @value{GDBN}'s internal event queue. This callable will be invoked at
23468 some later point, during @value{GDBN}'s event processing. Events
23469 posted using @code{post_event} will be run in the order in which they
23470 were posted; however, there is no way to know when they will be
23471 processed relative to other events inside @value{GDBN}.
23473 @value{GDBN} is not thread-safe. If your Python program uses multiple
23474 threads, you must be careful to only call @value{GDBN}-specific
23475 functions in the main @value{GDBN} thread. @code{post_event} ensures
23479 (@value{GDBP}) python
23483 > def __init__(self, message):
23484 > self.message = message;
23485 > def __call__(self):
23486 > gdb.write(self.message)
23488 >class MyThread1 (threading.Thread):
23490 > gdb.post_event(Writer("Hello "))
23492 >class MyThread2 (threading.Thread):
23494 > gdb.post_event(Writer("World\n"))
23496 >MyThread1().start()
23497 >MyThread2().start()
23499 (@value{GDBP}) Hello World
23504 @defun gdb.write (string @r{[}, stream{]})
23505 Print a string to @value{GDBN}'s paginated output stream. The
23506 optional @var{stream} determines the stream to print to. The default
23507 stream is @value{GDBN}'s standard output stream. Possible stream
23514 @value{GDBN}'s standard output stream.
23519 @value{GDBN}'s standard error stream.
23524 @value{GDBN}'s log stream (@pxref{Logging Output}).
23527 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23528 call this function and will automatically direct the output to the
23533 @defun gdb.flush ()
23534 Flush the buffer of a @value{GDBN} paginated stream so that the
23535 contents are displayed immediately. @value{GDBN} will flush the
23536 contents of a stream automatically when it encounters a newline in the
23537 buffer. The optional @var{stream} determines the stream to flush. The
23538 default stream is @value{GDBN}'s standard output stream. Possible
23545 @value{GDBN}'s standard output stream.
23550 @value{GDBN}'s standard error stream.
23555 @value{GDBN}'s log stream (@pxref{Logging Output}).
23559 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23560 call this function for the relevant stream.
23563 @findex gdb.target_charset
23564 @defun gdb.target_charset ()
23565 Return the name of the current target character set (@pxref{Character
23566 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23567 that @samp{auto} is never returned.
23570 @findex gdb.target_wide_charset
23571 @defun gdb.target_wide_charset ()
23572 Return the name of the current target wide character set
23573 (@pxref{Character Sets}). This differs from
23574 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23578 @findex gdb.solib_name
23579 @defun gdb.solib_name (address)
23580 Return the name of the shared library holding the given @var{address}
23581 as a string, or @code{None}.
23584 @findex gdb.decode_line
23585 @defun gdb.decode_line @r{[}expression@r{]}
23586 Return locations of the line specified by @var{expression}, or of the
23587 current line if no argument was given. This function returns a Python
23588 tuple containing two elements. The first element contains a string
23589 holding any unparsed section of @var{expression} (or @code{None} if
23590 the expression has been fully parsed). The second element contains
23591 either @code{None} or another tuple that contains all the locations
23592 that match the expression represented as @code{gdb.Symtab_and_line}
23593 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23594 provided, it is decoded the way that @value{GDBN}'s inbuilt
23595 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23598 @defun gdb.prompt_hook (current_prompt)
23599 @anchor{prompt_hook}
23601 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23602 assigned to this operation before a prompt is displayed by
23605 The parameter @code{current_prompt} contains the current @value{GDBN}
23606 prompt. This method must return a Python string, or @code{None}. If
23607 a string is returned, the @value{GDBN} prompt will be set to that
23608 string. If @code{None} is returned, @value{GDBN} will continue to use
23609 the current prompt.
23611 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23612 such as those used by readline for command input, and annotation
23613 related prompts are prohibited from being changed.
23616 @node Exception Handling
23617 @subsubsection Exception Handling
23618 @cindex python exceptions
23619 @cindex exceptions, python
23621 When executing the @code{python} command, Python exceptions
23622 uncaught within the Python code are translated to calls to
23623 @value{GDBN} error-reporting mechanism. If the command that called
23624 @code{python} does not handle the error, @value{GDBN} will
23625 terminate it and print an error message containing the Python
23626 exception name, the associated value, and the Python call stack
23627 backtrace at the point where the exception was raised. Example:
23630 (@value{GDBP}) python print foo
23631 Traceback (most recent call last):
23632 File "<string>", line 1, in <module>
23633 NameError: name 'foo' is not defined
23636 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23637 Python code are converted to Python exceptions. The type of the
23638 Python exception depends on the error.
23642 This is the base class for most exceptions generated by @value{GDBN}.
23643 It is derived from @code{RuntimeError}, for compatibility with earlier
23644 versions of @value{GDBN}.
23646 If an error occurring in @value{GDBN} does not fit into some more
23647 specific category, then the generated exception will have this type.
23649 @item gdb.MemoryError
23650 This is a subclass of @code{gdb.error} which is thrown when an
23651 operation tried to access invalid memory in the inferior.
23653 @item KeyboardInterrupt
23654 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23655 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23658 In all cases, your exception handler will see the @value{GDBN} error
23659 message as its value and the Python call stack backtrace at the Python
23660 statement closest to where the @value{GDBN} error occured as the
23663 @findex gdb.GdbError
23664 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23665 it is useful to be able to throw an exception that doesn't cause a
23666 traceback to be printed. For example, the user may have invoked the
23667 command incorrectly. Use the @code{gdb.GdbError} exception
23668 to handle this case. Example:
23672 >class HelloWorld (gdb.Command):
23673 > """Greet the whole world."""
23674 > def __init__ (self):
23675 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23676 > def invoke (self, args, from_tty):
23677 > argv = gdb.string_to_argv (args)
23678 > if len (argv) != 0:
23679 > raise gdb.GdbError ("hello-world takes no arguments")
23680 > print "Hello, World!"
23683 (gdb) hello-world 42
23684 hello-world takes no arguments
23687 @node Values From Inferior
23688 @subsubsection Values From Inferior
23689 @cindex values from inferior, with Python
23690 @cindex python, working with values from inferior
23692 @cindex @code{gdb.Value}
23693 @value{GDBN} provides values it obtains from the inferior program in
23694 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23695 for its internal bookkeeping of the inferior's values, and for
23696 fetching values when necessary.
23698 Inferior values that are simple scalars can be used directly in
23699 Python expressions that are valid for the value's data type. Here's
23700 an example for an integer or floating-point value @code{some_val}:
23707 As result of this, @code{bar} will also be a @code{gdb.Value} object
23708 whose values are of the same type as those of @code{some_val}.
23710 Inferior values that are structures or instances of some class can
23711 be accessed using the Python @dfn{dictionary syntax}. For example, if
23712 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23713 can access its @code{foo} element with:
23716 bar = some_val['foo']
23719 Again, @code{bar} will also be a @code{gdb.Value} object.
23721 A @code{gdb.Value} that represents a function can be executed via
23722 inferior function call. Any arguments provided to the call must match
23723 the function's prototype, and must be provided in the order specified
23726 For example, @code{some_val} is a @code{gdb.Value} instance
23727 representing a function that takes two integers as arguments. To
23728 execute this function, call it like so:
23731 result = some_val (10,20)
23734 Any values returned from a function call will be stored as a
23737 The following attributes are provided:
23739 @defvar Value.address
23740 If this object is addressable, this read-only attribute holds a
23741 @code{gdb.Value} object representing the address. Otherwise,
23742 this attribute holds @code{None}.
23745 @cindex optimized out value in Python
23746 @defvar Value.is_optimized_out
23747 This read-only boolean attribute is true if the compiler optimized out
23748 this value, thus it is not available for fetching from the inferior.
23752 The type of this @code{gdb.Value}. The value of this attribute is a
23753 @code{gdb.Type} object (@pxref{Types In Python}).
23756 @defvar Value.dynamic_type
23757 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23758 type information (@acronym{RTTI}) to determine the dynamic type of the
23759 value. If this value is of class type, it will return the class in
23760 which the value is embedded, if any. If this value is of pointer or
23761 reference to a class type, it will compute the dynamic type of the
23762 referenced object, and return a pointer or reference to that type,
23763 respectively. In all other cases, it will return the value's static
23766 Note that this feature will only work when debugging a C@t{++} program
23767 that includes @acronym{RTTI} for the object in question. Otherwise,
23768 it will just return the static type of the value as in @kbd{ptype foo}
23769 (@pxref{Symbols, ptype}).
23772 @defvar Value.is_lazy
23773 The value of this read-only boolean attribute is @code{True} if this
23774 @code{gdb.Value} has not yet been fetched from the inferior.
23775 @value{GDBN} does not fetch values until necessary, for efficiency.
23779 myval = gdb.parse_and_eval ('somevar')
23782 The value of @code{somevar} is not fetched at this time. It will be
23783 fetched when the value is needed, or when the @code{fetch_lazy}
23787 The following methods are provided:
23789 @defun Value.__init__ (@var{val})
23790 Many Python values can be converted directly to a @code{gdb.Value} via
23791 this object initializer. Specifically:
23794 @item Python boolean
23795 A Python boolean is converted to the boolean type from the current
23798 @item Python integer
23799 A Python integer is converted to the C @code{long} type for the
23800 current architecture.
23803 A Python long is converted to the C @code{long long} type for the
23804 current architecture.
23807 A Python float is converted to the C @code{double} type for the
23808 current architecture.
23810 @item Python string
23811 A Python string is converted to a target string, using the current
23814 @item @code{gdb.Value}
23815 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23817 @item @code{gdb.LazyString}
23818 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23819 Python}), then the lazy string's @code{value} method is called, and
23820 its result is used.
23824 @defun Value.cast (type)
23825 Return a new instance of @code{gdb.Value} that is the result of
23826 casting this instance to the type described by @var{type}, which must
23827 be a @code{gdb.Type} object. If the cast cannot be performed for some
23828 reason, this method throws an exception.
23831 @defun Value.dereference ()
23832 For pointer data types, this method returns a new @code{gdb.Value} object
23833 whose contents is the object pointed to by the pointer. For example, if
23834 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23841 then you can use the corresponding @code{gdb.Value} to access what
23842 @code{foo} points to like this:
23845 bar = foo.dereference ()
23848 The result @code{bar} will be a @code{gdb.Value} object holding the
23849 value pointed to by @code{foo}.
23851 A similar function @code{Value.referenced_value} exists which also
23852 returns @code{gdb.Value} objects corresonding to the values pointed to
23853 by pointer values (and additionally, values referenced by reference
23854 values). However, the behavior of @code{Value.dereference}
23855 differs from @code{Value.referenced_value} by the fact that the
23856 behavior of @code{Value.dereference} is identical to applying the C
23857 unary operator @code{*} on a given value. For example, consider a
23858 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23862 typedef int *intptr;
23866 intptr &ptrref = ptr;
23869 Though @code{ptrref} is a reference value, one can apply the method
23870 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23871 to it and obtain a @code{gdb.Value} which is identical to that
23872 corresponding to @code{val}. However, if you apply the method
23873 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23874 object identical to that corresponding to @code{ptr}.
23877 py_ptrref = gdb.parse_and_eval ("ptrref")
23878 py_val = py_ptrref.dereference ()
23879 py_ptr = py_ptrref.referenced_value ()
23882 The @code{gdb.Value} object @code{py_val} is identical to that
23883 corresponding to @code{val}, and @code{py_ptr} is identical to that
23884 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23885 be applied whenever the C unary operator @code{*} can be applied
23886 to the corresponding C value. For those cases where applying both
23887 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23888 the results obtained need not be identical (as we have seen in the above
23889 example). The results are however identical when applied on
23890 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23891 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23894 @defun Value.referenced_value ()
23895 For pointer or reference data types, this method returns a new
23896 @code{gdb.Value} object corresponding to the value referenced by the
23897 pointer/reference value. For pointer data types,
23898 @code{Value.dereference} and @code{Value.referenced_value} produce
23899 identical results. The difference between these methods is that
23900 @code{Value.dereference} cannot get the values referenced by reference
23901 values. For example, consider a reference to an @code{int}, declared
23902 in your C@t{++} program as
23910 then applying @code{Value.dereference} to the @code{gdb.Value} object
23911 corresponding to @code{ref} will result in an error, while applying
23912 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23913 identical to that corresponding to @code{val}.
23916 py_ref = gdb.parse_and_eval ("ref")
23917 er_ref = py_ref.dereference () # Results in error
23918 py_val = py_ref.referenced_value () # Returns the referenced value
23921 The @code{gdb.Value} object @code{py_val} is identical to that
23922 corresponding to @code{val}.
23925 @defun Value.dynamic_cast (type)
23926 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23927 operator were used. Consult a C@t{++} reference for details.
23930 @defun Value.reinterpret_cast (type)
23931 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23932 operator were used. Consult a C@t{++} reference for details.
23935 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23936 If this @code{gdb.Value} represents a string, then this method
23937 converts the contents to a Python string. Otherwise, this method will
23938 throw an exception.
23940 Strings are recognized in a language-specific way; whether a given
23941 @code{gdb.Value} represents a string is determined by the current
23944 For C-like languages, a value is a string if it is a pointer to or an
23945 array of characters or ints. The string is assumed to be terminated
23946 by a zero of the appropriate width. However if the optional length
23947 argument is given, the string will be converted to that given length,
23948 ignoring any embedded zeros that the string may contain.
23950 If the optional @var{encoding} argument is given, it must be a string
23951 naming the encoding of the string in the @code{gdb.Value}, such as
23952 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23953 the same encodings as the corresponding argument to Python's
23954 @code{string.decode} method, and the Python codec machinery will be used
23955 to convert the string. If @var{encoding} is not given, or if
23956 @var{encoding} is the empty string, then either the @code{target-charset}
23957 (@pxref{Character Sets}) will be used, or a language-specific encoding
23958 will be used, if the current language is able to supply one.
23960 The optional @var{errors} argument is the same as the corresponding
23961 argument to Python's @code{string.decode} method.
23963 If the optional @var{length} argument is given, the string will be
23964 fetched and converted to the given length.
23967 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23968 If this @code{gdb.Value} represents a string, then this method
23969 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23970 In Python}). Otherwise, this method will throw an exception.
23972 If the optional @var{encoding} argument is given, it must be a string
23973 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23974 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23975 @var{encoding} argument is an encoding that @value{GDBN} does
23976 recognize, @value{GDBN} will raise an error.
23978 When a lazy string is printed, the @value{GDBN} encoding machinery is
23979 used to convert the string during printing. If the optional
23980 @var{encoding} argument is not provided, or is an empty string,
23981 @value{GDBN} will automatically select the encoding most suitable for
23982 the string type. For further information on encoding in @value{GDBN}
23983 please see @ref{Character Sets}.
23985 If the optional @var{length} argument is given, the string will be
23986 fetched and encoded to the length of characters specified. If
23987 the @var{length} argument is not provided, the string will be fetched
23988 and encoded until a null of appropriate width is found.
23991 @defun Value.fetch_lazy ()
23992 If the @code{gdb.Value} object is currently a lazy value
23993 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23994 fetched from the inferior. Any errors that occur in the process
23995 will produce a Python exception.
23997 If the @code{gdb.Value} object is not a lazy value, this method
24000 This method does not return a value.
24004 @node Types In Python
24005 @subsubsection Types In Python
24006 @cindex types in Python
24007 @cindex Python, working with types
24010 @value{GDBN} represents types from the inferior using the class
24013 The following type-related functions are available in the @code{gdb}
24016 @findex gdb.lookup_type
24017 @defun gdb.lookup_type (name @r{[}, block@r{]})
24018 This function looks up a type by name. @var{name} is the name of the
24019 type to look up. It must be a string.
24021 If @var{block} is given, then @var{name} is looked up in that scope.
24022 Otherwise, it is searched for globally.
24024 Ordinarily, this function will return an instance of @code{gdb.Type}.
24025 If the named type cannot be found, it will throw an exception.
24028 If the type is a structure or class type, or an enum type, the fields
24029 of that type can be accessed using the Python @dfn{dictionary syntax}.
24030 For example, if @code{some_type} is a @code{gdb.Type} instance holding
24031 a structure type, you can access its @code{foo} field with:
24034 bar = some_type['foo']
24037 @code{bar} will be a @code{gdb.Field} object; see below under the
24038 description of the @code{Type.fields} method for a description of the
24039 @code{gdb.Field} class.
24041 An instance of @code{Type} has the following attributes:
24044 The type code for this type. The type code will be one of the
24045 @code{TYPE_CODE_} constants defined below.
24048 @defvar Type.sizeof
24049 The size of this type, in target @code{char} units. Usually, a
24050 target's @code{char} type will be an 8-bit byte. However, on some
24051 unusual platforms, this type may have a different size.
24055 The tag name for this type. The tag name is the name after
24056 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
24057 languages have this concept. If this type has no tag name, then
24058 @code{None} is returned.
24061 The following methods are provided:
24063 @defun Type.fields ()
24064 For structure and union types, this method returns the fields. Range
24065 types have two fields, the minimum and maximum values. Enum types
24066 have one field per enum constant. Function and method types have one
24067 field per parameter. The base types of C@t{++} classes are also
24068 represented as fields. If the type has no fields, or does not fit
24069 into one of these categories, an empty sequence will be returned.
24071 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
24074 This attribute is not available for @code{static} fields (as in
24075 C@t{++} or Java). For non-@code{static} fields, the value is the bit
24076 position of the field. For @code{enum} fields, the value is the
24077 enumeration member's integer representation.
24080 The name of the field, or @code{None} for anonymous fields.
24083 This is @code{True} if the field is artificial, usually meaning that
24084 it was provided by the compiler and not the user. This attribute is
24085 always provided, and is @code{False} if the field is not artificial.
24087 @item is_base_class
24088 This is @code{True} if the field represents a base class of a C@t{++}
24089 structure. This attribute is always provided, and is @code{False}
24090 if the field is not a base class of the type that is the argument of
24091 @code{fields}, or if that type was not a C@t{++} class.
24094 If the field is packed, or is a bitfield, then this will have a
24095 non-zero value, which is the size of the field in bits. Otherwise,
24096 this will be zero; in this case the field's size is given by its type.
24099 The type of the field. This is usually an instance of @code{Type},
24100 but it can be @code{None} in some situations.
24104 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24105 Return a new @code{gdb.Type} object which represents an array of this
24106 type. If one argument is given, it is the inclusive upper bound of
24107 the array; in this case the lower bound is zero. If two arguments are
24108 given, the first argument is the lower bound of the array, and the
24109 second argument is the upper bound of the array. An array's length
24110 must not be negative, but the bounds can be.
24113 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24114 Return a new @code{gdb.Type} object which represents a vector of this
24115 type. If one argument is given, it is the inclusive upper bound of
24116 the vector; in this case the lower bound is zero. If two arguments are
24117 given, the first argument is the lower bound of the vector, and the
24118 second argument is the upper bound of the vector. A vector's length
24119 must not be negative, but the bounds can be.
24121 The difference between an @code{array} and a @code{vector} is that
24122 arrays behave like in C: when used in expressions they decay to a pointer
24123 to the first element whereas vectors are treated as first class values.
24126 @defun Type.const ()
24127 Return a new @code{gdb.Type} object which represents a
24128 @code{const}-qualified variant of this type.
24131 @defun Type.volatile ()
24132 Return a new @code{gdb.Type} object which represents a
24133 @code{volatile}-qualified variant of this type.
24136 @defun Type.unqualified ()
24137 Return a new @code{gdb.Type} object which represents an unqualified
24138 variant of this type. That is, the result is neither @code{const} nor
24142 @defun Type.range ()
24143 Return a Python @code{Tuple} object that contains two elements: the
24144 low bound of the argument type and the high bound of that type. If
24145 the type does not have a range, @value{GDBN} will raise a
24146 @code{gdb.error} exception (@pxref{Exception Handling}).
24149 @defun Type.reference ()
24150 Return a new @code{gdb.Type} object which represents a reference to this
24154 @defun Type.pointer ()
24155 Return a new @code{gdb.Type} object which represents a pointer to this
24159 @defun Type.strip_typedefs ()
24160 Return a new @code{gdb.Type} that represents the real type,
24161 after removing all layers of typedefs.
24164 @defun Type.target ()
24165 Return a new @code{gdb.Type} object which represents the target type
24168 For a pointer type, the target type is the type of the pointed-to
24169 object. For an array type (meaning C-like arrays), the target type is
24170 the type of the elements of the array. For a function or method type,
24171 the target type is the type of the return value. For a complex type,
24172 the target type is the type of the elements. For a typedef, the
24173 target type is the aliased type.
24175 If the type does not have a target, this method will throw an
24179 @defun Type.template_argument (n @r{[}, block@r{]})
24180 If this @code{gdb.Type} is an instantiation of a template, this will
24181 return a new @code{gdb.Type} which represents the type of the
24182 @var{n}th template argument.
24184 If this @code{gdb.Type} is not a template type, this will throw an
24185 exception. Ordinarily, only C@t{++} code will have template types.
24187 If @var{block} is given, then @var{name} is looked up in that scope.
24188 Otherwise, it is searched for globally.
24192 Each type has a code, which indicates what category this type falls
24193 into. The available type categories are represented by constants
24194 defined in the @code{gdb} module:
24197 @findex TYPE_CODE_PTR
24198 @findex gdb.TYPE_CODE_PTR
24199 @item gdb.TYPE_CODE_PTR
24200 The type is a pointer.
24202 @findex TYPE_CODE_ARRAY
24203 @findex gdb.TYPE_CODE_ARRAY
24204 @item gdb.TYPE_CODE_ARRAY
24205 The type is an array.
24207 @findex TYPE_CODE_STRUCT
24208 @findex gdb.TYPE_CODE_STRUCT
24209 @item gdb.TYPE_CODE_STRUCT
24210 The type is a structure.
24212 @findex TYPE_CODE_UNION
24213 @findex gdb.TYPE_CODE_UNION
24214 @item gdb.TYPE_CODE_UNION
24215 The type is a union.
24217 @findex TYPE_CODE_ENUM
24218 @findex gdb.TYPE_CODE_ENUM
24219 @item gdb.TYPE_CODE_ENUM
24220 The type is an enum.
24222 @findex TYPE_CODE_FLAGS
24223 @findex gdb.TYPE_CODE_FLAGS
24224 @item gdb.TYPE_CODE_FLAGS
24225 A bit flags type, used for things such as status registers.
24227 @findex TYPE_CODE_FUNC
24228 @findex gdb.TYPE_CODE_FUNC
24229 @item gdb.TYPE_CODE_FUNC
24230 The type is a function.
24232 @findex TYPE_CODE_INT
24233 @findex gdb.TYPE_CODE_INT
24234 @item gdb.TYPE_CODE_INT
24235 The type is an integer type.
24237 @findex TYPE_CODE_FLT
24238 @findex gdb.TYPE_CODE_FLT
24239 @item gdb.TYPE_CODE_FLT
24240 A floating point type.
24242 @findex TYPE_CODE_VOID
24243 @findex gdb.TYPE_CODE_VOID
24244 @item gdb.TYPE_CODE_VOID
24245 The special type @code{void}.
24247 @findex TYPE_CODE_SET
24248 @findex gdb.TYPE_CODE_SET
24249 @item gdb.TYPE_CODE_SET
24252 @findex TYPE_CODE_RANGE
24253 @findex gdb.TYPE_CODE_RANGE
24254 @item gdb.TYPE_CODE_RANGE
24255 A range type, that is, an integer type with bounds.
24257 @findex TYPE_CODE_STRING
24258 @findex gdb.TYPE_CODE_STRING
24259 @item gdb.TYPE_CODE_STRING
24260 A string type. Note that this is only used for certain languages with
24261 language-defined string types; C strings are not represented this way.
24263 @findex TYPE_CODE_BITSTRING
24264 @findex gdb.TYPE_CODE_BITSTRING
24265 @item gdb.TYPE_CODE_BITSTRING
24266 A string of bits. It is deprecated.
24268 @findex TYPE_CODE_ERROR
24269 @findex gdb.TYPE_CODE_ERROR
24270 @item gdb.TYPE_CODE_ERROR
24271 An unknown or erroneous type.
24273 @findex TYPE_CODE_METHOD
24274 @findex gdb.TYPE_CODE_METHOD
24275 @item gdb.TYPE_CODE_METHOD
24276 A method type, as found in C@t{++} or Java.
24278 @findex TYPE_CODE_METHODPTR
24279 @findex gdb.TYPE_CODE_METHODPTR
24280 @item gdb.TYPE_CODE_METHODPTR
24281 A pointer-to-member-function.
24283 @findex TYPE_CODE_MEMBERPTR
24284 @findex gdb.TYPE_CODE_MEMBERPTR
24285 @item gdb.TYPE_CODE_MEMBERPTR
24286 A pointer-to-member.
24288 @findex TYPE_CODE_REF
24289 @findex gdb.TYPE_CODE_REF
24290 @item gdb.TYPE_CODE_REF
24293 @findex TYPE_CODE_CHAR
24294 @findex gdb.TYPE_CODE_CHAR
24295 @item gdb.TYPE_CODE_CHAR
24298 @findex TYPE_CODE_BOOL
24299 @findex gdb.TYPE_CODE_BOOL
24300 @item gdb.TYPE_CODE_BOOL
24303 @findex TYPE_CODE_COMPLEX
24304 @findex gdb.TYPE_CODE_COMPLEX
24305 @item gdb.TYPE_CODE_COMPLEX
24306 A complex float type.
24308 @findex TYPE_CODE_TYPEDEF
24309 @findex gdb.TYPE_CODE_TYPEDEF
24310 @item gdb.TYPE_CODE_TYPEDEF
24311 A typedef to some other type.
24313 @findex TYPE_CODE_NAMESPACE
24314 @findex gdb.TYPE_CODE_NAMESPACE
24315 @item gdb.TYPE_CODE_NAMESPACE
24316 A C@t{++} namespace.
24318 @findex TYPE_CODE_DECFLOAT
24319 @findex gdb.TYPE_CODE_DECFLOAT
24320 @item gdb.TYPE_CODE_DECFLOAT
24321 A decimal floating point type.
24323 @findex TYPE_CODE_INTERNAL_FUNCTION
24324 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24325 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24326 A function internal to @value{GDBN}. This is the type used to represent
24327 convenience functions.
24330 Further support for types is provided in the @code{gdb.types}
24331 Python module (@pxref{gdb.types}).
24333 @node Pretty Printing API
24334 @subsubsection Pretty Printing API
24336 An example output is provided (@pxref{Pretty Printing}).
24338 A pretty-printer is just an object that holds a value and implements a
24339 specific interface, defined here.
24341 @defun pretty_printer.children (self)
24342 @value{GDBN} will call this method on a pretty-printer to compute the
24343 children of the pretty-printer's value.
24345 This method must return an object conforming to the Python iterator
24346 protocol. Each item returned by the iterator must be a tuple holding
24347 two elements. The first element is the ``name'' of the child; the
24348 second element is the child's value. The value can be any Python
24349 object which is convertible to a @value{GDBN} value.
24351 This method is optional. If it does not exist, @value{GDBN} will act
24352 as though the value has no children.
24355 @defun pretty_printer.display_hint (self)
24356 The CLI may call this method and use its result to change the
24357 formatting of a value. The result will also be supplied to an MI
24358 consumer as a @samp{displayhint} attribute of the variable being
24361 This method is optional. If it does exist, this method must return a
24364 Some display hints are predefined by @value{GDBN}:
24368 Indicate that the object being printed is ``array-like''. The CLI
24369 uses this to respect parameters such as @code{set print elements} and
24370 @code{set print array}.
24373 Indicate that the object being printed is ``map-like'', and that the
24374 children of this value can be assumed to alternate between keys and
24378 Indicate that the object being printed is ``string-like''. If the
24379 printer's @code{to_string} method returns a Python string of some
24380 kind, then @value{GDBN} will call its internal language-specific
24381 string-printing function to format the string. For the CLI this means
24382 adding quotation marks, possibly escaping some characters, respecting
24383 @code{set print elements}, and the like.
24387 @defun pretty_printer.to_string (self)
24388 @value{GDBN} will call this method to display the string
24389 representation of the value passed to the object's constructor.
24391 When printing from the CLI, if the @code{to_string} method exists,
24392 then @value{GDBN} will prepend its result to the values returned by
24393 @code{children}. Exactly how this formatting is done is dependent on
24394 the display hint, and may change as more hints are added. Also,
24395 depending on the print settings (@pxref{Print Settings}), the CLI may
24396 print just the result of @code{to_string} in a stack trace, omitting
24397 the result of @code{children}.
24399 If this method returns a string, it is printed verbatim.
24401 Otherwise, if this method returns an instance of @code{gdb.Value},
24402 then @value{GDBN} prints this value. This may result in a call to
24403 another pretty-printer.
24405 If instead the method returns a Python value which is convertible to a
24406 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24407 the resulting value. Again, this may result in a call to another
24408 pretty-printer. Python scalars (integers, floats, and booleans) and
24409 strings are convertible to @code{gdb.Value}; other types are not.
24411 Finally, if this method returns @code{None} then no further operations
24412 are peformed in this method and nothing is printed.
24414 If the result is not one of these types, an exception is raised.
24417 @value{GDBN} provides a function which can be used to look up the
24418 default pretty-printer for a @code{gdb.Value}:
24420 @findex gdb.default_visualizer
24421 @defun gdb.default_visualizer (value)
24422 This function takes a @code{gdb.Value} object as an argument. If a
24423 pretty-printer for this value exists, then it is returned. If no such
24424 printer exists, then this returns @code{None}.
24427 @node Selecting Pretty-Printers
24428 @subsubsection Selecting Pretty-Printers
24430 The Python list @code{gdb.pretty_printers} contains an array of
24431 functions or callable objects that have been registered via addition
24432 as a pretty-printer. Printers in this list are called @code{global}
24433 printers, they're available when debugging all inferiors.
24434 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24435 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24438 Each function on these lists is passed a single @code{gdb.Value}
24439 argument and should return a pretty-printer object conforming to the
24440 interface definition above (@pxref{Pretty Printing API}). If a function
24441 cannot create a pretty-printer for the value, it should return
24444 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24445 @code{gdb.Objfile} in the current program space and iteratively calls
24446 each enabled lookup routine in the list for that @code{gdb.Objfile}
24447 until it receives a pretty-printer object.
24448 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24449 searches the pretty-printer list of the current program space,
24450 calling each enabled function until an object is returned.
24451 After these lists have been exhausted, it tries the global
24452 @code{gdb.pretty_printers} list, again calling each enabled function until an
24453 object is returned.
24455 The order in which the objfiles are searched is not specified. For a
24456 given list, functions are always invoked from the head of the list,
24457 and iterated over sequentially until the end of the list, or a printer
24458 object is returned.
24460 For various reasons a pretty-printer may not work.
24461 For example, the underlying data structure may have changed and
24462 the pretty-printer is out of date.
24464 The consequences of a broken pretty-printer are severe enough that
24465 @value{GDBN} provides support for enabling and disabling individual
24466 printers. For example, if @code{print frame-arguments} is on,
24467 a backtrace can become highly illegible if any argument is printed
24468 with a broken printer.
24470 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24471 attribute to the registered function or callable object. If this attribute
24472 is present and its value is @code{False}, the printer is disabled, otherwise
24473 the printer is enabled.
24475 @node Writing a Pretty-Printer
24476 @subsubsection Writing a Pretty-Printer
24477 @cindex writing a pretty-printer
24479 A pretty-printer consists of two parts: a lookup function to detect
24480 if the type is supported, and the printer itself.
24482 Here is an example showing how a @code{std::string} printer might be
24483 written. @xref{Pretty Printing API}, for details on the API this class
24487 class StdStringPrinter(object):
24488 "Print a std::string"
24490 def __init__(self, val):
24493 def to_string(self):
24494 return self.val['_M_dataplus']['_M_p']
24496 def display_hint(self):
24500 And here is an example showing how a lookup function for the printer
24501 example above might be written.
24504 def str_lookup_function(val):
24505 lookup_tag = val.type.tag
24506 if lookup_tag == None:
24508 regex = re.compile("^std::basic_string<char,.*>$")
24509 if regex.match(lookup_tag):
24510 return StdStringPrinter(val)
24514 The example lookup function extracts the value's type, and attempts to
24515 match it to a type that it can pretty-print. If it is a type the
24516 printer can pretty-print, it will return a printer object. If not, it
24517 returns @code{None}.
24519 We recommend that you put your core pretty-printers into a Python
24520 package. If your pretty-printers are for use with a library, we
24521 further recommend embedding a version number into the package name.
24522 This practice will enable @value{GDBN} to load multiple versions of
24523 your pretty-printers at the same time, because they will have
24526 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24527 can be evaluated multiple times without changing its meaning. An
24528 ideal auto-load file will consist solely of @code{import}s of your
24529 printer modules, followed by a call to a register pretty-printers with
24530 the current objfile.
24532 Taken as a whole, this approach will scale nicely to multiple
24533 inferiors, each potentially using a different library version.
24534 Embedding a version number in the Python package name will ensure that
24535 @value{GDBN} is able to load both sets of printers simultaneously.
24536 Then, because the search for pretty-printers is done by objfile, and
24537 because your auto-loaded code took care to register your library's
24538 printers with a specific objfile, @value{GDBN} will find the correct
24539 printers for the specific version of the library used by each
24542 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24543 this code might appear in @code{gdb.libstdcxx.v6}:
24546 def register_printers(objfile):
24547 objfile.pretty_printers.append(str_lookup_function)
24551 And then the corresponding contents of the auto-load file would be:
24554 import gdb.libstdcxx.v6
24555 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24558 The previous example illustrates a basic pretty-printer.
24559 There are a few things that can be improved on.
24560 The printer doesn't have a name, making it hard to identify in a
24561 list of installed printers. The lookup function has a name, but
24562 lookup functions can have arbitrary, even identical, names.
24564 Second, the printer only handles one type, whereas a library typically has
24565 several types. One could install a lookup function for each desired type
24566 in the library, but one could also have a single lookup function recognize
24567 several types. The latter is the conventional way this is handled.
24568 If a pretty-printer can handle multiple data types, then its
24569 @dfn{subprinters} are the printers for the individual data types.
24571 The @code{gdb.printing} module provides a formal way of solving these
24572 problems (@pxref{gdb.printing}).
24573 Here is another example that handles multiple types.
24575 These are the types we are going to pretty-print:
24578 struct foo @{ int a, b; @};
24579 struct bar @{ struct foo x, y; @};
24582 Here are the printers:
24586 """Print a foo object."""
24588 def __init__(self, val):
24591 def to_string(self):
24592 return ("a=<" + str(self.val["a"]) +
24593 "> b=<" + str(self.val["b"]) + ">")
24596 """Print a bar object."""
24598 def __init__(self, val):
24601 def to_string(self):
24602 return ("x=<" + str(self.val["x"]) +
24603 "> y=<" + str(self.val["y"]) + ">")
24606 This example doesn't need a lookup function, that is handled by the
24607 @code{gdb.printing} module. Instead a function is provided to build up
24608 the object that handles the lookup.
24611 import gdb.printing
24613 def build_pretty_printer():
24614 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24616 pp.add_printer('foo', '^foo$', fooPrinter)
24617 pp.add_printer('bar', '^bar$', barPrinter)
24621 And here is the autoload support:
24624 import gdb.printing
24626 gdb.printing.register_pretty_printer(
24627 gdb.current_objfile(),
24628 my_library.build_pretty_printer())
24631 Finally, when this printer is loaded into @value{GDBN}, here is the
24632 corresponding output of @samp{info pretty-printer}:
24635 (gdb) info pretty-printer
24642 @node Type Printing API
24643 @subsubsection Type Printing API
24644 @cindex type printing API for Python
24646 @value{GDBN} provides a way for Python code to customize type display.
24647 This is mainly useful for substituting canonical typedef names for
24650 @cindex type printer
24651 A @dfn{type printer} is just a Python object conforming to a certain
24652 protocol. A simple base class implementing the protocol is provided;
24653 see @ref{gdb.types}. A type printer must supply at least:
24655 @defivar type_printer enabled
24656 A boolean which is True if the printer is enabled, and False
24657 otherwise. This is manipulated by the @code{enable type-printer}
24658 and @code{disable type-printer} commands.
24661 @defivar type_printer name
24662 The name of the type printer. This must be a string. This is used by
24663 the @code{enable type-printer} and @code{disable type-printer}
24667 @defmethod type_printer instantiate (self)
24668 This is called by @value{GDBN} at the start of type-printing. It is
24669 only called if the type printer is enabled. This method must return a
24670 new object that supplies a @code{recognize} method, as described below.
24674 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24675 will compute a list of type recognizers. This is done by iterating
24676 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24677 followed by the per-progspace type printers (@pxref{Progspaces In
24678 Python}), and finally the global type printers.
24680 @value{GDBN} will call the @code{instantiate} method of each enabled
24681 type printer. If this method returns @code{None}, then the result is
24682 ignored; otherwise, it is appended to the list of recognizers.
24684 Then, when @value{GDBN} is going to display a type name, it iterates
24685 over the list of recognizers. For each one, it calls the recognition
24686 function, stopping if the function returns a non-@code{None} value.
24687 The recognition function is defined as:
24689 @defmethod type_recognizer recognize (self, type)
24690 If @var{type} is not recognized, return @code{None}. Otherwise,
24691 return a string which is to be printed as the name of @var{type}.
24692 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24696 @value{GDBN} uses this two-pass approach so that type printers can
24697 efficiently cache information without holding on to it too long. For
24698 example, it can be convenient to look up type information in a type
24699 printer and hold it for a recognizer's lifetime; if a single pass were
24700 done then type printers would have to make use of the event system in
24701 order to avoid holding information that could become stale as the
24704 @node Frame Filter API
24705 @subsubsection Filtering Frames.
24706 @cindex frame filters api
24708 Frame filters are Python objects that manipulate the visibility of a
24709 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24712 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24713 commands (@pxref{GDB/MI}), those that return a collection of frames
24714 are affected. The commands that work with frame filters are:
24716 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
24717 @code{-stack-list-frames}
24718 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
24719 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
24720 -stack-list-variables command}), @code{-stack-list-arguments}
24721 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
24722 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
24723 -stack-list-locals command}).
24725 A frame filter works by taking an iterator as an argument, applying
24726 actions to the contents of that iterator, and returning another
24727 iterator (or, possibly, the same iterator it was provided in the case
24728 where the filter does not perform any operations). Typically, frame
24729 filters utilize tools such as the Python's @code{itertools} module to
24730 work with and create new iterators from the source iterator.
24731 Regardless of how a filter chooses to apply actions, it must not alter
24732 the underlying @value{GDBN} frame or frames, or attempt to alter the
24733 call-stack within @value{GDBN}. This preserves data integrity within
24734 @value{GDBN}. Frame filters are executed on a priority basis and care
24735 should be taken that some frame filters may have been executed before,
24736 and that some frame filters will be executed after.
24738 An important consideration when designing frame filters, and well
24739 worth reflecting upon, is that frame filters should avoid unwinding
24740 the call stack if possible. Some stacks can run very deep, into the
24741 tens of thousands in some cases. To search every frame when a frame
24742 filter executes may be too expensive at that step. The frame filter
24743 cannot know how many frames it has to iterate over, and it may have to
24744 iterate through them all. This ends up duplicating effort as
24745 @value{GDBN} performs this iteration when it prints the frames. If
24746 the filter can defer unwinding frames until frame decorators are
24747 executed, after the last filter has executed, it should. @xref{Frame
24748 Decorator API}, for more information on decorators. Also, there are
24749 examples for both frame decorators and filters in later chapters.
24750 @xref{Writing a Frame Filter}, for more information.
24752 The Python dictionary @code{gdb.frame_filters} contains key/object
24753 pairings that comprise a frame filter. Frame filters in this
24754 dictionary are called @code{global} frame filters, and they are
24755 available when debugging all inferiors. These frame filters must
24756 register with the dictionary directly. In addition to the
24757 @code{global} dictionary, there are other dictionaries that are loaded
24758 with different inferiors via auto-loading (@pxref{Python
24759 Auto-loading}). The two other areas where frame filter dictionaries
24760 can be found are: @code{gdb.Progspace} which contains a
24761 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
24762 object which also contains a @code{frame_filters} dictionary
24765 When a command is executed from @value{GDBN} that is compatible with
24766 frame filters, @value{GDBN} combines the @code{global},
24767 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
24768 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
24769 several frames, and thus several object files, might be in use.
24770 @value{GDBN} then prunes any frame filter whose @code{enabled}
24771 attribute is @code{False}. This pruned list is then sorted according
24772 to the @code{priority} attribute in each filter.
24774 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
24775 creates an iterator which wraps each frame in the call stack in a
24776 @code{FrameDecorator} object, and calls each filter in order. The
24777 output from the previous filter will always be the input to the next
24780 Frame filters have a mandatory interface which each frame filter must
24781 implement, defined here:
24783 @defun FrameFilter.filter (iterator)
24784 @value{GDBN} will call this method on a frame filter when it has
24785 reached the order in the priority list for that filter.
24787 For example, if there are four frame filters:
24798 The order that the frame filters will be called is:
24801 Filter3 -> Filter2 -> Filter1 -> Filter4
24804 Note that the output from @code{Filter3} is passed to the input of
24805 @code{Filter2}, and so on.
24807 This @code{filter} method is passed a Python iterator. This iterator
24808 contains a sequence of frame decorators that wrap each
24809 @code{gdb.Frame}, or a frame decorator that wraps another frame
24810 decorator. The first filter that is executed in the sequence of frame
24811 filters will receive an iterator entirely comprised of default
24812 @code{FrameDecorator} objects. However, after each frame filter is
24813 executed, the previous frame filter may have wrapped some or all of
24814 the frame decorators with their own frame decorator. As frame
24815 decorators must also conform to a mandatory interface, these
24816 decorators can be assumed to act in a uniform manner (@pxref{Frame
24819 This method must return an object conforming to the Python iterator
24820 protocol. Each item in the iterator must be an object conforming to
24821 the frame decorator interface. If a frame filter does not wish to
24822 perform any operations on this iterator, it should return that
24823 iterator untouched.
24825 This method is not optional. If it does not exist, @value{GDBN} will
24826 raise and print an error.
24829 @defvar FrameFilter.name
24830 The @code{name} attribute must be Python string which contains the
24831 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
24832 Management}). This attribute may contain any combination of letters
24833 or numbers. Care should be taken to ensure that it is unique. This
24834 attribute is mandatory.
24837 @defvar FrameFilter.enabled
24838 The @code{enabled} attribute must be Python boolean. This attribute
24839 indicates to @value{GDBN} whether the frame filter is enabled, and
24840 should be considered when frame filters are executed. If
24841 @code{enabled} is @code{True}, then the frame filter will be executed
24842 when any of the backtrace commands detailed earlier in this chapter
24843 are executed. If @code{enabled} is @code{False}, then the frame
24844 filter will not be executed. This attribute is mandatory.
24847 @defvar FrameFilter.priority
24848 The @code{priority} attribute must be Python integer. This attribute
24849 controls the order of execution in relation to other frame filters.
24850 There are no imposed limits on the range of @code{priority} other than
24851 it must be a valid integer. The higher the @code{priority} attribute,
24852 the sooner the frame filter will be executed in relation to other
24853 frame filters. Although @code{priority} can be negative, it is
24854 recommended practice to assume zero is the lowest priority that a
24855 frame filter can be assigned. Frame filters that have the same
24856 priority are executed in unsorted order in that priority slot. This
24857 attribute is mandatory.
24860 @node Frame Decorator API
24861 @subsubsection Decorating Frames.
24862 @cindex frame decorator api
24864 Frame decorators are sister objects to frame filters (@pxref{Frame
24865 Filter API}). Frame decorators are applied by a frame filter and can
24866 only be used in conjunction with frame filters.
24868 The purpose of a frame decorator is to customize the printed content
24869 of each @code{gdb.Frame} in commands where frame filters are executed.
24870 This concept is called decorating a frame. Frame decorators decorate
24871 a @code{gdb.Frame} with Python code contained within each API call.
24872 This separates the actual data contained in a @code{gdb.Frame} from
24873 the decorated data produced by a frame decorator. This abstraction is
24874 necessary to maintain integrity of the data contained in each
24877 Frame decorators have a mandatory interface, defined below.
24879 @value{GDBN} already contains a frame decorator called
24880 @code{FrameDecorator}. This contains substantial amounts of
24881 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
24882 recommended that other frame decorators inherit and extend this
24883 object, and only to override the methods needed.
24885 @defun FrameDecorator.elided (self)
24887 The @code{elided} method groups frames together in a hierarchical
24888 system. An example would be an interpreter, where multiple low-level
24889 frames make up a single call in the interpreted language. In this
24890 example, the frame filter would elide the low-level frames and present
24891 a single high-level frame, representing the call in the interpreted
24892 language, to the user.
24894 The @code{elided} function must return an iterable and this iterable
24895 must contain the frames that are being elided wrapped in a suitable
24896 frame decorator. If no frames are being elided this function may
24897 return an empty iterable, or @code{None}. Elided frames are indented
24898 from normal frames in a @code{CLI} backtrace, or in the case of
24899 @code{GDB/MI}, are placed in the @code{children} field of the eliding
24902 It is the frame filter's task to also filter out the elided frames from
24903 the source iterator. This will avoid printing the frame twice.
24906 @defun FrameDecorator.function (self)
24908 This method returns the name of the function in the frame that is to
24911 This method must return a Python string describing the function, or
24914 If this function returns @code{None}, @value{GDBN} will not print any
24915 data for this field.
24918 @defun FrameDecorator.address (self)
24920 This method returns the address of the frame that is to be printed.
24922 This method must return a Python numeric integer type of sufficient
24923 size to describe the address of the frame, or @code{None}.
24925 If this function returns a @code{None}, @value{GDBN} will not print
24926 any data for this field.
24929 @defun FrameDecorator.filename (self)
24931 This method returns the filename and path associated with this frame.
24933 This method must return a Python string containing the filename and
24934 the path to the object file backing the frame, or @code{None}.
24936 If this function returns a @code{None}, @value{GDBN} will not print
24937 any data for this field.
24940 @defun FrameDecorator.line (self):
24942 This method returns the line number associated with the current
24943 position within the function addressed by this frame.
24945 This method must return a Python integer type, or @code{None}.
24947 If this function returns a @code{None}, @value{GDBN} will not print
24948 any data for this field.
24951 @defun FrameDecorator.frame_args (self)
24952 @anchor{frame_args}
24954 This method must return an iterable, or @code{None}. Returning an
24955 empty iterable, or @code{None} means frame arguments will not be
24956 printed for this frame. This iterable must contain objects that
24957 implement two methods, described here.
24959 This object must implement a @code{argument} method which takes a
24960 single @code{self} parameter and must return a @code{gdb.Symbol}
24961 (@pxref{Symbols In Python}), or a Python string. The object must also
24962 implement a @code{value} method which takes a single @code{self}
24963 parameter and must return a @code{gdb.Value} (@pxref{Values From
24964 Inferior}), a Python value, or @code{None}. If the @code{value}
24965 method returns @code{None}, and the @code{argument} method returns a
24966 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
24967 the @code{gdb.Symbol} automatically.
24972 class SymValueWrapper():
24974 def __init__(self, symbol, value):
24984 class SomeFrameDecorator()
24987 def frame_args(self):
24990 block = self.inferior_frame.block()
24994 # Iterate over all symbols in a block. Only add
24995 # symbols that are arguments.
24997 if not sym.is_argument:
24999 args.append(SymValueWrapper(sym,None))
25001 # Add example synthetic argument.
25002 args.append(SymValueWrapper(``foo'', 42))
25008 @defun FrameDecorator.frame_locals (self)
25010 This method must return an iterable or @code{None}. Returning an
25011 empty iterable, or @code{None} means frame local arguments will not be
25012 printed for this frame.
25014 The object interface, the description of the various strategies for
25015 reading frame locals, and the example are largely similar to those
25016 described in the @code{frame_args} function, (@pxref{frame_args,,The
25017 frame filter frame_args function}). Below is a modified example:
25020 class SomeFrameDecorator()
25023 def frame_locals(self):
25026 block = self.inferior_frame.block()
25030 # Iterate over all symbols in a block. Add all
25031 # symbols, except arguments.
25033 if sym.is_argument:
25035 vars.append(SymValueWrapper(sym,None))
25037 # Add an example of a synthetic local variable.
25038 vars.append(SymValueWrapper(``bar'', 99))
25044 @defun FrameDecorator.inferior_frame (self):
25046 This method must return the underlying @code{gdb.Frame} that this
25047 frame decorator is decorating. @value{GDBN} requires the underlying
25048 frame for internal frame information to determine how to print certain
25049 values when printing a frame.
25052 @node Writing a Frame Filter
25053 @subsubsection Writing a Frame Filter
25054 @cindex writing a frame filter
25056 There are three basic elements that a frame filter must implement: it
25057 must correctly implement the documented interface (@pxref{Frame Filter
25058 API}), it must register itself with @value{GDBN}, and finally, it must
25059 decide if it is to work on the data provided by @value{GDBN}. In all
25060 cases, whether it works on the iterator or not, each frame filter must
25061 return an iterator. A bare-bones frame filter follows the pattern in
25062 the following example.
25067 class FrameFilter():
25069 def __init__(self):
25070 # Frame filter attribute creation.
25072 # 'name' is the name of the filter that GDB will display.
25074 # 'priority' is the priority of the filter relative to other
25077 # 'enabled' is a boolean that indicates whether this filter is
25078 # enabled and should be executed.
25081 self.priority = 100
25082 self.enabled = True
25084 # Register this frame filter with the global frame_filters
25086 gdb.frame_filters[self.name] = self
25088 def filter(self, frame_iter):
25089 # Just return the iterator.
25093 The frame filter in the example above implements the three
25094 requirements for all frame filters. It implements the API, self
25095 registers, and makes a decision on the iterator (in this case, it just
25096 returns the iterator untouched).
25098 The first step is attribute creation and assignment, and as shown in
25099 the comments the filter assigns the following attributes: @code{name},
25100 @code{priority} and whether the filter should be enabled with the
25101 @code{enabled} attribute.
25103 The second step is registering the frame filter with the dictionary or
25104 dictionaries that the frame filter has interest in. As shown in the
25105 comments, this filter just registers itself with the global dictionary
25106 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25107 is a dictionary that is initialized in the @code{gdb} module when
25108 @value{GDBN} starts. What dictionary a filter registers with is an
25109 important consideration. Generally, if a filter is specific to a set
25110 of code, it should be registered either in the @code{objfile} or
25111 @code{progspace} dictionaries as they are specific to the program
25112 currently loaded in @value{GDBN}. The global dictionary is always
25113 present in @value{GDBN} and is never unloaded. Any filters registered
25114 with the global dictionary will exist until @value{GDBN} exits. To
25115 avoid filters that may conflict, it is generally better to register
25116 frame filters against the dictionaries that more closely align with
25117 the usage of the filter currently in question. @xref{Python
25118 Auto-loading}, for further information on auto-loading Python scripts.
25120 @value{GDBN} takes a hands-off approach to frame filter registration,
25121 therefore it is the frame filter's responsibility to ensure
25122 registration has occurred, and that any exceptions are handled
25123 appropriately. In particular, you may wish to handle exceptions
25124 relating to Python dictionary key uniqueness. It is mandatory that
25125 the dictionary key is the same as frame filter's @code{name}
25126 attribute. When a user manages frame filters (@pxref{Frame Filter
25127 Management}), the names @value{GDBN} will display are those contained
25128 in the @code{name} attribute.
25130 The final step of this example is the implementation of the
25131 @code{filter} method. As shown in the example comments, we define the
25132 @code{filter} method and note that the method must take an iterator,
25133 and also must return an iterator. In this bare-bones example, the
25134 frame filter is not very useful as it just returns the iterator
25135 untouched. However this is a valid operation for frame filters that
25136 have the @code{enabled} attribute set, but decide not to operate on
25139 In the next example, the frame filter operates on all frames and
25140 utilizes a frame decorator to perform some work on the frames.
25141 @xref{Frame Decorator API}, for further information on the frame
25142 decorator interface.
25144 This example works on inlined frames. It highlights frames which are
25145 inlined by tagging them with an ``[inlined]'' tag. By applying a
25146 frame decorator to all frames with the Python @code{itertools imap}
25147 method, the example defers actions to the frame decorator. Frame
25148 decorators are only processed when @value{GDBN} prints the backtrace.
25150 This introduces a new decision making topic: whether to perform
25151 decision making operations at the filtering step, or at the printing
25152 step. In this example's approach, it does not perform any filtering
25153 decisions at the filtering step beyond mapping a frame decorator to
25154 each frame. This allows the actual decision making to be performed
25155 when each frame is printed. This is an important consideration, and
25156 well worth reflecting upon when designing a frame filter. An issue
25157 that frame filters should avoid is unwinding the stack if possible.
25158 Some stacks can run very deep, into the tens of thousands in some
25159 cases. To search every frame to determine if it is inlined ahead of
25160 time may be too expensive at the filtering step. The frame filter
25161 cannot know how many frames it has to iterate over, and it would have
25162 to iterate through them all. This ends up duplicating effort as
25163 @value{GDBN} performs this iteration when it prints the frames.
25165 In this example decision making can be deferred to the printing step.
25166 As each frame is printed, the frame decorator can examine each frame
25167 in turn when @value{GDBN} iterates. From a performance viewpoint,
25168 this is the most appropriate decision to make as it avoids duplicating
25169 the effort that the printing step would undertake anyway. Also, if
25170 there are many frame filters unwinding the stack during filtering, it
25171 can substantially delay the printing of the backtrace which will
25172 result in large memory usage, and a poor user experience.
25175 class InlineFilter():
25177 def __init__(self):
25178 self.name = "InlinedFrameFilter"
25179 self.priority = 100
25180 self.enabled = True
25181 gdb.frame_filters[self.name] = self
25183 def filter(self, frame_iter):
25184 frame_iter = itertools.imap(InlinedFrameDecorator,
25189 This frame filter is somewhat similar to the earlier example, except
25190 that the @code{filter} method applies a frame decorator object called
25191 @code{InlinedFrameDecorator} to each element in the iterator. The
25192 @code{imap} Python method is light-weight. It does not proactively
25193 iterate over the iterator, but rather creates a new iterator which
25194 wraps the existing one.
25196 Below is the frame decorator for this example.
25199 class InlinedFrameDecorator(FrameDecorator):
25201 def __init__(self, fobj):
25202 super(InlinedFrameDecorator, self).__init__(fobj)
25204 def function(self):
25205 frame = fobj.inferior_frame()
25206 name = str(frame.name())
25208 if frame.type() == gdb.INLINE_FRAME:
25209 name = name + " [inlined]"
25214 This frame decorator only defines and overrides the @code{function}
25215 method. It lets the supplied @code{FrameDecorator}, which is shipped
25216 with @value{GDBN}, perform the other work associated with printing
25219 The combination of these two objects create this output from a
25223 #0 0x004004e0 in bar () at inline.c:11
25224 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25225 #2 0x00400566 in main () at inline.c:31
25228 So in the case of this example, a frame decorator is applied to all
25229 frames, regardless of whether they may be inlined or not. As
25230 @value{GDBN} iterates over the iterator produced by the frame filters,
25231 @value{GDBN} executes each frame decorator which then makes a decision
25232 on what to print in the @code{function} callback. Using a strategy
25233 like this is a way to defer decisions on the frame content to printing
25236 @subheading Eliding Frames
25238 It might be that the above example is not desirable for representing
25239 inlined frames, and a hierarchical approach may be preferred. If we
25240 want to hierarchically represent frames, the @code{elided} frame
25241 decorator interface might be preferable.
25243 This example approaches the issue with the @code{elided} method. This
25244 example is quite long, but very simplistic. It is out-of-scope for
25245 this section to write a complete example that comprehensively covers
25246 all approaches of finding and printing inlined frames. However, this
25247 example illustrates the approach an author might use.
25249 This example comprises of three sections.
25252 class InlineFrameFilter():
25254 def __init__(self):
25255 self.name = "InlinedFrameFilter"
25256 self.priority = 100
25257 self.enabled = True
25258 gdb.frame_filters[self.name] = self
25260 def filter(self, frame_iter):
25261 return ElidingInlineIterator(frame_iter)
25264 This frame filter is very similar to the other examples. The only
25265 difference is this frame filter is wrapping the iterator provided to
25266 it (@code{frame_iter}) with a custom iterator called
25267 @code{ElidingInlineIterator}. This again defers actions to when
25268 @value{GDBN} prints the backtrace, as the iterator is not traversed
25271 The iterator for this example is as follows. It is in this section of
25272 the example where decisions are made on the content of the backtrace.
25275 class ElidingInlineIterator:
25276 def __init__(self, ii):
25277 self.input_iterator = ii
25279 def __iter__(self):
25283 frame = next(self.input_iterator)
25285 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25289 eliding_frame = next(self.input_iterator)
25290 except StopIteration:
25292 return ElidingFrameDecorator(eliding_frame, [frame])
25295 This iterator implements the Python iterator protocol. When the
25296 @code{next} function is called (when @value{GDBN} prints each frame),
25297 the iterator checks if this frame decorator, @code{frame}, is wrapping
25298 an inlined frame. If it is not, it returns the existing frame decorator
25299 untouched. If it is wrapping an inlined frame, it assumes that the
25300 inlined frame was contained within the next oldest frame,
25301 @code{eliding_frame}, which it fetches. It then creates and returns a
25302 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25303 elided frame, and the eliding frame.
25306 class ElidingInlineDecorator(FrameDecorator):
25308 def __init__(self, frame, elided_frames):
25309 super(ElidingInlineDecorator, self).__init__(frame)
25311 self.elided_frames = elided_frames
25314 return iter(self.elided_frames)
25317 This frame decorator overrides one function and returns the inlined
25318 frame in the @code{elided} method. As before it lets
25319 @code{FrameDecorator} do the rest of the work involved in printing
25320 this frame. This produces the following output.
25323 #0 0x004004e0 in bar () at inline.c:11
25324 #2 0x00400529 in main () at inline.c:25
25325 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25328 In that output, @code{max} which has been inlined into @code{main} is
25329 printed hierarchically. Another approach would be to combine the
25330 @code{function} method, and the @code{elided} method to both print a
25331 marker in the inlined frame, and also show the hierarchical
25334 @node Inferiors In Python
25335 @subsubsection Inferiors In Python
25336 @cindex inferiors in Python
25338 @findex gdb.Inferior
25339 Programs which are being run under @value{GDBN} are called inferiors
25340 (@pxref{Inferiors and Programs}). Python scripts can access
25341 information about and manipulate inferiors controlled by @value{GDBN}
25342 via objects of the @code{gdb.Inferior} class.
25344 The following inferior-related functions are available in the @code{gdb}
25347 @defun gdb.inferiors ()
25348 Return a tuple containing all inferior objects.
25351 @defun gdb.selected_inferior ()
25352 Return an object representing the current inferior.
25355 A @code{gdb.Inferior} object has the following attributes:
25357 @defvar Inferior.num
25358 ID of inferior, as assigned by GDB.
25361 @defvar Inferior.pid
25362 Process ID of the inferior, as assigned by the underlying operating
25366 @defvar Inferior.was_attached
25367 Boolean signaling whether the inferior was created using `attach', or
25368 started by @value{GDBN} itself.
25371 A @code{gdb.Inferior} object has the following methods:
25373 @defun Inferior.is_valid ()
25374 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25375 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25376 if the inferior no longer exists within @value{GDBN}. All other
25377 @code{gdb.Inferior} methods will throw an exception if it is invalid
25378 at the time the method is called.
25381 @defun Inferior.threads ()
25382 This method returns a tuple holding all the threads which are valid
25383 when it is called. If there are no valid threads, the method will
25384 return an empty tuple.
25387 @findex Inferior.read_memory
25388 @defun Inferior.read_memory (address, length)
25389 Read @var{length} bytes of memory from the inferior, starting at
25390 @var{address}. Returns a buffer object, which behaves much like an array
25391 or a string. It can be modified and given to the
25392 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25393 value is a @code{memoryview} object.
25396 @findex Inferior.write_memory
25397 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25398 Write the contents of @var{buffer} to the inferior, starting at
25399 @var{address}. The @var{buffer} parameter must be a Python object
25400 which supports the buffer protocol, i.e., a string, an array or the
25401 object returned from @code{Inferior.read_memory}. If given, @var{length}
25402 determines the number of bytes from @var{buffer} to be written.
25405 @findex gdb.search_memory
25406 @defun Inferior.search_memory (address, length, pattern)
25407 Search a region of the inferior memory starting at @var{address} with
25408 the given @var{length} using the search pattern supplied in
25409 @var{pattern}. The @var{pattern} parameter must be a Python object
25410 which supports the buffer protocol, i.e., a string, an array or the
25411 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25412 containing the address where the pattern was found, or @code{None} if
25413 the pattern could not be found.
25416 @node Events In Python
25417 @subsubsection Events In Python
25418 @cindex inferior events in Python
25420 @value{GDBN} provides a general event facility so that Python code can be
25421 notified of various state changes, particularly changes that occur in
25424 An @dfn{event} is just an object that describes some state change. The
25425 type of the object and its attributes will vary depending on the details
25426 of the change. All the existing events are described below.
25428 In order to be notified of an event, you must register an event handler
25429 with an @dfn{event registry}. An event registry is an object in the
25430 @code{gdb.events} module which dispatches particular events. A registry
25431 provides methods to register and unregister event handlers:
25433 @defun EventRegistry.connect (object)
25434 Add the given callable @var{object} to the registry. This object will be
25435 called when an event corresponding to this registry occurs.
25438 @defun EventRegistry.disconnect (object)
25439 Remove the given @var{object} from the registry. Once removed, the object
25440 will no longer receive notifications of events.
25443 Here is an example:
25446 def exit_handler (event):
25447 print "event type: exit"
25448 print "exit code: %d" % (event.exit_code)
25450 gdb.events.exited.connect (exit_handler)
25453 In the above example we connect our handler @code{exit_handler} to the
25454 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25455 called when the inferior exits. The argument @dfn{event} in this example is
25456 of type @code{gdb.ExitedEvent}. As you can see in the example the
25457 @code{ExitedEvent} object has an attribute which indicates the exit code of
25460 The following is a listing of the event registries that are available and
25461 details of the events they emit:
25466 Emits @code{gdb.ThreadEvent}.
25468 Some events can be thread specific when @value{GDBN} is running in non-stop
25469 mode. When represented in Python, these events all extend
25470 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25471 events which are emitted by this or other modules might extend this event.
25472 Examples of these events are @code{gdb.BreakpointEvent} and
25473 @code{gdb.ContinueEvent}.
25475 @defvar ThreadEvent.inferior_thread
25476 In non-stop mode this attribute will be set to the specific thread which was
25477 involved in the emitted event. Otherwise, it will be set to @code{None}.
25480 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25482 This event indicates that the inferior has been continued after a stop. For
25483 inherited attribute refer to @code{gdb.ThreadEvent} above.
25485 @item events.exited
25486 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25487 @code{events.ExitedEvent} has two attributes:
25488 @defvar ExitedEvent.exit_code
25489 An integer representing the exit code, if available, which the inferior
25490 has returned. (The exit code could be unavailable if, for example,
25491 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25492 the attribute does not exist.
25494 @defvar ExitedEvent inferior
25495 A reference to the inferior which triggered the @code{exited} event.
25499 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25501 Indicates that the inferior has stopped. All events emitted by this registry
25502 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25503 will indicate the stopped thread when @value{GDBN} is running in non-stop
25504 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25506 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25508 This event indicates that the inferior or one of its threads has received as
25509 signal. @code{gdb.SignalEvent} has the following attributes:
25511 @defvar SignalEvent.stop_signal
25512 A string representing the signal received by the inferior. A list of possible
25513 signal values can be obtained by running the command @code{info signals} in
25514 the @value{GDBN} command prompt.
25517 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25519 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25520 been hit, and has the following attributes:
25522 @defvar BreakpointEvent.breakpoints
25523 A sequence containing references to all the breakpoints (type
25524 @code{gdb.Breakpoint}) that were hit.
25525 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25527 @defvar BreakpointEvent.breakpoint
25528 A reference to the first breakpoint that was hit.
25529 This function is maintained for backward compatibility and is now deprecated
25530 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25533 @item events.new_objfile
25534 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25535 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25537 @defvar NewObjFileEvent.new_objfile
25538 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25539 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25544 @node Threads In Python
25545 @subsubsection Threads In Python
25546 @cindex threads in python
25548 @findex gdb.InferiorThread
25549 Python scripts can access information about, and manipulate inferior threads
25550 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25552 The following thread-related functions are available in the @code{gdb}
25555 @findex gdb.selected_thread
25556 @defun gdb.selected_thread ()
25557 This function returns the thread object for the selected thread. If there
25558 is no selected thread, this will return @code{None}.
25561 A @code{gdb.InferiorThread} object has the following attributes:
25563 @defvar InferiorThread.name
25564 The name of the thread. If the user specified a name using
25565 @code{thread name}, then this returns that name. Otherwise, if an
25566 OS-supplied name is available, then it is returned. Otherwise, this
25567 returns @code{None}.
25569 This attribute can be assigned to. The new value must be a string
25570 object, which sets the new name, or @code{None}, which removes any
25571 user-specified thread name.
25574 @defvar InferiorThread.num
25575 ID of the thread, as assigned by GDB.
25578 @defvar InferiorThread.ptid
25579 ID of the thread, as assigned by the operating system. This attribute is a
25580 tuple containing three integers. The first is the Process ID (PID); the second
25581 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25582 Either the LWPID or TID may be 0, which indicates that the operating system
25583 does not use that identifier.
25586 A @code{gdb.InferiorThread} object has the following methods:
25588 @defun InferiorThread.is_valid ()
25589 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25590 @code{False} if not. A @code{gdb.InferiorThread} object will become
25591 invalid if the thread exits, or the inferior that the thread belongs
25592 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25593 exception if it is invalid at the time the method is called.
25596 @defun InferiorThread.switch ()
25597 This changes @value{GDBN}'s currently selected thread to the one represented
25601 @defun InferiorThread.is_stopped ()
25602 Return a Boolean indicating whether the thread is stopped.
25605 @defun InferiorThread.is_running ()
25606 Return a Boolean indicating whether the thread is running.
25609 @defun InferiorThread.is_exited ()
25610 Return a Boolean indicating whether the thread is exited.
25613 @node Commands In Python
25614 @subsubsection Commands In Python
25616 @cindex commands in python
25617 @cindex python commands
25618 You can implement new @value{GDBN} CLI commands in Python. A CLI
25619 command is implemented using an instance of the @code{gdb.Command}
25620 class, most commonly using a subclass.
25622 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25623 The object initializer for @code{Command} registers the new command
25624 with @value{GDBN}. This initializer is normally invoked from the
25625 subclass' own @code{__init__} method.
25627 @var{name} is the name of the command. If @var{name} consists of
25628 multiple words, then the initial words are looked for as prefix
25629 commands. In this case, if one of the prefix commands does not exist,
25630 an exception is raised.
25632 There is no support for multi-line commands.
25634 @var{command_class} should be one of the @samp{COMMAND_} constants
25635 defined below. This argument tells @value{GDBN} how to categorize the
25636 new command in the help system.
25638 @var{completer_class} is an optional argument. If given, it should be
25639 one of the @samp{COMPLETE_} constants defined below. This argument
25640 tells @value{GDBN} how to perform completion for this command. If not
25641 given, @value{GDBN} will attempt to complete using the object's
25642 @code{complete} method (see below); if no such method is found, an
25643 error will occur when completion is attempted.
25645 @var{prefix} is an optional argument. If @code{True}, then the new
25646 command is a prefix command; sub-commands of this command may be
25649 The help text for the new command is taken from the Python
25650 documentation string for the command's class, if there is one. If no
25651 documentation string is provided, the default value ``This command is
25652 not documented.'' is used.
25655 @cindex don't repeat Python command
25656 @defun Command.dont_repeat ()
25657 By default, a @value{GDBN} command is repeated when the user enters a
25658 blank line at the command prompt. A command can suppress this
25659 behavior by invoking the @code{dont_repeat} method. This is similar
25660 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25663 @defun Command.invoke (argument, from_tty)
25664 This method is called by @value{GDBN} when this command is invoked.
25666 @var{argument} is a string. It is the argument to the command, after
25667 leading and trailing whitespace has been stripped.
25669 @var{from_tty} is a boolean argument. When true, this means that the
25670 command was entered by the user at the terminal; when false it means
25671 that the command came from elsewhere.
25673 If this method throws an exception, it is turned into a @value{GDBN}
25674 @code{error} call. Otherwise, the return value is ignored.
25676 @findex gdb.string_to_argv
25677 To break @var{argument} up into an argv-like string use
25678 @code{gdb.string_to_argv}. This function behaves identically to
25679 @value{GDBN}'s internal argument lexer @code{buildargv}.
25680 It is recommended to use this for consistency.
25681 Arguments are separated by spaces and may be quoted.
25685 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25686 ['1', '2 "3', '4 "5', "6 '7"]
25691 @cindex completion of Python commands
25692 @defun Command.complete (text, word)
25693 This method is called by @value{GDBN} when the user attempts
25694 completion on this command. All forms of completion are handled by
25695 this method, that is, the @key{TAB} and @key{M-?} key bindings
25696 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25699 The arguments @var{text} and @var{word} are both strings. @var{text}
25700 holds the complete command line up to the cursor's location.
25701 @var{word} holds the last word of the command line; this is computed
25702 using a word-breaking heuristic.
25704 The @code{complete} method can return several values:
25707 If the return value is a sequence, the contents of the sequence are
25708 used as the completions. It is up to @code{complete} to ensure that the
25709 contents actually do complete the word. A zero-length sequence is
25710 allowed, it means that there were no completions available. Only
25711 string elements of the sequence are used; other elements in the
25712 sequence are ignored.
25715 If the return value is one of the @samp{COMPLETE_} constants defined
25716 below, then the corresponding @value{GDBN}-internal completion
25717 function is invoked, and its result is used.
25720 All other results are treated as though there were no available
25725 When a new command is registered, it must be declared as a member of
25726 some general class of commands. This is used to classify top-level
25727 commands in the on-line help system; note that prefix commands are not
25728 listed under their own category but rather that of their top-level
25729 command. The available classifications are represented by constants
25730 defined in the @code{gdb} module:
25733 @findex COMMAND_NONE
25734 @findex gdb.COMMAND_NONE
25735 @item gdb.COMMAND_NONE
25736 The command does not belong to any particular class. A command in
25737 this category will not be displayed in any of the help categories.
25739 @findex COMMAND_RUNNING
25740 @findex gdb.COMMAND_RUNNING
25741 @item gdb.COMMAND_RUNNING
25742 The command is related to running the inferior. For example,
25743 @code{start}, @code{step}, and @code{continue} are in this category.
25744 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
25745 commands in this category.
25747 @findex COMMAND_DATA
25748 @findex gdb.COMMAND_DATA
25749 @item gdb.COMMAND_DATA
25750 The command is related to data or variables. For example,
25751 @code{call}, @code{find}, and @code{print} are in this category. Type
25752 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
25755 @findex COMMAND_STACK
25756 @findex gdb.COMMAND_STACK
25757 @item gdb.COMMAND_STACK
25758 The command has to do with manipulation of the stack. For example,
25759 @code{backtrace}, @code{frame}, and @code{return} are in this
25760 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
25761 list of commands in this category.
25763 @findex COMMAND_FILES
25764 @findex gdb.COMMAND_FILES
25765 @item gdb.COMMAND_FILES
25766 This class is used for file-related commands. For example,
25767 @code{file}, @code{list} and @code{section} are in this category.
25768 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
25769 commands in this category.
25771 @findex COMMAND_SUPPORT
25772 @findex gdb.COMMAND_SUPPORT
25773 @item gdb.COMMAND_SUPPORT
25774 This should be used for ``support facilities'', generally meaning
25775 things that are useful to the user when interacting with @value{GDBN},
25776 but not related to the state of the inferior. For example,
25777 @code{help}, @code{make}, and @code{shell} are in this category. Type
25778 @kbd{help support} at the @value{GDBN} prompt to see a list of
25779 commands in this category.
25781 @findex COMMAND_STATUS
25782 @findex gdb.COMMAND_STATUS
25783 @item gdb.COMMAND_STATUS
25784 The command is an @samp{info}-related command, that is, related to the
25785 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
25786 and @code{show} are in this category. Type @kbd{help status} at the
25787 @value{GDBN} prompt to see a list of commands in this category.
25789 @findex COMMAND_BREAKPOINTS
25790 @findex gdb.COMMAND_BREAKPOINTS
25791 @item gdb.COMMAND_BREAKPOINTS
25792 The command has to do with breakpoints. For example, @code{break},
25793 @code{clear}, and @code{delete} are in this category. Type @kbd{help
25794 breakpoints} at the @value{GDBN} prompt to see a list of commands in
25797 @findex COMMAND_TRACEPOINTS
25798 @findex gdb.COMMAND_TRACEPOINTS
25799 @item gdb.COMMAND_TRACEPOINTS
25800 The command has to do with tracepoints. For example, @code{trace},
25801 @code{actions}, and @code{tfind} are in this category. Type
25802 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
25803 commands in this category.
25805 @findex COMMAND_USER
25806 @findex gdb.COMMAND_USER
25807 @item gdb.COMMAND_USER
25808 The command is a general purpose command for the user, and typically
25809 does not fit in one of the other categories.
25810 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
25811 a list of commands in this category, as well as the list of gdb macros
25812 (@pxref{Sequences}).
25814 @findex COMMAND_OBSCURE
25815 @findex gdb.COMMAND_OBSCURE
25816 @item gdb.COMMAND_OBSCURE
25817 The command is only used in unusual circumstances, or is not of
25818 general interest to users. For example, @code{checkpoint},
25819 @code{fork}, and @code{stop} are in this category. Type @kbd{help
25820 obscure} at the @value{GDBN} prompt to see a list of commands in this
25823 @findex COMMAND_MAINTENANCE
25824 @findex gdb.COMMAND_MAINTENANCE
25825 @item gdb.COMMAND_MAINTENANCE
25826 The command is only useful to @value{GDBN} maintainers. The
25827 @code{maintenance} and @code{flushregs} commands are in this category.
25828 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
25829 commands in this category.
25832 A new command can use a predefined completion function, either by
25833 specifying it via an argument at initialization, or by returning it
25834 from the @code{complete} method. These predefined completion
25835 constants are all defined in the @code{gdb} module:
25838 @findex COMPLETE_NONE
25839 @findex gdb.COMPLETE_NONE
25840 @item gdb.COMPLETE_NONE
25841 This constant means that no completion should be done.
25843 @findex COMPLETE_FILENAME
25844 @findex gdb.COMPLETE_FILENAME
25845 @item gdb.COMPLETE_FILENAME
25846 This constant means that filename completion should be performed.
25848 @findex COMPLETE_LOCATION
25849 @findex gdb.COMPLETE_LOCATION
25850 @item gdb.COMPLETE_LOCATION
25851 This constant means that location completion should be done.
25852 @xref{Specify Location}.
25854 @findex COMPLETE_COMMAND
25855 @findex gdb.COMPLETE_COMMAND
25856 @item gdb.COMPLETE_COMMAND
25857 This constant means that completion should examine @value{GDBN}
25860 @findex COMPLETE_SYMBOL
25861 @findex gdb.COMPLETE_SYMBOL
25862 @item gdb.COMPLETE_SYMBOL
25863 This constant means that completion should be done using symbol names
25867 The following code snippet shows how a trivial CLI command can be
25868 implemented in Python:
25871 class HelloWorld (gdb.Command):
25872 """Greet the whole world."""
25874 def __init__ (self):
25875 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
25877 def invoke (self, arg, from_tty):
25878 print "Hello, World!"
25883 The last line instantiates the class, and is necessary to trigger the
25884 registration of the command with @value{GDBN}. Depending on how the
25885 Python code is read into @value{GDBN}, you may need to import the
25886 @code{gdb} module explicitly.
25888 @node Parameters In Python
25889 @subsubsection Parameters In Python
25891 @cindex parameters in python
25892 @cindex python parameters
25893 @tindex gdb.Parameter
25895 You can implement new @value{GDBN} parameters using Python. A new
25896 parameter is implemented as an instance of the @code{gdb.Parameter}
25899 Parameters are exposed to the user via the @code{set} and
25900 @code{show} commands. @xref{Help}.
25902 There are many parameters that already exist and can be set in
25903 @value{GDBN}. Two examples are: @code{set follow fork} and
25904 @code{set charset}. Setting these parameters influences certain
25905 behavior in @value{GDBN}. Similarly, you can define parameters that
25906 can be used to influence behavior in custom Python scripts and commands.
25908 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
25909 The object initializer for @code{Parameter} registers the new
25910 parameter with @value{GDBN}. This initializer is normally invoked
25911 from the subclass' own @code{__init__} method.
25913 @var{name} is the name of the new parameter. If @var{name} consists
25914 of multiple words, then the initial words are looked for as prefix
25915 parameters. An example of this can be illustrated with the
25916 @code{set print} set of parameters. If @var{name} is
25917 @code{print foo}, then @code{print} will be searched as the prefix
25918 parameter. In this case the parameter can subsequently be accessed in
25919 @value{GDBN} as @code{set print foo}.
25921 If @var{name} consists of multiple words, and no prefix parameter group
25922 can be found, an exception is raised.
25924 @var{command-class} should be one of the @samp{COMMAND_} constants
25925 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
25926 categorize the new parameter in the help system.
25928 @var{parameter-class} should be one of the @samp{PARAM_} constants
25929 defined below. This argument tells @value{GDBN} the type of the new
25930 parameter; this information is used for input validation and
25933 If @var{parameter-class} is @code{PARAM_ENUM}, then
25934 @var{enum-sequence} must be a sequence of strings. These strings
25935 represent the possible values for the parameter.
25937 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
25938 of a fourth argument will cause an exception to be thrown.
25940 The help text for the new parameter is taken from the Python
25941 documentation string for the parameter's class, if there is one. If
25942 there is no documentation string, a default value is used.
25945 @defvar Parameter.set_doc
25946 If this attribute exists, and is a string, then its value is used as
25947 the help text for this parameter's @code{set} command. The value is
25948 examined when @code{Parameter.__init__} is invoked; subsequent changes
25952 @defvar Parameter.show_doc
25953 If this attribute exists, and is a string, then its value is used as
25954 the help text for this parameter's @code{show} command. The value is
25955 examined when @code{Parameter.__init__} is invoked; subsequent changes
25959 @defvar Parameter.value
25960 The @code{value} attribute holds the underlying value of the
25961 parameter. It can be read and assigned to just as any other
25962 attribute. @value{GDBN} does validation when assignments are made.
25965 There are two methods that should be implemented in any
25966 @code{Parameter} class. These are:
25968 @defun Parameter.get_set_string (self)
25969 @value{GDBN} will call this method when a @var{parameter}'s value has
25970 been changed via the @code{set} API (for example, @kbd{set foo off}).
25971 The @code{value} attribute has already been populated with the new
25972 value and may be used in output. This method must return a string.
25975 @defun Parameter.get_show_string (self, svalue)
25976 @value{GDBN} will call this method when a @var{parameter}'s
25977 @code{show} API has been invoked (for example, @kbd{show foo}). The
25978 argument @code{svalue} receives the string representation of the
25979 current value. This method must return a string.
25982 When a new parameter is defined, its type must be specified. The
25983 available types are represented by constants defined in the @code{gdb}
25987 @findex PARAM_BOOLEAN
25988 @findex gdb.PARAM_BOOLEAN
25989 @item gdb.PARAM_BOOLEAN
25990 The value is a plain boolean. The Python boolean values, @code{True}
25991 and @code{False} are the only valid values.
25993 @findex PARAM_AUTO_BOOLEAN
25994 @findex gdb.PARAM_AUTO_BOOLEAN
25995 @item gdb.PARAM_AUTO_BOOLEAN
25996 The value has three possible states: true, false, and @samp{auto}. In
25997 Python, true and false are represented using boolean constants, and
25998 @samp{auto} is represented using @code{None}.
26000 @findex PARAM_UINTEGER
26001 @findex gdb.PARAM_UINTEGER
26002 @item gdb.PARAM_UINTEGER
26003 The value is an unsigned integer. The value of 0 should be
26004 interpreted to mean ``unlimited''.
26006 @findex PARAM_INTEGER
26007 @findex gdb.PARAM_INTEGER
26008 @item gdb.PARAM_INTEGER
26009 The value is a signed integer. The value of 0 should be interpreted
26010 to mean ``unlimited''.
26012 @findex PARAM_STRING
26013 @findex gdb.PARAM_STRING
26014 @item gdb.PARAM_STRING
26015 The value is a string. When the user modifies the string, any escape
26016 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
26017 translated into corresponding characters and encoded into the current
26020 @findex PARAM_STRING_NOESCAPE
26021 @findex gdb.PARAM_STRING_NOESCAPE
26022 @item gdb.PARAM_STRING_NOESCAPE
26023 The value is a string. When the user modifies the string, escapes are
26024 passed through untranslated.
26026 @findex PARAM_OPTIONAL_FILENAME
26027 @findex gdb.PARAM_OPTIONAL_FILENAME
26028 @item gdb.PARAM_OPTIONAL_FILENAME
26029 The value is a either a filename (a string), or @code{None}.
26031 @findex PARAM_FILENAME
26032 @findex gdb.PARAM_FILENAME
26033 @item gdb.PARAM_FILENAME
26034 The value is a filename. This is just like
26035 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
26037 @findex PARAM_ZINTEGER
26038 @findex gdb.PARAM_ZINTEGER
26039 @item gdb.PARAM_ZINTEGER
26040 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
26041 is interpreted as itself.
26044 @findex gdb.PARAM_ENUM
26045 @item gdb.PARAM_ENUM
26046 The value is a string, which must be one of a collection string
26047 constants provided when the parameter is created.
26050 @node Functions In Python
26051 @subsubsection Writing new convenience functions
26053 @cindex writing convenience functions
26054 @cindex convenience functions in python
26055 @cindex python convenience functions
26056 @tindex gdb.Function
26058 You can implement new convenience functions (@pxref{Convenience Vars})
26059 in Python. A convenience function is an instance of a subclass of the
26060 class @code{gdb.Function}.
26062 @defun Function.__init__ (name)
26063 The initializer for @code{Function} registers the new function with
26064 @value{GDBN}. The argument @var{name} is the name of the function,
26065 a string. The function will be visible to the user as a convenience
26066 variable of type @code{internal function}, whose name is the same as
26067 the given @var{name}.
26069 The documentation for the new function is taken from the documentation
26070 string for the new class.
26073 @defun Function.invoke (@var{*args})
26074 When a convenience function is evaluated, its arguments are converted
26075 to instances of @code{gdb.Value}, and then the function's
26076 @code{invoke} method is called. Note that @value{GDBN} does not
26077 predetermine the arity of convenience functions. Instead, all
26078 available arguments are passed to @code{invoke}, following the
26079 standard Python calling convention. In particular, a convenience
26080 function can have default values for parameters without ill effect.
26082 The return value of this method is used as its value in the enclosing
26083 expression. If an ordinary Python value is returned, it is converted
26084 to a @code{gdb.Value} following the usual rules.
26087 The following code snippet shows how a trivial convenience function can
26088 be implemented in Python:
26091 class Greet (gdb.Function):
26092 """Return string to greet someone.
26093 Takes a name as argument."""
26095 def __init__ (self):
26096 super (Greet, self).__init__ ("greet")
26098 def invoke (self, name):
26099 return "Hello, %s!" % name.string ()
26104 The last line instantiates the class, and is necessary to trigger the
26105 registration of the function with @value{GDBN}. Depending on how the
26106 Python code is read into @value{GDBN}, you may need to import the
26107 @code{gdb} module explicitly.
26109 Now you can use the function in an expression:
26112 (gdb) print $greet("Bob")
26116 @node Progspaces In Python
26117 @subsubsection Program Spaces In Python
26119 @cindex progspaces in python
26120 @tindex gdb.Progspace
26122 A program space, or @dfn{progspace}, represents a symbolic view
26123 of an address space.
26124 It consists of all of the objfiles of the program.
26125 @xref{Objfiles In Python}.
26126 @xref{Inferiors and Programs, program spaces}, for more details
26127 about program spaces.
26129 The following progspace-related functions are available in the
26132 @findex gdb.current_progspace
26133 @defun gdb.current_progspace ()
26134 This function returns the program space of the currently selected inferior.
26135 @xref{Inferiors and Programs}.
26138 @findex gdb.progspaces
26139 @defun gdb.progspaces ()
26140 Return a sequence of all the progspaces currently known to @value{GDBN}.
26143 Each progspace is represented by an instance of the @code{gdb.Progspace}
26146 @defvar Progspace.filename
26147 The file name of the progspace as a string.
26150 @defvar Progspace.pretty_printers
26151 The @code{pretty_printers} attribute is a list of functions. It is
26152 used to look up pretty-printers. A @code{Value} is passed to each
26153 function in order; if the function returns @code{None}, then the
26154 search continues. Otherwise, the return value should be an object
26155 which is used to format the value. @xref{Pretty Printing API}, for more
26159 @defvar Progspace.type_printers
26160 The @code{type_printers} attribute is a list of type printer objects.
26161 @xref{Type Printing API}, for more information.
26164 @defvar Progspace.frame_filters
26165 The @code{frame_filters} attribute is a dictionary of frame filter
26166 objects. @xref{Frame Filter API}, for more information.
26169 @node Objfiles In Python
26170 @subsubsection Objfiles In Python
26172 @cindex objfiles in python
26173 @tindex gdb.Objfile
26175 @value{GDBN} loads symbols for an inferior from various
26176 symbol-containing files (@pxref{Files}). These include the primary
26177 executable file, any shared libraries used by the inferior, and any
26178 separate debug info files (@pxref{Separate Debug Files}).
26179 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26181 The following objfile-related functions are available in the
26184 @findex gdb.current_objfile
26185 @defun gdb.current_objfile ()
26186 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26187 sets the ``current objfile'' to the corresponding objfile. This
26188 function returns the current objfile. If there is no current objfile,
26189 this function returns @code{None}.
26192 @findex gdb.objfiles
26193 @defun gdb.objfiles ()
26194 Return a sequence of all the objfiles current known to @value{GDBN}.
26195 @xref{Objfiles In Python}.
26198 Each objfile is represented by an instance of the @code{gdb.Objfile}
26201 @defvar Objfile.filename
26202 The file name of the objfile as a string.
26205 @defvar Objfile.pretty_printers
26206 The @code{pretty_printers} attribute is a list of functions. It is
26207 used to look up pretty-printers. A @code{Value} is passed to each
26208 function in order; if the function returns @code{None}, then the
26209 search continues. Otherwise, the return value should be an object
26210 which is used to format the value. @xref{Pretty Printing API}, for more
26214 @defvar Objfile.type_printers
26215 The @code{type_printers} attribute is a list of type printer objects.
26216 @xref{Type Printing API}, for more information.
26219 @defvar Objfile.frame_filters
26220 The @code{frame_filters} attribute is a dictionary of frame filter
26221 objects. @xref{Frame Filter API}, for more information.
26224 A @code{gdb.Objfile} object has the following methods:
26226 @defun Objfile.is_valid ()
26227 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26228 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26229 if the object file it refers to is not loaded in @value{GDBN} any
26230 longer. All other @code{gdb.Objfile} methods will throw an exception
26231 if it is invalid at the time the method is called.
26234 @node Frames In Python
26235 @subsubsection Accessing inferior stack frames from Python.
26237 @cindex frames in python
26238 When the debugged program stops, @value{GDBN} is able to analyze its call
26239 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26240 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26241 while its corresponding frame exists in the inferior's stack. If you try
26242 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26243 exception (@pxref{Exception Handling}).
26245 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26249 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26253 The following frame-related functions are available in the @code{gdb} module:
26255 @findex gdb.selected_frame
26256 @defun gdb.selected_frame ()
26257 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26260 @findex gdb.newest_frame
26261 @defun gdb.newest_frame ()
26262 Return the newest frame object for the selected thread.
26265 @defun gdb.frame_stop_reason_string (reason)
26266 Return a string explaining the reason why @value{GDBN} stopped unwinding
26267 frames, as expressed by the given @var{reason} code (an integer, see the
26268 @code{unwind_stop_reason} method further down in this section).
26271 A @code{gdb.Frame} object has the following methods:
26273 @defun Frame.is_valid ()
26274 Returns true if the @code{gdb.Frame} object is valid, false if not.
26275 A frame object can become invalid if the frame it refers to doesn't
26276 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26277 an exception if it is invalid at the time the method is called.
26280 @defun Frame.name ()
26281 Returns the function name of the frame, or @code{None} if it can't be
26285 @defun Frame.architecture ()
26286 Returns the @code{gdb.Architecture} object corresponding to the frame's
26287 architecture. @xref{Architectures In Python}.
26290 @defun Frame.type ()
26291 Returns the type of the frame. The value can be one of:
26293 @item gdb.NORMAL_FRAME
26294 An ordinary stack frame.
26296 @item gdb.DUMMY_FRAME
26297 A fake stack frame that was created by @value{GDBN} when performing an
26298 inferior function call.
26300 @item gdb.INLINE_FRAME
26301 A frame representing an inlined function. The function was inlined
26302 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26304 @item gdb.TAILCALL_FRAME
26305 A frame representing a tail call. @xref{Tail Call Frames}.
26307 @item gdb.SIGTRAMP_FRAME
26308 A signal trampoline frame. This is the frame created by the OS when
26309 it calls into a signal handler.
26311 @item gdb.ARCH_FRAME
26312 A fake stack frame representing a cross-architecture call.
26314 @item gdb.SENTINEL_FRAME
26315 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26320 @defun Frame.unwind_stop_reason ()
26321 Return an integer representing the reason why it's not possible to find
26322 more frames toward the outermost frame. Use
26323 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26324 function to a string. The value can be one of:
26327 @item gdb.FRAME_UNWIND_NO_REASON
26328 No particular reason (older frames should be available).
26330 @item gdb.FRAME_UNWIND_NULL_ID
26331 The previous frame's analyzer returns an invalid result.
26333 @item gdb.FRAME_UNWIND_OUTERMOST
26334 This frame is the outermost.
26336 @item gdb.FRAME_UNWIND_UNAVAILABLE
26337 Cannot unwind further, because that would require knowing the
26338 values of registers or memory that have not been collected.
26340 @item gdb.FRAME_UNWIND_INNER_ID
26341 This frame ID looks like it ought to belong to a NEXT frame,
26342 but we got it for a PREV frame. Normally, this is a sign of
26343 unwinder failure. It could also indicate stack corruption.
26345 @item gdb.FRAME_UNWIND_SAME_ID
26346 This frame has the same ID as the previous one. That means
26347 that unwinding further would almost certainly give us another
26348 frame with exactly the same ID, so break the chain. Normally,
26349 this is a sign of unwinder failure. It could also indicate
26352 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26353 The frame unwinder did not find any saved PC, but we needed
26354 one to unwind further.
26356 @item gdb.FRAME_UNWIND_FIRST_ERROR
26357 Any stop reason greater or equal to this value indicates some kind
26358 of error. This special value facilitates writing code that tests
26359 for errors in unwinding in a way that will work correctly even if
26360 the list of the other values is modified in future @value{GDBN}
26361 versions. Using it, you could write:
26363 reason = gdb.selected_frame().unwind_stop_reason ()
26364 reason_str = gdb.frame_stop_reason_string (reason)
26365 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26366 print "An error occured: %s" % reason_str
26373 Returns the frame's resume address.
26376 @defun Frame.block ()
26377 Return the frame's code block. @xref{Blocks In Python}.
26380 @defun Frame.function ()
26381 Return the symbol for the function corresponding to this frame.
26382 @xref{Symbols In Python}.
26385 @defun Frame.older ()
26386 Return the frame that called this frame.
26389 @defun Frame.newer ()
26390 Return the frame called by this frame.
26393 @defun Frame.find_sal ()
26394 Return the frame's symtab and line object.
26395 @xref{Symbol Tables In Python}.
26398 @defun Frame.read_var (variable @r{[}, block@r{]})
26399 Return the value of @var{variable} in this frame. If the optional
26400 argument @var{block} is provided, search for the variable from that
26401 block; otherwise start at the frame's current block (which is
26402 determined by the frame's current program counter). @var{variable}
26403 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26404 @code{gdb.Block} object.
26407 @defun Frame.select ()
26408 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26412 @node Blocks In Python
26413 @subsubsection Accessing blocks from Python.
26415 @cindex blocks in python
26418 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26419 roughly to a scope in the source code. Blocks are organized
26420 hierarchically, and are represented individually in Python as a
26421 @code{gdb.Block}. Blocks rely on debugging information being
26424 A frame has a block. Please see @ref{Frames In Python}, for a more
26425 in-depth discussion of frames.
26427 The outermost block is known as the @dfn{global block}. The global
26428 block typically holds public global variables and functions.
26430 The block nested just inside the global block is the @dfn{static
26431 block}. The static block typically holds file-scoped variables and
26434 @value{GDBN} provides a method to get a block's superblock, but there
26435 is currently no way to examine the sub-blocks of a block, or to
26436 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26439 Here is a short example that should help explain blocks:
26442 /* This is in the global block. */
26445 /* This is in the static block. */
26446 static int file_scope;
26448 /* 'function' is in the global block, and 'argument' is
26449 in a block nested inside of 'function'. */
26450 int function (int argument)
26452 /* 'local' is in a block inside 'function'. It may or may
26453 not be in the same block as 'argument'. */
26457 /* 'inner' is in a block whose superblock is the one holding
26461 /* If this call is expanded by the compiler, you may see
26462 a nested block here whose function is 'inline_function'
26463 and whose superblock is the one holding 'inner'. */
26464 inline_function ();
26469 A @code{gdb.Block} is iterable. The iterator returns the symbols
26470 (@pxref{Symbols In Python}) local to the block. Python programs
26471 should not assume that a specific block object will always contain a
26472 given symbol, since changes in @value{GDBN} features and
26473 infrastructure may cause symbols move across blocks in a symbol
26476 The following block-related functions are available in the @code{gdb}
26479 @findex gdb.block_for_pc
26480 @defun gdb.block_for_pc (pc)
26481 Return the innermost @code{gdb.Block} containing the given @var{pc}
26482 value. If the block cannot be found for the @var{pc} value specified,
26483 the function will return @code{None}.
26486 A @code{gdb.Block} object has the following methods:
26488 @defun Block.is_valid ()
26489 Returns @code{True} if the @code{gdb.Block} object is valid,
26490 @code{False} if not. A block object can become invalid if the block it
26491 refers to doesn't exist anymore in the inferior. All other
26492 @code{gdb.Block} methods will throw an exception if it is invalid at
26493 the time the method is called. The block's validity is also checked
26494 during iteration over symbols of the block.
26497 A @code{gdb.Block} object has the following attributes:
26499 @defvar Block.start
26500 The start address of the block. This attribute is not writable.
26504 The end address of the block. This attribute is not writable.
26507 @defvar Block.function
26508 The name of the block represented as a @code{gdb.Symbol}. If the
26509 block is not named, then this attribute holds @code{None}. This
26510 attribute is not writable.
26512 For ordinary function blocks, the superblock is the static block.
26513 However, you should note that it is possible for a function block to
26514 have a superblock that is not the static block -- for instance this
26515 happens for an inlined function.
26518 @defvar Block.superblock
26519 The block containing this block. If this parent block does not exist,
26520 this attribute holds @code{None}. This attribute is not writable.
26523 @defvar Block.global_block
26524 The global block associated with this block. This attribute is not
26528 @defvar Block.static_block
26529 The static block associated with this block. This attribute is not
26533 @defvar Block.is_global
26534 @code{True} if the @code{gdb.Block} object is a global block,
26535 @code{False} if not. This attribute is not
26539 @defvar Block.is_static
26540 @code{True} if the @code{gdb.Block} object is a static block,
26541 @code{False} if not. This attribute is not writable.
26544 @node Symbols In Python
26545 @subsubsection Python representation of Symbols.
26547 @cindex symbols in python
26550 @value{GDBN} represents every variable, function and type as an
26551 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26552 Similarly, Python represents these symbols in @value{GDBN} with the
26553 @code{gdb.Symbol} object.
26555 The following symbol-related functions are available in the @code{gdb}
26558 @findex gdb.lookup_symbol
26559 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26560 This function searches for a symbol by name. The search scope can be
26561 restricted to the parameters defined in the optional domain and block
26564 @var{name} is the name of the symbol. It must be a string. The
26565 optional @var{block} argument restricts the search to symbols visible
26566 in that @var{block}. The @var{block} argument must be a
26567 @code{gdb.Block} object. If omitted, the block for the current frame
26568 is used. The optional @var{domain} argument restricts
26569 the search to the domain type. The @var{domain} argument must be a
26570 domain constant defined in the @code{gdb} module and described later
26573 The result is a tuple of two elements.
26574 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26576 If the symbol is found, the second element is @code{True} if the symbol
26577 is a field of a method's object (e.g., @code{this} in C@t{++}),
26578 otherwise it is @code{False}.
26579 If the symbol is not found, the second element is @code{False}.
26582 @findex gdb.lookup_global_symbol
26583 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26584 This function searches for a global symbol by name.
26585 The search scope can be restricted to by the domain argument.
26587 @var{name} is the name of the symbol. It must be a string.
26588 The optional @var{domain} argument restricts the search to the domain type.
26589 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26590 module and described later in this chapter.
26592 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26596 A @code{gdb.Symbol} object has the following attributes:
26598 @defvar Symbol.type
26599 The type of the symbol or @code{None} if no type is recorded.
26600 This attribute is represented as a @code{gdb.Type} object.
26601 @xref{Types In Python}. This attribute is not writable.
26604 @defvar Symbol.symtab
26605 The symbol table in which the symbol appears. This attribute is
26606 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26607 Python}. This attribute is not writable.
26610 @defvar Symbol.line
26611 The line number in the source code at which the symbol was defined.
26612 This is an integer.
26615 @defvar Symbol.name
26616 The name of the symbol as a string. This attribute is not writable.
26619 @defvar Symbol.linkage_name
26620 The name of the symbol, as used by the linker (i.e., may be mangled).
26621 This attribute is not writable.
26624 @defvar Symbol.print_name
26625 The name of the symbol in a form suitable for output. This is either
26626 @code{name} or @code{linkage_name}, depending on whether the user
26627 asked @value{GDBN} to display demangled or mangled names.
26630 @defvar Symbol.addr_class
26631 The address class of the symbol. This classifies how to find the value
26632 of a symbol. Each address class is a constant defined in the
26633 @code{gdb} module and described later in this chapter.
26636 @defvar Symbol.needs_frame
26637 This is @code{True} if evaluating this symbol's value requires a frame
26638 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26639 local variables will require a frame, but other symbols will not.
26642 @defvar Symbol.is_argument
26643 @code{True} if the symbol is an argument of a function.
26646 @defvar Symbol.is_constant
26647 @code{True} if the symbol is a constant.
26650 @defvar Symbol.is_function
26651 @code{True} if the symbol is a function or a method.
26654 @defvar Symbol.is_variable
26655 @code{True} if the symbol is a variable.
26658 A @code{gdb.Symbol} object has the following methods:
26660 @defun Symbol.is_valid ()
26661 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26662 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26663 the symbol it refers to does not exist in @value{GDBN} any longer.
26664 All other @code{gdb.Symbol} methods will throw an exception if it is
26665 invalid at the time the method is called.
26668 @defun Symbol.value (@r{[}frame@r{]})
26669 Compute the value of the symbol, as a @code{gdb.Value}. For
26670 functions, this computes the address of the function, cast to the
26671 appropriate type. If the symbol requires a frame in order to compute
26672 its value, then @var{frame} must be given. If @var{frame} is not
26673 given, or if @var{frame} is invalid, then this method will throw an
26677 The available domain categories in @code{gdb.Symbol} are represented
26678 as constants in the @code{gdb} module:
26681 @findex SYMBOL_UNDEF_DOMAIN
26682 @findex gdb.SYMBOL_UNDEF_DOMAIN
26683 @item gdb.SYMBOL_UNDEF_DOMAIN
26684 This is used when a domain has not been discovered or none of the
26685 following domains apply. This usually indicates an error either
26686 in the symbol information or in @value{GDBN}'s handling of symbols.
26687 @findex SYMBOL_VAR_DOMAIN
26688 @findex gdb.SYMBOL_VAR_DOMAIN
26689 @item gdb.SYMBOL_VAR_DOMAIN
26690 This domain contains variables, function names, typedef names and enum
26692 @findex SYMBOL_STRUCT_DOMAIN
26693 @findex gdb.SYMBOL_STRUCT_DOMAIN
26694 @item gdb.SYMBOL_STRUCT_DOMAIN
26695 This domain holds struct, union and enum type names.
26696 @findex SYMBOL_LABEL_DOMAIN
26697 @findex gdb.SYMBOL_LABEL_DOMAIN
26698 @item gdb.SYMBOL_LABEL_DOMAIN
26699 This domain contains names of labels (for gotos).
26700 @findex SYMBOL_VARIABLES_DOMAIN
26701 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26702 @item gdb.SYMBOL_VARIABLES_DOMAIN
26703 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26704 contains everything minus functions and types.
26705 @findex SYMBOL_FUNCTIONS_DOMAIN
26706 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
26707 @item gdb.SYMBOL_FUNCTION_DOMAIN
26708 This domain contains all functions.
26709 @findex SYMBOL_TYPES_DOMAIN
26710 @findex gdb.SYMBOL_TYPES_DOMAIN
26711 @item gdb.SYMBOL_TYPES_DOMAIN
26712 This domain contains all types.
26715 The available address class categories in @code{gdb.Symbol} are represented
26716 as constants in the @code{gdb} module:
26719 @findex SYMBOL_LOC_UNDEF
26720 @findex gdb.SYMBOL_LOC_UNDEF
26721 @item gdb.SYMBOL_LOC_UNDEF
26722 If this is returned by address class, it indicates an error either in
26723 the symbol information or in @value{GDBN}'s handling of symbols.
26724 @findex SYMBOL_LOC_CONST
26725 @findex gdb.SYMBOL_LOC_CONST
26726 @item gdb.SYMBOL_LOC_CONST
26727 Value is constant int.
26728 @findex SYMBOL_LOC_STATIC
26729 @findex gdb.SYMBOL_LOC_STATIC
26730 @item gdb.SYMBOL_LOC_STATIC
26731 Value is at a fixed address.
26732 @findex SYMBOL_LOC_REGISTER
26733 @findex gdb.SYMBOL_LOC_REGISTER
26734 @item gdb.SYMBOL_LOC_REGISTER
26735 Value is in a register.
26736 @findex SYMBOL_LOC_ARG
26737 @findex gdb.SYMBOL_LOC_ARG
26738 @item gdb.SYMBOL_LOC_ARG
26739 Value is an argument. This value is at the offset stored within the
26740 symbol inside the frame's argument list.
26741 @findex SYMBOL_LOC_REF_ARG
26742 @findex gdb.SYMBOL_LOC_REF_ARG
26743 @item gdb.SYMBOL_LOC_REF_ARG
26744 Value address is stored in the frame's argument list. Just like
26745 @code{LOC_ARG} except that the value's address is stored at the
26746 offset, not the value itself.
26747 @findex SYMBOL_LOC_REGPARM_ADDR
26748 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
26749 @item gdb.SYMBOL_LOC_REGPARM_ADDR
26750 Value is a specified register. Just like @code{LOC_REGISTER} except
26751 the register holds the address of the argument instead of the argument
26753 @findex SYMBOL_LOC_LOCAL
26754 @findex gdb.SYMBOL_LOC_LOCAL
26755 @item gdb.SYMBOL_LOC_LOCAL
26756 Value is a local variable.
26757 @findex SYMBOL_LOC_TYPEDEF
26758 @findex gdb.SYMBOL_LOC_TYPEDEF
26759 @item gdb.SYMBOL_LOC_TYPEDEF
26760 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
26762 @findex SYMBOL_LOC_BLOCK
26763 @findex gdb.SYMBOL_LOC_BLOCK
26764 @item gdb.SYMBOL_LOC_BLOCK
26766 @findex SYMBOL_LOC_CONST_BYTES
26767 @findex gdb.SYMBOL_LOC_CONST_BYTES
26768 @item gdb.SYMBOL_LOC_CONST_BYTES
26769 Value is a byte-sequence.
26770 @findex SYMBOL_LOC_UNRESOLVED
26771 @findex gdb.SYMBOL_LOC_UNRESOLVED
26772 @item gdb.SYMBOL_LOC_UNRESOLVED
26773 Value is at a fixed address, but the address of the variable has to be
26774 determined from the minimal symbol table whenever the variable is
26776 @findex SYMBOL_LOC_OPTIMIZED_OUT
26777 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
26778 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
26779 The value does not actually exist in the program.
26780 @findex SYMBOL_LOC_COMPUTED
26781 @findex gdb.SYMBOL_LOC_COMPUTED
26782 @item gdb.SYMBOL_LOC_COMPUTED
26783 The value's address is a computed location.
26786 @node Symbol Tables In Python
26787 @subsubsection Symbol table representation in Python.
26789 @cindex symbol tables in python
26791 @tindex gdb.Symtab_and_line
26793 Access to symbol table data maintained by @value{GDBN} on the inferior
26794 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
26795 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
26796 from the @code{find_sal} method in @code{gdb.Frame} object.
26797 @xref{Frames In Python}.
26799 For more information on @value{GDBN}'s symbol table management, see
26800 @ref{Symbols, ,Examining the Symbol Table}, for more information.
26802 A @code{gdb.Symtab_and_line} object has the following attributes:
26804 @defvar Symtab_and_line.symtab
26805 The symbol table object (@code{gdb.Symtab}) for this frame.
26806 This attribute is not writable.
26809 @defvar Symtab_and_line.pc
26810 Indicates the start of the address range occupied by code for the
26811 current source line. This attribute is not writable.
26814 @defvar Symtab_and_line.last
26815 Indicates the end of the address range occupied by code for the current
26816 source line. This attribute is not writable.
26819 @defvar Symtab_and_line.line
26820 Indicates the current line number for this object. This
26821 attribute is not writable.
26824 A @code{gdb.Symtab_and_line} object has the following methods:
26826 @defun Symtab_and_line.is_valid ()
26827 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
26828 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
26829 invalid if the Symbol table and line object it refers to does not
26830 exist in @value{GDBN} any longer. All other
26831 @code{gdb.Symtab_and_line} methods will throw an exception if it is
26832 invalid at the time the method is called.
26835 A @code{gdb.Symtab} object has the following attributes:
26837 @defvar Symtab.filename
26838 The symbol table's source filename. This attribute is not writable.
26841 @defvar Symtab.objfile
26842 The symbol table's backing object file. @xref{Objfiles In Python}.
26843 This attribute is not writable.
26846 A @code{gdb.Symtab} object has the following methods:
26848 @defun Symtab.is_valid ()
26849 Returns @code{True} if the @code{gdb.Symtab} object is valid,
26850 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
26851 the symbol table it refers to does not exist in @value{GDBN} any
26852 longer. All other @code{gdb.Symtab} methods will throw an exception
26853 if it is invalid at the time the method is called.
26856 @defun Symtab.fullname ()
26857 Return the symbol table's source absolute file name.
26860 @defun Symtab.global_block ()
26861 Return the global block of the underlying symbol table.
26862 @xref{Blocks In Python}.
26865 @defun Symtab.static_block ()
26866 Return the static block of the underlying symbol table.
26867 @xref{Blocks In Python}.
26870 @node Breakpoints In Python
26871 @subsubsection Manipulating breakpoints using Python
26873 @cindex breakpoints in python
26874 @tindex gdb.Breakpoint
26876 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
26879 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
26880 Create a new breakpoint. @var{spec} is a string naming the
26881 location of the breakpoint, or an expression that defines a
26882 watchpoint. The contents can be any location recognized by the
26883 @code{break} command, or in the case of a watchpoint, by the @code{watch}
26884 command. The optional @var{type} denotes the breakpoint to create
26885 from the types defined later in this chapter. This argument can be
26886 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
26887 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
26888 allows the breakpoint to become invisible to the user. The breakpoint
26889 will neither be reported when created, nor will it be listed in the
26890 output from @code{info breakpoints} (but will be listed with the
26891 @code{maint info breakpoints} command). The optional @var{wp_class}
26892 argument defines the class of watchpoint to create, if @var{type} is
26893 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
26894 assumed to be a @code{gdb.WP_WRITE} class.
26897 @defun Breakpoint.stop (self)
26898 The @code{gdb.Breakpoint} class can be sub-classed and, in
26899 particular, you may choose to implement the @code{stop} method.
26900 If this method is defined as a sub-class of @code{gdb.Breakpoint},
26901 it will be called when the inferior reaches any location of a
26902 breakpoint which instantiates that sub-class. If the method returns
26903 @code{True}, the inferior will be stopped at the location of the
26904 breakpoint, otherwise the inferior will continue.
26906 If there are multiple breakpoints at the same location with a
26907 @code{stop} method, each one will be called regardless of the
26908 return status of the previous. This ensures that all @code{stop}
26909 methods have a chance to execute at that location. In this scenario
26910 if one of the methods returns @code{True} but the others return
26911 @code{False}, the inferior will still be stopped.
26913 You should not alter the execution state of the inferior (i.e.@:, step,
26914 next, etc.), alter the current frame context (i.e.@:, change the current
26915 active frame), or alter, add or delete any breakpoint. As a general
26916 rule, you should not alter any data within @value{GDBN} or the inferior
26919 Example @code{stop} implementation:
26922 class MyBreakpoint (gdb.Breakpoint):
26924 inf_val = gdb.parse_and_eval("foo")
26931 The available watchpoint types represented by constants are defined in the
26936 @findex gdb.WP_READ
26938 Read only watchpoint.
26941 @findex gdb.WP_WRITE
26943 Write only watchpoint.
26946 @findex gdb.WP_ACCESS
26947 @item gdb.WP_ACCESS
26948 Read/Write watchpoint.
26951 @defun Breakpoint.is_valid ()
26952 Return @code{True} if this @code{Breakpoint} object is valid,
26953 @code{False} otherwise. A @code{Breakpoint} object can become invalid
26954 if the user deletes the breakpoint. In this case, the object still
26955 exists, but the underlying breakpoint does not. In the cases of
26956 watchpoint scope, the watchpoint remains valid even if execution of the
26957 inferior leaves the scope of that watchpoint.
26960 @defun Breakpoint.delete
26961 Permanently deletes the @value{GDBN} breakpoint. This also
26962 invalidates the Python @code{Breakpoint} object. Any further access
26963 to this object's attributes or methods will raise an error.
26966 @defvar Breakpoint.enabled
26967 This attribute is @code{True} if the breakpoint is enabled, and
26968 @code{False} otherwise. This attribute is writable.
26971 @defvar Breakpoint.silent
26972 This attribute is @code{True} if the breakpoint is silent, and
26973 @code{False} otherwise. This attribute is writable.
26975 Note that a breakpoint can also be silent if it has commands and the
26976 first command is @code{silent}. This is not reported by the
26977 @code{silent} attribute.
26980 @defvar Breakpoint.thread
26981 If the breakpoint is thread-specific, this attribute holds the thread
26982 id. If the breakpoint is not thread-specific, this attribute is
26983 @code{None}. This attribute is writable.
26986 @defvar Breakpoint.task
26987 If the breakpoint is Ada task-specific, this attribute holds the Ada task
26988 id. If the breakpoint is not task-specific (or the underlying
26989 language is not Ada), this attribute is @code{None}. This attribute
26993 @defvar Breakpoint.ignore_count
26994 This attribute holds the ignore count for the breakpoint, an integer.
26995 This attribute is writable.
26998 @defvar Breakpoint.number
26999 This attribute holds the breakpoint's number --- the identifier used by
27000 the user to manipulate the breakpoint. This attribute is not writable.
27003 @defvar Breakpoint.type
27004 This attribute holds the breakpoint's type --- the identifier used to
27005 determine the actual breakpoint type or use-case. This attribute is not
27009 @defvar Breakpoint.visible
27010 This attribute tells whether the breakpoint is visible to the user
27011 when set, or when the @samp{info breakpoints} command is run. This
27012 attribute is not writable.
27015 The available types are represented by constants defined in the @code{gdb}
27019 @findex BP_BREAKPOINT
27020 @findex gdb.BP_BREAKPOINT
27021 @item gdb.BP_BREAKPOINT
27022 Normal code breakpoint.
27024 @findex BP_WATCHPOINT
27025 @findex gdb.BP_WATCHPOINT
27026 @item gdb.BP_WATCHPOINT
27027 Watchpoint breakpoint.
27029 @findex BP_HARDWARE_WATCHPOINT
27030 @findex gdb.BP_HARDWARE_WATCHPOINT
27031 @item gdb.BP_HARDWARE_WATCHPOINT
27032 Hardware assisted watchpoint.
27034 @findex BP_READ_WATCHPOINT
27035 @findex gdb.BP_READ_WATCHPOINT
27036 @item gdb.BP_READ_WATCHPOINT
27037 Hardware assisted read watchpoint.
27039 @findex BP_ACCESS_WATCHPOINT
27040 @findex gdb.BP_ACCESS_WATCHPOINT
27041 @item gdb.BP_ACCESS_WATCHPOINT
27042 Hardware assisted access watchpoint.
27045 @defvar Breakpoint.hit_count
27046 This attribute holds the hit count for the breakpoint, an integer.
27047 This attribute is writable, but currently it can only be set to zero.
27050 @defvar Breakpoint.location
27051 This attribute holds the location of the breakpoint, as specified by
27052 the user. It is a string. If the breakpoint does not have a location
27053 (that is, it is a watchpoint) the attribute's value is @code{None}. This
27054 attribute is not writable.
27057 @defvar Breakpoint.expression
27058 This attribute holds a breakpoint expression, as specified by
27059 the user. It is a string. If the breakpoint does not have an
27060 expression (the breakpoint is not a watchpoint) the attribute's value
27061 is @code{None}. This attribute is not writable.
27064 @defvar Breakpoint.condition
27065 This attribute holds the condition of the breakpoint, as specified by
27066 the user. It is a string. If there is no condition, this attribute's
27067 value is @code{None}. This attribute is writable.
27070 @defvar Breakpoint.commands
27071 This attribute holds the commands attached to the breakpoint. If
27072 there are commands, this attribute's value is a string holding all the
27073 commands, separated by newlines. If there are no commands, this
27074 attribute is @code{None}. This attribute is not writable.
27077 @node Finish Breakpoints in Python
27078 @subsubsection Finish Breakpoints
27080 @cindex python finish breakpoints
27081 @tindex gdb.FinishBreakpoint
27083 A finish breakpoint is a temporary breakpoint set at the return address of
27084 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27085 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27086 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27087 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27088 Finish breakpoints are thread specific and must be create with the right
27091 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27092 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27093 object @var{frame}. If @var{frame} is not provided, this defaults to the
27094 newest frame. The optional @var{internal} argument allows the breakpoint to
27095 become invisible to the user. @xref{Breakpoints In Python}, for further
27096 details about this argument.
27099 @defun FinishBreakpoint.out_of_scope (self)
27100 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27101 @code{return} command, @dots{}), a function may not properly terminate, and
27102 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27103 situation, the @code{out_of_scope} callback will be triggered.
27105 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27109 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27111 print "normal finish"
27114 def out_of_scope ():
27115 print "abnormal finish"
27119 @defvar FinishBreakpoint.return_value
27120 When @value{GDBN} is stopped at a finish breakpoint and the frame
27121 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27122 attribute will contain a @code{gdb.Value} object corresponding to the return
27123 value of the function. The value will be @code{None} if the function return
27124 type is @code{void} or if the return value was not computable. This attribute
27128 @node Lazy Strings In Python
27129 @subsubsection Python representation of lazy strings.
27131 @cindex lazy strings in python
27132 @tindex gdb.LazyString
27134 A @dfn{lazy string} is a string whose contents is not retrieved or
27135 encoded until it is needed.
27137 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27138 @code{address} that points to a region of memory, an @code{encoding}
27139 that will be used to encode that region of memory, and a @code{length}
27140 to delimit the region of memory that represents the string. The
27141 difference between a @code{gdb.LazyString} and a string wrapped within
27142 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27143 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27144 retrieved and encoded during printing, while a @code{gdb.Value}
27145 wrapping a string is immediately retrieved and encoded on creation.
27147 A @code{gdb.LazyString} object has the following functions:
27149 @defun LazyString.value ()
27150 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27151 will point to the string in memory, but will lose all the delayed
27152 retrieval, encoding and handling that @value{GDBN} applies to a
27153 @code{gdb.LazyString}.
27156 @defvar LazyString.address
27157 This attribute holds the address of the string. This attribute is not
27161 @defvar LazyString.length
27162 This attribute holds the length of the string in characters. If the
27163 length is -1, then the string will be fetched and encoded up to the
27164 first null of appropriate width. This attribute is not writable.
27167 @defvar LazyString.encoding
27168 This attribute holds the encoding that will be applied to the string
27169 when the string is printed by @value{GDBN}. If the encoding is not
27170 set, or contains an empty string, then @value{GDBN} will select the
27171 most appropriate encoding when the string is printed. This attribute
27175 @defvar LazyString.type
27176 This attribute holds the type that is represented by the lazy string's
27177 type. For a lazy string this will always be a pointer type. To
27178 resolve this to the lazy string's character type, use the type's
27179 @code{target} method. @xref{Types In Python}. This attribute is not
27183 @node Architectures In Python
27184 @subsubsection Python representation of architectures
27185 @cindex Python architectures
27187 @value{GDBN} uses architecture specific parameters and artifacts in a
27188 number of its various computations. An architecture is represented
27189 by an instance of the @code{gdb.Architecture} class.
27191 A @code{gdb.Architecture} class has the following methods:
27193 @defun Architecture.name ()
27194 Return the name (string value) of the architecture.
27197 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27198 Return a list of disassembled instructions starting from the memory
27199 address @var{start_pc}. The optional arguments @var{end_pc} and
27200 @var{count} determine the number of instructions in the returned list.
27201 If both the optional arguments @var{end_pc} and @var{count} are
27202 specified, then a list of at most @var{count} disassembled instructions
27203 whose start address falls in the closed memory address interval from
27204 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27205 specified, but @var{count} is specified, then @var{count} number of
27206 instructions starting from the address @var{start_pc} are returned. If
27207 @var{count} is not specified but @var{end_pc} is specified, then all
27208 instructions whose start address falls in the closed memory address
27209 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27210 @var{end_pc} nor @var{count} are specified, then a single instruction at
27211 @var{start_pc} is returned. For all of these cases, each element of the
27212 returned list is a Python @code{dict} with the following string keys:
27217 The value corresponding to this key is a Python long integer capturing
27218 the memory address of the instruction.
27221 The value corresponding to this key is a string value which represents
27222 the instruction with assembly language mnemonics. The assembly
27223 language flavor used is the same as that specified by the current CLI
27224 variable @code{disassembly-flavor}. @xref{Machine Code}.
27227 The value corresponding to this key is the length (integer value) of the
27228 instruction in bytes.
27233 @node Python Auto-loading
27234 @subsection Python Auto-loading
27235 @cindex Python auto-loading
27237 When a new object file is read (for example, due to the @code{file}
27238 command, or because the inferior has loaded a shared library),
27239 @value{GDBN} will look for Python support scripts in several ways:
27240 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
27241 and @code{.debug_gdb_scripts} section
27242 (@pxref{dotdebug_gdb_scripts section}).
27244 The auto-loading feature is useful for supplying application-specific
27245 debugging commands and scripts.
27247 Auto-loading can be enabled or disabled,
27248 and the list of auto-loaded scripts can be printed.
27251 @anchor{set auto-load python-scripts}
27252 @kindex set auto-load python-scripts
27253 @item set auto-load python-scripts [on|off]
27254 Enable or disable the auto-loading of Python scripts.
27256 @anchor{show auto-load python-scripts}
27257 @kindex show auto-load python-scripts
27258 @item show auto-load python-scripts
27259 Show whether auto-loading of Python scripts is enabled or disabled.
27261 @anchor{info auto-load python-scripts}
27262 @kindex info auto-load python-scripts
27263 @cindex print list of auto-loaded Python scripts
27264 @item info auto-load python-scripts [@var{regexp}]
27265 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27267 Also printed is the list of Python scripts that were mentioned in
27268 the @code{.debug_gdb_scripts} section and were not found
27269 (@pxref{dotdebug_gdb_scripts section}).
27270 This is useful because their names are not printed when @value{GDBN}
27271 tries to load them and fails. There may be many of them, and printing
27272 an error message for each one is problematic.
27274 If @var{regexp} is supplied only Python scripts with matching names are printed.
27279 (gdb) info auto-load python-scripts
27281 Yes py-section-script.py
27282 full name: /tmp/py-section-script.py
27283 No my-foo-pretty-printers.py
27287 When reading an auto-loaded file, @value{GDBN} sets the
27288 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27289 function (@pxref{Objfiles In Python}). This can be useful for
27290 registering objfile-specific pretty-printers and frame-filters.
27293 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
27294 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27295 * Which flavor to choose?::
27298 @node objfile-gdb.py file
27299 @subsubsection The @file{@var{objfile}-gdb.py} file
27300 @cindex @file{@var{objfile}-gdb.py}
27302 When a new object file is read, @value{GDBN} looks for
27303 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
27304 where @var{objfile} is the object file's real name, formed by ensuring
27305 that the file name is absolute, following all symlinks, and resolving
27306 @code{.} and @code{..} components. If this file exists and is
27307 readable, @value{GDBN} will evaluate it as a Python script.
27309 If this file does not exist, then @value{GDBN} will look for
27310 @var{script-name} file in all of the directories as specified below.
27312 Note that loading of this script file also requires accordingly configured
27313 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27315 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27316 scripts normally according to its @file{.exe} filename. But if no scripts are
27317 found @value{GDBN} also tries script filenames matching the object file without
27318 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27319 is attempted on any platform. This makes the script filenames compatible
27320 between Unix and MS-Windows hosts.
27323 @anchor{set auto-load scripts-directory}
27324 @kindex set auto-load scripts-directory
27325 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27326 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27327 may be delimited by the host platform path separator in use
27328 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27330 Each entry here needs to be covered also by the security setting
27331 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27333 @anchor{with-auto-load-dir}
27334 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27335 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27336 configuration option @option{--with-auto-load-dir}.
27338 Any reference to @file{$debugdir} will get replaced by
27339 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27340 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27341 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27342 @file{$datadir} must be placed as a directory component --- either alone or
27343 delimited by @file{/} or @file{\} directory separators, depending on the host
27346 The list of directories uses path separator (@samp{:} on GNU and Unix
27347 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27348 to the @env{PATH} environment variable.
27350 @anchor{show auto-load scripts-directory}
27351 @kindex show auto-load scripts-directory
27352 @item show auto-load scripts-directory
27353 Show @value{GDBN} auto-loaded scripts location.
27356 @value{GDBN} does not track which files it has already auto-loaded this way.
27357 @value{GDBN} will load the associated script every time the corresponding
27358 @var{objfile} is opened.
27359 So your @file{-gdb.py} file should be careful to avoid errors if it
27360 is evaluated more than once.
27362 @node dotdebug_gdb_scripts section
27363 @subsubsection The @code{.debug_gdb_scripts} section
27364 @cindex @code{.debug_gdb_scripts} section
27366 For systems using file formats like ELF and COFF,
27367 when @value{GDBN} loads a new object file
27368 it will look for a special section named @samp{.debug_gdb_scripts}.
27369 If this section exists, its contents is a list of names of scripts to load.
27371 @value{GDBN} will look for each specified script file first in the
27372 current directory and then along the source search path
27373 (@pxref{Source Path, ,Specifying Source Directories}),
27374 except that @file{$cdir} is not searched, since the compilation
27375 directory is not relevant to scripts.
27377 Entries can be placed in section @code{.debug_gdb_scripts} with,
27378 for example, this GCC macro:
27381 /* Note: The "MS" section flags are to remove duplicates. */
27382 #define DEFINE_GDB_SCRIPT(script_name) \
27384 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27386 .asciz \"" script_name "\"\n\
27392 Then one can reference the macro in a header or source file like this:
27395 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
27398 The script name may include directories if desired.
27400 Note that loading of this script file also requires accordingly configured
27401 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27403 If the macro is put in a header, any application or library
27404 using this header will get a reference to the specified script.
27406 @node Which flavor to choose?
27407 @subsubsection Which flavor to choose?
27409 Given the multiple ways of auto-loading Python scripts, it might not always
27410 be clear which one to choose. This section provides some guidance.
27412 Benefits of the @file{-gdb.py} way:
27416 Can be used with file formats that don't support multiple sections.
27419 Ease of finding scripts for public libraries.
27421 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27422 in the source search path.
27423 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27424 isn't a source directory in which to find the script.
27427 Doesn't require source code additions.
27430 Benefits of the @code{.debug_gdb_scripts} way:
27434 Works with static linking.
27436 Scripts for libraries done the @file{-gdb.py} way require an objfile to
27437 trigger their loading. When an application is statically linked the only
27438 objfile available is the executable, and it is cumbersome to attach all the
27439 scripts from all the input libraries to the executable's @file{-gdb.py} script.
27442 Works with classes that are entirely inlined.
27444 Some classes can be entirely inlined, and thus there may not be an associated
27445 shared library to attach a @file{-gdb.py} script to.
27448 Scripts needn't be copied out of the source tree.
27450 In some circumstances, apps can be built out of large collections of internal
27451 libraries, and the build infrastructure necessary to install the
27452 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
27453 cumbersome. It may be easier to specify the scripts in the
27454 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27455 top of the source tree to the source search path.
27458 @node Python modules
27459 @subsection Python modules
27460 @cindex python modules
27462 @value{GDBN} comes with several modules to assist writing Python code.
27465 * gdb.printing:: Building and registering pretty-printers.
27466 * gdb.types:: Utilities for working with types.
27467 * gdb.prompt:: Utilities for prompt value substitution.
27471 @subsubsection gdb.printing
27472 @cindex gdb.printing
27474 This module provides a collection of utilities for working with
27478 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27479 This class specifies the API that makes @samp{info pretty-printer},
27480 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27481 Pretty-printers should generally inherit from this class.
27483 @item SubPrettyPrinter (@var{name})
27484 For printers that handle multiple types, this class specifies the
27485 corresponding API for the subprinters.
27487 @item RegexpCollectionPrettyPrinter (@var{name})
27488 Utility class for handling multiple printers, all recognized via
27489 regular expressions.
27490 @xref{Writing a Pretty-Printer}, for an example.
27492 @item FlagEnumerationPrinter (@var{name})
27493 A pretty-printer which handles printing of @code{enum} values. Unlike
27494 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27495 work properly when there is some overlap between the enumeration
27496 constants. @var{name} is the name of the printer and also the name of
27497 the @code{enum} type to look up.
27499 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27500 Register @var{printer} with the pretty-printer list of @var{obj}.
27501 If @var{replace} is @code{True} then any existing copy of the printer
27502 is replaced. Otherwise a @code{RuntimeError} exception is raised
27503 if a printer with the same name already exists.
27507 @subsubsection gdb.types
27510 This module provides a collection of utilities for working with
27511 @code{gdb.Type} objects.
27514 @item get_basic_type (@var{type})
27515 Return @var{type} with const and volatile qualifiers stripped,
27516 and with typedefs and C@t{++} references converted to the underlying type.
27521 typedef const int const_int;
27523 const_int& foo_ref (foo);
27524 int main () @{ return 0; @}
27531 (gdb) python import gdb.types
27532 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27533 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27537 @item has_field (@var{type}, @var{field})
27538 Return @code{True} if @var{type}, assumed to be a type with fields
27539 (e.g., a structure or union), has field @var{field}.
27541 @item make_enum_dict (@var{enum_type})
27542 Return a Python @code{dictionary} type produced from @var{enum_type}.
27544 @item deep_items (@var{type})
27545 Returns a Python iterator similar to the standard
27546 @code{gdb.Type.iteritems} method, except that the iterator returned
27547 by @code{deep_items} will recursively traverse anonymous struct or
27548 union fields. For example:
27562 Then in @value{GDBN}:
27564 (@value{GDBP}) python import gdb.types
27565 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27566 (@value{GDBP}) python print struct_a.keys ()
27568 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27569 @{['a', 'b0', 'b1']@}
27572 @item get_type_recognizers ()
27573 Return a list of the enabled type recognizers for the current context.
27574 This is called by @value{GDBN} during the type-printing process
27575 (@pxref{Type Printing API}).
27577 @item apply_type_recognizers (recognizers, type_obj)
27578 Apply the type recognizers, @var{recognizers}, to the type object
27579 @var{type_obj}. If any recognizer returns a string, return that
27580 string. Otherwise, return @code{None}. This is called by
27581 @value{GDBN} during the type-printing process (@pxref{Type Printing
27584 @item register_type_printer (locus, printer)
27585 This is a convenience function to register a type printer.
27586 @var{printer} is the type printer to register. It must implement the
27587 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27588 which case the printer is registered with that objfile; a
27589 @code{gdb.Progspace}, in which case the printer is registered with
27590 that progspace; or @code{None}, in which case the printer is
27591 registered globally.
27594 This is a base class that implements the type printer protocol. Type
27595 printers are encouraged, but not required, to derive from this class.
27596 It defines a constructor:
27598 @defmethod TypePrinter __init__ (self, name)
27599 Initialize the type printer with the given name. The new printer
27600 starts in the enabled state.
27606 @subsubsection gdb.prompt
27609 This module provides a method for prompt value-substitution.
27612 @item substitute_prompt (@var{string})
27613 Return @var{string} with escape sequences substituted by values. Some
27614 escape sequences take arguments. You can specify arguments inside
27615 ``@{@}'' immediately following the escape sequence.
27617 The escape sequences you can pass to this function are:
27621 Substitute a backslash.
27623 Substitute an ESC character.
27625 Substitute the selected frame; an argument names a frame parameter.
27627 Substitute a newline.
27629 Substitute a parameter's value; the argument names the parameter.
27631 Substitute a carriage return.
27633 Substitute the selected thread; an argument names a thread parameter.
27635 Substitute the version of GDB.
27637 Substitute the current working directory.
27639 Begin a sequence of non-printing characters. These sequences are
27640 typically used with the ESC character, and are not counted in the string
27641 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27642 blue-colored ``(gdb)'' prompt where the length is five.
27644 End a sequence of non-printing characters.
27650 substitute_prompt (``frame: \f,
27651 print arguments: \p@{print frame-arguments@}'')
27654 @exdent will return the string:
27657 "frame: main, print arguments: scalars"
27662 @section Creating new spellings of existing commands
27663 @cindex aliases for commands
27665 It is often useful to define alternate spellings of existing commands.
27666 For example, if a new @value{GDBN} command defined in Python has
27667 a long name to type, it is handy to have an abbreviated version of it
27668 that involves less typing.
27670 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27671 of the @samp{step} command even though it is otherwise an ambiguous
27672 abbreviation of other commands like @samp{set} and @samp{show}.
27674 Aliases are also used to provide shortened or more common versions
27675 of multi-word commands. For example, @value{GDBN} provides the
27676 @samp{tty} alias of the @samp{set inferior-tty} command.
27678 You can define a new alias with the @samp{alias} command.
27683 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
27687 @var{ALIAS} specifies the name of the new alias.
27688 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
27691 @var{COMMAND} specifies the name of an existing command
27692 that is being aliased.
27694 The @samp{-a} option specifies that the new alias is an abbreviation
27695 of the command. Abbreviations are not shown in command
27696 lists displayed by the @samp{help} command.
27698 The @samp{--} option specifies the end of options,
27699 and is useful when @var{ALIAS} begins with a dash.
27701 Here is a simple example showing how to make an abbreviation
27702 of a command so that there is less to type.
27703 Suppose you were tired of typing @samp{disas}, the current
27704 shortest unambiguous abbreviation of the @samp{disassemble} command
27705 and you wanted an even shorter version named @samp{di}.
27706 The following will accomplish this.
27709 (gdb) alias -a di = disas
27712 Note that aliases are different from user-defined commands.
27713 With a user-defined command, you also need to write documentation
27714 for it with the @samp{document} command.
27715 An alias automatically picks up the documentation of the existing command.
27717 Here is an example where we make @samp{elms} an abbreviation of
27718 @samp{elements} in the @samp{set print elements} command.
27719 This is to show that you can make an abbreviation of any part
27723 (gdb) alias -a set print elms = set print elements
27724 (gdb) alias -a show print elms = show print elements
27725 (gdb) set p elms 20
27727 Limit on string chars or array elements to print is 200.
27730 Note that if you are defining an alias of a @samp{set} command,
27731 and you want to have an alias for the corresponding @samp{show}
27732 command, then you need to define the latter separately.
27734 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
27735 @var{ALIAS}, just as they are normally.
27738 (gdb) alias -a set pr elms = set p ele
27741 Finally, here is an example showing the creation of a one word
27742 alias for a more complex command.
27743 This creates alias @samp{spe} of the command @samp{set print elements}.
27746 (gdb) alias spe = set print elements
27751 @chapter Command Interpreters
27752 @cindex command interpreters
27754 @value{GDBN} supports multiple command interpreters, and some command
27755 infrastructure to allow users or user interface writers to switch
27756 between interpreters or run commands in other interpreters.
27758 @value{GDBN} currently supports two command interpreters, the console
27759 interpreter (sometimes called the command-line interpreter or @sc{cli})
27760 and the machine interface interpreter (or @sc{gdb/mi}). This manual
27761 describes both of these interfaces in great detail.
27763 By default, @value{GDBN} will start with the console interpreter.
27764 However, the user may choose to start @value{GDBN} with another
27765 interpreter by specifying the @option{-i} or @option{--interpreter}
27766 startup options. Defined interpreters include:
27770 @cindex console interpreter
27771 The traditional console or command-line interpreter. This is the most often
27772 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
27773 @value{GDBN} will use this interpreter.
27776 @cindex mi interpreter
27777 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
27778 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
27779 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
27783 @cindex mi2 interpreter
27784 The current @sc{gdb/mi} interface.
27787 @cindex mi1 interpreter
27788 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
27792 @cindex invoke another interpreter
27793 The interpreter being used by @value{GDBN} may not be dynamically
27794 switched at runtime. Although possible, this could lead to a very
27795 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
27796 enters the command "interpreter-set console" in a console view,
27797 @value{GDBN} would switch to using the console interpreter, rendering
27798 the IDE inoperable!
27800 @kindex interpreter-exec
27801 Although you may only choose a single interpreter at startup, you may execute
27802 commands in any interpreter from the current interpreter using the appropriate
27803 command. If you are running the console interpreter, simply use the
27804 @code{interpreter-exec} command:
27807 interpreter-exec mi "-data-list-register-names"
27810 @sc{gdb/mi} has a similar command, although it is only available in versions of
27811 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
27814 @chapter @value{GDBN} Text User Interface
27816 @cindex Text User Interface
27819 * TUI Overview:: TUI overview
27820 * TUI Keys:: TUI key bindings
27821 * TUI Single Key Mode:: TUI single key mode
27822 * TUI Commands:: TUI-specific commands
27823 * TUI Configuration:: TUI configuration variables
27826 The @value{GDBN} Text User Interface (TUI) is a terminal
27827 interface which uses the @code{curses} library to show the source
27828 file, the assembly output, the program registers and @value{GDBN}
27829 commands in separate text windows. The TUI mode is supported only
27830 on platforms where a suitable version of the @code{curses} library
27833 The TUI mode is enabled by default when you invoke @value{GDBN} as
27834 @samp{@value{GDBP} -tui}.
27835 You can also switch in and out of TUI mode while @value{GDBN} runs by
27836 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
27837 @xref{TUI Keys, ,TUI Key Bindings}.
27840 @section TUI Overview
27842 In TUI mode, @value{GDBN} can display several text windows:
27846 This window is the @value{GDBN} command window with the @value{GDBN}
27847 prompt and the @value{GDBN} output. The @value{GDBN} input is still
27848 managed using readline.
27851 The source window shows the source file of the program. The current
27852 line and active breakpoints are displayed in this window.
27855 The assembly window shows the disassembly output of the program.
27858 This window shows the processor registers. Registers are highlighted
27859 when their values change.
27862 The source and assembly windows show the current program position
27863 by highlighting the current line and marking it with a @samp{>} marker.
27864 Breakpoints are indicated with two markers. The first marker
27865 indicates the breakpoint type:
27869 Breakpoint which was hit at least once.
27872 Breakpoint which was never hit.
27875 Hardware breakpoint which was hit at least once.
27878 Hardware breakpoint which was never hit.
27881 The second marker indicates whether the breakpoint is enabled or not:
27885 Breakpoint is enabled.
27888 Breakpoint is disabled.
27891 The source, assembly and register windows are updated when the current
27892 thread changes, when the frame changes, or when the program counter
27895 These windows are not all visible at the same time. The command
27896 window is always visible. The others can be arranged in several
27907 source and assembly,
27910 source and registers, or
27913 assembly and registers.
27916 A status line above the command window shows the following information:
27920 Indicates the current @value{GDBN} target.
27921 (@pxref{Targets, ,Specifying a Debugging Target}).
27924 Gives the current process or thread number.
27925 When no process is being debugged, this field is set to @code{No process}.
27928 Gives the current function name for the selected frame.
27929 The name is demangled if demangling is turned on (@pxref{Print Settings}).
27930 When there is no symbol corresponding to the current program counter,
27931 the string @code{??} is displayed.
27934 Indicates the current line number for the selected frame.
27935 When the current line number is not known, the string @code{??} is displayed.
27938 Indicates the current program counter address.
27942 @section TUI Key Bindings
27943 @cindex TUI key bindings
27945 The TUI installs several key bindings in the readline keymaps
27946 @ifset SYSTEM_READLINE
27947 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
27949 @ifclear SYSTEM_READLINE
27950 (@pxref{Command Line Editing}).
27952 The following key bindings are installed for both TUI mode and the
27953 @value{GDBN} standard mode.
27962 Enter or leave the TUI mode. When leaving the TUI mode,
27963 the curses window management stops and @value{GDBN} operates using
27964 its standard mode, writing on the terminal directly. When reentering
27965 the TUI mode, control is given back to the curses windows.
27966 The screen is then refreshed.
27970 Use a TUI layout with only one window. The layout will
27971 either be @samp{source} or @samp{assembly}. When the TUI mode
27972 is not active, it will switch to the TUI mode.
27974 Think of this key binding as the Emacs @kbd{C-x 1} binding.
27978 Use a TUI layout with at least two windows. When the current
27979 layout already has two windows, the next layout with two windows is used.
27980 When a new layout is chosen, one window will always be common to the
27981 previous layout and the new one.
27983 Think of it as the Emacs @kbd{C-x 2} binding.
27987 Change the active window. The TUI associates several key bindings
27988 (like scrolling and arrow keys) with the active window. This command
27989 gives the focus to the next TUI window.
27991 Think of it as the Emacs @kbd{C-x o} binding.
27995 Switch in and out of the TUI SingleKey mode that binds single
27996 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
27999 The following key bindings only work in the TUI mode:
28004 Scroll the active window one page up.
28008 Scroll the active window one page down.
28012 Scroll the active window one line up.
28016 Scroll the active window one line down.
28020 Scroll the active window one column left.
28024 Scroll the active window one column right.
28028 Refresh the screen.
28031 Because the arrow keys scroll the active window in the TUI mode, they
28032 are not available for their normal use by readline unless the command
28033 window has the focus. When another window is active, you must use
28034 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
28035 and @kbd{C-f} to control the command window.
28037 @node TUI Single Key Mode
28038 @section TUI Single Key Mode
28039 @cindex TUI single key mode
28041 The TUI also provides a @dfn{SingleKey} mode, which binds several
28042 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
28043 switch into this mode, where the following key bindings are used:
28046 @kindex c @r{(SingleKey TUI key)}
28050 @kindex d @r{(SingleKey TUI key)}
28054 @kindex f @r{(SingleKey TUI key)}
28058 @kindex n @r{(SingleKey TUI key)}
28062 @kindex q @r{(SingleKey TUI key)}
28064 exit the SingleKey mode.
28066 @kindex r @r{(SingleKey TUI key)}
28070 @kindex s @r{(SingleKey TUI key)}
28074 @kindex u @r{(SingleKey TUI key)}
28078 @kindex v @r{(SingleKey TUI key)}
28082 @kindex w @r{(SingleKey TUI key)}
28087 Other keys temporarily switch to the @value{GDBN} command prompt.
28088 The key that was pressed is inserted in the editing buffer so that
28089 it is possible to type most @value{GDBN} commands without interaction
28090 with the TUI SingleKey mode. Once the command is entered the TUI
28091 SingleKey mode is restored. The only way to permanently leave
28092 this mode is by typing @kbd{q} or @kbd{C-x s}.
28096 @section TUI-specific Commands
28097 @cindex TUI commands
28099 The TUI has specific commands to control the text windows.
28100 These commands are always available, even when @value{GDBN} is not in
28101 the TUI mode. When @value{GDBN} is in the standard mode, most
28102 of these commands will automatically switch to the TUI mode.
28104 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28105 terminal, or @value{GDBN} has been started with the machine interface
28106 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28107 these commands will fail with an error, because it would not be
28108 possible or desirable to enable curses window management.
28113 List and give the size of all displayed windows.
28117 Display the next layout.
28120 Display the previous layout.
28123 Display the source window only.
28126 Display the assembly window only.
28129 Display the source and assembly window.
28132 Display the register window together with the source or assembly window.
28136 Make the next window active for scrolling.
28139 Make the previous window active for scrolling.
28142 Make the source window active for scrolling.
28145 Make the assembly window active for scrolling.
28148 Make the register window active for scrolling.
28151 Make the command window active for scrolling.
28155 Refresh the screen. This is similar to typing @kbd{C-L}.
28157 @item tui reg float
28159 Show the floating point registers in the register window.
28161 @item tui reg general
28162 Show the general registers in the register window.
28165 Show the next register group. The list of register groups as well as
28166 their order is target specific. The predefined register groups are the
28167 following: @code{general}, @code{float}, @code{system}, @code{vector},
28168 @code{all}, @code{save}, @code{restore}.
28170 @item tui reg system
28171 Show the system registers in the register window.
28175 Update the source window and the current execution point.
28177 @item winheight @var{name} +@var{count}
28178 @itemx winheight @var{name} -@var{count}
28180 Change the height of the window @var{name} by @var{count}
28181 lines. Positive counts increase the height, while negative counts
28184 @item tabset @var{nchars}
28186 Set the width of tab stops to be @var{nchars} characters.
28189 @node TUI Configuration
28190 @section TUI Configuration Variables
28191 @cindex TUI configuration variables
28193 Several configuration variables control the appearance of TUI windows.
28196 @item set tui border-kind @var{kind}
28197 @kindex set tui border-kind
28198 Select the border appearance for the source, assembly and register windows.
28199 The possible values are the following:
28202 Use a space character to draw the border.
28205 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28208 Use the Alternate Character Set to draw the border. The border is
28209 drawn using character line graphics if the terminal supports them.
28212 @item set tui border-mode @var{mode}
28213 @kindex set tui border-mode
28214 @itemx set tui active-border-mode @var{mode}
28215 @kindex set tui active-border-mode
28216 Select the display attributes for the borders of the inactive windows
28217 or the active window. The @var{mode} can be one of the following:
28220 Use normal attributes to display the border.
28226 Use reverse video mode.
28229 Use half bright mode.
28231 @item half-standout
28232 Use half bright and standout mode.
28235 Use extra bright or bold mode.
28237 @item bold-standout
28238 Use extra bright or bold and standout mode.
28243 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28246 @cindex @sc{gnu} Emacs
28247 A special interface allows you to use @sc{gnu} Emacs to view (and
28248 edit) the source files for the program you are debugging with
28251 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28252 executable file you want to debug as an argument. This command starts
28253 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28254 created Emacs buffer.
28255 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28257 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28262 All ``terminal'' input and output goes through an Emacs buffer, called
28265 This applies both to @value{GDBN} commands and their output, and to the input
28266 and output done by the program you are debugging.
28268 This is useful because it means that you can copy the text of previous
28269 commands and input them again; you can even use parts of the output
28272 All the facilities of Emacs' Shell mode are available for interacting
28273 with your program. In particular, you can send signals the usual
28274 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28278 @value{GDBN} displays source code through Emacs.
28280 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28281 source file for that frame and puts an arrow (@samp{=>}) at the
28282 left margin of the current line. Emacs uses a separate buffer for
28283 source display, and splits the screen to show both your @value{GDBN} session
28286 Explicit @value{GDBN} @code{list} or search commands still produce output as
28287 usual, but you probably have no reason to use them from Emacs.
28290 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28291 a graphical mode, enabled by default, which provides further buffers
28292 that can control the execution and describe the state of your program.
28293 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28295 If you specify an absolute file name when prompted for the @kbd{M-x
28296 gdb} argument, then Emacs sets your current working directory to where
28297 your program resides. If you only specify the file name, then Emacs
28298 sets your current working directory to the directory associated
28299 with the previous buffer. In this case, @value{GDBN} may find your
28300 program by searching your environment's @code{PATH} variable, but on
28301 some operating systems it might not find the source. So, although the
28302 @value{GDBN} input and output session proceeds normally, the auxiliary
28303 buffer does not display the current source and line of execution.
28305 The initial working directory of @value{GDBN} is printed on the top
28306 line of the GUD buffer and this serves as a default for the commands
28307 that specify files for @value{GDBN} to operate on. @xref{Files,
28308 ,Commands to Specify Files}.
28310 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28311 need to call @value{GDBN} by a different name (for example, if you
28312 keep several configurations around, with different names) you can
28313 customize the Emacs variable @code{gud-gdb-command-name} to run the
28316 In the GUD buffer, you can use these special Emacs commands in
28317 addition to the standard Shell mode commands:
28321 Describe the features of Emacs' GUD Mode.
28324 Execute to another source line, like the @value{GDBN} @code{step} command; also
28325 update the display window to show the current file and location.
28328 Execute to next source line in this function, skipping all function
28329 calls, like the @value{GDBN} @code{next} command. Then update the display window
28330 to show the current file and location.
28333 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28334 display window accordingly.
28337 Execute until exit from the selected stack frame, like the @value{GDBN}
28338 @code{finish} command.
28341 Continue execution of your program, like the @value{GDBN} @code{continue}
28345 Go up the number of frames indicated by the numeric argument
28346 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28347 like the @value{GDBN} @code{up} command.
28350 Go down the number of frames indicated by the numeric argument, like the
28351 @value{GDBN} @code{down} command.
28354 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28355 tells @value{GDBN} to set a breakpoint on the source line point is on.
28357 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28358 separate frame which shows a backtrace when the GUD buffer is current.
28359 Move point to any frame in the stack and type @key{RET} to make it
28360 become the current frame and display the associated source in the
28361 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28362 selected frame become the current one. In graphical mode, the
28363 speedbar displays watch expressions.
28365 If you accidentally delete the source-display buffer, an easy way to get
28366 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28367 request a frame display; when you run under Emacs, this recreates
28368 the source buffer if necessary to show you the context of the current
28371 The source files displayed in Emacs are in ordinary Emacs buffers
28372 which are visiting the source files in the usual way. You can edit
28373 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28374 communicates with Emacs in terms of line numbers. If you add or
28375 delete lines from the text, the line numbers that @value{GDBN} knows cease
28376 to correspond properly with the code.
28378 A more detailed description of Emacs' interaction with @value{GDBN} is
28379 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28383 @chapter The @sc{gdb/mi} Interface
28385 @unnumberedsec Function and Purpose
28387 @cindex @sc{gdb/mi}, its purpose
28388 @sc{gdb/mi} is a line based machine oriented text interface to
28389 @value{GDBN} and is activated by specifying using the
28390 @option{--interpreter} command line option (@pxref{Mode Options}). It
28391 is specifically intended to support the development of systems which
28392 use the debugger as just one small component of a larger system.
28394 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28395 in the form of a reference manual.
28397 Note that @sc{gdb/mi} is still under construction, so some of the
28398 features described below are incomplete and subject to change
28399 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28401 @unnumberedsec Notation and Terminology
28403 @cindex notational conventions, for @sc{gdb/mi}
28404 This chapter uses the following notation:
28408 @code{|} separates two alternatives.
28411 @code{[ @var{something} ]} indicates that @var{something} is optional:
28412 it may or may not be given.
28415 @code{( @var{group} )*} means that @var{group} inside the parentheses
28416 may repeat zero or more times.
28419 @code{( @var{group} )+} means that @var{group} inside the parentheses
28420 may repeat one or more times.
28423 @code{"@var{string}"} means a literal @var{string}.
28427 @heading Dependencies
28431 * GDB/MI General Design::
28432 * GDB/MI Command Syntax::
28433 * GDB/MI Compatibility with CLI::
28434 * GDB/MI Development and Front Ends::
28435 * GDB/MI Output Records::
28436 * GDB/MI Simple Examples::
28437 * GDB/MI Command Description Format::
28438 * GDB/MI Breakpoint Commands::
28439 * GDB/MI Catchpoint Commands::
28440 * GDB/MI Program Context::
28441 * GDB/MI Thread Commands::
28442 * GDB/MI Ada Tasking Commands::
28443 * GDB/MI Program Execution::
28444 * GDB/MI Stack Manipulation::
28445 * GDB/MI Variable Objects::
28446 * GDB/MI Data Manipulation::
28447 * GDB/MI Tracepoint Commands::
28448 * GDB/MI Symbol Query::
28449 * GDB/MI File Commands::
28451 * GDB/MI Kod Commands::
28452 * GDB/MI Memory Overlay Commands::
28453 * GDB/MI Signal Handling Commands::
28455 * GDB/MI Target Manipulation::
28456 * GDB/MI File Transfer Commands::
28457 * GDB/MI Miscellaneous Commands::
28460 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28461 @node GDB/MI General Design
28462 @section @sc{gdb/mi} General Design
28463 @cindex GDB/MI General Design
28465 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28466 parts---commands sent to @value{GDBN}, responses to those commands
28467 and notifications. Each command results in exactly one response,
28468 indicating either successful completion of the command, or an error.
28469 For the commands that do not resume the target, the response contains the
28470 requested information. For the commands that resume the target, the
28471 response only indicates whether the target was successfully resumed.
28472 Notifications is the mechanism for reporting changes in the state of the
28473 target, or in @value{GDBN} state, that cannot conveniently be associated with
28474 a command and reported as part of that command response.
28476 The important examples of notifications are:
28480 Exec notifications. These are used to report changes in
28481 target state---when a target is resumed, or stopped. It would not
28482 be feasible to include this information in response of resuming
28483 commands, because one resume commands can result in multiple events in
28484 different threads. Also, quite some time may pass before any event
28485 happens in the target, while a frontend needs to know whether the resuming
28486 command itself was successfully executed.
28489 Console output, and status notifications. Console output
28490 notifications are used to report output of CLI commands, as well as
28491 diagnostics for other commands. Status notifications are used to
28492 report the progress of a long-running operation. Naturally, including
28493 this information in command response would mean no output is produced
28494 until the command is finished, which is undesirable.
28497 General notifications. Commands may have various side effects on
28498 the @value{GDBN} or target state beyond their official purpose. For example,
28499 a command may change the selected thread. Although such changes can
28500 be included in command response, using notification allows for more
28501 orthogonal frontend design.
28505 There's no guarantee that whenever an MI command reports an error,
28506 @value{GDBN} or the target are in any specific state, and especially,
28507 the state is not reverted to the state before the MI command was
28508 processed. Therefore, whenever an MI command results in an error,
28509 we recommend that the frontend refreshes all the information shown in
28510 the user interface.
28514 * Context management::
28515 * Asynchronous and non-stop modes::
28519 @node Context management
28520 @subsection Context management
28522 In most cases when @value{GDBN} accesses the target, this access is
28523 done in context of a specific thread and frame (@pxref{Frames}).
28524 Often, even when accessing global data, the target requires that a thread
28525 be specified. The CLI interface maintains the selected thread and frame,
28526 and supplies them to target on each command. This is convenient,
28527 because a command line user would not want to specify that information
28528 explicitly on each command, and because user interacts with
28529 @value{GDBN} via a single terminal, so no confusion is possible as
28530 to what thread and frame are the current ones.
28532 In the case of MI, the concept of selected thread and frame is less
28533 useful. First, a frontend can easily remember this information
28534 itself. Second, a graphical frontend can have more than one window,
28535 each one used for debugging a different thread, and the frontend might
28536 want to access additional threads for internal purposes. This
28537 increases the risk that by relying on implicitly selected thread, the
28538 frontend may be operating on a wrong one. Therefore, each MI command
28539 should explicitly specify which thread and frame to operate on. To
28540 make it possible, each MI command accepts the @samp{--thread} and
28541 @samp{--frame} options, the value to each is @value{GDBN} identifier
28542 for thread and frame to operate on.
28544 Usually, each top-level window in a frontend allows the user to select
28545 a thread and a frame, and remembers the user selection for further
28546 operations. However, in some cases @value{GDBN} may suggest that the
28547 current thread be changed. For example, when stopping on a breakpoint
28548 it is reasonable to switch to the thread where breakpoint is hit. For
28549 another example, if the user issues the CLI @samp{thread} command via
28550 the frontend, it is desirable to change the frontend's selected thread to the
28551 one specified by user. @value{GDBN} communicates the suggestion to
28552 change current thread using the @samp{=thread-selected} notification.
28553 No such notification is available for the selected frame at the moment.
28555 Note that historically, MI shares the selected thread with CLI, so
28556 frontends used the @code{-thread-select} to execute commands in the
28557 right context. However, getting this to work right is cumbersome. The
28558 simplest way is for frontend to emit @code{-thread-select} command
28559 before every command. This doubles the number of commands that need
28560 to be sent. The alternative approach is to suppress @code{-thread-select}
28561 if the selected thread in @value{GDBN} is supposed to be identical to the
28562 thread the frontend wants to operate on. However, getting this
28563 optimization right can be tricky. In particular, if the frontend
28564 sends several commands to @value{GDBN}, and one of the commands changes the
28565 selected thread, then the behaviour of subsequent commands will
28566 change. So, a frontend should either wait for response from such
28567 problematic commands, or explicitly add @code{-thread-select} for
28568 all subsequent commands. No frontend is known to do this exactly
28569 right, so it is suggested to just always pass the @samp{--thread} and
28570 @samp{--frame} options.
28572 @node Asynchronous and non-stop modes
28573 @subsection Asynchronous command execution and non-stop mode
28575 On some targets, @value{GDBN} is capable of processing MI commands
28576 even while the target is running. This is called @dfn{asynchronous
28577 command execution} (@pxref{Background Execution}). The frontend may
28578 specify a preferrence for asynchronous execution using the
28579 @code{-gdb-set target-async 1} command, which should be emitted before
28580 either running the executable or attaching to the target. After the
28581 frontend has started the executable or attached to the target, it can
28582 find if asynchronous execution is enabled using the
28583 @code{-list-target-features} command.
28585 Even if @value{GDBN} can accept a command while target is running,
28586 many commands that access the target do not work when the target is
28587 running. Therefore, asynchronous command execution is most useful
28588 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28589 it is possible to examine the state of one thread, while other threads
28592 When a given thread is running, MI commands that try to access the
28593 target in the context of that thread may not work, or may work only on
28594 some targets. In particular, commands that try to operate on thread's
28595 stack will not work, on any target. Commands that read memory, or
28596 modify breakpoints, may work or not work, depending on the target. Note
28597 that even commands that operate on global state, such as @code{print},
28598 @code{set}, and breakpoint commands, still access the target in the
28599 context of a specific thread, so frontend should try to find a
28600 stopped thread and perform the operation on that thread (using the
28601 @samp{--thread} option).
28603 Which commands will work in the context of a running thread is
28604 highly target dependent. However, the two commands
28605 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28606 to find the state of a thread, will always work.
28608 @node Thread groups
28609 @subsection Thread groups
28610 @value{GDBN} may be used to debug several processes at the same time.
28611 On some platfroms, @value{GDBN} may support debugging of several
28612 hardware systems, each one having several cores with several different
28613 processes running on each core. This section describes the MI
28614 mechanism to support such debugging scenarios.
28616 The key observation is that regardless of the structure of the
28617 target, MI can have a global list of threads, because most commands that
28618 accept the @samp{--thread} option do not need to know what process that
28619 thread belongs to. Therefore, it is not necessary to introduce
28620 neither additional @samp{--process} option, nor an notion of the
28621 current process in the MI interface. The only strictly new feature
28622 that is required is the ability to find how the threads are grouped
28625 To allow the user to discover such grouping, and to support arbitrary
28626 hierarchy of machines/cores/processes, MI introduces the concept of a
28627 @dfn{thread group}. Thread group is a collection of threads and other
28628 thread groups. A thread group always has a string identifier, a type,
28629 and may have additional attributes specific to the type. A new
28630 command, @code{-list-thread-groups}, returns the list of top-level
28631 thread groups, which correspond to processes that @value{GDBN} is
28632 debugging at the moment. By passing an identifier of a thread group
28633 to the @code{-list-thread-groups} command, it is possible to obtain
28634 the members of specific thread group.
28636 To allow the user to easily discover processes, and other objects, he
28637 wishes to debug, a concept of @dfn{available thread group} is
28638 introduced. Available thread group is an thread group that
28639 @value{GDBN} is not debugging, but that can be attached to, using the
28640 @code{-target-attach} command. The list of available top-level thread
28641 groups can be obtained using @samp{-list-thread-groups --available}.
28642 In general, the content of a thread group may be only retrieved only
28643 after attaching to that thread group.
28645 Thread groups are related to inferiors (@pxref{Inferiors and
28646 Programs}). Each inferior corresponds to a thread group of a special
28647 type @samp{process}, and some additional operations are permitted on
28648 such thread groups.
28650 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28651 @node GDB/MI Command Syntax
28652 @section @sc{gdb/mi} Command Syntax
28655 * GDB/MI Input Syntax::
28656 * GDB/MI Output Syntax::
28659 @node GDB/MI Input Syntax
28660 @subsection @sc{gdb/mi} Input Syntax
28662 @cindex input syntax for @sc{gdb/mi}
28663 @cindex @sc{gdb/mi}, input syntax
28665 @item @var{command} @expansion{}
28666 @code{@var{cli-command} | @var{mi-command}}
28668 @item @var{cli-command} @expansion{}
28669 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
28670 @var{cli-command} is any existing @value{GDBN} CLI command.
28672 @item @var{mi-command} @expansion{}
28673 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
28674 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
28676 @item @var{token} @expansion{}
28677 "any sequence of digits"
28679 @item @var{option} @expansion{}
28680 @code{"-" @var{parameter} [ " " @var{parameter} ]}
28682 @item @var{parameter} @expansion{}
28683 @code{@var{non-blank-sequence} | @var{c-string}}
28685 @item @var{operation} @expansion{}
28686 @emph{any of the operations described in this chapter}
28688 @item @var{non-blank-sequence} @expansion{}
28689 @emph{anything, provided it doesn't contain special characters such as
28690 "-", @var{nl}, """ and of course " "}
28692 @item @var{c-string} @expansion{}
28693 @code{""" @var{seven-bit-iso-c-string-content} """}
28695 @item @var{nl} @expansion{}
28704 The CLI commands are still handled by the @sc{mi} interpreter; their
28705 output is described below.
28708 The @code{@var{token}}, when present, is passed back when the command
28712 Some @sc{mi} commands accept optional arguments as part of the parameter
28713 list. Each option is identified by a leading @samp{-} (dash) and may be
28714 followed by an optional argument parameter. Options occur first in the
28715 parameter list and can be delimited from normal parameters using
28716 @samp{--} (this is useful when some parameters begin with a dash).
28723 We want easy access to the existing CLI syntax (for debugging).
28726 We want it to be easy to spot a @sc{mi} operation.
28729 @node GDB/MI Output Syntax
28730 @subsection @sc{gdb/mi} Output Syntax
28732 @cindex output syntax of @sc{gdb/mi}
28733 @cindex @sc{gdb/mi}, output syntax
28734 The output from @sc{gdb/mi} consists of zero or more out-of-band records
28735 followed, optionally, by a single result record. This result record
28736 is for the most recent command. The sequence of output records is
28737 terminated by @samp{(gdb)}.
28739 If an input command was prefixed with a @code{@var{token}} then the
28740 corresponding output for that command will also be prefixed by that same
28744 @item @var{output} @expansion{}
28745 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
28747 @item @var{result-record} @expansion{}
28748 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
28750 @item @var{out-of-band-record} @expansion{}
28751 @code{@var{async-record} | @var{stream-record}}
28753 @item @var{async-record} @expansion{}
28754 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
28756 @item @var{exec-async-output} @expansion{}
28757 @code{[ @var{token} ] "*" @var{async-output}}
28759 @item @var{status-async-output} @expansion{}
28760 @code{[ @var{token} ] "+" @var{async-output}}
28762 @item @var{notify-async-output} @expansion{}
28763 @code{[ @var{token} ] "=" @var{async-output}}
28765 @item @var{async-output} @expansion{}
28766 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
28768 @item @var{result-class} @expansion{}
28769 @code{"done" | "running" | "connected" | "error" | "exit"}
28771 @item @var{async-class} @expansion{}
28772 @code{"stopped" | @var{others}} (where @var{others} will be added
28773 depending on the needs---this is still in development).
28775 @item @var{result} @expansion{}
28776 @code{ @var{variable} "=" @var{value}}
28778 @item @var{variable} @expansion{}
28779 @code{ @var{string} }
28781 @item @var{value} @expansion{}
28782 @code{ @var{const} | @var{tuple} | @var{list} }
28784 @item @var{const} @expansion{}
28785 @code{@var{c-string}}
28787 @item @var{tuple} @expansion{}
28788 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
28790 @item @var{list} @expansion{}
28791 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
28792 @var{result} ( "," @var{result} )* "]" }
28794 @item @var{stream-record} @expansion{}
28795 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
28797 @item @var{console-stream-output} @expansion{}
28798 @code{"~" @var{c-string}}
28800 @item @var{target-stream-output} @expansion{}
28801 @code{"@@" @var{c-string}}
28803 @item @var{log-stream-output} @expansion{}
28804 @code{"&" @var{c-string}}
28806 @item @var{nl} @expansion{}
28809 @item @var{token} @expansion{}
28810 @emph{any sequence of digits}.
28818 All output sequences end in a single line containing a period.
28821 The @code{@var{token}} is from the corresponding request. Note that
28822 for all async output, while the token is allowed by the grammar and
28823 may be output by future versions of @value{GDBN} for select async
28824 output messages, it is generally omitted. Frontends should treat
28825 all async output as reporting general changes in the state of the
28826 target and there should be no need to associate async output to any
28830 @cindex status output in @sc{gdb/mi}
28831 @var{status-async-output} contains on-going status information about the
28832 progress of a slow operation. It can be discarded. All status output is
28833 prefixed by @samp{+}.
28836 @cindex async output in @sc{gdb/mi}
28837 @var{exec-async-output} contains asynchronous state change on the target
28838 (stopped, started, disappeared). All async output is prefixed by
28842 @cindex notify output in @sc{gdb/mi}
28843 @var{notify-async-output} contains supplementary information that the
28844 client should handle (e.g., a new breakpoint information). All notify
28845 output is prefixed by @samp{=}.
28848 @cindex console output in @sc{gdb/mi}
28849 @var{console-stream-output} is output that should be displayed as is in the
28850 console. It is the textual response to a CLI command. All the console
28851 output is prefixed by @samp{~}.
28854 @cindex target output in @sc{gdb/mi}
28855 @var{target-stream-output} is the output produced by the target program.
28856 All the target output is prefixed by @samp{@@}.
28859 @cindex log output in @sc{gdb/mi}
28860 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
28861 instance messages that should be displayed as part of an error log. All
28862 the log output is prefixed by @samp{&}.
28865 @cindex list output in @sc{gdb/mi}
28866 New @sc{gdb/mi} commands should only output @var{lists} containing
28872 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
28873 details about the various output records.
28875 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28876 @node GDB/MI Compatibility with CLI
28877 @section @sc{gdb/mi} Compatibility with CLI
28879 @cindex compatibility, @sc{gdb/mi} and CLI
28880 @cindex @sc{gdb/mi}, compatibility with CLI
28882 For the developers convenience CLI commands can be entered directly,
28883 but there may be some unexpected behaviour. For example, commands
28884 that query the user will behave as if the user replied yes, breakpoint
28885 command lists are not executed and some CLI commands, such as
28886 @code{if}, @code{when} and @code{define}, prompt for further input with
28887 @samp{>}, which is not valid MI output.
28889 This feature may be removed at some stage in the future and it is
28890 recommended that front ends use the @code{-interpreter-exec} command
28891 (@pxref{-interpreter-exec}).
28893 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28894 @node GDB/MI Development and Front Ends
28895 @section @sc{gdb/mi} Development and Front Ends
28896 @cindex @sc{gdb/mi} development
28898 The application which takes the MI output and presents the state of the
28899 program being debugged to the user is called a @dfn{front end}.
28901 Although @sc{gdb/mi} is still incomplete, it is currently being used
28902 by a variety of front ends to @value{GDBN}. This makes it difficult
28903 to introduce new functionality without breaking existing usage. This
28904 section tries to minimize the problems by describing how the protocol
28907 Some changes in MI need not break a carefully designed front end, and
28908 for these the MI version will remain unchanged. The following is a
28909 list of changes that may occur within one level, so front ends should
28910 parse MI output in a way that can handle them:
28914 New MI commands may be added.
28917 New fields may be added to the output of any MI command.
28920 The range of values for fields with specified values, e.g.,
28921 @code{in_scope} (@pxref{-var-update}) may be extended.
28923 @c The format of field's content e.g type prefix, may change so parse it
28924 @c at your own risk. Yes, in general?
28926 @c The order of fields may change? Shouldn't really matter but it might
28927 @c resolve inconsistencies.
28930 If the changes are likely to break front ends, the MI version level
28931 will be increased by one. This will allow the front end to parse the
28932 output according to the MI version. Apart from mi0, new versions of
28933 @value{GDBN} will not support old versions of MI and it will be the
28934 responsibility of the front end to work with the new one.
28936 @c Starting with mi3, add a new command -mi-version that prints the MI
28939 The best way to avoid unexpected changes in MI that might break your front
28940 end is to make your project known to @value{GDBN} developers and
28941 follow development on @email{gdb@@sourceware.org} and
28942 @email{gdb-patches@@sourceware.org}.
28943 @cindex mailing lists
28945 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28946 @node GDB/MI Output Records
28947 @section @sc{gdb/mi} Output Records
28950 * GDB/MI Result Records::
28951 * GDB/MI Stream Records::
28952 * GDB/MI Async Records::
28953 * GDB/MI Breakpoint Information::
28954 * GDB/MI Frame Information::
28955 * GDB/MI Thread Information::
28956 * GDB/MI Ada Exception Information::
28959 @node GDB/MI Result Records
28960 @subsection @sc{gdb/mi} Result Records
28962 @cindex result records in @sc{gdb/mi}
28963 @cindex @sc{gdb/mi}, result records
28964 In addition to a number of out-of-band notifications, the response to a
28965 @sc{gdb/mi} command includes one of the following result indications:
28969 @item "^done" [ "," @var{results} ]
28970 The synchronous operation was successful, @code{@var{results}} are the return
28975 This result record is equivalent to @samp{^done}. Historically, it
28976 was output instead of @samp{^done} if the command has resumed the
28977 target. This behaviour is maintained for backward compatibility, but
28978 all frontends should treat @samp{^done} and @samp{^running}
28979 identically and rely on the @samp{*running} output record to determine
28980 which threads are resumed.
28984 @value{GDBN} has connected to a remote target.
28986 @item "^error" "," @var{c-string}
28988 The operation failed. The @code{@var{c-string}} contains the corresponding
28993 @value{GDBN} has terminated.
28997 @node GDB/MI Stream Records
28998 @subsection @sc{gdb/mi} Stream Records
29000 @cindex @sc{gdb/mi}, stream records
29001 @cindex stream records in @sc{gdb/mi}
29002 @value{GDBN} internally maintains a number of output streams: the console, the
29003 target, and the log. The output intended for each of these streams is
29004 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
29006 Each stream record begins with a unique @dfn{prefix character} which
29007 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
29008 Syntax}). In addition to the prefix, each stream record contains a
29009 @code{@var{string-output}}. This is either raw text (with an implicit new
29010 line) or a quoted C string (which does not contain an implicit newline).
29013 @item "~" @var{string-output}
29014 The console output stream contains text that should be displayed in the
29015 CLI console window. It contains the textual responses to CLI commands.
29017 @item "@@" @var{string-output}
29018 The target output stream contains any textual output from the running
29019 target. This is only present when GDB's event loop is truly
29020 asynchronous, which is currently only the case for remote targets.
29022 @item "&" @var{string-output}
29023 The log stream contains debugging messages being produced by @value{GDBN}'s
29027 @node GDB/MI Async Records
29028 @subsection @sc{gdb/mi} Async Records
29030 @cindex async records in @sc{gdb/mi}
29031 @cindex @sc{gdb/mi}, async records
29032 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
29033 additional changes that have occurred. Those changes can either be a
29034 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
29035 target activity (e.g., target stopped).
29037 The following is the list of possible async records:
29041 @item *running,thread-id="@var{thread}"
29042 The target is now running. The @var{thread} field tells which
29043 specific thread is now running, and can be @samp{all} if all threads
29044 are running. The frontend should assume that no interaction with a
29045 running thread is possible after this notification is produced.
29046 The frontend should not assume that this notification is output
29047 only once for any command. @value{GDBN} may emit this notification
29048 several times, either for different threads, because it cannot resume
29049 all threads together, or even for a single thread, if the thread must
29050 be stepped though some code before letting it run freely.
29052 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
29053 The target has stopped. The @var{reason} field can have one of the
29057 @item breakpoint-hit
29058 A breakpoint was reached.
29059 @item watchpoint-trigger
29060 A watchpoint was triggered.
29061 @item read-watchpoint-trigger
29062 A read watchpoint was triggered.
29063 @item access-watchpoint-trigger
29064 An access watchpoint was triggered.
29065 @item function-finished
29066 An -exec-finish or similar CLI command was accomplished.
29067 @item location-reached
29068 An -exec-until or similar CLI command was accomplished.
29069 @item watchpoint-scope
29070 A watchpoint has gone out of scope.
29071 @item end-stepping-range
29072 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
29073 similar CLI command was accomplished.
29074 @item exited-signalled
29075 The inferior exited because of a signal.
29077 The inferior exited.
29078 @item exited-normally
29079 The inferior exited normally.
29080 @item signal-received
29081 A signal was received by the inferior.
29083 The inferior has stopped due to a library being loaded or unloaded.
29084 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29085 set or when a @code{catch load} or @code{catch unload} catchpoint is
29086 in use (@pxref{Set Catchpoints}).
29088 The inferior has forked. This is reported when @code{catch fork}
29089 (@pxref{Set Catchpoints}) has been used.
29091 The inferior has vforked. This is reported in when @code{catch vfork}
29092 (@pxref{Set Catchpoints}) has been used.
29093 @item syscall-entry
29094 The inferior entered a system call. This is reported when @code{catch
29095 syscall} (@pxref{Set Catchpoints}) has been used.
29096 @item syscall-entry
29097 The inferior returned from a system call. This is reported when
29098 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29100 The inferior called @code{exec}. This is reported when @code{catch exec}
29101 (@pxref{Set Catchpoints}) has been used.
29104 The @var{id} field identifies the thread that directly caused the stop
29105 -- for example by hitting a breakpoint. Depending on whether all-stop
29106 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29107 stop all threads, or only the thread that directly triggered the stop.
29108 If all threads are stopped, the @var{stopped} field will have the
29109 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29110 field will be a list of thread identifiers. Presently, this list will
29111 always include a single thread, but frontend should be prepared to see
29112 several threads in the list. The @var{core} field reports the
29113 processor core on which the stop event has happened. This field may be absent
29114 if such information is not available.
29116 @item =thread-group-added,id="@var{id}"
29117 @itemx =thread-group-removed,id="@var{id}"
29118 A thread group was either added or removed. The @var{id} field
29119 contains the @value{GDBN} identifier of the thread group. When a thread
29120 group is added, it generally might not be associated with a running
29121 process. When a thread group is removed, its id becomes invalid and
29122 cannot be used in any way.
29124 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29125 A thread group became associated with a running program,
29126 either because the program was just started or the thread group
29127 was attached to a program. The @var{id} field contains the
29128 @value{GDBN} identifier of the thread group. The @var{pid} field
29129 contains process identifier, specific to the operating system.
29131 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29132 A thread group is no longer associated with a running program,
29133 either because the program has exited, or because it was detached
29134 from. The @var{id} field contains the @value{GDBN} identifier of the
29135 thread group. @var{code} is the exit code of the inferior; it exists
29136 only when the inferior exited with some code.
29138 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29139 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29140 A thread either was created, or has exited. The @var{id} field
29141 contains the @value{GDBN} identifier of the thread. The @var{gid}
29142 field identifies the thread group this thread belongs to.
29144 @item =thread-selected,id="@var{id}"
29145 Informs that the selected thread was changed as result of the last
29146 command. This notification is not emitted as result of @code{-thread-select}
29147 command but is emitted whenever an MI command that is not documented
29148 to change the selected thread actually changes it. In particular,
29149 invoking, directly or indirectly (via user-defined command), the CLI
29150 @code{thread} command, will generate this notification.
29152 We suggest that in response to this notification, front ends
29153 highlight the selected thread and cause subsequent commands to apply to
29156 @item =library-loaded,...
29157 Reports that a new library file was loaded by the program. This
29158 notification has 4 fields---@var{id}, @var{target-name},
29159 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29160 opaque identifier of the library. For remote debugging case,
29161 @var{target-name} and @var{host-name} fields give the name of the
29162 library file on the target, and on the host respectively. For native
29163 debugging, both those fields have the same value. The
29164 @var{symbols-loaded} field is emitted only for backward compatibility
29165 and should not be relied on to convey any useful information. The
29166 @var{thread-group} field, if present, specifies the id of the thread
29167 group in whose context the library was loaded. If the field is
29168 absent, it means the library was loaded in the context of all present
29171 @item =library-unloaded,...
29172 Reports that a library was unloaded by the program. This notification
29173 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29174 the same meaning as for the @code{=library-loaded} notification.
29175 The @var{thread-group} field, if present, specifies the id of the
29176 thread group in whose context the library was unloaded. If the field is
29177 absent, it means the library was unloaded in the context of all present
29180 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29181 @itemx =traceframe-changed,end
29182 Reports that the trace frame was changed and its new number is
29183 @var{tfnum}. The number of the tracepoint associated with this trace
29184 frame is @var{tpnum}.
29186 @item =tsv-created,name=@var{name},initial=@var{initial}
29187 Reports that the new trace state variable @var{name} is created with
29188 initial value @var{initial}.
29190 @item =tsv-deleted,name=@var{name}
29191 @itemx =tsv-deleted
29192 Reports that the trace state variable @var{name} is deleted or all
29193 trace state variables are deleted.
29195 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29196 Reports that the trace state variable @var{name} is modified with
29197 the initial value @var{initial}. The current value @var{current} of
29198 trace state variable is optional and is reported if the current
29199 value of trace state variable is known.
29201 @item =breakpoint-created,bkpt=@{...@}
29202 @itemx =breakpoint-modified,bkpt=@{...@}
29203 @itemx =breakpoint-deleted,id=@var{number}
29204 Reports that a breakpoint was created, modified, or deleted,
29205 respectively. Only user-visible breakpoints are reported to the MI
29208 The @var{bkpt} argument is of the same form as returned by the various
29209 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29210 @var{number} is the ordinal number of the breakpoint.
29212 Note that if a breakpoint is emitted in the result record of a
29213 command, then it will not also be emitted in an async record.
29215 @item =record-started,thread-group="@var{id}"
29216 @itemx =record-stopped,thread-group="@var{id}"
29217 Execution log recording was either started or stopped on an
29218 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29219 group corresponding to the affected inferior.
29221 @item =cmd-param-changed,param=@var{param},value=@var{value}
29222 Reports that a parameter of the command @code{set @var{param}} is
29223 changed to @var{value}. In the multi-word @code{set} command,
29224 the @var{param} is the whole parameter list to @code{set} command.
29225 For example, In command @code{set check type on}, @var{param}
29226 is @code{check type} and @var{value} is @code{on}.
29228 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29229 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29230 written in an inferior. The @var{id} is the identifier of the
29231 thread group corresponding to the affected inferior. The optional
29232 @code{type="code"} part is reported if the memory written to holds
29236 @node GDB/MI Breakpoint Information
29237 @subsection @sc{gdb/mi} Breakpoint Information
29239 When @value{GDBN} reports information about a breakpoint, a
29240 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29245 The breakpoint number. For a breakpoint that represents one location
29246 of a multi-location breakpoint, this will be a dotted pair, like
29250 The type of the breakpoint. For ordinary breakpoints this will be
29251 @samp{breakpoint}, but many values are possible.
29254 If the type of the breakpoint is @samp{catchpoint}, then this
29255 indicates the exact type of catchpoint.
29258 This is the breakpoint disposition---either @samp{del}, meaning that
29259 the breakpoint will be deleted at the next stop, or @samp{keep},
29260 meaning that the breakpoint will not be deleted.
29263 This indicates whether the breakpoint is enabled, in which case the
29264 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29265 Note that this is not the same as the field @code{enable}.
29268 The address of the breakpoint. This may be a hexidecimal number,
29269 giving the address; or the string @samp{<PENDING>}, for a pending
29270 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29271 multiple locations. This field will not be present if no address can
29272 be determined. For example, a watchpoint does not have an address.
29275 If known, the function in which the breakpoint appears.
29276 If not known, this field is not present.
29279 The name of the source file which contains this function, if known.
29280 If not known, this field is not present.
29283 The full file name of the source file which contains this function, if
29284 known. If not known, this field is not present.
29287 The line number at which this breakpoint appears, if known.
29288 If not known, this field is not present.
29291 If the source file is not known, this field may be provided. If
29292 provided, this holds the address of the breakpoint, possibly followed
29296 If this breakpoint is pending, this field is present and holds the
29297 text used to set the breakpoint, as entered by the user.
29300 Where this breakpoint's condition is evaluated, either @samp{host} or
29304 If this is a thread-specific breakpoint, then this identifies the
29305 thread in which the breakpoint can trigger.
29308 If this breakpoint is restricted to a particular Ada task, then this
29309 field will hold the task identifier.
29312 If the breakpoint is conditional, this is the condition expression.
29315 The ignore count of the breakpoint.
29318 The enable count of the breakpoint.
29320 @item traceframe-usage
29323 @item static-tracepoint-marker-string-id
29324 For a static tracepoint, the name of the static tracepoint marker.
29327 For a masked watchpoint, this is the mask.
29330 A tracepoint's pass count.
29332 @item original-location
29333 The location of the breakpoint as originally specified by the user.
29334 This field is optional.
29337 The number of times the breakpoint has been hit.
29340 This field is only given for tracepoints. This is either @samp{y},
29341 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29345 Some extra data, the exact contents of which are type-dependent.
29349 For example, here is what the output of @code{-break-insert}
29350 (@pxref{GDB/MI Breakpoint Commands}) might be:
29353 -> -break-insert main
29354 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29355 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29356 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29361 @node GDB/MI Frame Information
29362 @subsection @sc{gdb/mi} Frame Information
29364 Response from many MI commands includes an information about stack
29365 frame. This information is a tuple that may have the following
29370 The level of the stack frame. The innermost frame has the level of
29371 zero. This field is always present.
29374 The name of the function corresponding to the frame. This field may
29375 be absent if @value{GDBN} is unable to determine the function name.
29378 The code address for the frame. This field is always present.
29381 The name of the source files that correspond to the frame's code
29382 address. This field may be absent.
29385 The source line corresponding to the frames' code address. This field
29389 The name of the binary file (either executable or shared library) the
29390 corresponds to the frame's code address. This field may be absent.
29394 @node GDB/MI Thread Information
29395 @subsection @sc{gdb/mi} Thread Information
29397 Whenever @value{GDBN} has to report an information about a thread, it
29398 uses a tuple with the following fields:
29402 The numeric id assigned to the thread by @value{GDBN}. This field is
29406 Target-specific string identifying the thread. This field is always present.
29409 Additional information about the thread provided by the target.
29410 It is supposed to be human-readable and not interpreted by the
29411 frontend. This field is optional.
29414 Either @samp{stopped} or @samp{running}, depending on whether the
29415 thread is presently running. This field is always present.
29418 The value of this field is an integer number of the processor core the
29419 thread was last seen on. This field is optional.
29422 @node GDB/MI Ada Exception Information
29423 @subsection @sc{gdb/mi} Ada Exception Information
29425 Whenever a @code{*stopped} record is emitted because the program
29426 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29427 @value{GDBN} provides the name of the exception that was raised via
29428 the @code{exception-name} field.
29430 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29431 @node GDB/MI Simple Examples
29432 @section Simple Examples of @sc{gdb/mi} Interaction
29433 @cindex @sc{gdb/mi}, simple examples
29435 This subsection presents several simple examples of interaction using
29436 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29437 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29438 the output received from @sc{gdb/mi}.
29440 Note the line breaks shown in the examples are here only for
29441 readability, they don't appear in the real output.
29443 @subheading Setting a Breakpoint
29445 Setting a breakpoint generates synchronous output which contains detailed
29446 information of the breakpoint.
29449 -> -break-insert main
29450 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29451 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29452 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29457 @subheading Program Execution
29459 Program execution generates asynchronous records and MI gives the
29460 reason that execution stopped.
29466 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29467 frame=@{addr="0x08048564",func="main",
29468 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29469 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29474 <- *stopped,reason="exited-normally"
29478 @subheading Quitting @value{GDBN}
29480 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29488 Please note that @samp{^exit} is printed immediately, but it might
29489 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29490 performs necessary cleanups, including killing programs being debugged
29491 or disconnecting from debug hardware, so the frontend should wait till
29492 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29493 fails to exit in reasonable time.
29495 @subheading A Bad Command
29497 Here's what happens if you pass a non-existent command:
29501 <- ^error,msg="Undefined MI command: rubbish"
29506 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29507 @node GDB/MI Command Description Format
29508 @section @sc{gdb/mi} Command Description Format
29510 The remaining sections describe blocks of commands. Each block of
29511 commands is laid out in a fashion similar to this section.
29513 @subheading Motivation
29515 The motivation for this collection of commands.
29517 @subheading Introduction
29519 A brief introduction to this collection of commands as a whole.
29521 @subheading Commands
29523 For each command in the block, the following is described:
29525 @subsubheading Synopsis
29528 -command @var{args}@dots{}
29531 @subsubheading Result
29533 @subsubheading @value{GDBN} Command
29535 The corresponding @value{GDBN} CLI command(s), if any.
29537 @subsubheading Example
29539 Example(s) formatted for readability. Some of the described commands have
29540 not been implemented yet and these are labeled N.A.@: (not available).
29543 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29544 @node GDB/MI Breakpoint Commands
29545 @section @sc{gdb/mi} Breakpoint Commands
29547 @cindex breakpoint commands for @sc{gdb/mi}
29548 @cindex @sc{gdb/mi}, breakpoint commands
29549 This section documents @sc{gdb/mi} commands for manipulating
29552 @subheading The @code{-break-after} Command
29553 @findex -break-after
29555 @subsubheading Synopsis
29558 -break-after @var{number} @var{count}
29561 The breakpoint number @var{number} is not in effect until it has been
29562 hit @var{count} times. To see how this is reflected in the output of
29563 the @samp{-break-list} command, see the description of the
29564 @samp{-break-list} command below.
29566 @subsubheading @value{GDBN} Command
29568 The corresponding @value{GDBN} command is @samp{ignore}.
29570 @subsubheading Example
29575 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29576 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29577 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29585 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29586 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29587 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29588 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29589 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29590 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29591 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29592 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29593 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29594 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29599 @subheading The @code{-break-catch} Command
29600 @findex -break-catch
29603 @subheading The @code{-break-commands} Command
29604 @findex -break-commands
29606 @subsubheading Synopsis
29609 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29612 Specifies the CLI commands that should be executed when breakpoint
29613 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29614 are the commands. If no command is specified, any previously-set
29615 commands are cleared. @xref{Break Commands}. Typical use of this
29616 functionality is tracing a program, that is, printing of values of
29617 some variables whenever breakpoint is hit and then continuing.
29619 @subsubheading @value{GDBN} Command
29621 The corresponding @value{GDBN} command is @samp{commands}.
29623 @subsubheading Example
29628 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29629 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29630 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29633 -break-commands 1 "print v" "continue"
29638 @subheading The @code{-break-condition} Command
29639 @findex -break-condition
29641 @subsubheading Synopsis
29644 -break-condition @var{number} @var{expr}
29647 Breakpoint @var{number} will stop the program only if the condition in
29648 @var{expr} is true. The condition becomes part of the
29649 @samp{-break-list} output (see the description of the @samp{-break-list}
29652 @subsubheading @value{GDBN} Command
29654 The corresponding @value{GDBN} command is @samp{condition}.
29656 @subsubheading Example
29660 -break-condition 1 1
29664 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29665 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29666 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29667 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29668 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29669 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29670 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29671 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29672 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29673 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
29677 @subheading The @code{-break-delete} Command
29678 @findex -break-delete
29680 @subsubheading Synopsis
29683 -break-delete ( @var{breakpoint} )+
29686 Delete the breakpoint(s) whose number(s) are specified in the argument
29687 list. This is obviously reflected in the breakpoint list.
29689 @subsubheading @value{GDBN} Command
29691 The corresponding @value{GDBN} command is @samp{delete}.
29693 @subsubheading Example
29701 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29702 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29703 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29704 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29705 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29706 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29707 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29712 @subheading The @code{-break-disable} Command
29713 @findex -break-disable
29715 @subsubheading Synopsis
29718 -break-disable ( @var{breakpoint} )+
29721 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
29722 break list is now set to @samp{n} for the named @var{breakpoint}(s).
29724 @subsubheading @value{GDBN} Command
29726 The corresponding @value{GDBN} command is @samp{disable}.
29728 @subsubheading Example
29736 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29737 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29738 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29739 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29740 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29741 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29742 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29743 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
29744 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29745 line="5",thread-groups=["i1"],times="0"@}]@}
29749 @subheading The @code{-break-enable} Command
29750 @findex -break-enable
29752 @subsubheading Synopsis
29755 -break-enable ( @var{breakpoint} )+
29758 Enable (previously disabled) @var{breakpoint}(s).
29760 @subsubheading @value{GDBN} Command
29762 The corresponding @value{GDBN} command is @samp{enable}.
29764 @subsubheading Example
29772 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29773 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29774 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29775 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29776 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29777 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29778 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29779 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29780 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29781 line="5",thread-groups=["i1"],times="0"@}]@}
29785 @subheading The @code{-break-info} Command
29786 @findex -break-info
29788 @subsubheading Synopsis
29791 -break-info @var{breakpoint}
29795 Get information about a single breakpoint.
29797 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
29798 Information}, for details on the format of each breakpoint in the
29801 @subsubheading @value{GDBN} Command
29803 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
29805 @subsubheading Example
29808 @subheading The @code{-break-insert} Command
29809 @findex -break-insert
29811 @subsubheading Synopsis
29814 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
29815 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29816 [ -p @var{thread-id} ] [ @var{location} ]
29820 If specified, @var{location}, can be one of:
29827 @item filename:linenum
29828 @item filename:function
29832 The possible optional parameters of this command are:
29836 Insert a temporary breakpoint.
29838 Insert a hardware breakpoint.
29840 If @var{location} cannot be parsed (for example if it
29841 refers to unknown files or functions), create a pending
29842 breakpoint. Without this flag, @value{GDBN} will report
29843 an error, and won't create a breakpoint, if @var{location}
29846 Create a disabled breakpoint.
29848 Create a tracepoint. @xref{Tracepoints}. When this parameter
29849 is used together with @samp{-h}, a fast tracepoint is created.
29850 @item -c @var{condition}
29851 Make the breakpoint conditional on @var{condition}.
29852 @item -i @var{ignore-count}
29853 Initialize the @var{ignore-count}.
29854 @item -p @var{thread-id}
29855 Restrict the breakpoint to the specified @var{thread-id}.
29858 @subsubheading Result
29860 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29861 resulting breakpoint.
29863 Note: this format is open to change.
29864 @c An out-of-band breakpoint instead of part of the result?
29866 @subsubheading @value{GDBN} Command
29868 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
29869 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
29871 @subsubheading Example
29876 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
29877 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
29880 -break-insert -t foo
29881 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
29882 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
29886 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29887 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29888 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29889 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29890 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29891 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29892 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29893 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29894 addr="0x0001072c", func="main",file="recursive2.c",
29895 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
29897 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
29898 addr="0x00010774",func="foo",file="recursive2.c",
29899 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29902 @c -break-insert -r foo.*
29903 @c ~int foo(int, int);
29904 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
29905 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29910 @subheading The @code{-dprintf-insert} Command
29911 @findex -dprintf-insert
29913 @subsubheading Synopsis
29916 -dprintf-insert [ -t ] [ -f ] [ -d ]
29917 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29918 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
29923 If specified, @var{location}, can be one of:
29926 @item @var{function}
29929 @c @item @var{linenum}
29930 @item @var{filename}:@var{linenum}
29931 @item @var{filename}:function
29932 @item *@var{address}
29935 The possible optional parameters of this command are:
29939 Insert a temporary breakpoint.
29941 If @var{location} cannot be parsed (for example, if it
29942 refers to unknown files or functions), create a pending
29943 breakpoint. Without this flag, @value{GDBN} will report
29944 an error, and won't create a breakpoint, if @var{location}
29947 Create a disabled breakpoint.
29948 @item -c @var{condition}
29949 Make the breakpoint conditional on @var{condition}.
29950 @item -i @var{ignore-count}
29951 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
29952 to @var{ignore-count}.
29953 @item -p @var{thread-id}
29954 Restrict the breakpoint to the specified @var{thread-id}.
29957 @subsubheading Result
29959 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29960 resulting breakpoint.
29962 @c An out-of-band breakpoint instead of part of the result?
29964 @subsubheading @value{GDBN} Command
29966 The corresponding @value{GDBN} command is @samp{dprintf}.
29968 @subsubheading Example
29972 4-dprintf-insert foo "At foo entry\n"
29973 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29974 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29975 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29976 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29977 original-location="foo"@}
29979 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29980 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29981 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29982 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29983 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29984 original-location="mi-dprintf.c:26"@}
29988 @subheading The @code{-break-list} Command
29989 @findex -break-list
29991 @subsubheading Synopsis
29997 Displays the list of inserted breakpoints, showing the following fields:
30001 number of the breakpoint
30003 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
30005 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
30008 is the breakpoint enabled or no: @samp{y} or @samp{n}
30010 memory location at which the breakpoint is set
30012 logical location of the breakpoint, expressed by function name, file
30014 @item Thread-groups
30015 list of thread groups to which this breakpoint applies
30017 number of times the breakpoint has been hit
30020 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
30021 @code{body} field is an empty list.
30023 @subsubheading @value{GDBN} Command
30025 The corresponding @value{GDBN} command is @samp{info break}.
30027 @subsubheading Example
30032 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30033 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30034 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30035 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30036 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30037 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30038 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30039 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30040 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
30042 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
30043 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
30044 line="13",thread-groups=["i1"],times="0"@}]@}
30048 Here's an example of the result when there are no breakpoints:
30053 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
30054 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30055 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30056 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30057 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30058 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30059 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30064 @subheading The @code{-break-passcount} Command
30065 @findex -break-passcount
30067 @subsubheading Synopsis
30070 -break-passcount @var{tracepoint-number} @var{passcount}
30073 Set the passcount for tracepoint @var{tracepoint-number} to
30074 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
30075 is not a tracepoint, error is emitted. This corresponds to CLI
30076 command @samp{passcount}.
30078 @subheading The @code{-break-watch} Command
30079 @findex -break-watch
30081 @subsubheading Synopsis
30084 -break-watch [ -a | -r ]
30087 Create a watchpoint. With the @samp{-a} option it will create an
30088 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30089 read from or on a write to the memory location. With the @samp{-r}
30090 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30091 trigger only when the memory location is accessed for reading. Without
30092 either of the options, the watchpoint created is a regular watchpoint,
30093 i.e., it will trigger when the memory location is accessed for writing.
30094 @xref{Set Watchpoints, , Setting Watchpoints}.
30096 Note that @samp{-break-list} will report a single list of watchpoints and
30097 breakpoints inserted.
30099 @subsubheading @value{GDBN} Command
30101 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30104 @subsubheading Example
30106 Setting a watchpoint on a variable in the @code{main} function:
30111 ^done,wpt=@{number="2",exp="x"@}
30116 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30117 value=@{old="-268439212",new="55"@},
30118 frame=@{func="main",args=[],file="recursive2.c",
30119 fullname="/home/foo/bar/recursive2.c",line="5"@}
30123 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30124 the program execution twice: first for the variable changing value, then
30125 for the watchpoint going out of scope.
30130 ^done,wpt=@{number="5",exp="C"@}
30135 *stopped,reason="watchpoint-trigger",
30136 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30137 frame=@{func="callee4",args=[],
30138 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30139 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30144 *stopped,reason="watchpoint-scope",wpnum="5",
30145 frame=@{func="callee3",args=[@{name="strarg",
30146 value="0x11940 \"A string argument.\""@}],
30147 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30148 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30152 Listing breakpoints and watchpoints, at different points in the program
30153 execution. Note that once the watchpoint goes out of scope, it is
30159 ^done,wpt=@{number="2",exp="C"@}
30162 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30163 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30164 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30165 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30166 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30167 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30168 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30169 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30170 addr="0x00010734",func="callee4",
30171 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30172 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30174 bkpt=@{number="2",type="watchpoint",disp="keep",
30175 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30180 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30181 value=@{old="-276895068",new="3"@},
30182 frame=@{func="callee4",args=[],
30183 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30184 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30187 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30188 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30189 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30190 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30191 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30192 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30193 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30194 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30195 addr="0x00010734",func="callee4",
30196 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30197 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30199 bkpt=@{number="2",type="watchpoint",disp="keep",
30200 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30204 ^done,reason="watchpoint-scope",wpnum="2",
30205 frame=@{func="callee3",args=[@{name="strarg",
30206 value="0x11940 \"A string argument.\""@}],
30207 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30208 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30211 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30212 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30213 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30214 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30215 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30216 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30217 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30218 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30219 addr="0x00010734",func="callee4",
30220 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30221 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30222 thread-groups=["i1"],times="1"@}]@}
30227 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30228 @node GDB/MI Catchpoint Commands
30229 @section @sc{gdb/mi} Catchpoint Commands
30231 This section documents @sc{gdb/mi} commands for manipulating
30234 @subheading The @code{-catch-load} Command
30235 @findex -catch-load
30237 @subsubheading Synopsis
30240 -catch-load [ -t ] [ -d ] @var{regexp}
30243 Add a catchpoint for library load events. If the @samp{-t} option is used,
30244 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30245 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30246 in a disabled state. The @samp{regexp} argument is a regular
30247 expression used to match the name of the loaded library.
30250 @subsubheading @value{GDBN} Command
30252 The corresponding @value{GDBN} command is @samp{catch load}.
30254 @subsubheading Example
30257 -catch-load -t foo.so
30258 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30259 what="load of library matching foo.so",catch-type="load",times="0"@}
30264 @subheading The @code{-catch-unload} Command
30265 @findex -catch-unload
30267 @subsubheading Synopsis
30270 -catch-unload [ -t ] [ -d ] @var{regexp}
30273 Add a catchpoint for library unload events. If the @samp{-t} option is
30274 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30275 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30276 created in a disabled state. The @samp{regexp} argument is a regular
30277 expression used to match the name of the unloaded library.
30279 @subsubheading @value{GDBN} Command
30281 The corresponding @value{GDBN} command is @samp{catch unload}.
30283 @subsubheading Example
30286 -catch-unload -d bar.so
30287 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30288 what="load of library matching bar.so",catch-type="unload",times="0"@}
30293 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30294 @node GDB/MI Program Context
30295 @section @sc{gdb/mi} Program Context
30297 @subheading The @code{-exec-arguments} Command
30298 @findex -exec-arguments
30301 @subsubheading Synopsis
30304 -exec-arguments @var{args}
30307 Set the inferior program arguments, to be used in the next
30310 @subsubheading @value{GDBN} Command
30312 The corresponding @value{GDBN} command is @samp{set args}.
30314 @subsubheading Example
30318 -exec-arguments -v word
30325 @subheading The @code{-exec-show-arguments} Command
30326 @findex -exec-show-arguments
30328 @subsubheading Synopsis
30331 -exec-show-arguments
30334 Print the arguments of the program.
30336 @subsubheading @value{GDBN} Command
30338 The corresponding @value{GDBN} command is @samp{show args}.
30340 @subsubheading Example
30345 @subheading The @code{-environment-cd} Command
30346 @findex -environment-cd
30348 @subsubheading Synopsis
30351 -environment-cd @var{pathdir}
30354 Set @value{GDBN}'s working directory.
30356 @subsubheading @value{GDBN} Command
30358 The corresponding @value{GDBN} command is @samp{cd}.
30360 @subsubheading Example
30364 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30370 @subheading The @code{-environment-directory} Command
30371 @findex -environment-directory
30373 @subsubheading Synopsis
30376 -environment-directory [ -r ] [ @var{pathdir} ]+
30379 Add directories @var{pathdir} to beginning of search path for source files.
30380 If the @samp{-r} option is used, the search path is reset to the default
30381 search path. If directories @var{pathdir} are supplied in addition to the
30382 @samp{-r} option, the search path is first reset and then addition
30384 Multiple directories may be specified, separated by blanks. Specifying
30385 multiple directories in a single command
30386 results in the directories added to the beginning of the
30387 search path in the same order they were presented in the command.
30388 If blanks are needed as
30389 part of a directory name, double-quotes should be used around
30390 the name. In the command output, the path will show up separated
30391 by the system directory-separator character. The directory-separator
30392 character must not be used
30393 in any directory name.
30394 If no directories are specified, the current search path is displayed.
30396 @subsubheading @value{GDBN} Command
30398 The corresponding @value{GDBN} command is @samp{dir}.
30400 @subsubheading Example
30404 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30405 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30407 -environment-directory ""
30408 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30410 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30411 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30413 -environment-directory -r
30414 ^done,source-path="$cdir:$cwd"
30419 @subheading The @code{-environment-path} Command
30420 @findex -environment-path
30422 @subsubheading Synopsis
30425 -environment-path [ -r ] [ @var{pathdir} ]+
30428 Add directories @var{pathdir} to beginning of search path for object files.
30429 If the @samp{-r} option is used, the search path is reset to the original
30430 search path that existed at gdb start-up. If directories @var{pathdir} are
30431 supplied in addition to the
30432 @samp{-r} option, the search path is first reset and then addition
30434 Multiple directories may be specified, separated by blanks. Specifying
30435 multiple directories in a single command
30436 results in the directories added to the beginning of the
30437 search path in the same order they were presented in the command.
30438 If blanks are needed as
30439 part of a directory name, double-quotes should be used around
30440 the name. In the command output, the path will show up separated
30441 by the system directory-separator character. The directory-separator
30442 character must not be used
30443 in any directory name.
30444 If no directories are specified, the current path is displayed.
30447 @subsubheading @value{GDBN} Command
30449 The corresponding @value{GDBN} command is @samp{path}.
30451 @subsubheading Example
30456 ^done,path="/usr/bin"
30458 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30459 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30461 -environment-path -r /usr/local/bin
30462 ^done,path="/usr/local/bin:/usr/bin"
30467 @subheading The @code{-environment-pwd} Command
30468 @findex -environment-pwd
30470 @subsubheading Synopsis
30476 Show the current working directory.
30478 @subsubheading @value{GDBN} Command
30480 The corresponding @value{GDBN} command is @samp{pwd}.
30482 @subsubheading Example
30487 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30491 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30492 @node GDB/MI Thread Commands
30493 @section @sc{gdb/mi} Thread Commands
30496 @subheading The @code{-thread-info} Command
30497 @findex -thread-info
30499 @subsubheading Synopsis
30502 -thread-info [ @var{thread-id} ]
30505 Reports information about either a specific thread, if
30506 the @var{thread-id} parameter is present, or about all
30507 threads. When printing information about all threads,
30508 also reports the current thread.
30510 @subsubheading @value{GDBN} Command
30512 The @samp{info thread} command prints the same information
30515 @subsubheading Result
30517 The result is a list of threads. The following attributes are
30518 defined for a given thread:
30522 This field exists only for the current thread. It has the value @samp{*}.
30525 The identifier that @value{GDBN} uses to refer to the thread.
30528 The identifier that the target uses to refer to the thread.
30531 Extra information about the thread, in a target-specific format. This
30535 The name of the thread. If the user specified a name using the
30536 @code{thread name} command, then this name is given. Otherwise, if
30537 @value{GDBN} can extract the thread name from the target, then that
30538 name is given. If @value{GDBN} cannot find the thread name, then this
30542 The stack frame currently executing in the thread.
30545 The thread's state. The @samp{state} field may have the following
30550 The thread is stopped. Frame information is available for stopped
30554 The thread is running. There's no frame information for running
30560 If @value{GDBN} can find the CPU core on which this thread is running,
30561 then this field is the core identifier. This field is optional.
30565 @subsubheading Example
30570 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30571 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
30572 args=[]@},state="running"@},
30573 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30574 frame=@{level="0",addr="0x0804891f",func="foo",
30575 args=[@{name="i",value="10"@}],
30576 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
30577 state="running"@}],
30578 current-thread-id="1"
30582 @subheading The @code{-thread-list-ids} Command
30583 @findex -thread-list-ids
30585 @subsubheading Synopsis
30591 Produces a list of the currently known @value{GDBN} thread ids. At the
30592 end of the list it also prints the total number of such threads.
30594 This command is retained for historical reasons, the
30595 @code{-thread-info} command should be used instead.
30597 @subsubheading @value{GDBN} Command
30599 Part of @samp{info threads} supplies the same information.
30601 @subsubheading Example
30606 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30607 current-thread-id="1",number-of-threads="3"
30612 @subheading The @code{-thread-select} Command
30613 @findex -thread-select
30615 @subsubheading Synopsis
30618 -thread-select @var{threadnum}
30621 Make @var{threadnum} the current thread. It prints the number of the new
30622 current thread, and the topmost frame for that thread.
30624 This command is deprecated in favor of explicitly using the
30625 @samp{--thread} option to each command.
30627 @subsubheading @value{GDBN} Command
30629 The corresponding @value{GDBN} command is @samp{thread}.
30631 @subsubheading Example
30638 *stopped,reason="end-stepping-range",thread-id="2",line="187",
30639 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
30643 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30644 number-of-threads="3"
30647 ^done,new-thread-id="3",
30648 frame=@{level="0",func="vprintf",
30649 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
30650 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
30654 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30655 @node GDB/MI Ada Tasking Commands
30656 @section @sc{gdb/mi} Ada Tasking Commands
30658 @subheading The @code{-ada-task-info} Command
30659 @findex -ada-task-info
30661 @subsubheading Synopsis
30664 -ada-task-info [ @var{task-id} ]
30667 Reports information about either a specific Ada task, if the
30668 @var{task-id} parameter is present, or about all Ada tasks.
30670 @subsubheading @value{GDBN} Command
30672 The @samp{info tasks} command prints the same information
30673 about all Ada tasks (@pxref{Ada Tasks}).
30675 @subsubheading Result
30677 The result is a table of Ada tasks. The following columns are
30678 defined for each Ada task:
30682 This field exists only for the current thread. It has the value @samp{*}.
30685 The identifier that @value{GDBN} uses to refer to the Ada task.
30688 The identifier that the target uses to refer to the Ada task.
30691 The identifier of the thread corresponding to the Ada task.
30693 This field should always exist, as Ada tasks are always implemented
30694 on top of a thread. But if @value{GDBN} cannot find this corresponding
30695 thread for any reason, the field is omitted.
30698 This field exists only when the task was created by another task.
30699 In this case, it provides the ID of the parent task.
30702 The base priority of the task.
30705 The current state of the task. For a detailed description of the
30706 possible states, see @ref{Ada Tasks}.
30709 The name of the task.
30713 @subsubheading Example
30717 ^done,tasks=@{nr_rows="3",nr_cols="8",
30718 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
30719 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
30720 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
30721 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
30722 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
30723 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
30724 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
30725 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
30726 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
30727 state="Child Termination Wait",name="main_task"@}]@}
30731 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30732 @node GDB/MI Program Execution
30733 @section @sc{gdb/mi} Program Execution
30735 These are the asynchronous commands which generate the out-of-band
30736 record @samp{*stopped}. Currently @value{GDBN} only really executes
30737 asynchronously with remote targets and this interaction is mimicked in
30740 @subheading The @code{-exec-continue} Command
30741 @findex -exec-continue
30743 @subsubheading Synopsis
30746 -exec-continue [--reverse] [--all|--thread-group N]
30749 Resumes the execution of the inferior program, which will continue
30750 to execute until it reaches a debugger stop event. If the
30751 @samp{--reverse} option is specified, execution resumes in reverse until
30752 it reaches a stop event. Stop events may include
30755 breakpoints or watchpoints
30757 signals or exceptions
30759 the end of the process (or its beginning under @samp{--reverse})
30761 the end or beginning of a replay log if one is being used.
30763 In all-stop mode (@pxref{All-Stop
30764 Mode}), may resume only one thread, or all threads, depending on the
30765 value of the @samp{scheduler-locking} variable. If @samp{--all} is
30766 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
30767 ignored in all-stop mode. If the @samp{--thread-group} options is
30768 specified, then all threads in that thread group are resumed.
30770 @subsubheading @value{GDBN} Command
30772 The corresponding @value{GDBN} corresponding is @samp{continue}.
30774 @subsubheading Example
30781 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
30782 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
30788 @subheading The @code{-exec-finish} Command
30789 @findex -exec-finish
30791 @subsubheading Synopsis
30794 -exec-finish [--reverse]
30797 Resumes the execution of the inferior program until the current
30798 function is exited. Displays the results returned by the function.
30799 If the @samp{--reverse} option is specified, resumes the reverse
30800 execution of the inferior program until the point where current
30801 function was called.
30803 @subsubheading @value{GDBN} Command
30805 The corresponding @value{GDBN} command is @samp{finish}.
30807 @subsubheading Example
30809 Function returning @code{void}.
30816 *stopped,reason="function-finished",frame=@{func="main",args=[],
30817 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
30821 Function returning other than @code{void}. The name of the internal
30822 @value{GDBN} variable storing the result is printed, together with the
30829 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
30830 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
30831 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30832 gdb-result-var="$1",return-value="0"
30837 @subheading The @code{-exec-interrupt} Command
30838 @findex -exec-interrupt
30840 @subsubheading Synopsis
30843 -exec-interrupt [--all|--thread-group N]
30846 Interrupts the background execution of the target. Note how the token
30847 associated with the stop message is the one for the execution command
30848 that has been interrupted. The token for the interrupt itself only
30849 appears in the @samp{^done} output. If the user is trying to
30850 interrupt a non-running program, an error message will be printed.
30852 Note that when asynchronous execution is enabled, this command is
30853 asynchronous just like other execution commands. That is, first the
30854 @samp{^done} response will be printed, and the target stop will be
30855 reported after that using the @samp{*stopped} notification.
30857 In non-stop mode, only the context thread is interrupted by default.
30858 All threads (in all inferiors) will be interrupted if the
30859 @samp{--all} option is specified. If the @samp{--thread-group}
30860 option is specified, all threads in that group will be interrupted.
30862 @subsubheading @value{GDBN} Command
30864 The corresponding @value{GDBN} command is @samp{interrupt}.
30866 @subsubheading Example
30877 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30878 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30879 fullname="/home/foo/bar/try.c",line="13"@}
30884 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30888 @subheading The @code{-exec-jump} Command
30891 @subsubheading Synopsis
30894 -exec-jump @var{location}
30897 Resumes execution of the inferior program at the location specified by
30898 parameter. @xref{Specify Location}, for a description of the
30899 different forms of @var{location}.
30901 @subsubheading @value{GDBN} Command
30903 The corresponding @value{GDBN} command is @samp{jump}.
30905 @subsubheading Example
30908 -exec-jump foo.c:10
30909 *running,thread-id="all"
30914 @subheading The @code{-exec-next} Command
30917 @subsubheading Synopsis
30920 -exec-next [--reverse]
30923 Resumes execution of the inferior program, stopping when the beginning
30924 of the next source line is reached.
30926 If the @samp{--reverse} option is specified, resumes reverse execution
30927 of the inferior program, stopping at the beginning of the previous
30928 source line. If you issue this command on the first line of a
30929 function, it will take you back to the caller of that function, to the
30930 source line where the function was called.
30933 @subsubheading @value{GDBN} Command
30935 The corresponding @value{GDBN} command is @samp{next}.
30937 @subsubheading Example
30943 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30948 @subheading The @code{-exec-next-instruction} Command
30949 @findex -exec-next-instruction
30951 @subsubheading Synopsis
30954 -exec-next-instruction [--reverse]
30957 Executes one machine instruction. If the instruction is a function
30958 call, continues until the function returns. If the program stops at an
30959 instruction in the middle of a source line, the address will be
30962 If the @samp{--reverse} option is specified, resumes reverse execution
30963 of the inferior program, stopping at the previous instruction. If the
30964 previously executed instruction was a return from another function,
30965 it will continue to execute in reverse until the call to that function
30966 (from the current stack frame) is reached.
30968 @subsubheading @value{GDBN} Command
30970 The corresponding @value{GDBN} command is @samp{nexti}.
30972 @subsubheading Example
30976 -exec-next-instruction
30980 *stopped,reason="end-stepping-range",
30981 addr="0x000100d4",line="5",file="hello.c"
30986 @subheading The @code{-exec-return} Command
30987 @findex -exec-return
30989 @subsubheading Synopsis
30995 Makes current function return immediately. Doesn't execute the inferior.
30996 Displays the new current frame.
30998 @subsubheading @value{GDBN} Command
31000 The corresponding @value{GDBN} command is @samp{return}.
31002 @subsubheading Example
31006 200-break-insert callee4
31007 200^done,bkpt=@{number="1",addr="0x00010734",
31008 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31013 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31014 frame=@{func="callee4",args=[],
31015 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31016 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
31022 111^done,frame=@{level="0",func="callee3",
31023 args=[@{name="strarg",
31024 value="0x11940 \"A string argument.\""@}],
31025 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31026 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
31031 @subheading The @code{-exec-run} Command
31034 @subsubheading Synopsis
31037 -exec-run [--all | --thread-group N]
31040 Starts execution of the inferior from the beginning. The inferior
31041 executes until either a breakpoint is encountered or the program
31042 exits. In the latter case the output will include an exit code, if
31043 the program has exited exceptionally.
31045 When no option is specified, the current inferior is started. If the
31046 @samp{--thread-group} option is specified, it should refer to a thread
31047 group of type @samp{process}, and that thread group will be started.
31048 If the @samp{--all} option is specified, then all inferiors will be started.
31050 @subsubheading @value{GDBN} Command
31052 The corresponding @value{GDBN} command is @samp{run}.
31054 @subsubheading Examples
31059 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
31064 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
31065 frame=@{func="main",args=[],file="recursive2.c",
31066 fullname="/home/foo/bar/recursive2.c",line="4"@}
31071 Program exited normally:
31079 *stopped,reason="exited-normally"
31084 Program exited exceptionally:
31092 *stopped,reason="exited",exit-code="01"
31096 Another way the program can terminate is if it receives a signal such as
31097 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31101 *stopped,reason="exited-signalled",signal-name="SIGINT",
31102 signal-meaning="Interrupt"
31106 @c @subheading -exec-signal
31109 @subheading The @code{-exec-step} Command
31112 @subsubheading Synopsis
31115 -exec-step [--reverse]
31118 Resumes execution of the inferior program, stopping when the beginning
31119 of the next source line is reached, if the next source line is not a
31120 function call. If it is, stop at the first instruction of the called
31121 function. If the @samp{--reverse} option is specified, resumes reverse
31122 execution of the inferior program, stopping at the beginning of the
31123 previously executed source line.
31125 @subsubheading @value{GDBN} Command
31127 The corresponding @value{GDBN} command is @samp{step}.
31129 @subsubheading Example
31131 Stepping into a function:
31137 *stopped,reason="end-stepping-range",
31138 frame=@{func="foo",args=[@{name="a",value="10"@},
31139 @{name="b",value="0"@}],file="recursive2.c",
31140 fullname="/home/foo/bar/recursive2.c",line="11"@}
31150 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31155 @subheading The @code{-exec-step-instruction} Command
31156 @findex -exec-step-instruction
31158 @subsubheading Synopsis
31161 -exec-step-instruction [--reverse]
31164 Resumes the inferior which executes one machine instruction. If the
31165 @samp{--reverse} option is specified, resumes reverse execution of the
31166 inferior program, stopping at the previously executed instruction.
31167 The output, once @value{GDBN} has stopped, will vary depending on
31168 whether we have stopped in the middle of a source line or not. In the
31169 former case, the address at which the program stopped will be printed
31172 @subsubheading @value{GDBN} Command
31174 The corresponding @value{GDBN} command is @samp{stepi}.
31176 @subsubheading Example
31180 -exec-step-instruction
31184 *stopped,reason="end-stepping-range",
31185 frame=@{func="foo",args=[],file="try.c",
31186 fullname="/home/foo/bar/try.c",line="10"@}
31188 -exec-step-instruction
31192 *stopped,reason="end-stepping-range",
31193 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31194 fullname="/home/foo/bar/try.c",line="10"@}
31199 @subheading The @code{-exec-until} Command
31200 @findex -exec-until
31202 @subsubheading Synopsis
31205 -exec-until [ @var{location} ]
31208 Executes the inferior until the @var{location} specified in the
31209 argument is reached. If there is no argument, the inferior executes
31210 until a source line greater than the current one is reached. The
31211 reason for stopping in this case will be @samp{location-reached}.
31213 @subsubheading @value{GDBN} Command
31215 The corresponding @value{GDBN} command is @samp{until}.
31217 @subsubheading Example
31221 -exec-until recursive2.c:6
31225 *stopped,reason="location-reached",frame=@{func="main",args=[],
31226 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31231 @subheading -file-clear
31232 Is this going away????
31235 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31236 @node GDB/MI Stack Manipulation
31237 @section @sc{gdb/mi} Stack Manipulation Commands
31239 @subheading The @code{-enable-frame-filters} Command
31240 @findex -enable-frame-filters
31243 -enable-frame-filters
31246 @value{GDBN} allows Python-based frame filters to affect the output of
31247 the MI commands relating to stack traces. As there is no way to
31248 implement this in a fully backward-compatible way, a front end must
31249 request that this functionality be enabled.
31251 Once enabled, this feature cannot be disabled.
31253 Note that if Python support has not been compiled into @value{GDBN},
31254 this command will still succeed (and do nothing).
31256 @subheading The @code{-stack-info-frame} Command
31257 @findex -stack-info-frame
31259 @subsubheading Synopsis
31265 Get info on the selected frame.
31267 @subsubheading @value{GDBN} Command
31269 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31270 (without arguments).
31272 @subsubheading Example
31277 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31278 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31279 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31283 @subheading The @code{-stack-info-depth} Command
31284 @findex -stack-info-depth
31286 @subsubheading Synopsis
31289 -stack-info-depth [ @var{max-depth} ]
31292 Return the depth of the stack. If the integer argument @var{max-depth}
31293 is specified, do not count beyond @var{max-depth} frames.
31295 @subsubheading @value{GDBN} Command
31297 There's no equivalent @value{GDBN} command.
31299 @subsubheading Example
31301 For a stack with frame levels 0 through 11:
31308 -stack-info-depth 4
31311 -stack-info-depth 12
31314 -stack-info-depth 11
31317 -stack-info-depth 13
31322 @anchor{-stack-list-arguments}
31323 @subheading The @code{-stack-list-arguments} Command
31324 @findex -stack-list-arguments
31326 @subsubheading Synopsis
31329 -stack-list-arguments [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31330 [ @var{low-frame} @var{high-frame} ]
31333 Display a list of the arguments for the frames between @var{low-frame}
31334 and @var{high-frame} (inclusive). If @var{low-frame} and
31335 @var{high-frame} are not provided, list the arguments for the whole
31336 call stack. If the two arguments are equal, show the single frame
31337 at the corresponding level. It is an error if @var{low-frame} is
31338 larger than the actual number of frames. On the other hand,
31339 @var{high-frame} may be larger than the actual number of frames, in
31340 which case only existing frames will be returned.
31342 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31343 the variables; if it is 1 or @code{--all-values}, print also their
31344 values; and if it is 2 or @code{--simple-values}, print the name,
31345 type and value for simple data types, and the name and type for arrays,
31346 structures and unions. If the option @code{--no-frame-filters} is
31347 supplied, then Python frame filters will not be executed.
31349 If the @code{--skip-unavailable} option is specified, arguments that
31350 are not available are not listed. Partially available arguments
31351 are still displayed, however.
31353 Use of this command to obtain arguments in a single frame is
31354 deprecated in favor of the @samp{-stack-list-variables} command.
31356 @subsubheading @value{GDBN} Command
31358 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31359 @samp{gdb_get_args} command which partially overlaps with the
31360 functionality of @samp{-stack-list-arguments}.
31362 @subsubheading Example
31369 frame=@{level="0",addr="0x00010734",func="callee4",
31370 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31371 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31372 frame=@{level="1",addr="0x0001076c",func="callee3",
31373 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31374 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31375 frame=@{level="2",addr="0x0001078c",func="callee2",
31376 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31377 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31378 frame=@{level="3",addr="0x000107b4",func="callee1",
31379 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31380 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31381 frame=@{level="4",addr="0x000107e0",func="main",
31382 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31383 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31385 -stack-list-arguments 0
31388 frame=@{level="0",args=[]@},
31389 frame=@{level="1",args=[name="strarg"]@},
31390 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31391 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31392 frame=@{level="4",args=[]@}]
31394 -stack-list-arguments 1
31397 frame=@{level="0",args=[]@},
31399 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31400 frame=@{level="2",args=[
31401 @{name="intarg",value="2"@},
31402 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31403 @{frame=@{level="3",args=[
31404 @{name="intarg",value="2"@},
31405 @{name="strarg",value="0x11940 \"A string argument.\""@},
31406 @{name="fltarg",value="3.5"@}]@},
31407 frame=@{level="4",args=[]@}]
31409 -stack-list-arguments 0 2 2
31410 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31412 -stack-list-arguments 1 2 2
31413 ^done,stack-args=[frame=@{level="2",
31414 args=[@{name="intarg",value="2"@},
31415 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31419 @c @subheading -stack-list-exception-handlers
31422 @anchor{-stack-list-frames}
31423 @subheading The @code{-stack-list-frames} Command
31424 @findex -stack-list-frames
31426 @subsubheading Synopsis
31429 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31432 List the frames currently on the stack. For each frame it displays the
31437 The frame number, 0 being the topmost frame, i.e., the innermost function.
31439 The @code{$pc} value for that frame.
31443 File name of the source file where the function lives.
31444 @item @var{fullname}
31445 The full file name of the source file where the function lives.
31447 Line number corresponding to the @code{$pc}.
31449 The shared library where this function is defined. This is only given
31450 if the frame's function is not known.
31453 If invoked without arguments, this command prints a backtrace for the
31454 whole stack. If given two integer arguments, it shows the frames whose
31455 levels are between the two arguments (inclusive). If the two arguments
31456 are equal, it shows the single frame at the corresponding level. It is
31457 an error if @var{low-frame} is larger than the actual number of
31458 frames. On the other hand, @var{high-frame} may be larger than the
31459 actual number of frames, in which case only existing frames will be
31460 returned. If the option @code{--no-frame-filters} is supplied, then
31461 Python frame filters will not be executed.
31463 @subsubheading @value{GDBN} Command
31465 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31467 @subsubheading Example
31469 Full stack backtrace:
31475 [frame=@{level="0",addr="0x0001076c",func="foo",
31476 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
31477 frame=@{level="1",addr="0x000107a4",func="foo",
31478 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31479 frame=@{level="2",addr="0x000107a4",func="foo",
31480 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31481 frame=@{level="3",addr="0x000107a4",func="foo",
31482 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31483 frame=@{level="4",addr="0x000107a4",func="foo",
31484 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31485 frame=@{level="5",addr="0x000107a4",func="foo",
31486 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31487 frame=@{level="6",addr="0x000107a4",func="foo",
31488 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31489 frame=@{level="7",addr="0x000107a4",func="foo",
31490 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31491 frame=@{level="8",addr="0x000107a4",func="foo",
31492 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31493 frame=@{level="9",addr="0x000107a4",func="foo",
31494 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31495 frame=@{level="10",addr="0x000107a4",func="foo",
31496 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31497 frame=@{level="11",addr="0x00010738",func="main",
31498 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
31502 Show frames between @var{low_frame} and @var{high_frame}:
31506 -stack-list-frames 3 5
31508 [frame=@{level="3",addr="0x000107a4",func="foo",
31509 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31510 frame=@{level="4",addr="0x000107a4",func="foo",
31511 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31512 frame=@{level="5",addr="0x000107a4",func="foo",
31513 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31517 Show a single frame:
31521 -stack-list-frames 3 3
31523 [frame=@{level="3",addr="0x000107a4",func="foo",
31524 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31529 @subheading The @code{-stack-list-locals} Command
31530 @findex -stack-list-locals
31531 @anchor{-stack-list-locals}
31533 @subsubheading Synopsis
31536 -stack-list-locals [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31539 Display the local variable names for the selected frame. If
31540 @var{print-values} is 0 or @code{--no-values}, print only the names of
31541 the variables; if it is 1 or @code{--all-values}, print also their
31542 values; and if it is 2 or @code{--simple-values}, print the name,
31543 type and value for simple data types, and the name and type for arrays,
31544 structures and unions. In this last case, a frontend can immediately
31545 display the value of simple data types and create variable objects for
31546 other data types when the user wishes to explore their values in
31547 more detail. If the option @code{--no-frame-filters} is supplied, then
31548 Python frame filters will not be executed.
31550 If the @code{--skip-unavailable} option is specified, local variables
31551 that are not available are not listed. Partially available local
31552 variables are still displayed, however.
31554 This command is deprecated in favor of the
31555 @samp{-stack-list-variables} command.
31557 @subsubheading @value{GDBN} Command
31559 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
31561 @subsubheading Example
31565 -stack-list-locals 0
31566 ^done,locals=[name="A",name="B",name="C"]
31568 -stack-list-locals --all-values
31569 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
31570 @{name="C",value="@{1, 2, 3@}"@}]
31571 -stack-list-locals --simple-values
31572 ^done,locals=[@{name="A",type="int",value="1"@},
31573 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
31577 @anchor{-stack-list-variables}
31578 @subheading The @code{-stack-list-variables} Command
31579 @findex -stack-list-variables
31581 @subsubheading Synopsis
31584 -stack-list-variables [ --no-frame-filters ] [ --skip-unavailable ] @var{print-values}
31587 Display the names of local variables and function arguments for the selected frame. If
31588 @var{print-values} is 0 or @code{--no-values}, print only the names of
31589 the variables; if it is 1 or @code{--all-values}, print also their
31590 values; and if it is 2 or @code{--simple-values}, print the name,
31591 type and value for simple data types, and the name and type for arrays,
31592 structures and unions. If the option @code{--no-frame-filters} is
31593 supplied, then Python frame filters will not be executed.
31595 If the @code{--skip-unavailable} option is specified, local variables
31596 and arguments that are not available are not listed. Partially
31597 available arguments and local variables are still displayed, however.
31599 @subsubheading Example
31603 -stack-list-variables --thread 1 --frame 0 --all-values
31604 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
31609 @subheading The @code{-stack-select-frame} Command
31610 @findex -stack-select-frame
31612 @subsubheading Synopsis
31615 -stack-select-frame @var{framenum}
31618 Change the selected frame. Select a different frame @var{framenum} on
31621 This command in deprecated in favor of passing the @samp{--frame}
31622 option to every command.
31624 @subsubheading @value{GDBN} Command
31626 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
31627 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
31629 @subsubheading Example
31633 -stack-select-frame 2
31638 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31639 @node GDB/MI Variable Objects
31640 @section @sc{gdb/mi} Variable Objects
31644 @subheading Motivation for Variable Objects in @sc{gdb/mi}
31646 For the implementation of a variable debugger window (locals, watched
31647 expressions, etc.), we are proposing the adaptation of the existing code
31648 used by @code{Insight}.
31650 The two main reasons for that are:
31654 It has been proven in practice (it is already on its second generation).
31657 It will shorten development time (needless to say how important it is
31661 The original interface was designed to be used by Tcl code, so it was
31662 slightly changed so it could be used through @sc{gdb/mi}. This section
31663 describes the @sc{gdb/mi} operations that will be available and gives some
31664 hints about their use.
31666 @emph{Note}: In addition to the set of operations described here, we
31667 expect the @sc{gui} implementation of a variable window to require, at
31668 least, the following operations:
31671 @item @code{-gdb-show} @code{output-radix}
31672 @item @code{-stack-list-arguments}
31673 @item @code{-stack-list-locals}
31674 @item @code{-stack-select-frame}
31679 @subheading Introduction to Variable Objects
31681 @cindex variable objects in @sc{gdb/mi}
31683 Variable objects are "object-oriented" MI interface for examining and
31684 changing values of expressions. Unlike some other MI interfaces that
31685 work with expressions, variable objects are specifically designed for
31686 simple and efficient presentation in the frontend. A variable object
31687 is identified by string name. When a variable object is created, the
31688 frontend specifies the expression for that variable object. The
31689 expression can be a simple variable, or it can be an arbitrary complex
31690 expression, and can even involve CPU registers. After creating a
31691 variable object, the frontend can invoke other variable object
31692 operations---for example to obtain or change the value of a variable
31693 object, or to change display format.
31695 Variable objects have hierarchical tree structure. Any variable object
31696 that corresponds to a composite type, such as structure in C, has
31697 a number of child variable objects, for example corresponding to each
31698 element of a structure. A child variable object can itself have
31699 children, recursively. Recursion ends when we reach
31700 leaf variable objects, which always have built-in types. Child variable
31701 objects are created only by explicit request, so if a frontend
31702 is not interested in the children of a particular variable object, no
31703 child will be created.
31705 For a leaf variable object it is possible to obtain its value as a
31706 string, or set the value from a string. String value can be also
31707 obtained for a non-leaf variable object, but it's generally a string
31708 that only indicates the type of the object, and does not list its
31709 contents. Assignment to a non-leaf variable object is not allowed.
31711 A frontend does not need to read the values of all variable objects each time
31712 the program stops. Instead, MI provides an update command that lists all
31713 variable objects whose values has changed since the last update
31714 operation. This considerably reduces the amount of data that must
31715 be transferred to the frontend. As noted above, children variable
31716 objects are created on demand, and only leaf variable objects have a
31717 real value. As result, gdb will read target memory only for leaf
31718 variables that frontend has created.
31720 The automatic update is not always desirable. For example, a frontend
31721 might want to keep a value of some expression for future reference,
31722 and never update it. For another example, fetching memory is
31723 relatively slow for embedded targets, so a frontend might want
31724 to disable automatic update for the variables that are either not
31725 visible on the screen, or ``closed''. This is possible using so
31726 called ``frozen variable objects''. Such variable objects are never
31727 implicitly updated.
31729 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
31730 fixed variable object, the expression is parsed when the variable
31731 object is created, including associating identifiers to specific
31732 variables. The meaning of expression never changes. For a floating
31733 variable object the values of variables whose names appear in the
31734 expressions are re-evaluated every time in the context of the current
31735 frame. Consider this example:
31740 struct work_state state;
31747 If a fixed variable object for the @code{state} variable is created in
31748 this function, and we enter the recursive call, the variable
31749 object will report the value of @code{state} in the top-level
31750 @code{do_work} invocation. On the other hand, a floating variable
31751 object will report the value of @code{state} in the current frame.
31753 If an expression specified when creating a fixed variable object
31754 refers to a local variable, the variable object becomes bound to the
31755 thread and frame in which the variable object is created. When such
31756 variable object is updated, @value{GDBN} makes sure that the
31757 thread/frame combination the variable object is bound to still exists,
31758 and re-evaluates the variable object in context of that thread/frame.
31760 The following is the complete set of @sc{gdb/mi} operations defined to
31761 access this functionality:
31763 @multitable @columnfractions .4 .6
31764 @item @strong{Operation}
31765 @tab @strong{Description}
31767 @item @code{-enable-pretty-printing}
31768 @tab enable Python-based pretty-printing
31769 @item @code{-var-create}
31770 @tab create a variable object
31771 @item @code{-var-delete}
31772 @tab delete the variable object and/or its children
31773 @item @code{-var-set-format}
31774 @tab set the display format of this variable
31775 @item @code{-var-show-format}
31776 @tab show the display format of this variable
31777 @item @code{-var-info-num-children}
31778 @tab tells how many children this object has
31779 @item @code{-var-list-children}
31780 @tab return a list of the object's children
31781 @item @code{-var-info-type}
31782 @tab show the type of this variable object
31783 @item @code{-var-info-expression}
31784 @tab print parent-relative expression that this variable object represents
31785 @item @code{-var-info-path-expression}
31786 @tab print full expression that this variable object represents
31787 @item @code{-var-show-attributes}
31788 @tab is this variable editable? does it exist here?
31789 @item @code{-var-evaluate-expression}
31790 @tab get the value of this variable
31791 @item @code{-var-assign}
31792 @tab set the value of this variable
31793 @item @code{-var-update}
31794 @tab update the variable and its children
31795 @item @code{-var-set-frozen}
31796 @tab set frozeness attribute
31797 @item @code{-var-set-update-range}
31798 @tab set range of children to display on update
31801 In the next subsection we describe each operation in detail and suggest
31802 how it can be used.
31804 @subheading Description And Use of Operations on Variable Objects
31806 @subheading The @code{-enable-pretty-printing} Command
31807 @findex -enable-pretty-printing
31810 -enable-pretty-printing
31813 @value{GDBN} allows Python-based visualizers to affect the output of the
31814 MI variable object commands. However, because there was no way to
31815 implement this in a fully backward-compatible way, a front end must
31816 request that this functionality be enabled.
31818 Once enabled, this feature cannot be disabled.
31820 Note that if Python support has not been compiled into @value{GDBN},
31821 this command will still succeed (and do nothing).
31823 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31824 may work differently in future versions of @value{GDBN}.
31826 @subheading The @code{-var-create} Command
31827 @findex -var-create
31829 @subsubheading Synopsis
31832 -var-create @{@var{name} | "-"@}
31833 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31836 This operation creates a variable object, which allows the monitoring of
31837 a variable, the result of an expression, a memory cell or a CPU
31840 The @var{name} parameter is the string by which the object can be
31841 referenced. It must be unique. If @samp{-} is specified, the varobj
31842 system will generate a string ``varNNNNNN'' automatically. It will be
31843 unique provided that one does not specify @var{name} of that format.
31844 The command fails if a duplicate name is found.
31846 The frame under which the expression should be evaluated can be
31847 specified by @var{frame-addr}. A @samp{*} indicates that the current
31848 frame should be used. A @samp{@@} indicates that a floating variable
31849 object must be created.
31851 @var{expression} is any expression valid on the current language set (must not
31852 begin with a @samp{*}), or one of the following:
31856 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31859 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31862 @samp{$@var{regname}} --- a CPU register name
31865 @cindex dynamic varobj
31866 A varobj's contents may be provided by a Python-based pretty-printer. In this
31867 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31868 have slightly different semantics in some cases. If the
31869 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31870 will never create a dynamic varobj. This ensures backward
31871 compatibility for existing clients.
31873 @subsubheading Result
31875 This operation returns attributes of the newly-created varobj. These
31880 The name of the varobj.
31883 The number of children of the varobj. This number is not necessarily
31884 reliable for a dynamic varobj. Instead, you must examine the
31885 @samp{has_more} attribute.
31888 The varobj's scalar value. For a varobj whose type is some sort of
31889 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31890 will not be interesting.
31893 The varobj's type. This is a string representation of the type, as
31894 would be printed by the @value{GDBN} CLI. If @samp{print object}
31895 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31896 @emph{actual} (derived) type of the object is shown rather than the
31897 @emph{declared} one.
31900 If a variable object is bound to a specific thread, then this is the
31901 thread's identifier.
31904 For a dynamic varobj, this indicates whether there appear to be any
31905 children available. For a non-dynamic varobj, this will be 0.
31908 This attribute will be present and have the value @samp{1} if the
31909 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31910 then this attribute will not be present.
31913 A dynamic varobj can supply a display hint to the front end. The
31914 value comes directly from the Python pretty-printer object's
31915 @code{display_hint} method. @xref{Pretty Printing API}.
31918 Typical output will look like this:
31921 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31922 has_more="@var{has_more}"
31926 @subheading The @code{-var-delete} Command
31927 @findex -var-delete
31929 @subsubheading Synopsis
31932 -var-delete [ -c ] @var{name}
31935 Deletes a previously created variable object and all of its children.
31936 With the @samp{-c} option, just deletes the children.
31938 Returns an error if the object @var{name} is not found.
31941 @subheading The @code{-var-set-format} Command
31942 @findex -var-set-format
31944 @subsubheading Synopsis
31947 -var-set-format @var{name} @var{format-spec}
31950 Sets the output format for the value of the object @var{name} to be
31953 @anchor{-var-set-format}
31954 The syntax for the @var{format-spec} is as follows:
31957 @var{format-spec} @expansion{}
31958 @{binary | decimal | hexadecimal | octal | natural@}
31961 The natural format is the default format choosen automatically
31962 based on the variable type (like decimal for an @code{int}, hex
31963 for pointers, etc.).
31965 For a variable with children, the format is set only on the
31966 variable itself, and the children are not affected.
31968 @subheading The @code{-var-show-format} Command
31969 @findex -var-show-format
31971 @subsubheading Synopsis
31974 -var-show-format @var{name}
31977 Returns the format used to display the value of the object @var{name}.
31980 @var{format} @expansion{}
31985 @subheading The @code{-var-info-num-children} Command
31986 @findex -var-info-num-children
31988 @subsubheading Synopsis
31991 -var-info-num-children @var{name}
31994 Returns the number of children of a variable object @var{name}:
32000 Note that this number is not completely reliable for a dynamic varobj.
32001 It will return the current number of children, but more children may
32005 @subheading The @code{-var-list-children} Command
32006 @findex -var-list-children
32008 @subsubheading Synopsis
32011 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
32013 @anchor{-var-list-children}
32015 Return a list of the children of the specified variable object and
32016 create variable objects for them, if they do not already exist. With
32017 a single argument or if @var{print-values} has a value of 0 or
32018 @code{--no-values}, print only the names of the variables; if
32019 @var{print-values} is 1 or @code{--all-values}, also print their
32020 values; and if it is 2 or @code{--simple-values} print the name and
32021 value for simple data types and just the name for arrays, structures
32024 @var{from} and @var{to}, if specified, indicate the range of children
32025 to report. If @var{from} or @var{to} is less than zero, the range is
32026 reset and all children will be reported. Otherwise, children starting
32027 at @var{from} (zero-based) and up to and excluding @var{to} will be
32030 If a child range is requested, it will only affect the current call to
32031 @code{-var-list-children}, but not future calls to @code{-var-update}.
32032 For this, you must instead use @code{-var-set-update-range}. The
32033 intent of this approach is to enable a front end to implement any
32034 update approach it likes; for example, scrolling a view may cause the
32035 front end to request more children with @code{-var-list-children}, and
32036 then the front end could call @code{-var-set-update-range} with a
32037 different range to ensure that future updates are restricted to just
32040 For each child the following results are returned:
32045 Name of the variable object created for this child.
32048 The expression to be shown to the user by the front end to designate this child.
32049 For example this may be the name of a structure member.
32051 For a dynamic varobj, this value cannot be used to form an
32052 expression. There is no way to do this at all with a dynamic varobj.
32054 For C/C@t{++} structures there are several pseudo children returned to
32055 designate access qualifiers. For these pseudo children @var{exp} is
32056 @samp{public}, @samp{private}, or @samp{protected}. In this case the
32057 type and value are not present.
32059 A dynamic varobj will not report the access qualifying
32060 pseudo-children, regardless of the language. This information is not
32061 available at all with a dynamic varobj.
32064 Number of children this child has. For a dynamic varobj, this will be
32068 The type of the child. If @samp{print object}
32069 (@pxref{Print Settings, set print object}) is set to @code{on}, the
32070 @emph{actual} (derived) type of the object is shown rather than the
32071 @emph{declared} one.
32074 If values were requested, this is the value.
32077 If this variable object is associated with a thread, this is the thread id.
32078 Otherwise this result is not present.
32081 If the variable object is frozen, this variable will be present with a value of 1.
32084 The result may have its own attributes:
32088 A dynamic varobj can supply a display hint to the front end. The
32089 value comes directly from the Python pretty-printer object's
32090 @code{display_hint} method. @xref{Pretty Printing API}.
32093 This is an integer attribute which is nonzero if there are children
32094 remaining after the end of the selected range.
32097 @subsubheading Example
32101 -var-list-children n
32102 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32103 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32105 -var-list-children --all-values n
32106 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32107 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32111 @subheading The @code{-var-info-type} Command
32112 @findex -var-info-type
32114 @subsubheading Synopsis
32117 -var-info-type @var{name}
32120 Returns the type of the specified variable @var{name}. The type is
32121 returned as a string in the same format as it is output by the
32125 type=@var{typename}
32129 @subheading The @code{-var-info-expression} Command
32130 @findex -var-info-expression
32132 @subsubheading Synopsis
32135 -var-info-expression @var{name}
32138 Returns a string that is suitable for presenting this
32139 variable object in user interface. The string is generally
32140 not valid expression in the current language, and cannot be evaluated.
32142 For example, if @code{a} is an array, and variable object
32143 @code{A} was created for @code{a}, then we'll get this output:
32146 (gdb) -var-info-expression A.1
32147 ^done,lang="C",exp="1"
32151 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
32153 Note that the output of the @code{-var-list-children} command also
32154 includes those expressions, so the @code{-var-info-expression} command
32157 @subheading The @code{-var-info-path-expression} Command
32158 @findex -var-info-path-expression
32160 @subsubheading Synopsis
32163 -var-info-path-expression @var{name}
32166 Returns an expression that can be evaluated in the current
32167 context and will yield the same value that a variable object has.
32168 Compare this with the @code{-var-info-expression} command, which
32169 result can be used only for UI presentation. Typical use of
32170 the @code{-var-info-path-expression} command is creating a
32171 watchpoint from a variable object.
32173 This command is currently not valid for children of a dynamic varobj,
32174 and will give an error when invoked on one.
32176 For example, suppose @code{C} is a C@t{++} class, derived from class
32177 @code{Base}, and that the @code{Base} class has a member called
32178 @code{m_size}. Assume a variable @code{c} is has the type of
32179 @code{C} and a variable object @code{C} was created for variable
32180 @code{c}. Then, we'll get this output:
32182 (gdb) -var-info-path-expression C.Base.public.m_size
32183 ^done,path_expr=((Base)c).m_size)
32186 @subheading The @code{-var-show-attributes} Command
32187 @findex -var-show-attributes
32189 @subsubheading Synopsis
32192 -var-show-attributes @var{name}
32195 List attributes of the specified variable object @var{name}:
32198 status=@var{attr} [ ( ,@var{attr} )* ]
32202 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32204 @subheading The @code{-var-evaluate-expression} Command
32205 @findex -var-evaluate-expression
32207 @subsubheading Synopsis
32210 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32213 Evaluates the expression that is represented by the specified variable
32214 object and returns its value as a string. The format of the string
32215 can be specified with the @samp{-f} option. The possible values of
32216 this option are the same as for @code{-var-set-format}
32217 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32218 the current display format will be used. The current display format
32219 can be changed using the @code{-var-set-format} command.
32225 Note that one must invoke @code{-var-list-children} for a variable
32226 before the value of a child variable can be evaluated.
32228 @subheading The @code{-var-assign} Command
32229 @findex -var-assign
32231 @subsubheading Synopsis
32234 -var-assign @var{name} @var{expression}
32237 Assigns the value of @var{expression} to the variable object specified
32238 by @var{name}. The object must be @samp{editable}. If the variable's
32239 value is altered by the assign, the variable will show up in any
32240 subsequent @code{-var-update} list.
32242 @subsubheading Example
32250 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32254 @subheading The @code{-var-update} Command
32255 @findex -var-update
32257 @subsubheading Synopsis
32260 -var-update [@var{print-values}] @{@var{name} | "*"@}
32263 Reevaluate the expressions corresponding to the variable object
32264 @var{name} and all its direct and indirect children, and return the
32265 list of variable objects whose values have changed; @var{name} must
32266 be a root variable object. Here, ``changed'' means that the result of
32267 @code{-var-evaluate-expression} before and after the
32268 @code{-var-update} is different. If @samp{*} is used as the variable
32269 object names, all existing variable objects are updated, except
32270 for frozen ones (@pxref{-var-set-frozen}). The option
32271 @var{print-values} determines whether both names and values, or just
32272 names are printed. The possible values of this option are the same
32273 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32274 recommended to use the @samp{--all-values} option, to reduce the
32275 number of MI commands needed on each program stop.
32277 With the @samp{*} parameter, if a variable object is bound to a
32278 currently running thread, it will not be updated, without any
32281 If @code{-var-set-update-range} was previously used on a varobj, then
32282 only the selected range of children will be reported.
32284 @code{-var-update} reports all the changed varobjs in a tuple named
32287 Each item in the change list is itself a tuple holding:
32291 The name of the varobj.
32294 If values were requested for this update, then this field will be
32295 present and will hold the value of the varobj.
32298 @anchor{-var-update}
32299 This field is a string which may take one of three values:
32303 The variable object's current value is valid.
32306 The variable object does not currently hold a valid value but it may
32307 hold one in the future if its associated expression comes back into
32311 The variable object no longer holds a valid value.
32312 This can occur when the executable file being debugged has changed,
32313 either through recompilation or by using the @value{GDBN} @code{file}
32314 command. The front end should normally choose to delete these variable
32318 In the future new values may be added to this list so the front should
32319 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32322 This is only present if the varobj is still valid. If the type
32323 changed, then this will be the string @samp{true}; otherwise it will
32326 When a varobj's type changes, its children are also likely to have
32327 become incorrect. Therefore, the varobj's children are automatically
32328 deleted when this attribute is @samp{true}. Also, the varobj's update
32329 range, when set using the @code{-var-set-update-range} command, is
32333 If the varobj's type changed, then this field will be present and will
32336 @item new_num_children
32337 For a dynamic varobj, if the number of children changed, or if the
32338 type changed, this will be the new number of children.
32340 The @samp{numchild} field in other varobj responses is generally not
32341 valid for a dynamic varobj -- it will show the number of children that
32342 @value{GDBN} knows about, but because dynamic varobjs lazily
32343 instantiate their children, this will not reflect the number of
32344 children which may be available.
32346 The @samp{new_num_children} attribute only reports changes to the
32347 number of children known by @value{GDBN}. This is the only way to
32348 detect whether an update has removed children (which necessarily can
32349 only happen at the end of the update range).
32352 The display hint, if any.
32355 This is an integer value, which will be 1 if there are more children
32356 available outside the varobj's update range.
32359 This attribute will be present and have the value @samp{1} if the
32360 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32361 then this attribute will not be present.
32364 If new children were added to a dynamic varobj within the selected
32365 update range (as set by @code{-var-set-update-range}), then they will
32366 be listed in this attribute.
32369 @subsubheading Example
32376 -var-update --all-values var1
32377 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32378 type_changed="false"@}]
32382 @subheading The @code{-var-set-frozen} Command
32383 @findex -var-set-frozen
32384 @anchor{-var-set-frozen}
32386 @subsubheading Synopsis
32389 -var-set-frozen @var{name} @var{flag}
32392 Set the frozenness flag on the variable object @var{name}. The
32393 @var{flag} parameter should be either @samp{1} to make the variable
32394 frozen or @samp{0} to make it unfrozen. If a variable object is
32395 frozen, then neither itself, nor any of its children, are
32396 implicitly updated by @code{-var-update} of
32397 a parent variable or by @code{-var-update *}. Only
32398 @code{-var-update} of the variable itself will update its value and
32399 values of its children. After a variable object is unfrozen, it is
32400 implicitly updated by all subsequent @code{-var-update} operations.
32401 Unfreezing a variable does not update it, only subsequent
32402 @code{-var-update} does.
32404 @subsubheading Example
32408 -var-set-frozen V 1
32413 @subheading The @code{-var-set-update-range} command
32414 @findex -var-set-update-range
32415 @anchor{-var-set-update-range}
32417 @subsubheading Synopsis
32420 -var-set-update-range @var{name} @var{from} @var{to}
32423 Set the range of children to be returned by future invocations of
32424 @code{-var-update}.
32426 @var{from} and @var{to} indicate the range of children to report. If
32427 @var{from} or @var{to} is less than zero, the range is reset and all
32428 children will be reported. Otherwise, children starting at @var{from}
32429 (zero-based) and up to and excluding @var{to} will be reported.
32431 @subsubheading Example
32435 -var-set-update-range V 1 2
32439 @subheading The @code{-var-set-visualizer} command
32440 @findex -var-set-visualizer
32441 @anchor{-var-set-visualizer}
32443 @subsubheading Synopsis
32446 -var-set-visualizer @var{name} @var{visualizer}
32449 Set a visualizer for the variable object @var{name}.
32451 @var{visualizer} is the visualizer to use. The special value
32452 @samp{None} means to disable any visualizer in use.
32454 If not @samp{None}, @var{visualizer} must be a Python expression.
32455 This expression must evaluate to a callable object which accepts a
32456 single argument. @value{GDBN} will call this object with the value of
32457 the varobj @var{name} as an argument (this is done so that the same
32458 Python pretty-printing code can be used for both the CLI and MI).
32459 When called, this object must return an object which conforms to the
32460 pretty-printing interface (@pxref{Pretty Printing API}).
32462 The pre-defined function @code{gdb.default_visualizer} may be used to
32463 select a visualizer by following the built-in process
32464 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32465 a varobj is created, and so ordinarily is not needed.
32467 This feature is only available if Python support is enabled. The MI
32468 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
32469 can be used to check this.
32471 @subsubheading Example
32473 Resetting the visualizer:
32477 -var-set-visualizer V None
32481 Reselecting the default (type-based) visualizer:
32485 -var-set-visualizer V gdb.default_visualizer
32489 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32490 can be used to instantiate this class for a varobj:
32494 -var-set-visualizer V "lambda val: SomeClass()"
32498 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32499 @node GDB/MI Data Manipulation
32500 @section @sc{gdb/mi} Data Manipulation
32502 @cindex data manipulation, in @sc{gdb/mi}
32503 @cindex @sc{gdb/mi}, data manipulation
32504 This section describes the @sc{gdb/mi} commands that manipulate data:
32505 examine memory and registers, evaluate expressions, etc.
32507 @c REMOVED FROM THE INTERFACE.
32508 @c @subheading -data-assign
32509 @c Change the value of a program variable. Plenty of side effects.
32510 @c @subsubheading GDB Command
32512 @c @subsubheading Example
32515 @subheading The @code{-data-disassemble} Command
32516 @findex -data-disassemble
32518 @subsubheading Synopsis
32522 [ -s @var{start-addr} -e @var{end-addr} ]
32523 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
32531 @item @var{start-addr}
32532 is the beginning address (or @code{$pc})
32533 @item @var{end-addr}
32535 @item @var{filename}
32536 is the name of the file to disassemble
32537 @item @var{linenum}
32538 is the line number to disassemble around
32540 is the number of disassembly lines to be produced. If it is -1,
32541 the whole function will be disassembled, in case no @var{end-addr} is
32542 specified. If @var{end-addr} is specified as a non-zero value, and
32543 @var{lines} is lower than the number of disassembly lines between
32544 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
32545 displayed; if @var{lines} is higher than the number of lines between
32546 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
32549 is either 0 (meaning only disassembly), 1 (meaning mixed source and
32550 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
32551 mixed source and disassembly with raw opcodes).
32554 @subsubheading Result
32556 The result of the @code{-data-disassemble} command will be a list named
32557 @samp{asm_insns}, the contents of this list depend on the @var{mode}
32558 used with the @code{-data-disassemble} command.
32560 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
32565 The address at which this instruction was disassembled.
32568 The name of the function this instruction is within.
32571 The decimal offset in bytes from the start of @samp{func-name}.
32574 The text disassembly for this @samp{address}.
32577 This field is only present for mode 2. This contains the raw opcode
32578 bytes for the @samp{inst} field.
32582 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
32583 @samp{src_and_asm_line}, each of which has the following fields:
32587 The line number within @samp{file}.
32590 The file name from the compilation unit. This might be an absolute
32591 file name or a relative file name depending on the compile command
32595 Absolute file name of @samp{file}. It is converted to a canonical form
32596 using the source file search path
32597 (@pxref{Source Path, ,Specifying Source Directories})
32598 and after resolving all the symbolic links.
32600 If the source file is not found this field will contain the path as
32601 present in the debug information.
32603 @item line_asm_insn
32604 This is a list of tuples containing the disassembly for @samp{line} in
32605 @samp{file}. The fields of each tuple are the same as for
32606 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
32607 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
32612 Note that whatever included in the @samp{inst} field, is not
32613 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
32616 @subsubheading @value{GDBN} Command
32618 The corresponding @value{GDBN} command is @samp{disassemble}.
32620 @subsubheading Example
32622 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
32626 -data-disassemble -s $pc -e "$pc + 20" -- 0
32629 @{address="0x000107c0",func-name="main",offset="4",
32630 inst="mov 2, %o0"@},
32631 @{address="0x000107c4",func-name="main",offset="8",
32632 inst="sethi %hi(0x11800), %o2"@},
32633 @{address="0x000107c8",func-name="main",offset="12",
32634 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
32635 @{address="0x000107cc",func-name="main",offset="16",
32636 inst="sethi %hi(0x11800), %o2"@},
32637 @{address="0x000107d0",func-name="main",offset="20",
32638 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
32642 Disassemble the whole @code{main} function. Line 32 is part of
32646 -data-disassemble -f basics.c -l 32 -- 0
32648 @{address="0x000107bc",func-name="main",offset="0",
32649 inst="save %sp, -112, %sp"@},
32650 @{address="0x000107c0",func-name="main",offset="4",
32651 inst="mov 2, %o0"@},
32652 @{address="0x000107c4",func-name="main",offset="8",
32653 inst="sethi %hi(0x11800), %o2"@},
32655 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
32656 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
32660 Disassemble 3 instructions from the start of @code{main}:
32664 -data-disassemble -f basics.c -l 32 -n 3 -- 0
32666 @{address="0x000107bc",func-name="main",offset="0",
32667 inst="save %sp, -112, %sp"@},
32668 @{address="0x000107c0",func-name="main",offset="4",
32669 inst="mov 2, %o0"@},
32670 @{address="0x000107c4",func-name="main",offset="8",
32671 inst="sethi %hi(0x11800), %o2"@}]
32675 Disassemble 3 instructions from the start of @code{main} in mixed mode:
32679 -data-disassemble -f basics.c -l 32 -n 3 -- 1
32681 src_and_asm_line=@{line="31",
32682 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32683 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32684 line_asm_insn=[@{address="0x000107bc",
32685 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
32686 src_and_asm_line=@{line="32",
32687 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32688 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32689 line_asm_insn=[@{address="0x000107c0",
32690 func-name="main",offset="4",inst="mov 2, %o0"@},
32691 @{address="0x000107c4",func-name="main",offset="8",
32692 inst="sethi %hi(0x11800), %o2"@}]@}]
32697 @subheading The @code{-data-evaluate-expression} Command
32698 @findex -data-evaluate-expression
32700 @subsubheading Synopsis
32703 -data-evaluate-expression @var{expr}
32706 Evaluate @var{expr} as an expression. The expression could contain an
32707 inferior function call. The function call will execute synchronously.
32708 If the expression contains spaces, it must be enclosed in double quotes.
32710 @subsubheading @value{GDBN} Command
32712 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
32713 @samp{call}. In @code{gdbtk} only, there's a corresponding
32714 @samp{gdb_eval} command.
32716 @subsubheading Example
32718 In the following example, the numbers that precede the commands are the
32719 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
32720 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
32724 211-data-evaluate-expression A
32727 311-data-evaluate-expression &A
32728 311^done,value="0xefffeb7c"
32730 411-data-evaluate-expression A+3
32733 511-data-evaluate-expression "A + 3"
32739 @subheading The @code{-data-list-changed-registers} Command
32740 @findex -data-list-changed-registers
32742 @subsubheading Synopsis
32745 -data-list-changed-registers
32748 Display a list of the registers that have changed.
32750 @subsubheading @value{GDBN} Command
32752 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32753 has the corresponding command @samp{gdb_changed_register_list}.
32755 @subsubheading Example
32757 On a PPC MBX board:
32765 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32766 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32769 -data-list-changed-registers
32770 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32771 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32772 "24","25","26","27","28","30","31","64","65","66","67","69"]
32777 @subheading The @code{-data-list-register-names} Command
32778 @findex -data-list-register-names
32780 @subsubheading Synopsis
32783 -data-list-register-names [ ( @var{regno} )+ ]
32786 Show a list of register names for the current target. If no arguments
32787 are given, it shows a list of the names of all the registers. If
32788 integer numbers are given as arguments, it will print a list of the
32789 names of the registers corresponding to the arguments. To ensure
32790 consistency between a register name and its number, the output list may
32791 include empty register names.
32793 @subsubheading @value{GDBN} Command
32795 @value{GDBN} does not have a command which corresponds to
32796 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32797 corresponding command @samp{gdb_regnames}.
32799 @subsubheading Example
32801 For the PPC MBX board:
32804 -data-list-register-names
32805 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32806 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32807 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32808 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32809 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32810 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32811 "", "pc","ps","cr","lr","ctr","xer"]
32813 -data-list-register-names 1 2 3
32814 ^done,register-names=["r1","r2","r3"]
32818 @subheading The @code{-data-list-register-values} Command
32819 @findex -data-list-register-values
32821 @subsubheading Synopsis
32824 -data-list-register-values
32825 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32828 Display the registers' contents. @var{fmt} is the format according to
32829 which the registers' contents are to be returned, followed by an optional
32830 list of numbers specifying the registers to display. A missing list of
32831 numbers indicates that the contents of all the registers must be
32832 returned. The @code{--skip-unavailable} option indicates that only
32833 the available registers are to be returned.
32835 Allowed formats for @var{fmt} are:
32852 @subsubheading @value{GDBN} Command
32854 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32855 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32857 @subsubheading Example
32859 For a PPC MBX board (note: line breaks are for readability only, they
32860 don't appear in the actual output):
32864 -data-list-register-values r 64 65
32865 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32866 @{number="65",value="0x00029002"@}]
32868 -data-list-register-values x
32869 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32870 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32871 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32872 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32873 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32874 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32875 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32876 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32877 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32878 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32879 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32880 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32881 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32882 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32883 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32884 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32885 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32886 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
32887 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
32888 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
32889 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
32890 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
32891 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
32892 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
32893 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
32894 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
32895 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
32896 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
32897 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
32898 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
32899 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
32900 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
32901 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
32902 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
32903 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
32904 @{number="69",value="0x20002b03"@}]
32909 @subheading The @code{-data-read-memory} Command
32910 @findex -data-read-memory
32912 This command is deprecated, use @code{-data-read-memory-bytes} instead.
32914 @subsubheading Synopsis
32917 -data-read-memory [ -o @var{byte-offset} ]
32918 @var{address} @var{word-format} @var{word-size}
32919 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
32926 @item @var{address}
32927 An expression specifying the address of the first memory word to be
32928 read. Complex expressions containing embedded white space should be
32929 quoted using the C convention.
32931 @item @var{word-format}
32932 The format to be used to print the memory words. The notation is the
32933 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
32936 @item @var{word-size}
32937 The size of each memory word in bytes.
32939 @item @var{nr-rows}
32940 The number of rows in the output table.
32942 @item @var{nr-cols}
32943 The number of columns in the output table.
32946 If present, indicates that each row should include an @sc{ascii} dump. The
32947 value of @var{aschar} is used as a padding character when a byte is not a
32948 member of the printable @sc{ascii} character set (printable @sc{ascii}
32949 characters are those whose code is between 32 and 126, inclusively).
32951 @item @var{byte-offset}
32952 An offset to add to the @var{address} before fetching memory.
32955 This command displays memory contents as a table of @var{nr-rows} by
32956 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32957 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32958 (returned as @samp{total-bytes}). Should less than the requested number
32959 of bytes be returned by the target, the missing words are identified
32960 using @samp{N/A}. The number of bytes read from the target is returned
32961 in @samp{nr-bytes} and the starting address used to read memory in
32964 The address of the next/previous row or page is available in
32965 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32968 @subsubheading @value{GDBN} Command
32970 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32971 @samp{gdb_get_mem} memory read command.
32973 @subsubheading Example
32975 Read six bytes of memory starting at @code{bytes+6} but then offset by
32976 @code{-6} bytes. Format as three rows of two columns. One byte per
32977 word. Display each word in hex.
32981 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32982 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32983 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32984 prev-page="0x0000138a",memory=[
32985 @{addr="0x00001390",data=["0x00","0x01"]@},
32986 @{addr="0x00001392",data=["0x02","0x03"]@},
32987 @{addr="0x00001394",data=["0x04","0x05"]@}]
32991 Read two bytes of memory starting at address @code{shorts + 64} and
32992 display as a single word formatted in decimal.
32996 5-data-read-memory shorts+64 d 2 1 1
32997 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32998 next-row="0x00001512",prev-row="0x0000150e",
32999 next-page="0x00001512",prev-page="0x0000150e",memory=[
33000 @{addr="0x00001510",data=["128"]@}]
33004 Read thirty two bytes of memory starting at @code{bytes+16} and format
33005 as eight rows of four columns. Include a string encoding with @samp{x}
33006 used as the non-printable character.
33010 4-data-read-memory bytes+16 x 1 8 4 x
33011 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
33012 next-row="0x000013c0",prev-row="0x0000139c",
33013 next-page="0x000013c0",prev-page="0x00001380",memory=[
33014 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
33015 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
33016 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
33017 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
33018 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
33019 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
33020 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
33021 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
33025 @subheading The @code{-data-read-memory-bytes} Command
33026 @findex -data-read-memory-bytes
33028 @subsubheading Synopsis
33031 -data-read-memory-bytes [ -o @var{byte-offset} ]
33032 @var{address} @var{count}
33039 @item @var{address}
33040 An expression specifying the address of the first memory word to be
33041 read. Complex expressions containing embedded white space should be
33042 quoted using the C convention.
33045 The number of bytes to read. This should be an integer literal.
33047 @item @var{byte-offset}
33048 The offsets in bytes relative to @var{address} at which to start
33049 reading. This should be an integer literal. This option is provided
33050 so that a frontend is not required to first evaluate address and then
33051 perform address arithmetics itself.
33055 This command attempts to read all accessible memory regions in the
33056 specified range. First, all regions marked as unreadable in the memory
33057 map (if one is defined) will be skipped. @xref{Memory Region
33058 Attributes}. Second, @value{GDBN} will attempt to read the remaining
33059 regions. For each one, if reading full region results in an errors,
33060 @value{GDBN} will try to read a subset of the region.
33062 In general, every single byte in the region may be readable or not,
33063 and the only way to read every readable byte is to try a read at
33064 every address, which is not practical. Therefore, @value{GDBN} will
33065 attempt to read all accessible bytes at either beginning or the end
33066 of the region, using a binary division scheme. This heuristic works
33067 well for reading accross a memory map boundary. Note that if a region
33068 has a readable range that is neither at the beginning or the end,
33069 @value{GDBN} will not read it.
33071 The result record (@pxref{GDB/MI Result Records}) that is output of
33072 the command includes a field named @samp{memory} whose content is a
33073 list of tuples. Each tuple represent a successfully read memory block
33074 and has the following fields:
33078 The start address of the memory block, as hexadecimal literal.
33081 The end address of the memory block, as hexadecimal literal.
33084 The offset of the memory block, as hexadecimal literal, relative to
33085 the start address passed to @code{-data-read-memory-bytes}.
33088 The contents of the memory block, in hex.
33094 @subsubheading @value{GDBN} Command
33096 The corresponding @value{GDBN} command is @samp{x}.
33098 @subsubheading Example
33102 -data-read-memory-bytes &a 10
33103 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33105 contents="01000000020000000300"@}]
33110 @subheading The @code{-data-write-memory-bytes} Command
33111 @findex -data-write-memory-bytes
33113 @subsubheading Synopsis
33116 -data-write-memory-bytes @var{address} @var{contents}
33117 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33124 @item @var{address}
33125 An expression specifying the address of the first memory word to be
33126 read. Complex expressions containing embedded white space should be
33127 quoted using the C convention.
33129 @item @var{contents}
33130 The hex-encoded bytes to write.
33133 Optional argument indicating the number of bytes to be written. If @var{count}
33134 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33135 write @var{contents} until it fills @var{count} bytes.
33139 @subsubheading @value{GDBN} Command
33141 There's no corresponding @value{GDBN} command.
33143 @subsubheading Example
33147 -data-write-memory-bytes &a "aabbccdd"
33154 -data-write-memory-bytes &a "aabbccdd" 16e
33159 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33160 @node GDB/MI Tracepoint Commands
33161 @section @sc{gdb/mi} Tracepoint Commands
33163 The commands defined in this section implement MI support for
33164 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33166 @subheading The @code{-trace-find} Command
33167 @findex -trace-find
33169 @subsubheading Synopsis
33172 -trace-find @var{mode} [@var{parameters}@dots{}]
33175 Find a trace frame using criteria defined by @var{mode} and
33176 @var{parameters}. The following table lists permissible
33177 modes and their parameters. For details of operation, see @ref{tfind}.
33182 No parameters are required. Stops examining trace frames.
33185 An integer is required as parameter. Selects tracepoint frame with
33188 @item tracepoint-number
33189 An integer is required as parameter. Finds next
33190 trace frame that corresponds to tracepoint with the specified number.
33193 An address is required as parameter. Finds
33194 next trace frame that corresponds to any tracepoint at the specified
33197 @item pc-inside-range
33198 Two addresses are required as parameters. Finds next trace
33199 frame that corresponds to a tracepoint at an address inside the
33200 specified range. Both bounds are considered to be inside the range.
33202 @item pc-outside-range
33203 Two addresses are required as parameters. Finds
33204 next trace frame that corresponds to a tracepoint at an address outside
33205 the specified range. Both bounds are considered to be inside the range.
33208 Line specification is required as parameter. @xref{Specify Location}.
33209 Finds next trace frame that corresponds to a tracepoint at
33210 the specified location.
33214 If @samp{none} was passed as @var{mode}, the response does not
33215 have fields. Otherwise, the response may have the following fields:
33219 This field has either @samp{0} or @samp{1} as the value, depending
33220 on whether a matching tracepoint was found.
33223 The index of the found traceframe. This field is present iff
33224 the @samp{found} field has value of @samp{1}.
33227 The index of the found tracepoint. This field is present iff
33228 the @samp{found} field has value of @samp{1}.
33231 The information about the frame corresponding to the found trace
33232 frame. This field is present only if a trace frame was found.
33233 @xref{GDB/MI Frame Information}, for description of this field.
33237 @subsubheading @value{GDBN} Command
33239 The corresponding @value{GDBN} command is @samp{tfind}.
33241 @subheading -trace-define-variable
33242 @findex -trace-define-variable
33244 @subsubheading Synopsis
33247 -trace-define-variable @var{name} [ @var{value} ]
33250 Create trace variable @var{name} if it does not exist. If
33251 @var{value} is specified, sets the initial value of the specified
33252 trace variable to that value. Note that the @var{name} should start
33253 with the @samp{$} character.
33255 @subsubheading @value{GDBN} Command
33257 The corresponding @value{GDBN} command is @samp{tvariable}.
33259 @subheading The @code{-trace-frame-collected} Command
33260 @findex -trace-frame-collected
33262 @subsubheading Synopsis
33265 -trace-frame-collected
33266 [--var-print-values @var{var_pval}]
33267 [--comp-print-values @var{comp_pval}]
33268 [--registers-format @var{regformat}]
33269 [--memory-contents]
33272 This command returns the set of collected objects, register names,
33273 trace state variable names, memory ranges and computed expressions
33274 that have been collected at a particular trace frame. The optional
33275 parameters to the command affect the output format in different ways.
33276 See the output description table below for more details.
33278 The reported names can be used in the normal manner to create
33279 varobjs and inspect the objects themselves. The items returned by
33280 this command are categorized so that it is clear which is a variable,
33281 which is a register, which is a trace state variable, which is a
33282 memory range and which is a computed expression.
33284 For instance, if the actions were
33286 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33287 collect *(int*)0xaf02bef0@@40
33291 the object collected in its entirety would be @code{myVar}. The
33292 object @code{myArray} would be partially collected, because only the
33293 element at index @code{myIndex} would be collected. The remaining
33294 objects would be computed expressions.
33296 An example output would be:
33300 -trace-frame-collected
33302 explicit-variables=[@{name="myVar",value="1"@}],
33303 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33304 @{name="myObj.field",value="0"@},
33305 @{name="myPtr->field",value="1"@},
33306 @{name="myCount + 2",value="3"@},
33307 @{name="$tvar1 + 1",value="43970027"@}],
33308 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33309 @{number="1",value="0x0"@},
33310 @{number="2",value="0x4"@},
33312 @{number="125",value="0x0"@}],
33313 tvars=[@{name="$tvar1",current="43970026"@}],
33314 memory=[@{address="0x0000000000602264",length="4"@},
33315 @{address="0x0000000000615bc0",length="4"@}]
33322 @item explicit-variables
33323 The set of objects that have been collected in their entirety (as
33324 opposed to collecting just a few elements of an array or a few struct
33325 members). For each object, its name and value are printed.
33326 The @code{--var-print-values} option affects how or whether the value
33327 field is output. If @var{var_pval} is 0, then print only the names;
33328 if it is 1, print also their values; and if it is 2, print the name,
33329 type and value for simple data types, and the name and type for
33330 arrays, structures and unions.
33332 @item computed-expressions
33333 The set of computed expressions that have been collected at the
33334 current trace frame. The @code{--comp-print-values} option affects
33335 this set like the @code{--var-print-values} option affects the
33336 @code{explicit-variables} set. See above.
33339 The registers that have been collected at the current trace frame.
33340 For each register collected, the name and current value are returned.
33341 The value is formatted according to the @code{--registers-format}
33342 option. See the @command{-data-list-register-values} command for a
33343 list of the allowed formats. The default is @samp{x}.
33346 The trace state variables that have been collected at the current
33347 trace frame. For each trace state variable collected, the name and
33348 current value are returned.
33351 The set of memory ranges that have been collected at the current trace
33352 frame. Its content is a list of tuples. Each tuple represents a
33353 collected memory range and has the following fields:
33357 The start address of the memory range, as hexadecimal literal.
33360 The length of the memory range, as decimal literal.
33363 The contents of the memory block, in hex. This field is only present
33364 if the @code{--memory-contents} option is specified.
33370 @subsubheading @value{GDBN} Command
33372 There is no corresponding @value{GDBN} command.
33374 @subsubheading Example
33376 @subheading -trace-list-variables
33377 @findex -trace-list-variables
33379 @subsubheading Synopsis
33382 -trace-list-variables
33385 Return a table of all defined trace variables. Each element of the
33386 table has the following fields:
33390 The name of the trace variable. This field is always present.
33393 The initial value. This is a 64-bit signed integer. This
33394 field is always present.
33397 The value the trace variable has at the moment. This is a 64-bit
33398 signed integer. This field is absent iff current value is
33399 not defined, for example if the trace was never run, or is
33404 @subsubheading @value{GDBN} Command
33406 The corresponding @value{GDBN} command is @samp{tvariables}.
33408 @subsubheading Example
33412 -trace-list-variables
33413 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33414 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33415 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33416 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33417 body=[variable=@{name="$trace_timestamp",initial="0"@}
33418 variable=@{name="$foo",initial="10",current="15"@}]@}
33422 @subheading -trace-save
33423 @findex -trace-save
33425 @subsubheading Synopsis
33428 -trace-save [-r ] @var{filename}
33431 Saves the collected trace data to @var{filename}. Without the
33432 @samp{-r} option, the data is downloaded from the target and saved
33433 in a local file. With the @samp{-r} option the target is asked
33434 to perform the save.
33436 @subsubheading @value{GDBN} Command
33438 The corresponding @value{GDBN} command is @samp{tsave}.
33441 @subheading -trace-start
33442 @findex -trace-start
33444 @subsubheading Synopsis
33450 Starts a tracing experiments. The result of this command does not
33453 @subsubheading @value{GDBN} Command
33455 The corresponding @value{GDBN} command is @samp{tstart}.
33457 @subheading -trace-status
33458 @findex -trace-status
33460 @subsubheading Synopsis
33466 Obtains the status of a tracing experiment. The result may include
33467 the following fields:
33472 May have a value of either @samp{0}, when no tracing operations are
33473 supported, @samp{1}, when all tracing operations are supported, or
33474 @samp{file} when examining trace file. In the latter case, examining
33475 of trace frame is possible but new tracing experiement cannot be
33476 started. This field is always present.
33479 May have a value of either @samp{0} or @samp{1} depending on whether
33480 tracing experiement is in progress on target. This field is present
33481 if @samp{supported} field is not @samp{0}.
33484 Report the reason why the tracing was stopped last time. This field
33485 may be absent iff tracing was never stopped on target yet. The
33486 value of @samp{request} means the tracing was stopped as result of
33487 the @code{-trace-stop} command. The value of @samp{overflow} means
33488 the tracing buffer is full. The value of @samp{disconnection} means
33489 tracing was automatically stopped when @value{GDBN} has disconnected.
33490 The value of @samp{passcount} means tracing was stopped when a
33491 tracepoint was passed a maximal number of times for that tracepoint.
33492 This field is present if @samp{supported} field is not @samp{0}.
33494 @item stopping-tracepoint
33495 The number of tracepoint whose passcount as exceeded. This field is
33496 present iff the @samp{stop-reason} field has the value of
33500 @itemx frames-created
33501 The @samp{frames} field is a count of the total number of trace frames
33502 in the trace buffer, while @samp{frames-created} is the total created
33503 during the run, including ones that were discarded, such as when a
33504 circular trace buffer filled up. Both fields are optional.
33508 These fields tell the current size of the tracing buffer and the
33509 remaining space. These fields are optional.
33512 The value of the circular trace buffer flag. @code{1} means that the
33513 trace buffer is circular and old trace frames will be discarded if
33514 necessary to make room, @code{0} means that the trace buffer is linear
33518 The value of the disconnected tracing flag. @code{1} means that
33519 tracing will continue after @value{GDBN} disconnects, @code{0} means
33520 that the trace run will stop.
33523 The filename of the trace file being examined. This field is
33524 optional, and only present when examining a trace file.
33528 @subsubheading @value{GDBN} Command
33530 The corresponding @value{GDBN} command is @samp{tstatus}.
33532 @subheading -trace-stop
33533 @findex -trace-stop
33535 @subsubheading Synopsis
33541 Stops a tracing experiment. The result of this command has the same
33542 fields as @code{-trace-status}, except that the @samp{supported} and
33543 @samp{running} fields are not output.
33545 @subsubheading @value{GDBN} Command
33547 The corresponding @value{GDBN} command is @samp{tstop}.
33550 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33551 @node GDB/MI Symbol Query
33552 @section @sc{gdb/mi} Symbol Query Commands
33556 @subheading The @code{-symbol-info-address} Command
33557 @findex -symbol-info-address
33559 @subsubheading Synopsis
33562 -symbol-info-address @var{symbol}
33565 Describe where @var{symbol} is stored.
33567 @subsubheading @value{GDBN} Command
33569 The corresponding @value{GDBN} command is @samp{info address}.
33571 @subsubheading Example
33575 @subheading The @code{-symbol-info-file} Command
33576 @findex -symbol-info-file
33578 @subsubheading Synopsis
33584 Show the file for the symbol.
33586 @subsubheading @value{GDBN} Command
33588 There's no equivalent @value{GDBN} command. @code{gdbtk} has
33589 @samp{gdb_find_file}.
33591 @subsubheading Example
33595 @subheading The @code{-symbol-info-function} Command
33596 @findex -symbol-info-function
33598 @subsubheading Synopsis
33601 -symbol-info-function
33604 Show which function the symbol lives in.
33606 @subsubheading @value{GDBN} Command
33608 @samp{gdb_get_function} in @code{gdbtk}.
33610 @subsubheading Example
33614 @subheading The @code{-symbol-info-line} Command
33615 @findex -symbol-info-line
33617 @subsubheading Synopsis
33623 Show the core addresses of the code for a source line.
33625 @subsubheading @value{GDBN} Command
33627 The corresponding @value{GDBN} command is @samp{info line}.
33628 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
33630 @subsubheading Example
33634 @subheading The @code{-symbol-info-symbol} Command
33635 @findex -symbol-info-symbol
33637 @subsubheading Synopsis
33640 -symbol-info-symbol @var{addr}
33643 Describe what symbol is at location @var{addr}.
33645 @subsubheading @value{GDBN} Command
33647 The corresponding @value{GDBN} command is @samp{info symbol}.
33649 @subsubheading Example
33653 @subheading The @code{-symbol-list-functions} Command
33654 @findex -symbol-list-functions
33656 @subsubheading Synopsis
33659 -symbol-list-functions
33662 List the functions in the executable.
33664 @subsubheading @value{GDBN} Command
33666 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
33667 @samp{gdb_search} in @code{gdbtk}.
33669 @subsubheading Example
33674 @subheading The @code{-symbol-list-lines} Command
33675 @findex -symbol-list-lines
33677 @subsubheading Synopsis
33680 -symbol-list-lines @var{filename}
33683 Print the list of lines that contain code and their associated program
33684 addresses for the given source filename. The entries are sorted in
33685 ascending PC order.
33687 @subsubheading @value{GDBN} Command
33689 There is no corresponding @value{GDBN} command.
33691 @subsubheading Example
33694 -symbol-list-lines basics.c
33695 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
33701 @subheading The @code{-symbol-list-types} Command
33702 @findex -symbol-list-types
33704 @subsubheading Synopsis
33710 List all the type names.
33712 @subsubheading @value{GDBN} Command
33714 The corresponding commands are @samp{info types} in @value{GDBN},
33715 @samp{gdb_search} in @code{gdbtk}.
33717 @subsubheading Example
33721 @subheading The @code{-symbol-list-variables} Command
33722 @findex -symbol-list-variables
33724 @subsubheading Synopsis
33727 -symbol-list-variables
33730 List all the global and static variable names.
33732 @subsubheading @value{GDBN} Command
33734 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
33736 @subsubheading Example
33740 @subheading The @code{-symbol-locate} Command
33741 @findex -symbol-locate
33743 @subsubheading Synopsis
33749 @subsubheading @value{GDBN} Command
33751 @samp{gdb_loc} in @code{gdbtk}.
33753 @subsubheading Example
33757 @subheading The @code{-symbol-type} Command
33758 @findex -symbol-type
33760 @subsubheading Synopsis
33763 -symbol-type @var{variable}
33766 Show type of @var{variable}.
33768 @subsubheading @value{GDBN} Command
33770 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33771 @samp{gdb_obj_variable}.
33773 @subsubheading Example
33778 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33779 @node GDB/MI File Commands
33780 @section @sc{gdb/mi} File Commands
33782 This section describes the GDB/MI commands to specify executable file names
33783 and to read in and obtain symbol table information.
33785 @subheading The @code{-file-exec-and-symbols} Command
33786 @findex -file-exec-and-symbols
33788 @subsubheading Synopsis
33791 -file-exec-and-symbols @var{file}
33794 Specify the executable file to be debugged. This file is the one from
33795 which the symbol table is also read. If no file is specified, the
33796 command clears the executable and symbol information. If breakpoints
33797 are set when using this command with no arguments, @value{GDBN} will produce
33798 error messages. Otherwise, no output is produced, except a completion
33801 @subsubheading @value{GDBN} Command
33803 The corresponding @value{GDBN} command is @samp{file}.
33805 @subsubheading Example
33809 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33815 @subheading The @code{-file-exec-file} Command
33816 @findex -file-exec-file
33818 @subsubheading Synopsis
33821 -file-exec-file @var{file}
33824 Specify the executable file to be debugged. Unlike
33825 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33826 from this file. If used without argument, @value{GDBN} clears the information
33827 about the executable file. No output is produced, except a completion
33830 @subsubheading @value{GDBN} Command
33832 The corresponding @value{GDBN} command is @samp{exec-file}.
33834 @subsubheading Example
33838 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33845 @subheading The @code{-file-list-exec-sections} Command
33846 @findex -file-list-exec-sections
33848 @subsubheading Synopsis
33851 -file-list-exec-sections
33854 List the sections of the current executable file.
33856 @subsubheading @value{GDBN} Command
33858 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33859 information as this command. @code{gdbtk} has a corresponding command
33860 @samp{gdb_load_info}.
33862 @subsubheading Example
33867 @subheading The @code{-file-list-exec-source-file} Command
33868 @findex -file-list-exec-source-file
33870 @subsubheading Synopsis
33873 -file-list-exec-source-file
33876 List the line number, the current source file, and the absolute path
33877 to the current source file for the current executable. The macro
33878 information field has a value of @samp{1} or @samp{0} depending on
33879 whether or not the file includes preprocessor macro information.
33881 @subsubheading @value{GDBN} Command
33883 The @value{GDBN} equivalent is @samp{info source}
33885 @subsubheading Example
33889 123-file-list-exec-source-file
33890 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
33895 @subheading The @code{-file-list-exec-source-files} Command
33896 @findex -file-list-exec-source-files
33898 @subsubheading Synopsis
33901 -file-list-exec-source-files
33904 List the source files for the current executable.
33906 It will always output both the filename and fullname (absolute file
33907 name) of a source file.
33909 @subsubheading @value{GDBN} Command
33911 The @value{GDBN} equivalent is @samp{info sources}.
33912 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
33914 @subsubheading Example
33917 -file-list-exec-source-files
33919 @{file=foo.c,fullname=/home/foo.c@},
33920 @{file=/home/bar.c,fullname=/home/bar.c@},
33921 @{file=gdb_could_not_find_fullpath.c@}]
33926 @subheading The @code{-file-list-shared-libraries} Command
33927 @findex -file-list-shared-libraries
33929 @subsubheading Synopsis
33932 -file-list-shared-libraries
33935 List the shared libraries in the program.
33937 @subsubheading @value{GDBN} Command
33939 The corresponding @value{GDBN} command is @samp{info shared}.
33941 @subsubheading Example
33945 @subheading The @code{-file-list-symbol-files} Command
33946 @findex -file-list-symbol-files
33948 @subsubheading Synopsis
33951 -file-list-symbol-files
33956 @subsubheading @value{GDBN} Command
33958 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33960 @subsubheading Example
33965 @subheading The @code{-file-symbol-file} Command
33966 @findex -file-symbol-file
33968 @subsubheading Synopsis
33971 -file-symbol-file @var{file}
33974 Read symbol table info from the specified @var{file} argument. When
33975 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33976 produced, except for a completion notification.
33978 @subsubheading @value{GDBN} Command
33980 The corresponding @value{GDBN} command is @samp{symbol-file}.
33982 @subsubheading Example
33986 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33992 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33993 @node GDB/MI Memory Overlay Commands
33994 @section @sc{gdb/mi} Memory Overlay Commands
33996 The memory overlay commands are not implemented.
33998 @c @subheading -overlay-auto
34000 @c @subheading -overlay-list-mapping-state
34002 @c @subheading -overlay-list-overlays
34004 @c @subheading -overlay-map
34006 @c @subheading -overlay-off
34008 @c @subheading -overlay-on
34010 @c @subheading -overlay-unmap
34012 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34013 @node GDB/MI Signal Handling Commands
34014 @section @sc{gdb/mi} Signal Handling Commands
34016 Signal handling commands are not implemented.
34018 @c @subheading -signal-handle
34020 @c @subheading -signal-list-handle-actions
34022 @c @subheading -signal-list-signal-types
34026 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34027 @node GDB/MI Target Manipulation
34028 @section @sc{gdb/mi} Target Manipulation Commands
34031 @subheading The @code{-target-attach} Command
34032 @findex -target-attach
34034 @subsubheading Synopsis
34037 -target-attach @var{pid} | @var{gid} | @var{file}
34040 Attach to a process @var{pid} or a file @var{file} outside of
34041 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
34042 group, the id previously returned by
34043 @samp{-list-thread-groups --available} must be used.
34045 @subsubheading @value{GDBN} Command
34047 The corresponding @value{GDBN} command is @samp{attach}.
34049 @subsubheading Example
34053 =thread-created,id="1"
34054 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
34060 @subheading The @code{-target-compare-sections} Command
34061 @findex -target-compare-sections
34063 @subsubheading Synopsis
34066 -target-compare-sections [ @var{section} ]
34069 Compare data of section @var{section} on target to the exec file.
34070 Without the argument, all sections are compared.
34072 @subsubheading @value{GDBN} Command
34074 The @value{GDBN} equivalent is @samp{compare-sections}.
34076 @subsubheading Example
34081 @subheading The @code{-target-detach} Command
34082 @findex -target-detach
34084 @subsubheading Synopsis
34087 -target-detach [ @var{pid} | @var{gid} ]
34090 Detach from the remote target which normally resumes its execution.
34091 If either @var{pid} or @var{gid} is specified, detaches from either
34092 the specified process, or specified thread group. There's no output.
34094 @subsubheading @value{GDBN} Command
34096 The corresponding @value{GDBN} command is @samp{detach}.
34098 @subsubheading Example
34108 @subheading The @code{-target-disconnect} Command
34109 @findex -target-disconnect
34111 @subsubheading Synopsis
34117 Disconnect from the remote target. There's no output and the target is
34118 generally not resumed.
34120 @subsubheading @value{GDBN} Command
34122 The corresponding @value{GDBN} command is @samp{disconnect}.
34124 @subsubheading Example
34134 @subheading The @code{-target-download} Command
34135 @findex -target-download
34137 @subsubheading Synopsis
34143 Loads the executable onto the remote target.
34144 It prints out an update message every half second, which includes the fields:
34148 The name of the section.
34150 The size of what has been sent so far for that section.
34152 The size of the section.
34154 The total size of what was sent so far (the current and the previous sections).
34156 The size of the overall executable to download.
34160 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34161 @sc{gdb/mi} Output Syntax}).
34163 In addition, it prints the name and size of the sections, as they are
34164 downloaded. These messages include the following fields:
34168 The name of the section.
34170 The size of the section.
34172 The size of the overall executable to download.
34176 At the end, a summary is printed.
34178 @subsubheading @value{GDBN} Command
34180 The corresponding @value{GDBN} command is @samp{load}.
34182 @subsubheading Example
34184 Note: each status message appears on a single line. Here the messages
34185 have been broken down so that they can fit onto a page.
34190 +download,@{section=".text",section-size="6668",total-size="9880"@}
34191 +download,@{section=".text",section-sent="512",section-size="6668",
34192 total-sent="512",total-size="9880"@}
34193 +download,@{section=".text",section-sent="1024",section-size="6668",
34194 total-sent="1024",total-size="9880"@}
34195 +download,@{section=".text",section-sent="1536",section-size="6668",
34196 total-sent="1536",total-size="9880"@}
34197 +download,@{section=".text",section-sent="2048",section-size="6668",
34198 total-sent="2048",total-size="9880"@}
34199 +download,@{section=".text",section-sent="2560",section-size="6668",
34200 total-sent="2560",total-size="9880"@}
34201 +download,@{section=".text",section-sent="3072",section-size="6668",
34202 total-sent="3072",total-size="9880"@}
34203 +download,@{section=".text",section-sent="3584",section-size="6668",
34204 total-sent="3584",total-size="9880"@}
34205 +download,@{section=".text",section-sent="4096",section-size="6668",
34206 total-sent="4096",total-size="9880"@}
34207 +download,@{section=".text",section-sent="4608",section-size="6668",
34208 total-sent="4608",total-size="9880"@}
34209 +download,@{section=".text",section-sent="5120",section-size="6668",
34210 total-sent="5120",total-size="9880"@}
34211 +download,@{section=".text",section-sent="5632",section-size="6668",
34212 total-sent="5632",total-size="9880"@}
34213 +download,@{section=".text",section-sent="6144",section-size="6668",
34214 total-sent="6144",total-size="9880"@}
34215 +download,@{section=".text",section-sent="6656",section-size="6668",
34216 total-sent="6656",total-size="9880"@}
34217 +download,@{section=".init",section-size="28",total-size="9880"@}
34218 +download,@{section=".fini",section-size="28",total-size="9880"@}
34219 +download,@{section=".data",section-size="3156",total-size="9880"@}
34220 +download,@{section=".data",section-sent="512",section-size="3156",
34221 total-sent="7236",total-size="9880"@}
34222 +download,@{section=".data",section-sent="1024",section-size="3156",
34223 total-sent="7748",total-size="9880"@}
34224 +download,@{section=".data",section-sent="1536",section-size="3156",
34225 total-sent="8260",total-size="9880"@}
34226 +download,@{section=".data",section-sent="2048",section-size="3156",
34227 total-sent="8772",total-size="9880"@}
34228 +download,@{section=".data",section-sent="2560",section-size="3156",
34229 total-sent="9284",total-size="9880"@}
34230 +download,@{section=".data",section-sent="3072",section-size="3156",
34231 total-sent="9796",total-size="9880"@}
34232 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34239 @subheading The @code{-target-exec-status} Command
34240 @findex -target-exec-status
34242 @subsubheading Synopsis
34245 -target-exec-status
34248 Provide information on the state of the target (whether it is running or
34249 not, for instance).
34251 @subsubheading @value{GDBN} Command
34253 There's no equivalent @value{GDBN} command.
34255 @subsubheading Example
34259 @subheading The @code{-target-list-available-targets} Command
34260 @findex -target-list-available-targets
34262 @subsubheading Synopsis
34265 -target-list-available-targets
34268 List the possible targets to connect to.
34270 @subsubheading @value{GDBN} Command
34272 The corresponding @value{GDBN} command is @samp{help target}.
34274 @subsubheading Example
34278 @subheading The @code{-target-list-current-targets} Command
34279 @findex -target-list-current-targets
34281 @subsubheading Synopsis
34284 -target-list-current-targets
34287 Describe the current target.
34289 @subsubheading @value{GDBN} Command
34291 The corresponding information is printed by @samp{info file} (among
34294 @subsubheading Example
34298 @subheading The @code{-target-list-parameters} Command
34299 @findex -target-list-parameters
34301 @subsubheading Synopsis
34304 -target-list-parameters
34310 @subsubheading @value{GDBN} Command
34314 @subsubheading Example
34318 @subheading The @code{-target-select} Command
34319 @findex -target-select
34321 @subsubheading Synopsis
34324 -target-select @var{type} @var{parameters @dots{}}
34327 Connect @value{GDBN} to the remote target. This command takes two args:
34331 The type of target, for instance @samp{remote}, etc.
34332 @item @var{parameters}
34333 Device names, host names and the like. @xref{Target Commands, ,
34334 Commands for Managing Targets}, for more details.
34337 The output is a connection notification, followed by the address at
34338 which the target program is, in the following form:
34341 ^connected,addr="@var{address}",func="@var{function name}",
34342 args=[@var{arg list}]
34345 @subsubheading @value{GDBN} Command
34347 The corresponding @value{GDBN} command is @samp{target}.
34349 @subsubheading Example
34353 -target-select remote /dev/ttya
34354 ^connected,addr="0xfe00a300",func="??",args=[]
34358 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34359 @node GDB/MI File Transfer Commands
34360 @section @sc{gdb/mi} File Transfer Commands
34363 @subheading The @code{-target-file-put} Command
34364 @findex -target-file-put
34366 @subsubheading Synopsis
34369 -target-file-put @var{hostfile} @var{targetfile}
34372 Copy file @var{hostfile} from the host system (the machine running
34373 @value{GDBN}) to @var{targetfile} on the target system.
34375 @subsubheading @value{GDBN} Command
34377 The corresponding @value{GDBN} command is @samp{remote put}.
34379 @subsubheading Example
34383 -target-file-put localfile remotefile
34389 @subheading The @code{-target-file-get} Command
34390 @findex -target-file-get
34392 @subsubheading Synopsis
34395 -target-file-get @var{targetfile} @var{hostfile}
34398 Copy file @var{targetfile} from the target system to @var{hostfile}
34399 on the host system.
34401 @subsubheading @value{GDBN} Command
34403 The corresponding @value{GDBN} command is @samp{remote get}.
34405 @subsubheading Example
34409 -target-file-get remotefile localfile
34415 @subheading The @code{-target-file-delete} Command
34416 @findex -target-file-delete
34418 @subsubheading Synopsis
34421 -target-file-delete @var{targetfile}
34424 Delete @var{targetfile} from the target system.
34426 @subsubheading @value{GDBN} Command
34428 The corresponding @value{GDBN} command is @samp{remote delete}.
34430 @subsubheading Example
34434 -target-file-delete remotefile
34440 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34441 @node GDB/MI Miscellaneous Commands
34442 @section Miscellaneous @sc{gdb/mi} Commands
34444 @c @subheading -gdb-complete
34446 @subheading The @code{-gdb-exit} Command
34449 @subsubheading Synopsis
34455 Exit @value{GDBN} immediately.
34457 @subsubheading @value{GDBN} Command
34459 Approximately corresponds to @samp{quit}.
34461 @subsubheading Example
34471 @subheading The @code{-exec-abort} Command
34472 @findex -exec-abort
34474 @subsubheading Synopsis
34480 Kill the inferior running program.
34482 @subsubheading @value{GDBN} Command
34484 The corresponding @value{GDBN} command is @samp{kill}.
34486 @subsubheading Example
34491 @subheading The @code{-gdb-set} Command
34494 @subsubheading Synopsis
34500 Set an internal @value{GDBN} variable.
34501 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34503 @subsubheading @value{GDBN} Command
34505 The corresponding @value{GDBN} command is @samp{set}.
34507 @subsubheading Example
34517 @subheading The @code{-gdb-show} Command
34520 @subsubheading Synopsis
34526 Show the current value of a @value{GDBN} variable.
34528 @subsubheading @value{GDBN} Command
34530 The corresponding @value{GDBN} command is @samp{show}.
34532 @subsubheading Example
34541 @c @subheading -gdb-source
34544 @subheading The @code{-gdb-version} Command
34545 @findex -gdb-version
34547 @subsubheading Synopsis
34553 Show version information for @value{GDBN}. Used mostly in testing.
34555 @subsubheading @value{GDBN} Command
34557 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34558 default shows this information when you start an interactive session.
34560 @subsubheading Example
34562 @c This example modifies the actual output from GDB to avoid overfull
34568 ~Copyright 2000 Free Software Foundation, Inc.
34569 ~GDB is free software, covered by the GNU General Public License, and
34570 ~you are welcome to change it and/or distribute copies of it under
34571 ~ certain conditions.
34572 ~Type "show copying" to see the conditions.
34573 ~There is absolutely no warranty for GDB. Type "show warranty" for
34575 ~This GDB was configured as
34576 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34581 @subheading The @code{-list-features} Command
34582 @findex -list-features
34584 Returns a list of particular features of the MI protocol that
34585 this version of gdb implements. A feature can be a command,
34586 or a new field in an output of some command, or even an
34587 important bugfix. While a frontend can sometimes detect presence
34588 of a feature at runtime, it is easier to perform detection at debugger
34591 The command returns a list of strings, with each string naming an
34592 available feature. Each returned string is just a name, it does not
34593 have any internal structure. The list of possible feature names
34599 (gdb) -list-features
34600 ^done,result=["feature1","feature2"]
34603 The current list of features is:
34606 @item frozen-varobjs
34607 Indicates support for the @code{-var-set-frozen} command, as well
34608 as possible presense of the @code{frozen} field in the output
34609 of @code{-varobj-create}.
34610 @item pending-breakpoints
34611 Indicates support for the @option{-f} option to the @code{-break-insert}
34614 Indicates Python scripting support, Python-based
34615 pretty-printing commands, and possible presence of the
34616 @samp{display_hint} field in the output of @code{-var-list-children}
34618 Indicates support for the @code{-thread-info} command.
34619 @item data-read-memory-bytes
34620 Indicates support for the @code{-data-read-memory-bytes} and the
34621 @code{-data-write-memory-bytes} commands.
34622 @item breakpoint-notifications
34623 Indicates that changes to breakpoints and breakpoints created via the
34624 CLI will be announced via async records.
34625 @item ada-task-info
34626 Indicates support for the @code{-ada-task-info} command.
34629 @subheading The @code{-list-target-features} Command
34630 @findex -list-target-features
34632 Returns a list of particular features that are supported by the
34633 target. Those features affect the permitted MI commands, but
34634 unlike the features reported by the @code{-list-features} command, the
34635 features depend on which target GDB is using at the moment. Whenever
34636 a target can change, due to commands such as @code{-target-select},
34637 @code{-target-attach} or @code{-exec-run}, the list of target features
34638 may change, and the frontend should obtain it again.
34642 (gdb) -list-target-features
34643 ^done,result=["async"]
34646 The current list of features is:
34650 Indicates that the target is capable of asynchronous command
34651 execution, which means that @value{GDBN} will accept further commands
34652 while the target is running.
34655 Indicates that the target is capable of reverse execution.
34656 @xref{Reverse Execution}, for more information.
34660 @subheading The @code{-list-thread-groups} Command
34661 @findex -list-thread-groups
34663 @subheading Synopsis
34666 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34669 Lists thread groups (@pxref{Thread groups}). When a single thread
34670 group is passed as the argument, lists the children of that group.
34671 When several thread group are passed, lists information about those
34672 thread groups. Without any parameters, lists information about all
34673 top-level thread groups.
34675 Normally, thread groups that are being debugged are reported.
34676 With the @samp{--available} option, @value{GDBN} reports thread groups
34677 available on the target.
34679 The output of this command may have either a @samp{threads} result or
34680 a @samp{groups} result. The @samp{thread} result has a list of tuples
34681 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34682 Information}). The @samp{groups} result has a list of tuples as value,
34683 each tuple describing a thread group. If top-level groups are
34684 requested (that is, no parameter is passed), or when several groups
34685 are passed, the output always has a @samp{groups} result. The format
34686 of the @samp{group} result is described below.
34688 To reduce the number of roundtrips it's possible to list thread groups
34689 together with their children, by passing the @samp{--recurse} option
34690 and the recursion depth. Presently, only recursion depth of 1 is
34691 permitted. If this option is present, then every reported thread group
34692 will also include its children, either as @samp{group} or
34693 @samp{threads} field.
34695 In general, any combination of option and parameters is permitted, with
34696 the following caveats:
34700 When a single thread group is passed, the output will typically
34701 be the @samp{threads} result. Because threads may not contain
34702 anything, the @samp{recurse} option will be ignored.
34705 When the @samp{--available} option is passed, limited information may
34706 be available. In particular, the list of threads of a process might
34707 be inaccessible. Further, specifying specific thread groups might
34708 not give any performance advantage over listing all thread groups.
34709 The frontend should assume that @samp{-list-thread-groups --available}
34710 is always an expensive operation and cache the results.
34714 The @samp{groups} result is a list of tuples, where each tuple may
34715 have the following fields:
34719 Identifier of the thread group. This field is always present.
34720 The identifier is an opaque string; frontends should not try to
34721 convert it to an integer, even though it might look like one.
34724 The type of the thread group. At present, only @samp{process} is a
34728 The target-specific process identifier. This field is only present
34729 for thread groups of type @samp{process} and only if the process exists.
34732 The number of children this thread group has. This field may be
34733 absent for an available thread group.
34736 This field has a list of tuples as value, each tuple describing a
34737 thread. It may be present if the @samp{--recurse} option is
34738 specified, and it's actually possible to obtain the threads.
34741 This field is a list of integers, each identifying a core that one
34742 thread of the group is running on. This field may be absent if
34743 such information is not available.
34746 The name of the executable file that corresponds to this thread group.
34747 The field is only present for thread groups of type @samp{process},
34748 and only if there is a corresponding executable file.
34752 @subheading Example
34756 -list-thread-groups
34757 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34758 -list-thread-groups 17
34759 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34760 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34761 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34762 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34763 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
34764 -list-thread-groups --available
34765 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34766 -list-thread-groups --available --recurse 1
34767 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34768 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34769 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34770 -list-thread-groups --available --recurse 1 17 18
34771 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34772 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34773 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34776 @subheading The @code{-info-os} Command
34779 @subsubheading Synopsis
34782 -info-os [ @var{type} ]
34785 If no argument is supplied, the command returns a table of available
34786 operating-system-specific information types. If one of these types is
34787 supplied as an argument @var{type}, then the command returns a table
34788 of data of that type.
34790 The types of information available depend on the target operating
34793 @subsubheading @value{GDBN} Command
34795 The corresponding @value{GDBN} command is @samp{info os}.
34797 @subsubheading Example
34799 When run on a @sc{gnu}/Linux system, the output will look something
34805 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
34806 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34807 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34808 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34809 body=[item=@{col0="processes",col1="Listing of all processes",
34810 col2="Processes"@},
34811 item=@{col0="procgroups",col1="Listing of all process groups",
34812 col2="Process groups"@},
34813 item=@{col0="threads",col1="Listing of all threads",
34815 item=@{col0="files",col1="Listing of all file descriptors",
34816 col2="File descriptors"@},
34817 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34819 item=@{col0="shm",col1="Listing of all shared-memory regions",
34820 col2="Shared-memory regions"@},
34821 item=@{col0="semaphores",col1="Listing of all semaphores",
34822 col2="Semaphores"@},
34823 item=@{col0="msg",col1="Listing of all message queues",
34824 col2="Message queues"@},
34825 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34826 col2="Kernel modules"@}]@}
34829 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34830 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34831 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34832 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34833 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34834 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34835 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34836 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34838 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34839 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34843 (Note that the MI output here includes a @code{"Title"} column that
34844 does not appear in command-line @code{info os}; this column is useful
34845 for MI clients that want to enumerate the types of data, such as in a
34846 popup menu, but is needless clutter on the command line, and
34847 @code{info os} omits it.)
34849 @subheading The @code{-add-inferior} Command
34850 @findex -add-inferior
34852 @subheading Synopsis
34858 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34859 inferior is not associated with any executable. Such association may
34860 be established with the @samp{-file-exec-and-symbols} command
34861 (@pxref{GDB/MI File Commands}). The command response has a single
34862 field, @samp{inferior}, whose value is the identifier of the
34863 thread group corresponding to the new inferior.
34865 @subheading Example
34870 ^done,inferior="i3"
34873 @subheading The @code{-interpreter-exec} Command
34874 @findex -interpreter-exec
34876 @subheading Synopsis
34879 -interpreter-exec @var{interpreter} @var{command}
34881 @anchor{-interpreter-exec}
34883 Execute the specified @var{command} in the given @var{interpreter}.
34885 @subheading @value{GDBN} Command
34887 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34889 @subheading Example
34893 -interpreter-exec console "break main"
34894 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34895 &"During symbol reading, bad structure-type format.\n"
34896 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34901 @subheading The @code{-inferior-tty-set} Command
34902 @findex -inferior-tty-set
34904 @subheading Synopsis
34907 -inferior-tty-set /dev/pts/1
34910 Set terminal for future runs of the program being debugged.
34912 @subheading @value{GDBN} Command
34914 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34916 @subheading Example
34920 -inferior-tty-set /dev/pts/1
34925 @subheading The @code{-inferior-tty-show} Command
34926 @findex -inferior-tty-show
34928 @subheading Synopsis
34934 Show terminal for future runs of program being debugged.
34936 @subheading @value{GDBN} Command
34938 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34940 @subheading Example
34944 -inferior-tty-set /dev/pts/1
34948 ^done,inferior_tty_terminal="/dev/pts/1"
34952 @subheading The @code{-enable-timings} Command
34953 @findex -enable-timings
34955 @subheading Synopsis
34958 -enable-timings [yes | no]
34961 Toggle the printing of the wallclock, user and system times for an MI
34962 command as a field in its output. This command is to help frontend
34963 developers optimize the performance of their code. No argument is
34964 equivalent to @samp{yes}.
34966 @subheading @value{GDBN} Command
34970 @subheading Example
34978 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34979 addr="0x080484ed",func="main",file="myprog.c",
34980 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34982 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34990 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34991 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34992 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34993 fullname="/home/nickrob/myprog.c",line="73"@}
34998 @chapter @value{GDBN} Annotations
35000 This chapter describes annotations in @value{GDBN}. Annotations were
35001 designed to interface @value{GDBN} to graphical user interfaces or other
35002 similar programs which want to interact with @value{GDBN} at a
35003 relatively high level.
35005 The annotation mechanism has largely been superseded by @sc{gdb/mi}
35009 This is Edition @value{EDITION}, @value{DATE}.
35013 * Annotations Overview:: What annotations are; the general syntax.
35014 * Server Prefix:: Issuing a command without affecting user state.
35015 * Prompting:: Annotations marking @value{GDBN}'s need for input.
35016 * Errors:: Annotations for error messages.
35017 * Invalidation:: Some annotations describe things now invalid.
35018 * Annotations for Running::
35019 Whether the program is running, how it stopped, etc.
35020 * Source Annotations:: Annotations describing source code.
35023 @node Annotations Overview
35024 @section What is an Annotation?
35025 @cindex annotations
35027 Annotations start with a newline character, two @samp{control-z}
35028 characters, and the name of the annotation. If there is no additional
35029 information associated with this annotation, the name of the annotation
35030 is followed immediately by a newline. If there is additional
35031 information, the name of the annotation is followed by a space, the
35032 additional information, and a newline. The additional information
35033 cannot contain newline characters.
35035 Any output not beginning with a newline and two @samp{control-z}
35036 characters denotes literal output from @value{GDBN}. Currently there is
35037 no need for @value{GDBN} to output a newline followed by two
35038 @samp{control-z} characters, but if there was such a need, the
35039 annotations could be extended with an @samp{escape} annotation which
35040 means those three characters as output.
35042 The annotation @var{level}, which is specified using the
35043 @option{--annotate} command line option (@pxref{Mode Options}), controls
35044 how much information @value{GDBN} prints together with its prompt,
35045 values of expressions, source lines, and other types of output. Level 0
35046 is for no annotations, level 1 is for use when @value{GDBN} is run as a
35047 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
35048 for programs that control @value{GDBN}, and level 2 annotations have
35049 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
35050 Interface, annotate, GDB's Obsolete Annotations}).
35053 @kindex set annotate
35054 @item set annotate @var{level}
35055 The @value{GDBN} command @code{set annotate} sets the level of
35056 annotations to the specified @var{level}.
35058 @item show annotate
35059 @kindex show annotate
35060 Show the current annotation level.
35063 This chapter describes level 3 annotations.
35065 A simple example of starting up @value{GDBN} with annotations is:
35068 $ @kbd{gdb --annotate=3}
35070 Copyright 2003 Free Software Foundation, Inc.
35071 GDB is free software, covered by the GNU General Public License,
35072 and you are welcome to change it and/or distribute copies of it
35073 under certain conditions.
35074 Type "show copying" to see the conditions.
35075 There is absolutely no warranty for GDB. Type "show warranty"
35077 This GDB was configured as "i386-pc-linux-gnu"
35088 Here @samp{quit} is input to @value{GDBN}; the rest is output from
35089 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
35090 denotes a @samp{control-z} character) are annotations; the rest is
35091 output from @value{GDBN}.
35093 @node Server Prefix
35094 @section The Server Prefix
35095 @cindex server prefix
35097 If you prefix a command with @samp{server } then it will not affect
35098 the command history, nor will it affect @value{GDBN}'s notion of which
35099 command to repeat if @key{RET} is pressed on a line by itself. This
35100 means that commands can be run behind a user's back by a front-end in
35101 a transparent manner.
35103 The @code{server } prefix does not affect the recording of values into
35104 the value history; to print a value without recording it into the
35105 value history, use the @code{output} command instead of the
35106 @code{print} command.
35108 Using this prefix also disables confirmation requests
35109 (@pxref{confirmation requests}).
35112 @section Annotation for @value{GDBN} Input
35114 @cindex annotations for prompts
35115 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35116 to know when to send output, when the output from a given command is
35119 Different kinds of input each have a different @dfn{input type}. Each
35120 input type has three annotations: a @code{pre-} annotation, which
35121 denotes the beginning of any prompt which is being output, a plain
35122 annotation, which denotes the end of the prompt, and then a @code{post-}
35123 annotation which denotes the end of any echo which may (or may not) be
35124 associated with the input. For example, the @code{prompt} input type
35125 features the following annotations:
35133 The input types are
35136 @findex pre-prompt annotation
35137 @findex prompt annotation
35138 @findex post-prompt annotation
35140 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35142 @findex pre-commands annotation
35143 @findex commands annotation
35144 @findex post-commands annotation
35146 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35147 command. The annotations are repeated for each command which is input.
35149 @findex pre-overload-choice annotation
35150 @findex overload-choice annotation
35151 @findex post-overload-choice annotation
35152 @item overload-choice
35153 When @value{GDBN} wants the user to select between various overloaded functions.
35155 @findex pre-query annotation
35156 @findex query annotation
35157 @findex post-query annotation
35159 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35161 @findex pre-prompt-for-continue annotation
35162 @findex prompt-for-continue annotation
35163 @findex post-prompt-for-continue annotation
35164 @item prompt-for-continue
35165 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35166 expect this to work well; instead use @code{set height 0} to disable
35167 prompting. This is because the counting of lines is buggy in the
35168 presence of annotations.
35173 @cindex annotations for errors, warnings and interrupts
35175 @findex quit annotation
35180 This annotation occurs right before @value{GDBN} responds to an interrupt.
35182 @findex error annotation
35187 This annotation occurs right before @value{GDBN} responds to an error.
35189 Quit and error annotations indicate that any annotations which @value{GDBN} was
35190 in the middle of may end abruptly. For example, if a
35191 @code{value-history-begin} annotation is followed by a @code{error}, one
35192 cannot expect to receive the matching @code{value-history-end}. One
35193 cannot expect not to receive it either, however; an error annotation
35194 does not necessarily mean that @value{GDBN} is immediately returning all the way
35197 @findex error-begin annotation
35198 A quit or error annotation may be preceded by
35204 Any output between that and the quit or error annotation is the error
35207 Warning messages are not yet annotated.
35208 @c If we want to change that, need to fix warning(), type_error(),
35209 @c range_error(), and possibly other places.
35212 @section Invalidation Notices
35214 @cindex annotations for invalidation messages
35215 The following annotations say that certain pieces of state may have
35219 @findex frames-invalid annotation
35220 @item ^Z^Zframes-invalid
35222 The frames (for example, output from the @code{backtrace} command) may
35225 @findex breakpoints-invalid annotation
35226 @item ^Z^Zbreakpoints-invalid
35228 The breakpoints may have changed. For example, the user just added or
35229 deleted a breakpoint.
35232 @node Annotations for Running
35233 @section Running the Program
35234 @cindex annotations for running programs
35236 @findex starting annotation
35237 @findex stopping annotation
35238 When the program starts executing due to a @value{GDBN} command such as
35239 @code{step} or @code{continue},
35245 is output. When the program stops,
35251 is output. Before the @code{stopped} annotation, a variety of
35252 annotations describe how the program stopped.
35255 @findex exited annotation
35256 @item ^Z^Zexited @var{exit-status}
35257 The program exited, and @var{exit-status} is the exit status (zero for
35258 successful exit, otherwise nonzero).
35260 @findex signalled annotation
35261 @findex signal-name annotation
35262 @findex signal-name-end annotation
35263 @findex signal-string annotation
35264 @findex signal-string-end annotation
35265 @item ^Z^Zsignalled
35266 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35267 annotation continues:
35273 ^Z^Zsignal-name-end
35277 ^Z^Zsignal-string-end
35282 where @var{name} is the name of the signal, such as @code{SIGILL} or
35283 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35284 as @code{Illegal Instruction} or @code{Segmentation fault}.
35285 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35286 user's benefit and have no particular format.
35288 @findex signal annotation
35290 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35291 just saying that the program received the signal, not that it was
35292 terminated with it.
35294 @findex breakpoint annotation
35295 @item ^Z^Zbreakpoint @var{number}
35296 The program hit breakpoint number @var{number}.
35298 @findex watchpoint annotation
35299 @item ^Z^Zwatchpoint @var{number}
35300 The program hit watchpoint number @var{number}.
35303 @node Source Annotations
35304 @section Displaying Source
35305 @cindex annotations for source display
35307 @findex source annotation
35308 The following annotation is used instead of displaying source code:
35311 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35314 where @var{filename} is an absolute file name indicating which source
35315 file, @var{line} is the line number within that file (where 1 is the
35316 first line in the file), @var{character} is the character position
35317 within the file (where 0 is the first character in the file) (for most
35318 debug formats this will necessarily point to the beginning of a line),
35319 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35320 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35321 @var{addr} is the address in the target program associated with the
35322 source which is being displayed. @var{addr} is in the form @samp{0x}
35323 followed by one or more lowercase hex digits (note that this does not
35324 depend on the language).
35326 @node JIT Interface
35327 @chapter JIT Compilation Interface
35328 @cindex just-in-time compilation
35329 @cindex JIT compilation interface
35331 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35332 interface. A JIT compiler is a program or library that generates native
35333 executable code at runtime and executes it, usually in order to achieve good
35334 performance while maintaining platform independence.
35336 Programs that use JIT compilation are normally difficult to debug because
35337 portions of their code are generated at runtime, instead of being loaded from
35338 object files, which is where @value{GDBN} normally finds the program's symbols
35339 and debug information. In order to debug programs that use JIT compilation,
35340 @value{GDBN} has an interface that allows the program to register in-memory
35341 symbol files with @value{GDBN} at runtime.
35343 If you are using @value{GDBN} to debug a program that uses this interface, then
35344 it should work transparently so long as you have not stripped the binary. If
35345 you are developing a JIT compiler, then the interface is documented in the rest
35346 of this chapter. At this time, the only known client of this interface is the
35349 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35350 JIT compiler communicates with @value{GDBN} by writing data into a global
35351 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35352 attaches, it reads a linked list of symbol files from the global variable to
35353 find existing code, and puts a breakpoint in the function so that it can find
35354 out about additional code.
35357 * Declarations:: Relevant C struct declarations
35358 * Registering Code:: Steps to register code
35359 * Unregistering Code:: Steps to unregister code
35360 * Custom Debug Info:: Emit debug information in a custom format
35364 @section JIT Declarations
35366 These are the relevant struct declarations that a C program should include to
35367 implement the interface:
35377 struct jit_code_entry
35379 struct jit_code_entry *next_entry;
35380 struct jit_code_entry *prev_entry;
35381 const char *symfile_addr;
35382 uint64_t symfile_size;
35385 struct jit_descriptor
35388 /* This type should be jit_actions_t, but we use uint32_t
35389 to be explicit about the bitwidth. */
35390 uint32_t action_flag;
35391 struct jit_code_entry *relevant_entry;
35392 struct jit_code_entry *first_entry;
35395 /* GDB puts a breakpoint in this function. */
35396 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35398 /* Make sure to specify the version statically, because the
35399 debugger may check the version before we can set it. */
35400 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35403 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35404 modifications to this global data properly, which can easily be done by putting
35405 a global mutex around modifications to these structures.
35407 @node Registering Code
35408 @section Registering Code
35410 To register code with @value{GDBN}, the JIT should follow this protocol:
35414 Generate an object file in memory with symbols and other desired debug
35415 information. The file must include the virtual addresses of the sections.
35418 Create a code entry for the file, which gives the start and size of the symbol
35422 Add it to the linked list in the JIT descriptor.
35425 Point the relevant_entry field of the descriptor at the entry.
35428 Set @code{action_flag} to @code{JIT_REGISTER} and call
35429 @code{__jit_debug_register_code}.
35432 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35433 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35434 new code. However, the linked list must still be maintained in order to allow
35435 @value{GDBN} to attach to a running process and still find the symbol files.
35437 @node Unregistering Code
35438 @section Unregistering Code
35440 If code is freed, then the JIT should use the following protocol:
35444 Remove the code entry corresponding to the code from the linked list.
35447 Point the @code{relevant_entry} field of the descriptor at the code entry.
35450 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35451 @code{__jit_debug_register_code}.
35454 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35455 and the JIT will leak the memory used for the associated symbol files.
35457 @node Custom Debug Info
35458 @section Custom Debug Info
35459 @cindex custom JIT debug info
35460 @cindex JIT debug info reader
35462 Generating debug information in platform-native file formats (like ELF
35463 or COFF) may be an overkill for JIT compilers; especially if all the
35464 debug info is used for is displaying a meaningful backtrace. The
35465 issue can be resolved by having the JIT writers decide on a debug info
35466 format and also provide a reader that parses the debug info generated
35467 by the JIT compiler. This section gives a brief overview on writing
35468 such a parser. More specific details can be found in the source file
35469 @file{gdb/jit-reader.in}, which is also installed as a header at
35470 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35472 The reader is implemented as a shared object (so this functionality is
35473 not available on platforms which don't allow loading shared objects at
35474 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35475 @code{jit-reader-unload} are provided, to be used to load and unload
35476 the readers from a preconfigured directory. Once loaded, the shared
35477 object is used the parse the debug information emitted by the JIT
35481 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35482 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35485 @node Using JIT Debug Info Readers
35486 @subsection Using JIT Debug Info Readers
35487 @kindex jit-reader-load
35488 @kindex jit-reader-unload
35490 Readers can be loaded and unloaded using the @code{jit-reader-load}
35491 and @code{jit-reader-unload} commands.
35494 @item jit-reader-load @var{reader}
35495 Load the JIT reader named @var{reader}. @var{reader} is a shared
35496 object specified as either an absolute or a relative file name. In
35497 the latter case, @value{GDBN} will try to load the reader from a
35498 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35499 system (here @var{libdir} is the system library directory, often
35500 @file{/usr/local/lib}).
35502 Only one reader can be active at a time; trying to load a second
35503 reader when one is already loaded will result in @value{GDBN}
35504 reporting an error. A new JIT reader can be loaded by first unloading
35505 the current one using @code{jit-reader-unload} and then invoking
35506 @code{jit-reader-load}.
35508 @item jit-reader-unload
35509 Unload the currently loaded JIT reader.
35513 @node Writing JIT Debug Info Readers
35514 @subsection Writing JIT Debug Info Readers
35515 @cindex writing JIT debug info readers
35517 As mentioned, a reader is essentially a shared object conforming to a
35518 certain ABI. This ABI is described in @file{jit-reader.h}.
35520 @file{jit-reader.h} defines the structures, macros and functions
35521 required to write a reader. It is installed (along with
35522 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
35523 the system include directory.
35525 Readers need to be released under a GPL compatible license. A reader
35526 can be declared as released under such a license by placing the macro
35527 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
35529 The entry point for readers is the symbol @code{gdb_init_reader},
35530 which is expected to be a function with the prototype
35532 @findex gdb_init_reader
35534 extern struct gdb_reader_funcs *gdb_init_reader (void);
35537 @cindex @code{struct gdb_reader_funcs}
35539 @code{struct gdb_reader_funcs} contains a set of pointers to callback
35540 functions. These functions are executed to read the debug info
35541 generated by the JIT compiler (@code{read}), to unwind stack frames
35542 (@code{unwind}) and to create canonical frame IDs
35543 (@code{get_Frame_id}). It also has a callback that is called when the
35544 reader is being unloaded (@code{destroy}). The struct looks like this
35547 struct gdb_reader_funcs
35549 /* Must be set to GDB_READER_INTERFACE_VERSION. */
35550 int reader_version;
35552 /* For use by the reader. */
35555 gdb_read_debug_info *read;
35556 gdb_unwind_frame *unwind;
35557 gdb_get_frame_id *get_frame_id;
35558 gdb_destroy_reader *destroy;
35562 @cindex @code{struct gdb_symbol_callbacks}
35563 @cindex @code{struct gdb_unwind_callbacks}
35565 The callbacks are provided with another set of callbacks by
35566 @value{GDBN} to do their job. For @code{read}, these callbacks are
35567 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35568 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35569 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35570 files and new symbol tables inside those object files. @code{struct
35571 gdb_unwind_callbacks} has callbacks to read registers off the current
35572 frame and to write out the values of the registers in the previous
35573 frame. Both have a callback (@code{target_read}) to read bytes off the
35574 target's address space.
35576 @node In-Process Agent
35577 @chapter In-Process Agent
35578 @cindex debugging agent
35579 The traditional debugging model is conceptually low-speed, but works fine,
35580 because most bugs can be reproduced in debugging-mode execution. However,
35581 as multi-core or many-core processors are becoming mainstream, and
35582 multi-threaded programs become more and more popular, there should be more
35583 and more bugs that only manifest themselves at normal-mode execution, for
35584 example, thread races, because debugger's interference with the program's
35585 timing may conceal the bugs. On the other hand, in some applications,
35586 it is not feasible for the debugger to interrupt the program's execution
35587 long enough for the developer to learn anything helpful about its behavior.
35588 If the program's correctness depends on its real-time behavior, delays
35589 introduced by a debugger might cause the program to fail, even when the
35590 code itself is correct. It is useful to be able to observe the program's
35591 behavior without interrupting it.
35593 Therefore, traditional debugging model is too intrusive to reproduce
35594 some bugs. In order to reduce the interference with the program, we can
35595 reduce the number of operations performed by debugger. The
35596 @dfn{In-Process Agent}, a shared library, is running within the same
35597 process with inferior, and is able to perform some debugging operations
35598 itself. As a result, debugger is only involved when necessary, and
35599 performance of debugging can be improved accordingly. Note that
35600 interference with program can be reduced but can't be removed completely,
35601 because the in-process agent will still stop or slow down the program.
35603 The in-process agent can interpret and execute Agent Expressions
35604 (@pxref{Agent Expressions}) during performing debugging operations. The
35605 agent expressions can be used for different purposes, such as collecting
35606 data in tracepoints, and condition evaluation in breakpoints.
35608 @anchor{Control Agent}
35609 You can control whether the in-process agent is used as an aid for
35610 debugging with the following commands:
35613 @kindex set agent on
35615 Causes the in-process agent to perform some operations on behalf of the
35616 debugger. Just which operations requested by the user will be done
35617 by the in-process agent depends on the its capabilities. For example,
35618 if you request to evaluate breakpoint conditions in the in-process agent,
35619 and the in-process agent has such capability as well, then breakpoint
35620 conditions will be evaluated in the in-process agent.
35622 @kindex set agent off
35623 @item set agent off
35624 Disables execution of debugging operations by the in-process agent. All
35625 of the operations will be performed by @value{GDBN}.
35629 Display the current setting of execution of debugging operations by
35630 the in-process agent.
35634 * In-Process Agent Protocol::
35637 @node In-Process Agent Protocol
35638 @section In-Process Agent Protocol
35639 @cindex in-process agent protocol
35641 The in-process agent is able to communicate with both @value{GDBN} and
35642 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35643 used for communications between @value{GDBN} or GDBserver and the IPA.
35644 In general, @value{GDBN} or GDBserver sends commands
35645 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35646 in-process agent replies back with the return result of the command, or
35647 some other information. The data sent to in-process agent is composed
35648 of primitive data types, such as 4-byte or 8-byte type, and composite
35649 types, which are called objects (@pxref{IPA Protocol Objects}).
35652 * IPA Protocol Objects::
35653 * IPA Protocol Commands::
35656 @node IPA Protocol Objects
35657 @subsection IPA Protocol Objects
35658 @cindex ipa protocol objects
35660 The commands sent to and results received from agent may contain some
35661 complex data types called @dfn{objects}.
35663 The in-process agent is running on the same machine with @value{GDBN}
35664 or GDBserver, so it doesn't have to handle as much differences between
35665 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35666 However, there are still some differences of two ends in two processes:
35670 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35671 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35673 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35674 GDBserver is compiled with one, and in-process agent is compiled with
35678 Here are the IPA Protocol Objects:
35682 agent expression object. It represents an agent expression
35683 (@pxref{Agent Expressions}).
35684 @anchor{agent expression object}
35686 tracepoint action object. It represents a tracepoint action
35687 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35688 memory, static trace data and to evaluate expression.
35689 @anchor{tracepoint action object}
35691 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35692 @anchor{tracepoint object}
35696 The following table describes important attributes of each IPA protocol
35699 @multitable @columnfractions .30 .20 .50
35700 @headitem Name @tab Size @tab Description
35701 @item @emph{agent expression object} @tab @tab
35702 @item length @tab 4 @tab length of bytes code
35703 @item byte code @tab @var{length} @tab contents of byte code
35704 @item @emph{tracepoint action for collecting memory} @tab @tab
35705 @item 'M' @tab 1 @tab type of tracepoint action
35706 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35707 address of the lowest byte to collect, otherwise @var{addr} is the offset
35708 of @var{basereg} for memory collecting.
35709 @item len @tab 8 @tab length of memory for collecting
35710 @item basereg @tab 4 @tab the register number containing the starting
35711 memory address for collecting.
35712 @item @emph{tracepoint action for collecting registers} @tab @tab
35713 @item 'R' @tab 1 @tab type of tracepoint action
35714 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35715 @item 'L' @tab 1 @tab type of tracepoint action
35716 @item @emph{tracepoint action for expression evaluation} @tab @tab
35717 @item 'X' @tab 1 @tab type of tracepoint action
35718 @item agent expression @tab length of @tab @ref{agent expression object}
35719 @item @emph{tracepoint object} @tab @tab
35720 @item number @tab 4 @tab number of tracepoint
35721 @item address @tab 8 @tab address of tracepoint inserted on
35722 @item type @tab 4 @tab type of tracepoint
35723 @item enabled @tab 1 @tab enable or disable of tracepoint
35724 @item step_count @tab 8 @tab step
35725 @item pass_count @tab 8 @tab pass
35726 @item numactions @tab 4 @tab number of tracepoint actions
35727 @item hit count @tab 8 @tab hit count
35728 @item trace frame usage @tab 8 @tab trace frame usage
35729 @item compiled_cond @tab 8 @tab compiled condition
35730 @item orig_size @tab 8 @tab orig size
35731 @item condition @tab 4 if condition is NULL otherwise length of
35732 @ref{agent expression object}
35733 @tab zero if condition is NULL, otherwise is
35734 @ref{agent expression object}
35735 @item actions @tab variable
35736 @tab numactions number of @ref{tracepoint action object}
35739 @node IPA Protocol Commands
35740 @subsection IPA Protocol Commands
35741 @cindex ipa protocol commands
35743 The spaces in each command are delimiters to ease reading this commands
35744 specification. They don't exist in real commands.
35748 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35749 Installs a new fast tracepoint described by @var{tracepoint_object}
35750 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
35751 head of @dfn{jumppad}, which is used to jump to data collection routine
35756 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35757 @var{target_address} is address of tracepoint in the inferior.
35758 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35759 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35760 @var{fjump} contains a sequence of instructions jump to jumppad entry.
35761 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35768 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35769 is about to kill inferiors.
35777 @item probe_marker_at:@var{address}
35778 Asks in-process agent to probe the marker at @var{address}.
35785 @item unprobe_marker_at:@var{address}
35786 Asks in-process agent to unprobe the marker at @var{address}.
35790 @chapter Reporting Bugs in @value{GDBN}
35791 @cindex bugs in @value{GDBN}
35792 @cindex reporting bugs in @value{GDBN}
35794 Your bug reports play an essential role in making @value{GDBN} reliable.
35796 Reporting a bug may help you by bringing a solution to your problem, or it
35797 may not. But in any case the principal function of a bug report is to help
35798 the entire community by making the next version of @value{GDBN} work better. Bug
35799 reports are your contribution to the maintenance of @value{GDBN}.
35801 In order for a bug report to serve its purpose, you must include the
35802 information that enables us to fix the bug.
35805 * Bug Criteria:: Have you found a bug?
35806 * Bug Reporting:: How to report bugs
35810 @section Have You Found a Bug?
35811 @cindex bug criteria
35813 If you are not sure whether you have found a bug, here are some guidelines:
35816 @cindex fatal signal
35817 @cindex debugger crash
35818 @cindex crash of debugger
35820 If the debugger gets a fatal signal, for any input whatever, that is a
35821 @value{GDBN} bug. Reliable debuggers never crash.
35823 @cindex error on valid input
35825 If @value{GDBN} produces an error message for valid input, that is a
35826 bug. (Note that if you're cross debugging, the problem may also be
35827 somewhere in the connection to the target.)
35829 @cindex invalid input
35831 If @value{GDBN} does not produce an error message for invalid input,
35832 that is a bug. However, you should note that your idea of
35833 ``invalid input'' might be our idea of ``an extension'' or ``support
35834 for traditional practice''.
35837 If you are an experienced user of debugging tools, your suggestions
35838 for improvement of @value{GDBN} are welcome in any case.
35841 @node Bug Reporting
35842 @section How to Report Bugs
35843 @cindex bug reports
35844 @cindex @value{GDBN} bugs, reporting
35846 A number of companies and individuals offer support for @sc{gnu} products.
35847 If you obtained @value{GDBN} from a support organization, we recommend you
35848 contact that organization first.
35850 You can find contact information for many support companies and
35851 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35853 @c should add a web page ref...
35856 @ifset BUGURL_DEFAULT
35857 In any event, we also recommend that you submit bug reports for
35858 @value{GDBN}. The preferred method is to submit them directly using
35859 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35860 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35863 @strong{Do not send bug reports to @samp{info-gdb}, or to
35864 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35865 not want to receive bug reports. Those that do have arranged to receive
35868 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35869 serves as a repeater. The mailing list and the newsgroup carry exactly
35870 the same messages. Often people think of posting bug reports to the
35871 newsgroup instead of mailing them. This appears to work, but it has one
35872 problem which can be crucial: a newsgroup posting often lacks a mail
35873 path back to the sender. Thus, if we need to ask for more information,
35874 we may be unable to reach you. For this reason, it is better to send
35875 bug reports to the mailing list.
35877 @ifclear BUGURL_DEFAULT
35878 In any event, we also recommend that you submit bug reports for
35879 @value{GDBN} to @value{BUGURL}.
35883 The fundamental principle of reporting bugs usefully is this:
35884 @strong{report all the facts}. If you are not sure whether to state a
35885 fact or leave it out, state it!
35887 Often people omit facts because they think they know what causes the
35888 problem and assume that some details do not matter. Thus, you might
35889 assume that the name of the variable you use in an example does not matter.
35890 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35891 stray memory reference which happens to fetch from the location where that
35892 name is stored in memory; perhaps, if the name were different, the contents
35893 of that location would fool the debugger into doing the right thing despite
35894 the bug. Play it safe and give a specific, complete example. That is the
35895 easiest thing for you to do, and the most helpful.
35897 Keep in mind that the purpose of a bug report is to enable us to fix the
35898 bug. It may be that the bug has been reported previously, but neither
35899 you nor we can know that unless your bug report is complete and
35902 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35903 bell?'' Those bug reports are useless, and we urge everyone to
35904 @emph{refuse to respond to them} except to chide the sender to report
35907 To enable us to fix the bug, you should include all these things:
35911 The version of @value{GDBN}. @value{GDBN} announces it if you start
35912 with no arguments; you can also print it at any time using @code{show
35915 Without this, we will not know whether there is any point in looking for
35916 the bug in the current version of @value{GDBN}.
35919 The type of machine you are using, and the operating system name and
35923 The details of the @value{GDBN} build-time configuration.
35924 @value{GDBN} shows these details if you invoke it with the
35925 @option{--configuration} command-line option, or if you type
35926 @code{show configuration} at @value{GDBN}'s prompt.
35929 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35930 ``@value{GCC}--2.8.1''.
35933 What compiler (and its version) was used to compile the program you are
35934 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35935 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35936 to get this information; for other compilers, see the documentation for
35940 The command arguments you gave the compiler to compile your example and
35941 observe the bug. For example, did you use @samp{-O}? To guarantee
35942 you will not omit something important, list them all. A copy of the
35943 Makefile (or the output from make) is sufficient.
35945 If we were to try to guess the arguments, we would probably guess wrong
35946 and then we might not encounter the bug.
35949 A complete input script, and all necessary source files, that will
35953 A description of what behavior you observe that you believe is
35954 incorrect. For example, ``It gets a fatal signal.''
35956 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35957 will certainly notice it. But if the bug is incorrect output, we might
35958 not notice unless it is glaringly wrong. You might as well not give us
35959 a chance to make a mistake.
35961 Even if the problem you experience is a fatal signal, you should still
35962 say so explicitly. Suppose something strange is going on, such as, your
35963 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35964 the C library on your system. (This has happened!) Your copy might
35965 crash and ours would not. If you told us to expect a crash, then when
35966 ours fails to crash, we would know that the bug was not happening for
35967 us. If you had not told us to expect a crash, then we would not be able
35968 to draw any conclusion from our observations.
35971 @cindex recording a session script
35972 To collect all this information, you can use a session recording program
35973 such as @command{script}, which is available on many Unix systems.
35974 Just run your @value{GDBN} session inside @command{script} and then
35975 include the @file{typescript} file with your bug report.
35977 Another way to record a @value{GDBN} session is to run @value{GDBN}
35978 inside Emacs and then save the entire buffer to a file.
35981 If you wish to suggest changes to the @value{GDBN} source, send us context
35982 diffs. If you even discuss something in the @value{GDBN} source, refer to
35983 it by context, not by line number.
35985 The line numbers in our development sources will not match those in your
35986 sources. Your line numbers would convey no useful information to us.
35990 Here are some things that are not necessary:
35994 A description of the envelope of the bug.
35996 Often people who encounter a bug spend a lot of time investigating
35997 which changes to the input file will make the bug go away and which
35998 changes will not affect it.
36000 This is often time consuming and not very useful, because the way we
36001 will find the bug is by running a single example under the debugger
36002 with breakpoints, not by pure deduction from a series of examples.
36003 We recommend that you save your time for something else.
36005 Of course, if you can find a simpler example to report @emph{instead}
36006 of the original one, that is a convenience for us. Errors in the
36007 output will be easier to spot, running under the debugger will take
36008 less time, and so on.
36010 However, simplification is not vital; if you do not want to do this,
36011 report the bug anyway and send us the entire test case you used.
36014 A patch for the bug.
36016 A patch for the bug does help us if it is a good one. But do not omit
36017 the necessary information, such as the test case, on the assumption that
36018 a patch is all we need. We might see problems with your patch and decide
36019 to fix the problem another way, or we might not understand it at all.
36021 Sometimes with a program as complicated as @value{GDBN} it is very hard to
36022 construct an example that will make the program follow a certain path
36023 through the code. If you do not send us the example, we will not be able
36024 to construct one, so we will not be able to verify that the bug is fixed.
36026 And if we cannot understand what bug you are trying to fix, or why your
36027 patch should be an improvement, we will not install it. A test case will
36028 help us to understand.
36031 A guess about what the bug is or what it depends on.
36033 Such guesses are usually wrong. Even we cannot guess right about such
36034 things without first using the debugger to find the facts.
36037 @c The readline documentation is distributed with the readline code
36038 @c and consists of the two following files:
36041 @c Use -I with makeinfo to point to the appropriate directory,
36042 @c environment var TEXINPUTS with TeX.
36043 @ifclear SYSTEM_READLINE
36044 @include rluser.texi
36045 @include hsuser.texi
36049 @appendix In Memoriam
36051 The @value{GDBN} project mourns the loss of the following long-time
36056 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
36057 to Free Software in general. Outside of @value{GDBN}, he was known in
36058 the Amiga world for his series of Fish Disks, and the GeekGadget project.
36060 @item Michael Snyder
36061 Michael was one of the Global Maintainers of the @value{GDBN} project,
36062 with contributions recorded as early as 1996, until 2011. In addition
36063 to his day to day participation, he was a large driving force behind
36064 adding Reverse Debugging to @value{GDBN}.
36067 Beyond their technical contributions to the project, they were also
36068 enjoyable members of the Free Software Community. We will miss them.
36070 @node Formatting Documentation
36071 @appendix Formatting Documentation
36073 @cindex @value{GDBN} reference card
36074 @cindex reference card
36075 The @value{GDBN} 4 release includes an already-formatted reference card, ready
36076 for printing with PostScript or Ghostscript, in the @file{gdb}
36077 subdirectory of the main source directory@footnote{In
36078 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
36079 release.}. If you can use PostScript or Ghostscript with your printer,
36080 you can print the reference card immediately with @file{refcard.ps}.
36082 The release also includes the source for the reference card. You
36083 can format it, using @TeX{}, by typing:
36089 The @value{GDBN} reference card is designed to print in @dfn{landscape}
36090 mode on US ``letter'' size paper;
36091 that is, on a sheet 11 inches wide by 8.5 inches
36092 high. You will need to specify this form of printing as an option to
36093 your @sc{dvi} output program.
36095 @cindex documentation
36097 All the documentation for @value{GDBN} comes as part of the machine-readable
36098 distribution. The documentation is written in Texinfo format, which is
36099 a documentation system that uses a single source file to produce both
36100 on-line information and a printed manual. You can use one of the Info
36101 formatting commands to create the on-line version of the documentation
36102 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36104 @value{GDBN} includes an already formatted copy of the on-line Info
36105 version of this manual in the @file{gdb} subdirectory. The main Info
36106 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36107 subordinate files matching @samp{gdb.info*} in the same directory. If
36108 necessary, you can print out these files, or read them with any editor;
36109 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36110 Emacs or the standalone @code{info} program, available as part of the
36111 @sc{gnu} Texinfo distribution.
36113 If you want to format these Info files yourself, you need one of the
36114 Info formatting programs, such as @code{texinfo-format-buffer} or
36117 If you have @code{makeinfo} installed, and are in the top level
36118 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36119 version @value{GDBVN}), you can make the Info file by typing:
36126 If you want to typeset and print copies of this manual, you need @TeX{},
36127 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36128 Texinfo definitions file.
36130 @TeX{} is a typesetting program; it does not print files directly, but
36131 produces output files called @sc{dvi} files. To print a typeset
36132 document, you need a program to print @sc{dvi} files. If your system
36133 has @TeX{} installed, chances are it has such a program. The precise
36134 command to use depends on your system; @kbd{lpr -d} is common; another
36135 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36136 require a file name without any extension or a @samp{.dvi} extension.
36138 @TeX{} also requires a macro definitions file called
36139 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36140 written in Texinfo format. On its own, @TeX{} cannot either read or
36141 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36142 and is located in the @file{gdb-@var{version-number}/texinfo}
36145 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36146 typeset and print this manual. First switch to the @file{gdb}
36147 subdirectory of the main source directory (for example, to
36148 @file{gdb-@value{GDBVN}/gdb}) and type:
36154 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36156 @node Installing GDB
36157 @appendix Installing @value{GDBN}
36158 @cindex installation
36161 * Requirements:: Requirements for building @value{GDBN}
36162 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36163 * Separate Objdir:: Compiling @value{GDBN} in another directory
36164 * Config Names:: Specifying names for hosts and targets
36165 * Configure Options:: Summary of options for configure
36166 * System-wide configuration:: Having a system-wide init file
36170 @section Requirements for Building @value{GDBN}
36171 @cindex building @value{GDBN}, requirements for
36173 Building @value{GDBN} requires various tools and packages to be available.
36174 Other packages will be used only if they are found.
36176 @heading Tools/Packages Necessary for Building @value{GDBN}
36178 @item ISO C90 compiler
36179 @value{GDBN} is written in ISO C90. It should be buildable with any
36180 working C90 compiler, e.g.@: GCC.
36184 @heading Tools/Packages Optional for Building @value{GDBN}
36188 @value{GDBN} can use the Expat XML parsing library. This library may be
36189 included with your operating system distribution; if it is not, you
36190 can get the latest version from @url{http://expat.sourceforge.net}.
36191 The @file{configure} script will search for this library in several
36192 standard locations; if it is installed in an unusual path, you can
36193 use the @option{--with-libexpat-prefix} option to specify its location.
36199 Remote protocol memory maps (@pxref{Memory Map Format})
36201 Target descriptions (@pxref{Target Descriptions})
36203 Remote shared library lists (@xref{Library List Format},
36204 or alternatively @pxref{Library List Format for SVR4 Targets})
36206 MS-Windows shared libraries (@pxref{Shared Libraries})
36208 Traceframe info (@pxref{Traceframe Info Format})
36210 Branch trace (@pxref{Branch Trace Format})
36214 @cindex compressed debug sections
36215 @value{GDBN} will use the @samp{zlib} library, if available, to read
36216 compressed debug sections. Some linkers, such as GNU gold, are capable
36217 of producing binaries with compressed debug sections. If @value{GDBN}
36218 is compiled with @samp{zlib}, it will be able to read the debug
36219 information in such binaries.
36221 The @samp{zlib} library is likely included with your operating system
36222 distribution; if it is not, you can get the latest version from
36223 @url{http://zlib.net}.
36226 @value{GDBN}'s features related to character sets (@pxref{Character
36227 Sets}) require a functioning @code{iconv} implementation. If you are
36228 on a GNU system, then this is provided by the GNU C Library. Some
36229 other systems also provide a working @code{iconv}.
36231 If @value{GDBN} is using the @code{iconv} program which is installed
36232 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36233 This is done with @option{--with-iconv-bin} which specifies the
36234 directory that contains the @code{iconv} program.
36236 On systems without @code{iconv}, you can install GNU Libiconv. If you
36237 have previously installed Libiconv, you can use the
36238 @option{--with-libiconv-prefix} option to configure.
36240 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36241 arrange to build Libiconv if a directory named @file{libiconv} appears
36242 in the top-most source directory. If Libiconv is built this way, and
36243 if the operating system does not provide a suitable @code{iconv}
36244 implementation, then the just-built library will automatically be used
36245 by @value{GDBN}. One easy way to set this up is to download GNU
36246 Libiconv, unpack it, and then rename the directory holding the
36247 Libiconv source code to @samp{libiconv}.
36250 @node Running Configure
36251 @section Invoking the @value{GDBN} @file{configure} Script
36252 @cindex configuring @value{GDBN}
36253 @value{GDBN} comes with a @file{configure} script that automates the process
36254 of preparing @value{GDBN} for installation; you can then use @code{make} to
36255 build the @code{gdb} program.
36257 @c irrelevant in info file; it's as current as the code it lives with.
36258 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36259 look at the @file{README} file in the sources; we may have improved the
36260 installation procedures since publishing this manual.}
36263 The @value{GDBN} distribution includes all the source code you need for
36264 @value{GDBN} in a single directory, whose name is usually composed by
36265 appending the version number to @samp{gdb}.
36267 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36268 @file{gdb-@value{GDBVN}} directory. That directory contains:
36271 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36272 script for configuring @value{GDBN} and all its supporting libraries
36274 @item gdb-@value{GDBVN}/gdb
36275 the source specific to @value{GDBN} itself
36277 @item gdb-@value{GDBVN}/bfd
36278 source for the Binary File Descriptor library
36280 @item gdb-@value{GDBVN}/include
36281 @sc{gnu} include files
36283 @item gdb-@value{GDBVN}/libiberty
36284 source for the @samp{-liberty} free software library
36286 @item gdb-@value{GDBVN}/opcodes
36287 source for the library of opcode tables and disassemblers
36289 @item gdb-@value{GDBVN}/readline
36290 source for the @sc{gnu} command-line interface
36292 @item gdb-@value{GDBVN}/glob
36293 source for the @sc{gnu} filename pattern-matching subroutine
36295 @item gdb-@value{GDBVN}/mmalloc
36296 source for the @sc{gnu} memory-mapped malloc package
36299 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36300 from the @file{gdb-@var{version-number}} source directory, which in
36301 this example is the @file{gdb-@value{GDBVN}} directory.
36303 First switch to the @file{gdb-@var{version-number}} source directory
36304 if you are not already in it; then run @file{configure}. Pass the
36305 identifier for the platform on which @value{GDBN} will run as an
36311 cd gdb-@value{GDBVN}
36312 ./configure @var{host}
36317 where @var{host} is an identifier such as @samp{sun4} or
36318 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
36319 (You can often leave off @var{host}; @file{configure} tries to guess the
36320 correct value by examining your system.)
36322 Running @samp{configure @var{host}} and then running @code{make} builds the
36323 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
36324 libraries, then @code{gdb} itself. The configured source files, and the
36325 binaries, are left in the corresponding source directories.
36328 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36329 system does not recognize this automatically when you run a different
36330 shell, you may need to run @code{sh} on it explicitly:
36333 sh configure @var{host}
36336 If you run @file{configure} from a directory that contains source
36337 directories for multiple libraries or programs, such as the
36338 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
36340 creates configuration files for every directory level underneath (unless
36341 you tell it not to, with the @samp{--norecursion} option).
36343 You should run the @file{configure} script from the top directory in the
36344 source tree, the @file{gdb-@var{version-number}} directory. If you run
36345 @file{configure} from one of the subdirectories, you will configure only
36346 that subdirectory. That is usually not what you want. In particular,
36347 if you run the first @file{configure} from the @file{gdb} subdirectory
36348 of the @file{gdb-@var{version-number}} directory, you will omit the
36349 configuration of @file{bfd}, @file{readline}, and other sibling
36350 directories of the @file{gdb} subdirectory. This leads to build errors
36351 about missing include files such as @file{bfd/bfd.h}.
36353 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
36354 However, you should make sure that the shell on your path (named by
36355 the @samp{SHELL} environment variable) is publicly readable. Remember
36356 that @value{GDBN} uses the shell to start your program---some systems refuse to
36357 let @value{GDBN} debug child processes whose programs are not readable.
36359 @node Separate Objdir
36360 @section Compiling @value{GDBN} in Another Directory
36362 If you want to run @value{GDBN} versions for several host or target machines,
36363 you need a different @code{gdb} compiled for each combination of
36364 host and target. @file{configure} is designed to make this easy by
36365 allowing you to generate each configuration in a separate subdirectory,
36366 rather than in the source directory. If your @code{make} program
36367 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36368 @code{make} in each of these directories builds the @code{gdb}
36369 program specified there.
36371 To build @code{gdb} in a separate directory, run @file{configure}
36372 with the @samp{--srcdir} option to specify where to find the source.
36373 (You also need to specify a path to find @file{configure}
36374 itself from your working directory. If the path to @file{configure}
36375 would be the same as the argument to @samp{--srcdir}, you can leave out
36376 the @samp{--srcdir} option; it is assumed.)
36378 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36379 separate directory for a Sun 4 like this:
36383 cd gdb-@value{GDBVN}
36386 ../gdb-@value{GDBVN}/configure sun4
36391 When @file{configure} builds a configuration using a remote source
36392 directory, it creates a tree for the binaries with the same structure
36393 (and using the same names) as the tree under the source directory. In
36394 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36395 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36396 @file{gdb-sun4/gdb}.
36398 Make sure that your path to the @file{configure} script has just one
36399 instance of @file{gdb} in it. If your path to @file{configure} looks
36400 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36401 one subdirectory of @value{GDBN}, not the whole package. This leads to
36402 build errors about missing include files such as @file{bfd/bfd.h}.
36404 One popular reason to build several @value{GDBN} configurations in separate
36405 directories is to configure @value{GDBN} for cross-compiling (where
36406 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36407 programs that run on another machine---the @dfn{target}).
36408 You specify a cross-debugging target by
36409 giving the @samp{--target=@var{target}} option to @file{configure}.
36411 When you run @code{make} to build a program or library, you must run
36412 it in a configured directory---whatever directory you were in when you
36413 called @file{configure} (or one of its subdirectories).
36415 The @code{Makefile} that @file{configure} generates in each source
36416 directory also runs recursively. If you type @code{make} in a source
36417 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36418 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36419 will build all the required libraries, and then build GDB.
36421 When you have multiple hosts or targets configured in separate
36422 directories, you can run @code{make} on them in parallel (for example,
36423 if they are NFS-mounted on each of the hosts); they will not interfere
36427 @section Specifying Names for Hosts and Targets
36429 The specifications used for hosts and targets in the @file{configure}
36430 script are based on a three-part naming scheme, but some short predefined
36431 aliases are also supported. The full naming scheme encodes three pieces
36432 of information in the following pattern:
36435 @var{architecture}-@var{vendor}-@var{os}
36438 For example, you can use the alias @code{sun4} as a @var{host} argument,
36439 or as the value for @var{target} in a @code{--target=@var{target}}
36440 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36442 The @file{configure} script accompanying @value{GDBN} does not provide
36443 any query facility to list all supported host and target names or
36444 aliases. @file{configure} calls the Bourne shell script
36445 @code{config.sub} to map abbreviations to full names; you can read the
36446 script, if you wish, or you can use it to test your guesses on
36447 abbreviations---for example:
36450 % sh config.sub i386-linux
36452 % sh config.sub alpha-linux
36453 alpha-unknown-linux-gnu
36454 % sh config.sub hp9k700
36456 % sh config.sub sun4
36457 sparc-sun-sunos4.1.1
36458 % sh config.sub sun3
36459 m68k-sun-sunos4.1.1
36460 % sh config.sub i986v
36461 Invalid configuration `i986v': machine `i986v' not recognized
36465 @code{config.sub} is also distributed in the @value{GDBN} source
36466 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36468 @node Configure Options
36469 @section @file{configure} Options
36471 Here is a summary of the @file{configure} options and arguments that
36472 are most often useful for building @value{GDBN}. @file{configure} also has
36473 several other options not listed here. @inforef{What Configure
36474 Does,,configure.info}, for a full explanation of @file{configure}.
36477 configure @r{[}--help@r{]}
36478 @r{[}--prefix=@var{dir}@r{]}
36479 @r{[}--exec-prefix=@var{dir}@r{]}
36480 @r{[}--srcdir=@var{dirname}@r{]}
36481 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
36482 @r{[}--target=@var{target}@r{]}
36487 You may introduce options with a single @samp{-} rather than
36488 @samp{--} if you prefer; but you may abbreviate option names if you use
36493 Display a quick summary of how to invoke @file{configure}.
36495 @item --prefix=@var{dir}
36496 Configure the source to install programs and files under directory
36499 @item --exec-prefix=@var{dir}
36500 Configure the source to install programs under directory
36503 @c avoid splitting the warning from the explanation:
36505 @item --srcdir=@var{dirname}
36506 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
36507 @code{make} that implements the @code{VPATH} feature.}@*
36508 Use this option to make configurations in directories separate from the
36509 @value{GDBN} source directories. Among other things, you can use this to
36510 build (or maintain) several configurations simultaneously, in separate
36511 directories. @file{configure} writes configuration-specific files in
36512 the current directory, but arranges for them to use the source in the
36513 directory @var{dirname}. @file{configure} creates directories under
36514 the working directory in parallel to the source directories below
36517 @item --norecursion
36518 Configure only the directory level where @file{configure} is executed; do not
36519 propagate configuration to subdirectories.
36521 @item --target=@var{target}
36522 Configure @value{GDBN} for cross-debugging programs running on the specified
36523 @var{target}. Without this option, @value{GDBN} is configured to debug
36524 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
36526 There is no convenient way to generate a list of all available targets.
36528 @item @var{host} @dots{}
36529 Configure @value{GDBN} to run on the specified @var{host}.
36531 There is no convenient way to generate a list of all available hosts.
36534 There are many other options available as well, but they are generally
36535 needed for special purposes only.
36537 @node System-wide configuration
36538 @section System-wide configuration and settings
36539 @cindex system-wide init file
36541 @value{GDBN} can be configured to have a system-wide init file;
36542 this file will be read and executed at startup (@pxref{Startup, , What
36543 @value{GDBN} does during startup}).
36545 Here is the corresponding configure option:
36548 @item --with-system-gdbinit=@var{file}
36549 Specify that the default location of the system-wide init file is
36553 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36554 it may be subject to relocation. Two possible cases:
36558 If the default location of this init file contains @file{$prefix},
36559 it will be subject to relocation. Suppose that the configure options
36560 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36561 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36562 init file is looked for as @file{$install/etc/gdbinit} instead of
36563 @file{$prefix/etc/gdbinit}.
36566 By contrast, if the default location does not contain the prefix,
36567 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36568 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36569 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36570 wherever @value{GDBN} is installed.
36573 If the configured location of the system-wide init file (as given by the
36574 @option{--with-system-gdbinit} option at configure time) is in the
36575 data-directory (as specified by @option{--with-gdb-datadir} at configure
36576 time) or in one of its subdirectories, then @value{GDBN} will look for the
36577 system-wide init file in the directory specified by the
36578 @option{--data-directory} command-line option.
36579 Note that the system-wide init file is only read once, during @value{GDBN}
36580 initialization. If the data-directory is changed after @value{GDBN} has
36581 started with the @code{set data-directory} command, the file will not be
36585 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36588 @node System-wide Configuration Scripts
36589 @subsection Installed System-wide Configuration Scripts
36590 @cindex system-wide configuration scripts
36592 The @file{system-gdbinit} directory, located inside the data-directory
36593 (as specified by @option{--with-gdb-datadir} at configure time) contains
36594 a number of scripts which can be used as system-wide init files. To
36595 automatically source those scripts at startup, @value{GDBN} should be
36596 configured with @option{--with-system-gdbinit}. Otherwise, any user
36597 should be able to source them by hand as needed.
36599 The following scripts are currently available:
36602 @item @file{elinos.py}
36604 @cindex ELinOS system-wide configuration script
36605 This script is useful when debugging a program on an ELinOS target.
36606 It takes advantage of the environment variables defined in a standard
36607 ELinOS environment in order to determine the location of the system
36608 shared libraries, and then sets the @samp{solib-absolute-prefix}
36609 and @samp{solib-search-path} variables appropriately.
36611 @item @file{wrs-linux.py}
36612 @pindex wrs-linux.py
36613 @cindex Wind River Linux system-wide configuration script
36614 This script is useful when debugging a program on a target running
36615 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36616 the host-side sysroot used by the target system.
36620 @node Maintenance Commands
36621 @appendix Maintenance Commands
36622 @cindex maintenance commands
36623 @cindex internal commands
36625 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36626 includes a number of commands intended for @value{GDBN} developers,
36627 that are not documented elsewhere in this manual. These commands are
36628 provided here for reference. (For commands that turn on debugging
36629 messages, see @ref{Debugging Output}.)
36632 @kindex maint agent
36633 @kindex maint agent-eval
36634 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36635 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36636 Translate the given @var{expression} into remote agent bytecodes.
36637 This command is useful for debugging the Agent Expression mechanism
36638 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36639 expression useful for data collection, such as by tracepoints, while
36640 @samp{maint agent-eval} produces an expression that evaluates directly
36641 to a result. For instance, a collection expression for @code{globa +
36642 globb} will include bytecodes to record four bytes of memory at each
36643 of the addresses of @code{globa} and @code{globb}, while discarding
36644 the result of the addition, while an evaluation expression will do the
36645 addition and return the sum.
36646 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36647 If not, generate remote agent bytecode for current frame PC address.
36649 @kindex maint agent-printf
36650 @item maint agent-printf @var{format},@var{expr},...
36651 Translate the given format string and list of argument expressions
36652 into remote agent bytecodes and display them as a disassembled list.
36653 This command is useful for debugging the agent version of dynamic
36654 printf (@pxref{Dynamic Printf}).
36656 @kindex maint info breakpoints
36657 @item @anchor{maint info breakpoints}maint info breakpoints
36658 Using the same format as @samp{info breakpoints}, display both the
36659 breakpoints you've set explicitly, and those @value{GDBN} is using for
36660 internal purposes. Internal breakpoints are shown with negative
36661 breakpoint numbers. The type column identifies what kind of breakpoint
36666 Normal, explicitly set breakpoint.
36669 Normal, explicitly set watchpoint.
36672 Internal breakpoint, used to handle correctly stepping through
36673 @code{longjmp} calls.
36675 @item longjmp resume
36676 Internal breakpoint at the target of a @code{longjmp}.
36679 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36682 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36685 Shared library events.
36689 @kindex maint info bfds
36690 @item maint info bfds
36691 This prints information about each @code{bfd} object that is known to
36692 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
36694 @kindex set displaced-stepping
36695 @kindex show displaced-stepping
36696 @cindex displaced stepping support
36697 @cindex out-of-line single-stepping
36698 @item set displaced-stepping
36699 @itemx show displaced-stepping
36700 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36701 if the target supports it. Displaced stepping is a way to single-step
36702 over breakpoints without removing them from the inferior, by executing
36703 an out-of-line copy of the instruction that was originally at the
36704 breakpoint location. It is also known as out-of-line single-stepping.
36707 @item set displaced-stepping on
36708 If the target architecture supports it, @value{GDBN} will use
36709 displaced stepping to step over breakpoints.
36711 @item set displaced-stepping off
36712 @value{GDBN} will not use displaced stepping to step over breakpoints,
36713 even if such is supported by the target architecture.
36715 @cindex non-stop mode, and @samp{set displaced-stepping}
36716 @item set displaced-stepping auto
36717 This is the default mode. @value{GDBN} will use displaced stepping
36718 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36719 architecture supports displaced stepping.
36722 @kindex maint check-psymtabs
36723 @item maint check-psymtabs
36724 Check the consistency of currently expanded psymtabs versus symtabs.
36725 Use this to check, for example, whether a symbol is in one but not the other.
36727 @kindex maint check-symtabs
36728 @item maint check-symtabs
36729 Check the consistency of currently expanded symtabs.
36731 @kindex maint expand-symtabs
36732 @item maint expand-symtabs [@var{regexp}]
36733 Expand symbol tables.
36734 If @var{regexp} is specified, only expand symbol tables for file
36735 names matching @var{regexp}.
36737 @kindex maint cplus first_component
36738 @item maint cplus first_component @var{name}
36739 Print the first C@t{++} class/namespace component of @var{name}.
36741 @kindex maint cplus namespace
36742 @item maint cplus namespace
36743 Print the list of possible C@t{++} namespaces.
36745 @kindex maint demangle
36746 @item maint demangle @var{name}
36747 Demangle a C@t{++} or Objective-C mangled @var{name}.
36749 @kindex maint deprecate
36750 @kindex maint undeprecate
36751 @cindex deprecated commands
36752 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36753 @itemx maint undeprecate @var{command}
36754 Deprecate or undeprecate the named @var{command}. Deprecated commands
36755 cause @value{GDBN} to issue a warning when you use them. The optional
36756 argument @var{replacement} says which newer command should be used in
36757 favor of the deprecated one; if it is given, @value{GDBN} will mention
36758 the replacement as part of the warning.
36760 @kindex maint dump-me
36761 @item maint dump-me
36762 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36763 Cause a fatal signal in the debugger and force it to dump its core.
36764 This is supported only on systems which support aborting a program
36765 with the @code{SIGQUIT} signal.
36767 @kindex maint internal-error
36768 @kindex maint internal-warning
36769 @item maint internal-error @r{[}@var{message-text}@r{]}
36770 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36771 Cause @value{GDBN} to call the internal function @code{internal_error}
36772 or @code{internal_warning} and hence behave as though an internal error
36773 or internal warning has been detected. In addition to reporting the
36774 internal problem, these functions give the user the opportunity to
36775 either quit @value{GDBN} or create a core file of the current
36776 @value{GDBN} session.
36778 These commands take an optional parameter @var{message-text} that is
36779 used as the text of the error or warning message.
36781 Here's an example of using @code{internal-error}:
36784 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36785 @dots{}/maint.c:121: internal-error: testing, 1, 2
36786 A problem internal to GDB has been detected. Further
36787 debugging may prove unreliable.
36788 Quit this debugging session? (y or n) @kbd{n}
36789 Create a core file? (y or n) @kbd{n}
36793 @cindex @value{GDBN} internal error
36794 @cindex internal errors, control of @value{GDBN} behavior
36796 @kindex maint set internal-error
36797 @kindex maint show internal-error
36798 @kindex maint set internal-warning
36799 @kindex maint show internal-warning
36800 @item maint set internal-error @var{action} [ask|yes|no]
36801 @itemx maint show internal-error @var{action}
36802 @itemx maint set internal-warning @var{action} [ask|yes|no]
36803 @itemx maint show internal-warning @var{action}
36804 When @value{GDBN} reports an internal problem (error or warning) it
36805 gives the user the opportunity to both quit @value{GDBN} and create a
36806 core file of the current @value{GDBN} session. These commands let you
36807 override the default behaviour for each particular @var{action},
36808 described in the table below.
36812 You can specify that @value{GDBN} should always (yes) or never (no)
36813 quit. The default is to ask the user what to do.
36816 You can specify that @value{GDBN} should always (yes) or never (no)
36817 create a core file. The default is to ask the user what to do.
36820 @kindex maint packet
36821 @item maint packet @var{text}
36822 If @value{GDBN} is talking to an inferior via the serial protocol,
36823 then this command sends the string @var{text} to the inferior, and
36824 displays the response packet. @value{GDBN} supplies the initial
36825 @samp{$} character, the terminating @samp{#} character, and the
36828 @kindex maint print architecture
36829 @item maint print architecture @r{[}@var{file}@r{]}
36830 Print the entire architecture configuration. The optional argument
36831 @var{file} names the file where the output goes.
36833 @kindex maint print c-tdesc
36834 @item maint print c-tdesc
36835 Print the current target description (@pxref{Target Descriptions}) as
36836 a C source file. The created source file can be used in @value{GDBN}
36837 when an XML parser is not available to parse the description.
36839 @kindex maint print dummy-frames
36840 @item maint print dummy-frames
36841 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36844 (@value{GDBP}) @kbd{b add}
36846 (@value{GDBP}) @kbd{print add(2,3)}
36847 Breakpoint 2, add (a=2, b=3) at @dots{}
36849 The program being debugged stopped while in a function called from GDB.
36851 (@value{GDBP}) @kbd{maint print dummy-frames}
36852 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
36853 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
36854 call_lo=0x01014000 call_hi=0x01014001
36858 Takes an optional file parameter.
36860 @kindex maint print registers
36861 @kindex maint print raw-registers
36862 @kindex maint print cooked-registers
36863 @kindex maint print register-groups
36864 @kindex maint print remote-registers
36865 @item maint print registers @r{[}@var{file}@r{]}
36866 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36867 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36868 @itemx maint print register-groups @r{[}@var{file}@r{]}
36869 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36870 Print @value{GDBN}'s internal register data structures.
36872 The command @code{maint print raw-registers} includes the contents of
36873 the raw register cache; the command @code{maint print
36874 cooked-registers} includes the (cooked) value of all registers,
36875 including registers which aren't available on the target nor visible
36876 to user; the command @code{maint print register-groups} includes the
36877 groups that each register is a member of; and the command @code{maint
36878 print remote-registers} includes the remote target's register numbers
36879 and offsets in the `G' packets.
36881 These commands take an optional parameter, a file name to which to
36882 write the information.
36884 @kindex maint print reggroups
36885 @item maint print reggroups @r{[}@var{file}@r{]}
36886 Print @value{GDBN}'s internal register group data structures. The
36887 optional argument @var{file} tells to what file to write the
36890 The register groups info looks like this:
36893 (@value{GDBP}) @kbd{maint print reggroups}
36906 This command forces @value{GDBN} to flush its internal register cache.
36908 @kindex maint print objfiles
36909 @cindex info for known object files
36910 @item maint print objfiles @r{[}@var{regexp}@r{]}
36911 Print a dump of all known object files.
36912 If @var{regexp} is specified, only print object files whose names
36913 match @var{regexp}. For each object file, this command prints its name,
36914 address in memory, and all of its psymtabs and symtabs.
36916 @kindex maint print section-scripts
36917 @cindex info for known .debug_gdb_scripts-loaded scripts
36918 @item maint print section-scripts [@var{regexp}]
36919 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36920 If @var{regexp} is specified, only print scripts loaded by object files
36921 matching @var{regexp}.
36922 For each script, this command prints its name as specified in the objfile,
36923 and the full path if known.
36924 @xref{dotdebug_gdb_scripts section}.
36926 @kindex maint print statistics
36927 @cindex bcache statistics
36928 @item maint print statistics
36929 This command prints, for each object file in the program, various data
36930 about that object file followed by the byte cache (@dfn{bcache})
36931 statistics for the object file. The objfile data includes the number
36932 of minimal, partial, full, and stabs symbols, the number of types
36933 defined by the objfile, the number of as yet unexpanded psym tables,
36934 the number of line tables and string tables, and the amount of memory
36935 used by the various tables. The bcache statistics include the counts,
36936 sizes, and counts of duplicates of all and unique objects, max,
36937 average, and median entry size, total memory used and its overhead and
36938 savings, and various measures of the hash table size and chain
36941 @kindex maint print target-stack
36942 @cindex target stack description
36943 @item maint print target-stack
36944 A @dfn{target} is an interface between the debugger and a particular
36945 kind of file or process. Targets can be stacked in @dfn{strata},
36946 so that more than one target can potentially respond to a request.
36947 In particular, memory accesses will walk down the stack of targets
36948 until they find a target that is interested in handling that particular
36951 This command prints a short description of each layer that was pushed on
36952 the @dfn{target stack}, starting from the top layer down to the bottom one.
36954 @kindex maint print type
36955 @cindex type chain of a data type
36956 @item maint print type @var{expr}
36957 Print the type chain for a type specified by @var{expr}. The argument
36958 can be either a type name or a symbol. If it is a symbol, the type of
36959 that symbol is described. The type chain produced by this command is
36960 a recursive definition of the data type as stored in @value{GDBN}'s
36961 data structures, including its flags and contained types.
36963 @kindex maint set dwarf2 always-disassemble
36964 @kindex maint show dwarf2 always-disassemble
36965 @item maint set dwarf2 always-disassemble
36966 @item maint show dwarf2 always-disassemble
36967 Control the behavior of @code{info address} when using DWARF debugging
36970 The default is @code{off}, which means that @value{GDBN} should try to
36971 describe a variable's location in an easily readable format. When
36972 @code{on}, @value{GDBN} will instead display the DWARF location
36973 expression in an assembly-like format. Note that some locations are
36974 too complex for @value{GDBN} to describe simply; in this case you will
36975 always see the disassembly form.
36977 Here is an example of the resulting disassembly:
36980 (gdb) info addr argc
36981 Symbol "argc" is a complex DWARF expression:
36985 For more information on these expressions, see
36986 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36988 @kindex maint set dwarf2 max-cache-age
36989 @kindex maint show dwarf2 max-cache-age
36990 @item maint set dwarf2 max-cache-age
36991 @itemx maint show dwarf2 max-cache-age
36992 Control the DWARF 2 compilation unit cache.
36994 @cindex DWARF 2 compilation units cache
36995 In object files with inter-compilation-unit references, such as those
36996 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
36997 reader needs to frequently refer to previously read compilation units.
36998 This setting controls how long a compilation unit will remain in the
36999 cache if it is not referenced. A higher limit means that cached
37000 compilation units will be stored in memory longer, and more total
37001 memory will be used. Setting it to zero disables caching, which will
37002 slow down @value{GDBN} startup, but reduce memory consumption.
37004 @kindex maint set profile
37005 @kindex maint show profile
37006 @cindex profiling GDB
37007 @item maint set profile
37008 @itemx maint show profile
37009 Control profiling of @value{GDBN}.
37011 Profiling will be disabled until you use the @samp{maint set profile}
37012 command to enable it. When you enable profiling, the system will begin
37013 collecting timing and execution count data; when you disable profiling or
37014 exit @value{GDBN}, the results will be written to a log file. Remember that
37015 if you use profiling, @value{GDBN} will overwrite the profiling log file
37016 (often called @file{gmon.out}). If you have a record of important profiling
37017 data in a @file{gmon.out} file, be sure to move it to a safe location.
37019 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
37020 compiled with the @samp{-pg} compiler option.
37022 @kindex maint set show-debug-regs
37023 @kindex maint show show-debug-regs
37024 @cindex hardware debug registers
37025 @item maint set show-debug-regs
37026 @itemx maint show show-debug-regs
37027 Control whether to show variables that mirror the hardware debug
37028 registers. Use @code{ON} to enable, @code{OFF} to disable. If
37029 enabled, the debug registers values are shown when @value{GDBN} inserts or
37030 removes a hardware breakpoint or watchpoint, and when the inferior
37031 triggers a hardware-assisted breakpoint or watchpoint.
37033 @kindex maint set show-all-tib
37034 @kindex maint show show-all-tib
37035 @item maint set show-all-tib
37036 @itemx maint show show-all-tib
37037 Control whether to show all non zero areas within a 1k block starting
37038 at thread local base, when using the @samp{info w32 thread-information-block}
37041 @kindex maint set per-command
37042 @kindex maint show per-command
37043 @item maint set per-command
37044 @itemx maint show per-command
37045 @cindex resources used by commands
37047 @value{GDBN} can display the resources used by each command.
37048 This is useful in debugging performance problems.
37051 @item maint set per-command space [on|off]
37052 @itemx maint show per-command space
37053 Enable or disable the printing of the memory used by GDB for each command.
37054 If enabled, @value{GDBN} will display how much memory each command
37055 took, following the command's own output.
37056 This can also be requested by invoking @value{GDBN} with the
37057 @option{--statistics} command-line switch (@pxref{Mode Options}).
37059 @item maint set per-command time [on|off]
37060 @itemx maint show per-command time
37061 Enable or disable the printing of the execution time of @value{GDBN}
37063 If enabled, @value{GDBN} will display how much time it
37064 took to execute each command, following the command's own output.
37065 Both CPU time and wallclock time are printed.
37066 Printing both is useful when trying to determine whether the cost is
37067 CPU or, e.g., disk/network latency.
37068 Note that the CPU time printed is for @value{GDBN} only, it does not include
37069 the execution time of the inferior because there's no mechanism currently
37070 to compute how much time was spent by @value{GDBN} and how much time was
37071 spent by the program been debugged.
37072 This can also be requested by invoking @value{GDBN} with the
37073 @option{--statistics} command-line switch (@pxref{Mode Options}).
37075 @item maint set per-command symtab [on|off]
37076 @itemx maint show per-command symtab
37077 Enable or disable the printing of basic symbol table statistics
37079 If enabled, @value{GDBN} will display the following information:
37083 number of symbol tables
37085 number of primary symbol tables
37087 number of blocks in the blockvector
37091 @kindex maint space
37092 @cindex memory used by commands
37093 @item maint space @var{value}
37094 An alias for @code{maint set per-command space}.
37095 A non-zero value enables it, zero disables it.
37098 @cindex time of command execution
37099 @item maint time @var{value}
37100 An alias for @code{maint set per-command time}.
37101 A non-zero value enables it, zero disables it.
37103 @kindex maint translate-address
37104 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37105 Find the symbol stored at the location specified by the address
37106 @var{addr} and an optional section name @var{section}. If found,
37107 @value{GDBN} prints the name of the closest symbol and an offset from
37108 the symbol's location to the specified address. This is similar to
37109 the @code{info address} command (@pxref{Symbols}), except that this
37110 command also allows to find symbols in other sections.
37112 If section was not specified, the section in which the symbol was found
37113 is also printed. For dynamically linked executables, the name of
37114 executable or shared library containing the symbol is printed as well.
37118 The following command is useful for non-interactive invocations of
37119 @value{GDBN}, such as in the test suite.
37122 @item set watchdog @var{nsec}
37123 @kindex set watchdog
37124 @cindex watchdog timer
37125 @cindex timeout for commands
37126 Set the maximum number of seconds @value{GDBN} will wait for the
37127 target operation to finish. If this time expires, @value{GDBN}
37128 reports and error and the command is aborted.
37130 @item show watchdog
37131 Show the current setting of the target wait timeout.
37134 @node Remote Protocol
37135 @appendix @value{GDBN} Remote Serial Protocol
37140 * Stop Reply Packets::
37141 * General Query Packets::
37142 * Architecture-Specific Protocol Details::
37143 * Tracepoint Packets::
37144 * Host I/O Packets::
37146 * Notification Packets::
37147 * Remote Non-Stop::
37148 * Packet Acknowledgment::
37150 * File-I/O Remote Protocol Extension::
37151 * Library List Format::
37152 * Library List Format for SVR4 Targets::
37153 * Memory Map Format::
37154 * Thread List Format::
37155 * Traceframe Info Format::
37156 * Branch Trace Format::
37162 There may be occasions when you need to know something about the
37163 protocol---for example, if there is only one serial port to your target
37164 machine, you might want your program to do something special if it
37165 recognizes a packet meant for @value{GDBN}.
37167 In the examples below, @samp{->} and @samp{<-} are used to indicate
37168 transmitted and received data, respectively.
37170 @cindex protocol, @value{GDBN} remote serial
37171 @cindex serial protocol, @value{GDBN} remote
37172 @cindex remote serial protocol
37173 All @value{GDBN} commands and responses (other than acknowledgments
37174 and notifications, see @ref{Notification Packets}) are sent as a
37175 @var{packet}. A @var{packet} is introduced with the character
37176 @samp{$}, the actual @var{packet-data}, and the terminating character
37177 @samp{#} followed by a two-digit @var{checksum}:
37180 @code{$}@var{packet-data}@code{#}@var{checksum}
37184 @cindex checksum, for @value{GDBN} remote
37186 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37187 characters between the leading @samp{$} and the trailing @samp{#} (an
37188 eight bit unsigned checksum).
37190 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37191 specification also included an optional two-digit @var{sequence-id}:
37194 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37197 @cindex sequence-id, for @value{GDBN} remote
37199 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37200 has never output @var{sequence-id}s. Stubs that handle packets added
37201 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37203 When either the host or the target machine receives a packet, the first
37204 response expected is an acknowledgment: either @samp{+} (to indicate
37205 the package was received correctly) or @samp{-} (to request
37209 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37214 The @samp{+}/@samp{-} acknowledgments can be disabled
37215 once a connection is established.
37216 @xref{Packet Acknowledgment}, for details.
37218 The host (@value{GDBN}) sends @var{command}s, and the target (the
37219 debugging stub incorporated in your program) sends a @var{response}. In
37220 the case of step and continue @var{command}s, the response is only sent
37221 when the operation has completed, and the target has again stopped all
37222 threads in all attached processes. This is the default all-stop mode
37223 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37224 execution mode; see @ref{Remote Non-Stop}, for details.
37226 @var{packet-data} consists of a sequence of characters with the
37227 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37230 @cindex remote protocol, field separator
37231 Fields within the packet should be separated using @samp{,} @samp{;} or
37232 @samp{:}. Except where otherwise noted all numbers are represented in
37233 @sc{hex} with leading zeros suppressed.
37235 Implementors should note that prior to @value{GDBN} 5.0, the character
37236 @samp{:} could not appear as the third character in a packet (as it
37237 would potentially conflict with the @var{sequence-id}).
37239 @cindex remote protocol, binary data
37240 @anchor{Binary Data}
37241 Binary data in most packets is encoded either as two hexadecimal
37242 digits per byte of binary data. This allowed the traditional remote
37243 protocol to work over connections which were only seven-bit clean.
37244 Some packets designed more recently assume an eight-bit clean
37245 connection, and use a more efficient encoding to send and receive
37248 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37249 as an escape character. Any escaped byte is transmitted as the escape
37250 character followed by the original character XORed with @code{0x20}.
37251 For example, the byte @code{0x7d} would be transmitted as the two
37252 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37253 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37254 @samp{@}}) must always be escaped. Responses sent by the stub
37255 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37256 is not interpreted as the start of a run-length encoded sequence
37259 Response @var{data} can be run-length encoded to save space.
37260 Run-length encoding replaces runs of identical characters with one
37261 instance of the repeated character, followed by a @samp{*} and a
37262 repeat count. The repeat count is itself sent encoded, to avoid
37263 binary characters in @var{data}: a value of @var{n} is sent as
37264 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37265 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37266 code 32) for a repeat count of 3. (This is because run-length
37267 encoding starts to win for counts 3 or more.) Thus, for example,
37268 @samp{0* } is a run-length encoding of ``0000'': the space character
37269 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37272 The printable characters @samp{#} and @samp{$} or with a numeric value
37273 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37274 seven repeats (@samp{$}) can be expanded using a repeat count of only
37275 five (@samp{"}). For example, @samp{00000000} can be encoded as
37278 The error response returned for some packets includes a two character
37279 error number. That number is not well defined.
37281 @cindex empty response, for unsupported packets
37282 For any @var{command} not supported by the stub, an empty response
37283 (@samp{$#00}) should be returned. That way it is possible to extend the
37284 protocol. A newer @value{GDBN} can tell if a packet is supported based
37287 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37288 commands for register access, and the @samp{m} and @samp{M} commands
37289 for memory access. Stubs that only control single-threaded targets
37290 can implement run control with the @samp{c} (continue), and @samp{s}
37291 (step) commands. Stubs that support multi-threading targets should
37292 support the @samp{vCont} command. All other commands are optional.
37297 The following table provides a complete list of all currently defined
37298 @var{command}s and their corresponding response @var{data}.
37299 @xref{File-I/O Remote Protocol Extension}, for details about the File
37300 I/O extension of the remote protocol.
37302 Each packet's description has a template showing the packet's overall
37303 syntax, followed by an explanation of the packet's meaning. We
37304 include spaces in some of the templates for clarity; these are not
37305 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37306 separate its components. For example, a template like @samp{foo
37307 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37308 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37309 @var{baz}. @value{GDBN} does not transmit a space character between the
37310 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37313 @cindex @var{thread-id}, in remote protocol
37314 @anchor{thread-id syntax}
37315 Several packets and replies include a @var{thread-id} field to identify
37316 a thread. Normally these are positive numbers with a target-specific
37317 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37318 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37321 In addition, the remote protocol supports a multiprocess feature in
37322 which the @var{thread-id} syntax is extended to optionally include both
37323 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37324 The @var{pid} (process) and @var{tid} (thread) components each have the
37325 format described above: a positive number with target-specific
37326 interpretation formatted as a big-endian hex string, literal @samp{-1}
37327 to indicate all processes or threads (respectively), or @samp{0} to
37328 indicate an arbitrary process or thread. Specifying just a process, as
37329 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37330 error to specify all processes but a specific thread, such as
37331 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37332 for those packets and replies explicitly documented to include a process
37333 ID, rather than a @var{thread-id}.
37335 The multiprocess @var{thread-id} syntax extensions are only used if both
37336 @value{GDBN} and the stub report support for the @samp{multiprocess}
37337 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37340 Note that all packet forms beginning with an upper- or lower-case
37341 letter, other than those described here, are reserved for future use.
37343 Here are the packet descriptions.
37348 @cindex @samp{!} packet
37349 @anchor{extended mode}
37350 Enable extended mode. In extended mode, the remote server is made
37351 persistent. The @samp{R} packet is used to restart the program being
37357 The remote target both supports and has enabled extended mode.
37361 @cindex @samp{?} packet
37362 Indicate the reason the target halted. The reply is the same as for
37363 step and continue. This packet has a special interpretation when the
37364 target is in non-stop mode; see @ref{Remote Non-Stop}.
37367 @xref{Stop Reply Packets}, for the reply specifications.
37369 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37370 @cindex @samp{A} packet
37371 Initialized @code{argv[]} array passed into program. @var{arglen}
37372 specifies the number of bytes in the hex encoded byte stream
37373 @var{arg}. See @code{gdbserver} for more details.
37378 The arguments were set.
37384 @cindex @samp{b} packet
37385 (Don't use this packet; its behavior is not well-defined.)
37386 Change the serial line speed to @var{baud}.
37388 JTC: @emph{When does the transport layer state change? When it's
37389 received, or after the ACK is transmitted. In either case, there are
37390 problems if the command or the acknowledgment packet is dropped.}
37392 Stan: @emph{If people really wanted to add something like this, and get
37393 it working for the first time, they ought to modify ser-unix.c to send
37394 some kind of out-of-band message to a specially-setup stub and have the
37395 switch happen "in between" packets, so that from remote protocol's point
37396 of view, nothing actually happened.}
37398 @item B @var{addr},@var{mode}
37399 @cindex @samp{B} packet
37400 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37401 breakpoint at @var{addr}.
37403 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37404 (@pxref{insert breakpoint or watchpoint packet}).
37406 @cindex @samp{bc} packet
37409 Backward continue. Execute the target system in reverse. No parameter.
37410 @xref{Reverse Execution}, for more information.
37413 @xref{Stop Reply Packets}, for the reply specifications.
37415 @cindex @samp{bs} packet
37418 Backward single step. Execute one instruction in reverse. No parameter.
37419 @xref{Reverse Execution}, for more information.
37422 @xref{Stop Reply Packets}, for the reply specifications.
37424 @item c @r{[}@var{addr}@r{]}
37425 @cindex @samp{c} packet
37426 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
37427 resume at current address.
37429 This packet is deprecated for multi-threading support. @xref{vCont
37433 @xref{Stop Reply Packets}, for the reply specifications.
37435 @item C @var{sig}@r{[};@var{addr}@r{]}
37436 @cindex @samp{C} packet
37437 Continue with signal @var{sig} (hex signal number). If
37438 @samp{;@var{addr}} is omitted, resume at same address.
37440 This packet is deprecated for multi-threading support. @xref{vCont
37444 @xref{Stop Reply Packets}, for the reply specifications.
37447 @cindex @samp{d} packet
37450 Don't use this packet; instead, define a general set packet
37451 (@pxref{General Query Packets}).
37455 @cindex @samp{D} packet
37456 The first form of the packet is used to detach @value{GDBN} from the
37457 remote system. It is sent to the remote target
37458 before @value{GDBN} disconnects via the @code{detach} command.
37460 The second form, including a process ID, is used when multiprocess
37461 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37462 detach only a specific process. The @var{pid} is specified as a
37463 big-endian hex string.
37473 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37474 @cindex @samp{F} packet
37475 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37476 This is part of the File-I/O protocol extension. @xref{File-I/O
37477 Remote Protocol Extension}, for the specification.
37480 @anchor{read registers packet}
37481 @cindex @samp{g} packet
37482 Read general registers.
37486 @item @var{XX@dots{}}
37487 Each byte of register data is described by two hex digits. The bytes
37488 with the register are transmitted in target byte order. The size of
37489 each register and their position within the @samp{g} packet are
37490 determined by the @value{GDBN} internal gdbarch functions
37491 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
37492 specification of several standard @samp{g} packets is specified below.
37494 When reading registers from a trace frame (@pxref{Analyze Collected
37495 Data,,Using the Collected Data}), the stub may also return a string of
37496 literal @samp{x}'s in place of the register data digits, to indicate
37497 that the corresponding register has not been collected, thus its value
37498 is unavailable. For example, for an architecture with 4 registers of
37499 4 bytes each, the following reply indicates to @value{GDBN} that
37500 registers 0 and 2 have not been collected, while registers 1 and 3
37501 have been collected, and both have zero value:
37505 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37512 @item G @var{XX@dots{}}
37513 @cindex @samp{G} packet
37514 Write general registers. @xref{read registers packet}, for a
37515 description of the @var{XX@dots{}} data.
37525 @item H @var{op} @var{thread-id}
37526 @cindex @samp{H} packet
37527 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37528 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
37529 it should be @samp{c} for step and continue operations (note that this
37530 is deprecated, supporting the @samp{vCont} command is a better
37531 option), @samp{g} for other operations. The thread designator
37532 @var{thread-id} has the format and interpretation described in
37533 @ref{thread-id syntax}.
37544 @c 'H': How restrictive (or permissive) is the thread model. If a
37545 @c thread is selected and stopped, are other threads allowed
37546 @c to continue to execute? As I mentioned above, I think the
37547 @c semantics of each command when a thread is selected must be
37548 @c described. For example:
37550 @c 'g': If the stub supports threads and a specific thread is
37551 @c selected, returns the register block from that thread;
37552 @c otherwise returns current registers.
37554 @c 'G' If the stub supports threads and a specific thread is
37555 @c selected, sets the registers of the register block of
37556 @c that thread; otherwise sets current registers.
37558 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37559 @anchor{cycle step packet}
37560 @cindex @samp{i} packet
37561 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37562 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37563 step starting at that address.
37566 @cindex @samp{I} packet
37567 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37571 @cindex @samp{k} packet
37574 FIXME: @emph{There is no description of how to operate when a specific
37575 thread context has been selected (i.e.@: does 'k' kill only that
37578 @item m @var{addr},@var{length}
37579 @cindex @samp{m} packet
37580 Read @var{length} bytes of memory starting at address @var{addr}.
37581 Note that @var{addr} may not be aligned to any particular boundary.
37583 The stub need not use any particular size or alignment when gathering
37584 data from memory for the response; even if @var{addr} is word-aligned
37585 and @var{length} is a multiple of the word size, the stub is free to
37586 use byte accesses, or not. For this reason, this packet may not be
37587 suitable for accessing memory-mapped I/O devices.
37588 @cindex alignment of remote memory accesses
37589 @cindex size of remote memory accesses
37590 @cindex memory, alignment and size of remote accesses
37594 @item @var{XX@dots{}}
37595 Memory contents; each byte is transmitted as a two-digit hexadecimal
37596 number. The reply may contain fewer bytes than requested if the
37597 server was able to read only part of the region of memory.
37602 @item M @var{addr},@var{length}:@var{XX@dots{}}
37603 @cindex @samp{M} packet
37604 Write @var{length} bytes of memory starting at address @var{addr}.
37605 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
37606 hexadecimal number.
37613 for an error (this includes the case where only part of the data was
37618 @cindex @samp{p} packet
37619 Read the value of register @var{n}; @var{n} is in hex.
37620 @xref{read registers packet}, for a description of how the returned
37621 register value is encoded.
37625 @item @var{XX@dots{}}
37626 the register's value
37630 Indicating an unrecognized @var{query}.
37633 @item P @var{n@dots{}}=@var{r@dots{}}
37634 @anchor{write register packet}
37635 @cindex @samp{P} packet
37636 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37637 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37638 digits for each byte in the register (target byte order).
37648 @item q @var{name} @var{params}@dots{}
37649 @itemx Q @var{name} @var{params}@dots{}
37650 @cindex @samp{q} packet
37651 @cindex @samp{Q} packet
37652 General query (@samp{q}) and set (@samp{Q}). These packets are
37653 described fully in @ref{General Query Packets}.
37656 @cindex @samp{r} packet
37657 Reset the entire system.
37659 Don't use this packet; use the @samp{R} packet instead.
37662 @cindex @samp{R} packet
37663 Restart the program being debugged. @var{XX}, while needed, is ignored.
37664 This packet is only available in extended mode (@pxref{extended mode}).
37666 The @samp{R} packet has no reply.
37668 @item s @r{[}@var{addr}@r{]}
37669 @cindex @samp{s} packet
37670 Single step. @var{addr} is the address at which to resume. If
37671 @var{addr} is omitted, resume at same address.
37673 This packet is deprecated for multi-threading support. @xref{vCont
37677 @xref{Stop Reply Packets}, for the reply specifications.
37679 @item S @var{sig}@r{[};@var{addr}@r{]}
37680 @anchor{step with signal packet}
37681 @cindex @samp{S} packet
37682 Step with signal. This is analogous to the @samp{C} packet, but
37683 requests a single-step, rather than a normal resumption of execution.
37685 This packet is deprecated for multi-threading support. @xref{vCont
37689 @xref{Stop Reply Packets}, for the reply specifications.
37691 @item t @var{addr}:@var{PP},@var{MM}
37692 @cindex @samp{t} packet
37693 Search backwards starting at address @var{addr} for a match with pattern
37694 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
37695 @var{addr} must be at least 3 digits.
37697 @item T @var{thread-id}
37698 @cindex @samp{T} packet
37699 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37704 thread is still alive
37710 Packets starting with @samp{v} are identified by a multi-letter name,
37711 up to the first @samp{;} or @samp{?} (or the end of the packet).
37713 @item vAttach;@var{pid}
37714 @cindex @samp{vAttach} packet
37715 Attach to a new process with the specified process ID @var{pid}.
37716 The process ID is a
37717 hexadecimal integer identifying the process. In all-stop mode, all
37718 threads in the attached process are stopped; in non-stop mode, it may be
37719 attached without being stopped if that is supported by the target.
37721 @c In non-stop mode, on a successful vAttach, the stub should set the
37722 @c current thread to a thread of the newly-attached process. After
37723 @c attaching, GDB queries for the attached process's thread ID with qC.
37724 @c Also note that, from a user perspective, whether or not the
37725 @c target is stopped on attach in non-stop mode depends on whether you
37726 @c use the foreground or background version of the attach command, not
37727 @c on what vAttach does; GDB does the right thing with respect to either
37728 @c stopping or restarting threads.
37730 This packet is only available in extended mode (@pxref{extended mode}).
37736 @item @r{Any stop packet}
37737 for success in all-stop mode (@pxref{Stop Reply Packets})
37739 for success in non-stop mode (@pxref{Remote Non-Stop})
37742 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37743 @cindex @samp{vCont} packet
37744 @anchor{vCont packet}
37745 Resume the inferior, specifying different actions for each thread.
37746 If an action is specified with no @var{thread-id}, then it is applied to any
37747 threads that don't have a specific action specified; if no default action is
37748 specified then other threads should remain stopped in all-stop mode and
37749 in their current state in non-stop mode.
37750 Specifying multiple
37751 default actions is an error; specifying no actions is also an error.
37752 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
37754 Currently supported actions are:
37760 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37764 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37767 @item r @var{start},@var{end}
37768 Step once, and then keep stepping as long as the thread stops at
37769 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37770 The remote stub reports a stop reply when either the thread goes out
37771 of the range or is stopped due to an unrelated reason, such as hitting
37772 a breakpoint. @xref{range stepping}.
37774 If the range is empty (@var{start} == @var{end}), then the action
37775 becomes equivalent to the @samp{s} action. In other words,
37776 single-step once, and report the stop (even if the stepped instruction
37777 jumps to @var{start}).
37779 (A stop reply may be sent at any point even if the PC is still within
37780 the stepping range; for example, it is valid to implement this packet
37781 in a degenerate way as a single instruction step operation.)
37785 The optional argument @var{addr} normally associated with the
37786 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37787 not supported in @samp{vCont}.
37789 The @samp{t} action is only relevant in non-stop mode
37790 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37791 A stop reply should be generated for any affected thread not already stopped.
37792 When a thread is stopped by means of a @samp{t} action,
37793 the corresponding stop reply should indicate that the thread has stopped with
37794 signal @samp{0}, regardless of whether the target uses some other signal
37795 as an implementation detail.
37797 The stub must support @samp{vCont} if it reports support for
37798 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
37799 this case @samp{vCont} actions can be specified to apply to all threads
37800 in a process by using the @samp{p@var{pid}.-1} form of the
37804 @xref{Stop Reply Packets}, for the reply specifications.
37807 @cindex @samp{vCont?} packet
37808 Request a list of actions supported by the @samp{vCont} packet.
37812 @item vCont@r{[};@var{action}@dots{}@r{]}
37813 The @samp{vCont} packet is supported. Each @var{action} is a supported
37814 command in the @samp{vCont} packet.
37816 The @samp{vCont} packet is not supported.
37819 @item vFile:@var{operation}:@var{parameter}@dots{}
37820 @cindex @samp{vFile} packet
37821 Perform a file operation on the target system. For details,
37822 see @ref{Host I/O Packets}.
37824 @item vFlashErase:@var{addr},@var{length}
37825 @cindex @samp{vFlashErase} packet
37826 Direct the stub to erase @var{length} bytes of flash starting at
37827 @var{addr}. The region may enclose any number of flash blocks, but
37828 its start and end must fall on block boundaries, as indicated by the
37829 flash block size appearing in the memory map (@pxref{Memory Map
37830 Format}). @value{GDBN} groups flash memory programming operations
37831 together, and sends a @samp{vFlashDone} request after each group; the
37832 stub is allowed to delay erase operation until the @samp{vFlashDone}
37833 packet is received.
37843 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37844 @cindex @samp{vFlashWrite} packet
37845 Direct the stub to write data to flash address @var{addr}. The data
37846 is passed in binary form using the same encoding as for the @samp{X}
37847 packet (@pxref{Binary Data}). The memory ranges specified by
37848 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37849 not overlap, and must appear in order of increasing addresses
37850 (although @samp{vFlashErase} packets for higher addresses may already
37851 have been received; the ordering is guaranteed only between
37852 @samp{vFlashWrite} packets). If a packet writes to an address that was
37853 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37854 target-specific method, the results are unpredictable.
37862 for vFlashWrite addressing non-flash memory
37868 @cindex @samp{vFlashDone} packet
37869 Indicate to the stub that flash programming operation is finished.
37870 The stub is permitted to delay or batch the effects of a group of
37871 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37872 @samp{vFlashDone} packet is received. The contents of the affected
37873 regions of flash memory are unpredictable until the @samp{vFlashDone}
37874 request is completed.
37876 @item vKill;@var{pid}
37877 @cindex @samp{vKill} packet
37878 Kill the process with the specified process ID. @var{pid} is a
37879 hexadecimal integer identifying the process. This packet is used in
37880 preference to @samp{k} when multiprocess protocol extensions are
37881 supported; see @ref{multiprocess extensions}.
37891 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37892 @cindex @samp{vRun} packet
37893 Run the program @var{filename}, passing it each @var{argument} on its
37894 command line. The file and arguments are hex-encoded strings. If
37895 @var{filename} is an empty string, the stub may use a default program
37896 (e.g.@: the last program run). The program is created in the stopped
37899 @c FIXME: What about non-stop mode?
37901 This packet is only available in extended mode (@pxref{extended mode}).
37907 @item @r{Any stop packet}
37908 for success (@pxref{Stop Reply Packets})
37912 @cindex @samp{vStopped} packet
37913 @xref{Notification Packets}.
37915 @item X @var{addr},@var{length}:@var{XX@dots{}}
37917 @cindex @samp{X} packet
37918 Write data to memory, where the data is transmitted in binary.
37919 @var{addr} is address, @var{length} is number of bytes,
37920 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37930 @item z @var{type},@var{addr},@var{kind}
37931 @itemx Z @var{type},@var{addr},@var{kind}
37932 @anchor{insert breakpoint or watchpoint packet}
37933 @cindex @samp{z} packet
37934 @cindex @samp{Z} packets
37935 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37936 watchpoint starting at address @var{address} of kind @var{kind}.
37938 Each breakpoint and watchpoint packet @var{type} is documented
37941 @emph{Implementation notes: A remote target shall return an empty string
37942 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37943 remote target shall support either both or neither of a given
37944 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37945 avoid potential problems with duplicate packets, the operations should
37946 be implemented in an idempotent way.}
37948 @item z0,@var{addr},@var{kind}
37949 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37950 @cindex @samp{z0} packet
37951 @cindex @samp{Z0} packet
37952 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
37953 @var{addr} of type @var{kind}.
37955 A memory breakpoint is implemented by replacing the instruction at
37956 @var{addr} with a software breakpoint or trap instruction. The
37957 @var{kind} is target-specific and typically indicates the size of
37958 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
37959 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37960 architectures have additional meanings for @var{kind};
37961 @var{cond_list} is an optional list of conditional expressions in bytecode
37962 form that should be evaluated on the target's side. These are the
37963 conditions that should be taken into consideration when deciding if
37964 the breakpoint trigger should be reported back to @var{GDBN}.
37966 The @var{cond_list} parameter is comprised of a series of expressions,
37967 concatenated without separators. Each expression has the following form:
37971 @item X @var{len},@var{expr}
37972 @var{len} is the length of the bytecode expression and @var{expr} is the
37973 actual conditional expression in bytecode form.
37977 The optional @var{cmd_list} parameter introduces commands that may be
37978 run on the target, rather than being reported back to @value{GDBN}.
37979 The parameter starts with a numeric flag @var{persist}; if the flag is
37980 nonzero, then the breakpoint may remain active and the commands
37981 continue to be run even when @value{GDBN} disconnects from the target.
37982 Following this flag is a series of expressions concatenated with no
37983 separators. Each expression has the following form:
37987 @item X @var{len},@var{expr}
37988 @var{len} is the length of the bytecode expression and @var{expr} is the
37989 actual conditional expression in bytecode form.
37993 see @ref{Architecture-Specific Protocol Details}.
37995 @emph{Implementation note: It is possible for a target to copy or move
37996 code that contains memory breakpoints (e.g., when implementing
37997 overlays). The behavior of this packet, in the presence of such a
37998 target, is not defined.}
38010 @item z1,@var{addr},@var{kind}
38011 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
38012 @cindex @samp{z1} packet
38013 @cindex @samp{Z1} packet
38014 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
38015 address @var{addr}.
38017 A hardware breakpoint is implemented using a mechanism that is not
38018 dependant on being able to modify the target's memory. @var{kind}
38019 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
38021 @emph{Implementation note: A hardware breakpoint is not affected by code
38034 @item z2,@var{addr},@var{kind}
38035 @itemx Z2,@var{addr},@var{kind}
38036 @cindex @samp{z2} packet
38037 @cindex @samp{Z2} packet
38038 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
38039 @var{kind} is interpreted as the number of bytes to watch.
38051 @item z3,@var{addr},@var{kind}
38052 @itemx Z3,@var{addr},@var{kind}
38053 @cindex @samp{z3} packet
38054 @cindex @samp{Z3} packet
38055 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
38056 @var{kind} is interpreted as the number of bytes to watch.
38068 @item z4,@var{addr},@var{kind}
38069 @itemx Z4,@var{addr},@var{kind}
38070 @cindex @samp{z4} packet
38071 @cindex @samp{Z4} packet
38072 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
38073 @var{kind} is interpreted as the number of bytes to watch.
38087 @node Stop Reply Packets
38088 @section Stop Reply Packets
38089 @cindex stop reply packets
38091 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
38092 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38093 receive any of the below as a reply. Except for @samp{?}
38094 and @samp{vStopped}, that reply is only returned
38095 when the target halts. In the below the exact meaning of @dfn{signal
38096 number} is defined by the header @file{include/gdb/signals.h} in the
38097 @value{GDBN} source code.
38099 As in the description of request packets, we include spaces in the
38100 reply templates for clarity; these are not part of the reply packet's
38101 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38107 The program received signal number @var{AA} (a two-digit hexadecimal
38108 number). This is equivalent to a @samp{T} response with no
38109 @var{n}:@var{r} pairs.
38111 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38112 @cindex @samp{T} packet reply
38113 The program received signal number @var{AA} (a two-digit hexadecimal
38114 number). This is equivalent to an @samp{S} response, except that the
38115 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38116 and other information directly in the stop reply packet, reducing
38117 round-trip latency. Single-step and breakpoint traps are reported
38118 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38122 If @var{n} is a hexadecimal number, it is a register number, and the
38123 corresponding @var{r} gives that register's value. @var{r} is a
38124 series of bytes in target byte order, with each byte given by a
38125 two-digit hex number.
38128 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38129 the stopped thread, as specified in @ref{thread-id syntax}.
38132 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38133 the core on which the stop event was detected.
38136 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38137 specific event that stopped the target. The currently defined stop
38138 reasons are listed below. @var{aa} should be @samp{05}, the trap
38139 signal. At most one stop reason should be present.
38142 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38143 and go on to the next; this allows us to extend the protocol in the
38147 The currently defined stop reasons are:
38153 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38156 @cindex shared library events, remote reply
38158 The packet indicates that the loaded libraries have changed.
38159 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38160 list of loaded libraries. @var{r} is ignored.
38162 @cindex replay log events, remote reply
38164 The packet indicates that the target cannot continue replaying
38165 logged execution events, because it has reached the end (or the
38166 beginning when executing backward) of the log. The value of @var{r}
38167 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38168 for more information.
38172 @itemx W @var{AA} ; process:@var{pid}
38173 The process exited, and @var{AA} is the exit status. This is only
38174 applicable to certain targets.
38176 The second form of the response, including the process ID of the exited
38177 process, can be used only when @value{GDBN} has reported support for
38178 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38179 The @var{pid} is formatted as a big-endian hex string.
38182 @itemx X @var{AA} ; process:@var{pid}
38183 The process terminated with signal @var{AA}.
38185 The second form of the response, including the process ID of the
38186 terminated process, can be used only when @value{GDBN} has reported
38187 support for multiprocess protocol extensions; see @ref{multiprocess
38188 extensions}. The @var{pid} is formatted as a big-endian hex string.
38190 @item O @var{XX}@dots{}
38191 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38192 written as the program's console output. This can happen at any time
38193 while the program is running and the debugger should continue to wait
38194 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38196 @item F @var{call-id},@var{parameter}@dots{}
38197 @var{call-id} is the identifier which says which host system call should
38198 be called. This is just the name of the function. Translation into the
38199 correct system call is only applicable as it's defined in @value{GDBN}.
38200 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38203 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38204 this very system call.
38206 The target replies with this packet when it expects @value{GDBN} to
38207 call a host system call on behalf of the target. @value{GDBN} replies
38208 with an appropriate @samp{F} packet and keeps up waiting for the next
38209 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38210 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38211 Protocol Extension}, for more details.
38215 @node General Query Packets
38216 @section General Query Packets
38217 @cindex remote query requests
38219 Packets starting with @samp{q} are @dfn{general query packets};
38220 packets starting with @samp{Q} are @dfn{general set packets}. General
38221 query and set packets are a semi-unified form for retrieving and
38222 sending information to and from the stub.
38224 The initial letter of a query or set packet is followed by a name
38225 indicating what sort of thing the packet applies to. For example,
38226 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38227 definitions with the stub. These packet names follow some
38232 The name must not contain commas, colons or semicolons.
38234 Most @value{GDBN} query and set packets have a leading upper case
38237 The names of custom vendor packets should use a company prefix, in
38238 lower case, followed by a period. For example, packets designed at
38239 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38240 foos) or @samp{Qacme.bar} (for setting bars).
38243 The name of a query or set packet should be separated from any
38244 parameters by a @samp{:}; the parameters themselves should be
38245 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38246 full packet name, and check for a separator or the end of the packet,
38247 in case two packet names share a common prefix. New packets should not begin
38248 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38249 packets predate these conventions, and have arguments without any terminator
38250 for the packet name; we suspect they are in widespread use in places that
38251 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38252 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38255 Like the descriptions of the other packets, each description here
38256 has a template showing the packet's overall syntax, followed by an
38257 explanation of the packet's meaning. We include spaces in some of the
38258 templates for clarity; these are not part of the packet's syntax. No
38259 @value{GDBN} packet uses spaces to separate its components.
38261 Here are the currently defined query and set packets:
38267 Turn on or off the agent as a helper to perform some debugging operations
38268 delegated from @value{GDBN} (@pxref{Control Agent}).
38270 @item QAllow:@var{op}:@var{val}@dots{}
38271 @cindex @samp{QAllow} packet
38272 Specify which operations @value{GDBN} expects to request of the
38273 target, as a semicolon-separated list of operation name and value
38274 pairs. Possible values for @var{op} include @samp{WriteReg},
38275 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38276 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38277 indicating that @value{GDBN} will not request the operation, or 1,
38278 indicating that it may. (The target can then use this to set up its
38279 own internals optimally, for instance if the debugger never expects to
38280 insert breakpoints, it may not need to install its own trap handler.)
38283 @cindex current thread, remote request
38284 @cindex @samp{qC} packet
38285 Return the current thread ID.
38289 @item QC @var{thread-id}
38290 Where @var{thread-id} is a thread ID as documented in
38291 @ref{thread-id syntax}.
38292 @item @r{(anything else)}
38293 Any other reply implies the old thread ID.
38296 @item qCRC:@var{addr},@var{length}
38297 @cindex CRC of memory block, remote request
38298 @cindex @samp{qCRC} packet
38299 Compute the CRC checksum of a block of memory using CRC-32 defined in
38300 IEEE 802.3. The CRC is computed byte at a time, taking the most
38301 significant bit of each byte first. The initial pattern code
38302 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38304 @emph{Note:} This is the same CRC used in validating separate debug
38305 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38306 Files}). However the algorithm is slightly different. When validating
38307 separate debug files, the CRC is computed taking the @emph{least}
38308 significant bit of each byte first, and the final result is inverted to
38309 detect trailing zeros.
38314 An error (such as memory fault)
38315 @item C @var{crc32}
38316 The specified memory region's checksum is @var{crc32}.
38319 @item QDisableRandomization:@var{value}
38320 @cindex disable address space randomization, remote request
38321 @cindex @samp{QDisableRandomization} packet
38322 Some target operating systems will randomize the virtual address space
38323 of the inferior process as a security feature, but provide a feature
38324 to disable such randomization, e.g.@: to allow for a more deterministic
38325 debugging experience. On such systems, this packet with a @var{value}
38326 of 1 directs the target to disable address space randomization for
38327 processes subsequently started via @samp{vRun} packets, while a packet
38328 with a @var{value} of 0 tells the target to enable address space
38331 This packet is only available in extended mode (@pxref{extended mode}).
38336 The request succeeded.
38339 An error occurred. @var{nn} are hex digits.
38342 An empty reply indicates that @samp{QDisableRandomization} is not supported
38346 This packet is not probed by default; the remote stub must request it,
38347 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38348 This should only be done on targets that actually support disabling
38349 address space randomization.
38352 @itemx qsThreadInfo
38353 @cindex list active threads, remote request
38354 @cindex @samp{qfThreadInfo} packet
38355 @cindex @samp{qsThreadInfo} packet
38356 Obtain a list of all active thread IDs from the target (OS). Since there
38357 may be too many active threads to fit into one reply packet, this query
38358 works iteratively: it may require more than one query/reply sequence to
38359 obtain the entire list of threads. The first query of the sequence will
38360 be the @samp{qfThreadInfo} query; subsequent queries in the
38361 sequence will be the @samp{qsThreadInfo} query.
38363 NOTE: This packet replaces the @samp{qL} query (see below).
38367 @item m @var{thread-id}
38369 @item m @var{thread-id},@var{thread-id}@dots{}
38370 a comma-separated list of thread IDs
38372 (lower case letter @samp{L}) denotes end of list.
38375 In response to each query, the target will reply with a list of one or
38376 more thread IDs, separated by commas.
38377 @value{GDBN} will respond to each reply with a request for more thread
38378 ids (using the @samp{qs} form of the query), until the target responds
38379 with @samp{l} (lower-case ell, for @dfn{last}).
38380 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38383 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38384 @cindex get thread-local storage address, remote request
38385 @cindex @samp{qGetTLSAddr} packet
38386 Fetch the address associated with thread local storage specified
38387 by @var{thread-id}, @var{offset}, and @var{lm}.
38389 @var{thread-id} is the thread ID associated with the
38390 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38392 @var{offset} is the (big endian, hex encoded) offset associated with the
38393 thread local variable. (This offset is obtained from the debug
38394 information associated with the variable.)
38396 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38397 load module associated with the thread local storage. For example,
38398 a @sc{gnu}/Linux system will pass the link map address of the shared
38399 object associated with the thread local storage under consideration.
38400 Other operating environments may choose to represent the load module
38401 differently, so the precise meaning of this parameter will vary.
38405 @item @var{XX}@dots{}
38406 Hex encoded (big endian) bytes representing the address of the thread
38407 local storage requested.
38410 An error occurred. @var{nn} are hex digits.
38413 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38416 @item qGetTIBAddr:@var{thread-id}
38417 @cindex get thread information block address
38418 @cindex @samp{qGetTIBAddr} packet
38419 Fetch address of the Windows OS specific Thread Information Block.
38421 @var{thread-id} is the thread ID associated with the thread.
38425 @item @var{XX}@dots{}
38426 Hex encoded (big endian) bytes representing the linear address of the
38427 thread information block.
38430 An error occured. This means that either the thread was not found, or the
38431 address could not be retrieved.
38434 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38437 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38438 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38439 digit) is one to indicate the first query and zero to indicate a
38440 subsequent query; @var{threadcount} (two hex digits) is the maximum
38441 number of threads the response packet can contain; and @var{nextthread}
38442 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38443 returned in the response as @var{argthread}.
38445 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38449 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38450 Where: @var{count} (two hex digits) is the number of threads being
38451 returned; @var{done} (one hex digit) is zero to indicate more threads
38452 and one indicates no further threads; @var{argthreadid} (eight hex
38453 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38454 is a sequence of thread IDs from the target. @var{threadid} (eight hex
38455 digits). See @code{remote.c:parse_threadlist_response()}.
38459 @cindex section offsets, remote request
38460 @cindex @samp{qOffsets} packet
38461 Get section offsets that the target used when relocating the downloaded
38466 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38467 Relocate the @code{Text} section by @var{xxx} from its original address.
38468 Relocate the @code{Data} section by @var{yyy} from its original address.
38469 If the object file format provides segment information (e.g.@: @sc{elf}
38470 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38471 segments by the supplied offsets.
38473 @emph{Note: while a @code{Bss} offset may be included in the response,
38474 @value{GDBN} ignores this and instead applies the @code{Data} offset
38475 to the @code{Bss} section.}
38477 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38478 Relocate the first segment of the object file, which conventionally
38479 contains program code, to a starting address of @var{xxx}. If
38480 @samp{DataSeg} is specified, relocate the second segment, which
38481 conventionally contains modifiable data, to a starting address of
38482 @var{yyy}. @value{GDBN} will report an error if the object file
38483 does not contain segment information, or does not contain at least
38484 as many segments as mentioned in the reply. Extra segments are
38485 kept at fixed offsets relative to the last relocated segment.
38488 @item qP @var{mode} @var{thread-id}
38489 @cindex thread information, remote request
38490 @cindex @samp{qP} packet
38491 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38492 encoded 32 bit mode; @var{thread-id} is a thread ID
38493 (@pxref{thread-id syntax}).
38495 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38498 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38502 @cindex non-stop mode, remote request
38503 @cindex @samp{QNonStop} packet
38505 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38506 @xref{Remote Non-Stop}, for more information.
38511 The request succeeded.
38514 An error occurred. @var{nn} are hex digits.
38517 An empty reply indicates that @samp{QNonStop} is not supported by
38521 This packet is not probed by default; the remote stub must request it,
38522 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38523 Use of this packet is controlled by the @code{set non-stop} command;
38524 @pxref{Non-Stop Mode}.
38526 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38527 @cindex pass signals to inferior, remote request
38528 @cindex @samp{QPassSignals} packet
38529 @anchor{QPassSignals}
38530 Each listed @var{signal} should be passed directly to the inferior process.
38531 Signals are numbered identically to continue packets and stop replies
38532 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38533 strictly greater than the previous item. These signals do not need to stop
38534 the inferior, or be reported to @value{GDBN}. All other signals should be
38535 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38536 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38537 new list. This packet improves performance when using @samp{handle
38538 @var{signal} nostop noprint pass}.
38543 The request succeeded.
38546 An error occurred. @var{nn} are hex digits.
38549 An empty reply indicates that @samp{QPassSignals} is not supported by
38553 Use of this packet is controlled by the @code{set remote pass-signals}
38554 command (@pxref{Remote Configuration, set remote pass-signals}).
38555 This packet is not probed by default; the remote stub must request it,
38556 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38558 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38559 @cindex signals the inferior may see, remote request
38560 @cindex @samp{QProgramSignals} packet
38561 @anchor{QProgramSignals}
38562 Each listed @var{signal} may be delivered to the inferior process.
38563 Others should be silently discarded.
38565 In some cases, the remote stub may need to decide whether to deliver a
38566 signal to the program or not without @value{GDBN} involvement. One
38567 example of that is while detaching --- the program's threads may have
38568 stopped for signals that haven't yet had a chance of being reported to
38569 @value{GDBN}, and so the remote stub can use the signal list specified
38570 by this packet to know whether to deliver or ignore those pending
38573 This does not influence whether to deliver a signal as requested by a
38574 resumption packet (@pxref{vCont packet}).
38576 Signals are numbered identically to continue packets and stop replies
38577 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38578 strictly greater than the previous item. Multiple
38579 @samp{QProgramSignals} packets do not combine; any earlier
38580 @samp{QProgramSignals} list is completely replaced by the new list.
38585 The request succeeded.
38588 An error occurred. @var{nn} are hex digits.
38591 An empty reply indicates that @samp{QProgramSignals} is not supported
38595 Use of this packet is controlled by the @code{set remote program-signals}
38596 command (@pxref{Remote Configuration, set remote program-signals}).
38597 This packet is not probed by default; the remote stub must request it,
38598 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38600 @item qRcmd,@var{command}
38601 @cindex execute remote command, remote request
38602 @cindex @samp{qRcmd} packet
38603 @var{command} (hex encoded) is passed to the local interpreter for
38604 execution. Invalid commands should be reported using the output
38605 string. Before the final result packet, the target may also respond
38606 with a number of intermediate @samp{O@var{output}} console output
38607 packets. @emph{Implementors should note that providing access to a
38608 stubs's interpreter may have security implications}.
38613 A command response with no output.
38615 A command response with the hex encoded output string @var{OUTPUT}.
38617 Indicate a badly formed request.
38619 An empty reply indicates that @samp{qRcmd} is not recognized.
38622 (Note that the @code{qRcmd} packet's name is separated from the
38623 command by a @samp{,}, not a @samp{:}, contrary to the naming
38624 conventions above. Please don't use this packet as a model for new
38627 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38628 @cindex searching memory, in remote debugging
38630 @cindex @samp{qSearch:memory} packet
38632 @cindex @samp{qSearch memory} packet
38633 @anchor{qSearch memory}
38634 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38635 @var{address} and @var{length} are encoded in hex.
38636 @var{search-pattern} is a sequence of bytes, hex encoded.
38641 The pattern was not found.
38643 The pattern was found at @var{address}.
38645 A badly formed request or an error was encountered while searching memory.
38647 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38650 @item QStartNoAckMode
38651 @cindex @samp{QStartNoAckMode} packet
38652 @anchor{QStartNoAckMode}
38653 Request that the remote stub disable the normal @samp{+}/@samp{-}
38654 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38659 The stub has switched to no-acknowledgment mode.
38660 @value{GDBN} acknowledges this reponse,
38661 but neither the stub nor @value{GDBN} shall send or expect further
38662 @samp{+}/@samp{-} acknowledgments in the current connection.
38664 An empty reply indicates that the stub does not support no-acknowledgment mode.
38667 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38668 @cindex supported packets, remote query
38669 @cindex features of the remote protocol
38670 @cindex @samp{qSupported} packet
38671 @anchor{qSupported}
38672 Tell the remote stub about features supported by @value{GDBN}, and
38673 query the stub for features it supports. This packet allows
38674 @value{GDBN} and the remote stub to take advantage of each others'
38675 features. @samp{qSupported} also consolidates multiple feature probes
38676 at startup, to improve @value{GDBN} performance---a single larger
38677 packet performs better than multiple smaller probe packets on
38678 high-latency links. Some features may enable behavior which must not
38679 be on by default, e.g.@: because it would confuse older clients or
38680 stubs. Other features may describe packets which could be
38681 automatically probed for, but are not. These features must be
38682 reported before @value{GDBN} will use them. This ``default
38683 unsupported'' behavior is not appropriate for all packets, but it
38684 helps to keep the initial connection time under control with new
38685 versions of @value{GDBN} which support increasing numbers of packets.
38689 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38690 The stub supports or does not support each returned @var{stubfeature},
38691 depending on the form of each @var{stubfeature} (see below for the
38694 An empty reply indicates that @samp{qSupported} is not recognized,
38695 or that no features needed to be reported to @value{GDBN}.
38698 The allowed forms for each feature (either a @var{gdbfeature} in the
38699 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38703 @item @var{name}=@var{value}
38704 The remote protocol feature @var{name} is supported, and associated
38705 with the specified @var{value}. The format of @var{value} depends
38706 on the feature, but it must not include a semicolon.
38708 The remote protocol feature @var{name} is supported, and does not
38709 need an associated value.
38711 The remote protocol feature @var{name} is not supported.
38713 The remote protocol feature @var{name} may be supported, and
38714 @value{GDBN} should auto-detect support in some other way when it is
38715 needed. This form will not be used for @var{gdbfeature} notifications,
38716 but may be used for @var{stubfeature} responses.
38719 Whenever the stub receives a @samp{qSupported} request, the
38720 supplied set of @value{GDBN} features should override any previous
38721 request. This allows @value{GDBN} to put the stub in a known
38722 state, even if the stub had previously been communicating with
38723 a different version of @value{GDBN}.
38725 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38730 This feature indicates whether @value{GDBN} supports multiprocess
38731 extensions to the remote protocol. @value{GDBN} does not use such
38732 extensions unless the stub also reports that it supports them by
38733 including @samp{multiprocess+} in its @samp{qSupported} reply.
38734 @xref{multiprocess extensions}, for details.
38737 This feature indicates that @value{GDBN} supports the XML target
38738 description. If the stub sees @samp{xmlRegisters=} with target
38739 specific strings separated by a comma, it will report register
38743 This feature indicates whether @value{GDBN} supports the
38744 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38745 instruction reply packet}).
38748 Stubs should ignore any unknown values for
38749 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
38750 packet supports receiving packets of unlimited length (earlier
38751 versions of @value{GDBN} may reject overly long responses). Additional values
38752 for @var{gdbfeature} may be defined in the future to let the stub take
38753 advantage of new features in @value{GDBN}, e.g.@: incompatible
38754 improvements in the remote protocol---the @samp{multiprocess} feature is
38755 an example of such a feature. The stub's reply should be independent
38756 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
38757 describes all the features it supports, and then the stub replies with
38758 all the features it supports.
38760 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
38761 responses, as long as each response uses one of the standard forms.
38763 Some features are flags. A stub which supports a flag feature
38764 should respond with a @samp{+} form response. Other features
38765 require values, and the stub should respond with an @samp{=}
38768 Each feature has a default value, which @value{GDBN} will use if
38769 @samp{qSupported} is not available or if the feature is not mentioned
38770 in the @samp{qSupported} response. The default values are fixed; a
38771 stub is free to omit any feature responses that match the defaults.
38773 Not all features can be probed, but for those which can, the probing
38774 mechanism is useful: in some cases, a stub's internal
38775 architecture may not allow the protocol layer to know some information
38776 about the underlying target in advance. This is especially common in
38777 stubs which may be configured for multiple targets.
38779 These are the currently defined stub features and their properties:
38781 @multitable @columnfractions 0.35 0.2 0.12 0.2
38782 @c NOTE: The first row should be @headitem, but we do not yet require
38783 @c a new enough version of Texinfo (4.7) to use @headitem.
38785 @tab Value Required
38789 @item @samp{PacketSize}
38794 @item @samp{qXfer:auxv:read}
38799 @item @samp{qXfer:btrace:read}
38804 @item @samp{qXfer:features:read}
38809 @item @samp{qXfer:libraries:read}
38814 @item @samp{qXfer:libraries-svr4:read}
38819 @item @samp{augmented-libraries-svr4-read}
38824 @item @samp{qXfer:memory-map:read}
38829 @item @samp{qXfer:sdata:read}
38834 @item @samp{qXfer:spu:read}
38839 @item @samp{qXfer:spu:write}
38844 @item @samp{qXfer:siginfo:read}
38849 @item @samp{qXfer:siginfo:write}
38854 @item @samp{qXfer:threads:read}
38859 @item @samp{qXfer:traceframe-info:read}
38864 @item @samp{qXfer:uib:read}
38869 @item @samp{qXfer:fdpic:read}
38874 @item @samp{Qbtrace:off}
38879 @item @samp{Qbtrace:bts}
38884 @item @samp{QNonStop}
38889 @item @samp{QPassSignals}
38894 @item @samp{QStartNoAckMode}
38899 @item @samp{multiprocess}
38904 @item @samp{ConditionalBreakpoints}
38909 @item @samp{ConditionalTracepoints}
38914 @item @samp{ReverseContinue}
38919 @item @samp{ReverseStep}
38924 @item @samp{TracepointSource}
38929 @item @samp{QAgent}
38934 @item @samp{QAllow}
38939 @item @samp{QDisableRandomization}
38944 @item @samp{EnableDisableTracepoints}
38949 @item @samp{QTBuffer:size}
38954 @item @samp{tracenz}
38959 @item @samp{BreakpointCommands}
38966 These are the currently defined stub features, in more detail:
38969 @cindex packet size, remote protocol
38970 @item PacketSize=@var{bytes}
38971 The remote stub can accept packets up to at least @var{bytes} in
38972 length. @value{GDBN} will send packets up to this size for bulk
38973 transfers, and will never send larger packets. This is a limit on the
38974 data characters in the packet, including the frame and checksum.
38975 There is no trailing NUL byte in a remote protocol packet; if the stub
38976 stores packets in a NUL-terminated format, it should allow an extra
38977 byte in its buffer for the NUL. If this stub feature is not supported,
38978 @value{GDBN} guesses based on the size of the @samp{g} packet response.
38980 @item qXfer:auxv:read
38981 The remote stub understands the @samp{qXfer:auxv:read} packet
38982 (@pxref{qXfer auxiliary vector read}).
38984 @item qXfer:btrace:read
38985 The remote stub understands the @samp{qXfer:btrace:read}
38986 packet (@pxref{qXfer btrace read}).
38988 @item qXfer:features:read
38989 The remote stub understands the @samp{qXfer:features:read} packet
38990 (@pxref{qXfer target description read}).
38992 @item qXfer:libraries:read
38993 The remote stub understands the @samp{qXfer:libraries:read} packet
38994 (@pxref{qXfer library list read}).
38996 @item qXfer:libraries-svr4:read
38997 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
38998 (@pxref{qXfer svr4 library list read}).
39000 @item augmented-libraries-svr4-read
39001 The remote stub understands the augmented form of the
39002 @samp{qXfer:libraries-svr4:read} packet
39003 (@pxref{qXfer svr4 library list read}).
39005 @item qXfer:memory-map:read
39006 The remote stub understands the @samp{qXfer:memory-map:read} packet
39007 (@pxref{qXfer memory map read}).
39009 @item qXfer:sdata:read
39010 The remote stub understands the @samp{qXfer:sdata:read} packet
39011 (@pxref{qXfer sdata read}).
39013 @item qXfer:spu:read
39014 The remote stub understands the @samp{qXfer:spu:read} packet
39015 (@pxref{qXfer spu read}).
39017 @item qXfer:spu:write
39018 The remote stub understands the @samp{qXfer:spu:write} packet
39019 (@pxref{qXfer spu write}).
39021 @item qXfer:siginfo:read
39022 The remote stub understands the @samp{qXfer:siginfo:read} packet
39023 (@pxref{qXfer siginfo read}).
39025 @item qXfer:siginfo:write
39026 The remote stub understands the @samp{qXfer:siginfo:write} packet
39027 (@pxref{qXfer siginfo write}).
39029 @item qXfer:threads:read
39030 The remote stub understands the @samp{qXfer:threads:read} packet
39031 (@pxref{qXfer threads read}).
39033 @item qXfer:traceframe-info:read
39034 The remote stub understands the @samp{qXfer:traceframe-info:read}
39035 packet (@pxref{qXfer traceframe info read}).
39037 @item qXfer:uib:read
39038 The remote stub understands the @samp{qXfer:uib:read}
39039 packet (@pxref{qXfer unwind info block}).
39041 @item qXfer:fdpic:read
39042 The remote stub understands the @samp{qXfer:fdpic:read}
39043 packet (@pxref{qXfer fdpic loadmap read}).
39046 The remote stub understands the @samp{QNonStop} packet
39047 (@pxref{QNonStop}).
39050 The remote stub understands the @samp{QPassSignals} packet
39051 (@pxref{QPassSignals}).
39053 @item QStartNoAckMode
39054 The remote stub understands the @samp{QStartNoAckMode} packet and
39055 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
39058 @anchor{multiprocess extensions}
39059 @cindex multiprocess extensions, in remote protocol
39060 The remote stub understands the multiprocess extensions to the remote
39061 protocol syntax. The multiprocess extensions affect the syntax of
39062 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
39063 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
39064 replies. Note that reporting this feature indicates support for the
39065 syntactic extensions only, not that the stub necessarily supports
39066 debugging of more than one process at a time. The stub must not use
39067 multiprocess extensions in packet replies unless @value{GDBN} has also
39068 indicated it supports them in its @samp{qSupported} request.
39070 @item qXfer:osdata:read
39071 The remote stub understands the @samp{qXfer:osdata:read} packet
39072 ((@pxref{qXfer osdata read}).
39074 @item ConditionalBreakpoints
39075 The target accepts and implements evaluation of conditional expressions
39076 defined for breakpoints. The target will only report breakpoint triggers
39077 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
39079 @item ConditionalTracepoints
39080 The remote stub accepts and implements conditional expressions defined
39081 for tracepoints (@pxref{Tracepoint Conditions}).
39083 @item ReverseContinue
39084 The remote stub accepts and implements the reverse continue packet
39088 The remote stub accepts and implements the reverse step packet
39091 @item TracepointSource
39092 The remote stub understands the @samp{QTDPsrc} packet that supplies
39093 the source form of tracepoint definitions.
39096 The remote stub understands the @samp{QAgent} packet.
39099 The remote stub understands the @samp{QAllow} packet.
39101 @item QDisableRandomization
39102 The remote stub understands the @samp{QDisableRandomization} packet.
39104 @item StaticTracepoint
39105 @cindex static tracepoints, in remote protocol
39106 The remote stub supports static tracepoints.
39108 @item InstallInTrace
39109 @anchor{install tracepoint in tracing}
39110 The remote stub supports installing tracepoint in tracing.
39112 @item EnableDisableTracepoints
39113 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39114 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39115 to be enabled and disabled while a trace experiment is running.
39117 @item QTBuffer:size
39118 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39119 packet that allows to change the size of the trace buffer.
39122 @cindex string tracing, in remote protocol
39123 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39124 See @ref{Bytecode Descriptions} for details about the bytecode.
39126 @item BreakpointCommands
39127 @cindex breakpoint commands, in remote protocol
39128 The remote stub supports running a breakpoint's command list itself,
39129 rather than reporting the hit to @value{GDBN}.
39132 The remote stub understands the @samp{Qbtrace:off} packet.
39135 The remote stub understands the @samp{Qbtrace:bts} packet.
39140 @cindex symbol lookup, remote request
39141 @cindex @samp{qSymbol} packet
39142 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39143 requests. Accept requests from the target for the values of symbols.
39148 The target does not need to look up any (more) symbols.
39149 @item qSymbol:@var{sym_name}
39150 The target requests the value of symbol @var{sym_name} (hex encoded).
39151 @value{GDBN} may provide the value by using the
39152 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39156 @item qSymbol:@var{sym_value}:@var{sym_name}
39157 Set the value of @var{sym_name} to @var{sym_value}.
39159 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39160 target has previously requested.
39162 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39163 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39169 The target does not need to look up any (more) symbols.
39170 @item qSymbol:@var{sym_name}
39171 The target requests the value of a new symbol @var{sym_name} (hex
39172 encoded). @value{GDBN} will continue to supply the values of symbols
39173 (if available), until the target ceases to request them.
39178 @itemx QTDisconnected
39185 @itemx qTMinFTPILen
39187 @xref{Tracepoint Packets}.
39189 @item qThreadExtraInfo,@var{thread-id}
39190 @cindex thread attributes info, remote request
39191 @cindex @samp{qThreadExtraInfo} packet
39192 Obtain a printable string description of a thread's attributes from
39193 the target OS. @var{thread-id} is a thread ID;
39194 see @ref{thread-id syntax}. This
39195 string may contain anything that the target OS thinks is interesting
39196 for @value{GDBN} to tell the user about the thread. The string is
39197 displayed in @value{GDBN}'s @code{info threads} display. Some
39198 examples of possible thread extra info strings are @samp{Runnable}, or
39199 @samp{Blocked on Mutex}.
39203 @item @var{XX}@dots{}
39204 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39205 comprising the printable string containing the extra information about
39206 the thread's attributes.
39209 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39210 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39211 conventions above. Please don't use this packet as a model for new
39230 @xref{Tracepoint Packets}.
39232 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39233 @cindex read special object, remote request
39234 @cindex @samp{qXfer} packet
39235 @anchor{qXfer read}
39236 Read uninterpreted bytes from the target's special data area
39237 identified by the keyword @var{object}. Request @var{length} bytes
39238 starting at @var{offset} bytes into the data. The content and
39239 encoding of @var{annex} is specific to @var{object}; it can supply
39240 additional details about what data to access.
39242 Here are the specific requests of this form defined so far. All
39243 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39244 formats, listed below.
39247 @item qXfer:auxv:read::@var{offset},@var{length}
39248 @anchor{qXfer auxiliary vector read}
39249 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39250 auxiliary vector}. Note @var{annex} must be empty.
39252 This packet is not probed by default; the remote stub must request it,
39253 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39255 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39256 @anchor{qXfer btrace read}
39258 Return a description of the current branch trace.
39259 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39260 packet may have one of the following values:
39264 Returns all available branch trace.
39267 Returns all available branch trace if the branch trace changed since
39268 the last read request.
39271 This packet is not probed by default; the remote stub must request it
39272 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39274 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39275 @anchor{qXfer target description read}
39276 Access the @dfn{target description}. @xref{Target Descriptions}. The
39277 annex specifies which XML document to access. The main description is
39278 always loaded from the @samp{target.xml} annex.
39280 This packet is not probed by default; the remote stub must request it,
39281 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39283 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39284 @anchor{qXfer library list read}
39285 Access the target's list of loaded libraries. @xref{Library List Format}.
39286 The annex part of the generic @samp{qXfer} packet must be empty
39287 (@pxref{qXfer read}).
39289 Targets which maintain a list of libraries in the program's memory do
39290 not need to implement this packet; it is designed for platforms where
39291 the operating system manages the list of loaded libraries.
39293 This packet is not probed by default; the remote stub must request it,
39294 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39296 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39297 @anchor{qXfer svr4 library list read}
39298 Access the target's list of loaded libraries when the target is an SVR4
39299 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39300 of the generic @samp{qXfer} packet must be empty unless the remote
39301 stub indicated it supports the augmented form of this packet
39302 by supplying an appropriate @samp{qSupported} response
39303 (@pxref{qXfer read}, @ref{qSupported}).
39305 This packet is optional for better performance on SVR4 targets.
39306 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39308 This packet is not probed by default; the remote stub must request it,
39309 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39311 If the remote stub indicates it supports the augmented form of this
39312 packet then the annex part of the generic @samp{qXfer} packet may
39313 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39314 arguments. The currently supported arguments are:
39317 @item start=@var{address}
39318 A hexadecimal number specifying the address of the @samp{struct
39319 link_map} to start reading the library list from. If unset or zero
39320 then the first @samp{struct link_map} in the library list will be
39321 chosen as the starting point.
39323 @item prev=@var{address}
39324 A hexadecimal number specifying the address of the @samp{struct
39325 link_map} immediately preceding the @samp{struct link_map}
39326 specified by the @samp{start} argument. If unset or zero then
39327 the remote stub will expect that no @samp{struct link_map}
39328 exists prior to the starting point.
39332 Arguments that are not understood by the remote stub will be silently
39335 @item qXfer:memory-map:read::@var{offset},@var{length}
39336 @anchor{qXfer memory map read}
39337 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39338 annex part of the generic @samp{qXfer} packet must be empty
39339 (@pxref{qXfer read}).
39341 This packet is not probed by default; the remote stub must request it,
39342 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39344 @item qXfer:sdata:read::@var{offset},@var{length}
39345 @anchor{qXfer sdata read}
39347 Read contents of the extra collected static tracepoint marker
39348 information. The annex part of the generic @samp{qXfer} packet must
39349 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39352 This packet is not probed by default; the remote stub must request it,
39353 by supplying an appropriate @samp{qSupported} response
39354 (@pxref{qSupported}).
39356 @item qXfer:siginfo:read::@var{offset},@var{length}
39357 @anchor{qXfer siginfo read}
39358 Read contents of the extra signal information on the target
39359 system. The annex part of the generic @samp{qXfer} packet must be
39360 empty (@pxref{qXfer read}).
39362 This packet is not probed by default; the remote stub must request it,
39363 by supplying an appropriate @samp{qSupported} response
39364 (@pxref{qSupported}).
39366 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39367 @anchor{qXfer spu read}
39368 Read contents of an @code{spufs} file on the target system. The
39369 annex specifies which file to read; it must be of the form
39370 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39371 in the target process, and @var{name} identifes the @code{spufs} file
39372 in that context to be accessed.
39374 This packet is not probed by default; the remote stub must request it,
39375 by supplying an appropriate @samp{qSupported} response
39376 (@pxref{qSupported}).
39378 @item qXfer:threads:read::@var{offset},@var{length}
39379 @anchor{qXfer threads read}
39380 Access the list of threads on target. @xref{Thread List Format}. The
39381 annex part of the generic @samp{qXfer} packet must be empty
39382 (@pxref{qXfer read}).
39384 This packet is not probed by default; the remote stub must request it,
39385 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39387 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39388 @anchor{qXfer traceframe info read}
39390 Return a description of the current traceframe's contents.
39391 @xref{Traceframe Info Format}. The annex part of the generic
39392 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39394 This packet is not probed by default; the remote stub must request it,
39395 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39397 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39398 @anchor{qXfer unwind info block}
39400 Return the unwind information block for @var{pc}. This packet is used
39401 on OpenVMS/ia64 to ask the kernel unwind information.
39403 This packet is not probed by default.
39405 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39406 @anchor{qXfer fdpic loadmap read}
39407 Read contents of @code{loadmap}s on the target system. The
39408 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39409 executable @code{loadmap} or interpreter @code{loadmap} to read.
39411 This packet is not probed by default; the remote stub must request it,
39412 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39414 @item qXfer:osdata:read::@var{offset},@var{length}
39415 @anchor{qXfer osdata read}
39416 Access the target's @dfn{operating system information}.
39417 @xref{Operating System Information}.
39424 Data @var{data} (@pxref{Binary Data}) has been read from the
39425 target. There may be more data at a higher address (although
39426 it is permitted to return @samp{m} even for the last valid
39427 block of data, as long as at least one byte of data was read).
39428 @var{data} may have fewer bytes than the @var{length} in the
39432 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39433 There is no more data to be read. @var{data} may have fewer bytes
39434 than the @var{length} in the request.
39437 The @var{offset} in the request is at the end of the data.
39438 There is no more data to be read.
39441 The request was malformed, or @var{annex} was invalid.
39444 The offset was invalid, or there was an error encountered reading the data.
39445 @var{nn} is a hex-encoded @code{errno} value.
39448 An empty reply indicates the @var{object} string was not recognized by
39449 the stub, or that the object does not support reading.
39452 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39453 @cindex write data into object, remote request
39454 @anchor{qXfer write}
39455 Write uninterpreted bytes into the target's special data area
39456 identified by the keyword @var{object}, starting at @var{offset} bytes
39457 into the data. @var{data}@dots{} is the binary-encoded data
39458 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
39459 is specific to @var{object}; it can supply additional details about what data
39462 Here are the specific requests of this form defined so far. All
39463 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39464 formats, listed below.
39467 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39468 @anchor{qXfer siginfo write}
39469 Write @var{data} to the extra signal information on the target system.
39470 The annex part of the generic @samp{qXfer} packet must be
39471 empty (@pxref{qXfer write}).
39473 This packet is not probed by default; the remote stub must request it,
39474 by supplying an appropriate @samp{qSupported} response
39475 (@pxref{qSupported}).
39477 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39478 @anchor{qXfer spu write}
39479 Write @var{data} to an @code{spufs} file on the target system. The
39480 annex specifies which file to write; it must be of the form
39481 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39482 in the target process, and @var{name} identifes the @code{spufs} file
39483 in that context to be accessed.
39485 This packet is not probed by default; the remote stub must request it,
39486 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39492 @var{nn} (hex encoded) is the number of bytes written.
39493 This may be fewer bytes than supplied in the request.
39496 The request was malformed, or @var{annex} was invalid.
39499 The offset was invalid, or there was an error encountered writing the data.
39500 @var{nn} is a hex-encoded @code{errno} value.
39503 An empty reply indicates the @var{object} string was not
39504 recognized by the stub, or that the object does not support writing.
39507 @item qXfer:@var{object}:@var{operation}:@dots{}
39508 Requests of this form may be added in the future. When a stub does
39509 not recognize the @var{object} keyword, or its support for
39510 @var{object} does not recognize the @var{operation} keyword, the stub
39511 must respond with an empty packet.
39513 @item qAttached:@var{pid}
39514 @cindex query attached, remote request
39515 @cindex @samp{qAttached} packet
39516 Return an indication of whether the remote server attached to an
39517 existing process or created a new process. When the multiprocess
39518 protocol extensions are supported (@pxref{multiprocess extensions}),
39519 @var{pid} is an integer in hexadecimal format identifying the target
39520 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39521 the query packet will be simplified as @samp{qAttached}.
39523 This query is used, for example, to know whether the remote process
39524 should be detached or killed when a @value{GDBN} session is ended with
39525 the @code{quit} command.
39530 The remote server attached to an existing process.
39532 The remote server created a new process.
39534 A badly formed request or an error was encountered.
39538 Enable branch tracing for the current thread using bts tracing.
39543 Branch tracing has been enabled.
39545 A badly formed request or an error was encountered.
39549 Disable branch tracing for the current thread.
39554 Branch tracing has been disabled.
39556 A badly formed request or an error was encountered.
39561 @node Architecture-Specific Protocol Details
39562 @section Architecture-Specific Protocol Details
39564 This section describes how the remote protocol is applied to specific
39565 target architectures. Also see @ref{Standard Target Features}, for
39566 details of XML target descriptions for each architecture.
39569 * ARM-Specific Protocol Details::
39570 * MIPS-Specific Protocol Details::
39573 @node ARM-Specific Protocol Details
39574 @subsection @acronym{ARM}-specific Protocol Details
39577 * ARM Breakpoint Kinds::
39580 @node ARM Breakpoint Kinds
39581 @subsubsection @acronym{ARM} Breakpoint Kinds
39582 @cindex breakpoint kinds, @acronym{ARM}
39584 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39589 16-bit Thumb mode breakpoint.
39592 32-bit Thumb mode (Thumb-2) breakpoint.
39595 32-bit @acronym{ARM} mode breakpoint.
39599 @node MIPS-Specific Protocol Details
39600 @subsection @acronym{MIPS}-specific Protocol Details
39603 * MIPS Register packet Format::
39604 * MIPS Breakpoint Kinds::
39607 @node MIPS Register packet Format
39608 @subsubsection @acronym{MIPS} Register Packet Format
39609 @cindex register packet format, @acronym{MIPS}
39611 The following @code{g}/@code{G} packets have previously been defined.
39612 In the below, some thirty-two bit registers are transferred as
39613 sixty-four bits. Those registers should be zero/sign extended (which?)
39614 to fill the space allocated. Register bytes are transferred in target
39615 byte order. The two nibbles within a register byte are transferred
39616 most-significant -- least-significant.
39621 All registers are transferred as thirty-two bit quantities in the order:
39622 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
39623 registers; fsr; fir; fp.
39626 All registers are transferred as sixty-four bit quantities (including
39627 thirty-two bit registers such as @code{sr}). The ordering is the same
39632 @node MIPS Breakpoint Kinds
39633 @subsubsection @acronym{MIPS} Breakpoint Kinds
39634 @cindex breakpoint kinds, @acronym{MIPS}
39636 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39641 16-bit @acronym{MIPS16} mode breakpoint.
39644 16-bit @acronym{microMIPS} mode breakpoint.
39647 32-bit standard @acronym{MIPS} mode breakpoint.
39650 32-bit @acronym{microMIPS} mode breakpoint.
39654 @node Tracepoint Packets
39655 @section Tracepoint Packets
39656 @cindex tracepoint packets
39657 @cindex packets, tracepoint
39659 Here we describe the packets @value{GDBN} uses to implement
39660 tracepoints (@pxref{Tracepoints}).
39664 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
39665 @cindex @samp{QTDP} packet
39666 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
39667 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
39668 the tracepoint is disabled. @var{step} is the tracepoint's step
39669 count, and @var{pass} is its pass count. If an @samp{F} is present,
39670 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
39671 the number of bytes that the target should copy elsewhere to make room
39672 for the tracepoint. If an @samp{X} is present, it introduces a
39673 tracepoint condition, which consists of a hexadecimal length, followed
39674 by a comma and hex-encoded bytes, in a manner similar to action
39675 encodings as described below. If the trailing @samp{-} is present,
39676 further @samp{QTDP} packets will follow to specify this tracepoint's
39682 The packet was understood and carried out.
39684 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39686 The packet was not recognized.
39689 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
39690 Define actions to be taken when a tracepoint is hit. @var{n} and
39691 @var{addr} must be the same as in the initial @samp{QTDP} packet for
39692 this tracepoint. This packet may only be sent immediately after
39693 another @samp{QTDP} packet that ended with a @samp{-}. If the
39694 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
39695 specifying more actions for this tracepoint.
39697 In the series of action packets for a given tracepoint, at most one
39698 can have an @samp{S} before its first @var{action}. If such a packet
39699 is sent, it and the following packets define ``while-stepping''
39700 actions. Any prior packets define ordinary actions --- that is, those
39701 taken when the tracepoint is first hit. If no action packet has an
39702 @samp{S}, then all the packets in the series specify ordinary
39703 tracepoint actions.
39705 The @samp{@var{action}@dots{}} portion of the packet is a series of
39706 actions, concatenated without separators. Each action has one of the
39712 Collect the registers whose bits are set in @var{mask}. @var{mask} is
39713 a hexadecimal number whose @var{i}'th bit is set if register number
39714 @var{i} should be collected. (The least significant bit is numbered
39715 zero.) Note that @var{mask} may be any number of digits long; it may
39716 not fit in a 32-bit word.
39718 @item M @var{basereg},@var{offset},@var{len}
39719 Collect @var{len} bytes of memory starting at the address in register
39720 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39721 @samp{-1}, then the range has a fixed address: @var{offset} is the
39722 address of the lowest byte to collect. The @var{basereg},
39723 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39724 values (the @samp{-1} value for @var{basereg} is a special case).
39726 @item X @var{len},@var{expr}
39727 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39728 it directs. @var{expr} is an agent expression, as described in
39729 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39730 two-digit hex number in the packet; @var{len} is the number of bytes
39731 in the expression (and thus one-half the number of hex digits in the
39736 Any number of actions may be packed together in a single @samp{QTDP}
39737 packet, as long as the packet does not exceed the maximum packet
39738 length (400 bytes, for many stubs). There may be only one @samp{R}
39739 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39740 actions. Any registers referred to by @samp{M} and @samp{X} actions
39741 must be collected by a preceding @samp{R} action. (The
39742 ``while-stepping'' actions are treated as if they were attached to a
39743 separate tracepoint, as far as these restrictions are concerned.)
39748 The packet was understood and carried out.
39750 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39752 The packet was not recognized.
39755 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39756 @cindex @samp{QTDPsrc} packet
39757 Specify a source string of tracepoint @var{n} at address @var{addr}.
39758 This is useful to get accurate reproduction of the tracepoints
39759 originally downloaded at the beginning of the trace run. @var{type}
39760 is the name of the tracepoint part, such as @samp{cond} for the
39761 tracepoint's conditional expression (see below for a list of types), while
39762 @var{bytes} is the string, encoded in hexadecimal.
39764 @var{start} is the offset of the @var{bytes} within the overall source
39765 string, while @var{slen} is the total length of the source string.
39766 This is intended for handling source strings that are longer than will
39767 fit in a single packet.
39768 @c Add detailed example when this info is moved into a dedicated
39769 @c tracepoint descriptions section.
39771 The available string types are @samp{at} for the location,
39772 @samp{cond} for the conditional, and @samp{cmd} for an action command.
39773 @value{GDBN} sends a separate packet for each command in the action
39774 list, in the same order in which the commands are stored in the list.
39776 The target does not need to do anything with source strings except
39777 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
39780 Although this packet is optional, and @value{GDBN} will only send it
39781 if the target replies with @samp{TracepointSource} @xref{General
39782 Query Packets}, it makes both disconnected tracing and trace files
39783 much easier to use. Otherwise the user must be careful that the
39784 tracepoints in effect while looking at trace frames are identical to
39785 the ones in effect during the trace run; even a small discrepancy
39786 could cause @samp{tdump} not to work, or a particular trace frame not
39789 @item QTDV:@var{n}:@var{value}
39790 @cindex define trace state variable, remote request
39791 @cindex @samp{QTDV} packet
39792 Create a new trace state variable, number @var{n}, with an initial
39793 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
39794 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
39795 the option of not using this packet for initial values of zero; the
39796 target should simply create the trace state variables as they are
39797 mentioned in expressions.
39799 @item QTFrame:@var{n}
39800 @cindex @samp{QTFrame} packet
39801 Select the @var{n}'th tracepoint frame from the buffer, and use the
39802 register and memory contents recorded there to answer subsequent
39803 request packets from @value{GDBN}.
39805 A successful reply from the stub indicates that the stub has found the
39806 requested frame. The response is a series of parts, concatenated
39807 without separators, describing the frame we selected. Each part has
39808 one of the following forms:
39812 The selected frame is number @var{n} in the trace frame buffer;
39813 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
39814 was no frame matching the criteria in the request packet.
39817 The selected trace frame records a hit of tracepoint number @var{t};
39818 @var{t} is a hexadecimal number.
39822 @item QTFrame:pc:@var{addr}
39823 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39824 currently selected frame whose PC is @var{addr};
39825 @var{addr} is a hexadecimal number.
39827 @item QTFrame:tdp:@var{t}
39828 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39829 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
39830 is a hexadecimal number.
39832 @item QTFrame:range:@var{start}:@var{end}
39833 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39834 currently selected frame whose PC is between @var{start} (inclusive)
39835 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
39838 @item QTFrame:outside:@var{start}:@var{end}
39839 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
39840 frame @emph{outside} the given range of addresses (exclusive).
39843 @cindex @samp{qTMinFTPILen} packet
39844 This packet requests the minimum length of instruction at which a fast
39845 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
39846 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
39847 it depends on the target system being able to create trampolines in
39848 the first 64K of memory, which might or might not be possible for that
39849 system. So the reply to this packet will be 4 if it is able to
39856 The minimum instruction length is currently unknown.
39858 The minimum instruction length is @var{length}, where @var{length} is greater
39859 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
39860 that a fast tracepoint may be placed on any instruction regardless of size.
39862 An error has occurred.
39864 An empty reply indicates that the request is not supported by the stub.
39868 @cindex @samp{QTStart} packet
39869 Begin the tracepoint experiment. Begin collecting data from
39870 tracepoint hits in the trace frame buffer. This packet supports the
39871 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
39872 instruction reply packet}).
39875 @cindex @samp{QTStop} packet
39876 End the tracepoint experiment. Stop collecting trace frames.
39878 @item QTEnable:@var{n}:@var{addr}
39880 @cindex @samp{QTEnable} packet
39881 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
39882 experiment. If the tracepoint was previously disabled, then collection
39883 of data from it will resume.
39885 @item QTDisable:@var{n}:@var{addr}
39887 @cindex @samp{QTDisable} packet
39888 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
39889 experiment. No more data will be collected from the tracepoint unless
39890 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
39893 @cindex @samp{QTinit} packet
39894 Clear the table of tracepoints, and empty the trace frame buffer.
39896 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
39897 @cindex @samp{QTro} packet
39898 Establish the given ranges of memory as ``transparent''. The stub
39899 will answer requests for these ranges from memory's current contents,
39900 if they were not collected as part of the tracepoint hit.
39902 @value{GDBN} uses this to mark read-only regions of memory, like those
39903 containing program code. Since these areas never change, they should
39904 still have the same contents they did when the tracepoint was hit, so
39905 there's no reason for the stub to refuse to provide their contents.
39907 @item QTDisconnected:@var{value}
39908 @cindex @samp{QTDisconnected} packet
39909 Set the choice to what to do with the tracing run when @value{GDBN}
39910 disconnects from the target. A @var{value} of 1 directs the target to
39911 continue the tracing run, while 0 tells the target to stop tracing if
39912 @value{GDBN} is no longer in the picture.
39915 @cindex @samp{qTStatus} packet
39916 Ask the stub if there is a trace experiment running right now.
39918 The reply has the form:
39922 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
39923 @var{running} is a single digit @code{1} if the trace is presently
39924 running, or @code{0} if not. It is followed by semicolon-separated
39925 optional fields that an agent may use to report additional status.
39929 If the trace is not running, the agent may report any of several
39930 explanations as one of the optional fields:
39935 No trace has been run yet.
39937 @item tstop[:@var{text}]:0
39938 The trace was stopped by a user-originated stop command. The optional
39939 @var{text} field is a user-supplied string supplied as part of the
39940 stop command (for instance, an explanation of why the trace was
39941 stopped manually). It is hex-encoded.
39944 The trace stopped because the trace buffer filled up.
39946 @item tdisconnected:0
39947 The trace stopped because @value{GDBN} disconnected from the target.
39949 @item tpasscount:@var{tpnum}
39950 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39952 @item terror:@var{text}:@var{tpnum}
39953 The trace stopped because tracepoint @var{tpnum} had an error. The
39954 string @var{text} is available to describe the nature of the error
39955 (for instance, a divide by zero in the condition expression).
39956 @var{text} is hex encoded.
39959 The trace stopped for some other reason.
39963 Additional optional fields supply statistical and other information.
39964 Although not required, they are extremely useful for users monitoring
39965 the progress of a trace run. If a trace has stopped, and these
39966 numbers are reported, they must reflect the state of the just-stopped
39971 @item tframes:@var{n}
39972 The number of trace frames in the buffer.
39974 @item tcreated:@var{n}
39975 The total number of trace frames created during the run. This may
39976 be larger than the trace frame count, if the buffer is circular.
39978 @item tsize:@var{n}
39979 The total size of the trace buffer, in bytes.
39981 @item tfree:@var{n}
39982 The number of bytes still unused in the buffer.
39984 @item circular:@var{n}
39985 The value of the circular trace buffer flag. @code{1} means that the
39986 trace buffer is circular and old trace frames will be discarded if
39987 necessary to make room, @code{0} means that the trace buffer is linear
39990 @item disconn:@var{n}
39991 The value of the disconnected tracing flag. @code{1} means that
39992 tracing will continue after @value{GDBN} disconnects, @code{0} means
39993 that the trace run will stop.
39997 @item qTP:@var{tp}:@var{addr}
39998 @cindex tracepoint status, remote request
39999 @cindex @samp{qTP} packet
40000 Ask the stub for the current state of tracepoint number @var{tp} at
40001 address @var{addr}.
40005 @item V@var{hits}:@var{usage}
40006 The tracepoint has been hit @var{hits} times so far during the trace
40007 run, and accounts for @var{usage} in the trace buffer. Note that
40008 @code{while-stepping} steps are not counted as separate hits, but the
40009 steps' space consumption is added into the usage number.
40013 @item qTV:@var{var}
40014 @cindex trace state variable value, remote request
40015 @cindex @samp{qTV} packet
40016 Ask the stub for the value of the trace state variable number @var{var}.
40021 The value of the variable is @var{value}. This will be the current
40022 value of the variable if the user is examining a running target, or a
40023 saved value if the variable was collected in the trace frame that the
40024 user is looking at. Note that multiple requests may result in
40025 different reply values, such as when requesting values while the
40026 program is running.
40029 The value of the variable is unknown. This would occur, for example,
40030 if the user is examining a trace frame in which the requested variable
40035 @cindex @samp{qTfP} packet
40037 @cindex @samp{qTsP} packet
40038 These packets request data about tracepoints that are being used by
40039 the target. @value{GDBN} sends @code{qTfP} to get the first piece
40040 of data, and multiple @code{qTsP} to get additional pieces. Replies
40041 to these packets generally take the form of the @code{QTDP} packets
40042 that define tracepoints. (FIXME add detailed syntax)
40045 @cindex @samp{qTfV} packet
40047 @cindex @samp{qTsV} packet
40048 These packets request data about trace state variables that are on the
40049 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
40050 and multiple @code{qTsV} to get additional variables. Replies to
40051 these packets follow the syntax of the @code{QTDV} packets that define
40052 trace state variables.
40058 @cindex @samp{qTfSTM} packet
40059 @cindex @samp{qTsSTM} packet
40060 These packets request data about static tracepoint markers that exist
40061 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
40062 first piece of data, and multiple @code{qTsSTM} to get additional
40063 pieces. Replies to these packets take the following form:
40067 @item m @var{address}:@var{id}:@var{extra}
40069 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
40070 a comma-separated list of markers
40072 (lower case letter @samp{L}) denotes end of list.
40074 An error occurred. @var{nn} are hex digits.
40076 An empty reply indicates that the request is not supported by the
40080 @var{address} is encoded in hex.
40081 @var{id} and @var{extra} are strings encoded in hex.
40083 In response to each query, the target will reply with a list of one or
40084 more markers, separated by commas. @value{GDBN} will respond to each
40085 reply with a request for more markers (using the @samp{qs} form of the
40086 query), until the target responds with @samp{l} (lower-case ell, for
40089 @item qTSTMat:@var{address}
40091 @cindex @samp{qTSTMat} packet
40092 This packets requests data about static tracepoint markers in the
40093 target program at @var{address}. Replies to this packet follow the
40094 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40095 tracepoint markers.
40097 @item QTSave:@var{filename}
40098 @cindex @samp{QTSave} packet
40099 This packet directs the target to save trace data to the file name
40100 @var{filename} in the target's filesystem. @var{filename} is encoded
40101 as a hex string; the interpretation of the file name (relative vs
40102 absolute, wild cards, etc) is up to the target.
40104 @item qTBuffer:@var{offset},@var{len}
40105 @cindex @samp{qTBuffer} packet
40106 Return up to @var{len} bytes of the current contents of trace buffer,
40107 starting at @var{offset}. The trace buffer is treated as if it were
40108 a contiguous collection of traceframes, as per the trace file format.
40109 The reply consists as many hex-encoded bytes as the target can deliver
40110 in a packet; it is not an error to return fewer than were asked for.
40111 A reply consisting of just @code{l} indicates that no bytes are
40114 @item QTBuffer:circular:@var{value}
40115 This packet directs the target to use a circular trace buffer if
40116 @var{value} is 1, or a linear buffer if the value is 0.
40118 @item QTBuffer:size:@var{size}
40119 @anchor{QTBuffer-size}
40120 @cindex @samp{QTBuffer size} packet
40121 This packet directs the target to make the trace buffer be of size
40122 @var{size} if possible. A value of @code{-1} tells the target to
40123 use whatever size it prefers.
40125 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40126 @cindex @samp{QTNotes} packet
40127 This packet adds optional textual notes to the trace run. Allowable
40128 types include @code{user}, @code{notes}, and @code{tstop}, the
40129 @var{text} fields are arbitrary strings, hex-encoded.
40133 @subsection Relocate instruction reply packet
40134 When installing fast tracepoints in memory, the target may need to
40135 relocate the instruction currently at the tracepoint address to a
40136 different address in memory. For most instructions, a simple copy is
40137 enough, but, for example, call instructions that implicitly push the
40138 return address on the stack, and relative branches or other
40139 PC-relative instructions require offset adjustment, so that the effect
40140 of executing the instruction at a different address is the same as if
40141 it had executed in the original location.
40143 In response to several of the tracepoint packets, the target may also
40144 respond with a number of intermediate @samp{qRelocInsn} request
40145 packets before the final result packet, to have @value{GDBN} handle
40146 this relocation operation. If a packet supports this mechanism, its
40147 documentation will explicitly say so. See for example the above
40148 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40149 format of the request is:
40152 @item qRelocInsn:@var{from};@var{to}
40154 This requests @value{GDBN} to copy instruction at address @var{from}
40155 to address @var{to}, possibly adjusted so that executing the
40156 instruction at @var{to} has the same effect as executing it at
40157 @var{from}. @value{GDBN} writes the adjusted instruction to target
40158 memory starting at @var{to}.
40163 @item qRelocInsn:@var{adjusted_size}
40164 Informs the stub the relocation is complete. @var{adjusted_size} is
40165 the length in bytes of resulting relocated instruction sequence.
40167 A badly formed request was detected, or an error was encountered while
40168 relocating the instruction.
40171 @node Host I/O Packets
40172 @section Host I/O Packets
40173 @cindex Host I/O, remote protocol
40174 @cindex file transfer, remote protocol
40176 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40177 operations on the far side of a remote link. For example, Host I/O is
40178 used to upload and download files to a remote target with its own
40179 filesystem. Host I/O uses the same constant values and data structure
40180 layout as the target-initiated File-I/O protocol. However, the
40181 Host I/O packets are structured differently. The target-initiated
40182 protocol relies on target memory to store parameters and buffers.
40183 Host I/O requests are initiated by @value{GDBN}, and the
40184 target's memory is not involved. @xref{File-I/O Remote Protocol
40185 Extension}, for more details on the target-initiated protocol.
40187 The Host I/O request packets all encode a single operation along with
40188 its arguments. They have this format:
40192 @item vFile:@var{operation}: @var{parameter}@dots{}
40193 @var{operation} is the name of the particular request; the target
40194 should compare the entire packet name up to the second colon when checking
40195 for a supported operation. The format of @var{parameter} depends on
40196 the operation. Numbers are always passed in hexadecimal. Negative
40197 numbers have an explicit minus sign (i.e.@: two's complement is not
40198 used). Strings (e.g.@: filenames) are encoded as a series of
40199 hexadecimal bytes. The last argument to a system call may be a
40200 buffer of escaped binary data (@pxref{Binary Data}).
40204 The valid responses to Host I/O packets are:
40208 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40209 @var{result} is the integer value returned by this operation, usually
40210 non-negative for success and -1 for errors. If an error has occured,
40211 @var{errno} will be included in the result. @var{errno} will have a
40212 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40213 operations which return data, @var{attachment} supplies the data as a
40214 binary buffer. Binary buffers in response packets are escaped in the
40215 normal way (@pxref{Binary Data}). See the individual packet
40216 documentation for the interpretation of @var{result} and
40220 An empty response indicates that this operation is not recognized.
40224 These are the supported Host I/O operations:
40227 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40228 Open a file at @var{pathname} and return a file descriptor for it, or
40229 return -1 if an error occurs. @var{pathname} is a string,
40230 @var{flags} is an integer indicating a mask of open flags
40231 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40232 of mode bits to use if the file is created (@pxref{mode_t Values}).
40233 @xref{open}, for details of the open flags and mode values.
40235 @item vFile:close: @var{fd}
40236 Close the open file corresponding to @var{fd} and return 0, or
40237 -1 if an error occurs.
40239 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40240 Read data from the open file corresponding to @var{fd}. Up to
40241 @var{count} bytes will be read from the file, starting at @var{offset}
40242 relative to the start of the file. The target may read fewer bytes;
40243 common reasons include packet size limits and an end-of-file
40244 condition. The number of bytes read is returned. Zero should only be
40245 returned for a successful read at the end of the file, or if
40246 @var{count} was zero.
40248 The data read should be returned as a binary attachment on success.
40249 If zero bytes were read, the response should include an empty binary
40250 attachment (i.e.@: a trailing semicolon). The return value is the
40251 number of target bytes read; the binary attachment may be longer if
40252 some characters were escaped.
40254 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40255 Write @var{data} (a binary buffer) to the open file corresponding
40256 to @var{fd}. Start the write at @var{offset} from the start of the
40257 file. Unlike many @code{write} system calls, there is no
40258 separate @var{count} argument; the length of @var{data} in the
40259 packet is used. @samp{vFile:write} returns the number of bytes written,
40260 which may be shorter than the length of @var{data}, or -1 if an
40263 @item vFile:unlink: @var{pathname}
40264 Delete the file at @var{pathname} on the target. Return 0,
40265 or -1 if an error occurs. @var{pathname} is a string.
40267 @item vFile:readlink: @var{filename}
40268 Read value of symbolic link @var{filename} on the target. Return
40269 the number of bytes read, or -1 if an error occurs.
40271 The data read should be returned as a binary attachment on success.
40272 If zero bytes were read, the response should include an empty binary
40273 attachment (i.e.@: a trailing semicolon). The return value is the
40274 number of target bytes read; the binary attachment may be longer if
40275 some characters were escaped.
40280 @section Interrupts
40281 @cindex interrupts (remote protocol)
40283 When a program on the remote target is running, @value{GDBN} may
40284 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40285 a @code{BREAK} followed by @code{g},
40286 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40288 The precise meaning of @code{BREAK} is defined by the transport
40289 mechanism and may, in fact, be undefined. @value{GDBN} does not
40290 currently define a @code{BREAK} mechanism for any of the network
40291 interfaces except for TCP, in which case @value{GDBN} sends the
40292 @code{telnet} BREAK sequence.
40294 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40295 transport mechanisms. It is represented by sending the single byte
40296 @code{0x03} without any of the usual packet overhead described in
40297 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40298 transmitted as part of a packet, it is considered to be packet data
40299 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40300 (@pxref{X packet}), used for binary downloads, may include an unescaped
40301 @code{0x03} as part of its packet.
40303 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40304 When Linux kernel receives this sequence from serial port,
40305 it stops execution and connects to gdb.
40307 Stubs are not required to recognize these interrupt mechanisms and the
40308 precise meaning associated with receipt of the interrupt is
40309 implementation defined. If the target supports debugging of multiple
40310 threads and/or processes, it should attempt to interrupt all
40311 currently-executing threads and processes.
40312 If the stub is successful at interrupting the
40313 running program, it should send one of the stop
40314 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40315 of successfully stopping the program in all-stop mode, and a stop reply
40316 for each stopped thread in non-stop mode.
40317 Interrupts received while the
40318 program is stopped are discarded.
40320 @node Notification Packets
40321 @section Notification Packets
40322 @cindex notification packets
40323 @cindex packets, notification
40325 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40326 packets that require no acknowledgment. Both the GDB and the stub
40327 may send notifications (although the only notifications defined at
40328 present are sent by the stub). Notifications carry information
40329 without incurring the round-trip latency of an acknowledgment, and so
40330 are useful for low-impact communications where occasional packet loss
40333 A notification packet has the form @samp{% @var{data} #
40334 @var{checksum}}, where @var{data} is the content of the notification,
40335 and @var{checksum} is a checksum of @var{data}, computed and formatted
40336 as for ordinary @value{GDBN} packets. A notification's @var{data}
40337 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40338 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40339 to acknowledge the notification's receipt or to report its corruption.
40341 Every notification's @var{data} begins with a name, which contains no
40342 colon characters, followed by a colon character.
40344 Recipients should silently ignore corrupted notifications and
40345 notifications they do not understand. Recipients should restart
40346 timeout periods on receipt of a well-formed notification, whether or
40347 not they understand it.
40349 Senders should only send the notifications described here when this
40350 protocol description specifies that they are permitted. In the
40351 future, we may extend the protocol to permit existing notifications in
40352 new contexts; this rule helps older senders avoid confusing newer
40355 (Older versions of @value{GDBN} ignore bytes received until they see
40356 the @samp{$} byte that begins an ordinary packet, so new stubs may
40357 transmit notifications without fear of confusing older clients. There
40358 are no notifications defined for @value{GDBN} to send at the moment, but we
40359 assume that most older stubs would ignore them, as well.)
40361 Each notification is comprised of three parts:
40363 @item @var{name}:@var{event}
40364 The notification packet is sent by the side that initiates the
40365 exchange (currently, only the stub does that), with @var{event}
40366 carrying the specific information about the notification.
40367 @var{name} is the name of the notification.
40369 The acknowledge sent by the other side, usually @value{GDBN}, to
40370 acknowledge the exchange and request the event.
40373 The purpose of an asynchronous notification mechanism is to report to
40374 @value{GDBN} that something interesting happened in the remote stub.
40376 The remote stub may send notification @var{name}:@var{event}
40377 at any time, but @value{GDBN} acknowledges the notification when
40378 appropriate. The notification event is pending before @value{GDBN}
40379 acknowledges. Only one notification at a time may be pending; if
40380 additional events occur before @value{GDBN} has acknowledged the
40381 previous notification, they must be queued by the stub for later
40382 synchronous transmission in response to @var{ack} packets from
40383 @value{GDBN}. Because the notification mechanism is unreliable,
40384 the stub is permitted to resend a notification if it believes
40385 @value{GDBN} may not have received it.
40387 Specifically, notifications may appear when @value{GDBN} is not
40388 otherwise reading input from the stub, or when @value{GDBN} is
40389 expecting to read a normal synchronous response or a
40390 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40391 Notification packets are distinct from any other communication from
40392 the stub so there is no ambiguity.
40394 After receiving a notification, @value{GDBN} shall acknowledge it by
40395 sending a @var{ack} packet as a regular, synchronous request to the
40396 stub. Such acknowledgment is not required to happen immediately, as
40397 @value{GDBN} is permitted to send other, unrelated packets to the
40398 stub first, which the stub should process normally.
40400 Upon receiving a @var{ack} packet, if the stub has other queued
40401 events to report to @value{GDBN}, it shall respond by sending a
40402 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40403 packet to solicit further responses; again, it is permitted to send
40404 other, unrelated packets as well which the stub should process
40407 If the stub receives a @var{ack} packet and there are no additional
40408 @var{event} to report, the stub shall return an @samp{OK} response.
40409 At this point, @value{GDBN} has finished processing a notification
40410 and the stub has completed sending any queued events. @value{GDBN}
40411 won't accept any new notifications until the final @samp{OK} is
40412 received . If further notification events occur, the stub shall send
40413 a new notification, @value{GDBN} shall accept the notification, and
40414 the process shall be repeated.
40416 The process of asynchronous notification can be illustrated by the
40419 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40422 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40424 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40429 The following notifications are defined:
40430 @multitable @columnfractions 0.12 0.12 0.38 0.38
40439 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40440 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40441 for information on how these notifications are acknowledged by
40443 @tab Report an asynchronous stop event in non-stop mode.
40447 @node Remote Non-Stop
40448 @section Remote Protocol Support for Non-Stop Mode
40450 @value{GDBN}'s remote protocol supports non-stop debugging of
40451 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40452 supports non-stop mode, it should report that to @value{GDBN} by including
40453 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40455 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40456 establishing a new connection with the stub. Entering non-stop mode
40457 does not alter the state of any currently-running threads, but targets
40458 must stop all threads in any already-attached processes when entering
40459 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40460 probe the target state after a mode change.
40462 In non-stop mode, when an attached process encounters an event that
40463 would otherwise be reported with a stop reply, it uses the
40464 asynchronous notification mechanism (@pxref{Notification Packets}) to
40465 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40466 in all processes are stopped when a stop reply is sent, in non-stop
40467 mode only the thread reporting the stop event is stopped. That is,
40468 when reporting a @samp{S} or @samp{T} response to indicate completion
40469 of a step operation, hitting a breakpoint, or a fault, only the
40470 affected thread is stopped; any other still-running threads continue
40471 to run. When reporting a @samp{W} or @samp{X} response, all running
40472 threads belonging to other attached processes continue to run.
40474 In non-stop mode, the target shall respond to the @samp{?} packet as
40475 follows. First, any incomplete stop reply notification/@samp{vStopped}
40476 sequence in progress is abandoned. The target must begin a new
40477 sequence reporting stop events for all stopped threads, whether or not
40478 it has previously reported those events to @value{GDBN}. The first
40479 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40480 subsequent stop replies are sent as responses to @samp{vStopped} packets
40481 using the mechanism described above. The target must not send
40482 asynchronous stop reply notifications until the sequence is complete.
40483 If all threads are running when the target receives the @samp{?} packet,
40484 or if the target is not attached to any process, it shall respond
40487 @node Packet Acknowledgment
40488 @section Packet Acknowledgment
40490 @cindex acknowledgment, for @value{GDBN} remote
40491 @cindex packet acknowledgment, for @value{GDBN} remote
40492 By default, when either the host or the target machine receives a packet,
40493 the first response expected is an acknowledgment: either @samp{+} (to indicate
40494 the package was received correctly) or @samp{-} (to request retransmission).
40495 This mechanism allows the @value{GDBN} remote protocol to operate over
40496 unreliable transport mechanisms, such as a serial line.
40498 In cases where the transport mechanism is itself reliable (such as a pipe or
40499 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40500 It may be desirable to disable them in that case to reduce communication
40501 overhead, or for other reasons. This can be accomplished by means of the
40502 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40504 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40505 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40506 and response format still includes the normal checksum, as described in
40507 @ref{Overview}, but the checksum may be ignored by the receiver.
40509 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40510 no-acknowledgment mode, it should report that to @value{GDBN}
40511 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40512 @pxref{qSupported}.
40513 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40514 disabled via the @code{set remote noack-packet off} command
40515 (@pxref{Remote Configuration}),
40516 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40517 Only then may the stub actually turn off packet acknowledgments.
40518 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40519 response, which can be safely ignored by the stub.
40521 Note that @code{set remote noack-packet} command only affects negotiation
40522 between @value{GDBN} and the stub when subsequent connections are made;
40523 it does not affect the protocol acknowledgment state for any current
40525 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
40526 new connection is established,
40527 there is also no protocol request to re-enable the acknowledgments
40528 for the current connection, once disabled.
40533 Example sequence of a target being re-started. Notice how the restart
40534 does not get any direct output:
40539 @emph{target restarts}
40542 <- @code{T001:1234123412341234}
40546 Example sequence of a target being stepped by a single instruction:
40549 -> @code{G1445@dots{}}
40554 <- @code{T001:1234123412341234}
40558 <- @code{1455@dots{}}
40562 @node File-I/O Remote Protocol Extension
40563 @section File-I/O Remote Protocol Extension
40564 @cindex File-I/O remote protocol extension
40567 * File-I/O Overview::
40568 * Protocol Basics::
40569 * The F Request Packet::
40570 * The F Reply Packet::
40571 * The Ctrl-C Message::
40573 * List of Supported Calls::
40574 * Protocol-specific Representation of Datatypes::
40576 * File-I/O Examples::
40579 @node File-I/O Overview
40580 @subsection File-I/O Overview
40581 @cindex file-i/o overview
40583 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
40584 target to use the host's file system and console I/O to perform various
40585 system calls. System calls on the target system are translated into a
40586 remote protocol packet to the host system, which then performs the needed
40587 actions and returns a response packet to the target system.
40588 This simulates file system operations even on targets that lack file systems.
40590 The protocol is defined to be independent of both the host and target systems.
40591 It uses its own internal representation of datatypes and values. Both
40592 @value{GDBN} and the target's @value{GDBN} stub are responsible for
40593 translating the system-dependent value representations into the internal
40594 protocol representations when data is transmitted.
40596 The communication is synchronous. A system call is possible only when
40597 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
40598 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
40599 the target is stopped to allow deterministic access to the target's
40600 memory. Therefore File-I/O is not interruptible by target signals. On
40601 the other hand, it is possible to interrupt File-I/O by a user interrupt
40602 (@samp{Ctrl-C}) within @value{GDBN}.
40604 The target's request to perform a host system call does not finish
40605 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
40606 after finishing the system call, the target returns to continuing the
40607 previous activity (continue, step). No additional continue or step
40608 request from @value{GDBN} is required.
40611 (@value{GDBP}) continue
40612 <- target requests 'system call X'
40613 target is stopped, @value{GDBN} executes system call
40614 -> @value{GDBN} returns result
40615 ... target continues, @value{GDBN} returns to wait for the target
40616 <- target hits breakpoint and sends a Txx packet
40619 The protocol only supports I/O on the console and to regular files on
40620 the host file system. Character or block special devices, pipes,
40621 named pipes, sockets or any other communication method on the host
40622 system are not supported by this protocol.
40624 File I/O is not supported in non-stop mode.
40626 @node Protocol Basics
40627 @subsection Protocol Basics
40628 @cindex protocol basics, file-i/o
40630 The File-I/O protocol uses the @code{F} packet as the request as well
40631 as reply packet. Since a File-I/O system call can only occur when
40632 @value{GDBN} is waiting for a response from the continuing or stepping target,
40633 the File-I/O request is a reply that @value{GDBN} has to expect as a result
40634 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
40635 This @code{F} packet contains all information needed to allow @value{GDBN}
40636 to call the appropriate host system call:
40640 A unique identifier for the requested system call.
40643 All parameters to the system call. Pointers are given as addresses
40644 in the target memory address space. Pointers to strings are given as
40645 pointer/length pair. Numerical values are given as they are.
40646 Numerical control flags are given in a protocol-specific representation.
40650 At this point, @value{GDBN} has to perform the following actions.
40654 If the parameters include pointer values to data needed as input to a
40655 system call, @value{GDBN} requests this data from the target with a
40656 standard @code{m} packet request. This additional communication has to be
40657 expected by the target implementation and is handled as any other @code{m}
40661 @value{GDBN} translates all value from protocol representation to host
40662 representation as needed. Datatypes are coerced into the host types.
40665 @value{GDBN} calls the system call.
40668 It then coerces datatypes back to protocol representation.
40671 If the system call is expected to return data in buffer space specified
40672 by pointer parameters to the call, the data is transmitted to the
40673 target using a @code{M} or @code{X} packet. This packet has to be expected
40674 by the target implementation and is handled as any other @code{M} or @code{X}
40679 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40680 necessary information for the target to continue. This at least contains
40687 @code{errno}, if has been changed by the system call.
40694 After having done the needed type and value coercion, the target continues
40695 the latest continue or step action.
40697 @node The F Request Packet
40698 @subsection The @code{F} Request Packet
40699 @cindex file-i/o request packet
40700 @cindex @code{F} request packet
40702 The @code{F} request packet has the following format:
40705 @item F@var{call-id},@var{parameter@dots{}}
40707 @var{call-id} is the identifier to indicate the host system call to be called.
40708 This is just the name of the function.
40710 @var{parameter@dots{}} are the parameters to the system call.
40711 Parameters are hexadecimal integer values, either the actual values in case
40712 of scalar datatypes, pointers to target buffer space in case of compound
40713 datatypes and unspecified memory areas, or pointer/length pairs in case
40714 of string parameters. These are appended to the @var{call-id} as a
40715 comma-delimited list. All values are transmitted in ASCII
40716 string representation, pointer/length pairs separated by a slash.
40722 @node The F Reply Packet
40723 @subsection The @code{F} Reply Packet
40724 @cindex file-i/o reply packet
40725 @cindex @code{F} reply packet
40727 The @code{F} reply packet has the following format:
40731 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
40733 @var{retcode} is the return code of the system call as hexadecimal value.
40735 @var{errno} is the @code{errno} set by the call, in protocol-specific
40737 This parameter can be omitted if the call was successful.
40739 @var{Ctrl-C flag} is only sent if the user requested a break. In this
40740 case, @var{errno} must be sent as well, even if the call was successful.
40741 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
40748 or, if the call was interrupted before the host call has been performed:
40755 assuming 4 is the protocol-specific representation of @code{EINTR}.
40760 @node The Ctrl-C Message
40761 @subsection The @samp{Ctrl-C} Message
40762 @cindex ctrl-c message, in file-i/o protocol
40764 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
40765 reply packet (@pxref{The F Reply Packet}),
40766 the target should behave as if it had
40767 gotten a break message. The meaning for the target is ``system call
40768 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
40769 (as with a break message) and return to @value{GDBN} with a @code{T02}
40772 It's important for the target to know in which
40773 state the system call was interrupted. There are two possible cases:
40777 The system call hasn't been performed on the host yet.
40780 The system call on the host has been finished.
40784 These two states can be distinguished by the target by the value of the
40785 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40786 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40787 on POSIX systems. In any other case, the target may presume that the
40788 system call has been finished --- successfully or not --- and should behave
40789 as if the break message arrived right after the system call.
40791 @value{GDBN} must behave reliably. If the system call has not been called
40792 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40793 @code{errno} in the packet. If the system call on the host has been finished
40794 before the user requests a break, the full action must be finished by
40795 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40796 The @code{F} packet may only be sent when either nothing has happened
40797 or the full action has been completed.
40800 @subsection Console I/O
40801 @cindex console i/o as part of file-i/o
40803 By default and if not explicitly closed by the target system, the file
40804 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
40805 on the @value{GDBN} console is handled as any other file output operation
40806 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
40807 by @value{GDBN} so that after the target read request from file descriptor
40808 0 all following typing is buffered until either one of the following
40813 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
40815 system call is treated as finished.
40818 The user presses @key{RET}. This is treated as end of input with a trailing
40822 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
40823 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
40827 If the user has typed more characters than fit in the buffer given to
40828 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
40829 either another @code{read(0, @dots{})} is requested by the target, or debugging
40830 is stopped at the user's request.
40833 @node List of Supported Calls
40834 @subsection List of Supported Calls
40835 @cindex list of supported file-i/o calls
40852 @unnumberedsubsubsec open
40853 @cindex open, file-i/o system call
40858 int open(const char *pathname, int flags);
40859 int open(const char *pathname, int flags, mode_t mode);
40863 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
40866 @var{flags} is the bitwise @code{OR} of the following values:
40870 If the file does not exist it will be created. The host
40871 rules apply as far as file ownership and time stamps
40875 When used with @code{O_CREAT}, if the file already exists it is
40876 an error and open() fails.
40879 If the file already exists and the open mode allows
40880 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
40881 truncated to zero length.
40884 The file is opened in append mode.
40887 The file is opened for reading only.
40890 The file is opened for writing only.
40893 The file is opened for reading and writing.
40897 Other bits are silently ignored.
40901 @var{mode} is the bitwise @code{OR} of the following values:
40905 User has read permission.
40908 User has write permission.
40911 Group has read permission.
40914 Group has write permission.
40917 Others have read permission.
40920 Others have write permission.
40924 Other bits are silently ignored.
40927 @item Return value:
40928 @code{open} returns the new file descriptor or -1 if an error
40935 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40938 @var{pathname} refers to a directory.
40941 The requested access is not allowed.
40944 @var{pathname} was too long.
40947 A directory component in @var{pathname} does not exist.
40950 @var{pathname} refers to a device, pipe, named pipe or socket.
40953 @var{pathname} refers to a file on a read-only filesystem and
40954 write access was requested.
40957 @var{pathname} is an invalid pointer value.
40960 No space on device to create the file.
40963 The process already has the maximum number of files open.
40966 The limit on the total number of files open on the system
40970 The call was interrupted by the user.
40976 @unnumberedsubsubsec close
40977 @cindex close, file-i/o system call
40986 @samp{Fclose,@var{fd}}
40988 @item Return value:
40989 @code{close} returns zero on success, or -1 if an error occurred.
40995 @var{fd} isn't a valid open file descriptor.
40998 The call was interrupted by the user.
41004 @unnumberedsubsubsec read
41005 @cindex read, file-i/o system call
41010 int read(int fd, void *buf, unsigned int count);
41014 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
41016 @item Return value:
41017 On success, the number of bytes read is returned.
41018 Zero indicates end of file. If count is zero, read
41019 returns zero as well. On error, -1 is returned.
41025 @var{fd} is not a valid file descriptor or is not open for
41029 @var{bufptr} is an invalid pointer value.
41032 The call was interrupted by the user.
41038 @unnumberedsubsubsec write
41039 @cindex write, file-i/o system call
41044 int write(int fd, const void *buf, unsigned int count);
41048 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
41050 @item Return value:
41051 On success, the number of bytes written are returned.
41052 Zero indicates nothing was written. On error, -1
41059 @var{fd} is not a valid file descriptor or is not open for
41063 @var{bufptr} is an invalid pointer value.
41066 An attempt was made to write a file that exceeds the
41067 host-specific maximum file size allowed.
41070 No space on device to write the data.
41073 The call was interrupted by the user.
41079 @unnumberedsubsubsec lseek
41080 @cindex lseek, file-i/o system call
41085 long lseek (int fd, long offset, int flag);
41089 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
41091 @var{flag} is one of:
41095 The offset is set to @var{offset} bytes.
41098 The offset is set to its current location plus @var{offset}
41102 The offset is set to the size of the file plus @var{offset}
41106 @item Return value:
41107 On success, the resulting unsigned offset in bytes from
41108 the beginning of the file is returned. Otherwise, a
41109 value of -1 is returned.
41115 @var{fd} is not a valid open file descriptor.
41118 @var{fd} is associated with the @value{GDBN} console.
41121 @var{flag} is not a proper value.
41124 The call was interrupted by the user.
41130 @unnumberedsubsubsec rename
41131 @cindex rename, file-i/o system call
41136 int rename(const char *oldpath, const char *newpath);
41140 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41142 @item Return value:
41143 On success, zero is returned. On error, -1 is returned.
41149 @var{newpath} is an existing directory, but @var{oldpath} is not a
41153 @var{newpath} is a non-empty directory.
41156 @var{oldpath} or @var{newpath} is a directory that is in use by some
41160 An attempt was made to make a directory a subdirectory
41164 A component used as a directory in @var{oldpath} or new
41165 path is not a directory. Or @var{oldpath} is a directory
41166 and @var{newpath} exists but is not a directory.
41169 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41172 No access to the file or the path of the file.
41176 @var{oldpath} or @var{newpath} was too long.
41179 A directory component in @var{oldpath} or @var{newpath} does not exist.
41182 The file is on a read-only filesystem.
41185 The device containing the file has no room for the new
41189 The call was interrupted by the user.
41195 @unnumberedsubsubsec unlink
41196 @cindex unlink, file-i/o system call
41201 int unlink(const char *pathname);
41205 @samp{Funlink,@var{pathnameptr}/@var{len}}
41207 @item Return value:
41208 On success, zero is returned. On error, -1 is returned.
41214 No access to the file or the path of the file.
41217 The system does not allow unlinking of directories.
41220 The file @var{pathname} cannot be unlinked because it's
41221 being used by another process.
41224 @var{pathnameptr} is an invalid pointer value.
41227 @var{pathname} was too long.
41230 A directory component in @var{pathname} does not exist.
41233 A component of the path is not a directory.
41236 The file is on a read-only filesystem.
41239 The call was interrupted by the user.
41245 @unnumberedsubsubsec stat/fstat
41246 @cindex fstat, file-i/o system call
41247 @cindex stat, file-i/o system call
41252 int stat(const char *pathname, struct stat *buf);
41253 int fstat(int fd, struct stat *buf);
41257 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41258 @samp{Ffstat,@var{fd},@var{bufptr}}
41260 @item Return value:
41261 On success, zero is returned. On error, -1 is returned.
41267 @var{fd} is not a valid open file.
41270 A directory component in @var{pathname} does not exist or the
41271 path is an empty string.
41274 A component of the path is not a directory.
41277 @var{pathnameptr} is an invalid pointer value.
41280 No access to the file or the path of the file.
41283 @var{pathname} was too long.
41286 The call was interrupted by the user.
41292 @unnumberedsubsubsec gettimeofday
41293 @cindex gettimeofday, file-i/o system call
41298 int gettimeofday(struct timeval *tv, void *tz);
41302 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41304 @item Return value:
41305 On success, 0 is returned, -1 otherwise.
41311 @var{tz} is a non-NULL pointer.
41314 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41320 @unnumberedsubsubsec isatty
41321 @cindex isatty, file-i/o system call
41326 int isatty(int fd);
41330 @samp{Fisatty,@var{fd}}
41332 @item Return value:
41333 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41339 The call was interrupted by the user.
41344 Note that the @code{isatty} call is treated as a special case: it returns
41345 1 to the target if the file descriptor is attached
41346 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41347 would require implementing @code{ioctl} and would be more complex than
41352 @unnumberedsubsubsec system
41353 @cindex system, file-i/o system call
41358 int system(const char *command);
41362 @samp{Fsystem,@var{commandptr}/@var{len}}
41364 @item Return value:
41365 If @var{len} is zero, the return value indicates whether a shell is
41366 available. A zero return value indicates a shell is not available.
41367 For non-zero @var{len}, the value returned is -1 on error and the
41368 return status of the command otherwise. Only the exit status of the
41369 command is returned, which is extracted from the host's @code{system}
41370 return value by calling @code{WEXITSTATUS(retval)}. In case
41371 @file{/bin/sh} could not be executed, 127 is returned.
41377 The call was interrupted by the user.
41382 @value{GDBN} takes over the full task of calling the necessary host calls
41383 to perform the @code{system} call. The return value of @code{system} on
41384 the host is simplified before it's returned
41385 to the target. Any termination signal information from the child process
41386 is discarded, and the return value consists
41387 entirely of the exit status of the called command.
41389 Due to security concerns, the @code{system} call is by default refused
41390 by @value{GDBN}. The user has to allow this call explicitly with the
41391 @code{set remote system-call-allowed 1} command.
41394 @item set remote system-call-allowed
41395 @kindex set remote system-call-allowed
41396 Control whether to allow the @code{system} calls in the File I/O
41397 protocol for the remote target. The default is zero (disabled).
41399 @item show remote system-call-allowed
41400 @kindex show remote system-call-allowed
41401 Show whether the @code{system} calls are allowed in the File I/O
41405 @node Protocol-specific Representation of Datatypes
41406 @subsection Protocol-specific Representation of Datatypes
41407 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41410 * Integral Datatypes::
41412 * Memory Transfer::
41417 @node Integral Datatypes
41418 @unnumberedsubsubsec Integral Datatypes
41419 @cindex integral datatypes, in file-i/o protocol
41421 The integral datatypes used in the system calls are @code{int},
41422 @code{unsigned int}, @code{long}, @code{unsigned long},
41423 @code{mode_t}, and @code{time_t}.
41425 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41426 implemented as 32 bit values in this protocol.
41428 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41430 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41431 in @file{limits.h}) to allow range checking on host and target.
41433 @code{time_t} datatypes are defined as seconds since the Epoch.
41435 All integral datatypes transferred as part of a memory read or write of a
41436 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41439 @node Pointer Values
41440 @unnumberedsubsubsec Pointer Values
41441 @cindex pointer values, in file-i/o protocol
41443 Pointers to target data are transmitted as they are. An exception
41444 is made for pointers to buffers for which the length isn't
41445 transmitted as part of the function call, namely strings. Strings
41446 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41453 which is a pointer to data of length 18 bytes at position 0x1aaf.
41454 The length is defined as the full string length in bytes, including
41455 the trailing null byte. For example, the string @code{"hello world"}
41456 at address 0x123456 is transmitted as
41462 @node Memory Transfer
41463 @unnumberedsubsubsec Memory Transfer
41464 @cindex memory transfer, in file-i/o protocol
41466 Structured data which is transferred using a memory read or write (for
41467 example, a @code{struct stat}) is expected to be in a protocol-specific format
41468 with all scalar multibyte datatypes being big endian. Translation to
41469 this representation needs to be done both by the target before the @code{F}
41470 packet is sent, and by @value{GDBN} before
41471 it transfers memory to the target. Transferred pointers to structured
41472 data should point to the already-coerced data at any time.
41476 @unnumberedsubsubsec struct stat
41477 @cindex struct stat, in file-i/o protocol
41479 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41480 is defined as follows:
41484 unsigned int st_dev; /* device */
41485 unsigned int st_ino; /* inode */
41486 mode_t st_mode; /* protection */
41487 unsigned int st_nlink; /* number of hard links */
41488 unsigned int st_uid; /* user ID of owner */
41489 unsigned int st_gid; /* group ID of owner */
41490 unsigned int st_rdev; /* device type (if inode device) */
41491 unsigned long st_size; /* total size, in bytes */
41492 unsigned long st_blksize; /* blocksize for filesystem I/O */
41493 unsigned long st_blocks; /* number of blocks allocated */
41494 time_t st_atime; /* time of last access */
41495 time_t st_mtime; /* time of last modification */
41496 time_t st_ctime; /* time of last change */
41500 The integral datatypes conform to the definitions given in the
41501 appropriate section (see @ref{Integral Datatypes}, for details) so this
41502 structure is of size 64 bytes.
41504 The values of several fields have a restricted meaning and/or
41510 A value of 0 represents a file, 1 the console.
41513 No valid meaning for the target. Transmitted unchanged.
41516 Valid mode bits are described in @ref{Constants}. Any other
41517 bits have currently no meaning for the target.
41522 No valid meaning for the target. Transmitted unchanged.
41527 These values have a host and file system dependent
41528 accuracy. Especially on Windows hosts, the file system may not
41529 support exact timing values.
41532 The target gets a @code{struct stat} of the above representation and is
41533 responsible for coercing it to the target representation before
41536 Note that due to size differences between the host, target, and protocol
41537 representations of @code{struct stat} members, these members could eventually
41538 get truncated on the target.
41540 @node struct timeval
41541 @unnumberedsubsubsec struct timeval
41542 @cindex struct timeval, in file-i/o protocol
41544 The buffer of type @code{struct timeval} used by the File-I/O protocol
41545 is defined as follows:
41549 time_t tv_sec; /* second */
41550 long tv_usec; /* microsecond */
41554 The integral datatypes conform to the definitions given in the
41555 appropriate section (see @ref{Integral Datatypes}, for details) so this
41556 structure is of size 8 bytes.
41559 @subsection Constants
41560 @cindex constants, in file-i/o protocol
41562 The following values are used for the constants inside of the
41563 protocol. @value{GDBN} and target are responsible for translating these
41564 values before and after the call as needed.
41575 @unnumberedsubsubsec Open Flags
41576 @cindex open flags, in file-i/o protocol
41578 All values are given in hexadecimal representation.
41590 @node mode_t Values
41591 @unnumberedsubsubsec mode_t Values
41592 @cindex mode_t values, in file-i/o protocol
41594 All values are given in octal representation.
41611 @unnumberedsubsubsec Errno Values
41612 @cindex errno values, in file-i/o protocol
41614 All values are given in decimal representation.
41639 @code{EUNKNOWN} is used as a fallback error value if a host system returns
41640 any error value not in the list of supported error numbers.
41643 @unnumberedsubsubsec Lseek Flags
41644 @cindex lseek flags, in file-i/o protocol
41653 @unnumberedsubsubsec Limits
41654 @cindex limits, in file-i/o protocol
41656 All values are given in decimal representation.
41659 INT_MIN -2147483648
41661 UINT_MAX 4294967295
41662 LONG_MIN -9223372036854775808
41663 LONG_MAX 9223372036854775807
41664 ULONG_MAX 18446744073709551615
41667 @node File-I/O Examples
41668 @subsection File-I/O Examples
41669 @cindex file-i/o examples
41671 Example sequence of a write call, file descriptor 3, buffer is at target
41672 address 0x1234, 6 bytes should be written:
41675 <- @code{Fwrite,3,1234,6}
41676 @emph{request memory read from target}
41679 @emph{return "6 bytes written"}
41683 Example sequence of a read call, file descriptor 3, buffer is at target
41684 address 0x1234, 6 bytes should be read:
41687 <- @code{Fread,3,1234,6}
41688 @emph{request memory write to target}
41689 -> @code{X1234,6:XXXXXX}
41690 @emph{return "6 bytes read"}
41694 Example sequence of a read call, call fails on the host due to invalid
41695 file descriptor (@code{EBADF}):
41698 <- @code{Fread,3,1234,6}
41702 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41706 <- @code{Fread,3,1234,6}
41711 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41715 <- @code{Fread,3,1234,6}
41716 -> @code{X1234,6:XXXXXX}
41720 @node Library List Format
41721 @section Library List Format
41722 @cindex library list format, remote protocol
41724 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
41725 same process as your application to manage libraries. In this case,
41726 @value{GDBN} can use the loader's symbol table and normal memory
41727 operations to maintain a list of shared libraries. On other
41728 platforms, the operating system manages loaded libraries.
41729 @value{GDBN} can not retrieve the list of currently loaded libraries
41730 through memory operations, so it uses the @samp{qXfer:libraries:read}
41731 packet (@pxref{qXfer library list read}) instead. The remote stub
41732 queries the target's operating system and reports which libraries
41735 The @samp{qXfer:libraries:read} packet returns an XML document which
41736 lists loaded libraries and their offsets. Each library has an
41737 associated name and one or more segment or section base addresses,
41738 which report where the library was loaded in memory.
41740 For the common case of libraries that are fully linked binaries, the
41741 library should have a list of segments. If the target supports
41742 dynamic linking of a relocatable object file, its library XML element
41743 should instead include a list of allocated sections. The segment or
41744 section bases are start addresses, not relocation offsets; they do not
41745 depend on the library's link-time base addresses.
41747 @value{GDBN} must be linked with the Expat library to support XML
41748 library lists. @xref{Expat}.
41750 A simple memory map, with one loaded library relocated by a single
41751 offset, looks like this:
41755 <library name="/lib/libc.so.6">
41756 <segment address="0x10000000"/>
41761 Another simple memory map, with one loaded library with three
41762 allocated sections (.text, .data, .bss), looks like this:
41766 <library name="sharedlib.o">
41767 <section address="0x10000000"/>
41768 <section address="0x20000000"/>
41769 <section address="0x30000000"/>
41774 The format of a library list is described by this DTD:
41777 <!-- library-list: Root element with versioning -->
41778 <!ELEMENT library-list (library)*>
41779 <!ATTLIST library-list version CDATA #FIXED "1.0">
41780 <!ELEMENT library (segment*, section*)>
41781 <!ATTLIST library name CDATA #REQUIRED>
41782 <!ELEMENT segment EMPTY>
41783 <!ATTLIST segment address CDATA #REQUIRED>
41784 <!ELEMENT section EMPTY>
41785 <!ATTLIST section address CDATA #REQUIRED>
41788 In addition, segments and section descriptors cannot be mixed within a
41789 single library element, and you must supply at least one segment or
41790 section for each library.
41792 @node Library List Format for SVR4 Targets
41793 @section Library List Format for SVR4 Targets
41794 @cindex library list format, remote protocol
41796 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41797 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
41798 shared libraries. Still a special library list provided by this packet is
41799 more efficient for the @value{GDBN} remote protocol.
41801 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
41802 loaded libraries and their SVR4 linker parameters. For each library on SVR4
41803 target, the following parameters are reported:
41807 @code{name}, the absolute file name from the @code{l_name} field of
41808 @code{struct link_map}.
41810 @code{lm} with address of @code{struct link_map} used for TLS
41811 (Thread Local Storage) access.
41813 @code{l_addr}, the displacement as read from the field @code{l_addr} of
41814 @code{struct link_map}. For prelinked libraries this is not an absolute
41815 memory address. It is a displacement of absolute memory address against
41816 address the file was prelinked to during the library load.
41818 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
41821 Additionally the single @code{main-lm} attribute specifies address of
41822 @code{struct link_map} used for the main executable. This parameter is used
41823 for TLS access and its presence is optional.
41825 @value{GDBN} must be linked with the Expat library to support XML
41826 SVR4 library lists. @xref{Expat}.
41828 A simple memory map, with two loaded libraries (which do not use prelink),
41832 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
41833 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
41835 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
41837 </library-list-svr>
41840 The format of an SVR4 library list is described by this DTD:
41843 <!-- library-list-svr4: Root element with versioning -->
41844 <!ELEMENT library-list-svr4 (library)*>
41845 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
41846 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
41847 <!ELEMENT library EMPTY>
41848 <!ATTLIST library name CDATA #REQUIRED>
41849 <!ATTLIST library lm CDATA #REQUIRED>
41850 <!ATTLIST library l_addr CDATA #REQUIRED>
41851 <!ATTLIST library l_ld CDATA #REQUIRED>
41854 @node Memory Map Format
41855 @section Memory Map Format
41856 @cindex memory map format
41858 To be able to write into flash memory, @value{GDBN} needs to obtain a
41859 memory map from the target. This section describes the format of the
41862 The memory map is obtained using the @samp{qXfer:memory-map:read}
41863 (@pxref{qXfer memory map read}) packet and is an XML document that
41864 lists memory regions.
41866 @value{GDBN} must be linked with the Expat library to support XML
41867 memory maps. @xref{Expat}.
41869 The top-level structure of the document is shown below:
41872 <?xml version="1.0"?>
41873 <!DOCTYPE memory-map
41874 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41875 "http://sourceware.org/gdb/gdb-memory-map.dtd">
41881 Each region can be either:
41886 A region of RAM starting at @var{addr} and extending for @var{length}
41890 <memory type="ram" start="@var{addr}" length="@var{length}"/>
41895 A region of read-only memory:
41898 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41903 A region of flash memory, with erasure blocks @var{blocksize}
41907 <memory type="flash" start="@var{addr}" length="@var{length}">
41908 <property name="blocksize">@var{blocksize}</property>
41914 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41915 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41916 packets to write to addresses in such ranges.
41918 The formal DTD for memory map format is given below:
41921 <!-- ................................................... -->
41922 <!-- Memory Map XML DTD ................................ -->
41923 <!-- File: memory-map.dtd .............................. -->
41924 <!-- .................................... .............. -->
41925 <!-- memory-map.dtd -->
41926 <!-- memory-map: Root element with versioning -->
41927 <!ELEMENT memory-map (memory | property)>
41928 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41929 <!ELEMENT memory (property)>
41930 <!-- memory: Specifies a memory region,
41931 and its type, or device. -->
41932 <!ATTLIST memory type CDATA #REQUIRED
41933 start CDATA #REQUIRED
41934 length CDATA #REQUIRED
41935 device CDATA #IMPLIED>
41936 <!-- property: Generic attribute tag -->
41937 <!ELEMENT property (#PCDATA | property)*>
41938 <!ATTLIST property name CDATA #REQUIRED>
41941 @node Thread List Format
41942 @section Thread List Format
41943 @cindex thread list format
41945 To efficiently update the list of threads and their attributes,
41946 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41947 (@pxref{qXfer threads read}) and obtains the XML document with
41948 the following structure:
41951 <?xml version="1.0"?>
41953 <thread id="id" core="0">
41954 ... description ...
41959 Each @samp{thread} element must have the @samp{id} attribute that
41960 identifies the thread (@pxref{thread-id syntax}). The
41961 @samp{core} attribute, if present, specifies which processor core
41962 the thread was last executing on. The content of the of @samp{thread}
41963 element is interpreted as human-readable auxilliary information.
41965 @node Traceframe Info Format
41966 @section Traceframe Info Format
41967 @cindex traceframe info format
41969 To be able to know which objects in the inferior can be examined when
41970 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41971 memory ranges, registers and trace state variables that have been
41972 collected in a traceframe.
41974 This list is obtained using the @samp{qXfer:traceframe-info:read}
41975 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41977 @value{GDBN} must be linked with the Expat library to support XML
41978 traceframe info discovery. @xref{Expat}.
41980 The top-level structure of the document is shown below:
41983 <?xml version="1.0"?>
41984 <!DOCTYPE traceframe-info
41985 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41986 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41992 Each traceframe block can be either:
41997 A region of collected memory starting at @var{addr} and extending for
41998 @var{length} bytes from there:
42001 <memory start="@var{addr}" length="@var{length}"/>
42005 A block indicating trace state variable numbered @var{number} has been
42009 <tvar id="@var{number}"/>
42014 The formal DTD for the traceframe info format is given below:
42017 <!ELEMENT traceframe-info (memory | tvar)* >
42018 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
42020 <!ELEMENT memory EMPTY>
42021 <!ATTLIST memory start CDATA #REQUIRED
42022 length CDATA #REQUIRED>
42024 <!ATTLIST tvar id CDATA #REQUIRED>
42027 @node Branch Trace Format
42028 @section Branch Trace Format
42029 @cindex branch trace format
42031 In order to display the branch trace of an inferior thread,
42032 @value{GDBN} needs to obtain the list of branches. This list is
42033 represented as list of sequential code blocks that are connected via
42034 branches. The code in each block has been executed sequentially.
42036 This list is obtained using the @samp{qXfer:btrace:read}
42037 (@pxref{qXfer btrace read}) packet and is an XML document.
42039 @value{GDBN} must be linked with the Expat library to support XML
42040 traceframe info discovery. @xref{Expat}.
42042 The top-level structure of the document is shown below:
42045 <?xml version="1.0"?>
42047 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
42048 "http://sourceware.org/gdb/gdb-btrace.dtd">
42057 A block of sequentially executed instructions starting at @var{begin}
42058 and ending at @var{end}:
42061 <block begin="@var{begin}" end="@var{end}"/>
42066 The formal DTD for the branch trace format is given below:
42069 <!ELEMENT btrace (block)* >
42070 <!ATTLIST btrace version CDATA #FIXED "1.0">
42072 <!ELEMENT block EMPTY>
42073 <!ATTLIST block begin CDATA #REQUIRED
42074 end CDATA #REQUIRED>
42077 @include agentexpr.texi
42079 @node Target Descriptions
42080 @appendix Target Descriptions
42081 @cindex target descriptions
42083 One of the challenges of using @value{GDBN} to debug embedded systems
42084 is that there are so many minor variants of each processor
42085 architecture in use. It is common practice for vendors to start with
42086 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
42087 and then make changes to adapt it to a particular market niche. Some
42088 architectures have hundreds of variants, available from dozens of
42089 vendors. This leads to a number of problems:
42093 With so many different customized processors, it is difficult for
42094 the @value{GDBN} maintainers to keep up with the changes.
42096 Since individual variants may have short lifetimes or limited
42097 audiences, it may not be worthwhile to carry information about every
42098 variant in the @value{GDBN} source tree.
42100 When @value{GDBN} does support the architecture of the embedded system
42101 at hand, the task of finding the correct architecture name to give the
42102 @command{set architecture} command can be error-prone.
42105 To address these problems, the @value{GDBN} remote protocol allows a
42106 target system to not only identify itself to @value{GDBN}, but to
42107 actually describe its own features. This lets @value{GDBN} support
42108 processor variants it has never seen before --- to the extent that the
42109 descriptions are accurate, and that @value{GDBN} understands them.
42111 @value{GDBN} must be linked with the Expat library to support XML
42112 target descriptions. @xref{Expat}.
42115 * Retrieving Descriptions:: How descriptions are fetched from a target.
42116 * Target Description Format:: The contents of a target description.
42117 * Predefined Target Types:: Standard types available for target
42119 * Standard Target Features:: Features @value{GDBN} knows about.
42122 @node Retrieving Descriptions
42123 @section Retrieving Descriptions
42125 Target descriptions can be read from the target automatically, or
42126 specified by the user manually. The default behavior is to read the
42127 description from the target. @value{GDBN} retrieves it via the remote
42128 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42129 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42130 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42131 XML document, of the form described in @ref{Target Description
42134 Alternatively, you can specify a file to read for the target description.
42135 If a file is set, the target will not be queried. The commands to
42136 specify a file are:
42139 @cindex set tdesc filename
42140 @item set tdesc filename @var{path}
42141 Read the target description from @var{path}.
42143 @cindex unset tdesc filename
42144 @item unset tdesc filename
42145 Do not read the XML target description from a file. @value{GDBN}
42146 will use the description supplied by the current target.
42148 @cindex show tdesc filename
42149 @item show tdesc filename
42150 Show the filename to read for a target description, if any.
42154 @node Target Description Format
42155 @section Target Description Format
42156 @cindex target descriptions, XML format
42158 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42159 document which complies with the Document Type Definition provided in
42160 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42161 means you can use generally available tools like @command{xmllint} to
42162 check that your feature descriptions are well-formed and valid.
42163 However, to help people unfamiliar with XML write descriptions for
42164 their targets, we also describe the grammar here.
42166 Target descriptions can identify the architecture of the remote target
42167 and (for some architectures) provide information about custom register
42168 sets. They can also identify the OS ABI of the remote target.
42169 @value{GDBN} can use this information to autoconfigure for your
42170 target, or to warn you if you connect to an unsupported target.
42172 Here is a simple target description:
42175 <target version="1.0">
42176 <architecture>i386:x86-64</architecture>
42181 This minimal description only says that the target uses
42182 the x86-64 architecture.
42184 A target description has the following overall form, with [ ] marking
42185 optional elements and @dots{} marking repeatable elements. The elements
42186 are explained further below.
42189 <?xml version="1.0"?>
42190 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42191 <target version="1.0">
42192 @r{[}@var{architecture}@r{]}
42193 @r{[}@var{osabi}@r{]}
42194 @r{[}@var{compatible}@r{]}
42195 @r{[}@var{feature}@dots{}@r{]}
42200 The description is generally insensitive to whitespace and line
42201 breaks, under the usual common-sense rules. The XML version
42202 declaration and document type declaration can generally be omitted
42203 (@value{GDBN} does not require them), but specifying them may be
42204 useful for XML validation tools. The @samp{version} attribute for
42205 @samp{<target>} may also be omitted, but we recommend
42206 including it; if future versions of @value{GDBN} use an incompatible
42207 revision of @file{gdb-target.dtd}, they will detect and report
42208 the version mismatch.
42210 @subsection Inclusion
42211 @cindex target descriptions, inclusion
42214 @cindex <xi:include>
42217 It can sometimes be valuable to split a target description up into
42218 several different annexes, either for organizational purposes, or to
42219 share files between different possible target descriptions. You can
42220 divide a description into multiple files by replacing any element of
42221 the target description with an inclusion directive of the form:
42224 <xi:include href="@var{document}"/>
42228 When @value{GDBN} encounters an element of this form, it will retrieve
42229 the named XML @var{document}, and replace the inclusion directive with
42230 the contents of that document. If the current description was read
42231 using @samp{qXfer}, then so will be the included document;
42232 @var{document} will be interpreted as the name of an annex. If the
42233 current description was read from a file, @value{GDBN} will look for
42234 @var{document} as a file in the same directory where it found the
42235 original description.
42237 @subsection Architecture
42238 @cindex <architecture>
42240 An @samp{<architecture>} element has this form:
42243 <architecture>@var{arch}</architecture>
42246 @var{arch} is one of the architectures from the set accepted by
42247 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42250 @cindex @code{<osabi>}
42252 This optional field was introduced in @value{GDBN} version 7.0.
42253 Previous versions of @value{GDBN} ignore it.
42255 An @samp{<osabi>} element has this form:
42258 <osabi>@var{abi-name}</osabi>
42261 @var{abi-name} is an OS ABI name from the same selection accepted by
42262 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42264 @subsection Compatible Architecture
42265 @cindex @code{<compatible>}
42267 This optional field was introduced in @value{GDBN} version 7.0.
42268 Previous versions of @value{GDBN} ignore it.
42270 A @samp{<compatible>} element has this form:
42273 <compatible>@var{arch}</compatible>
42276 @var{arch} is one of the architectures from the set accepted by
42277 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42279 A @samp{<compatible>} element is used to specify that the target
42280 is able to run binaries in some other than the main target architecture
42281 given by the @samp{<architecture>} element. For example, on the
42282 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42283 or @code{powerpc:common64}, but the system is able to run binaries
42284 in the @code{spu} architecture as well. The way to describe this
42285 capability with @samp{<compatible>} is as follows:
42288 <architecture>powerpc:common</architecture>
42289 <compatible>spu</compatible>
42292 @subsection Features
42295 Each @samp{<feature>} describes some logical portion of the target
42296 system. Features are currently used to describe available CPU
42297 registers and the types of their contents. A @samp{<feature>} element
42301 <feature name="@var{name}">
42302 @r{[}@var{type}@dots{}@r{]}
42308 Each feature's name should be unique within the description. The name
42309 of a feature does not matter unless @value{GDBN} has some special
42310 knowledge of the contents of that feature; if it does, the feature
42311 should have its standard name. @xref{Standard Target Features}.
42315 Any register's value is a collection of bits which @value{GDBN} must
42316 interpret. The default interpretation is a two's complement integer,
42317 but other types can be requested by name in the register description.
42318 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42319 Target Types}), and the description can define additional composite types.
42321 Each type element must have an @samp{id} attribute, which gives
42322 a unique (within the containing @samp{<feature>}) name to the type.
42323 Types must be defined before they are used.
42326 Some targets offer vector registers, which can be treated as arrays
42327 of scalar elements. These types are written as @samp{<vector>} elements,
42328 specifying the array element type, @var{type}, and the number of elements,
42332 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42336 If a register's value is usefully viewed in multiple ways, define it
42337 with a union type containing the useful representations. The
42338 @samp{<union>} element contains one or more @samp{<field>} elements,
42339 each of which has a @var{name} and a @var{type}:
42342 <union id="@var{id}">
42343 <field name="@var{name}" type="@var{type}"/>
42349 If a register's value is composed from several separate values, define
42350 it with a structure type. There are two forms of the @samp{<struct>}
42351 element; a @samp{<struct>} element must either contain only bitfields
42352 or contain no bitfields. If the structure contains only bitfields,
42353 its total size in bytes must be specified, each bitfield must have an
42354 explicit start and end, and bitfields are automatically assigned an
42355 integer type. The field's @var{start} should be less than or
42356 equal to its @var{end}, and zero represents the least significant bit.
42359 <struct id="@var{id}" size="@var{size}">
42360 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42365 If the structure contains no bitfields, then each field has an
42366 explicit type, and no implicit padding is added.
42369 <struct id="@var{id}">
42370 <field name="@var{name}" type="@var{type}"/>
42376 If a register's value is a series of single-bit flags, define it with
42377 a flags type. The @samp{<flags>} element has an explicit @var{size}
42378 and contains one or more @samp{<field>} elements. Each field has a
42379 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
42383 <flags id="@var{id}" size="@var{size}">
42384 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42389 @subsection Registers
42392 Each register is represented as an element with this form:
42395 <reg name="@var{name}"
42396 bitsize="@var{size}"
42397 @r{[}regnum="@var{num}"@r{]}
42398 @r{[}save-restore="@var{save-restore}"@r{]}
42399 @r{[}type="@var{type}"@r{]}
42400 @r{[}group="@var{group}"@r{]}/>
42404 The components are as follows:
42409 The register's name; it must be unique within the target description.
42412 The register's size, in bits.
42415 The register's number. If omitted, a register's number is one greater
42416 than that of the previous register (either in the current feature or in
42417 a preceding feature); the first register in the target description
42418 defaults to zero. This register number is used to read or write
42419 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42420 packets, and registers appear in the @code{g} and @code{G} packets
42421 in order of increasing register number.
42424 Whether the register should be preserved across inferior function
42425 calls; this must be either @code{yes} or @code{no}. The default is
42426 @code{yes}, which is appropriate for most registers except for
42427 some system control registers; this is not related to the target's
42431 The type of the register. @var{type} may be a predefined type, a type
42432 defined in the current feature, or one of the special types @code{int}
42433 and @code{float}. @code{int} is an integer type of the correct size
42434 for @var{bitsize}, and @code{float} is a floating point type (in the
42435 architecture's normal floating point format) of the correct size for
42436 @var{bitsize}. The default is @code{int}.
42439 The register group to which this register belongs. @var{group} must
42440 be either @code{general}, @code{float}, or @code{vector}. If no
42441 @var{group} is specified, @value{GDBN} will not display the register
42442 in @code{info registers}.
42446 @node Predefined Target Types
42447 @section Predefined Target Types
42448 @cindex target descriptions, predefined types
42450 Type definitions in the self-description can build up composite types
42451 from basic building blocks, but can not define fundamental types. Instead,
42452 standard identifiers are provided by @value{GDBN} for the fundamental
42453 types. The currently supported types are:
42462 Signed integer types holding the specified number of bits.
42469 Unsigned integer types holding the specified number of bits.
42473 Pointers to unspecified code and data. The program counter and
42474 any dedicated return address register may be marked as code
42475 pointers; printing a code pointer converts it into a symbolic
42476 address. The stack pointer and any dedicated address registers
42477 may be marked as data pointers.
42480 Single precision IEEE floating point.
42483 Double precision IEEE floating point.
42486 The 12-byte extended precision format used by ARM FPA registers.
42489 The 10-byte extended precision format used by x87 registers.
42492 32bit @sc{eflags} register used by x86.
42495 32bit @sc{mxcsr} register used by x86.
42499 @node Standard Target Features
42500 @section Standard Target Features
42501 @cindex target descriptions, standard features
42503 A target description must contain either no registers or all the
42504 target's registers. If the description contains no registers, then
42505 @value{GDBN} will assume a default register layout, selected based on
42506 the architecture. If the description contains any registers, the
42507 default layout will not be used; the standard registers must be
42508 described in the target description, in such a way that @value{GDBN}
42509 can recognize them.
42511 This is accomplished by giving specific names to feature elements
42512 which contain standard registers. @value{GDBN} will look for features
42513 with those names and verify that they contain the expected registers;
42514 if any known feature is missing required registers, or if any required
42515 feature is missing, @value{GDBN} will reject the target
42516 description. You can add additional registers to any of the
42517 standard features --- @value{GDBN} will display them just as if
42518 they were added to an unrecognized feature.
42520 This section lists the known features and their expected contents.
42521 Sample XML documents for these features are included in the
42522 @value{GDBN} source tree, in the directory @file{gdb/features}.
42524 Names recognized by @value{GDBN} should include the name of the
42525 company or organization which selected the name, and the overall
42526 architecture to which the feature applies; so e.g.@: the feature
42527 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
42529 The names of registers are not case sensitive for the purpose
42530 of recognizing standard features, but @value{GDBN} will only display
42531 registers using the capitalization used in the description.
42534 * AArch64 Features::
42539 * Nios II Features::
42540 * PowerPC Features::
42541 * S/390 and System z Features::
42546 @node AArch64 Features
42547 @subsection AArch64 Features
42548 @cindex target descriptions, AArch64 features
42550 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42551 targets. It should contain registers @samp{x0} through @samp{x30},
42552 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42554 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42555 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42559 @subsection ARM Features
42560 @cindex target descriptions, ARM features
42562 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
42564 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
42565 @samp{lr}, @samp{pc}, and @samp{cpsr}.
42567 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
42568 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
42569 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
42572 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
42573 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
42575 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
42576 it should contain at least registers @samp{wR0} through @samp{wR15} and
42577 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
42578 @samp{wCSSF}, and @samp{wCASF} registers are optional.
42580 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
42581 should contain at least registers @samp{d0} through @samp{d15}. If
42582 they are present, @samp{d16} through @samp{d31} should also be included.
42583 @value{GDBN} will synthesize the single-precision registers from
42584 halves of the double-precision registers.
42586 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
42587 need to contain registers; it instructs @value{GDBN} to display the
42588 VFP double-precision registers as vectors and to synthesize the
42589 quad-precision registers from pairs of double-precision registers.
42590 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
42591 be present and include 32 double-precision registers.
42593 @node i386 Features
42594 @subsection i386 Features
42595 @cindex target descriptions, i386 features
42597 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42598 targets. It should describe the following registers:
42602 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42604 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42606 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42607 @samp{fs}, @samp{gs}
42609 @samp{st0} through @samp{st7}
42611 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42612 @samp{foseg}, @samp{fooff} and @samp{fop}
42615 The register sets may be different, depending on the target.
42617 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42618 describe registers:
42622 @samp{xmm0} through @samp{xmm7} for i386
42624 @samp{xmm0} through @samp{xmm15} for amd64
42629 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42630 @samp{org.gnu.gdb.i386.sse} feature. It should
42631 describe the upper 128 bits of @sc{ymm} registers:
42635 @samp{ymm0h} through @samp{ymm7h} for i386
42637 @samp{ymm0h} through @samp{ymm15h} for amd64
42640 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42641 describe a single register, @samp{orig_eax}.
42643 @node MIPS Features
42644 @subsection @acronym{MIPS} Features
42645 @cindex target descriptions, @acronym{MIPS} features
42647 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42648 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42649 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42652 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42653 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42654 registers. They may be 32-bit or 64-bit depending on the target.
42656 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42657 it may be optional in a future version of @value{GDBN}. It should
42658 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42659 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42661 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42662 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42663 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42664 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42666 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42667 contain a single register, @samp{restart}, which is used by the
42668 Linux kernel to control restartable syscalls.
42670 @node M68K Features
42671 @subsection M68K Features
42672 @cindex target descriptions, M68K features
42675 @item @samp{org.gnu.gdb.m68k.core}
42676 @itemx @samp{org.gnu.gdb.coldfire.core}
42677 @itemx @samp{org.gnu.gdb.fido.core}
42678 One of those features must be always present.
42679 The feature that is present determines which flavor of m68k is
42680 used. The feature that is present should contain registers
42681 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42682 @samp{sp}, @samp{ps} and @samp{pc}.
42684 @item @samp{org.gnu.gdb.coldfire.fp}
42685 This feature is optional. If present, it should contain registers
42686 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42690 @node Nios II Features
42691 @subsection Nios II Features
42692 @cindex target descriptions, Nios II features
42694 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42695 targets. It should contain the 32 core registers (@samp{zero},
42696 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42697 @samp{pc}, and the 16 control registers (@samp{status} through
42700 @node PowerPC Features
42701 @subsection PowerPC Features
42702 @cindex target descriptions, PowerPC features
42704 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42705 targets. It should contain registers @samp{r0} through @samp{r31},
42706 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42707 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42709 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42710 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42712 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42713 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42716 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42717 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42718 will combine these registers with the floating point registers
42719 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42720 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42721 through @samp{vs63}, the set of vector registers for POWER7.
42723 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42724 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42725 @samp{spefscr}. SPE targets should provide 32-bit registers in
42726 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42727 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42728 these to present registers @samp{ev0} through @samp{ev31} to the
42731 @node S/390 and System z Features
42732 @subsection S/390 and System z Features
42733 @cindex target descriptions, S/390 features
42734 @cindex target descriptions, System z features
42736 The @samp{org.gnu.gdb.s390.core} feature is required for S/390 and
42737 System z targets. It should contain the PSW and the 16 general
42738 registers. In particular, System z targets should provide the 64-bit
42739 registers @samp{pswm}, @samp{pswa}, and @samp{r0} through @samp{r15}.
42740 S/390 targets should provide the 32-bit versions of these registers.
42741 A System z target that runs in 31-bit addressing mode should provide
42742 32-bit versions of @samp{pswm} and @samp{pswa}, as well as the general
42743 register's upper halves @samp{r0h} through @samp{r15h}, and their
42744 lower halves @samp{r0l} through @samp{r15l}.
42746 The @samp{org.gnu.gdb.s390.fpr} feature is required. It should
42747 contain the 64-bit registers @samp{f0} through @samp{f15}, and
42750 The @samp{org.gnu.gdb.s390.acr} feature is required. It should
42751 contain the 32-bit registers @samp{acr0} through @samp{acr15}.
42753 The @samp{org.gnu.gdb.s390.linux} feature is optional. It should
42754 contain the register @samp{orig_r2}, which is 64-bit wide on System z
42755 targets and 32-bit otherwise. In addition, the feature may contain
42756 the @samp{last_break} register, whose width depends on the addressing
42757 mode, as well as the @samp{system_call} register, which is always
42760 The @samp{org.gnu.gdb.s390.tdb} feature is optional. It should
42761 contain the 64-bit registers @samp{tdb0}, @samp{tac}, @samp{tct},
42762 @samp{atia}, and @samp{tr0} through @samp{tr15}.
42764 @node TIC6x Features
42765 @subsection TMS320C6x Features
42766 @cindex target descriptions, TIC6x features
42767 @cindex target descriptions, TMS320C6x features
42768 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42769 targets. It should contain registers @samp{A0} through @samp{A15},
42770 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42772 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42773 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42774 through @samp{B31}.
42776 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42777 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42779 @node Operating System Information
42780 @appendix Operating System Information
42781 @cindex operating system information
42787 Users of @value{GDBN} often wish to obtain information about the state of
42788 the operating system running on the target---for example the list of
42789 processes, or the list of open files. This section describes the
42790 mechanism that makes it possible. This mechanism is similar to the
42791 target features mechanism (@pxref{Target Descriptions}), but focuses
42792 on a different aspect of target.
42794 Operating system information is retrived from the target via the
42795 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42796 read}). The object name in the request should be @samp{osdata}, and
42797 the @var{annex} identifies the data to be fetched.
42800 @appendixsection Process list
42801 @cindex operating system information, process list
42803 When requesting the process list, the @var{annex} field in the
42804 @samp{qXfer} request should be @samp{processes}. The returned data is
42805 an XML document. The formal syntax of this document is defined in
42806 @file{gdb/features/osdata.dtd}.
42808 An example document is:
42811 <?xml version="1.0"?>
42812 <!DOCTYPE target SYSTEM "osdata.dtd">
42813 <osdata type="processes">
42815 <column name="pid">1</column>
42816 <column name="user">root</column>
42817 <column name="command">/sbin/init</column>
42818 <column name="cores">1,2,3</column>
42823 Each item should include a column whose name is @samp{pid}. The value
42824 of that column should identify the process on the target. The
42825 @samp{user} and @samp{command} columns are optional, and will be
42826 displayed by @value{GDBN}. The @samp{cores} column, if present,
42827 should contain a comma-separated list of cores that this process
42828 is running on. Target may provide additional columns,
42829 which @value{GDBN} currently ignores.
42831 @node Trace File Format
42832 @appendix Trace File Format
42833 @cindex trace file format
42835 The trace file comes in three parts: a header, a textual description
42836 section, and a trace frame section with binary data.
42838 The header has the form @code{\x7fTRACE0\n}. The first byte is
42839 @code{0x7f} so as to indicate that the file contains binary data,
42840 while the @code{0} is a version number that may have different values
42843 The description section consists of multiple lines of @sc{ascii} text
42844 separated by newline characters (@code{0xa}). The lines may include a
42845 variety of optional descriptive or context-setting information, such
42846 as tracepoint definitions or register set size. @value{GDBN} will
42847 ignore any line that it does not recognize. An empty line marks the end
42850 @c FIXME add some specific types of data
42852 The trace frame section consists of a number of consecutive frames.
42853 Each frame begins with a two-byte tracepoint number, followed by a
42854 four-byte size giving the amount of data in the frame. The data in
42855 the frame consists of a number of blocks, each introduced by a
42856 character indicating its type (at least register, memory, and trace
42857 state variable). The data in this section is raw binary, not a
42858 hexadecimal or other encoding; its endianness matches the target's
42861 @c FIXME bi-arch may require endianness/arch info in description section
42864 @item R @var{bytes}
42865 Register block. The number and ordering of bytes matches that of a
42866 @code{g} packet in the remote protocol. Note that these are the
42867 actual bytes, in target order and @value{GDBN} register order, not a
42868 hexadecimal encoding.
42870 @item M @var{address} @var{length} @var{bytes}...
42871 Memory block. This is a contiguous block of memory, at the 8-byte
42872 address @var{address}, with a 2-byte length @var{length}, followed by
42873 @var{length} bytes.
42875 @item V @var{number} @var{value}
42876 Trace state variable block. This records the 8-byte signed value
42877 @var{value} of trace state variable numbered @var{number}.
42881 Future enhancements of the trace file format may include additional types
42884 @node Index Section Format
42885 @appendix @code{.gdb_index} section format
42886 @cindex .gdb_index section format
42887 @cindex index section format
42889 This section documents the index section that is created by @code{save
42890 gdb-index} (@pxref{Index Files}). The index section is
42891 DWARF-specific; some knowledge of DWARF is assumed in this
42894 The mapped index file format is designed to be directly
42895 @code{mmap}able on any architecture. In most cases, a datum is
42896 represented using a little-endian 32-bit integer value, called an
42897 @code{offset_type}. Big endian machines must byte-swap the values
42898 before using them. Exceptions to this rule are noted. The data is
42899 laid out such that alignment is always respected.
42901 A mapped index consists of several areas, laid out in order.
42905 The file header. This is a sequence of values, of @code{offset_type}
42906 unless otherwise noted:
42910 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42911 Version 4 uses a different hashing function from versions 5 and 6.
42912 Version 6 includes symbols for inlined functions, whereas versions 4
42913 and 5 do not. Version 7 adds attributes to the CU indices in the
42914 symbol table. Version 8 specifies that symbols from DWARF type units
42915 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42916 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42918 @value{GDBN} will only read version 4, 5, or 6 indices
42919 by specifying @code{set use-deprecated-index-sections on}.
42920 GDB has a workaround for potentially broken version 7 indices so it is
42921 currently not flagged as deprecated.
42924 The offset, from the start of the file, of the CU list.
42927 The offset, from the start of the file, of the types CU list. Note
42928 that this area can be empty, in which case this offset will be equal
42929 to the next offset.
42932 The offset, from the start of the file, of the address area.
42935 The offset, from the start of the file, of the symbol table.
42938 The offset, from the start of the file, of the constant pool.
42942 The CU list. This is a sequence of pairs of 64-bit little-endian
42943 values, sorted by the CU offset. The first element in each pair is
42944 the offset of a CU in the @code{.debug_info} section. The second
42945 element in each pair is the length of that CU. References to a CU
42946 elsewhere in the map are done using a CU index, which is just the
42947 0-based index into this table. Note that if there are type CUs, then
42948 conceptually CUs and type CUs form a single list for the purposes of
42952 The types CU list. This is a sequence of triplets of 64-bit
42953 little-endian values. In a triplet, the first value is the CU offset,
42954 the second value is the type offset in the CU, and the third value is
42955 the type signature. The types CU list is not sorted.
42958 The address area. The address area consists of a sequence of address
42959 entries. Each address entry has three elements:
42963 The low address. This is a 64-bit little-endian value.
42966 The high address. This is a 64-bit little-endian value. Like
42967 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42970 The CU index. This is an @code{offset_type} value.
42974 The symbol table. This is an open-addressed hash table. The size of
42975 the hash table is always a power of 2.
42977 Each slot in the hash table consists of a pair of @code{offset_type}
42978 values. The first value is the offset of the symbol's name in the
42979 constant pool. The second value is the offset of the CU vector in the
42982 If both values are 0, then this slot in the hash table is empty. This
42983 is ok because while 0 is a valid constant pool index, it cannot be a
42984 valid index for both a string and a CU vector.
42986 The hash value for a table entry is computed by applying an
42987 iterative hash function to the symbol's name. Starting with an
42988 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42989 the string is incorporated into the hash using the formula depending on the
42994 The formula is @code{r = r * 67 + c - 113}.
42996 @item Versions 5 to 7
42997 The formula is @code{r = r * 67 + tolower (c) - 113}.
43000 The terminating @samp{\0} is not incorporated into the hash.
43002 The step size used in the hash table is computed via
43003 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
43004 value, and @samp{size} is the size of the hash table. The step size
43005 is used to find the next candidate slot when handling a hash
43008 The names of C@t{++} symbols in the hash table are canonicalized. We
43009 don't currently have a simple description of the canonicalization
43010 algorithm; if you intend to create new index sections, you must read
43014 The constant pool. This is simply a bunch of bytes. It is organized
43015 so that alignment is correct: CU vectors are stored first, followed by
43018 A CU vector in the constant pool is a sequence of @code{offset_type}
43019 values. The first value is the number of CU indices in the vector.
43020 Each subsequent value is the index and symbol attributes of a CU in
43021 the CU list. This element in the hash table is used to indicate which
43022 CUs define the symbol and how the symbol is used.
43023 See below for the format of each CU index+attributes entry.
43025 A string in the constant pool is zero-terminated.
43028 Attributes were added to CU index values in @code{.gdb_index} version 7.
43029 If a symbol has multiple uses within a CU then there is one
43030 CU index+attributes value for each use.
43032 The format of each CU index+attributes entry is as follows
43038 This is the index of the CU in the CU list.
43040 These bits are reserved for future purposes and must be zero.
43042 The kind of the symbol in the CU.
43046 This value is reserved and should not be used.
43047 By reserving zero the full @code{offset_type} value is backwards compatible
43048 with previous versions of the index.
43050 The symbol is a type.
43052 The symbol is a variable or an enum value.
43054 The symbol is a function.
43056 Any other kind of symbol.
43058 These values are reserved.
43062 This bit is zero if the value is global and one if it is static.
43064 The determination of whether a symbol is global or static is complicated.
43065 The authorative reference is the file @file{dwarf2read.c} in
43066 @value{GDBN} sources.
43070 This pseudo-code describes the computation of a symbol's kind and
43071 global/static attributes in the index.
43074 is_external = get_attribute (die, DW_AT_external);
43075 language = get_attribute (cu_die, DW_AT_language);
43078 case DW_TAG_typedef:
43079 case DW_TAG_base_type:
43080 case DW_TAG_subrange_type:
43084 case DW_TAG_enumerator:
43086 is_static = (language != CPLUS && language != JAVA);
43088 case DW_TAG_subprogram:
43090 is_static = ! (is_external || language == ADA);
43092 case DW_TAG_constant:
43094 is_static = ! is_external;
43096 case DW_TAG_variable:
43098 is_static = ! is_external;
43100 case DW_TAG_namespace:
43104 case DW_TAG_class_type:
43105 case DW_TAG_interface_type:
43106 case DW_TAG_structure_type:
43107 case DW_TAG_union_type:
43108 case DW_TAG_enumeration_type:
43110 is_static = (language != CPLUS && language != JAVA);
43118 @appendix Manual pages
43122 * gdb man:: The GNU Debugger man page
43123 * gdbserver man:: Remote Server for the GNU Debugger man page
43124 * gcore man:: Generate a core file of a running program
43125 * gdbinit man:: gdbinit scripts
43131 @c man title gdb The GNU Debugger
43133 @c man begin SYNOPSIS gdb
43134 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43135 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43136 [@option{-b}@w{ }@var{bps}]
43137 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43138 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43139 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43140 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43141 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43144 @c man begin DESCRIPTION gdb
43145 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43146 going on ``inside'' another program while it executes -- or what another
43147 program was doing at the moment it crashed.
43149 @value{GDBN} can do four main kinds of things (plus other things in support of
43150 these) to help you catch bugs in the act:
43154 Start your program, specifying anything that might affect its behavior.
43157 Make your program stop on specified conditions.
43160 Examine what has happened, when your program has stopped.
43163 Change things in your program, so you can experiment with correcting the
43164 effects of one bug and go on to learn about another.
43167 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43170 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43171 commands from the terminal until you tell it to exit with the @value{GDBN}
43172 command @code{quit}. You can get online help from @value{GDBN} itself
43173 by using the command @code{help}.
43175 You can run @code{gdb} with no arguments or options; but the most
43176 usual way to start @value{GDBN} is with one argument or two, specifying an
43177 executable program as the argument:
43183 You can also start with both an executable program and a core file specified:
43189 You can, instead, specify a process ID as a second argument, if you want
43190 to debug a running process:
43198 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43199 named @file{1234}; @value{GDBN} does check for a core file first).
43200 With option @option{-p} you can omit the @var{program} filename.
43202 Here are some of the most frequently needed @value{GDBN} commands:
43204 @c pod2man highlights the right hand side of the @item lines.
43206 @item break [@var{file}:]@var{functiop}
43207 Set a breakpoint at @var{function} (in @var{file}).
43209 @item run [@var{arglist}]
43210 Start your program (with @var{arglist}, if specified).
43213 Backtrace: display the program stack.
43215 @item print @var{expr}
43216 Display the value of an expression.
43219 Continue running your program (after stopping, e.g. at a breakpoint).
43222 Execute next program line (after stopping); step @emph{over} any
43223 function calls in the line.
43225 @item edit [@var{file}:]@var{function}
43226 look at the program line where it is presently stopped.
43228 @item list [@var{file}:]@var{function}
43229 type the text of the program in the vicinity of where it is presently stopped.
43232 Execute next program line (after stopping); step @emph{into} any
43233 function calls in the line.
43235 @item help [@var{name}]
43236 Show information about @value{GDBN} command @var{name}, or general information
43237 about using @value{GDBN}.
43240 Exit from @value{GDBN}.
43244 For full details on @value{GDBN},
43245 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43246 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43247 as the @code{gdb} entry in the @code{info} program.
43251 @c man begin OPTIONS gdb
43252 Any arguments other than options specify an executable
43253 file and core file (or process ID); that is, the first argument
43254 encountered with no
43255 associated option flag is equivalent to a @option{-se} option, and the second,
43256 if any, is equivalent to a @option{-c} option if it's the name of a file.
43258 both long and short forms; both are shown here. The long forms are also
43259 recognized if you truncate them, so long as enough of the option is
43260 present to be unambiguous. (If you prefer, you can flag option
43261 arguments with @option{+} rather than @option{-}, though we illustrate the
43262 more usual convention.)
43264 All the options and command line arguments you give are processed
43265 in sequential order. The order makes a difference when the @option{-x}
43271 List all options, with brief explanations.
43273 @item -symbols=@var{file}
43274 @itemx -s @var{file}
43275 Read symbol table from file @var{file}.
43278 Enable writing into executable and core files.
43280 @item -exec=@var{file}
43281 @itemx -e @var{file}
43282 Use file @var{file} as the executable file to execute when
43283 appropriate, and for examining pure data in conjunction with a core
43286 @item -se=@var{file}
43287 Read symbol table from file @var{file} and use it as the executable
43290 @item -core=@var{file}
43291 @itemx -c @var{file}
43292 Use file @var{file} as a core dump to examine.
43294 @item -command=@var{file}
43295 @itemx -x @var{file}
43296 Execute @value{GDBN} commands from file @var{file}.
43298 @item -ex @var{command}
43299 Execute given @value{GDBN} @var{command}.
43301 @item -directory=@var{directory}
43302 @itemx -d @var{directory}
43303 Add @var{directory} to the path to search for source files.
43306 Do not execute commands from @file{~/.gdbinit}.
43310 Do not execute commands from any @file{.gdbinit} initialization files.
43314 ``Quiet''. Do not print the introductory and copyright messages. These
43315 messages are also suppressed in batch mode.
43318 Run in batch mode. Exit with status @code{0} after processing all the command
43319 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43320 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43321 commands in the command files.
43323 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43324 download and run a program on another computer; in order to make this
43325 more useful, the message
43328 Program exited normally.
43332 (which is ordinarily issued whenever a program running under @value{GDBN} control
43333 terminates) is not issued when running in batch mode.
43335 @item -cd=@var{directory}
43336 Run @value{GDBN} using @var{directory} as its working directory,
43337 instead of the current directory.
43341 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43342 @value{GDBN} to output the full file name and line number in a standard,
43343 recognizable fashion each time a stack frame is displayed (which
43344 includes each time the program stops). This recognizable format looks
43345 like two @samp{\032} characters, followed by the file name, line number
43346 and character position separated by colons, and a newline. The
43347 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43348 characters as a signal to display the source code for the frame.
43351 Set the line speed (baud rate or bits per second) of any serial
43352 interface used by @value{GDBN} for remote debugging.
43354 @item -tty=@var{device}
43355 Run using @var{device} for your program's standard input and output.
43359 @c man begin SEEALSO gdb
43361 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43362 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43363 documentation are properly installed at your site, the command
43370 should give you access to the complete manual.
43372 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43373 Richard M. Stallman and Roland H. Pesch, July 1991.
43377 @node gdbserver man
43378 @heading gdbserver man
43380 @c man title gdbserver Remote Server for the GNU Debugger
43382 @c man begin SYNOPSIS gdbserver
43383 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43385 gdbserver --attach @var{comm} @var{pid}
43387 gdbserver --multi @var{comm}
43391 @c man begin DESCRIPTION gdbserver
43392 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43393 than the one which is running the program being debugged.
43396 @subheading Usage (server (target) side)
43399 Usage (server (target) side):
43402 First, you need to have a copy of the program you want to debug put onto
43403 the target system. The program can be stripped to save space if needed, as
43404 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43405 the @value{GDBN} running on the host system.
43407 To use the server, you log on to the target system, and run the @command{gdbserver}
43408 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43409 your program, and (c) its arguments. The general syntax is:
43412 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43415 For example, using a serial port, you might say:
43419 @c @file would wrap it as F</dev/com1>.
43420 target> gdbserver /dev/com1 emacs foo.txt
43423 target> gdbserver @file{/dev/com1} emacs foo.txt
43427 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43428 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43429 waits patiently for the host @value{GDBN} to communicate with it.
43431 To use a TCP connection, you could say:
43434 target> gdbserver host:2345 emacs foo.txt
43437 This says pretty much the same thing as the last example, except that we are
43438 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43439 that we are expecting to see a TCP connection from @code{host} to local TCP port
43440 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43441 want for the port number as long as it does not conflict with any existing TCP
43442 ports on the target system. This same port number must be used in the host
43443 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43444 you chose a port number that conflicts with another service, @command{gdbserver} will
43445 print an error message and exit.
43447 @command{gdbserver} can also attach to running programs.
43448 This is accomplished via the @option{--attach} argument. The syntax is:
43451 target> gdbserver --attach @var{comm} @var{pid}
43454 @var{pid} is the process ID of a currently running process. It isn't
43455 necessary to point @command{gdbserver} at a binary for the running process.
43457 To start @code{gdbserver} without supplying an initial command to run
43458 or process ID to attach, use the @option{--multi} command line option.
43459 In such case you should connect using @kbd{target extended-remote} to start
43460 the program you want to debug.
43463 target> gdbserver --multi @var{comm}
43467 @subheading Usage (host side)
43473 You need an unstripped copy of the target program on your host system, since
43474 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43475 would, with the target program as the first argument. (You may need to use the
43476 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43477 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43478 new command you need to know about is @code{target remote}
43479 (or @code{target extended-remote}). Its argument is either
43480 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43481 descriptor. For example:
43485 @c @file would wrap it as F</dev/ttyb>.
43486 (gdb) target remote /dev/ttyb
43489 (gdb) target remote @file{/dev/ttyb}
43494 communicates with the server via serial line @file{/dev/ttyb}, and:
43497 (gdb) target remote the-target:2345
43501 communicates via a TCP connection to port 2345 on host `the-target', where
43502 you previously started up @command{gdbserver} with the same port number. Note that for
43503 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43504 command, otherwise you may get an error that looks something like
43505 `Connection refused'.
43507 @command{gdbserver} can also debug multiple inferiors at once,
43510 the @value{GDBN} manual in node @code{Inferiors and Programs}
43511 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43514 @ref{Inferiors and Programs}.
43516 In such case use the @code{extended-remote} @value{GDBN} command variant:
43519 (gdb) target extended-remote the-target:2345
43522 The @command{gdbserver} option @option{--multi} may or may not be used in such
43526 @c man begin OPTIONS gdbserver
43527 There are three different modes for invoking @command{gdbserver}:
43532 Debug a specific program specified by its program name:
43535 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43538 The @var{comm} parameter specifies how should the server communicate
43539 with @value{GDBN}; it is either a device name (to use a serial line),
43540 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43541 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43542 debug in @var{prog}. Any remaining arguments will be passed to the
43543 program verbatim. When the program exits, @value{GDBN} will close the
43544 connection, and @code{gdbserver} will exit.
43547 Debug a specific program by specifying the process ID of a running
43551 gdbserver --attach @var{comm} @var{pid}
43554 The @var{comm} parameter is as described above. Supply the process ID
43555 of a running program in @var{pid}; @value{GDBN} will do everything
43556 else. Like with the previous mode, when the process @var{pid} exits,
43557 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43560 Multi-process mode -- debug more than one program/process:
43563 gdbserver --multi @var{comm}
43566 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43567 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43568 close the connection when a process being debugged exits, so you can
43569 debug several processes in the same session.
43572 In each of the modes you may specify these options:
43577 List all options, with brief explanations.
43580 This option causes @command{gdbserver} to print its version number and exit.
43583 @command{gdbserver} will attach to a running program. The syntax is:
43586 target> gdbserver --attach @var{comm} @var{pid}
43589 @var{pid} is the process ID of a currently running process. It isn't
43590 necessary to point @command{gdbserver} at a binary for the running process.
43593 To start @code{gdbserver} without supplying an initial command to run
43594 or process ID to attach, use this command line option.
43595 Then you can connect using @kbd{target extended-remote} and start
43596 the program you want to debug. The syntax is:
43599 target> gdbserver --multi @var{comm}
43603 Instruct @code{gdbserver} to display extra status information about the debugging
43605 This option is intended for @code{gdbserver} development and for bug reports to
43608 @item --remote-debug
43609 Instruct @code{gdbserver} to display remote protocol debug output.
43610 This option is intended for @code{gdbserver} development and for bug reports to
43614 Specify a wrapper to launch programs
43615 for debugging. The option should be followed by the name of the
43616 wrapper, then any command-line arguments to pass to the wrapper, then
43617 @kbd{--} indicating the end of the wrapper arguments.
43620 By default, @command{gdbserver} keeps the listening TCP port open, so that
43621 additional connections are possible. However, if you start @code{gdbserver}
43622 with the @option{--once} option, it will stop listening for any further
43623 connection attempts after connecting to the first @value{GDBN} session.
43625 @c --disable-packet is not documented for users.
43627 @c --disable-randomization and --no-disable-randomization are superseded by
43628 @c QDisableRandomization.
43633 @c man begin SEEALSO gdbserver
43635 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43636 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43637 documentation are properly installed at your site, the command
43643 should give you access to the complete manual.
43645 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43646 Richard M. Stallman and Roland H. Pesch, July 1991.
43653 @c man title gcore Generate a core file of a running program
43656 @c man begin SYNOPSIS gcore
43657 gcore [-o @var{filename}] @var{pid}
43661 @c man begin DESCRIPTION gcore
43662 Generate a core dump of a running program with process ID @var{pid}.
43663 Produced file is equivalent to a kernel produced core file as if the process
43664 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43665 limit). Unlike after a crash, after @command{gcore} the program remains
43666 running without any change.
43669 @c man begin OPTIONS gcore
43671 @item -o @var{filename}
43672 The optional argument
43673 @var{filename} specifies the file name where to put the core dump.
43674 If not specified, the file name defaults to @file{core.@var{pid}},
43675 where @var{pid} is the running program process ID.
43679 @c man begin SEEALSO gcore
43681 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43682 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43683 documentation are properly installed at your site, the command
43690 should give you access to the complete manual.
43692 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43693 Richard M. Stallman and Roland H. Pesch, July 1991.
43700 @c man title gdbinit GDB initialization scripts
43703 @c man begin SYNOPSIS gdbinit
43704 @ifset SYSTEM_GDBINIT
43705 @value{SYSTEM_GDBINIT}
43714 @c man begin DESCRIPTION gdbinit
43715 These files contain @value{GDBN} commands to automatically execute during
43716 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43719 the @value{GDBN} manual in node @code{Sequences}
43720 -- shell command @code{info -f gdb -n Sequences}.
43726 Please read more in
43728 the @value{GDBN} manual in node @code{Startup}
43729 -- shell command @code{info -f gdb -n Startup}.
43736 @ifset SYSTEM_GDBINIT
43737 @item @value{SYSTEM_GDBINIT}
43739 @ifclear SYSTEM_GDBINIT
43740 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43742 System-wide initialization file. It is executed unless user specified
43743 @value{GDBN} option @code{-nx} or @code{-n}.
43746 the @value{GDBN} manual in node @code{System-wide configuration}
43747 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43750 @ref{System-wide configuration}.
43754 User initialization file. It is executed unless user specified
43755 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43758 Initialization file for current directory. It may need to be enabled with
43759 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43762 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43763 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43766 @ref{Init File in the Current Directory}.
43771 @c man begin SEEALSO gdbinit
43773 gdb(1), @code{info -f gdb -n Startup}
43775 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43776 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43777 documentation are properly installed at your site, the command
43783 should give you access to the complete manual.
43785 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43786 Richard M. Stallman and Roland H. Pesch, July 1991.
43792 @node GNU Free Documentation License
43793 @appendix GNU Free Documentation License
43796 @node Concept Index
43797 @unnumbered Concept Index
43801 @node Command and Variable Index
43802 @unnumbered Command, Variable, and Function Index
43807 % I think something like @@colophon should be in texinfo. In the
43809 \long\def\colophon{\hbox to0pt{}\vfill
43810 \centerline{The body of this manual is set in}
43811 \centerline{\fontname\tenrm,}
43812 \centerline{with headings in {\bf\fontname\tenbf}}
43813 \centerline{and examples in {\tt\fontname\tentt}.}
43814 \centerline{{\it\fontname\tenit\/},}
43815 \centerline{{\bf\fontname\tenbf}, and}
43816 \centerline{{\sl\fontname\tensl\/}}
43817 \centerline{are used for emphasis.}\vfill}
43819 % Blame: doc@@cygnus.com, 1991.