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 @cindex raw printing
8522 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8523 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8524 Printing}). This typically results in a higher-level display of the
8525 value's contents. The @samp{r} format bypasses any Python
8526 pretty-printer which might exist.
8529 For example, to print the program counter in hex (@pxref{Registers}), type
8536 Note that no space is required before the slash; this is because command
8537 names in @value{GDBN} cannot contain a slash.
8539 To reprint the last value in the value history with a different format,
8540 you can use the @code{print} command with just a format and no
8541 expression. For example, @samp{p/x} reprints the last value in hex.
8544 @section Examining Memory
8546 You can use the command @code{x} (for ``examine'') to examine memory in
8547 any of several formats, independently of your program's data types.
8549 @cindex examining memory
8551 @kindex x @r{(examine memory)}
8552 @item x/@var{nfu} @var{addr}
8555 Use the @code{x} command to examine memory.
8558 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8559 much memory to display and how to format it; @var{addr} is an
8560 expression giving the address where you want to start displaying memory.
8561 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8562 Several commands set convenient defaults for @var{addr}.
8565 @item @var{n}, the repeat count
8566 The repeat count is a decimal integer; the default is 1. It specifies
8567 how much memory (counting by units @var{u}) to display.
8568 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8571 @item @var{f}, the display format
8572 The display format is one of the formats used by @code{print}
8573 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8574 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8575 The default is @samp{x} (hexadecimal) initially. The default changes
8576 each time you use either @code{x} or @code{print}.
8578 @item @var{u}, the unit size
8579 The unit size is any of
8585 Halfwords (two bytes).
8587 Words (four bytes). This is the initial default.
8589 Giant words (eight bytes).
8592 Each time you specify a unit size with @code{x}, that size becomes the
8593 default unit the next time you use @code{x}. For the @samp{i} format,
8594 the unit size is ignored and is normally not written. For the @samp{s} format,
8595 the unit size defaults to @samp{b}, unless it is explicitly given.
8596 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8597 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8598 Note that the results depend on the programming language of the
8599 current compilation unit. If the language is C, the @samp{s}
8600 modifier will use the UTF-16 encoding while @samp{w} will use
8601 UTF-32. The encoding is set by the programming language and cannot
8604 @item @var{addr}, starting display address
8605 @var{addr} is the address where you want @value{GDBN} to begin displaying
8606 memory. The expression need not have a pointer value (though it may);
8607 it is always interpreted as an integer address of a byte of memory.
8608 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8609 @var{addr} is usually just after the last address examined---but several
8610 other commands also set the default address: @code{info breakpoints} (to
8611 the address of the last breakpoint listed), @code{info line} (to the
8612 starting address of a line), and @code{print} (if you use it to display
8613 a value from memory).
8616 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8617 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8618 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8619 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8620 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8622 Since the letters indicating unit sizes are all distinct from the
8623 letters specifying output formats, you do not have to remember whether
8624 unit size or format comes first; either order works. The output
8625 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8626 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8628 Even though the unit size @var{u} is ignored for the formats @samp{s}
8629 and @samp{i}, you might still want to use a count @var{n}; for example,
8630 @samp{3i} specifies that you want to see three machine instructions,
8631 including any operands. For convenience, especially when used with
8632 the @code{display} command, the @samp{i} format also prints branch delay
8633 slot instructions, if any, beyond the count specified, which immediately
8634 follow the last instruction that is within the count. The command
8635 @code{disassemble} gives an alternative way of inspecting machine
8636 instructions; see @ref{Machine Code,,Source and Machine Code}.
8638 All the defaults for the arguments to @code{x} are designed to make it
8639 easy to continue scanning memory with minimal specifications each time
8640 you use @code{x}. For example, after you have inspected three machine
8641 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8642 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8643 the repeat count @var{n} is used again; the other arguments default as
8644 for successive uses of @code{x}.
8646 When examining machine instructions, the instruction at current program
8647 counter is shown with a @code{=>} marker. For example:
8650 (@value{GDBP}) x/5i $pc-6
8651 0x804837f <main+11>: mov %esp,%ebp
8652 0x8048381 <main+13>: push %ecx
8653 0x8048382 <main+14>: sub $0x4,%esp
8654 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8655 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8658 @cindex @code{$_}, @code{$__}, and value history
8659 The addresses and contents printed by the @code{x} command are not saved
8660 in the value history because there is often too much of them and they
8661 would get in the way. Instead, @value{GDBN} makes these values available for
8662 subsequent use in expressions as values of the convenience variables
8663 @code{$_} and @code{$__}. After an @code{x} command, the last address
8664 examined is available for use in expressions in the convenience variable
8665 @code{$_}. The contents of that address, as examined, are available in
8666 the convenience variable @code{$__}.
8668 If the @code{x} command has a repeat count, the address and contents saved
8669 are from the last memory unit printed; this is not the same as the last
8670 address printed if several units were printed on the last line of output.
8672 @cindex remote memory comparison
8673 @cindex verify remote memory image
8674 When you are debugging a program running on a remote target machine
8675 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8676 remote machine's memory against the executable file you downloaded to
8677 the target. The @code{compare-sections} command is provided for such
8681 @kindex compare-sections
8682 @item compare-sections @r{[}@var{section-name}@r{]}
8683 Compare the data of a loadable section @var{section-name} in the
8684 executable file of the program being debugged with the same section in
8685 the remote machine's memory, and report any mismatches. With no
8686 arguments, compares all loadable sections. This command's
8687 availability depends on the target's support for the @code{"qCRC"}
8692 @section Automatic Display
8693 @cindex automatic display
8694 @cindex display of expressions
8696 If you find that you want to print the value of an expression frequently
8697 (to see how it changes), you might want to add it to the @dfn{automatic
8698 display list} so that @value{GDBN} prints its value each time your program stops.
8699 Each expression added to the list is given a number to identify it;
8700 to remove an expression from the list, you specify that number.
8701 The automatic display looks like this:
8705 3: bar[5] = (struct hack *) 0x3804
8709 This display shows item numbers, expressions and their current values. As with
8710 displays you request manually using @code{x} or @code{print}, you can
8711 specify the output format you prefer; in fact, @code{display} decides
8712 whether to use @code{print} or @code{x} depending your format
8713 specification---it uses @code{x} if you specify either the @samp{i}
8714 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8718 @item display @var{expr}
8719 Add the expression @var{expr} to the list of expressions to display
8720 each time your program stops. @xref{Expressions, ,Expressions}.
8722 @code{display} does not repeat if you press @key{RET} again after using it.
8724 @item display/@var{fmt} @var{expr}
8725 For @var{fmt} specifying only a display format and not a size or
8726 count, add the expression @var{expr} to the auto-display list but
8727 arrange to display it each time in the specified format @var{fmt}.
8728 @xref{Output Formats,,Output Formats}.
8730 @item display/@var{fmt} @var{addr}
8731 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8732 number of units, add the expression @var{addr} as a memory address to
8733 be examined each time your program stops. Examining means in effect
8734 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8737 For example, @samp{display/i $pc} can be helpful, to see the machine
8738 instruction about to be executed each time execution stops (@samp{$pc}
8739 is a common name for the program counter; @pxref{Registers, ,Registers}).
8742 @kindex delete display
8744 @item undisplay @var{dnums}@dots{}
8745 @itemx delete display @var{dnums}@dots{}
8746 Remove items from the list of expressions to display. Specify the
8747 numbers of the displays that you want affected with the command
8748 argument @var{dnums}. It can be a single display number, one of the
8749 numbers shown in the first field of the @samp{info display} display;
8750 or it could be a range of display numbers, as in @code{2-4}.
8752 @code{undisplay} does not repeat if you press @key{RET} after using it.
8753 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8755 @kindex disable display
8756 @item disable display @var{dnums}@dots{}
8757 Disable the display of item numbers @var{dnums}. A disabled display
8758 item is not printed automatically, but is not forgotten. It may be
8759 enabled again later. Specify the numbers of the displays that you
8760 want affected with the command argument @var{dnums}. It can be a
8761 single display number, one of the numbers shown in the first field of
8762 the @samp{info display} display; or it could be a range of display
8763 numbers, as in @code{2-4}.
8765 @kindex enable display
8766 @item enable display @var{dnums}@dots{}
8767 Enable display of item numbers @var{dnums}. It becomes effective once
8768 again in auto display of its expression, until you specify otherwise.
8769 Specify the numbers of the displays that you want affected with the
8770 command argument @var{dnums}. It can be a single display number, one
8771 of the numbers shown in the first field of the @samp{info display}
8772 display; or it could be a range of display numbers, as in @code{2-4}.
8775 Display the current values of the expressions on the list, just as is
8776 done when your program stops.
8778 @kindex info display
8780 Print the list of expressions previously set up to display
8781 automatically, each one with its item number, but without showing the
8782 values. This includes disabled expressions, which are marked as such.
8783 It also includes expressions which would not be displayed right now
8784 because they refer to automatic variables not currently available.
8787 @cindex display disabled out of scope
8788 If a display expression refers to local variables, then it does not make
8789 sense outside the lexical context for which it was set up. Such an
8790 expression is disabled when execution enters a context where one of its
8791 variables is not defined. For example, if you give the command
8792 @code{display last_char} while inside a function with an argument
8793 @code{last_char}, @value{GDBN} displays this argument while your program
8794 continues to stop inside that function. When it stops elsewhere---where
8795 there is no variable @code{last_char}---the display is disabled
8796 automatically. The next time your program stops where @code{last_char}
8797 is meaningful, you can enable the display expression once again.
8799 @node Print Settings
8800 @section Print Settings
8802 @cindex format options
8803 @cindex print settings
8804 @value{GDBN} provides the following ways to control how arrays, structures,
8805 and symbols are printed.
8808 These settings are useful for debugging programs in any language:
8812 @item set print address
8813 @itemx set print address on
8814 @cindex print/don't print memory addresses
8815 @value{GDBN} prints memory addresses showing the location of stack
8816 traces, structure values, pointer values, breakpoints, and so forth,
8817 even when it also displays the contents of those addresses. The default
8818 is @code{on}. For example, this is what a stack frame display looks like with
8819 @code{set print address on}:
8824 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8826 530 if (lquote != def_lquote)
8830 @item set print address off
8831 Do not print addresses when displaying their contents. For example,
8832 this is the same stack frame displayed with @code{set print address off}:
8836 (@value{GDBP}) set print addr off
8838 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8839 530 if (lquote != def_lquote)
8843 You can use @samp{set print address off} to eliminate all machine
8844 dependent displays from the @value{GDBN} interface. For example, with
8845 @code{print address off}, you should get the same text for backtraces on
8846 all machines---whether or not they involve pointer arguments.
8849 @item show print address
8850 Show whether or not addresses are to be printed.
8853 When @value{GDBN} prints a symbolic address, it normally prints the
8854 closest earlier symbol plus an offset. If that symbol does not uniquely
8855 identify the address (for example, it is a name whose scope is a single
8856 source file), you may need to clarify. One way to do this is with
8857 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8858 you can set @value{GDBN} to print the source file and line number when
8859 it prints a symbolic address:
8862 @item set print symbol-filename on
8863 @cindex source file and line of a symbol
8864 @cindex symbol, source file and line
8865 Tell @value{GDBN} to print the source file name and line number of a
8866 symbol in the symbolic form of an address.
8868 @item set print symbol-filename off
8869 Do not print source file name and line number of a symbol. This is the
8872 @item show print symbol-filename
8873 Show whether or not @value{GDBN} will print the source file name and
8874 line number of a symbol in the symbolic form of an address.
8877 Another situation where it is helpful to show symbol filenames and line
8878 numbers is when disassembling code; @value{GDBN} shows you the line
8879 number and source file that corresponds to each instruction.
8881 Also, you may wish to see the symbolic form only if the address being
8882 printed is reasonably close to the closest earlier symbol:
8885 @item set print max-symbolic-offset @var{max-offset}
8886 @itemx set print max-symbolic-offset unlimited
8887 @cindex maximum value for offset of closest symbol
8888 Tell @value{GDBN} to only display the symbolic form of an address if the
8889 offset between the closest earlier symbol and the address is less than
8890 @var{max-offset}. The default is @code{unlimited}, which tells @value{GDBN}
8891 to always print the symbolic form of an address if any symbol precedes
8892 it. Zero is equivalent to @code{unlimited}.
8894 @item show print max-symbolic-offset
8895 Ask how large the maximum offset is that @value{GDBN} prints in a
8899 @cindex wild pointer, interpreting
8900 @cindex pointer, finding referent
8901 If you have a pointer and you are not sure where it points, try
8902 @samp{set print symbol-filename on}. Then you can determine the name
8903 and source file location of the variable where it points, using
8904 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8905 For example, here @value{GDBN} shows that a variable @code{ptt} points
8906 at another variable @code{t}, defined in @file{hi2.c}:
8909 (@value{GDBP}) set print symbol-filename on
8910 (@value{GDBP}) p/a ptt
8911 $4 = 0xe008 <t in hi2.c>
8915 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8916 does not show the symbol name and filename of the referent, even with
8917 the appropriate @code{set print} options turned on.
8920 You can also enable @samp{/a}-like formatting all the time using
8921 @samp{set print symbol on}:
8924 @item set print symbol on
8925 Tell @value{GDBN} to print the symbol corresponding to an address, if
8928 @item set print symbol off
8929 Tell @value{GDBN} not to print the symbol corresponding to an
8930 address. In this mode, @value{GDBN} will still print the symbol
8931 corresponding to pointers to functions. This is the default.
8933 @item show print symbol
8934 Show whether @value{GDBN} will display the symbol corresponding to an
8938 Other settings control how different kinds of objects are printed:
8941 @item set print array
8942 @itemx set print array on
8943 @cindex pretty print arrays
8944 Pretty print arrays. This format is more convenient to read,
8945 but uses more space. The default is off.
8947 @item set print array off
8948 Return to compressed format for arrays.
8950 @item show print array
8951 Show whether compressed or pretty format is selected for displaying
8954 @cindex print array indexes
8955 @item set print array-indexes
8956 @itemx set print array-indexes on
8957 Print the index of each element when displaying arrays. May be more
8958 convenient to locate a given element in the array or quickly find the
8959 index of a given element in that printed array. The default is off.
8961 @item set print array-indexes off
8962 Stop printing element indexes when displaying arrays.
8964 @item show print array-indexes
8965 Show whether the index of each element is printed when displaying
8968 @item set print elements @var{number-of-elements}
8969 @itemx set print elements unlimited
8970 @cindex number of array elements to print
8971 @cindex limit on number of printed array elements
8972 Set a limit on how many elements of an array @value{GDBN} will print.
8973 If @value{GDBN} is printing a large array, it stops printing after it has
8974 printed the number of elements set by the @code{set print elements} command.
8975 This limit also applies to the display of strings.
8976 When @value{GDBN} starts, this limit is set to 200.
8977 Setting @var{number-of-elements} to @code{unlimited} or zero means
8978 that the number of elements to print is unlimited.
8980 @item show print elements
8981 Display the number of elements of a large array that @value{GDBN} will print.
8982 If the number is 0, then the printing is unlimited.
8984 @item set print frame-arguments @var{value}
8985 @kindex set print frame-arguments
8986 @cindex printing frame argument values
8987 @cindex print all frame argument values
8988 @cindex print frame argument values for scalars only
8989 @cindex do not print frame argument values
8990 This command allows to control how the values of arguments are printed
8991 when the debugger prints a frame (@pxref{Frames}). The possible
8996 The values of all arguments are printed.
8999 Print the value of an argument only if it is a scalar. The value of more
9000 complex arguments such as arrays, structures, unions, etc, is replaced
9001 by @code{@dots{}}. This is the default. Here is an example where
9002 only scalar arguments are shown:
9005 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
9010 None of the argument values are printed. Instead, the value of each argument
9011 is replaced by @code{@dots{}}. In this case, the example above now becomes:
9014 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
9019 By default, only scalar arguments are printed. This command can be used
9020 to configure the debugger to print the value of all arguments, regardless
9021 of their type. However, it is often advantageous to not print the value
9022 of more complex parameters. For instance, it reduces the amount of
9023 information printed in each frame, making the backtrace more readable.
9024 Also, it improves performance when displaying Ada frames, because
9025 the computation of large arguments can sometimes be CPU-intensive,
9026 especially in large applications. Setting @code{print frame-arguments}
9027 to @code{scalars} (the default) or @code{none} avoids this computation,
9028 thus speeding up the display of each Ada frame.
9030 @item show print frame-arguments
9031 Show how the value of arguments should be displayed when printing a frame.
9033 @item set print raw frame-arguments on
9034 Print frame arguments in raw, non pretty-printed, form.
9036 @item set print raw frame-arguments off
9037 Print frame arguments in pretty-printed form, if there is a pretty-printer
9038 for the value (@pxref{Pretty Printing}),
9039 otherwise print the value in raw form.
9040 This is the default.
9042 @item show print raw frame-arguments
9043 Show whether to print frame arguments in raw form.
9045 @anchor{set print entry-values}
9046 @item set print entry-values @var{value}
9047 @kindex set print entry-values
9048 Set printing of frame argument values at function entry. In some cases
9049 @value{GDBN} can determine the value of function argument which was passed by
9050 the function caller, even if the value was modified inside the called function
9051 and therefore is different. With optimized code, the current value could be
9052 unavailable, but the entry value may still be known.
9054 The default value is @code{default} (see below for its description). Older
9055 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
9056 this feature will behave in the @code{default} setting the same way as with the
9059 This functionality is currently supported only by DWARF 2 debugging format and
9060 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
9061 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
9064 The @var{value} parameter can be one of the following:
9068 Print only actual parameter values, never print values from function entry
9072 #0 different (val=6)
9073 #0 lost (val=<optimized out>)
9075 #0 invalid (val=<optimized out>)
9079 Print only parameter values from function entry point. The actual parameter
9080 values are never printed.
9082 #0 equal (val@@entry=5)
9083 #0 different (val@@entry=5)
9084 #0 lost (val@@entry=5)
9085 #0 born (val@@entry=<optimized out>)
9086 #0 invalid (val@@entry=<optimized out>)
9090 Print only parameter values from function entry point. If value from function
9091 entry point is not known while the actual value is known, print the actual
9092 value for such parameter.
9094 #0 equal (val@@entry=5)
9095 #0 different (val@@entry=5)
9096 #0 lost (val@@entry=5)
9098 #0 invalid (val@@entry=<optimized out>)
9102 Print actual parameter values. If actual parameter value is not known while
9103 value from function entry point is known, print the entry point value for such
9107 #0 different (val=6)
9108 #0 lost (val@@entry=5)
9110 #0 invalid (val=<optimized out>)
9114 Always print both the actual parameter value and its value from function entry
9115 point, even if values of one or both are not available due to compiler
9118 #0 equal (val=5, val@@entry=5)
9119 #0 different (val=6, val@@entry=5)
9120 #0 lost (val=<optimized out>, val@@entry=5)
9121 #0 born (val=10, val@@entry=<optimized out>)
9122 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
9126 Print the actual parameter value if it is known and also its value from
9127 function entry point if it is known. If neither is known, print for the actual
9128 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
9129 values are known and identical, print the shortened
9130 @code{param=param@@entry=VALUE} notation.
9132 #0 equal (val=val@@entry=5)
9133 #0 different (val=6, val@@entry=5)
9134 #0 lost (val@@entry=5)
9136 #0 invalid (val=<optimized out>)
9140 Always print the actual parameter value. Print also its value from function
9141 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
9142 if both values are known and identical, print the shortened
9143 @code{param=param@@entry=VALUE} notation.
9145 #0 equal (val=val@@entry=5)
9146 #0 different (val=6, val@@entry=5)
9147 #0 lost (val=<optimized out>, val@@entry=5)
9149 #0 invalid (val=<optimized out>)
9153 For analysis messages on possible failures of frame argument values at function
9154 entry resolution see @ref{set debug entry-values}.
9156 @item show print entry-values
9157 Show the method being used for printing of frame argument values at function
9160 @item set print repeats @var{number-of-repeats}
9161 @itemx set print repeats unlimited
9162 @cindex repeated array elements
9163 Set the threshold for suppressing display of repeated array
9164 elements. When the number of consecutive identical elements of an
9165 array exceeds the threshold, @value{GDBN} prints the string
9166 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
9167 identical repetitions, instead of displaying the identical elements
9168 themselves. Setting the threshold to @code{unlimited} or zero will
9169 cause all elements to be individually printed. The default threshold
9172 @item show print repeats
9173 Display the current threshold for printing repeated identical
9176 @item set print null-stop
9177 @cindex @sc{null} elements in arrays
9178 Cause @value{GDBN} to stop printing the characters of an array when the first
9179 @sc{null} is encountered. This is useful when large arrays actually
9180 contain only short strings.
9183 @item show print null-stop
9184 Show whether @value{GDBN} stops printing an array on the first
9185 @sc{null} character.
9187 @item set print pretty on
9188 @cindex print structures in indented form
9189 @cindex indentation in structure display
9190 Cause @value{GDBN} to print structures in an indented format with one member
9191 per line, like this:
9206 @item set print pretty off
9207 Cause @value{GDBN} to print structures in a compact format, like this:
9211 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
9212 meat = 0x54 "Pork"@}
9217 This is the default format.
9219 @item show print pretty
9220 Show which format @value{GDBN} is using to print structures.
9222 @item set print sevenbit-strings on
9223 @cindex eight-bit characters in strings
9224 @cindex octal escapes in strings
9225 Print using only seven-bit characters; if this option is set,
9226 @value{GDBN} displays any eight-bit characters (in strings or
9227 character values) using the notation @code{\}@var{nnn}. This setting is
9228 best if you are working in English (@sc{ascii}) and you use the
9229 high-order bit of characters as a marker or ``meta'' bit.
9231 @item set print sevenbit-strings off
9232 Print full eight-bit characters. This allows the use of more
9233 international character sets, and is the default.
9235 @item show print sevenbit-strings
9236 Show whether or not @value{GDBN} is printing only seven-bit characters.
9238 @item set print union on
9239 @cindex unions in structures, printing
9240 Tell @value{GDBN} to print unions which are contained in structures
9241 and other unions. This is the default setting.
9243 @item set print union off
9244 Tell @value{GDBN} not to print unions which are contained in
9245 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
9248 @item show print union
9249 Ask @value{GDBN} whether or not it will print unions which are contained in
9250 structures and other unions.
9252 For example, given the declarations
9255 typedef enum @{Tree, Bug@} Species;
9256 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9257 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9268 struct thing foo = @{Tree, @{Acorn@}@};
9272 with @code{set print union on} in effect @samp{p foo} would print
9275 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9279 and with @code{set print union off} in effect it would print
9282 $1 = @{it = Tree, form = @{...@}@}
9286 @code{set print union} affects programs written in C-like languages
9292 These settings are of interest when debugging C@t{++} programs:
9295 @cindex demangling C@t{++} names
9296 @item set print demangle
9297 @itemx set print demangle on
9298 Print C@t{++} names in their source form rather than in the encoded
9299 (``mangled'') form passed to the assembler and linker for type-safe
9300 linkage. The default is on.
9302 @item show print demangle
9303 Show whether C@t{++} names are printed in mangled or demangled form.
9305 @item set print asm-demangle
9306 @itemx set print asm-demangle on
9307 Print C@t{++} names in their source form rather than their mangled form, even
9308 in assembler code printouts such as instruction disassemblies.
9311 @item show print asm-demangle
9312 Show whether C@t{++} names in assembly listings are printed in mangled
9315 @cindex C@t{++} symbol decoding style
9316 @cindex symbol decoding style, C@t{++}
9317 @kindex set demangle-style
9318 @item set demangle-style @var{style}
9319 Choose among several encoding schemes used by different compilers to
9320 represent C@t{++} names. The choices for @var{style} are currently:
9324 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9325 This is the default.
9328 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9331 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9334 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9337 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9338 @strong{Warning:} this setting alone is not sufficient to allow
9339 debugging @code{cfront}-generated executables. @value{GDBN} would
9340 require further enhancement to permit that.
9343 If you omit @var{style}, you will see a list of possible formats.
9345 @item show demangle-style
9346 Display the encoding style currently in use for decoding C@t{++} symbols.
9348 @item set print object
9349 @itemx set print object on
9350 @cindex derived type of an object, printing
9351 @cindex display derived types
9352 When displaying a pointer to an object, identify the @emph{actual}
9353 (derived) type of the object rather than the @emph{declared} type, using
9354 the virtual function table. Note that the virtual function table is
9355 required---this feature can only work for objects that have run-time
9356 type identification; a single virtual method in the object's declared
9357 type is sufficient. Note that this setting is also taken into account when
9358 working with variable objects via MI (@pxref{GDB/MI}).
9360 @item set print object off
9361 Display only the declared type of objects, without reference to the
9362 virtual function table. This is the default setting.
9364 @item show print object
9365 Show whether actual, or declared, object types are displayed.
9367 @item set print static-members
9368 @itemx set print static-members on
9369 @cindex static members of C@t{++} objects
9370 Print static members when displaying a C@t{++} object. The default is on.
9372 @item set print static-members off
9373 Do not print static members when displaying a C@t{++} object.
9375 @item show print static-members
9376 Show whether C@t{++} static members are printed or not.
9378 @item set print pascal_static-members
9379 @itemx set print pascal_static-members on
9380 @cindex static members of Pascal objects
9381 @cindex Pascal objects, static members display
9382 Print static members when displaying a Pascal object. The default is on.
9384 @item set print pascal_static-members off
9385 Do not print static members when displaying a Pascal object.
9387 @item show print pascal_static-members
9388 Show whether Pascal static members are printed or not.
9390 @c These don't work with HP ANSI C++ yet.
9391 @item set print vtbl
9392 @itemx set print vtbl on
9393 @cindex pretty print C@t{++} virtual function tables
9394 @cindex virtual functions (C@t{++}) display
9395 @cindex VTBL display
9396 Pretty print C@t{++} virtual function tables. The default is off.
9397 (The @code{vtbl} commands do not work on programs compiled with the HP
9398 ANSI C@t{++} compiler (@code{aCC}).)
9400 @item set print vtbl off
9401 Do not pretty print C@t{++} virtual function tables.
9403 @item show print vtbl
9404 Show whether C@t{++} virtual function tables are pretty printed, or not.
9407 @node Pretty Printing
9408 @section Pretty Printing
9410 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9411 Python code. It greatly simplifies the display of complex objects. This
9412 mechanism works for both MI and the CLI.
9415 * Pretty-Printer Introduction:: Introduction to pretty-printers
9416 * Pretty-Printer Example:: An example pretty-printer
9417 * Pretty-Printer Commands:: Pretty-printer commands
9420 @node Pretty-Printer Introduction
9421 @subsection Pretty-Printer Introduction
9423 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9424 registered for the value. If there is then @value{GDBN} invokes the
9425 pretty-printer to print the value. Otherwise the value is printed normally.
9427 Pretty-printers are normally named. This makes them easy to manage.
9428 The @samp{info pretty-printer} command will list all the installed
9429 pretty-printers with their names.
9430 If a pretty-printer can handle multiple data types, then its
9431 @dfn{subprinters} are the printers for the individual data types.
9432 Each such subprinter has its own name.
9433 The format of the name is @var{printer-name};@var{subprinter-name}.
9435 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9436 Typically they are automatically loaded and registered when the corresponding
9437 debug information is loaded, thus making them available without having to
9438 do anything special.
9440 There are three places where a pretty-printer can be registered.
9444 Pretty-printers registered globally are available when debugging
9448 Pretty-printers registered with a program space are available only
9449 when debugging that program.
9450 @xref{Progspaces In Python}, for more details on program spaces in Python.
9453 Pretty-printers registered with an objfile are loaded and unloaded
9454 with the corresponding objfile (e.g., shared library).
9455 @xref{Objfiles In Python}, for more details on objfiles in Python.
9458 @xref{Selecting Pretty-Printers}, for further information on how
9459 pretty-printers are selected,
9461 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9464 @node Pretty-Printer Example
9465 @subsection Pretty-Printer Example
9467 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9470 (@value{GDBP}) print s
9472 static npos = 4294967295,
9474 <std::allocator<char>> = @{
9475 <__gnu_cxx::new_allocator<char>> = @{
9476 <No data fields>@}, <No data fields>
9478 members of std::basic_string<char, std::char_traits<char>,
9479 std::allocator<char> >::_Alloc_hider:
9480 _M_p = 0x804a014 "abcd"
9485 With a pretty-printer for @code{std::string} only the contents are printed:
9488 (@value{GDBP}) print s
9492 @node Pretty-Printer Commands
9493 @subsection Pretty-Printer Commands
9494 @cindex pretty-printer commands
9497 @kindex info pretty-printer
9498 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9499 Print the list of installed pretty-printers.
9500 This includes disabled pretty-printers, which are marked as such.
9502 @var{object-regexp} is a regular expression matching the objects
9503 whose pretty-printers to list.
9504 Objects can be @code{global}, the program space's file
9505 (@pxref{Progspaces In Python}),
9506 and the object files within that program space (@pxref{Objfiles In Python}).
9507 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9508 looks up a printer from these three objects.
9510 @var{name-regexp} is a regular expression matching the name of the printers
9513 @kindex disable pretty-printer
9514 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9515 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9516 A disabled pretty-printer is not forgotten, it may be enabled again later.
9518 @kindex enable pretty-printer
9519 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9520 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9525 Suppose we have three pretty-printers installed: one from library1.so
9526 named @code{foo} that prints objects of type @code{foo}, and
9527 another from library2.so named @code{bar} that prints two types of objects,
9528 @code{bar1} and @code{bar2}.
9531 (gdb) info pretty-printer
9538 (gdb) info pretty-printer library2
9543 (gdb) disable pretty-printer library1
9545 2 of 3 printers enabled
9546 (gdb) info pretty-printer
9553 (gdb) disable pretty-printer library2 bar:bar1
9555 1 of 3 printers enabled
9556 (gdb) info pretty-printer library2
9563 (gdb) disable pretty-printer library2 bar
9565 0 of 3 printers enabled
9566 (gdb) info pretty-printer library2
9575 Note that for @code{bar} the entire printer can be disabled,
9576 as can each individual subprinter.
9579 @section Value History
9581 @cindex value history
9582 @cindex history of values printed by @value{GDBN}
9583 Values printed by the @code{print} command are saved in the @value{GDBN}
9584 @dfn{value history}. This allows you to refer to them in other expressions.
9585 Values are kept until the symbol table is re-read or discarded
9586 (for example with the @code{file} or @code{symbol-file} commands).
9587 When the symbol table changes, the value history is discarded,
9588 since the values may contain pointers back to the types defined in the
9593 @cindex history number
9594 The values printed are given @dfn{history numbers} by which you can
9595 refer to them. These are successive integers starting with one.
9596 @code{print} shows you the history number assigned to a value by
9597 printing @samp{$@var{num} = } before the value; here @var{num} is the
9600 To refer to any previous value, use @samp{$} followed by the value's
9601 history number. The way @code{print} labels its output is designed to
9602 remind you of this. Just @code{$} refers to the most recent value in
9603 the history, and @code{$$} refers to the value before that.
9604 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9605 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9606 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9608 For example, suppose you have just printed a pointer to a structure and
9609 want to see the contents of the structure. It suffices to type
9615 If you have a chain of structures where the component @code{next} points
9616 to the next one, you can print the contents of the next one with this:
9623 You can print successive links in the chain by repeating this
9624 command---which you can do by just typing @key{RET}.
9626 Note that the history records values, not expressions. If the value of
9627 @code{x} is 4 and you type these commands:
9635 then the value recorded in the value history by the @code{print} command
9636 remains 4 even though the value of @code{x} has changed.
9641 Print the last ten values in the value history, with their item numbers.
9642 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9643 values} does not change the history.
9645 @item show values @var{n}
9646 Print ten history values centered on history item number @var{n}.
9649 Print ten history values just after the values last printed. If no more
9650 values are available, @code{show values +} produces no display.
9653 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9654 same effect as @samp{show values +}.
9656 @node Convenience Vars
9657 @section Convenience Variables
9659 @cindex convenience variables
9660 @cindex user-defined variables
9661 @value{GDBN} provides @dfn{convenience variables} that you can use within
9662 @value{GDBN} to hold on to a value and refer to it later. These variables
9663 exist entirely within @value{GDBN}; they are not part of your program, and
9664 setting a convenience variable has no direct effect on further execution
9665 of your program. That is why you can use them freely.
9667 Convenience variables are prefixed with @samp{$}. Any name preceded by
9668 @samp{$} can be used for a convenience variable, unless it is one of
9669 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9670 (Value history references, in contrast, are @emph{numbers} preceded
9671 by @samp{$}. @xref{Value History, ,Value History}.)
9673 You can save a value in a convenience variable with an assignment
9674 expression, just as you would set a variable in your program.
9678 set $foo = *object_ptr
9682 would save in @code{$foo} the value contained in the object pointed to by
9685 Using a convenience variable for the first time creates it, but its
9686 value is @code{void} until you assign a new value. You can alter the
9687 value with another assignment at any time.
9689 Convenience variables have no fixed types. You can assign a convenience
9690 variable any type of value, including structures and arrays, even if
9691 that variable already has a value of a different type. The convenience
9692 variable, when used as an expression, has the type of its current value.
9695 @kindex show convenience
9696 @cindex show all user variables and functions
9697 @item show convenience
9698 Print a list of convenience variables used so far, and their values,
9699 as well as a list of the convenience functions.
9700 Abbreviated @code{show conv}.
9702 @kindex init-if-undefined
9703 @cindex convenience variables, initializing
9704 @item init-if-undefined $@var{variable} = @var{expression}
9705 Set a convenience variable if it has not already been set. This is useful
9706 for user-defined commands that keep some state. It is similar, in concept,
9707 to using local static variables with initializers in C (except that
9708 convenience variables are global). It can also be used to allow users to
9709 override default values used in a command script.
9711 If the variable is already defined then the expression is not evaluated so
9712 any side-effects do not occur.
9715 One of the ways to use a convenience variable is as a counter to be
9716 incremented or a pointer to be advanced. For example, to print
9717 a field from successive elements of an array of structures:
9721 print bar[$i++]->contents
9725 Repeat that command by typing @key{RET}.
9727 Some convenience variables are created automatically by @value{GDBN} and given
9728 values likely to be useful.
9731 @vindex $_@r{, convenience variable}
9733 The variable @code{$_} is automatically set by the @code{x} command to
9734 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9735 commands which provide a default address for @code{x} to examine also
9736 set @code{$_} to that address; these commands include @code{info line}
9737 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9738 except when set by the @code{x} command, in which case it is a pointer
9739 to the type of @code{$__}.
9741 @vindex $__@r{, convenience variable}
9743 The variable @code{$__} is automatically set by the @code{x} command
9744 to the value found in the last address examined. Its type is chosen
9745 to match the format in which the data was printed.
9748 @vindex $_exitcode@r{, convenience variable}
9749 The variable @code{$_exitcode} is automatically set to the exit code when
9750 the program being debugged terminates.
9753 The variable @code{$_exception} is set to the exception object being
9754 thrown at an exception-related catchpoint. @xref{Set Catchpoints}.
9757 @itemx $_probe_arg0@dots{}$_probe_arg11
9758 Arguments to a static probe. @xref{Static Probe Points}.
9761 @vindex $_sdata@r{, inspect, convenience variable}
9762 The variable @code{$_sdata} contains extra collected static tracepoint
9763 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9764 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9765 if extra static tracepoint data has not been collected.
9768 @vindex $_siginfo@r{, convenience variable}
9769 The variable @code{$_siginfo} contains extra signal information
9770 (@pxref{extra signal information}). Note that @code{$_siginfo}
9771 could be empty, if the application has not yet received any signals.
9772 For example, it will be empty before you execute the @code{run} command.
9775 @vindex $_tlb@r{, convenience variable}
9776 The variable @code{$_tlb} is automatically set when debugging
9777 applications running on MS-Windows in native mode or connected to
9778 gdbserver that supports the @code{qGetTIBAddr} request.
9779 @xref{General Query Packets}.
9780 This variable contains the address of the thread information block.
9784 On HP-UX systems, if you refer to a function or variable name that
9785 begins with a dollar sign, @value{GDBN} searches for a user or system
9786 name first, before it searches for a convenience variable.
9788 @node Convenience Funs
9789 @section Convenience Functions
9791 @cindex convenience functions
9792 @value{GDBN} also supplies some @dfn{convenience functions}. These
9793 have a syntax similar to convenience variables. A convenience
9794 function can be used in an expression just like an ordinary function;
9795 however, a convenience function is implemented internally to
9798 These functions require @value{GDBN} to be configured with
9799 @code{Python} support.
9803 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9804 @findex $_memeq@r{, convenience function}
9805 Returns one if the @var{length} bytes at the addresses given by
9806 @var{buf1} and @var{buf2} are equal.
9807 Otherwise it returns zero.
9809 @item $_regex(@var{str}, @var{regex})
9810 @findex $_regex@r{, convenience function}
9811 Returns one if the string @var{str} matches the regular expression
9812 @var{regex}. Otherwise it returns zero.
9813 The syntax of the regular expression is that specified by @code{Python}'s
9814 regular expression support.
9816 @item $_streq(@var{str1}, @var{str2})
9817 @findex $_streq@r{, convenience function}
9818 Returns one if the strings @var{str1} and @var{str2} are equal.
9819 Otherwise it returns zero.
9821 @item $_strlen(@var{str})
9822 @findex $_strlen@r{, convenience function}
9823 Returns the length of string @var{str}.
9827 @value{GDBN} provides the ability to list and get help on
9828 convenience functions.
9832 @kindex help function
9833 @cindex show all convenience functions
9834 Print a list of all convenience functions.
9841 You can refer to machine register contents, in expressions, as variables
9842 with names starting with @samp{$}. The names of registers are different
9843 for each machine; use @code{info registers} to see the names used on
9847 @kindex info registers
9848 @item info registers
9849 Print the names and values of all registers except floating-point
9850 and vector registers (in the selected stack frame).
9852 @kindex info all-registers
9853 @cindex floating point registers
9854 @item info all-registers
9855 Print the names and values of all registers, including floating-point
9856 and vector registers (in the selected stack frame).
9858 @item info registers @var{regname} @dots{}
9859 Print the @dfn{relativized} value of each specified register @var{regname}.
9860 As discussed in detail below, register values are normally relative to
9861 the selected stack frame. @var{regname} may be any register name valid on
9862 the machine you are using, with or without the initial @samp{$}.
9865 @cindex stack pointer register
9866 @cindex program counter register
9867 @cindex process status register
9868 @cindex frame pointer register
9869 @cindex standard registers
9870 @value{GDBN} has four ``standard'' register names that are available (in
9871 expressions) on most machines---whenever they do not conflict with an
9872 architecture's canonical mnemonics for registers. The register names
9873 @code{$pc} and @code{$sp} are used for the program counter register and
9874 the stack pointer. @code{$fp} is used for a register that contains a
9875 pointer to the current stack frame, and @code{$ps} is used for a
9876 register that contains the processor status. For example,
9877 you could print the program counter in hex with
9884 or print the instruction to be executed next with
9891 or add four to the stack pointer@footnote{This is a way of removing
9892 one word from the stack, on machines where stacks grow downward in
9893 memory (most machines, nowadays). This assumes that the innermost
9894 stack frame is selected; setting @code{$sp} is not allowed when other
9895 stack frames are selected. To pop entire frames off the stack,
9896 regardless of machine architecture, use @code{return};
9897 see @ref{Returning, ,Returning from a Function}.} with
9903 Whenever possible, these four standard register names are available on
9904 your machine even though the machine has different canonical mnemonics,
9905 so long as there is no conflict. The @code{info registers} command
9906 shows the canonical names. For example, on the SPARC, @code{info
9907 registers} displays the processor status register as @code{$psr} but you
9908 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9909 is an alias for the @sc{eflags} register.
9911 @value{GDBN} always considers the contents of an ordinary register as an
9912 integer when the register is examined in this way. Some machines have
9913 special registers which can hold nothing but floating point; these
9914 registers are considered to have floating point values. There is no way
9915 to refer to the contents of an ordinary register as floating point value
9916 (although you can @emph{print} it as a floating point value with
9917 @samp{print/f $@var{regname}}).
9919 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9920 means that the data format in which the register contents are saved by
9921 the operating system is not the same one that your program normally
9922 sees. For example, the registers of the 68881 floating point
9923 coprocessor are always saved in ``extended'' (raw) format, but all C
9924 programs expect to work with ``double'' (virtual) format. In such
9925 cases, @value{GDBN} normally works with the virtual format only (the format
9926 that makes sense for your program), but the @code{info registers} command
9927 prints the data in both formats.
9929 @cindex SSE registers (x86)
9930 @cindex MMX registers (x86)
9931 Some machines have special registers whose contents can be interpreted
9932 in several different ways. For example, modern x86-based machines
9933 have SSE and MMX registers that can hold several values packed
9934 together in several different formats. @value{GDBN} refers to such
9935 registers in @code{struct} notation:
9938 (@value{GDBP}) print $xmm1
9940 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9941 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9942 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9943 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9944 v4_int32 = @{0, 20657912, 11, 13@},
9945 v2_int64 = @{88725056443645952, 55834574859@},
9946 uint128 = 0x0000000d0000000b013b36f800000000
9951 To set values of such registers, you need to tell @value{GDBN} which
9952 view of the register you wish to change, as if you were assigning
9953 value to a @code{struct} member:
9956 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9959 Normally, register values are relative to the selected stack frame
9960 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9961 value that the register would contain if all stack frames farther in
9962 were exited and their saved registers restored. In order to see the
9963 true contents of hardware registers, you must select the innermost
9964 frame (with @samp{frame 0}).
9966 However, @value{GDBN} must deduce where registers are saved, from the machine
9967 code generated by your compiler. If some registers are not saved, or if
9968 @value{GDBN} is unable to locate the saved registers, the selected stack
9969 frame makes no difference.
9971 @node Floating Point Hardware
9972 @section Floating Point Hardware
9973 @cindex floating point
9975 Depending on the configuration, @value{GDBN} may be able to give
9976 you more information about the status of the floating point hardware.
9981 Display hardware-dependent information about the floating
9982 point unit. The exact contents and layout vary depending on the
9983 floating point chip. Currently, @samp{info float} is supported on
9984 the ARM and x86 machines.
9988 @section Vector Unit
9991 Depending on the configuration, @value{GDBN} may be able to give you
9992 more information about the status of the vector unit.
9997 Display information about the vector unit. The exact contents and
9998 layout vary depending on the hardware.
10001 @node OS Information
10002 @section Operating System Auxiliary Information
10003 @cindex OS information
10005 @value{GDBN} provides interfaces to useful OS facilities that can help
10006 you debug your program.
10008 @cindex auxiliary vector
10009 @cindex vector, auxiliary
10010 Some operating systems supply an @dfn{auxiliary vector} to programs at
10011 startup. This is akin to the arguments and environment that you
10012 specify for a program, but contains a system-dependent variety of
10013 binary values that tell system libraries important details about the
10014 hardware, operating system, and process. Each value's purpose is
10015 identified by an integer tag; the meanings are well-known but system-specific.
10016 Depending on the configuration and operating system facilities,
10017 @value{GDBN} may be able to show you this information. For remote
10018 targets, this functionality may further depend on the remote stub's
10019 support of the @samp{qXfer:auxv:read} packet, see
10020 @ref{qXfer auxiliary vector read}.
10025 Display the auxiliary vector of the inferior, which can be either a
10026 live process or a core dump file. @value{GDBN} prints each tag value
10027 numerically, and also shows names and text descriptions for recognized
10028 tags. Some values in the vector are numbers, some bit masks, and some
10029 pointers to strings or other data. @value{GDBN} displays each value in the
10030 most appropriate form for a recognized tag, and in hexadecimal for
10031 an unrecognized tag.
10034 On some targets, @value{GDBN} can access operating system-specific
10035 information and show it to you. The types of information available
10036 will differ depending on the type of operating system running on the
10037 target. The mechanism used to fetch the data is described in
10038 @ref{Operating System Information}. For remote targets, this
10039 functionality depends on the remote stub's support of the
10040 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
10044 @item info os @var{infotype}
10046 Display OS information of the requested type.
10048 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
10050 @anchor{linux info os infotypes}
10052 @kindex info os processes
10054 Display the list of processes on the target. For each process,
10055 @value{GDBN} prints the process identifier, the name of the user, the
10056 command corresponding to the process, and the list of processor cores
10057 that the process is currently running on. (To understand what these
10058 properties mean, for this and the following info types, please consult
10059 the general @sc{gnu}/Linux documentation.)
10061 @kindex info os procgroups
10063 Display the list of process groups on the target. For each process,
10064 @value{GDBN} prints the identifier of the process group that it belongs
10065 to, the command corresponding to the process group leader, the process
10066 identifier, and the command line of the process. The list is sorted
10067 first by the process group identifier, then by the process identifier,
10068 so that processes belonging to the same process group are grouped together
10069 and the process group leader is listed first.
10071 @kindex info os threads
10073 Display the list of threads running on the target. For each thread,
10074 @value{GDBN} prints the identifier of the process that the thread
10075 belongs to, the command of the process, the thread identifier, and the
10076 processor core that it is currently running on. The main thread of a
10077 process is not listed.
10079 @kindex info os files
10081 Display the list of open file descriptors on the target. For each
10082 file descriptor, @value{GDBN} prints the identifier of the process
10083 owning the descriptor, the command of the owning process, the value
10084 of the descriptor, and the target of the descriptor.
10086 @kindex info os sockets
10088 Display the list of Internet-domain sockets on the target. For each
10089 socket, @value{GDBN} prints the address and port of the local and
10090 remote endpoints, the current state of the connection, the creator of
10091 the socket, the IP address family of the socket, and the type of the
10094 @kindex info os shm
10096 Display the list of all System V shared-memory regions on the target.
10097 For each shared-memory region, @value{GDBN} prints the region key,
10098 the shared-memory identifier, the access permissions, the size of the
10099 region, the process that created the region, the process that last
10100 attached to or detached from the region, the current number of live
10101 attaches to the region, and the times at which the region was last
10102 attached to, detach from, and changed.
10104 @kindex info os semaphores
10106 Display the list of all System V semaphore sets on the target. For each
10107 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
10108 set identifier, the access permissions, the number of semaphores in the
10109 set, the user and group of the owner and creator of the semaphore set,
10110 and the times at which the semaphore set was operated upon and changed.
10112 @kindex info os msg
10114 Display the list of all System V message queues on the target. For each
10115 message queue, @value{GDBN} prints the message queue key, the message
10116 queue identifier, the access permissions, the current number of bytes
10117 on the queue, the current number of messages on the queue, the processes
10118 that last sent and received a message on the queue, the user and group
10119 of the owner and creator of the message queue, the times at which a
10120 message was last sent and received on the queue, and the time at which
10121 the message queue was last changed.
10123 @kindex info os modules
10125 Display the list of all loaded kernel modules on the target. For each
10126 module, @value{GDBN} prints the module name, the size of the module in
10127 bytes, the number of times the module is used, the dependencies of the
10128 module, the status of the module, and the address of the loaded module
10133 If @var{infotype} is omitted, then list the possible values for
10134 @var{infotype} and the kind of OS information available for each
10135 @var{infotype}. If the target does not return a list of possible
10136 types, this command will report an error.
10139 @node Memory Region Attributes
10140 @section Memory Region Attributes
10141 @cindex memory region attributes
10143 @dfn{Memory region attributes} allow you to describe special handling
10144 required by regions of your target's memory. @value{GDBN} uses
10145 attributes to determine whether to allow certain types of memory
10146 accesses; whether to use specific width accesses; and whether to cache
10147 target memory. By default the description of memory regions is
10148 fetched from the target (if the current target supports this), but the
10149 user can override the fetched regions.
10151 Defined memory regions can be individually enabled and disabled. When a
10152 memory region is disabled, @value{GDBN} uses the default attributes when
10153 accessing memory in that region. Similarly, if no memory regions have
10154 been defined, @value{GDBN} uses the default attributes when accessing
10157 When a memory region is defined, it is given a number to identify it;
10158 to enable, disable, or remove a memory region, you specify that number.
10162 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
10163 Define a memory region bounded by @var{lower} and @var{upper} with
10164 attributes @var{attributes}@dots{}, and add it to the list of regions
10165 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
10166 case: it is treated as the target's maximum memory address.
10167 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
10170 Discard any user changes to the memory regions and use target-supplied
10171 regions, if available, or no regions if the target does not support.
10174 @item delete mem @var{nums}@dots{}
10175 Remove memory regions @var{nums}@dots{} from the list of regions
10176 monitored by @value{GDBN}.
10178 @kindex disable mem
10179 @item disable mem @var{nums}@dots{}
10180 Disable monitoring of memory regions @var{nums}@dots{}.
10181 A disabled memory region is not forgotten.
10182 It may be enabled again later.
10185 @item enable mem @var{nums}@dots{}
10186 Enable monitoring of memory regions @var{nums}@dots{}.
10190 Print a table of all defined memory regions, with the following columns
10194 @item Memory Region Number
10195 @item Enabled or Disabled.
10196 Enabled memory regions are marked with @samp{y}.
10197 Disabled memory regions are marked with @samp{n}.
10200 The address defining the inclusive lower bound of the memory region.
10203 The address defining the exclusive upper bound of the memory region.
10206 The list of attributes set for this memory region.
10211 @subsection Attributes
10213 @subsubsection Memory Access Mode
10214 The access mode attributes set whether @value{GDBN} may make read or
10215 write accesses to a memory region.
10217 While these attributes prevent @value{GDBN} from performing invalid
10218 memory accesses, they do nothing to prevent the target system, I/O DMA,
10219 etc.@: from accessing memory.
10223 Memory is read only.
10225 Memory is write only.
10227 Memory is read/write. This is the default.
10230 @subsubsection Memory Access Size
10231 The access size attribute tells @value{GDBN} to use specific sized
10232 accesses in the memory region. Often memory mapped device registers
10233 require specific sized accesses. If no access size attribute is
10234 specified, @value{GDBN} may use accesses of any size.
10238 Use 8 bit memory accesses.
10240 Use 16 bit memory accesses.
10242 Use 32 bit memory accesses.
10244 Use 64 bit memory accesses.
10247 @c @subsubsection Hardware/Software Breakpoints
10248 @c The hardware/software breakpoint attributes set whether @value{GDBN}
10249 @c will use hardware or software breakpoints for the internal breakpoints
10250 @c used by the step, next, finish, until, etc. commands.
10254 @c Always use hardware breakpoints
10255 @c @item swbreak (default)
10258 @subsubsection Data Cache
10259 The data cache attributes set whether @value{GDBN} will cache target
10260 memory. While this generally improves performance by reducing debug
10261 protocol overhead, it can lead to incorrect results because @value{GDBN}
10262 does not know about volatile variables or memory mapped device
10267 Enable @value{GDBN} to cache target memory.
10269 Disable @value{GDBN} from caching target memory. This is the default.
10272 @subsection Memory Access Checking
10273 @value{GDBN} can be instructed to refuse accesses to memory that is
10274 not explicitly described. This can be useful if accessing such
10275 regions has undesired effects for a specific target, or to provide
10276 better error checking. The following commands control this behaviour.
10279 @kindex set mem inaccessible-by-default
10280 @item set mem inaccessible-by-default [on|off]
10281 If @code{on} is specified, make @value{GDBN} treat memory not
10282 explicitly described by the memory ranges as non-existent and refuse accesses
10283 to such memory. The checks are only performed if there's at least one
10284 memory range defined. If @code{off} is specified, make @value{GDBN}
10285 treat the memory not explicitly described by the memory ranges as RAM.
10286 The default value is @code{on}.
10287 @kindex show mem inaccessible-by-default
10288 @item show mem inaccessible-by-default
10289 Show the current handling of accesses to unknown memory.
10293 @c @subsubsection Memory Write Verification
10294 @c The memory write verification attributes set whether @value{GDBN}
10295 @c will re-reads data after each write to verify the write was successful.
10299 @c @item noverify (default)
10302 @node Dump/Restore Files
10303 @section Copy Between Memory and a File
10304 @cindex dump/restore files
10305 @cindex append data to a file
10306 @cindex dump data to a file
10307 @cindex restore data from a file
10309 You can use the commands @code{dump}, @code{append}, and
10310 @code{restore} to copy data between target memory and a file. The
10311 @code{dump} and @code{append} commands write data to a file, and the
10312 @code{restore} command reads data from a file back into the inferior's
10313 memory. Files may be in binary, Motorola S-record, Intel hex, or
10314 Tektronix Hex format; however, @value{GDBN} can only append to binary
10320 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10321 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10322 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10323 or the value of @var{expr}, to @var{filename} in the given format.
10325 The @var{format} parameter may be any one of:
10332 Motorola S-record format.
10334 Tektronix Hex format.
10337 @value{GDBN} uses the same definitions of these formats as the
10338 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10339 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10343 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10344 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10345 Append the contents of memory from @var{start_addr} to @var{end_addr},
10346 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10347 (@value{GDBN} can only append data to files in raw binary form.)
10350 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10351 Restore the contents of file @var{filename} into memory. The
10352 @code{restore} command can automatically recognize any known @sc{bfd}
10353 file format, except for raw binary. To restore a raw binary file you
10354 must specify the optional keyword @code{binary} after the filename.
10356 If @var{bias} is non-zero, its value will be added to the addresses
10357 contained in the file. Binary files always start at address zero, so
10358 they will be restored at address @var{bias}. Other bfd files have
10359 a built-in location; they will be restored at offset @var{bias}
10360 from that location.
10362 If @var{start} and/or @var{end} are non-zero, then only data between
10363 file offset @var{start} and file offset @var{end} will be restored.
10364 These offsets are relative to the addresses in the file, before
10365 the @var{bias} argument is applied.
10369 @node Core File Generation
10370 @section How to Produce a Core File from Your Program
10371 @cindex dump core from inferior
10373 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10374 image of a running process and its process status (register values
10375 etc.). Its primary use is post-mortem debugging of a program that
10376 crashed while it ran outside a debugger. A program that crashes
10377 automatically produces a core file, unless this feature is disabled by
10378 the user. @xref{Files}, for information on invoking @value{GDBN} in
10379 the post-mortem debugging mode.
10381 Occasionally, you may wish to produce a core file of the program you
10382 are debugging in order to preserve a snapshot of its state.
10383 @value{GDBN} has a special command for that.
10387 @kindex generate-core-file
10388 @item generate-core-file [@var{file}]
10389 @itemx gcore [@var{file}]
10390 Produce a core dump of the inferior process. The optional argument
10391 @var{file} specifies the file name where to put the core dump. If not
10392 specified, the file name defaults to @file{core.@var{pid}}, where
10393 @var{pid} is the inferior process ID.
10395 Note that this command is implemented only for some systems (as of
10396 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10399 @node Character Sets
10400 @section Character Sets
10401 @cindex character sets
10403 @cindex translating between character sets
10404 @cindex host character set
10405 @cindex target character set
10407 If the program you are debugging uses a different character set to
10408 represent characters and strings than the one @value{GDBN} uses itself,
10409 @value{GDBN} can automatically translate between the character sets for
10410 you. The character set @value{GDBN} uses we call the @dfn{host
10411 character set}; the one the inferior program uses we call the
10412 @dfn{target character set}.
10414 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10415 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10416 remote protocol (@pxref{Remote Debugging}) to debug a program
10417 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10418 then the host character set is Latin-1, and the target character set is
10419 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10420 target-charset EBCDIC-US}, then @value{GDBN} translates between
10421 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10422 character and string literals in expressions.
10424 @value{GDBN} has no way to automatically recognize which character set
10425 the inferior program uses; you must tell it, using the @code{set
10426 target-charset} command, described below.
10428 Here are the commands for controlling @value{GDBN}'s character set
10432 @item set target-charset @var{charset}
10433 @kindex set target-charset
10434 Set the current target character set to @var{charset}. To display the
10435 list of supported target character sets, type
10436 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10438 @item set host-charset @var{charset}
10439 @kindex set host-charset
10440 Set the current host character set to @var{charset}.
10442 By default, @value{GDBN} uses a host character set appropriate to the
10443 system it is running on; you can override that default using the
10444 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10445 automatically determine the appropriate host character set. In this
10446 case, @value{GDBN} uses @samp{UTF-8}.
10448 @value{GDBN} can only use certain character sets as its host character
10449 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10450 @value{GDBN} will list the host character sets it supports.
10452 @item set charset @var{charset}
10453 @kindex set charset
10454 Set the current host and target character sets to @var{charset}. As
10455 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10456 @value{GDBN} will list the names of the character sets that can be used
10457 for both host and target.
10460 @kindex show charset
10461 Show the names of the current host and target character sets.
10463 @item show host-charset
10464 @kindex show host-charset
10465 Show the name of the current host character set.
10467 @item show target-charset
10468 @kindex show target-charset
10469 Show the name of the current target character set.
10471 @item set target-wide-charset @var{charset}
10472 @kindex set target-wide-charset
10473 Set the current target's wide character set to @var{charset}. This is
10474 the character set used by the target's @code{wchar_t} type. To
10475 display the list of supported wide character sets, type
10476 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10478 @item show target-wide-charset
10479 @kindex show target-wide-charset
10480 Show the name of the current target's wide character set.
10483 Here is an example of @value{GDBN}'s character set support in action.
10484 Assume that the following source code has been placed in the file
10485 @file{charset-test.c}:
10491 = @{72, 101, 108, 108, 111, 44, 32, 119,
10492 111, 114, 108, 100, 33, 10, 0@};
10493 char ibm1047_hello[]
10494 = @{200, 133, 147, 147, 150, 107, 64, 166,
10495 150, 153, 147, 132, 90, 37, 0@};
10499 printf ("Hello, world!\n");
10503 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10504 containing the string @samp{Hello, world!} followed by a newline,
10505 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10507 We compile the program, and invoke the debugger on it:
10510 $ gcc -g charset-test.c -o charset-test
10511 $ gdb -nw charset-test
10512 GNU gdb 2001-12-19-cvs
10513 Copyright 2001 Free Software Foundation, Inc.
10518 We can use the @code{show charset} command to see what character sets
10519 @value{GDBN} is currently using to interpret and display characters and
10523 (@value{GDBP}) show charset
10524 The current host and target character set is `ISO-8859-1'.
10528 For the sake of printing this manual, let's use @sc{ascii} as our
10529 initial character set:
10531 (@value{GDBP}) set charset ASCII
10532 (@value{GDBP}) show charset
10533 The current host and target character set is `ASCII'.
10537 Let's assume that @sc{ascii} is indeed the correct character set for our
10538 host system --- in other words, let's assume that if @value{GDBN} prints
10539 characters using the @sc{ascii} character set, our terminal will display
10540 them properly. Since our current target character set is also
10541 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10544 (@value{GDBP}) print ascii_hello
10545 $1 = 0x401698 "Hello, world!\n"
10546 (@value{GDBP}) print ascii_hello[0]
10551 @value{GDBN} uses the target character set for character and string
10552 literals you use in expressions:
10555 (@value{GDBP}) print '+'
10560 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10563 @value{GDBN} relies on the user to tell it which character set the
10564 target program uses. If we print @code{ibm1047_hello} while our target
10565 character set is still @sc{ascii}, we get jibberish:
10568 (@value{GDBP}) print ibm1047_hello
10569 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10570 (@value{GDBP}) print ibm1047_hello[0]
10575 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10576 @value{GDBN} tells us the character sets it supports:
10579 (@value{GDBP}) set target-charset
10580 ASCII EBCDIC-US IBM1047 ISO-8859-1
10581 (@value{GDBP}) set target-charset
10584 We can select @sc{ibm1047} as our target character set, and examine the
10585 program's strings again. Now the @sc{ascii} string is wrong, but
10586 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10587 target character set, @sc{ibm1047}, to the host character set,
10588 @sc{ascii}, and they display correctly:
10591 (@value{GDBP}) set target-charset IBM1047
10592 (@value{GDBP}) show charset
10593 The current host character set is `ASCII'.
10594 The current target character set is `IBM1047'.
10595 (@value{GDBP}) print ascii_hello
10596 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10597 (@value{GDBP}) print ascii_hello[0]
10599 (@value{GDBP}) print ibm1047_hello
10600 $8 = 0x4016a8 "Hello, world!\n"
10601 (@value{GDBP}) print ibm1047_hello[0]
10606 As above, @value{GDBN} uses the target character set for character and
10607 string literals you use in expressions:
10610 (@value{GDBP}) print '+'
10615 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10618 @node Caching Remote Data
10619 @section Caching Data of Remote Targets
10620 @cindex caching data of remote targets
10622 @value{GDBN} caches data exchanged between the debugger and a
10623 remote target (@pxref{Remote Debugging}). Such caching generally improves
10624 performance, because it reduces the overhead of the remote protocol by
10625 bundling memory reads and writes into large chunks. Unfortunately, simply
10626 caching everything would lead to incorrect results, since @value{GDBN}
10627 does not necessarily know anything about volatile values, memory-mapped I/O
10628 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10629 memory can be changed @emph{while} a gdb command is executing.
10630 Therefore, by default, @value{GDBN} only caches data
10631 known to be on the stack@footnote{In non-stop mode, it is moderately
10632 rare for a running thread to modify the stack of a stopped thread
10633 in a way that would interfere with a backtrace, and caching of
10634 stack reads provides a significant speed up of remote backtraces.}.
10635 Other regions of memory can be explicitly marked as
10636 cacheable; see @pxref{Memory Region Attributes}.
10639 @kindex set remotecache
10640 @item set remotecache on
10641 @itemx set remotecache off
10642 This option no longer does anything; it exists for compatibility
10645 @kindex show remotecache
10646 @item show remotecache
10647 Show the current state of the obsolete remotecache flag.
10649 @kindex set stack-cache
10650 @item set stack-cache on
10651 @itemx set stack-cache off
10652 Enable or disable caching of stack accesses. When @code{ON}, use
10653 caching. By default, this option is @code{ON}.
10655 @kindex show stack-cache
10656 @item show stack-cache
10657 Show the current state of data caching for memory accesses.
10659 @kindex info dcache
10660 @item info dcache @r{[}line@r{]}
10661 Print the information about the data cache performance. The
10662 information displayed includes the dcache width and depth, and for
10663 each cache line, its number, address, and how many times it was
10664 referenced. This command is useful for debugging the data cache
10667 If a line number is specified, the contents of that line will be
10670 @item set dcache size @var{size}
10671 @cindex dcache size
10672 @kindex set dcache size
10673 Set maximum number of entries in dcache (dcache depth above).
10675 @item set dcache line-size @var{line-size}
10676 @cindex dcache line-size
10677 @kindex set dcache line-size
10678 Set number of bytes each dcache entry caches (dcache width above).
10679 Must be a power of 2.
10681 @item show dcache size
10682 @kindex show dcache size
10683 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10685 @item show dcache line-size
10686 @kindex show dcache line-size
10687 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10691 @node Searching Memory
10692 @section Search Memory
10693 @cindex searching memory
10695 Memory can be searched for a particular sequence of bytes with the
10696 @code{find} command.
10700 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10701 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10702 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10703 etc. The search begins at address @var{start_addr} and continues for either
10704 @var{len} bytes or through to @var{end_addr} inclusive.
10707 @var{s} and @var{n} are optional parameters.
10708 They may be specified in either order, apart or together.
10711 @item @var{s}, search query size
10712 The size of each search query value.
10718 halfwords (two bytes)
10722 giant words (eight bytes)
10725 All values are interpreted in the current language.
10726 This means, for example, that if the current source language is C/C@t{++}
10727 then searching for the string ``hello'' includes the trailing '\0'.
10729 If the value size is not specified, it is taken from the
10730 value's type in the current language.
10731 This is useful when one wants to specify the search
10732 pattern as a mixture of types.
10733 Note that this means, for example, that in the case of C-like languages
10734 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10735 which is typically four bytes.
10737 @item @var{n}, maximum number of finds
10738 The maximum number of matches to print. The default is to print all finds.
10741 You can use strings as search values. Quote them with double-quotes
10743 The string value is copied into the search pattern byte by byte,
10744 regardless of the endianness of the target and the size specification.
10746 The address of each match found is printed as well as a count of the
10747 number of matches found.
10749 The address of the last value found is stored in convenience variable
10751 A count of the number of matches is stored in @samp{$numfound}.
10753 For example, if stopped at the @code{printf} in this function:
10759 static char hello[] = "hello-hello";
10760 static struct @{ char c; short s; int i; @}
10761 __attribute__ ((packed)) mixed
10762 = @{ 'c', 0x1234, 0x87654321 @};
10763 printf ("%s\n", hello);
10768 you get during debugging:
10771 (gdb) find &hello[0], +sizeof(hello), "hello"
10772 0x804956d <hello.1620+6>
10774 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10775 0x8049567 <hello.1620>
10776 0x804956d <hello.1620+6>
10778 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10779 0x8049567 <hello.1620>
10781 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10782 0x8049560 <mixed.1625>
10784 (gdb) print $numfound
10787 $2 = (void *) 0x8049560
10790 @node Optimized Code
10791 @chapter Debugging Optimized Code
10792 @cindex optimized code, debugging
10793 @cindex debugging optimized code
10795 Almost all compilers support optimization. With optimization
10796 disabled, the compiler generates assembly code that corresponds
10797 directly to your source code, in a simplistic way. As the compiler
10798 applies more powerful optimizations, the generated assembly code
10799 diverges from your original source code. With help from debugging
10800 information generated by the compiler, @value{GDBN} can map from
10801 the running program back to constructs from your original source.
10803 @value{GDBN} is more accurate with optimization disabled. If you
10804 can recompile without optimization, it is easier to follow the
10805 progress of your program during debugging. But, there are many cases
10806 where you may need to debug an optimized version.
10808 When you debug a program compiled with @samp{-g -O}, remember that the
10809 optimizer has rearranged your code; the debugger shows you what is
10810 really there. Do not be too surprised when the execution path does not
10811 exactly match your source file! An extreme example: if you define a
10812 variable, but never use it, @value{GDBN} never sees that
10813 variable---because the compiler optimizes it out of existence.
10815 Some things do not work as well with @samp{-g -O} as with just
10816 @samp{-g}, particularly on machines with instruction scheduling. If in
10817 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10818 please report it to us as a bug (including a test case!).
10819 @xref{Variables}, for more information about debugging optimized code.
10822 * Inline Functions:: How @value{GDBN} presents inlining
10823 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10826 @node Inline Functions
10827 @section Inline Functions
10828 @cindex inline functions, debugging
10830 @dfn{Inlining} is an optimization that inserts a copy of the function
10831 body directly at each call site, instead of jumping to a shared
10832 routine. @value{GDBN} displays inlined functions just like
10833 non-inlined functions. They appear in backtraces. You can view their
10834 arguments and local variables, step into them with @code{step}, skip
10835 them with @code{next}, and escape from them with @code{finish}.
10836 You can check whether a function was inlined by using the
10837 @code{info frame} command.
10839 For @value{GDBN} to support inlined functions, the compiler must
10840 record information about inlining in the debug information ---
10841 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10842 other compilers do also. @value{GDBN} only supports inlined functions
10843 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10844 do not emit two required attributes (@samp{DW_AT_call_file} and
10845 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10846 function calls with earlier versions of @value{NGCC}. It instead
10847 displays the arguments and local variables of inlined functions as
10848 local variables in the caller.
10850 The body of an inlined function is directly included at its call site;
10851 unlike a non-inlined function, there are no instructions devoted to
10852 the call. @value{GDBN} still pretends that the call site and the
10853 start of the inlined function are different instructions. Stepping to
10854 the call site shows the call site, and then stepping again shows
10855 the first line of the inlined function, even though no additional
10856 instructions are executed.
10858 This makes source-level debugging much clearer; you can see both the
10859 context of the call and then the effect of the call. Only stepping by
10860 a single instruction using @code{stepi} or @code{nexti} does not do
10861 this; single instruction steps always show the inlined body.
10863 There are some ways that @value{GDBN} does not pretend that inlined
10864 function calls are the same as normal calls:
10868 Setting breakpoints at the call site of an inlined function may not
10869 work, because the call site does not contain any code. @value{GDBN}
10870 may incorrectly move the breakpoint to the next line of the enclosing
10871 function, after the call. This limitation will be removed in a future
10872 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10873 or inside the inlined function instead.
10876 @value{GDBN} cannot locate the return value of inlined calls after
10877 using the @code{finish} command. This is a limitation of compiler-generated
10878 debugging information; after @code{finish}, you can step to the next line
10879 and print a variable where your program stored the return value.
10883 @node Tail Call Frames
10884 @section Tail Call Frames
10885 @cindex tail call frames, debugging
10887 Function @code{B} can call function @code{C} in its very last statement. In
10888 unoptimized compilation the call of @code{C} is immediately followed by return
10889 instruction at the end of @code{B} code. Optimizing compiler may replace the
10890 call and return in function @code{B} into one jump to function @code{C}
10891 instead. Such use of a jump instruction is called @dfn{tail call}.
10893 During execution of function @code{C}, there will be no indication in the
10894 function call stack frames that it was tail-called from @code{B}. If function
10895 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10896 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10897 some cases @value{GDBN} can determine that @code{C} was tail-called from
10898 @code{B}, and it will then create fictitious call frame for that, with the
10899 return address set up as if @code{B} called @code{C} normally.
10901 This functionality is currently supported only by DWARF 2 debugging format and
10902 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10903 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10906 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10907 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10911 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10913 Stack level 1, frame at 0x7fffffffda30:
10914 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10915 tail call frame, caller of frame at 0x7fffffffda30
10916 source language c++.
10917 Arglist at unknown address.
10918 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10921 The detection of all the possible code path executions can find them ambiguous.
10922 There is no execution history stored (possible @ref{Reverse Execution} is never
10923 used for this purpose) and the last known caller could have reached the known
10924 callee by multiple different jump sequences. In such case @value{GDBN} still
10925 tries to show at least all the unambiguous top tail callers and all the
10926 unambiguous bottom tail calees, if any.
10929 @anchor{set debug entry-values}
10930 @item set debug entry-values
10931 @kindex set debug entry-values
10932 When set to on, enables printing of analysis messages for both frame argument
10933 values at function entry and tail calls. It will show all the possible valid
10934 tail calls code paths it has considered. It will also print the intersection
10935 of them with the final unambiguous (possibly partial or even empty) code path
10938 @item show debug entry-values
10939 @kindex show debug entry-values
10940 Show the current state of analysis messages printing for both frame argument
10941 values at function entry and tail calls.
10944 The analysis messages for tail calls can for example show why the virtual tail
10945 call frame for function @code{c} has not been recognized (due to the indirect
10946 reference by variable @code{x}):
10949 static void __attribute__((noinline, noclone)) c (void);
10950 void (*x) (void) = c;
10951 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10952 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10953 int main (void) @{ x (); return 0; @}
10955 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10956 DW_TAG_GNU_call_site 0x40039a in main
10958 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10961 #1 0x000000000040039a in main () at t.c:5
10964 Another possibility is an ambiguous virtual tail call frames resolution:
10968 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10969 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10970 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10971 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10972 static void __attribute__((noinline, noclone)) b (void)
10973 @{ if (i) c (); else e (); @}
10974 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10975 int main (void) @{ a (); return 0; @}
10977 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10978 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10979 tailcall: reduced: 0x4004d2(a) |
10982 #1 0x00000000004004d2 in a () at t.c:8
10983 #2 0x0000000000400395 in main () at t.c:9
10986 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10987 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10989 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10990 @ifset HAVE_MAKEINFO_CLICK
10991 @set ARROW @click{}
10992 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10993 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10995 @ifclear HAVE_MAKEINFO_CLICK
10997 @set CALLSEQ1B @value{CALLSEQ1A}
10998 @set CALLSEQ2B @value{CALLSEQ2A}
11001 Frames #0 and #2 are real, #1 is a virtual tail call frame.
11002 The code can have possible execution paths @value{CALLSEQ1B} or
11003 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
11005 @code{initial:} state shows some random possible calling sequence @value{GDBN}
11006 has found. It then finds another possible calling sequcen - that one is
11007 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
11008 printed as the @code{reduced:} calling sequence. That one could have many
11009 futher @code{compare:} and @code{reduced:} statements as long as there remain
11010 any non-ambiguous sequence entries.
11012 For the frame of function @code{b} in both cases there are different possible
11013 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
11014 also ambigous. The only non-ambiguous frame is the one for function @code{a},
11015 therefore this one is displayed to the user while the ambiguous frames are
11018 There can be also reasons why printing of frame argument values at function
11023 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
11024 static void __attribute__((noinline, noclone)) a (int i);
11025 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
11026 static void __attribute__((noinline, noclone)) a (int i)
11027 @{ if (i) b (i - 1); else c (0); @}
11028 int main (void) @{ a (5); return 0; @}
11031 #0 c (i=i@@entry=0) at t.c:2
11032 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
11033 function "a" at 0x400420 can call itself via tail calls
11034 i=<optimized out>) at t.c:6
11035 #2 0x000000000040036e in main () at t.c:7
11038 @value{GDBN} cannot find out from the inferior state if and how many times did
11039 function @code{a} call itself (via function @code{b}) as these calls would be
11040 tail calls. Such tail calls would modify thue @code{i} variable, therefore
11041 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
11042 prints @code{<optimized out>} instead.
11045 @chapter C Preprocessor Macros
11047 Some languages, such as C and C@t{++}, provide a way to define and invoke
11048 ``preprocessor macros'' which expand into strings of tokens.
11049 @value{GDBN} can evaluate expressions containing macro invocations, show
11050 the result of macro expansion, and show a macro's definition, including
11051 where it was defined.
11053 You may need to compile your program specially to provide @value{GDBN}
11054 with information about preprocessor macros. Most compilers do not
11055 include macros in their debugging information, even when you compile
11056 with the @option{-g} flag. @xref{Compilation}.
11058 A program may define a macro at one point, remove that definition later,
11059 and then provide a different definition after that. Thus, at different
11060 points in the program, a macro may have different definitions, or have
11061 no definition at all. If there is a current stack frame, @value{GDBN}
11062 uses the macros in scope at that frame's source code line. Otherwise,
11063 @value{GDBN} uses the macros in scope at the current listing location;
11066 Whenever @value{GDBN} evaluates an expression, it always expands any
11067 macro invocations present in the expression. @value{GDBN} also provides
11068 the following commands for working with macros explicitly.
11072 @kindex macro expand
11073 @cindex macro expansion, showing the results of preprocessor
11074 @cindex preprocessor macro expansion, showing the results of
11075 @cindex expanding preprocessor macros
11076 @item macro expand @var{expression}
11077 @itemx macro exp @var{expression}
11078 Show the results of expanding all preprocessor macro invocations in
11079 @var{expression}. Since @value{GDBN} simply expands macros, but does
11080 not parse the result, @var{expression} need not be a valid expression;
11081 it can be any string of tokens.
11084 @item macro expand-once @var{expression}
11085 @itemx macro exp1 @var{expression}
11086 @cindex expand macro once
11087 @i{(This command is not yet implemented.)} Show the results of
11088 expanding those preprocessor macro invocations that appear explicitly in
11089 @var{expression}. Macro invocations appearing in that expansion are
11090 left unchanged. This command allows you to see the effect of a
11091 particular macro more clearly, without being confused by further
11092 expansions. Since @value{GDBN} simply expands macros, but does not
11093 parse the result, @var{expression} need not be a valid expression; it
11094 can be any string of tokens.
11097 @cindex macro definition, showing
11098 @cindex definition of a macro, showing
11099 @cindex macros, from debug info
11100 @item info macro [-a|-all] [--] @var{macro}
11101 Show the current definition or all definitions of the named @var{macro},
11102 and describe the source location or compiler command-line where that
11103 definition was established. The optional double dash is to signify the end of
11104 argument processing and the beginning of @var{macro} for non C-like macros where
11105 the macro may begin with a hyphen.
11107 @kindex info macros
11108 @item info macros @var{linespec}
11109 Show all macro definitions that are in effect at the location specified
11110 by @var{linespec}, and describe the source location or compiler
11111 command-line where those definitions were established.
11113 @kindex macro define
11114 @cindex user-defined macros
11115 @cindex defining macros interactively
11116 @cindex macros, user-defined
11117 @item macro define @var{macro} @var{replacement-list}
11118 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
11119 Introduce a definition for a preprocessor macro named @var{macro},
11120 invocations of which are replaced by the tokens given in
11121 @var{replacement-list}. The first form of this command defines an
11122 ``object-like'' macro, which takes no arguments; the second form
11123 defines a ``function-like'' macro, which takes the arguments given in
11126 A definition introduced by this command is in scope in every
11127 expression evaluated in @value{GDBN}, until it is removed with the
11128 @code{macro undef} command, described below. The definition overrides
11129 all definitions for @var{macro} present in the program being debugged,
11130 as well as any previous user-supplied definition.
11132 @kindex macro undef
11133 @item macro undef @var{macro}
11134 Remove any user-supplied definition for the macro named @var{macro}.
11135 This command only affects definitions provided with the @code{macro
11136 define} command, described above; it cannot remove definitions present
11137 in the program being debugged.
11141 List all the macros defined using the @code{macro define} command.
11144 @cindex macros, example of debugging with
11145 Here is a transcript showing the above commands in action. First, we
11146 show our source files:
11151 #include "sample.h"
11154 #define ADD(x) (M + x)
11159 printf ("Hello, world!\n");
11161 printf ("We're so creative.\n");
11163 printf ("Goodbye, world!\n");
11170 Now, we compile the program using the @sc{gnu} C compiler,
11171 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
11172 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
11173 and @option{-gdwarf-4}; we recommend always choosing the most recent
11174 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
11175 includes information about preprocessor macros in the debugging
11179 $ gcc -gdwarf-2 -g3 sample.c -o sample
11183 Now, we start @value{GDBN} on our sample program:
11187 GNU gdb 2002-05-06-cvs
11188 Copyright 2002 Free Software Foundation, Inc.
11189 GDB is free software, @dots{}
11193 We can expand macros and examine their definitions, even when the
11194 program is not running. @value{GDBN} uses the current listing position
11195 to decide which macro definitions are in scope:
11198 (@value{GDBP}) list main
11201 5 #define ADD(x) (M + x)
11206 10 printf ("Hello, world!\n");
11208 12 printf ("We're so creative.\n");
11209 (@value{GDBP}) info macro ADD
11210 Defined at /home/jimb/gdb/macros/play/sample.c:5
11211 #define ADD(x) (M + x)
11212 (@value{GDBP}) info macro Q
11213 Defined at /home/jimb/gdb/macros/play/sample.h:1
11214 included at /home/jimb/gdb/macros/play/sample.c:2
11216 (@value{GDBP}) macro expand ADD(1)
11217 expands to: (42 + 1)
11218 (@value{GDBP}) macro expand-once ADD(1)
11219 expands to: once (M + 1)
11223 In the example above, note that @code{macro expand-once} expands only
11224 the macro invocation explicit in the original text --- the invocation of
11225 @code{ADD} --- but does not expand the invocation of the macro @code{M},
11226 which was introduced by @code{ADD}.
11228 Once the program is running, @value{GDBN} uses the macro definitions in
11229 force at the source line of the current stack frame:
11232 (@value{GDBP}) break main
11233 Breakpoint 1 at 0x8048370: file sample.c, line 10.
11235 Starting program: /home/jimb/gdb/macros/play/sample
11237 Breakpoint 1, main () at sample.c:10
11238 10 printf ("Hello, world!\n");
11242 At line 10, the definition of the macro @code{N} at line 9 is in force:
11245 (@value{GDBP}) info macro N
11246 Defined at /home/jimb/gdb/macros/play/sample.c:9
11248 (@value{GDBP}) macro expand N Q M
11249 expands to: 28 < 42
11250 (@value{GDBP}) print N Q M
11255 As we step over directives that remove @code{N}'s definition, and then
11256 give it a new definition, @value{GDBN} finds the definition (or lack
11257 thereof) in force at each point:
11260 (@value{GDBP}) next
11262 12 printf ("We're so creative.\n");
11263 (@value{GDBP}) info macro N
11264 The symbol `N' has no definition as a C/C++ preprocessor macro
11265 at /home/jimb/gdb/macros/play/sample.c:12
11266 (@value{GDBP}) next
11268 14 printf ("Goodbye, world!\n");
11269 (@value{GDBP}) info macro N
11270 Defined at /home/jimb/gdb/macros/play/sample.c:13
11272 (@value{GDBP}) macro expand N Q M
11273 expands to: 1729 < 42
11274 (@value{GDBP}) print N Q M
11279 In addition to source files, macros can be defined on the compilation command
11280 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11281 such a way, @value{GDBN} displays the location of their definition as line zero
11282 of the source file submitted to the compiler.
11285 (@value{GDBP}) info macro __STDC__
11286 Defined at /home/jimb/gdb/macros/play/sample.c:0
11293 @chapter Tracepoints
11294 @c This chapter is based on the documentation written by Michael
11295 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11297 @cindex tracepoints
11298 In some applications, it is not feasible for the debugger to interrupt
11299 the program's execution long enough for the developer to learn
11300 anything helpful about its behavior. If the program's correctness
11301 depends on its real-time behavior, delays introduced by a debugger
11302 might cause the program to change its behavior drastically, or perhaps
11303 fail, even when the code itself is correct. It is useful to be able
11304 to observe the program's behavior without interrupting it.
11306 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11307 specify locations in the program, called @dfn{tracepoints}, and
11308 arbitrary expressions to evaluate when those tracepoints are reached.
11309 Later, using the @code{tfind} command, you can examine the values
11310 those expressions had when the program hit the tracepoints. The
11311 expressions may also denote objects in memory---structures or arrays,
11312 for example---whose values @value{GDBN} should record; while visiting
11313 a particular tracepoint, you may inspect those objects as if they were
11314 in memory at that moment. However, because @value{GDBN} records these
11315 values without interacting with you, it can do so quickly and
11316 unobtrusively, hopefully not disturbing the program's behavior.
11318 The tracepoint facility is currently available only for remote
11319 targets. @xref{Targets}. In addition, your remote target must know
11320 how to collect trace data. This functionality is implemented in the
11321 remote stub; however, none of the stubs distributed with @value{GDBN}
11322 support tracepoints as of this writing. The format of the remote
11323 packets used to implement tracepoints are described in @ref{Tracepoint
11326 It is also possible to get trace data from a file, in a manner reminiscent
11327 of corefiles; you specify the filename, and use @code{tfind} to search
11328 through the file. @xref{Trace Files}, for more details.
11330 This chapter describes the tracepoint commands and features.
11333 * Set Tracepoints::
11334 * Analyze Collected Data::
11335 * Tracepoint Variables::
11339 @node Set Tracepoints
11340 @section Commands to Set Tracepoints
11342 Before running such a @dfn{trace experiment}, an arbitrary number of
11343 tracepoints can be set. A tracepoint is actually a special type of
11344 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11345 standard breakpoint commands. For instance, as with breakpoints,
11346 tracepoint numbers are successive integers starting from one, and many
11347 of the commands associated with tracepoints take the tracepoint number
11348 as their argument, to identify which tracepoint to work on.
11350 For each tracepoint, you can specify, in advance, some arbitrary set
11351 of data that you want the target to collect in the trace buffer when
11352 it hits that tracepoint. The collected data can include registers,
11353 local variables, or global data. Later, you can use @value{GDBN}
11354 commands to examine the values these data had at the time the
11355 tracepoint was hit.
11357 Tracepoints do not support every breakpoint feature. Ignore counts on
11358 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11359 commands when they are hit. Tracepoints may not be thread-specific
11362 @cindex fast tracepoints
11363 Some targets may support @dfn{fast tracepoints}, which are inserted in
11364 a different way (such as with a jump instead of a trap), that is
11365 faster but possibly restricted in where they may be installed.
11367 @cindex static tracepoints
11368 @cindex markers, static tracepoints
11369 @cindex probing markers, static tracepoints
11370 Regular and fast tracepoints are dynamic tracing facilities, meaning
11371 that they can be used to insert tracepoints at (almost) any location
11372 in the target. Some targets may also support controlling @dfn{static
11373 tracepoints} from @value{GDBN}. With static tracing, a set of
11374 instrumentation points, also known as @dfn{markers}, are embedded in
11375 the target program, and can be activated or deactivated by name or
11376 address. These are usually placed at locations which facilitate
11377 investigating what the target is actually doing. @value{GDBN}'s
11378 support for static tracing includes being able to list instrumentation
11379 points, and attach them with @value{GDBN} defined high level
11380 tracepoints that expose the whole range of convenience of
11381 @value{GDBN}'s tracepoints support. Namely, support for collecting
11382 registers values and values of global or local (to the instrumentation
11383 point) variables; tracepoint conditions and trace state variables.
11384 The act of installing a @value{GDBN} static tracepoint on an
11385 instrumentation point, or marker, is referred to as @dfn{probing} a
11386 static tracepoint marker.
11388 @code{gdbserver} supports tracepoints on some target systems.
11389 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11391 This section describes commands to set tracepoints and associated
11392 conditions and actions.
11395 * Create and Delete Tracepoints::
11396 * Enable and Disable Tracepoints::
11397 * Tracepoint Passcounts::
11398 * Tracepoint Conditions::
11399 * Trace State Variables::
11400 * Tracepoint Actions::
11401 * Listing Tracepoints::
11402 * Listing Static Tracepoint Markers::
11403 * Starting and Stopping Trace Experiments::
11404 * Tracepoint Restrictions::
11407 @node Create and Delete Tracepoints
11408 @subsection Create and Delete Tracepoints
11411 @cindex set tracepoint
11413 @item trace @var{location}
11414 The @code{trace} command is very similar to the @code{break} command.
11415 Its argument @var{location} can be a source line, a function name, or
11416 an address in the target program. @xref{Specify Location}. The
11417 @code{trace} command defines a tracepoint, which is a point in the
11418 target program where the debugger will briefly stop, collect some
11419 data, and then allow the program to continue. Setting a tracepoint or
11420 changing its actions takes effect immediately if the remote stub
11421 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11423 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11424 these changes don't take effect until the next @code{tstart}
11425 command, and once a trace experiment is running, further changes will
11426 not have any effect until the next trace experiment starts. In addition,
11427 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11428 address is not yet resolved. (This is similar to pending breakpoints.)
11429 Pending tracepoints are not downloaded to the target and not installed
11430 until they are resolved. The resolution of pending tracepoints requires
11431 @value{GDBN} support---when debugging with the remote target, and
11432 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11433 tracing}), pending tracepoints can not be resolved (and downloaded to
11434 the remote stub) while @value{GDBN} is disconnected.
11436 Here are some examples of using the @code{trace} command:
11439 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11441 (@value{GDBP}) @b{trace +2} // 2 lines forward
11443 (@value{GDBP}) @b{trace my_function} // first source line of function
11445 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11447 (@value{GDBP}) @b{trace *0x2117c4} // an address
11451 You can abbreviate @code{trace} as @code{tr}.
11453 @item trace @var{location} if @var{cond}
11454 Set a tracepoint with condition @var{cond}; evaluate the expression
11455 @var{cond} each time the tracepoint is reached, and collect data only
11456 if the value is nonzero---that is, if @var{cond} evaluates as true.
11457 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11458 information on tracepoint conditions.
11460 @item ftrace @var{location} [ if @var{cond} ]
11461 @cindex set fast tracepoint
11462 @cindex fast tracepoints, setting
11464 The @code{ftrace} command sets a fast tracepoint. For targets that
11465 support them, fast tracepoints will use a more efficient but possibly
11466 less general technique to trigger data collection, such as a jump
11467 instruction instead of a trap, or some sort of hardware support. It
11468 may not be possible to create a fast tracepoint at the desired
11469 location, in which case the command will exit with an explanatory
11472 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11475 On 32-bit x86-architecture systems, fast tracepoints normally need to
11476 be placed at an instruction that is 5 bytes or longer, but can be
11477 placed at 4-byte instructions if the low 64K of memory of the target
11478 program is available to install trampolines. Some Unix-type systems,
11479 such as @sc{gnu}/Linux, exclude low addresses from the program's
11480 address space; but for instance with the Linux kernel it is possible
11481 to let @value{GDBN} use this area by doing a @command{sysctl} command
11482 to set the @code{mmap_min_addr} kernel parameter, as in
11485 sudo sysctl -w vm.mmap_min_addr=32768
11489 which sets the low address to 32K, which leaves plenty of room for
11490 trampolines. The minimum address should be set to a page boundary.
11492 @item strace @var{location} [ if @var{cond} ]
11493 @cindex set static tracepoint
11494 @cindex static tracepoints, setting
11495 @cindex probe static tracepoint marker
11497 The @code{strace} command sets a static tracepoint. For targets that
11498 support it, setting a static tracepoint probes a static
11499 instrumentation point, or marker, found at @var{location}. It may not
11500 be possible to set a static tracepoint at the desired location, in
11501 which case the command will exit with an explanatory message.
11503 @value{GDBN} handles arguments to @code{strace} exactly as for
11504 @code{trace}, with the addition that the user can also specify
11505 @code{-m @var{marker}} as @var{location}. This probes the marker
11506 identified by the @var{marker} string identifier. This identifier
11507 depends on the static tracepoint backend library your program is
11508 using. You can find all the marker identifiers in the @samp{ID} field
11509 of the @code{info static-tracepoint-markers} command output.
11510 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11511 Markers}. For example, in the following small program using the UST
11517 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11522 the marker id is composed of joining the first two arguments to the
11523 @code{trace_mark} call with a slash, which translates to:
11526 (@value{GDBP}) info static-tracepoint-markers
11527 Cnt Enb ID Address What
11528 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11534 so you may probe the marker above with:
11537 (@value{GDBP}) strace -m ust/bar33
11540 Static tracepoints accept an extra collect action --- @code{collect
11541 $_sdata}. This collects arbitrary user data passed in the probe point
11542 call to the tracing library. In the UST example above, you'll see
11543 that the third argument to @code{trace_mark} is a printf-like format
11544 string. The user data is then the result of running that formating
11545 string against the following arguments. Note that @code{info
11546 static-tracepoint-markers} command output lists that format string in
11547 the @samp{Data:} field.
11549 You can inspect this data when analyzing the trace buffer, by printing
11550 the $_sdata variable like any other variable available to
11551 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11554 @cindex last tracepoint number
11555 @cindex recent tracepoint number
11556 @cindex tracepoint number
11557 The convenience variable @code{$tpnum} records the tracepoint number
11558 of the most recently set tracepoint.
11560 @kindex delete tracepoint
11561 @cindex tracepoint deletion
11562 @item delete tracepoint @r{[}@var{num}@r{]}
11563 Permanently delete one or more tracepoints. With no argument, the
11564 default is to delete all tracepoints. Note that the regular
11565 @code{delete} command can remove tracepoints also.
11570 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11572 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11576 You can abbreviate this command as @code{del tr}.
11579 @node Enable and Disable Tracepoints
11580 @subsection Enable and Disable Tracepoints
11582 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11585 @kindex disable tracepoint
11586 @item disable tracepoint @r{[}@var{num}@r{]}
11587 Disable tracepoint @var{num}, or all tracepoints if no argument
11588 @var{num} is given. A disabled tracepoint will have no effect during
11589 a trace experiment, but it is not forgotten. You can re-enable
11590 a disabled tracepoint using the @code{enable tracepoint} command.
11591 If the command is issued during a trace experiment and the debug target
11592 has support for disabling tracepoints during a trace experiment, then the
11593 change will be effective immediately. Otherwise, it will be applied to the
11594 next trace experiment.
11596 @kindex enable tracepoint
11597 @item enable tracepoint @r{[}@var{num}@r{]}
11598 Enable tracepoint @var{num}, or all tracepoints. If this command is
11599 issued during a trace experiment and the debug target supports enabling
11600 tracepoints during a trace experiment, then the enabled tracepoints will
11601 become effective immediately. Otherwise, they will become effective the
11602 next time a trace experiment is run.
11605 @node Tracepoint Passcounts
11606 @subsection Tracepoint Passcounts
11610 @cindex tracepoint pass count
11611 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11612 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11613 automatically stop a trace experiment. If a tracepoint's passcount is
11614 @var{n}, then the trace experiment will be automatically stopped on
11615 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11616 @var{num} is not specified, the @code{passcount} command sets the
11617 passcount of the most recently defined tracepoint. If no passcount is
11618 given, the trace experiment will run until stopped explicitly by the
11624 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11625 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11627 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11628 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11629 (@value{GDBP}) @b{trace foo}
11630 (@value{GDBP}) @b{pass 3}
11631 (@value{GDBP}) @b{trace bar}
11632 (@value{GDBP}) @b{pass 2}
11633 (@value{GDBP}) @b{trace baz}
11634 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11635 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11636 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11637 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11641 @node Tracepoint Conditions
11642 @subsection Tracepoint Conditions
11643 @cindex conditional tracepoints
11644 @cindex tracepoint conditions
11646 The simplest sort of tracepoint collects data every time your program
11647 reaches a specified place. You can also specify a @dfn{condition} for
11648 a tracepoint. A condition is just a Boolean expression in your
11649 programming language (@pxref{Expressions, ,Expressions}). A
11650 tracepoint with a condition evaluates the expression each time your
11651 program reaches it, and data collection happens only if the condition
11654 Tracepoint conditions can be specified when a tracepoint is set, by
11655 using @samp{if} in the arguments to the @code{trace} command.
11656 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11657 also be set or changed at any time with the @code{condition} command,
11658 just as with breakpoints.
11660 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11661 the conditional expression itself. Instead, @value{GDBN} encodes the
11662 expression into an agent expression (@pxref{Agent Expressions})
11663 suitable for execution on the target, independently of @value{GDBN}.
11664 Global variables become raw memory locations, locals become stack
11665 accesses, and so forth.
11667 For instance, suppose you have a function that is usually called
11668 frequently, but should not be called after an error has occurred. You
11669 could use the following tracepoint command to collect data about calls
11670 of that function that happen while the error code is propagating
11671 through the program; an unconditional tracepoint could end up
11672 collecting thousands of useless trace frames that you would have to
11676 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11679 @node Trace State Variables
11680 @subsection Trace State Variables
11681 @cindex trace state variables
11683 A @dfn{trace state variable} is a special type of variable that is
11684 created and managed by target-side code. The syntax is the same as
11685 that for GDB's convenience variables (a string prefixed with ``$''),
11686 but they are stored on the target. They must be created explicitly,
11687 using a @code{tvariable} command. They are always 64-bit signed
11690 Trace state variables are remembered by @value{GDBN}, and downloaded
11691 to the target along with tracepoint information when the trace
11692 experiment starts. There are no intrinsic limits on the number of
11693 trace state variables, beyond memory limitations of the target.
11695 @cindex convenience variables, and trace state variables
11696 Although trace state variables are managed by the target, you can use
11697 them in print commands and expressions as if they were convenience
11698 variables; @value{GDBN} will get the current value from the target
11699 while the trace experiment is running. Trace state variables share
11700 the same namespace as other ``$'' variables, which means that you
11701 cannot have trace state variables with names like @code{$23} or
11702 @code{$pc}, nor can you have a trace state variable and a convenience
11703 variable with the same name.
11707 @item tvariable $@var{name} [ = @var{expression} ]
11709 The @code{tvariable} command creates a new trace state variable named
11710 @code{$@var{name}}, and optionally gives it an initial value of
11711 @var{expression}. @var{expression} is evaluated when this command is
11712 entered; the result will be converted to an integer if possible,
11713 otherwise @value{GDBN} will report an error. A subsequent
11714 @code{tvariable} command specifying the same name does not create a
11715 variable, but instead assigns the supplied initial value to the
11716 existing variable of that name, overwriting any previous initial
11717 value. The default initial value is 0.
11719 @item info tvariables
11720 @kindex info tvariables
11721 List all the trace state variables along with their initial values.
11722 Their current values may also be displayed, if the trace experiment is
11725 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11726 @kindex delete tvariable
11727 Delete the given trace state variables, or all of them if no arguments
11732 @node Tracepoint Actions
11733 @subsection Tracepoint Action Lists
11737 @cindex tracepoint actions
11738 @item actions @r{[}@var{num}@r{]}
11739 This command will prompt for a list of actions to be taken when the
11740 tracepoint is hit. If the tracepoint number @var{num} is not
11741 specified, this command sets the actions for the one that was most
11742 recently defined (so that you can define a tracepoint and then say
11743 @code{actions} without bothering about its number). You specify the
11744 actions themselves on the following lines, one action at a time, and
11745 terminate the actions list with a line containing just @code{end}. So
11746 far, the only defined actions are @code{collect}, @code{teval}, and
11747 @code{while-stepping}.
11749 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11750 Commands, ,Breakpoint Command Lists}), except that only the defined
11751 actions are allowed; any other @value{GDBN} command is rejected.
11753 @cindex remove actions from a tracepoint
11754 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11755 and follow it immediately with @samp{end}.
11758 (@value{GDBP}) @b{collect @var{data}} // collect some data
11760 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11762 (@value{GDBP}) @b{end} // signals the end of actions.
11765 In the following example, the action list begins with @code{collect}
11766 commands indicating the things to be collected when the tracepoint is
11767 hit. Then, in order to single-step and collect additional data
11768 following the tracepoint, a @code{while-stepping} command is used,
11769 followed by the list of things to be collected after each step in a
11770 sequence of single steps. The @code{while-stepping} command is
11771 terminated by its own separate @code{end} command. Lastly, the action
11772 list is terminated by an @code{end} command.
11775 (@value{GDBP}) @b{trace foo}
11776 (@value{GDBP}) @b{actions}
11777 Enter actions for tracepoint 1, one per line:
11780 > while-stepping 12
11781 > collect $pc, arr[i]
11786 @kindex collect @r{(tracepoints)}
11787 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11788 Collect values of the given expressions when the tracepoint is hit.
11789 This command accepts a comma-separated list of any valid expressions.
11790 In addition to global, static, or local variables, the following
11791 special arguments are supported:
11795 Collect all registers.
11798 Collect all function arguments.
11801 Collect all local variables.
11804 Collect the return address. This is helpful if you want to see more
11808 Collects the number of arguments from the static probe at which the
11809 tracepoint is located.
11810 @xref{Static Probe Points}.
11812 @item $_probe_arg@var{n}
11813 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11814 from the static probe at which the tracepoint is located.
11815 @xref{Static Probe Points}.
11818 @vindex $_sdata@r{, collect}
11819 Collect static tracepoint marker specific data. Only available for
11820 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11821 Lists}. On the UST static tracepoints library backend, an
11822 instrumentation point resembles a @code{printf} function call. The
11823 tracing library is able to collect user specified data formatted to a
11824 character string using the format provided by the programmer that
11825 instrumented the program. Other backends have similar mechanisms.
11826 Here's an example of a UST marker call:
11829 const char master_name[] = "$your_name";
11830 trace_mark(channel1, marker1, "hello %s", master_name)
11833 In this case, collecting @code{$_sdata} collects the string
11834 @samp{hello $yourname}. When analyzing the trace buffer, you can
11835 inspect @samp{$_sdata} like any other variable available to
11839 You can give several consecutive @code{collect} commands, each one
11840 with a single argument, or one @code{collect} command with several
11841 arguments separated by commas; the effect is the same.
11843 The optional @var{mods} changes the usual handling of the arguments.
11844 @code{s} requests that pointers to chars be handled as strings, in
11845 particular collecting the contents of the memory being pointed at, up
11846 to the first zero. The upper bound is by default the value of the
11847 @code{print elements} variable; if @code{s} is followed by a decimal
11848 number, that is the upper bound instead. So for instance
11849 @samp{collect/s25 mystr} collects as many as 25 characters at
11852 The command @code{info scope} (@pxref{Symbols, info scope}) is
11853 particularly useful for figuring out what data to collect.
11855 @kindex teval @r{(tracepoints)}
11856 @item teval @var{expr1}, @var{expr2}, @dots{}
11857 Evaluate the given expressions when the tracepoint is hit. This
11858 command accepts a comma-separated list of expressions. The results
11859 are discarded, so this is mainly useful for assigning values to trace
11860 state variables (@pxref{Trace State Variables}) without adding those
11861 values to the trace buffer, as would be the case if the @code{collect}
11864 @kindex while-stepping @r{(tracepoints)}
11865 @item while-stepping @var{n}
11866 Perform @var{n} single-step instruction traces after the tracepoint,
11867 collecting new data after each step. The @code{while-stepping}
11868 command is followed by the list of what to collect while stepping
11869 (followed by its own @code{end} command):
11872 > while-stepping 12
11873 > collect $regs, myglobal
11879 Note that @code{$pc} is not automatically collected by
11880 @code{while-stepping}; you need to explicitly collect that register if
11881 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11884 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11885 @kindex set default-collect
11886 @cindex default collection action
11887 This variable is a list of expressions to collect at each tracepoint
11888 hit. It is effectively an additional @code{collect} action prepended
11889 to every tracepoint action list. The expressions are parsed
11890 individually for each tracepoint, so for instance a variable named
11891 @code{xyz} may be interpreted as a global for one tracepoint, and a
11892 local for another, as appropriate to the tracepoint's location.
11894 @item show default-collect
11895 @kindex show default-collect
11896 Show the list of expressions that are collected by default at each
11901 @node Listing Tracepoints
11902 @subsection Listing Tracepoints
11905 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11906 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11907 @cindex information about tracepoints
11908 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11909 Display information about the tracepoint @var{num}. If you don't
11910 specify a tracepoint number, displays information about all the
11911 tracepoints defined so far. The format is similar to that used for
11912 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11913 command, simply restricting itself to tracepoints.
11915 A tracepoint's listing may include additional information specific to
11920 its passcount as given by the @code{passcount @var{n}} command
11923 the state about installed on target of each location
11927 (@value{GDBP}) @b{info trace}
11928 Num Type Disp Enb Address What
11929 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11931 collect globfoo, $regs
11936 2 tracepoint keep y <MULTIPLE>
11938 2.1 y 0x0804859c in func4 at change-loc.h:35
11939 installed on target
11940 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11941 installed on target
11942 2.3 y <PENDING> set_tracepoint
11943 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11944 not installed on target
11949 This command can be abbreviated @code{info tp}.
11952 @node Listing Static Tracepoint Markers
11953 @subsection Listing Static Tracepoint Markers
11956 @kindex info static-tracepoint-markers
11957 @cindex information about static tracepoint markers
11958 @item info static-tracepoint-markers
11959 Display information about all static tracepoint markers defined in the
11962 For each marker, the following columns are printed:
11966 An incrementing counter, output to help readability. This is not a
11969 The marker ID, as reported by the target.
11970 @item Enabled or Disabled
11971 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11972 that are not enabled.
11974 Where the marker is in your program, as a memory address.
11976 Where the marker is in the source for your program, as a file and line
11977 number. If the debug information included in the program does not
11978 allow @value{GDBN} to locate the source of the marker, this column
11979 will be left blank.
11983 In addition, the following information may be printed for each marker:
11987 User data passed to the tracing library by the marker call. In the
11988 UST backend, this is the format string passed as argument to the
11990 @item Static tracepoints probing the marker
11991 The list of static tracepoints attached to the marker.
11995 (@value{GDBP}) info static-tracepoint-markers
11996 Cnt ID Enb Address What
11997 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11998 Data: number1 %d number2 %d
11999 Probed by static tracepoints: #2
12000 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
12006 @node Starting and Stopping Trace Experiments
12007 @subsection Starting and Stopping Trace Experiments
12010 @kindex tstart [ @var{notes} ]
12011 @cindex start a new trace experiment
12012 @cindex collected data discarded
12014 This command starts the trace experiment, and begins collecting data.
12015 It has the side effect of discarding all the data collected in the
12016 trace buffer during the previous trace experiment. If any arguments
12017 are supplied, they are taken as a note and stored with the trace
12018 experiment's state. The notes may be arbitrary text, and are
12019 especially useful with disconnected tracing in a multi-user context;
12020 the notes can explain what the trace is doing, supply user contact
12021 information, and so forth.
12023 @kindex tstop [ @var{notes} ]
12024 @cindex stop a running trace experiment
12026 This command stops the trace experiment. If any arguments are
12027 supplied, they are recorded with the experiment as a note. This is
12028 useful if you are stopping a trace started by someone else, for
12029 instance if the trace is interfering with the system's behavior and
12030 needs to be stopped quickly.
12032 @strong{Note}: a trace experiment and data collection may stop
12033 automatically if any tracepoint's passcount is reached
12034 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
12037 @cindex status of trace data collection
12038 @cindex trace experiment, status of
12040 This command displays the status of the current trace data
12044 Here is an example of the commands we described so far:
12047 (@value{GDBP}) @b{trace gdb_c_test}
12048 (@value{GDBP}) @b{actions}
12049 Enter actions for tracepoint #1, one per line.
12050 > collect $regs,$locals,$args
12051 > while-stepping 11
12055 (@value{GDBP}) @b{tstart}
12056 [time passes @dots{}]
12057 (@value{GDBP}) @b{tstop}
12060 @anchor{disconnected tracing}
12061 @cindex disconnected tracing
12062 You can choose to continue running the trace experiment even if
12063 @value{GDBN} disconnects from the target, voluntarily or
12064 involuntarily. For commands such as @code{detach}, the debugger will
12065 ask what you want to do with the trace. But for unexpected
12066 terminations (@value{GDBN} crash, network outage), it would be
12067 unfortunate to lose hard-won trace data, so the variable
12068 @code{disconnected-tracing} lets you decide whether the trace should
12069 continue running without @value{GDBN}.
12072 @item set disconnected-tracing on
12073 @itemx set disconnected-tracing off
12074 @kindex set disconnected-tracing
12075 Choose whether a tracing run should continue to run if @value{GDBN}
12076 has disconnected from the target. Note that @code{detach} or
12077 @code{quit} will ask you directly what to do about a running trace no
12078 matter what this variable's setting, so the variable is mainly useful
12079 for handling unexpected situations, such as loss of the network.
12081 @item show disconnected-tracing
12082 @kindex show disconnected-tracing
12083 Show the current choice for disconnected tracing.
12087 When you reconnect to the target, the trace experiment may or may not
12088 still be running; it might have filled the trace buffer in the
12089 meantime, or stopped for one of the other reasons. If it is running,
12090 it will continue after reconnection.
12092 Upon reconnection, the target will upload information about the
12093 tracepoints in effect. @value{GDBN} will then compare that
12094 information to the set of tracepoints currently defined, and attempt
12095 to match them up, allowing for the possibility that the numbers may
12096 have changed due to creation and deletion in the meantime. If one of
12097 the target's tracepoints does not match any in @value{GDBN}, the
12098 debugger will create a new tracepoint, so that you have a number with
12099 which to specify that tracepoint. This matching-up process is
12100 necessarily heuristic, and it may result in useless tracepoints being
12101 created; you may simply delete them if they are of no use.
12103 @cindex circular trace buffer
12104 If your target agent supports a @dfn{circular trace buffer}, then you
12105 can run a trace experiment indefinitely without filling the trace
12106 buffer; when space runs out, the agent deletes already-collected trace
12107 frames, oldest first, until there is enough room to continue
12108 collecting. This is especially useful if your tracepoints are being
12109 hit too often, and your trace gets terminated prematurely because the
12110 buffer is full. To ask for a circular trace buffer, simply set
12111 @samp{circular-trace-buffer} to on. You can set this at any time,
12112 including during tracing; if the agent can do it, it will change
12113 buffer handling on the fly, otherwise it will not take effect until
12117 @item set circular-trace-buffer on
12118 @itemx set circular-trace-buffer off
12119 @kindex set circular-trace-buffer
12120 Choose whether a tracing run should use a linear or circular buffer
12121 for trace data. A linear buffer will not lose any trace data, but may
12122 fill up prematurely, while a circular buffer will discard old trace
12123 data, but it will have always room for the latest tracepoint hits.
12125 @item show circular-trace-buffer
12126 @kindex show circular-trace-buffer
12127 Show the current choice for the trace buffer. Note that this may not
12128 match the agent's current buffer handling, nor is it guaranteed to
12129 match the setting that might have been in effect during a past run,
12130 for instance if you are looking at frames from a trace file.
12135 @item set trace-buffer-size @var{n}
12136 @itemx set trace-buffer-size unlimited
12137 @kindex set trace-buffer-size
12138 Request that the target use a trace buffer of @var{n} bytes. Not all
12139 targets will honor the request; they may have a compiled-in size for
12140 the trace buffer, or some other limitation. Set to a value of
12141 @code{unlimited} or @code{-1} to let the target use whatever size it
12142 likes. This is also the default.
12144 @item show trace-buffer-size
12145 @kindex show trace-buffer-size
12146 Show the current requested size for the trace buffer. Note that this
12147 will only match the actual size if the target supports size-setting,
12148 and was able to handle the requested size. For instance, if the
12149 target can only change buffer size between runs, this variable will
12150 not reflect the change until the next run starts. Use @code{tstatus}
12151 to get a report of the actual buffer size.
12155 @item set trace-user @var{text}
12156 @kindex set trace-user
12158 @item show trace-user
12159 @kindex show trace-user
12161 @item set trace-notes @var{text}
12162 @kindex set trace-notes
12163 Set the trace run's notes.
12165 @item show trace-notes
12166 @kindex show trace-notes
12167 Show the trace run's notes.
12169 @item set trace-stop-notes @var{text}
12170 @kindex set trace-stop-notes
12171 Set the trace run's stop notes. The handling of the note is as for
12172 @code{tstop} arguments; the set command is convenient way to fix a
12173 stop note that is mistaken or incomplete.
12175 @item show trace-stop-notes
12176 @kindex show trace-stop-notes
12177 Show the trace run's stop notes.
12181 @node Tracepoint Restrictions
12182 @subsection Tracepoint Restrictions
12184 @cindex tracepoint restrictions
12185 There are a number of restrictions on the use of tracepoints. As
12186 described above, tracepoint data gathering occurs on the target
12187 without interaction from @value{GDBN}. Thus the full capabilities of
12188 the debugger are not available during data gathering, and then at data
12189 examination time, you will be limited by only having what was
12190 collected. The following items describe some common problems, but it
12191 is not exhaustive, and you may run into additional difficulties not
12197 Tracepoint expressions are intended to gather objects (lvalues). Thus
12198 the full flexibility of GDB's expression evaluator is not available.
12199 You cannot call functions, cast objects to aggregate types, access
12200 convenience variables or modify values (except by assignment to trace
12201 state variables). Some language features may implicitly call
12202 functions (for instance Objective-C fields with accessors), and therefore
12203 cannot be collected either.
12206 Collection of local variables, either individually or in bulk with
12207 @code{$locals} or @code{$args}, during @code{while-stepping} may
12208 behave erratically. The stepping action may enter a new scope (for
12209 instance by stepping into a function), or the location of the variable
12210 may change (for instance it is loaded into a register). The
12211 tracepoint data recorded uses the location information for the
12212 variables that is correct for the tracepoint location. When the
12213 tracepoint is created, it is not possible, in general, to determine
12214 where the steps of a @code{while-stepping} sequence will advance the
12215 program---particularly if a conditional branch is stepped.
12218 Collection of an incompletely-initialized or partially-destroyed object
12219 may result in something that @value{GDBN} cannot display, or displays
12220 in a misleading way.
12223 When @value{GDBN} displays a pointer to character it automatically
12224 dereferences the pointer to also display characters of the string
12225 being pointed to. However, collecting the pointer during tracing does
12226 not automatically collect the string. You need to explicitly
12227 dereference the pointer and provide size information if you want to
12228 collect not only the pointer, but the memory pointed to. For example,
12229 @code{*ptr@@50} can be used to collect the 50 element array pointed to
12233 It is not possible to collect a complete stack backtrace at a
12234 tracepoint. Instead, you may collect the registers and a few hundred
12235 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
12236 (adjust to use the name of the actual stack pointer register on your
12237 target architecture, and the amount of stack you wish to capture).
12238 Then the @code{backtrace} command will show a partial backtrace when
12239 using a trace frame. The number of stack frames that can be examined
12240 depends on the sizes of the frames in the collected stack. Note that
12241 if you ask for a block so large that it goes past the bottom of the
12242 stack, the target agent may report an error trying to read from an
12246 If you do not collect registers at a tracepoint, @value{GDBN} can
12247 infer that the value of @code{$pc} must be the same as the address of
12248 the tracepoint and use that when you are looking at a trace frame
12249 for that tracepoint. However, this cannot work if the tracepoint has
12250 multiple locations (for instance if it was set in a function that was
12251 inlined), or if it has a @code{while-stepping} loop. In those cases
12252 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
12257 @node Analyze Collected Data
12258 @section Using the Collected Data
12260 After the tracepoint experiment ends, you use @value{GDBN} commands
12261 for examining the trace data. The basic idea is that each tracepoint
12262 collects a trace @dfn{snapshot} every time it is hit and another
12263 snapshot every time it single-steps. All these snapshots are
12264 consecutively numbered from zero and go into a buffer, and you can
12265 examine them later. The way you examine them is to @dfn{focus} on a
12266 specific trace snapshot. When the remote stub is focused on a trace
12267 snapshot, it will respond to all @value{GDBN} requests for memory and
12268 registers by reading from the buffer which belongs to that snapshot,
12269 rather than from @emph{real} memory or registers of the program being
12270 debugged. This means that @strong{all} @value{GDBN} commands
12271 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12272 behave as if we were currently debugging the program state as it was
12273 when the tracepoint occurred. Any requests for data that are not in
12274 the buffer will fail.
12277 * tfind:: How to select a trace snapshot
12278 * tdump:: How to display all data for a snapshot
12279 * save tracepoints:: How to save tracepoints for a future run
12283 @subsection @code{tfind @var{n}}
12286 @cindex select trace snapshot
12287 @cindex find trace snapshot
12288 The basic command for selecting a trace snapshot from the buffer is
12289 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12290 counting from zero. If no argument @var{n} is given, the next
12291 snapshot is selected.
12293 Here are the various forms of using the @code{tfind} command.
12297 Find the first snapshot in the buffer. This is a synonym for
12298 @code{tfind 0} (since 0 is the number of the first snapshot).
12301 Stop debugging trace snapshots, resume @emph{live} debugging.
12304 Same as @samp{tfind none}.
12307 No argument means find the next trace snapshot.
12310 Find the previous trace snapshot before the current one. This permits
12311 retracing earlier steps.
12313 @item tfind tracepoint @var{num}
12314 Find the next snapshot associated with tracepoint @var{num}. Search
12315 proceeds forward from the last examined trace snapshot. If no
12316 argument @var{num} is given, it means find the next snapshot collected
12317 for the same tracepoint as the current snapshot.
12319 @item tfind pc @var{addr}
12320 Find the next snapshot associated with the value @var{addr} of the
12321 program counter. Search proceeds forward from the last examined trace
12322 snapshot. If no argument @var{addr} is given, it means find the next
12323 snapshot with the same value of PC as the current snapshot.
12325 @item tfind outside @var{addr1}, @var{addr2}
12326 Find the next snapshot whose PC is outside the given range of
12327 addresses (exclusive).
12329 @item tfind range @var{addr1}, @var{addr2}
12330 Find the next snapshot whose PC is between @var{addr1} and
12331 @var{addr2} (inclusive).
12333 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12334 Find the next snapshot associated with the source line @var{n}. If
12335 the optional argument @var{file} is given, refer to line @var{n} in
12336 that source file. Search proceeds forward from the last examined
12337 trace snapshot. If no argument @var{n} is given, it means find the
12338 next line other than the one currently being examined; thus saying
12339 @code{tfind line} repeatedly can appear to have the same effect as
12340 stepping from line to line in a @emph{live} debugging session.
12343 The default arguments for the @code{tfind} commands are specifically
12344 designed to make it easy to scan through the trace buffer. For
12345 instance, @code{tfind} with no argument selects the next trace
12346 snapshot, and @code{tfind -} with no argument selects the previous
12347 trace snapshot. So, by giving one @code{tfind} command, and then
12348 simply hitting @key{RET} repeatedly you can examine all the trace
12349 snapshots in order. Or, by saying @code{tfind -} and then hitting
12350 @key{RET} repeatedly you can examine the snapshots in reverse order.
12351 The @code{tfind line} command with no argument selects the snapshot
12352 for the next source line executed. The @code{tfind pc} command with
12353 no argument selects the next snapshot with the same program counter
12354 (PC) as the current frame. The @code{tfind tracepoint} command with
12355 no argument selects the next trace snapshot collected by the same
12356 tracepoint as the current one.
12358 In addition to letting you scan through the trace buffer manually,
12359 these commands make it easy to construct @value{GDBN} scripts that
12360 scan through the trace buffer and print out whatever collected data
12361 you are interested in. Thus, if we want to examine the PC, FP, and SP
12362 registers from each trace frame in the buffer, we can say this:
12365 (@value{GDBP}) @b{tfind start}
12366 (@value{GDBP}) @b{while ($trace_frame != -1)}
12367 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12368 $trace_frame, $pc, $sp, $fp
12372 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12373 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12374 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12375 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12376 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12377 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12378 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12379 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12380 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12381 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12382 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12385 Or, if we want to examine the variable @code{X} at each source line in
12389 (@value{GDBP}) @b{tfind start}
12390 (@value{GDBP}) @b{while ($trace_frame != -1)}
12391 > printf "Frame %d, X == %d\n", $trace_frame, X
12401 @subsection @code{tdump}
12403 @cindex dump all data collected at tracepoint
12404 @cindex tracepoint data, display
12406 This command takes no arguments. It prints all the data collected at
12407 the current trace snapshot.
12410 (@value{GDBP}) @b{trace 444}
12411 (@value{GDBP}) @b{actions}
12412 Enter actions for tracepoint #2, one per line:
12413 > collect $regs, $locals, $args, gdb_long_test
12416 (@value{GDBP}) @b{tstart}
12418 (@value{GDBP}) @b{tfind line 444}
12419 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12421 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12423 (@value{GDBP}) @b{tdump}
12424 Data collected at tracepoint 2, trace frame 1:
12425 d0 0xc4aa0085 -995491707
12429 d4 0x71aea3d 119204413
12432 d7 0x380035 3670069
12433 a0 0x19e24a 1696330
12434 a1 0x3000668 50333288
12436 a3 0x322000 3284992
12437 a4 0x3000698 50333336
12438 a5 0x1ad3cc 1758156
12439 fp 0x30bf3c 0x30bf3c
12440 sp 0x30bf34 0x30bf34
12442 pc 0x20b2c8 0x20b2c8
12446 p = 0x20e5b4 "gdb-test"
12453 gdb_long_test = 17 '\021'
12458 @code{tdump} works by scanning the tracepoint's current collection
12459 actions and printing the value of each expression listed. So
12460 @code{tdump} can fail, if after a run, you change the tracepoint's
12461 actions to mention variables that were not collected during the run.
12463 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12464 uses the collected value of @code{$pc} to distinguish between trace
12465 frames that were collected at the tracepoint hit, and frames that were
12466 collected while stepping. This allows it to correctly choose whether
12467 to display the basic list of collections, or the collections from the
12468 body of the while-stepping loop. However, if @code{$pc} was not collected,
12469 then @code{tdump} will always attempt to dump using the basic collection
12470 list, and may fail if a while-stepping frame does not include all the
12471 same data that is collected at the tracepoint hit.
12472 @c This is getting pretty arcane, example would be good.
12474 @node save tracepoints
12475 @subsection @code{save tracepoints @var{filename}}
12476 @kindex save tracepoints
12477 @kindex save-tracepoints
12478 @cindex save tracepoints for future sessions
12480 This command saves all current tracepoint definitions together with
12481 their actions and passcounts, into a file @file{@var{filename}}
12482 suitable for use in a later debugging session. To read the saved
12483 tracepoint definitions, use the @code{source} command (@pxref{Command
12484 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12485 alias for @w{@code{save tracepoints}}
12487 @node Tracepoint Variables
12488 @section Convenience Variables for Tracepoints
12489 @cindex tracepoint variables
12490 @cindex convenience variables for tracepoints
12493 @vindex $trace_frame
12494 @item (int) $trace_frame
12495 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12496 snapshot is selected.
12498 @vindex $tracepoint
12499 @item (int) $tracepoint
12500 The tracepoint for the current trace snapshot.
12502 @vindex $trace_line
12503 @item (int) $trace_line
12504 The line number for the current trace snapshot.
12506 @vindex $trace_file
12507 @item (char []) $trace_file
12508 The source file for the current trace snapshot.
12510 @vindex $trace_func
12511 @item (char []) $trace_func
12512 The name of the function containing @code{$tracepoint}.
12515 Note: @code{$trace_file} is not suitable for use in @code{printf},
12516 use @code{output} instead.
12518 Here's a simple example of using these convenience variables for
12519 stepping through all the trace snapshots and printing some of their
12520 data. Note that these are not the same as trace state variables,
12521 which are managed by the target.
12524 (@value{GDBP}) @b{tfind start}
12526 (@value{GDBP}) @b{while $trace_frame != -1}
12527 > output $trace_file
12528 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12534 @section Using Trace Files
12535 @cindex trace files
12537 In some situations, the target running a trace experiment may no
12538 longer be available; perhaps it crashed, or the hardware was needed
12539 for a different activity. To handle these cases, you can arrange to
12540 dump the trace data into a file, and later use that file as a source
12541 of trace data, via the @code{target tfile} command.
12546 @item tsave [ -r ] @var{filename}
12547 @itemx tsave [-ctf] @var{dirname}
12548 Save the trace data to @var{filename}. By default, this command
12549 assumes that @var{filename} refers to the host filesystem, so if
12550 necessary @value{GDBN} will copy raw trace data up from the target and
12551 then save it. If the target supports it, you can also supply the
12552 optional argument @code{-r} (``remote'') to direct the target to save
12553 the data directly into @var{filename} in its own filesystem, which may be
12554 more efficient if the trace buffer is very large. (Note, however, that
12555 @code{target tfile} can only read from files accessible to the host.)
12556 By default, this command will save trace frame in tfile format.
12557 You can supply the optional argument @code{-ctf} to save date in CTF
12558 format. The @dfn{Common Trace Format} (CTF) is proposed as a trace format
12559 that can be shared by multiple debugging and tracing tools. Please go to
12560 @indicateurl{http://www.efficios.com/ctf} to get more information.
12562 @kindex target tfile
12566 @item target tfile @var{filename}
12567 @itemx target ctf @var{dirname}
12568 Use the file named @var{filename} or directory named @var{dirname} as
12569 a source of trace data. Commands that examine data work as they do with
12570 a live target, but it is not possible to run any new trace experiments.
12571 @code{tstatus} will report the state of the trace run at the moment
12572 the data was saved, as well as the current trace frame you are examining.
12573 @var{filename} or @var{dirname} must be on a filesystem accessible to
12577 (@value{GDBP}) target ctf ctf.ctf
12578 (@value{GDBP}) tfind
12579 Found trace frame 0, tracepoint 2
12580 39 ++a; /* set tracepoint 1 here */
12581 (@value{GDBP}) tdump
12582 Data collected at tracepoint 2, trace frame 0:
12586 c = @{"123", "456", "789", "123", "456", "789"@}
12587 d = @{@{@{a = 1, b = 2@}, @{a = 3, b = 4@}@}, @{@{a = 5, b = 6@}, @{a = 7, b = 8@}@}@}
12595 @chapter Debugging Programs That Use Overlays
12598 If your program is too large to fit completely in your target system's
12599 memory, you can sometimes use @dfn{overlays} to work around this
12600 problem. @value{GDBN} provides some support for debugging programs that
12604 * How Overlays Work:: A general explanation of overlays.
12605 * Overlay Commands:: Managing overlays in @value{GDBN}.
12606 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12607 mapped by asking the inferior.
12608 * Overlay Sample Program:: A sample program using overlays.
12611 @node How Overlays Work
12612 @section How Overlays Work
12613 @cindex mapped overlays
12614 @cindex unmapped overlays
12615 @cindex load address, overlay's
12616 @cindex mapped address
12617 @cindex overlay area
12619 Suppose you have a computer whose instruction address space is only 64
12620 kilobytes long, but which has much more memory which can be accessed by
12621 other means: special instructions, segment registers, or memory
12622 management hardware, for example. Suppose further that you want to
12623 adapt a program which is larger than 64 kilobytes to run on this system.
12625 One solution is to identify modules of your program which are relatively
12626 independent, and need not call each other directly; call these modules
12627 @dfn{overlays}. Separate the overlays from the main program, and place
12628 their machine code in the larger memory. Place your main program in
12629 instruction memory, but leave at least enough space there to hold the
12630 largest overlay as well.
12632 Now, to call a function located in an overlay, you must first copy that
12633 overlay's machine code from the large memory into the space set aside
12634 for it in the instruction memory, and then jump to its entry point
12637 @c NB: In the below the mapped area's size is greater or equal to the
12638 @c size of all overlays. This is intentional to remind the developer
12639 @c that overlays don't necessarily need to be the same size.
12643 Data Instruction Larger
12644 Address Space Address Space Address Space
12645 +-----------+ +-----------+ +-----------+
12647 +-----------+ +-----------+ +-----------+<-- overlay 1
12648 | program | | main | .----| overlay 1 | load address
12649 | variables | | program | | +-----------+
12650 | and heap | | | | | |
12651 +-----------+ | | | +-----------+<-- overlay 2
12652 | | +-----------+ | | | load address
12653 +-----------+ | | | .-| overlay 2 |
12655 mapped --->+-----------+ | | +-----------+
12656 address | | | | | |
12657 | overlay | <-' | | |
12658 | area | <---' +-----------+<-- overlay 3
12659 | | <---. | | load address
12660 +-----------+ `--| overlay 3 |
12667 @anchor{A code overlay}A code overlay
12671 The diagram (@pxref{A code overlay}) shows a system with separate data
12672 and instruction address spaces. To map an overlay, the program copies
12673 its code from the larger address space to the instruction address space.
12674 Since the overlays shown here all use the same mapped address, only one
12675 may be mapped at a time. For a system with a single address space for
12676 data and instructions, the diagram would be similar, except that the
12677 program variables and heap would share an address space with the main
12678 program and the overlay area.
12680 An overlay loaded into instruction memory and ready for use is called a
12681 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12682 instruction memory. An overlay not present (or only partially present)
12683 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12684 is its address in the larger memory. The mapped address is also called
12685 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12686 called the @dfn{load memory address}, or @dfn{LMA}.
12688 Unfortunately, overlays are not a completely transparent way to adapt a
12689 program to limited instruction memory. They introduce a new set of
12690 global constraints you must keep in mind as you design your program:
12695 Before calling or returning to a function in an overlay, your program
12696 must make sure that overlay is actually mapped. Otherwise, the call or
12697 return will transfer control to the right address, but in the wrong
12698 overlay, and your program will probably crash.
12701 If the process of mapping an overlay is expensive on your system, you
12702 will need to choose your overlays carefully to minimize their effect on
12703 your program's performance.
12706 The executable file you load onto your system must contain each
12707 overlay's instructions, appearing at the overlay's load address, not its
12708 mapped address. However, each overlay's instructions must be relocated
12709 and its symbols defined as if the overlay were at its mapped address.
12710 You can use GNU linker scripts to specify different load and relocation
12711 addresses for pieces of your program; see @ref{Overlay Description,,,
12712 ld.info, Using ld: the GNU linker}.
12715 The procedure for loading executable files onto your system must be able
12716 to load their contents into the larger address space as well as the
12717 instruction and data spaces.
12721 The overlay system described above is rather simple, and could be
12722 improved in many ways:
12727 If your system has suitable bank switch registers or memory management
12728 hardware, you could use those facilities to make an overlay's load area
12729 contents simply appear at their mapped address in instruction space.
12730 This would probably be faster than copying the overlay to its mapped
12731 area in the usual way.
12734 If your overlays are small enough, you could set aside more than one
12735 overlay area, and have more than one overlay mapped at a time.
12738 You can use overlays to manage data, as well as instructions. In
12739 general, data overlays are even less transparent to your design than
12740 code overlays: whereas code overlays only require care when you call or
12741 return to functions, data overlays require care every time you access
12742 the data. Also, if you change the contents of a data overlay, you
12743 must copy its contents back out to its load address before you can copy a
12744 different data overlay into the same mapped area.
12749 @node Overlay Commands
12750 @section Overlay Commands
12752 To use @value{GDBN}'s overlay support, each overlay in your program must
12753 correspond to a separate section of the executable file. The section's
12754 virtual memory address and load memory address must be the overlay's
12755 mapped and load addresses. Identifying overlays with sections allows
12756 @value{GDBN} to determine the appropriate address of a function or
12757 variable, depending on whether the overlay is mapped or not.
12759 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12760 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12765 Disable @value{GDBN}'s overlay support. When overlay support is
12766 disabled, @value{GDBN} assumes that all functions and variables are
12767 always present at their mapped addresses. By default, @value{GDBN}'s
12768 overlay support is disabled.
12770 @item overlay manual
12771 @cindex manual overlay debugging
12772 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12773 relies on you to tell it which overlays are mapped, and which are not,
12774 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12775 commands described below.
12777 @item overlay map-overlay @var{overlay}
12778 @itemx overlay map @var{overlay}
12779 @cindex map an overlay
12780 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12781 be the name of the object file section containing the overlay. When an
12782 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12783 functions and variables at their mapped addresses. @value{GDBN} assumes
12784 that any other overlays whose mapped ranges overlap that of
12785 @var{overlay} are now unmapped.
12787 @item overlay unmap-overlay @var{overlay}
12788 @itemx overlay unmap @var{overlay}
12789 @cindex unmap an overlay
12790 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12791 must be the name of the object file section containing the overlay.
12792 When an overlay is unmapped, @value{GDBN} assumes it can find the
12793 overlay's functions and variables at their load addresses.
12796 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12797 consults a data structure the overlay manager maintains in the inferior
12798 to see which overlays are mapped. For details, see @ref{Automatic
12799 Overlay Debugging}.
12801 @item overlay load-target
12802 @itemx overlay load
12803 @cindex reloading the overlay table
12804 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12805 re-reads the table @value{GDBN} automatically each time the inferior
12806 stops, so this command should only be necessary if you have changed the
12807 overlay mapping yourself using @value{GDBN}. This command is only
12808 useful when using automatic overlay debugging.
12810 @item overlay list-overlays
12811 @itemx overlay list
12812 @cindex listing mapped overlays
12813 Display a list of the overlays currently mapped, along with their mapped
12814 addresses, load addresses, and sizes.
12818 Normally, when @value{GDBN} prints a code address, it includes the name
12819 of the function the address falls in:
12822 (@value{GDBP}) print main
12823 $3 = @{int ()@} 0x11a0 <main>
12826 When overlay debugging is enabled, @value{GDBN} recognizes code in
12827 unmapped overlays, and prints the names of unmapped functions with
12828 asterisks around them. For example, if @code{foo} is a function in an
12829 unmapped overlay, @value{GDBN} prints it this way:
12832 (@value{GDBP}) overlay list
12833 No sections are mapped.
12834 (@value{GDBP}) print foo
12835 $5 = @{int (int)@} 0x100000 <*foo*>
12838 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12842 (@value{GDBP}) overlay list
12843 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12844 mapped at 0x1016 - 0x104a
12845 (@value{GDBP}) print foo
12846 $6 = @{int (int)@} 0x1016 <foo>
12849 When overlay debugging is enabled, @value{GDBN} can find the correct
12850 address for functions and variables in an overlay, whether or not the
12851 overlay is mapped. This allows most @value{GDBN} commands, like
12852 @code{break} and @code{disassemble}, to work normally, even on unmapped
12853 code. However, @value{GDBN}'s breakpoint support has some limitations:
12857 @cindex breakpoints in overlays
12858 @cindex overlays, setting breakpoints in
12859 You can set breakpoints in functions in unmapped overlays, as long as
12860 @value{GDBN} can write to the overlay at its load address.
12862 @value{GDBN} can not set hardware or simulator-based breakpoints in
12863 unmapped overlays. However, if you set a breakpoint at the end of your
12864 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12865 you are using manual overlay management), @value{GDBN} will re-set its
12866 breakpoints properly.
12870 @node Automatic Overlay Debugging
12871 @section Automatic Overlay Debugging
12872 @cindex automatic overlay debugging
12874 @value{GDBN} can automatically track which overlays are mapped and which
12875 are not, given some simple co-operation from the overlay manager in the
12876 inferior. If you enable automatic overlay debugging with the
12877 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12878 looks in the inferior's memory for certain variables describing the
12879 current state of the overlays.
12881 Here are the variables your overlay manager must define to support
12882 @value{GDBN}'s automatic overlay debugging:
12886 @item @code{_ovly_table}:
12887 This variable must be an array of the following structures:
12892 /* The overlay's mapped address. */
12895 /* The size of the overlay, in bytes. */
12896 unsigned long size;
12898 /* The overlay's load address. */
12901 /* Non-zero if the overlay is currently mapped;
12903 unsigned long mapped;
12907 @item @code{_novlys}:
12908 This variable must be a four-byte signed integer, holding the total
12909 number of elements in @code{_ovly_table}.
12913 To decide whether a particular overlay is mapped or not, @value{GDBN}
12914 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12915 @code{lma} members equal the VMA and LMA of the overlay's section in the
12916 executable file. When @value{GDBN} finds a matching entry, it consults
12917 the entry's @code{mapped} member to determine whether the overlay is
12920 In addition, your overlay manager may define a function called
12921 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12922 will silently set a breakpoint there. If the overlay manager then
12923 calls this function whenever it has changed the overlay table, this
12924 will enable @value{GDBN} to accurately keep track of which overlays
12925 are in program memory, and update any breakpoints that may be set
12926 in overlays. This will allow breakpoints to work even if the
12927 overlays are kept in ROM or other non-writable memory while they
12928 are not being executed.
12930 @node Overlay Sample Program
12931 @section Overlay Sample Program
12932 @cindex overlay example program
12934 When linking a program which uses overlays, you must place the overlays
12935 at their load addresses, while relocating them to run at their mapped
12936 addresses. To do this, you must write a linker script (@pxref{Overlay
12937 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12938 since linker scripts are specific to a particular host system, target
12939 architecture, and target memory layout, this manual cannot provide
12940 portable sample code demonstrating @value{GDBN}'s overlay support.
12942 However, the @value{GDBN} source distribution does contain an overlaid
12943 program, with linker scripts for a few systems, as part of its test
12944 suite. The program consists of the following files from
12945 @file{gdb/testsuite/gdb.base}:
12949 The main program file.
12951 A simple overlay manager, used by @file{overlays.c}.
12956 Overlay modules, loaded and used by @file{overlays.c}.
12959 Linker scripts for linking the test program on the @code{d10v-elf}
12960 and @code{m32r-elf} targets.
12963 You can build the test program using the @code{d10v-elf} GCC
12964 cross-compiler like this:
12967 $ d10v-elf-gcc -g -c overlays.c
12968 $ d10v-elf-gcc -g -c ovlymgr.c
12969 $ d10v-elf-gcc -g -c foo.c
12970 $ d10v-elf-gcc -g -c bar.c
12971 $ d10v-elf-gcc -g -c baz.c
12972 $ d10v-elf-gcc -g -c grbx.c
12973 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12974 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12977 The build process is identical for any other architecture, except that
12978 you must substitute the appropriate compiler and linker script for the
12979 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12983 @chapter Using @value{GDBN} with Different Languages
12986 Although programming languages generally have common aspects, they are
12987 rarely expressed in the same manner. For instance, in ANSI C,
12988 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12989 Modula-2, it is accomplished by @code{p^}. Values can also be
12990 represented (and displayed) differently. Hex numbers in C appear as
12991 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12993 @cindex working language
12994 Language-specific information is built into @value{GDBN} for some languages,
12995 allowing you to express operations like the above in your program's
12996 native language, and allowing @value{GDBN} to output values in a manner
12997 consistent with the syntax of your program's native language. The
12998 language you use to build expressions is called the @dfn{working
13002 * Setting:: Switching between source languages
13003 * Show:: Displaying the language
13004 * Checks:: Type and range checks
13005 * Supported Languages:: Supported languages
13006 * Unsupported Languages:: Unsupported languages
13010 @section Switching Between Source Languages
13012 There are two ways to control the working language---either have @value{GDBN}
13013 set it automatically, or select it manually yourself. You can use the
13014 @code{set language} command for either purpose. On startup, @value{GDBN}
13015 defaults to setting the language automatically. The working language is
13016 used to determine how expressions you type are interpreted, how values
13019 In addition to the working language, every source file that
13020 @value{GDBN} knows about has its own working language. For some object
13021 file formats, the compiler might indicate which language a particular
13022 source file is in. However, most of the time @value{GDBN} infers the
13023 language from the name of the file. The language of a source file
13024 controls whether C@t{++} names are demangled---this way @code{backtrace} can
13025 show each frame appropriately for its own language. There is no way to
13026 set the language of a source file from within @value{GDBN}, but you can
13027 set the language associated with a filename extension. @xref{Show, ,
13028 Displaying the Language}.
13030 This is most commonly a problem when you use a program, such
13031 as @code{cfront} or @code{f2c}, that generates C but is written in
13032 another language. In that case, make the
13033 program use @code{#line} directives in its C output; that way
13034 @value{GDBN} will know the correct language of the source code of the original
13035 program, and will display that source code, not the generated C code.
13038 * Filenames:: Filename extensions and languages.
13039 * Manually:: Setting the working language manually
13040 * Automatically:: Having @value{GDBN} infer the source language
13044 @subsection List of Filename Extensions and Languages
13046 If a source file name ends in one of the following extensions, then
13047 @value{GDBN} infers that its language is the one indicated.
13065 C@t{++} source file
13071 Objective-C source file
13075 Fortran source file
13078 Modula-2 source file
13082 Assembler source file. This actually behaves almost like C, but
13083 @value{GDBN} does not skip over function prologues when stepping.
13086 In addition, you may set the language associated with a filename
13087 extension. @xref{Show, , Displaying the Language}.
13090 @subsection Setting the Working Language
13092 If you allow @value{GDBN} to set the language automatically,
13093 expressions are interpreted the same way in your debugging session and
13096 @kindex set language
13097 If you wish, you may set the language manually. To do this, issue the
13098 command @samp{set language @var{lang}}, where @var{lang} is the name of
13099 a language, such as
13100 @code{c} or @code{modula-2}.
13101 For a list of the supported languages, type @samp{set language}.
13103 Setting the language manually prevents @value{GDBN} from updating the working
13104 language automatically. This can lead to confusion if you try
13105 to debug a program when the working language is not the same as the
13106 source language, when an expression is acceptable to both
13107 languages---but means different things. For instance, if the current
13108 source file were written in C, and @value{GDBN} was parsing Modula-2, a
13116 might not have the effect you intended. In C, this means to add
13117 @code{b} and @code{c} and place the result in @code{a}. The result
13118 printed would be the value of @code{a}. In Modula-2, this means to compare
13119 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
13121 @node Automatically
13122 @subsection Having @value{GDBN} Infer the Source Language
13124 To have @value{GDBN} set the working language automatically, use
13125 @samp{set language local} or @samp{set language auto}. @value{GDBN}
13126 then infers the working language. That is, when your program stops in a
13127 frame (usually by encountering a breakpoint), @value{GDBN} sets the
13128 working language to the language recorded for the function in that
13129 frame. If the language for a frame is unknown (that is, if the function
13130 or block corresponding to the frame was defined in a source file that
13131 does not have a recognized extension), the current working language is
13132 not changed, and @value{GDBN} issues a warning.
13134 This may not seem necessary for most programs, which are written
13135 entirely in one source language. However, program modules and libraries
13136 written in one source language can be used by a main program written in
13137 a different source language. Using @samp{set language auto} in this
13138 case frees you from having to set the working language manually.
13141 @section Displaying the Language
13143 The following commands help you find out which language is the
13144 working language, and also what language source files were written in.
13147 @item show language
13148 @kindex show language
13149 Display the current working language. This is the
13150 language you can use with commands such as @code{print} to
13151 build and compute expressions that may involve variables in your program.
13154 @kindex info frame@r{, show the source language}
13155 Display the source language for this frame. This language becomes the
13156 working language if you use an identifier from this frame.
13157 @xref{Frame Info, ,Information about a Frame}, to identify the other
13158 information listed here.
13161 @kindex info source@r{, show the source language}
13162 Display the source language of this source file.
13163 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
13164 information listed here.
13167 In unusual circumstances, you may have source files with extensions
13168 not in the standard list. You can then set the extension associated
13169 with a language explicitly:
13172 @item set extension-language @var{ext} @var{language}
13173 @kindex set extension-language
13174 Tell @value{GDBN} that source files with extension @var{ext} are to be
13175 assumed as written in the source language @var{language}.
13177 @item info extensions
13178 @kindex info extensions
13179 List all the filename extensions and the associated languages.
13183 @section Type and Range Checking
13185 Some languages are designed to guard you against making seemingly common
13186 errors through a series of compile- and run-time checks. These include
13187 checking the type of arguments to functions and operators and making
13188 sure mathematical overflows are caught at run time. Checks such as
13189 these help to ensure a program's correctness once it has been compiled
13190 by eliminating type mismatches and providing active checks for range
13191 errors when your program is running.
13193 By default @value{GDBN} checks for these errors according to the
13194 rules of the current source language. Although @value{GDBN} does not check
13195 the statements in your program, it can check expressions entered directly
13196 into @value{GDBN} for evaluation via the @code{print} command, for example.
13199 * Type Checking:: An overview of type checking
13200 * Range Checking:: An overview of range checking
13203 @cindex type checking
13204 @cindex checks, type
13205 @node Type Checking
13206 @subsection An Overview of Type Checking
13208 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
13209 arguments to operators and functions have to be of the correct type,
13210 otherwise an error occurs. These checks prevent type mismatch
13211 errors from ever causing any run-time problems. For example,
13214 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
13216 (@value{GDBP}) print obj.my_method (0)
13219 (@value{GDBP}) print obj.my_method (0x1234)
13220 Cannot resolve method klass::my_method to any overloaded instance
13223 The second example fails because in C@t{++} the integer constant
13224 @samp{0x1234} is not type-compatible with the pointer parameter type.
13226 For the expressions you use in @value{GDBN} commands, you can tell
13227 @value{GDBN} to not enforce strict type checking or
13228 to treat any mismatches as errors and abandon the expression;
13229 When type checking is disabled, @value{GDBN} successfully evaluates
13230 expressions like the second example above.
13232 Even if type checking is off, there may be other reasons
13233 related to type that prevent @value{GDBN} from evaluating an expression.
13234 For instance, @value{GDBN} does not know how to add an @code{int} and
13235 a @code{struct foo}. These particular type errors have nothing to do
13236 with the language in use and usually arise from expressions which make
13237 little sense to evaluate anyway.
13239 @value{GDBN} provides some additional commands for controlling type checking:
13241 @kindex set check type
13242 @kindex show check type
13244 @item set check type on
13245 @itemx set check type off
13246 Set strict type checking on or off. If any type mismatches occur in
13247 evaluating an expression while type checking is on, @value{GDBN} prints a
13248 message and aborts evaluation of the expression.
13250 @item show check type
13251 Show the current setting of type checking and whether @value{GDBN}
13252 is enforcing strict type checking rules.
13255 @cindex range checking
13256 @cindex checks, range
13257 @node Range Checking
13258 @subsection An Overview of Range Checking
13260 In some languages (such as Modula-2), it is an error to exceed the
13261 bounds of a type; this is enforced with run-time checks. Such range
13262 checking is meant to ensure program correctness by making sure
13263 computations do not overflow, or indices on an array element access do
13264 not exceed the bounds of the array.
13266 For expressions you use in @value{GDBN} commands, you can tell
13267 @value{GDBN} to treat range errors in one of three ways: ignore them,
13268 always treat them as errors and abandon the expression, or issue
13269 warnings but evaluate the expression anyway.
13271 A range error can result from numerical overflow, from exceeding an
13272 array index bound, or when you type a constant that is not a member
13273 of any type. Some languages, however, do not treat overflows as an
13274 error. In many implementations of C, mathematical overflow causes the
13275 result to ``wrap around'' to lower values---for example, if @var{m} is
13276 the largest integer value, and @var{s} is the smallest, then
13279 @var{m} + 1 @result{} @var{s}
13282 This, too, is specific to individual languages, and in some cases
13283 specific to individual compilers or machines. @xref{Supported Languages, ,
13284 Supported Languages}, for further details on specific languages.
13286 @value{GDBN} provides some additional commands for controlling the range checker:
13288 @kindex set check range
13289 @kindex show check range
13291 @item set check range auto
13292 Set range checking on or off based on the current working language.
13293 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13296 @item set check range on
13297 @itemx set check range off
13298 Set range checking on or off, overriding the default setting for the
13299 current working language. A warning is issued if the setting does not
13300 match the language default. If a range error occurs and range checking is on,
13301 then a message is printed and evaluation of the expression is aborted.
13303 @item set check range warn
13304 Output messages when the @value{GDBN} range checker detects a range error,
13305 but attempt to evaluate the expression anyway. Evaluating the
13306 expression may still be impossible for other reasons, such as accessing
13307 memory that the process does not own (a typical example from many Unix
13311 Show the current setting of the range checker, and whether or not it is
13312 being set automatically by @value{GDBN}.
13315 @node Supported Languages
13316 @section Supported Languages
13318 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13319 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13320 @c This is false ...
13321 Some @value{GDBN} features may be used in expressions regardless of the
13322 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13323 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13324 ,Expressions}) can be used with the constructs of any supported
13327 The following sections detail to what degree each source language is
13328 supported by @value{GDBN}. These sections are not meant to be language
13329 tutorials or references, but serve only as a reference guide to what the
13330 @value{GDBN} expression parser accepts, and what input and output
13331 formats should look like for different languages. There are many good
13332 books written on each of these languages; please look to these for a
13333 language reference or tutorial.
13336 * C:: C and C@t{++}
13339 * Objective-C:: Objective-C
13340 * OpenCL C:: OpenCL C
13341 * Fortran:: Fortran
13343 * Modula-2:: Modula-2
13348 @subsection C and C@t{++}
13350 @cindex C and C@t{++}
13351 @cindex expressions in C or C@t{++}
13353 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13354 to both languages. Whenever this is the case, we discuss those languages
13358 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13359 @cindex @sc{gnu} C@t{++}
13360 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13361 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13362 effectively, you must compile your C@t{++} programs with a supported
13363 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13364 compiler (@code{aCC}).
13367 * C Operators:: C and C@t{++} operators
13368 * C Constants:: C and C@t{++} constants
13369 * C Plus Plus Expressions:: C@t{++} expressions
13370 * C Defaults:: Default settings for C and C@t{++}
13371 * C Checks:: C and C@t{++} type and range checks
13372 * Debugging C:: @value{GDBN} and C
13373 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13374 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13378 @subsubsection C and C@t{++} Operators
13380 @cindex C and C@t{++} operators
13382 Operators must be defined on values of specific types. For instance,
13383 @code{+} is defined on numbers, but not on structures. Operators are
13384 often defined on groups of types.
13386 For the purposes of C and C@t{++}, the following definitions hold:
13391 @emph{Integral types} include @code{int} with any of its storage-class
13392 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13395 @emph{Floating-point types} include @code{float}, @code{double}, and
13396 @code{long double} (if supported by the target platform).
13399 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13402 @emph{Scalar types} include all of the above.
13407 The following operators are supported. They are listed here
13408 in order of increasing precedence:
13412 The comma or sequencing operator. Expressions in a comma-separated list
13413 are evaluated from left to right, with the result of the entire
13414 expression being the last expression evaluated.
13417 Assignment. The value of an assignment expression is the value
13418 assigned. Defined on scalar types.
13421 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13422 and translated to @w{@code{@var{a} = @var{a op b}}}.
13423 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13424 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13425 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13428 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13429 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13433 Logical @sc{or}. Defined on integral types.
13436 Logical @sc{and}. Defined on integral types.
13439 Bitwise @sc{or}. Defined on integral types.
13442 Bitwise exclusive-@sc{or}. Defined on integral types.
13445 Bitwise @sc{and}. Defined on integral types.
13448 Equality and inequality. Defined on scalar types. The value of these
13449 expressions is 0 for false and non-zero for true.
13451 @item <@r{, }>@r{, }<=@r{, }>=
13452 Less than, greater than, less than or equal, greater than or equal.
13453 Defined on scalar types. The value of these expressions is 0 for false
13454 and non-zero for true.
13457 left shift, and right shift. Defined on integral types.
13460 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13463 Addition and subtraction. Defined on integral types, floating-point types and
13466 @item *@r{, }/@r{, }%
13467 Multiplication, division, and modulus. Multiplication and division are
13468 defined on integral and floating-point types. Modulus is defined on
13472 Increment and decrement. When appearing before a variable, the
13473 operation is performed before the variable is used in an expression;
13474 when appearing after it, the variable's value is used before the
13475 operation takes place.
13478 Pointer dereferencing. Defined on pointer types. Same precedence as
13482 Address operator. Defined on variables. Same precedence as @code{++}.
13484 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13485 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13486 to examine the address
13487 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13491 Negative. Defined on integral and floating-point types. Same
13492 precedence as @code{++}.
13495 Logical negation. Defined on integral types. Same precedence as
13499 Bitwise complement operator. Defined on integral types. Same precedence as
13504 Structure member, and pointer-to-structure member. For convenience,
13505 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13506 pointer based on the stored type information.
13507 Defined on @code{struct} and @code{union} data.
13510 Dereferences of pointers to members.
13513 Array indexing. @code{@var{a}[@var{i}]} is defined as
13514 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13517 Function parameter list. Same precedence as @code{->}.
13520 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13521 and @code{class} types.
13524 Doubled colons also represent the @value{GDBN} scope operator
13525 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13529 If an operator is redefined in the user code, @value{GDBN} usually
13530 attempts to invoke the redefined version instead of using the operator's
13531 predefined meaning.
13534 @subsubsection C and C@t{++} Constants
13536 @cindex C and C@t{++} constants
13538 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13543 Integer constants are a sequence of digits. Octal constants are
13544 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13545 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13546 @samp{l}, specifying that the constant should be treated as a
13550 Floating point constants are a sequence of digits, followed by a decimal
13551 point, followed by a sequence of digits, and optionally followed by an
13552 exponent. An exponent is of the form:
13553 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13554 sequence of digits. The @samp{+} is optional for positive exponents.
13555 A floating-point constant may also end with a letter @samp{f} or
13556 @samp{F}, specifying that the constant should be treated as being of
13557 the @code{float} (as opposed to the default @code{double}) type; or with
13558 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13562 Enumerated constants consist of enumerated identifiers, or their
13563 integral equivalents.
13566 Character constants are a single character surrounded by single quotes
13567 (@code{'}), or a number---the ordinal value of the corresponding character
13568 (usually its @sc{ascii} value). Within quotes, the single character may
13569 be represented by a letter or by @dfn{escape sequences}, which are of
13570 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13571 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13572 @samp{@var{x}} is a predefined special character---for example,
13573 @samp{\n} for newline.
13575 Wide character constants can be written by prefixing a character
13576 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13577 form of @samp{x}. The target wide character set is used when
13578 computing the value of this constant (@pxref{Character Sets}).
13581 String constants are a sequence of character constants surrounded by
13582 double quotes (@code{"}). Any valid character constant (as described
13583 above) may appear. Double quotes within the string must be preceded by
13584 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13587 Wide string constants can be written by prefixing a string constant
13588 with @samp{L}, as in C. The target wide character set is used when
13589 computing the value of this constant (@pxref{Character Sets}).
13592 Pointer constants are an integral value. You can also write pointers
13593 to constants using the C operator @samp{&}.
13596 Array constants are comma-separated lists surrounded by braces @samp{@{}
13597 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13598 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13599 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13602 @node C Plus Plus Expressions
13603 @subsubsection C@t{++} Expressions
13605 @cindex expressions in C@t{++}
13606 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13608 @cindex debugging C@t{++} programs
13609 @cindex C@t{++} compilers
13610 @cindex debug formats and C@t{++}
13611 @cindex @value{NGCC} and C@t{++}
13613 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13614 the proper compiler and the proper debug format. Currently,
13615 @value{GDBN} works best when debugging C@t{++} code that is compiled
13616 with the most recent version of @value{NGCC} possible. The DWARF
13617 debugging format is preferred; @value{NGCC} defaults to this on most
13618 popular platforms. Other compilers and/or debug formats are likely to
13619 work badly or not at all when using @value{GDBN} to debug C@t{++}
13620 code. @xref{Compilation}.
13625 @cindex member functions
13627 Member function calls are allowed; you can use expressions like
13630 count = aml->GetOriginal(x, y)
13633 @vindex this@r{, inside C@t{++} member functions}
13634 @cindex namespace in C@t{++}
13636 While a member function is active (in the selected stack frame), your
13637 expressions have the same namespace available as the member function;
13638 that is, @value{GDBN} allows implicit references to the class instance
13639 pointer @code{this} following the same rules as C@t{++}. @code{using}
13640 declarations in the current scope are also respected by @value{GDBN}.
13642 @cindex call overloaded functions
13643 @cindex overloaded functions, calling
13644 @cindex type conversions in C@t{++}
13646 You can call overloaded functions; @value{GDBN} resolves the function
13647 call to the right definition, with some restrictions. @value{GDBN} does not
13648 perform overload resolution involving user-defined type conversions,
13649 calls to constructors, or instantiations of templates that do not exist
13650 in the program. It also cannot handle ellipsis argument lists or
13653 It does perform integral conversions and promotions, floating-point
13654 promotions, arithmetic conversions, pointer conversions, conversions of
13655 class objects to base classes, and standard conversions such as those of
13656 functions or arrays to pointers; it requires an exact match on the
13657 number of function arguments.
13659 Overload resolution is always performed, unless you have specified
13660 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13661 ,@value{GDBN} Features for C@t{++}}.
13663 You must specify @code{set overload-resolution off} in order to use an
13664 explicit function signature to call an overloaded function, as in
13666 p 'foo(char,int)'('x', 13)
13669 The @value{GDBN} command-completion facility can simplify this;
13670 see @ref{Completion, ,Command Completion}.
13672 @cindex reference declarations
13674 @value{GDBN} understands variables declared as C@t{++} references; you can use
13675 them in expressions just as you do in C@t{++} source---they are automatically
13678 In the parameter list shown when @value{GDBN} displays a frame, the values of
13679 reference variables are not displayed (unlike other variables); this
13680 avoids clutter, since references are often used for large structures.
13681 The @emph{address} of a reference variable is always shown, unless
13682 you have specified @samp{set print address off}.
13685 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13686 expressions can use it just as expressions in your program do. Since
13687 one scope may be defined in another, you can use @code{::} repeatedly if
13688 necessary, for example in an expression like
13689 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13690 resolving name scope by reference to source files, in both C and C@t{++}
13691 debugging (@pxref{Variables, ,Program Variables}).
13694 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13699 @subsubsection C and C@t{++} Defaults
13701 @cindex C and C@t{++} defaults
13703 If you allow @value{GDBN} to set range checking automatically, it
13704 defaults to @code{off} whenever the working language changes to
13705 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13706 selects the working language.
13708 If you allow @value{GDBN} to set the language automatically, it
13709 recognizes source files whose names end with @file{.c}, @file{.C}, or
13710 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13711 these files, it sets the working language to C or C@t{++}.
13712 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13713 for further details.
13716 @subsubsection C and C@t{++} Type and Range Checks
13718 @cindex C and C@t{++} checks
13720 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13721 checking is used. However, if you turn type checking off, @value{GDBN}
13722 will allow certain non-standard conversions, such as promoting integer
13723 constants to pointers.
13725 Range checking, if turned on, is done on mathematical operations. Array
13726 indices are not checked, since they are often used to index a pointer
13727 that is not itself an array.
13730 @subsubsection @value{GDBN} and C
13732 The @code{set print union} and @code{show print union} commands apply to
13733 the @code{union} type. When set to @samp{on}, any @code{union} that is
13734 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13735 appears as @samp{@{...@}}.
13737 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13738 with pointers and a memory allocation function. @xref{Expressions,
13741 @node Debugging C Plus Plus
13742 @subsubsection @value{GDBN} Features for C@t{++}
13744 @cindex commands for C@t{++}
13746 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13747 designed specifically for use with C@t{++}. Here is a summary:
13750 @cindex break in overloaded functions
13751 @item @r{breakpoint menus}
13752 When you want a breakpoint in a function whose name is overloaded,
13753 @value{GDBN} has the capability to display a menu of possible breakpoint
13754 locations to help you specify which function definition you want.
13755 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13757 @cindex overloading in C@t{++}
13758 @item rbreak @var{regex}
13759 Setting breakpoints using regular expressions is helpful for setting
13760 breakpoints on overloaded functions that are not members of any special
13762 @xref{Set Breaks, ,Setting Breakpoints}.
13764 @cindex C@t{++} exception handling
13766 @itemx catch rethrow
13768 Debug C@t{++} exception handling using these commands. @xref{Set
13769 Catchpoints, , Setting Catchpoints}.
13771 @cindex inheritance
13772 @item ptype @var{typename}
13773 Print inheritance relationships as well as other information for type
13775 @xref{Symbols, ,Examining the Symbol Table}.
13777 @item info vtbl @var{expression}.
13778 The @code{info vtbl} command can be used to display the virtual
13779 method tables of the object computed by @var{expression}. This shows
13780 one entry per virtual table; there may be multiple virtual tables when
13781 multiple inheritance is in use.
13783 @cindex C@t{++} symbol display
13784 @item set print demangle
13785 @itemx show print demangle
13786 @itemx set print asm-demangle
13787 @itemx show print asm-demangle
13788 Control whether C@t{++} symbols display in their source form, both when
13789 displaying code as C@t{++} source and when displaying disassemblies.
13790 @xref{Print Settings, ,Print Settings}.
13792 @item set print object
13793 @itemx show print object
13794 Choose whether to print derived (actual) or declared types of objects.
13795 @xref{Print Settings, ,Print Settings}.
13797 @item set print vtbl
13798 @itemx show print vtbl
13799 Control the format for printing virtual function tables.
13800 @xref{Print Settings, ,Print Settings}.
13801 (The @code{vtbl} commands do not work on programs compiled with the HP
13802 ANSI C@t{++} compiler (@code{aCC}).)
13804 @kindex set overload-resolution
13805 @cindex overloaded functions, overload resolution
13806 @item set overload-resolution on
13807 Enable overload resolution for C@t{++} expression evaluation. The default
13808 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13809 and searches for a function whose signature matches the argument types,
13810 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13811 Expressions, ,C@t{++} Expressions}, for details).
13812 If it cannot find a match, it emits a message.
13814 @item set overload-resolution off
13815 Disable overload resolution for C@t{++} expression evaluation. For
13816 overloaded functions that are not class member functions, @value{GDBN}
13817 chooses the first function of the specified name that it finds in the
13818 symbol table, whether or not its arguments are of the correct type. For
13819 overloaded functions that are class member functions, @value{GDBN}
13820 searches for a function whose signature @emph{exactly} matches the
13823 @kindex show overload-resolution
13824 @item show overload-resolution
13825 Show the current setting of overload resolution.
13827 @item @r{Overloaded symbol names}
13828 You can specify a particular definition of an overloaded symbol, using
13829 the same notation that is used to declare such symbols in C@t{++}: type
13830 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13831 also use the @value{GDBN} command-line word completion facilities to list the
13832 available choices, or to finish the type list for you.
13833 @xref{Completion,, Command Completion}, for details on how to do this.
13836 @node Decimal Floating Point
13837 @subsubsection Decimal Floating Point format
13838 @cindex decimal floating point format
13840 @value{GDBN} can examine, set and perform computations with numbers in
13841 decimal floating point format, which in the C language correspond to the
13842 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13843 specified by the extension to support decimal floating-point arithmetic.
13845 There are two encodings in use, depending on the architecture: BID (Binary
13846 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13847 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13850 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13851 to manipulate decimal floating point numbers, it is not possible to convert
13852 (using a cast, for example) integers wider than 32-bit to decimal float.
13854 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13855 point computations, error checking in decimal float operations ignores
13856 underflow, overflow and divide by zero exceptions.
13858 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13859 to inspect @code{_Decimal128} values stored in floating point registers.
13860 See @ref{PowerPC,,PowerPC} for more details.
13866 @value{GDBN} can be used to debug programs written in D and compiled with
13867 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13868 specific feature --- dynamic arrays.
13873 @cindex Go (programming language)
13874 @value{GDBN} can be used to debug programs written in Go and compiled with
13875 @file{gccgo} or @file{6g} compilers.
13877 Here is a summary of the Go-specific features and restrictions:
13880 @cindex current Go package
13881 @item The current Go package
13882 The name of the current package does not need to be specified when
13883 specifying global variables and functions.
13885 For example, given the program:
13889 var myglob = "Shall we?"
13895 When stopped inside @code{main} either of these work:
13899 (gdb) p main.myglob
13902 @cindex builtin Go types
13903 @item Builtin Go types
13904 The @code{string} type is recognized by @value{GDBN} and is printed
13907 @cindex builtin Go functions
13908 @item Builtin Go functions
13909 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13910 function and handles it internally.
13912 @cindex restrictions on Go expressions
13913 @item Restrictions on Go expressions
13914 All Go operators are supported except @code{&^}.
13915 The Go @code{_} ``blank identifier'' is not supported.
13916 Automatic dereferencing of pointers is not supported.
13920 @subsection Objective-C
13922 @cindex Objective-C
13923 This section provides information about some commands and command
13924 options that are useful for debugging Objective-C code. See also
13925 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13926 few more commands specific to Objective-C support.
13929 * Method Names in Commands::
13930 * The Print Command with Objective-C::
13933 @node Method Names in Commands
13934 @subsubsection Method Names in Commands
13936 The following commands have been extended to accept Objective-C method
13937 names as line specifications:
13939 @kindex clear@r{, and Objective-C}
13940 @kindex break@r{, and Objective-C}
13941 @kindex info line@r{, and Objective-C}
13942 @kindex jump@r{, and Objective-C}
13943 @kindex list@r{, and Objective-C}
13947 @item @code{info line}
13952 A fully qualified Objective-C method name is specified as
13955 -[@var{Class} @var{methodName}]
13958 where the minus sign is used to indicate an instance method and a
13959 plus sign (not shown) is used to indicate a class method. The class
13960 name @var{Class} and method name @var{methodName} are enclosed in
13961 brackets, similar to the way messages are specified in Objective-C
13962 source code. For example, to set a breakpoint at the @code{create}
13963 instance method of class @code{Fruit} in the program currently being
13967 break -[Fruit create]
13970 To list ten program lines around the @code{initialize} class method,
13974 list +[NSText initialize]
13977 In the current version of @value{GDBN}, the plus or minus sign is
13978 required. In future versions of @value{GDBN}, the plus or minus
13979 sign will be optional, but you can use it to narrow the search. It
13980 is also possible to specify just a method name:
13986 You must specify the complete method name, including any colons. If
13987 your program's source files contain more than one @code{create} method,
13988 you'll be presented with a numbered list of classes that implement that
13989 method. Indicate your choice by number, or type @samp{0} to exit if
13992 As another example, to clear a breakpoint established at the
13993 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13996 clear -[NSWindow makeKeyAndOrderFront:]
13999 @node The Print Command with Objective-C
14000 @subsubsection The Print Command With Objective-C
14001 @cindex Objective-C, print objects
14002 @kindex print-object
14003 @kindex po @r{(@code{print-object})}
14005 The print command has also been extended to accept methods. For example:
14008 print -[@var{object} hash]
14011 @cindex print an Objective-C object description
14012 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
14014 will tell @value{GDBN} to send the @code{hash} message to @var{object}
14015 and print the result. Also, an additional command has been added,
14016 @code{print-object} or @code{po} for short, which is meant to print
14017 the description of an object. However, this command may only work
14018 with certain Objective-C libraries that have a particular hook
14019 function, @code{_NSPrintForDebugger}, defined.
14022 @subsection OpenCL C
14025 This section provides information about @value{GDBN}s OpenCL C support.
14028 * OpenCL C Datatypes::
14029 * OpenCL C Expressions::
14030 * OpenCL C Operators::
14033 @node OpenCL C Datatypes
14034 @subsubsection OpenCL C Datatypes
14036 @cindex OpenCL C Datatypes
14037 @value{GDBN} supports the builtin scalar and vector datatypes specified
14038 by OpenCL 1.1. In addition the half- and double-precision floating point
14039 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
14040 extensions are also known to @value{GDBN}.
14042 @node OpenCL C Expressions
14043 @subsubsection OpenCL C Expressions
14045 @cindex OpenCL C Expressions
14046 @value{GDBN} supports accesses to vector components including the access as
14047 lvalue where possible. Since OpenCL C is based on C99 most C expressions
14048 supported by @value{GDBN} can be used as well.
14050 @node OpenCL C Operators
14051 @subsubsection OpenCL C Operators
14053 @cindex OpenCL C Operators
14054 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
14058 @subsection Fortran
14059 @cindex Fortran-specific support in @value{GDBN}
14061 @value{GDBN} can be used to debug programs written in Fortran, but it
14062 currently supports only the features of Fortran 77 language.
14064 @cindex trailing underscore, in Fortran symbols
14065 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
14066 among them) append an underscore to the names of variables and
14067 functions. When you debug programs compiled by those compilers, you
14068 will need to refer to variables and functions with a trailing
14072 * Fortran Operators:: Fortran operators and expressions
14073 * Fortran Defaults:: Default settings for Fortran
14074 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
14077 @node Fortran Operators
14078 @subsubsection Fortran Operators and Expressions
14080 @cindex Fortran operators and expressions
14082 Operators must be defined on values of specific types. For instance,
14083 @code{+} is defined on numbers, but not on characters or other non-
14084 arithmetic types. Operators are often defined on groups of types.
14088 The exponentiation operator. It raises the first operand to the power
14092 The range operator. Normally used in the form of array(low:high) to
14093 represent a section of array.
14096 The access component operator. Normally used to access elements in derived
14097 types. Also suitable for unions. As unions aren't part of regular Fortran,
14098 this can only happen when accessing a register that uses a gdbarch-defined
14102 @node Fortran Defaults
14103 @subsubsection Fortran Defaults
14105 @cindex Fortran Defaults
14107 Fortran symbols are usually case-insensitive, so @value{GDBN} by
14108 default uses case-insensitive matches for Fortran symbols. You can
14109 change that with the @samp{set case-insensitive} command, see
14110 @ref{Symbols}, for the details.
14112 @node Special Fortran Commands
14113 @subsubsection Special Fortran Commands
14115 @cindex Special Fortran commands
14117 @value{GDBN} has some commands to support Fortran-specific features,
14118 such as displaying common blocks.
14121 @cindex @code{COMMON} blocks, Fortran
14122 @kindex info common
14123 @item info common @r{[}@var{common-name}@r{]}
14124 This command prints the values contained in the Fortran @code{COMMON}
14125 block whose name is @var{common-name}. With no argument, the names of
14126 all @code{COMMON} blocks visible at the current program location are
14133 @cindex Pascal support in @value{GDBN}, limitations
14134 Debugging Pascal programs which use sets, subranges, file variables, or
14135 nested functions does not currently work. @value{GDBN} does not support
14136 entering expressions, printing values, or similar features using Pascal
14139 The Pascal-specific command @code{set print pascal_static-members}
14140 controls whether static members of Pascal objects are displayed.
14141 @xref{Print Settings, pascal_static-members}.
14144 @subsection Modula-2
14146 @cindex Modula-2, @value{GDBN} support
14148 The extensions made to @value{GDBN} to support Modula-2 only support
14149 output from the @sc{gnu} Modula-2 compiler (which is currently being
14150 developed). Other Modula-2 compilers are not currently supported, and
14151 attempting to debug executables produced by them is most likely
14152 to give an error as @value{GDBN} reads in the executable's symbol
14155 @cindex expressions in Modula-2
14157 * M2 Operators:: Built-in operators
14158 * Built-In Func/Proc:: Built-in functions and procedures
14159 * M2 Constants:: Modula-2 constants
14160 * M2 Types:: Modula-2 types
14161 * M2 Defaults:: Default settings for Modula-2
14162 * Deviations:: Deviations from standard Modula-2
14163 * M2 Checks:: Modula-2 type and range checks
14164 * M2 Scope:: The scope operators @code{::} and @code{.}
14165 * GDB/M2:: @value{GDBN} and Modula-2
14169 @subsubsection Operators
14170 @cindex Modula-2 operators
14172 Operators must be defined on values of specific types. For instance,
14173 @code{+} is defined on numbers, but not on structures. Operators are
14174 often defined on groups of types. For the purposes of Modula-2, the
14175 following definitions hold:
14180 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
14184 @emph{Character types} consist of @code{CHAR} and its subranges.
14187 @emph{Floating-point types} consist of @code{REAL}.
14190 @emph{Pointer types} consist of anything declared as @code{POINTER TO
14194 @emph{Scalar types} consist of all of the above.
14197 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
14200 @emph{Boolean types} consist of @code{BOOLEAN}.
14204 The following operators are supported, and appear in order of
14205 increasing precedence:
14209 Function argument or array index separator.
14212 Assignment. The value of @var{var} @code{:=} @var{value} is
14216 Less than, greater than on integral, floating-point, or enumerated
14220 Less than or equal to, greater than or equal to
14221 on integral, floating-point and enumerated types, or set inclusion on
14222 set types. Same precedence as @code{<}.
14224 @item =@r{, }<>@r{, }#
14225 Equality and two ways of expressing inequality, valid on scalar types.
14226 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
14227 available for inequality, since @code{#} conflicts with the script
14231 Set membership. Defined on set types and the types of their members.
14232 Same precedence as @code{<}.
14235 Boolean disjunction. Defined on boolean types.
14238 Boolean conjunction. Defined on boolean types.
14241 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
14244 Addition and subtraction on integral and floating-point types, or union
14245 and difference on set types.
14248 Multiplication on integral and floating-point types, or set intersection
14252 Division on floating-point types, or symmetric set difference on set
14253 types. Same precedence as @code{*}.
14256 Integer division and remainder. Defined on integral types. Same
14257 precedence as @code{*}.
14260 Negative. Defined on @code{INTEGER} and @code{REAL} data.
14263 Pointer dereferencing. Defined on pointer types.
14266 Boolean negation. Defined on boolean types. Same precedence as
14270 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
14271 precedence as @code{^}.
14274 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
14277 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
14281 @value{GDBN} and Modula-2 scope operators.
14285 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14286 treats the use of the operator @code{IN}, or the use of operators
14287 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14288 @code{<=}, and @code{>=} on sets as an error.
14292 @node Built-In Func/Proc
14293 @subsubsection Built-in Functions and Procedures
14294 @cindex Modula-2 built-ins
14296 Modula-2 also makes available several built-in procedures and functions.
14297 In describing these, the following metavariables are used:
14302 represents an @code{ARRAY} variable.
14305 represents a @code{CHAR} constant or variable.
14308 represents a variable or constant of integral type.
14311 represents an identifier that belongs to a set. Generally used in the
14312 same function with the metavariable @var{s}. The type of @var{s} should
14313 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14316 represents a variable or constant of integral or floating-point type.
14319 represents a variable or constant of floating-point type.
14325 represents a variable.
14328 represents a variable or constant of one of many types. See the
14329 explanation of the function for details.
14332 All Modula-2 built-in procedures also return a result, described below.
14336 Returns the absolute value of @var{n}.
14339 If @var{c} is a lower case letter, it returns its upper case
14340 equivalent, otherwise it returns its argument.
14343 Returns the character whose ordinal value is @var{i}.
14346 Decrements the value in the variable @var{v} by one. Returns the new value.
14348 @item DEC(@var{v},@var{i})
14349 Decrements the value in the variable @var{v} by @var{i}. Returns the
14352 @item EXCL(@var{m},@var{s})
14353 Removes the element @var{m} from the set @var{s}. Returns the new
14356 @item FLOAT(@var{i})
14357 Returns the floating point equivalent of the integer @var{i}.
14359 @item HIGH(@var{a})
14360 Returns the index of the last member of @var{a}.
14363 Increments the value in the variable @var{v} by one. Returns the new value.
14365 @item INC(@var{v},@var{i})
14366 Increments the value in the variable @var{v} by @var{i}. Returns the
14369 @item INCL(@var{m},@var{s})
14370 Adds the element @var{m} to the set @var{s} if it is not already
14371 there. Returns the new set.
14374 Returns the maximum value of the type @var{t}.
14377 Returns the minimum value of the type @var{t}.
14380 Returns boolean TRUE if @var{i} is an odd number.
14383 Returns the ordinal value of its argument. For example, the ordinal
14384 value of a character is its @sc{ascii} value (on machines supporting the
14385 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14386 integral, character and enumerated types.
14388 @item SIZE(@var{x})
14389 Returns the size of its argument. @var{x} can be a variable or a type.
14391 @item TRUNC(@var{r})
14392 Returns the integral part of @var{r}.
14394 @item TSIZE(@var{x})
14395 Returns the size of its argument. @var{x} can be a variable or a type.
14397 @item VAL(@var{t},@var{i})
14398 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14402 @emph{Warning:} Sets and their operations are not yet supported, so
14403 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14407 @cindex Modula-2 constants
14409 @subsubsection Constants
14411 @value{GDBN} allows you to express the constants of Modula-2 in the following
14417 Integer constants are simply a sequence of digits. When used in an
14418 expression, a constant is interpreted to be type-compatible with the
14419 rest of the expression. Hexadecimal integers are specified by a
14420 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14423 Floating point constants appear as a sequence of digits, followed by a
14424 decimal point and another sequence of digits. An optional exponent can
14425 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14426 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14427 digits of the floating point constant must be valid decimal (base 10)
14431 Character constants consist of a single character enclosed by a pair of
14432 like quotes, either single (@code{'}) or double (@code{"}). They may
14433 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14434 followed by a @samp{C}.
14437 String constants consist of a sequence of characters enclosed by a
14438 pair of like quotes, either single (@code{'}) or double (@code{"}).
14439 Escape sequences in the style of C are also allowed. @xref{C
14440 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14444 Enumerated constants consist of an enumerated identifier.
14447 Boolean constants consist of the identifiers @code{TRUE} and
14451 Pointer constants consist of integral values only.
14454 Set constants are not yet supported.
14458 @subsubsection Modula-2 Types
14459 @cindex Modula-2 types
14461 Currently @value{GDBN} can print the following data types in Modula-2
14462 syntax: array types, record types, set types, pointer types, procedure
14463 types, enumerated types, subrange types and base types. You can also
14464 print the contents of variables declared using these type.
14465 This section gives a number of simple source code examples together with
14466 sample @value{GDBN} sessions.
14468 The first example contains the following section of code:
14477 and you can request @value{GDBN} to interrogate the type and value of
14478 @code{r} and @code{s}.
14481 (@value{GDBP}) print s
14483 (@value{GDBP}) ptype s
14485 (@value{GDBP}) print r
14487 (@value{GDBP}) ptype r
14492 Likewise if your source code declares @code{s} as:
14496 s: SET ['A'..'Z'] ;
14500 then you may query the type of @code{s} by:
14503 (@value{GDBP}) ptype s
14504 type = SET ['A'..'Z']
14508 Note that at present you cannot interactively manipulate set
14509 expressions using the debugger.
14511 The following example shows how you might declare an array in Modula-2
14512 and how you can interact with @value{GDBN} to print its type and contents:
14516 s: ARRAY [-10..10] OF CHAR ;
14520 (@value{GDBP}) ptype s
14521 ARRAY [-10..10] OF CHAR
14524 Note that the array handling is not yet complete and although the type
14525 is printed correctly, expression handling still assumes that all
14526 arrays have a lower bound of zero and not @code{-10} as in the example
14529 Here are some more type related Modula-2 examples:
14533 colour = (blue, red, yellow, green) ;
14534 t = [blue..yellow] ;
14542 The @value{GDBN} interaction shows how you can query the data type
14543 and value of a variable.
14546 (@value{GDBP}) print s
14548 (@value{GDBP}) ptype t
14549 type = [blue..yellow]
14553 In this example a Modula-2 array is declared and its contents
14554 displayed. Observe that the contents are written in the same way as
14555 their @code{C} counterparts.
14559 s: ARRAY [1..5] OF CARDINAL ;
14565 (@value{GDBP}) print s
14566 $1 = @{1, 0, 0, 0, 0@}
14567 (@value{GDBP}) ptype s
14568 type = ARRAY [1..5] OF CARDINAL
14571 The Modula-2 language interface to @value{GDBN} also understands
14572 pointer types as shown in this example:
14576 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14583 and you can request that @value{GDBN} describes the type of @code{s}.
14586 (@value{GDBP}) ptype s
14587 type = POINTER TO ARRAY [1..5] OF CARDINAL
14590 @value{GDBN} handles compound types as we can see in this example.
14591 Here we combine array types, record types, pointer types and subrange
14602 myarray = ARRAY myrange OF CARDINAL ;
14603 myrange = [-2..2] ;
14605 s: POINTER TO ARRAY myrange OF foo ;
14609 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14613 (@value{GDBP}) ptype s
14614 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14617 f3 : ARRAY [-2..2] OF CARDINAL;
14622 @subsubsection Modula-2 Defaults
14623 @cindex Modula-2 defaults
14625 If type and range checking are set automatically by @value{GDBN}, they
14626 both default to @code{on} whenever the working language changes to
14627 Modula-2. This happens regardless of whether you or @value{GDBN}
14628 selected the working language.
14630 If you allow @value{GDBN} to set the language automatically, then entering
14631 code compiled from a file whose name ends with @file{.mod} sets the
14632 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14633 Infer the Source Language}, for further details.
14636 @subsubsection Deviations from Standard Modula-2
14637 @cindex Modula-2, deviations from
14639 A few changes have been made to make Modula-2 programs easier to debug.
14640 This is done primarily via loosening its type strictness:
14644 Unlike in standard Modula-2, pointer constants can be formed by
14645 integers. This allows you to modify pointer variables during
14646 debugging. (In standard Modula-2, the actual address contained in a
14647 pointer variable is hidden from you; it can only be modified
14648 through direct assignment to another pointer variable or expression that
14649 returned a pointer.)
14652 C escape sequences can be used in strings and characters to represent
14653 non-printable characters. @value{GDBN} prints out strings with these
14654 escape sequences embedded. Single non-printable characters are
14655 printed using the @samp{CHR(@var{nnn})} format.
14658 The assignment operator (@code{:=}) returns the value of its right-hand
14662 All built-in procedures both modify @emph{and} return their argument.
14666 @subsubsection Modula-2 Type and Range Checks
14667 @cindex Modula-2 checks
14670 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14673 @c FIXME remove warning when type/range checks added
14675 @value{GDBN} considers two Modula-2 variables type equivalent if:
14679 They are of types that have been declared equivalent via a @code{TYPE
14680 @var{t1} = @var{t2}} statement
14683 They have been declared on the same line. (Note: This is true of the
14684 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14687 As long as type checking is enabled, any attempt to combine variables
14688 whose types are not equivalent is an error.
14690 Range checking is done on all mathematical operations, assignment, array
14691 index bounds, and all built-in functions and procedures.
14694 @subsubsection The Scope Operators @code{::} and @code{.}
14696 @cindex @code{.}, Modula-2 scope operator
14697 @cindex colon, doubled as scope operator
14699 @vindex colon-colon@r{, in Modula-2}
14700 @c Info cannot handle :: but TeX can.
14703 @vindex ::@r{, in Modula-2}
14706 There are a few subtle differences between the Modula-2 scope operator
14707 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14712 @var{module} . @var{id}
14713 @var{scope} :: @var{id}
14717 where @var{scope} is the name of a module or a procedure,
14718 @var{module} the name of a module, and @var{id} is any declared
14719 identifier within your program, except another module.
14721 Using the @code{::} operator makes @value{GDBN} search the scope
14722 specified by @var{scope} for the identifier @var{id}. If it is not
14723 found in the specified scope, then @value{GDBN} searches all scopes
14724 enclosing the one specified by @var{scope}.
14726 Using the @code{.} operator makes @value{GDBN} search the current scope for
14727 the identifier specified by @var{id} that was imported from the
14728 definition module specified by @var{module}. With this operator, it is
14729 an error if the identifier @var{id} was not imported from definition
14730 module @var{module}, or if @var{id} is not an identifier in
14734 @subsubsection @value{GDBN} and Modula-2
14736 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14737 Five subcommands of @code{set print} and @code{show print} apply
14738 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14739 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14740 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14741 analogue in Modula-2.
14743 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14744 with any language, is not useful with Modula-2. Its
14745 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14746 created in Modula-2 as they can in C or C@t{++}. However, because an
14747 address can be specified by an integral constant, the construct
14748 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14750 @cindex @code{#} in Modula-2
14751 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14752 interpreted as the beginning of a comment. Use @code{<>} instead.
14758 The extensions made to @value{GDBN} for Ada only support
14759 output from the @sc{gnu} Ada (GNAT) compiler.
14760 Other Ada compilers are not currently supported, and
14761 attempting to debug executables produced by them is most likely
14765 @cindex expressions in Ada
14767 * Ada Mode Intro:: General remarks on the Ada syntax
14768 and semantics supported by Ada mode
14770 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14771 * Additions to Ada:: Extensions of the Ada expression syntax.
14772 * Stopping Before Main Program:: Debugging the program during elaboration.
14773 * Ada Tasks:: Listing and setting breakpoints in tasks.
14774 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14775 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14777 * Ada Glitches:: Known peculiarities of Ada mode.
14780 @node Ada Mode Intro
14781 @subsubsection Introduction
14782 @cindex Ada mode, general
14784 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14785 syntax, with some extensions.
14786 The philosophy behind the design of this subset is
14790 That @value{GDBN} should provide basic literals and access to operations for
14791 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14792 leaving more sophisticated computations to subprograms written into the
14793 program (which therefore may be called from @value{GDBN}).
14796 That type safety and strict adherence to Ada language restrictions
14797 are not particularly important to the @value{GDBN} user.
14800 That brevity is important to the @value{GDBN} user.
14803 Thus, for brevity, the debugger acts as if all names declared in
14804 user-written packages are directly visible, even if they are not visible
14805 according to Ada rules, thus making it unnecessary to fully qualify most
14806 names with their packages, regardless of context. Where this causes
14807 ambiguity, @value{GDBN} asks the user's intent.
14809 The debugger will start in Ada mode if it detects an Ada main program.
14810 As for other languages, it will enter Ada mode when stopped in a program that
14811 was translated from an Ada source file.
14813 While in Ada mode, you may use `@t{--}' for comments. This is useful
14814 mostly for documenting command files. The standard @value{GDBN} comment
14815 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14816 middle (to allow based literals).
14818 The debugger supports limited overloading. Given a subprogram call in which
14819 the function symbol has multiple definitions, it will use the number of
14820 actual parameters and some information about their types to attempt to narrow
14821 the set of definitions. It also makes very limited use of context, preferring
14822 procedures to functions in the context of the @code{call} command, and
14823 functions to procedures elsewhere.
14825 @node Omissions from Ada
14826 @subsubsection Omissions from Ada
14827 @cindex Ada, omissions from
14829 Here are the notable omissions from the subset:
14833 Only a subset of the attributes are supported:
14837 @t{'First}, @t{'Last}, and @t{'Length}
14838 on array objects (not on types and subtypes).
14841 @t{'Min} and @t{'Max}.
14844 @t{'Pos} and @t{'Val}.
14850 @t{'Range} on array objects (not subtypes), but only as the right
14851 operand of the membership (@code{in}) operator.
14854 @t{'Access}, @t{'Unchecked_Access}, and
14855 @t{'Unrestricted_Access} (a GNAT extension).
14863 @code{Characters.Latin_1} are not available and
14864 concatenation is not implemented. Thus, escape characters in strings are
14865 not currently available.
14868 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14869 equality of representations. They will generally work correctly
14870 for strings and arrays whose elements have integer or enumeration types.
14871 They may not work correctly for arrays whose element
14872 types have user-defined equality, for arrays of real values
14873 (in particular, IEEE-conformant floating point, because of negative
14874 zeroes and NaNs), and for arrays whose elements contain unused bits with
14875 indeterminate values.
14878 The other component-by-component array operations (@code{and}, @code{or},
14879 @code{xor}, @code{not}, and relational tests other than equality)
14880 are not implemented.
14883 @cindex array aggregates (Ada)
14884 @cindex record aggregates (Ada)
14885 @cindex aggregates (Ada)
14886 There is limited support for array and record aggregates. They are
14887 permitted only on the right sides of assignments, as in these examples:
14890 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14891 (@value{GDBP}) set An_Array := (1, others => 0)
14892 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14893 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14894 (@value{GDBP}) set A_Record := (1, "Peter", True);
14895 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14899 discriminant's value by assigning an aggregate has an
14900 undefined effect if that discriminant is used within the record.
14901 However, you can first modify discriminants by directly assigning to
14902 them (which normally would not be allowed in Ada), and then performing an
14903 aggregate assignment. For example, given a variable @code{A_Rec}
14904 declared to have a type such as:
14907 type Rec (Len : Small_Integer := 0) is record
14909 Vals : IntArray (1 .. Len);
14913 you can assign a value with a different size of @code{Vals} with two
14917 (@value{GDBP}) set A_Rec.Len := 4
14918 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14921 As this example also illustrates, @value{GDBN} is very loose about the usual
14922 rules concerning aggregates. You may leave out some of the
14923 components of an array or record aggregate (such as the @code{Len}
14924 component in the assignment to @code{A_Rec} above); they will retain their
14925 original values upon assignment. You may freely use dynamic values as
14926 indices in component associations. You may even use overlapping or
14927 redundant component associations, although which component values are
14928 assigned in such cases is not defined.
14931 Calls to dispatching subprograms are not implemented.
14934 The overloading algorithm is much more limited (i.e., less selective)
14935 than that of real Ada. It makes only limited use of the context in
14936 which a subexpression appears to resolve its meaning, and it is much
14937 looser in its rules for allowing type matches. As a result, some
14938 function calls will be ambiguous, and the user will be asked to choose
14939 the proper resolution.
14942 The @code{new} operator is not implemented.
14945 Entry calls are not implemented.
14948 Aside from printing, arithmetic operations on the native VAX floating-point
14949 formats are not supported.
14952 It is not possible to slice a packed array.
14955 The names @code{True} and @code{False}, when not part of a qualified name,
14956 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14958 Should your program
14959 redefine these names in a package or procedure (at best a dubious practice),
14960 you will have to use fully qualified names to access their new definitions.
14963 @node Additions to Ada
14964 @subsubsection Additions to Ada
14965 @cindex Ada, deviations from
14967 As it does for other languages, @value{GDBN} makes certain generic
14968 extensions to Ada (@pxref{Expressions}):
14972 If the expression @var{E} is a variable residing in memory (typically
14973 a local variable or array element) and @var{N} is a positive integer,
14974 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14975 @var{N}-1 adjacent variables following it in memory as an array. In
14976 Ada, this operator is generally not necessary, since its prime use is
14977 in displaying parts of an array, and slicing will usually do this in
14978 Ada. However, there are occasional uses when debugging programs in
14979 which certain debugging information has been optimized away.
14982 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14983 appears in function or file @var{B}.'' When @var{B} is a file name,
14984 you must typically surround it in single quotes.
14987 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14988 @var{type} that appears at address @var{addr}.''
14991 A name starting with @samp{$} is a convenience variable
14992 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14995 In addition, @value{GDBN} provides a few other shortcuts and outright
14996 additions specific to Ada:
15000 The assignment statement is allowed as an expression, returning
15001 its right-hand operand as its value. Thus, you may enter
15004 (@value{GDBP}) set x := y + 3
15005 (@value{GDBP}) print A(tmp := y + 1)
15009 The semicolon is allowed as an ``operator,'' returning as its value
15010 the value of its right-hand operand.
15011 This allows, for example,
15012 complex conditional breaks:
15015 (@value{GDBP}) break f
15016 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
15020 Rather than use catenation and symbolic character names to introduce special
15021 characters into strings, one may instead use a special bracket notation,
15022 which is also used to print strings. A sequence of characters of the form
15023 @samp{["@var{XX}"]} within a string or character literal denotes the
15024 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
15025 sequence of characters @samp{["""]} also denotes a single quotation mark
15026 in strings. For example,
15028 "One line.["0a"]Next line.["0a"]"
15031 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
15035 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
15036 @t{'Max} is optional (and is ignored in any case). For example, it is valid
15040 (@value{GDBP}) print 'max(x, y)
15044 When printing arrays, @value{GDBN} uses positional notation when the
15045 array has a lower bound of 1, and uses a modified named notation otherwise.
15046 For example, a one-dimensional array of three integers with a lower bound
15047 of 3 might print as
15054 That is, in contrast to valid Ada, only the first component has a @code{=>}
15058 You may abbreviate attributes in expressions with any unique,
15059 multi-character subsequence of
15060 their names (an exact match gets preference).
15061 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
15062 in place of @t{a'length}.
15065 @cindex quoting Ada internal identifiers
15066 Since Ada is case-insensitive, the debugger normally maps identifiers you type
15067 to lower case. The GNAT compiler uses upper-case characters for
15068 some of its internal identifiers, which are normally of no interest to users.
15069 For the rare occasions when you actually have to look at them,
15070 enclose them in angle brackets to avoid the lower-case mapping.
15073 (@value{GDBP}) print <JMPBUF_SAVE>[0]
15077 Printing an object of class-wide type or dereferencing an
15078 access-to-class-wide value will display all the components of the object's
15079 specific type (as indicated by its run-time tag). Likewise, component
15080 selection on such a value will operate on the specific type of the
15085 @node Stopping Before Main Program
15086 @subsubsection Stopping at the Very Beginning
15088 @cindex breakpointing Ada elaboration code
15089 It is sometimes necessary to debug the program during elaboration, and
15090 before reaching the main procedure.
15091 As defined in the Ada Reference
15092 Manual, the elaboration code is invoked from a procedure called
15093 @code{adainit}. To run your program up to the beginning of
15094 elaboration, simply use the following two commands:
15095 @code{tbreak adainit} and @code{run}.
15098 @subsubsection Extensions for Ada Tasks
15099 @cindex Ada, tasking
15101 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
15102 @value{GDBN} provides the following task-related commands:
15107 This command shows a list of current Ada tasks, as in the following example:
15114 (@value{GDBP}) info tasks
15115 ID TID P-ID Pri State Name
15116 1 8088000 0 15 Child Activation Wait main_task
15117 2 80a4000 1 15 Accept Statement b
15118 3 809a800 1 15 Child Activation Wait a
15119 * 4 80ae800 3 15 Runnable c
15124 In this listing, the asterisk before the last task indicates it to be the
15125 task currently being inspected.
15129 Represents @value{GDBN}'s internal task number.
15135 The parent's task ID (@value{GDBN}'s internal task number).
15138 The base priority of the task.
15141 Current state of the task.
15145 The task has been created but has not been activated. It cannot be
15149 The task is not blocked for any reason known to Ada. (It may be waiting
15150 for a mutex, though.) It is conceptually "executing" in normal mode.
15153 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
15154 that were waiting on terminate alternatives have been awakened and have
15155 terminated themselves.
15157 @item Child Activation Wait
15158 The task is waiting for created tasks to complete activation.
15160 @item Accept Statement
15161 The task is waiting on an accept or selective wait statement.
15163 @item Waiting on entry call
15164 The task is waiting on an entry call.
15166 @item Async Select Wait
15167 The task is waiting to start the abortable part of an asynchronous
15171 The task is waiting on a select statement with only a delay
15174 @item Child Termination Wait
15175 The task is sleeping having completed a master within itself, and is
15176 waiting for the tasks dependent on that master to become terminated or
15177 waiting on a terminate Phase.
15179 @item Wait Child in Term Alt
15180 The task is sleeping waiting for tasks on terminate alternatives to
15181 finish terminating.
15183 @item Accepting RV with @var{taskno}
15184 The task is accepting a rendez-vous with the task @var{taskno}.
15188 Name of the task in the program.
15192 @kindex info task @var{taskno}
15193 @item info task @var{taskno}
15194 This command shows detailled informations on the specified task, as in
15195 the following example:
15200 (@value{GDBP}) info tasks
15201 ID TID P-ID Pri State Name
15202 1 8077880 0 15 Child Activation Wait main_task
15203 * 2 807c468 1 15 Runnable task_1
15204 (@value{GDBP}) info task 2
15205 Ada Task: 0x807c468
15208 Parent: 1 (main_task)
15214 @kindex task@r{ (Ada)}
15215 @cindex current Ada task ID
15216 This command prints the ID of the current task.
15222 (@value{GDBP}) info tasks
15223 ID TID P-ID Pri State Name
15224 1 8077870 0 15 Child Activation Wait main_task
15225 * 2 807c458 1 15 Runnable t
15226 (@value{GDBP}) task
15227 [Current task is 2]
15230 @item task @var{taskno}
15231 @cindex Ada task switching
15232 This command is like the @code{thread @var{threadno}}
15233 command (@pxref{Threads}). It switches the context of debugging
15234 from the current task to the given task.
15240 (@value{GDBP}) info tasks
15241 ID TID P-ID Pri State Name
15242 1 8077870 0 15 Child Activation Wait main_task
15243 * 2 807c458 1 15 Runnable t
15244 (@value{GDBP}) task 1
15245 [Switching to task 1]
15246 #0 0x8067726 in pthread_cond_wait ()
15248 #0 0x8067726 in pthread_cond_wait ()
15249 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
15250 #2 0x805cb63 in system.task_primitives.operations.sleep ()
15251 #3 0x806153e in system.tasking.stages.activate_tasks ()
15252 #4 0x804aacc in un () at un.adb:5
15255 @item break @var{linespec} task @var{taskno}
15256 @itemx break @var{linespec} task @var{taskno} if @dots{}
15257 @cindex breakpoints and tasks, in Ada
15258 @cindex task breakpoints, in Ada
15259 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
15260 These commands are like the @code{break @dots{} thread @dots{}}
15261 command (@pxref{Thread Stops}).
15262 @var{linespec} specifies source lines, as described
15263 in @ref{Specify Location}.
15265 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
15266 to specify that you only want @value{GDBN} to stop the program when a
15267 particular Ada task reaches this breakpoint. @var{taskno} is one of the
15268 numeric task identifiers assigned by @value{GDBN}, shown in the first
15269 column of the @samp{info tasks} display.
15271 If you do not specify @samp{task @var{taskno}} when you set a
15272 breakpoint, the breakpoint applies to @emph{all} tasks of your
15275 You can use the @code{task} qualifier on conditional breakpoints as
15276 well; in this case, place @samp{task @var{taskno}} before the
15277 breakpoint condition (before the @code{if}).
15285 (@value{GDBP}) info tasks
15286 ID TID P-ID Pri State Name
15287 1 140022020 0 15 Child Activation Wait main_task
15288 2 140045060 1 15 Accept/Select Wait t2
15289 3 140044840 1 15 Runnable t1
15290 * 4 140056040 1 15 Runnable t3
15291 (@value{GDBP}) b 15 task 2
15292 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15293 (@value{GDBP}) cont
15298 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15300 (@value{GDBP}) info tasks
15301 ID TID P-ID Pri State Name
15302 1 140022020 0 15 Child Activation Wait main_task
15303 * 2 140045060 1 15 Runnable t2
15304 3 140044840 1 15 Runnable t1
15305 4 140056040 1 15 Delay Sleep t3
15309 @node Ada Tasks and Core Files
15310 @subsubsection Tasking Support when Debugging Core Files
15311 @cindex Ada tasking and core file debugging
15313 When inspecting a core file, as opposed to debugging a live program,
15314 tasking support may be limited or even unavailable, depending on
15315 the platform being used.
15316 For instance, on x86-linux, the list of tasks is available, but task
15317 switching is not supported. On Tru64, however, task switching will work
15320 On certain platforms, including Tru64, the debugger needs to perform some
15321 memory writes in order to provide Ada tasking support. When inspecting
15322 a core file, this means that the core file must be opened with read-write
15323 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15324 Under these circumstances, you should make a backup copy of the core
15325 file before inspecting it with @value{GDBN}.
15327 @node Ravenscar Profile
15328 @subsubsection Tasking Support when using the Ravenscar Profile
15329 @cindex Ravenscar Profile
15331 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15332 specifically designed for systems with safety-critical real-time
15336 @kindex set ravenscar task-switching on
15337 @cindex task switching with program using Ravenscar Profile
15338 @item set ravenscar task-switching on
15339 Allows task switching when debugging a program that uses the Ravenscar
15340 Profile. This is the default.
15342 @kindex set ravenscar task-switching off
15343 @item set ravenscar task-switching off
15344 Turn off task switching when debugging a program that uses the Ravenscar
15345 Profile. This is mostly intended to disable the code that adds support
15346 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15347 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15348 To be effective, this command should be run before the program is started.
15350 @kindex show ravenscar task-switching
15351 @item show ravenscar task-switching
15352 Show whether it is possible to switch from task to task in a program
15353 using the Ravenscar Profile.
15358 @subsubsection Known Peculiarities of Ada Mode
15359 @cindex Ada, problems
15361 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15362 we know of several problems with and limitations of Ada mode in
15364 some of which will be fixed with planned future releases of the debugger
15365 and the GNU Ada compiler.
15369 Static constants that the compiler chooses not to materialize as objects in
15370 storage are invisible to the debugger.
15373 Named parameter associations in function argument lists are ignored (the
15374 argument lists are treated as positional).
15377 Many useful library packages are currently invisible to the debugger.
15380 Fixed-point arithmetic, conversions, input, and output is carried out using
15381 floating-point arithmetic, and may give results that only approximate those on
15385 The GNAT compiler never generates the prefix @code{Standard} for any of
15386 the standard symbols defined by the Ada language. @value{GDBN} knows about
15387 this: it will strip the prefix from names when you use it, and will never
15388 look for a name you have so qualified among local symbols, nor match against
15389 symbols in other packages or subprograms. If you have
15390 defined entities anywhere in your program other than parameters and
15391 local variables whose simple names match names in @code{Standard},
15392 GNAT's lack of qualification here can cause confusion. When this happens,
15393 you can usually resolve the confusion
15394 by qualifying the problematic names with package
15395 @code{Standard} explicitly.
15398 Older versions of the compiler sometimes generate erroneous debugging
15399 information, resulting in the debugger incorrectly printing the value
15400 of affected entities. In some cases, the debugger is able to work
15401 around an issue automatically. In other cases, the debugger is able
15402 to work around the issue, but the work-around has to be specifically
15405 @kindex set ada trust-PAD-over-XVS
15406 @kindex show ada trust-PAD-over-XVS
15409 @item set ada trust-PAD-over-XVS on
15410 Configure GDB to strictly follow the GNAT encoding when computing the
15411 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15412 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15413 a complete description of the encoding used by the GNAT compiler).
15414 This is the default.
15416 @item set ada trust-PAD-over-XVS off
15417 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15418 sometimes prints the wrong value for certain entities, changing @code{ada
15419 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15420 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15421 @code{off}, but this incurs a slight performance penalty, so it is
15422 recommended to leave this setting to @code{on} unless necessary.
15426 @node Unsupported Languages
15427 @section Unsupported Languages
15429 @cindex unsupported languages
15430 @cindex minimal language
15431 In addition to the other fully-supported programming languages,
15432 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15433 It does not represent a real programming language, but provides a set
15434 of capabilities close to what the C or assembly languages provide.
15435 This should allow most simple operations to be performed while debugging
15436 an application that uses a language currently not supported by @value{GDBN}.
15438 If the language is set to @code{auto}, @value{GDBN} will automatically
15439 select this language if the current frame corresponds to an unsupported
15443 @chapter Examining the Symbol Table
15445 The commands described in this chapter allow you to inquire about the
15446 symbols (names of variables, functions and types) defined in your
15447 program. This information is inherent in the text of your program and
15448 does not change as your program executes. @value{GDBN} finds it in your
15449 program's symbol table, in the file indicated when you started @value{GDBN}
15450 (@pxref{File Options, ,Choosing Files}), or by one of the
15451 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15453 @cindex symbol names
15454 @cindex names of symbols
15455 @cindex quoting names
15456 Occasionally, you may need to refer to symbols that contain unusual
15457 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15458 most frequent case is in referring to static variables in other
15459 source files (@pxref{Variables,,Program Variables}). File names
15460 are recorded in object files as debugging symbols, but @value{GDBN} would
15461 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15462 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15463 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15470 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15473 @cindex case-insensitive symbol names
15474 @cindex case sensitivity in symbol names
15475 @kindex set case-sensitive
15476 @item set case-sensitive on
15477 @itemx set case-sensitive off
15478 @itemx set case-sensitive auto
15479 Normally, when @value{GDBN} looks up symbols, it matches their names
15480 with case sensitivity determined by the current source language.
15481 Occasionally, you may wish to control that. The command @code{set
15482 case-sensitive} lets you do that by specifying @code{on} for
15483 case-sensitive matches or @code{off} for case-insensitive ones. If
15484 you specify @code{auto}, case sensitivity is reset to the default
15485 suitable for the source language. The default is case-sensitive
15486 matches for all languages except for Fortran, for which the default is
15487 case-insensitive matches.
15489 @kindex show case-sensitive
15490 @item show case-sensitive
15491 This command shows the current setting of case sensitivity for symbols
15494 @kindex set print type methods
15495 @item set print type methods
15496 @itemx set print type methods on
15497 @itemx set print type methods off
15498 Normally, when @value{GDBN} prints a class, it displays any methods
15499 declared in that class. You can control this behavior either by
15500 passing the appropriate flag to @code{ptype}, or using @command{set
15501 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15502 display the methods; this is the default. Specifying @code{off} will
15503 cause @value{GDBN} to omit the methods.
15505 @kindex show print type methods
15506 @item show print type methods
15507 This command shows the current setting of method display when printing
15510 @kindex set print type typedefs
15511 @item set print type typedefs
15512 @itemx set print type typedefs on
15513 @itemx set print type typedefs off
15515 Normally, when @value{GDBN} prints a class, it displays any typedefs
15516 defined in that class. You can control this behavior either by
15517 passing the appropriate flag to @code{ptype}, or using @command{set
15518 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15519 display the typedef definitions; this is the default. Specifying
15520 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15521 Note that this controls whether the typedef definition itself is
15522 printed, not whether typedef names are substituted when printing other
15525 @kindex show print type typedefs
15526 @item show print type typedefs
15527 This command shows the current setting of typedef display when
15530 @kindex info address
15531 @cindex address of a symbol
15532 @item info address @var{symbol}
15533 Describe where the data for @var{symbol} is stored. For a register
15534 variable, this says which register it is kept in. For a non-register
15535 local variable, this prints the stack-frame offset at which the variable
15538 Note the contrast with @samp{print &@var{symbol}}, which does not work
15539 at all for a register variable, and for a stack local variable prints
15540 the exact address of the current instantiation of the variable.
15542 @kindex info symbol
15543 @cindex symbol from address
15544 @cindex closest symbol and offset for an address
15545 @item info symbol @var{addr}
15546 Print the name of a symbol which is stored at the address @var{addr}.
15547 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15548 nearest symbol and an offset from it:
15551 (@value{GDBP}) info symbol 0x54320
15552 _initialize_vx + 396 in section .text
15556 This is the opposite of the @code{info address} command. You can use
15557 it to find out the name of a variable or a function given its address.
15559 For dynamically linked executables, the name of executable or shared
15560 library containing the symbol is also printed:
15563 (@value{GDBP}) info symbol 0x400225
15564 _start + 5 in section .text of /tmp/a.out
15565 (@value{GDBP}) info symbol 0x2aaaac2811cf
15566 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15570 @item whatis[/@var{flags}] [@var{arg}]
15571 Print the data type of @var{arg}, which can be either an expression
15572 or a name of a data type. With no argument, print the data type of
15573 @code{$}, the last value in the value history.
15575 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15576 is not actually evaluated, and any side-effecting operations (such as
15577 assignments or function calls) inside it do not take place.
15579 If @var{arg} is a variable or an expression, @code{whatis} prints its
15580 literal type as it is used in the source code. If the type was
15581 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15582 the data type underlying the @code{typedef}. If the type of the
15583 variable or the expression is a compound data type, such as
15584 @code{struct} or @code{class}, @code{whatis} never prints their
15585 fields or methods. It just prints the @code{struct}/@code{class}
15586 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15587 such a compound data type, use @code{ptype}.
15589 If @var{arg} is a type name that was defined using @code{typedef},
15590 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15591 Unrolling means that @code{whatis} will show the underlying type used
15592 in the @code{typedef} declaration of @var{arg}. However, if that
15593 underlying type is also a @code{typedef}, @code{whatis} will not
15596 For C code, the type names may also have the form @samp{class
15597 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15598 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15600 @var{flags} can be used to modify how the type is displayed.
15601 Available flags are:
15605 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15606 parameters and typedefs defined in a class when printing the class'
15607 members. The @code{/r} flag disables this.
15610 Do not print methods defined in the class.
15613 Print methods defined in the class. This is the default, but the flag
15614 exists in case you change the default with @command{set print type methods}.
15617 Do not print typedefs defined in the class. Note that this controls
15618 whether the typedef definition itself is printed, not whether typedef
15619 names are substituted when printing other types.
15622 Print typedefs defined in the class. This is the default, but the flag
15623 exists in case you change the default with @command{set print type typedefs}.
15627 @item ptype[/@var{flags}] [@var{arg}]
15628 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15629 detailed description of the type, instead of just the name of the type.
15630 @xref{Expressions, ,Expressions}.
15632 Contrary to @code{whatis}, @code{ptype} always unrolls any
15633 @code{typedef}s in its argument declaration, whether the argument is
15634 a variable, expression, or a data type. This means that @code{ptype}
15635 of a variable or an expression will not print literally its type as
15636 present in the source code---use @code{whatis} for that. @code{typedef}s at
15637 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15638 fields, methods and inner @code{class typedef}s of @code{struct}s,
15639 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15641 For example, for this variable declaration:
15644 typedef double real_t;
15645 struct complex @{ real_t real; double imag; @};
15646 typedef struct complex complex_t;
15648 real_t *real_pointer_var;
15652 the two commands give this output:
15656 (@value{GDBP}) whatis var
15658 (@value{GDBP}) ptype var
15659 type = struct complex @{
15663 (@value{GDBP}) whatis complex_t
15664 type = struct complex
15665 (@value{GDBP}) whatis struct complex
15666 type = struct complex
15667 (@value{GDBP}) ptype struct complex
15668 type = struct complex @{
15672 (@value{GDBP}) whatis real_pointer_var
15674 (@value{GDBP}) ptype real_pointer_var
15680 As with @code{whatis}, using @code{ptype} without an argument refers to
15681 the type of @code{$}, the last value in the value history.
15683 @cindex incomplete type
15684 Sometimes, programs use opaque data types or incomplete specifications
15685 of complex data structure. If the debug information included in the
15686 program does not allow @value{GDBN} to display a full declaration of
15687 the data type, it will say @samp{<incomplete type>}. For example,
15688 given these declarations:
15692 struct foo *fooptr;
15696 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15699 (@value{GDBP}) ptype foo
15700 $1 = <incomplete type>
15704 ``Incomplete type'' is C terminology for data types that are not
15705 completely specified.
15708 @item info types @var{regexp}
15710 Print a brief description of all types whose names match the regular
15711 expression @var{regexp} (or all types in your program, if you supply
15712 no argument). Each complete typename is matched as though it were a
15713 complete line; thus, @samp{i type value} gives information on all
15714 types in your program whose names include the string @code{value}, but
15715 @samp{i type ^value$} gives information only on types whose complete
15716 name is @code{value}.
15718 This command differs from @code{ptype} in two ways: first, like
15719 @code{whatis}, it does not print a detailed description; second, it
15720 lists all source files where a type is defined.
15722 @kindex info type-printers
15723 @item info type-printers
15724 Versions of @value{GDBN} that ship with Python scripting enabled may
15725 have ``type printers'' available. When using @command{ptype} or
15726 @command{whatis}, these printers are consulted when the name of a type
15727 is needed. @xref{Type Printing API}, for more information on writing
15730 @code{info type-printers} displays all the available type printers.
15732 @kindex enable type-printer
15733 @kindex disable type-printer
15734 @item enable type-printer @var{name}@dots{}
15735 @item disable type-printer @var{name}@dots{}
15736 These commands can be used to enable or disable type printers.
15739 @cindex local variables
15740 @item info scope @var{location}
15741 List all the variables local to a particular scope. This command
15742 accepts a @var{location} argument---a function name, a source line, or
15743 an address preceded by a @samp{*}, and prints all the variables local
15744 to the scope defined by that location. (@xref{Specify Location}, for
15745 details about supported forms of @var{location}.) For example:
15748 (@value{GDBP}) @b{info scope command_line_handler}
15749 Scope for command_line_handler:
15750 Symbol rl is an argument at stack/frame offset 8, length 4.
15751 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15752 Symbol linelength is in static storage at address 0x150a1c, length 4.
15753 Symbol p is a local variable in register $esi, length 4.
15754 Symbol p1 is a local variable in register $ebx, length 4.
15755 Symbol nline is a local variable in register $edx, length 4.
15756 Symbol repeat is a local variable at frame offset -8, length 4.
15760 This command is especially useful for determining what data to collect
15761 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15764 @kindex info source
15766 Show information about the current source file---that is, the source file for
15767 the function containing the current point of execution:
15770 the name of the source file, and the directory containing it,
15772 the directory it was compiled in,
15774 its length, in lines,
15776 which programming language it is written in,
15778 whether the executable includes debugging information for that file, and
15779 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15781 whether the debugging information includes information about
15782 preprocessor macros.
15786 @kindex info sources
15788 Print the names of all source files in your program for which there is
15789 debugging information, organized into two lists: files whose symbols
15790 have already been read, and files whose symbols will be read when needed.
15792 @kindex info functions
15793 @item info functions
15794 Print the names and data types of all defined functions.
15796 @item info functions @var{regexp}
15797 Print the names and data types of all defined functions
15798 whose names contain a match for regular expression @var{regexp}.
15799 Thus, @samp{info fun step} finds all functions whose names
15800 include @code{step}; @samp{info fun ^step} finds those whose names
15801 start with @code{step}. If a function name contains characters
15802 that conflict with the regular expression language (e.g.@:
15803 @samp{operator*()}), they may be quoted with a backslash.
15805 @kindex info variables
15806 @item info variables
15807 Print the names and data types of all variables that are defined
15808 outside of functions (i.e.@: excluding local variables).
15810 @item info variables @var{regexp}
15811 Print the names and data types of all variables (except for local
15812 variables) whose names contain a match for regular expression
15815 @kindex info classes
15816 @cindex Objective-C, classes and selectors
15818 @itemx info classes @var{regexp}
15819 Display all Objective-C classes in your program, or
15820 (with the @var{regexp} argument) all those matching a particular regular
15823 @kindex info selectors
15824 @item info selectors
15825 @itemx info selectors @var{regexp}
15826 Display all Objective-C selectors in your program, or
15827 (with the @var{regexp} argument) all those matching a particular regular
15831 This was never implemented.
15832 @kindex info methods
15834 @itemx info methods @var{regexp}
15835 The @code{info methods} command permits the user to examine all defined
15836 methods within C@t{++} program, or (with the @var{regexp} argument) a
15837 specific set of methods found in the various C@t{++} classes. Many
15838 C@t{++} classes provide a large number of methods. Thus, the output
15839 from the @code{ptype} command can be overwhelming and hard to use. The
15840 @code{info-methods} command filters the methods, printing only those
15841 which match the regular-expression @var{regexp}.
15844 @cindex opaque data types
15845 @kindex set opaque-type-resolution
15846 @item set opaque-type-resolution on
15847 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15848 declared as a pointer to a @code{struct}, @code{class}, or
15849 @code{union}---for example, @code{struct MyType *}---that is used in one
15850 source file although the full declaration of @code{struct MyType} is in
15851 another source file. The default is on.
15853 A change in the setting of this subcommand will not take effect until
15854 the next time symbols for a file are loaded.
15856 @item set opaque-type-resolution off
15857 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15858 is printed as follows:
15860 @{<no data fields>@}
15863 @kindex show opaque-type-resolution
15864 @item show opaque-type-resolution
15865 Show whether opaque types are resolved or not.
15867 @kindex maint print symbols
15868 @cindex symbol dump
15869 @kindex maint print psymbols
15870 @cindex partial symbol dump
15871 @kindex maint print msymbols
15872 @cindex minimal symbol dump
15873 @item maint print symbols @var{filename}
15874 @itemx maint print psymbols @var{filename}
15875 @itemx maint print msymbols @var{filename}
15876 Write a dump of debugging symbol data into the file @var{filename}.
15877 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15878 symbols with debugging data are included. If you use @samp{maint print
15879 symbols}, @value{GDBN} includes all the symbols for which it has already
15880 collected full details: that is, @var{filename} reflects symbols for
15881 only those files whose symbols @value{GDBN} has read. You can use the
15882 command @code{info sources} to find out which files these are. If you
15883 use @samp{maint print psymbols} instead, the dump shows information about
15884 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15885 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15886 @samp{maint print msymbols} dumps just the minimal symbol information
15887 required for each object file from which @value{GDBN} has read some symbols.
15888 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15889 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15891 @kindex maint info symtabs
15892 @kindex maint info psymtabs
15893 @cindex listing @value{GDBN}'s internal symbol tables
15894 @cindex symbol tables, listing @value{GDBN}'s internal
15895 @cindex full symbol tables, listing @value{GDBN}'s internal
15896 @cindex partial symbol tables, listing @value{GDBN}'s internal
15897 @item maint info symtabs @r{[} @var{regexp} @r{]}
15898 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15900 List the @code{struct symtab} or @code{struct partial_symtab}
15901 structures whose names match @var{regexp}. If @var{regexp} is not
15902 given, list them all. The output includes expressions which you can
15903 copy into a @value{GDBN} debugging this one to examine a particular
15904 structure in more detail. For example:
15907 (@value{GDBP}) maint info psymtabs dwarf2read
15908 @{ objfile /home/gnu/build/gdb/gdb
15909 ((struct objfile *) 0x82e69d0)
15910 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15911 ((struct partial_symtab *) 0x8474b10)
15914 text addresses 0x814d3c8 -- 0x8158074
15915 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15916 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15917 dependencies (none)
15920 (@value{GDBP}) maint info symtabs
15924 We see that there is one partial symbol table whose filename contains
15925 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15926 and we see that @value{GDBN} has not read in any symtabs yet at all.
15927 If we set a breakpoint on a function, that will cause @value{GDBN} to
15928 read the symtab for the compilation unit containing that function:
15931 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15932 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15934 (@value{GDBP}) maint info symtabs
15935 @{ objfile /home/gnu/build/gdb/gdb
15936 ((struct objfile *) 0x82e69d0)
15937 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15938 ((struct symtab *) 0x86c1f38)
15941 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15942 linetable ((struct linetable *) 0x8370fa0)
15943 debugformat DWARF 2
15952 @chapter Altering Execution
15954 Once you think you have found an error in your program, you might want to
15955 find out for certain whether correcting the apparent error would lead to
15956 correct results in the rest of the run. You can find the answer by
15957 experiment, using the @value{GDBN} features for altering execution of the
15960 For example, you can store new values into variables or memory
15961 locations, give your program a signal, restart it at a different
15962 address, or even return prematurely from a function.
15965 * Assignment:: Assignment to variables
15966 * Jumping:: Continuing at a different address
15967 * Signaling:: Giving your program a signal
15968 * Returning:: Returning from a function
15969 * Calling:: Calling your program's functions
15970 * Patching:: Patching your program
15974 @section Assignment to Variables
15977 @cindex setting variables
15978 To alter the value of a variable, evaluate an assignment expression.
15979 @xref{Expressions, ,Expressions}. For example,
15986 stores the value 4 into the variable @code{x}, and then prints the
15987 value of the assignment expression (which is 4).
15988 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15989 information on operators in supported languages.
15991 @kindex set variable
15992 @cindex variables, setting
15993 If you are not interested in seeing the value of the assignment, use the
15994 @code{set} command instead of the @code{print} command. @code{set} is
15995 really the same as @code{print} except that the expression's value is
15996 not printed and is not put in the value history (@pxref{Value History,
15997 ,Value History}). The expression is evaluated only for its effects.
15999 If the beginning of the argument string of the @code{set} command
16000 appears identical to a @code{set} subcommand, use the @code{set
16001 variable} command instead of just @code{set}. This command is identical
16002 to @code{set} except for its lack of subcommands. For example, if your
16003 program has a variable @code{width}, you get an error if you try to set
16004 a new value with just @samp{set width=13}, because @value{GDBN} has the
16005 command @code{set width}:
16008 (@value{GDBP}) whatis width
16010 (@value{GDBP}) p width
16012 (@value{GDBP}) set width=47
16013 Invalid syntax in expression.
16017 The invalid expression, of course, is @samp{=47}. In
16018 order to actually set the program's variable @code{width}, use
16021 (@value{GDBP}) set var width=47
16024 Because the @code{set} command has many subcommands that can conflict
16025 with the names of program variables, it is a good idea to use the
16026 @code{set variable} command instead of just @code{set}. For example, if
16027 your program has a variable @code{g}, you run into problems if you try
16028 to set a new value with just @samp{set g=4}, because @value{GDBN} has
16029 the command @code{set gnutarget}, abbreviated @code{set g}:
16033 (@value{GDBP}) whatis g
16037 (@value{GDBP}) set g=4
16041 The program being debugged has been started already.
16042 Start it from the beginning? (y or n) y
16043 Starting program: /home/smith/cc_progs/a.out
16044 "/home/smith/cc_progs/a.out": can't open to read symbols:
16045 Invalid bfd target.
16046 (@value{GDBP}) show g
16047 The current BFD target is "=4".
16052 The program variable @code{g} did not change, and you silently set the
16053 @code{gnutarget} to an invalid value. In order to set the variable
16057 (@value{GDBP}) set var g=4
16060 @value{GDBN} allows more implicit conversions in assignments than C; you can
16061 freely store an integer value into a pointer variable or vice versa,
16062 and you can convert any structure to any other structure that is the
16063 same length or shorter.
16064 @comment FIXME: how do structs align/pad in these conversions?
16065 @comment /doc@cygnus.com 18dec1990
16067 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
16068 construct to generate a value of specified type at a specified address
16069 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
16070 to memory location @code{0x83040} as an integer (which implies a certain size
16071 and representation in memory), and
16074 set @{int@}0x83040 = 4
16078 stores the value 4 into that memory location.
16081 @section Continuing at a Different Address
16083 Ordinarily, when you continue your program, you do so at the place where
16084 it stopped, with the @code{continue} command. You can instead continue at
16085 an address of your own choosing, with the following commands:
16089 @kindex j @r{(@code{jump})}
16090 @item jump @var{linespec}
16091 @itemx j @var{linespec}
16092 @itemx jump @var{location}
16093 @itemx j @var{location}
16094 Resume execution at line @var{linespec} or at address given by
16095 @var{location}. Execution stops again immediately if there is a
16096 breakpoint there. @xref{Specify Location}, for a description of the
16097 different forms of @var{linespec} and @var{location}. It is common
16098 practice to use the @code{tbreak} command in conjunction with
16099 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
16101 The @code{jump} command does not change the current stack frame, or
16102 the stack pointer, or the contents of any memory location or any
16103 register other than the program counter. If line @var{linespec} is in
16104 a different function from the one currently executing, the results may
16105 be bizarre if the two functions expect different patterns of arguments or
16106 of local variables. For this reason, the @code{jump} command requests
16107 confirmation if the specified line is not in the function currently
16108 executing. However, even bizarre results are predictable if you are
16109 well acquainted with the machine-language code of your program.
16112 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
16113 On many systems, you can get much the same effect as the @code{jump}
16114 command by storing a new value into the register @code{$pc}. The
16115 difference is that this does not start your program running; it only
16116 changes the address of where it @emph{will} run when you continue. For
16124 makes the next @code{continue} command or stepping command execute at
16125 address @code{0x485}, rather than at the address where your program stopped.
16126 @xref{Continuing and Stepping, ,Continuing and Stepping}.
16128 The most common occasion to use the @code{jump} command is to back
16129 up---perhaps with more breakpoints set---over a portion of a program
16130 that has already executed, in order to examine its execution in more
16135 @section Giving your Program a Signal
16136 @cindex deliver a signal to a program
16140 @item signal @var{signal}
16141 Resume execution where your program stopped, but immediately give it the
16142 signal @var{signal}. @var{signal} can be the name or the number of a
16143 signal. For example, on many systems @code{signal 2} and @code{signal
16144 SIGINT} are both ways of sending an interrupt signal.
16146 Alternatively, if @var{signal} is zero, continue execution without
16147 giving a signal. This is useful when your program stopped on account of
16148 a signal and would ordinarily see the signal when resumed with the
16149 @code{continue} command; @samp{signal 0} causes it to resume without a
16152 @code{signal} does not repeat when you press @key{RET} a second time
16153 after executing the command.
16157 Invoking the @code{signal} command is not the same as invoking the
16158 @code{kill} utility from the shell. Sending a signal with @code{kill}
16159 causes @value{GDBN} to decide what to do with the signal depending on
16160 the signal handling tables (@pxref{Signals}). The @code{signal} command
16161 passes the signal directly to your program.
16165 @section Returning from a Function
16168 @cindex returning from a function
16171 @itemx return @var{expression}
16172 You can cancel execution of a function call with the @code{return}
16173 command. If you give an
16174 @var{expression} argument, its value is used as the function's return
16178 When you use @code{return}, @value{GDBN} discards the selected stack frame
16179 (and all frames within it). You can think of this as making the
16180 discarded frame return prematurely. If you wish to specify a value to
16181 be returned, give that value as the argument to @code{return}.
16183 This pops the selected stack frame (@pxref{Selection, ,Selecting a
16184 Frame}), and any other frames inside of it, leaving its caller as the
16185 innermost remaining frame. That frame becomes selected. The
16186 specified value is stored in the registers used for returning values
16189 The @code{return} command does not resume execution; it leaves the
16190 program stopped in the state that would exist if the function had just
16191 returned. In contrast, the @code{finish} command (@pxref{Continuing
16192 and Stepping, ,Continuing and Stepping}) resumes execution until the
16193 selected stack frame returns naturally.
16195 @value{GDBN} needs to know how the @var{expression} argument should be set for
16196 the inferior. The concrete registers assignment depends on the OS ABI and the
16197 type being returned by the selected stack frame. For example it is common for
16198 OS ABI to return floating point values in FPU registers while integer values in
16199 CPU registers. Still some ABIs return even floating point values in CPU
16200 registers. Larger integer widths (such as @code{long long int}) also have
16201 specific placement rules. @value{GDBN} already knows the OS ABI from its
16202 current target so it needs to find out also the type being returned to make the
16203 assignment into the right register(s).
16205 Normally, the selected stack frame has debug info. @value{GDBN} will always
16206 use the debug info instead of the implicit type of @var{expression} when the
16207 debug info is available. For example, if you type @kbd{return -1}, and the
16208 function in the current stack frame is declared to return a @code{long long
16209 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
16210 into a @code{long long int}:
16213 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
16215 (@value{GDBP}) return -1
16216 Make func return now? (y or n) y
16217 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
16218 43 printf ("result=%lld\n", func ());
16222 However, if the selected stack frame does not have a debug info, e.g., if the
16223 function was compiled without debug info, @value{GDBN} has to find out the type
16224 to return from user. Specifying a different type by mistake may set the value
16225 in different inferior registers than the caller code expects. For example,
16226 typing @kbd{return -1} with its implicit type @code{int} would set only a part
16227 of a @code{long long int} result for a debug info less function (on 32-bit
16228 architectures). Therefore the user is required to specify the return type by
16229 an appropriate cast explicitly:
16232 Breakpoint 2, 0x0040050b in func ()
16233 (@value{GDBP}) return -1
16234 Return value type not available for selected stack frame.
16235 Please use an explicit cast of the value to return.
16236 (@value{GDBP}) return (long long int) -1
16237 Make selected stack frame return now? (y or n) y
16238 #0 0x00400526 in main ()
16243 @section Calling Program Functions
16246 @cindex calling functions
16247 @cindex inferior functions, calling
16248 @item print @var{expr}
16249 Evaluate the expression @var{expr} and display the resulting value.
16250 @var{expr} may include calls to functions in the program being
16254 @item call @var{expr}
16255 Evaluate the expression @var{expr} without displaying @code{void}
16258 You can use this variant of the @code{print} command if you want to
16259 execute a function from your program that does not return anything
16260 (a.k.a.@: @dfn{a void function}), but without cluttering the output
16261 with @code{void} returned values that @value{GDBN} will otherwise
16262 print. If the result is not void, it is printed and saved in the
16266 It is possible for the function you call via the @code{print} or
16267 @code{call} command to generate a signal (e.g., if there's a bug in
16268 the function, or if you passed it incorrect arguments). What happens
16269 in that case is controlled by the @code{set unwindonsignal} command.
16271 Similarly, with a C@t{++} program it is possible for the function you
16272 call via the @code{print} or @code{call} command to generate an
16273 exception that is not handled due to the constraints of the dummy
16274 frame. In this case, any exception that is raised in the frame, but has
16275 an out-of-frame exception handler will not be found. GDB builds a
16276 dummy-frame for the inferior function call, and the unwinder cannot
16277 seek for exception handlers outside of this dummy-frame. What happens
16278 in that case is controlled by the
16279 @code{set unwind-on-terminating-exception} command.
16282 @item set unwindonsignal
16283 @kindex set unwindonsignal
16284 @cindex unwind stack in called functions
16285 @cindex call dummy stack unwinding
16286 Set unwinding of the stack if a signal is received while in a function
16287 that @value{GDBN} called in the program being debugged. If set to on,
16288 @value{GDBN} unwinds the stack it created for the call and restores
16289 the context to what it was before the call. If set to off (the
16290 default), @value{GDBN} stops in the frame where the signal was
16293 @item show unwindonsignal
16294 @kindex show unwindonsignal
16295 Show the current setting of stack unwinding in the functions called by
16298 @item set unwind-on-terminating-exception
16299 @kindex set unwind-on-terminating-exception
16300 @cindex unwind stack in called functions with unhandled exceptions
16301 @cindex call dummy stack unwinding on unhandled exception.
16302 Set unwinding of the stack if a C@t{++} exception is raised, but left
16303 unhandled while in a function that @value{GDBN} called in the program being
16304 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16305 it created for the call and restores the context to what it was before
16306 the call. If set to off, @value{GDBN} the exception is delivered to
16307 the default C@t{++} exception handler and the inferior terminated.
16309 @item show unwind-on-terminating-exception
16310 @kindex show unwind-on-terminating-exception
16311 Show the current setting of stack unwinding in the functions called by
16316 @cindex weak alias functions
16317 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16318 for another function. In such case, @value{GDBN} might not pick up
16319 the type information, including the types of the function arguments,
16320 which causes @value{GDBN} to call the inferior function incorrectly.
16321 As a result, the called function will function erroneously and may
16322 even crash. A solution to that is to use the name of the aliased
16326 @section Patching Programs
16328 @cindex patching binaries
16329 @cindex writing into executables
16330 @cindex writing into corefiles
16332 By default, @value{GDBN} opens the file containing your program's
16333 executable code (or the corefile) read-only. This prevents accidental
16334 alterations to machine code; but it also prevents you from intentionally
16335 patching your program's binary.
16337 If you'd like to be able to patch the binary, you can specify that
16338 explicitly with the @code{set write} command. For example, you might
16339 want to turn on internal debugging flags, or even to make emergency
16345 @itemx set write off
16346 If you specify @samp{set write on}, @value{GDBN} opens executable and
16347 core files for both reading and writing; if you specify @kbd{set write
16348 off} (the default), @value{GDBN} opens them read-only.
16350 If you have already loaded a file, you must load it again (using the
16351 @code{exec-file} or @code{core-file} command) after changing @code{set
16352 write}, for your new setting to take effect.
16356 Display whether executable files and core files are opened for writing
16357 as well as reading.
16361 @chapter @value{GDBN} Files
16363 @value{GDBN} needs to know the file name of the program to be debugged,
16364 both in order to read its symbol table and in order to start your
16365 program. To debug a core dump of a previous run, you must also tell
16366 @value{GDBN} the name of the core dump file.
16369 * Files:: Commands to specify files
16370 * Separate Debug Files:: Debugging information in separate files
16371 * MiniDebugInfo:: Debugging information in a special section
16372 * Index Files:: Index files speed up GDB
16373 * Symbol Errors:: Errors reading symbol files
16374 * Data Files:: GDB data files
16378 @section Commands to Specify Files
16380 @cindex symbol table
16381 @cindex core dump file
16383 You may want to specify executable and core dump file names. The usual
16384 way to do this is at start-up time, using the arguments to
16385 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16386 Out of @value{GDBN}}).
16388 Occasionally it is necessary to change to a different file during a
16389 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16390 specify a file you want to use. Or you are debugging a remote target
16391 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16392 Program}). In these situations the @value{GDBN} commands to specify
16393 new files are useful.
16396 @cindex executable file
16398 @item file @var{filename}
16399 Use @var{filename} as the program to be debugged. It is read for its
16400 symbols and for the contents of pure memory. It is also the program
16401 executed when you use the @code{run} command. If you do not specify a
16402 directory and the file is not found in the @value{GDBN} working directory,
16403 @value{GDBN} uses the environment variable @code{PATH} as a list of
16404 directories to search, just as the shell does when looking for a program
16405 to run. You can change the value of this variable, for both @value{GDBN}
16406 and your program, using the @code{path} command.
16408 @cindex unlinked object files
16409 @cindex patching object files
16410 You can load unlinked object @file{.o} files into @value{GDBN} using
16411 the @code{file} command. You will not be able to ``run'' an object
16412 file, but you can disassemble functions and inspect variables. Also,
16413 if the underlying BFD functionality supports it, you could use
16414 @kbd{gdb -write} to patch object files using this technique. Note
16415 that @value{GDBN} can neither interpret nor modify relocations in this
16416 case, so branches and some initialized variables will appear to go to
16417 the wrong place. But this feature is still handy from time to time.
16420 @code{file} with no argument makes @value{GDBN} discard any information it
16421 has on both executable file and the symbol table.
16424 @item exec-file @r{[} @var{filename} @r{]}
16425 Specify that the program to be run (but not the symbol table) is found
16426 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16427 if necessary to locate your program. Omitting @var{filename} means to
16428 discard information on the executable file.
16430 @kindex symbol-file
16431 @item symbol-file @r{[} @var{filename} @r{]}
16432 Read symbol table information from file @var{filename}. @code{PATH} is
16433 searched when necessary. Use the @code{file} command to get both symbol
16434 table and program to run from the same file.
16436 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16437 program's symbol table.
16439 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16440 some breakpoints and auto-display expressions. This is because they may
16441 contain pointers to the internal data recording symbols and data types,
16442 which are part of the old symbol table data being discarded inside
16445 @code{symbol-file} does not repeat if you press @key{RET} again after
16448 When @value{GDBN} is configured for a particular environment, it
16449 understands debugging information in whatever format is the standard
16450 generated for that environment; you may use either a @sc{gnu} compiler, or
16451 other compilers that adhere to the local conventions.
16452 Best results are usually obtained from @sc{gnu} compilers; for example,
16453 using @code{@value{NGCC}} you can generate debugging information for
16456 For most kinds of object files, with the exception of old SVR3 systems
16457 using COFF, the @code{symbol-file} command does not normally read the
16458 symbol table in full right away. Instead, it scans the symbol table
16459 quickly to find which source files and which symbols are present. The
16460 details are read later, one source file at a time, as they are needed.
16462 The purpose of this two-stage reading strategy is to make @value{GDBN}
16463 start up faster. For the most part, it is invisible except for
16464 occasional pauses while the symbol table details for a particular source
16465 file are being read. (The @code{set verbose} command can turn these
16466 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16467 Warnings and Messages}.)
16469 We have not implemented the two-stage strategy for COFF yet. When the
16470 symbol table is stored in COFF format, @code{symbol-file} reads the
16471 symbol table data in full right away. Note that ``stabs-in-COFF''
16472 still does the two-stage strategy, since the debug info is actually
16476 @cindex reading symbols immediately
16477 @cindex symbols, reading immediately
16478 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16479 @itemx file @r{[} -readnow @r{]} @var{filename}
16480 You can override the @value{GDBN} two-stage strategy for reading symbol
16481 tables by using the @samp{-readnow} option with any of the commands that
16482 load symbol table information, if you want to be sure @value{GDBN} has the
16483 entire symbol table available.
16485 @c FIXME: for now no mention of directories, since this seems to be in
16486 @c flux. 13mar1992 status is that in theory GDB would look either in
16487 @c current dir or in same dir as myprog; but issues like competing
16488 @c GDB's, or clutter in system dirs, mean that in practice right now
16489 @c only current dir is used. FFish says maybe a special GDB hierarchy
16490 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16494 @item core-file @r{[}@var{filename}@r{]}
16496 Specify the whereabouts of a core dump file to be used as the ``contents
16497 of memory''. Traditionally, core files contain only some parts of the
16498 address space of the process that generated them; @value{GDBN} can access the
16499 executable file itself for other parts.
16501 @code{core-file} with no argument specifies that no core file is
16504 Note that the core file is ignored when your program is actually running
16505 under @value{GDBN}. So, if you have been running your program and you
16506 wish to debug a core file instead, you must kill the subprocess in which
16507 the program is running. To do this, use the @code{kill} command
16508 (@pxref{Kill Process, ,Killing the Child Process}).
16510 @kindex add-symbol-file
16511 @cindex dynamic linking
16512 @item add-symbol-file @var{filename} @var{address}
16513 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16514 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16515 The @code{add-symbol-file} command reads additional symbol table
16516 information from the file @var{filename}. You would use this command
16517 when @var{filename} has been dynamically loaded (by some other means)
16518 into the program that is running. @var{address} should be the memory
16519 address at which the file has been loaded; @value{GDBN} cannot figure
16520 this out for itself. You can additionally specify an arbitrary number
16521 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16522 section name and base address for that section. You can specify any
16523 @var{address} as an expression.
16525 The symbol table of the file @var{filename} is added to the symbol table
16526 originally read with the @code{symbol-file} command. You can use the
16527 @code{add-symbol-file} command any number of times; the new symbol data
16528 thus read keeps adding to the old. To discard all old symbol data
16529 instead, use the @code{symbol-file} command without any arguments.
16531 @cindex relocatable object files, reading symbols from
16532 @cindex object files, relocatable, reading symbols from
16533 @cindex reading symbols from relocatable object files
16534 @cindex symbols, reading from relocatable object files
16535 @cindex @file{.o} files, reading symbols from
16536 Although @var{filename} is typically a shared library file, an
16537 executable file, or some other object file which has been fully
16538 relocated for loading into a process, you can also load symbolic
16539 information from relocatable @file{.o} files, as long as:
16543 the file's symbolic information refers only to linker symbols defined in
16544 that file, not to symbols defined by other object files,
16546 every section the file's symbolic information refers to has actually
16547 been loaded into the inferior, as it appears in the file, and
16549 you can determine the address at which every section was loaded, and
16550 provide these to the @code{add-symbol-file} command.
16554 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16555 relocatable files into an already running program; such systems
16556 typically make the requirements above easy to meet. However, it's
16557 important to recognize that many native systems use complex link
16558 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16559 assembly, for example) that make the requirements difficult to meet. In
16560 general, one cannot assume that using @code{add-symbol-file} to read a
16561 relocatable object file's symbolic information will have the same effect
16562 as linking the relocatable object file into the program in the normal
16565 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16567 @kindex add-symbol-file-from-memory
16568 @cindex @code{syscall DSO}
16569 @cindex load symbols from memory
16570 @item add-symbol-file-from-memory @var{address}
16571 Load symbols from the given @var{address} in a dynamically loaded
16572 object file whose image is mapped directly into the inferior's memory.
16573 For example, the Linux kernel maps a @code{syscall DSO} into each
16574 process's address space; this DSO provides kernel-specific code for
16575 some system calls. The argument can be any expression whose
16576 evaluation yields the address of the file's shared object file header.
16577 For this command to work, you must have used @code{symbol-file} or
16578 @code{exec-file} commands in advance.
16580 @kindex add-shared-symbol-files
16582 @item add-shared-symbol-files @var{library-file}
16583 @itemx assf @var{library-file}
16584 The @code{add-shared-symbol-files} command can currently be used only
16585 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16586 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16587 @value{GDBN} automatically looks for shared libraries, however if
16588 @value{GDBN} does not find yours, you can invoke
16589 @code{add-shared-symbol-files}. It takes one argument: the shared
16590 library's file name. @code{assf} is a shorthand alias for
16591 @code{add-shared-symbol-files}.
16594 @item section @var{section} @var{addr}
16595 The @code{section} command changes the base address of the named
16596 @var{section} of the exec file to @var{addr}. This can be used if the
16597 exec file does not contain section addresses, (such as in the
16598 @code{a.out} format), or when the addresses specified in the file
16599 itself are wrong. Each section must be changed separately. The
16600 @code{info files} command, described below, lists all the sections and
16604 @kindex info target
16607 @code{info files} and @code{info target} are synonymous; both print the
16608 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16609 including the names of the executable and core dump files currently in
16610 use by @value{GDBN}, and the files from which symbols were loaded. The
16611 command @code{help target} lists all possible targets rather than
16614 @kindex maint info sections
16615 @item maint info sections
16616 Another command that can give you extra information about program sections
16617 is @code{maint info sections}. In addition to the section information
16618 displayed by @code{info files}, this command displays the flags and file
16619 offset of each section in the executable and core dump files. In addition,
16620 @code{maint info sections} provides the following command options (which
16621 may be arbitrarily combined):
16625 Display sections for all loaded object files, including shared libraries.
16626 @item @var{sections}
16627 Display info only for named @var{sections}.
16628 @item @var{section-flags}
16629 Display info only for sections for which @var{section-flags} are true.
16630 The section flags that @value{GDBN} currently knows about are:
16633 Section will have space allocated in the process when loaded.
16634 Set for all sections except those containing debug information.
16636 Section will be loaded from the file into the child process memory.
16637 Set for pre-initialized code and data, clear for @code{.bss} sections.
16639 Section needs to be relocated before loading.
16641 Section cannot be modified by the child process.
16643 Section contains executable code only.
16645 Section contains data only (no executable code).
16647 Section will reside in ROM.
16649 Section contains data for constructor/destructor lists.
16651 Section is not empty.
16653 An instruction to the linker to not output the section.
16654 @item COFF_SHARED_LIBRARY
16655 A notification to the linker that the section contains
16656 COFF shared library information.
16658 Section contains common symbols.
16661 @kindex set trust-readonly-sections
16662 @cindex read-only sections
16663 @item set trust-readonly-sections on
16664 Tell @value{GDBN} that readonly sections in your object file
16665 really are read-only (i.e.@: that their contents will not change).
16666 In that case, @value{GDBN} can fetch values from these sections
16667 out of the object file, rather than from the target program.
16668 For some targets (notably embedded ones), this can be a significant
16669 enhancement to debugging performance.
16671 The default is off.
16673 @item set trust-readonly-sections off
16674 Tell @value{GDBN} not to trust readonly sections. This means that
16675 the contents of the section might change while the program is running,
16676 and must therefore be fetched from the target when needed.
16678 @item show trust-readonly-sections
16679 Show the current setting of trusting readonly sections.
16682 All file-specifying commands allow both absolute and relative file names
16683 as arguments. @value{GDBN} always converts the file name to an absolute file
16684 name and remembers it that way.
16686 @cindex shared libraries
16687 @anchor{Shared Libraries}
16688 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16689 and IBM RS/6000 AIX shared libraries.
16691 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16692 shared libraries. @xref{Expat}.
16694 @value{GDBN} automatically loads symbol definitions from shared libraries
16695 when you use the @code{run} command, or when you examine a core file.
16696 (Before you issue the @code{run} command, @value{GDBN} does not understand
16697 references to a function in a shared library, however---unless you are
16698 debugging a core file).
16700 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16701 automatically loads the symbols at the time of the @code{shl_load} call.
16703 @c FIXME: some @value{GDBN} release may permit some refs to undef
16704 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16705 @c FIXME...lib; check this from time to time when updating manual
16707 There are times, however, when you may wish to not automatically load
16708 symbol definitions from shared libraries, such as when they are
16709 particularly large or there are many of them.
16711 To control the automatic loading of shared library symbols, use the
16715 @kindex set auto-solib-add
16716 @item set auto-solib-add @var{mode}
16717 If @var{mode} is @code{on}, symbols from all shared object libraries
16718 will be loaded automatically when the inferior begins execution, you
16719 attach to an independently started inferior, or when the dynamic linker
16720 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16721 is @code{off}, symbols must be loaded manually, using the
16722 @code{sharedlibrary} command. The default value is @code{on}.
16724 @cindex memory used for symbol tables
16725 If your program uses lots of shared libraries with debug info that
16726 takes large amounts of memory, you can decrease the @value{GDBN}
16727 memory footprint by preventing it from automatically loading the
16728 symbols from shared libraries. To that end, type @kbd{set
16729 auto-solib-add off} before running the inferior, then load each
16730 library whose debug symbols you do need with @kbd{sharedlibrary
16731 @var{regexp}}, where @var{regexp} is a regular expression that matches
16732 the libraries whose symbols you want to be loaded.
16734 @kindex show auto-solib-add
16735 @item show auto-solib-add
16736 Display the current autoloading mode.
16739 @cindex load shared library
16740 To explicitly load shared library symbols, use the @code{sharedlibrary}
16744 @kindex info sharedlibrary
16746 @item info share @var{regex}
16747 @itemx info sharedlibrary @var{regex}
16748 Print the names of the shared libraries which are currently loaded
16749 that match @var{regex}. If @var{regex} is omitted then print
16750 all shared libraries that are loaded.
16752 @kindex sharedlibrary
16754 @item sharedlibrary @var{regex}
16755 @itemx share @var{regex}
16756 Load shared object library symbols for files matching a
16757 Unix regular expression.
16758 As with files loaded automatically, it only loads shared libraries
16759 required by your program for a core file or after typing @code{run}. If
16760 @var{regex} is omitted all shared libraries required by your program are
16763 @item nosharedlibrary
16764 @kindex nosharedlibrary
16765 @cindex unload symbols from shared libraries
16766 Unload all shared object library symbols. This discards all symbols
16767 that have been loaded from all shared libraries. Symbols from shared
16768 libraries that were loaded by explicit user requests are not
16772 Sometimes you may wish that @value{GDBN} stops and gives you control
16773 when any of shared library events happen. The best way to do this is
16774 to use @code{catch load} and @code{catch unload} (@pxref{Set
16777 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16778 command for this. This command exists for historical reasons. It is
16779 less useful than setting a catchpoint, because it does not allow for
16780 conditions or commands as a catchpoint does.
16783 @item set stop-on-solib-events
16784 @kindex set stop-on-solib-events
16785 This command controls whether @value{GDBN} should give you control
16786 when the dynamic linker notifies it about some shared library event.
16787 The most common event of interest is loading or unloading of a new
16790 @item show stop-on-solib-events
16791 @kindex show stop-on-solib-events
16792 Show whether @value{GDBN} stops and gives you control when shared
16793 library events happen.
16796 Shared libraries are also supported in many cross or remote debugging
16797 configurations. @value{GDBN} needs to have access to the target's libraries;
16798 this can be accomplished either by providing copies of the libraries
16799 on the host system, or by asking @value{GDBN} to automatically retrieve the
16800 libraries from the target. If copies of the target libraries are
16801 provided, they need to be the same as the target libraries, although the
16802 copies on the target can be stripped as long as the copies on the host are
16805 @cindex where to look for shared libraries
16806 For remote debugging, you need to tell @value{GDBN} where the target
16807 libraries are, so that it can load the correct copies---otherwise, it
16808 may try to load the host's libraries. @value{GDBN} has two variables
16809 to specify the search directories for target libraries.
16812 @cindex prefix for shared library file names
16813 @cindex system root, alternate
16814 @kindex set solib-absolute-prefix
16815 @kindex set sysroot
16816 @item set sysroot @var{path}
16817 Use @var{path} as the system root for the program being debugged. Any
16818 absolute shared library paths will be prefixed with @var{path}; many
16819 runtime loaders store the absolute paths to the shared library in the
16820 target program's memory. If you use @code{set sysroot} to find shared
16821 libraries, they need to be laid out in the same way that they are on
16822 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16825 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16826 retrieve the target libraries from the remote system. This is only
16827 supported when using a remote target that supports the @code{remote get}
16828 command (@pxref{File Transfer,,Sending files to a remote system}).
16829 The part of @var{path} following the initial @file{remote:}
16830 (if present) is used as system root prefix on the remote file system.
16831 @footnote{If you want to specify a local system root using a directory
16832 that happens to be named @file{remote:}, you need to use some equivalent
16833 variant of the name like @file{./remote:}.}
16835 For targets with an MS-DOS based filesystem, such as MS-Windows and
16836 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16837 absolute file name with @var{path}. But first, on Unix hosts,
16838 @value{GDBN} converts all backslash directory separators into forward
16839 slashes, because the backslash is not a directory separator on Unix:
16842 c:\foo\bar.dll @result{} c:/foo/bar.dll
16845 Then, @value{GDBN} attempts prefixing the target file name with
16846 @var{path}, and looks for the resulting file name in the host file
16850 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16853 If that does not find the shared library, @value{GDBN} tries removing
16854 the @samp{:} character from the drive spec, both for convenience, and,
16855 for the case of the host file system not supporting file names with
16859 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16862 This makes it possible to have a system root that mirrors a target
16863 with more than one drive. E.g., you may want to setup your local
16864 copies of the target system shared libraries like so (note @samp{c} vs
16868 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16869 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16870 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16874 and point the system root at @file{/path/to/sysroot}, so that
16875 @value{GDBN} can find the correct copies of both
16876 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16878 If that still does not find the shared library, @value{GDBN} tries
16879 removing the whole drive spec from the target file name:
16882 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16885 This last lookup makes it possible to not care about the drive name,
16886 if you don't want or need to.
16888 The @code{set solib-absolute-prefix} command is an alias for @code{set
16891 @cindex default system root
16892 @cindex @samp{--with-sysroot}
16893 You can set the default system root by using the configure-time
16894 @samp{--with-sysroot} option. If the system root is inside
16895 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16896 @samp{--exec-prefix}), then the default system root will be updated
16897 automatically if the installed @value{GDBN} is moved to a new
16900 @kindex show sysroot
16902 Display the current shared library prefix.
16904 @kindex set solib-search-path
16905 @item set solib-search-path @var{path}
16906 If this variable is set, @var{path} is a colon-separated list of
16907 directories to search for shared libraries. @samp{solib-search-path}
16908 is used after @samp{sysroot} fails to locate the library, or if the
16909 path to the library is relative instead of absolute. If you want to
16910 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16911 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16912 finding your host's libraries. @samp{sysroot} is preferred; setting
16913 it to a nonexistent directory may interfere with automatic loading
16914 of shared library symbols.
16916 @kindex show solib-search-path
16917 @item show solib-search-path
16918 Display the current shared library search path.
16920 @cindex DOS file-name semantics of file names.
16921 @kindex set target-file-system-kind (unix|dos-based|auto)
16922 @kindex show target-file-system-kind
16923 @item set target-file-system-kind @var{kind}
16924 Set assumed file system kind for target reported file names.
16926 Shared library file names as reported by the target system may not
16927 make sense as is on the system @value{GDBN} is running on. For
16928 example, when remote debugging a target that has MS-DOS based file
16929 system semantics, from a Unix host, the target may be reporting to
16930 @value{GDBN} a list of loaded shared libraries with file names such as
16931 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16932 drive letters, so the @samp{c:\} prefix is not normally understood as
16933 indicating an absolute file name, and neither is the backslash
16934 normally considered a directory separator character. In that case,
16935 the native file system would interpret this whole absolute file name
16936 as a relative file name with no directory components. This would make
16937 it impossible to point @value{GDBN} at a copy of the remote target's
16938 shared libraries on the host using @code{set sysroot}, and impractical
16939 with @code{set solib-search-path}. Setting
16940 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16941 to interpret such file names similarly to how the target would, and to
16942 map them to file names valid on @value{GDBN}'s native file system
16943 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16944 to one of the supported file system kinds. In that case, @value{GDBN}
16945 tries to determine the appropriate file system variant based on the
16946 current target's operating system (@pxref{ABI, ,Configuring the
16947 Current ABI}). The supported file system settings are:
16951 Instruct @value{GDBN} to assume the target file system is of Unix
16952 kind. Only file names starting the forward slash (@samp{/}) character
16953 are considered absolute, and the directory separator character is also
16957 Instruct @value{GDBN} to assume the target file system is DOS based.
16958 File names starting with either a forward slash, or a drive letter
16959 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16960 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16961 considered directory separators.
16964 Instruct @value{GDBN} to use the file system kind associated with the
16965 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16966 This is the default.
16970 @cindex file name canonicalization
16971 @cindex base name differences
16972 When processing file names provided by the user, @value{GDBN}
16973 frequently needs to compare them to the file names recorded in the
16974 program's debug info. Normally, @value{GDBN} compares just the
16975 @dfn{base names} of the files as strings, which is reasonably fast
16976 even for very large programs. (The base name of a file is the last
16977 portion of its name, after stripping all the leading directories.)
16978 This shortcut in comparison is based upon the assumption that files
16979 cannot have more than one base name. This is usually true, but
16980 references to files that use symlinks or similar filesystem
16981 facilities violate that assumption. If your program records files
16982 using such facilities, or if you provide file names to @value{GDBN}
16983 using symlinks etc., you can set @code{basenames-may-differ} to
16984 @code{true} to instruct @value{GDBN} to completely canonicalize each
16985 pair of file names it needs to compare. This will make file-name
16986 comparisons accurate, but at a price of a significant slowdown.
16989 @item set basenames-may-differ
16990 @kindex set basenames-may-differ
16991 Set whether a source file may have multiple base names.
16993 @item show basenames-may-differ
16994 @kindex show basenames-may-differ
16995 Show whether a source file may have multiple base names.
16998 @node Separate Debug Files
16999 @section Debugging Information in Separate Files
17000 @cindex separate debugging information files
17001 @cindex debugging information in separate files
17002 @cindex @file{.debug} subdirectories
17003 @cindex debugging information directory, global
17004 @cindex global debugging information directories
17005 @cindex build ID, and separate debugging files
17006 @cindex @file{.build-id} directory
17008 @value{GDBN} allows you to put a program's debugging information in a
17009 file separate from the executable itself, in a way that allows
17010 @value{GDBN} to find and load the debugging information automatically.
17011 Since debugging information can be very large---sometimes larger
17012 than the executable code itself---some systems distribute debugging
17013 information for their executables in separate files, which users can
17014 install only when they need to debug a problem.
17016 @value{GDBN} supports two ways of specifying the separate debug info
17021 The executable contains a @dfn{debug link} that specifies the name of
17022 the separate debug info file. The separate debug file's name is
17023 usually @file{@var{executable}.debug}, where @var{executable} is the
17024 name of the corresponding executable file without leading directories
17025 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
17026 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
17027 checksum for the debug file, which @value{GDBN} uses to validate that
17028 the executable and the debug file came from the same build.
17031 The executable contains a @dfn{build ID}, a unique bit string that is
17032 also present in the corresponding debug info file. (This is supported
17033 only on some operating systems, notably those which use the ELF format
17034 for binary files and the @sc{gnu} Binutils.) For more details about
17035 this feature, see the description of the @option{--build-id}
17036 command-line option in @ref{Options, , Command Line Options, ld.info,
17037 The GNU Linker}. The debug info file's name is not specified
17038 explicitly by the build ID, but can be computed from the build ID, see
17042 Depending on the way the debug info file is specified, @value{GDBN}
17043 uses two different methods of looking for the debug file:
17047 For the ``debug link'' method, @value{GDBN} looks up the named file in
17048 the directory of the executable file, then in a subdirectory of that
17049 directory named @file{.debug}, and finally under each one of the global debug
17050 directories, in a subdirectory whose name is identical to the leading
17051 directories of the executable's absolute file name.
17054 For the ``build ID'' method, @value{GDBN} looks in the
17055 @file{.build-id} subdirectory of each one of the global debug directories for
17056 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
17057 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
17058 are the rest of the bit string. (Real build ID strings are 32 or more
17059 hex characters, not 10.)
17062 So, for example, suppose you ask @value{GDBN} to debug
17063 @file{/usr/bin/ls}, which has a debug link that specifies the
17064 file @file{ls.debug}, and a build ID whose value in hex is
17065 @code{abcdef1234}. If the list of the global debug directories includes
17066 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
17067 debug information files, in the indicated order:
17071 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
17073 @file{/usr/bin/ls.debug}
17075 @file{/usr/bin/.debug/ls.debug}
17077 @file{/usr/lib/debug/usr/bin/ls.debug}.
17080 @anchor{debug-file-directory}
17081 Global debugging info directories default to what is set by @value{GDBN}
17082 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
17083 you can also set the global debugging info directories, and view the list
17084 @value{GDBN} is currently using.
17088 @kindex set debug-file-directory
17089 @item set debug-file-directory @var{directories}
17090 Set the directories which @value{GDBN} searches for separate debugging
17091 information files to @var{directory}. Multiple path components can be set
17092 concatenating them by a path separator.
17094 @kindex show debug-file-directory
17095 @item show debug-file-directory
17096 Show the directories @value{GDBN} searches for separate debugging
17101 @cindex @code{.gnu_debuglink} sections
17102 @cindex debug link sections
17103 A debug link is a special section of the executable file named
17104 @code{.gnu_debuglink}. The section must contain:
17108 A filename, with any leading directory components removed, followed by
17111 zero to three bytes of padding, as needed to reach the next four-byte
17112 boundary within the section, and
17114 a four-byte CRC checksum, stored in the same endianness used for the
17115 executable file itself. The checksum is computed on the debugging
17116 information file's full contents by the function given below, passing
17117 zero as the @var{crc} argument.
17120 Any executable file format can carry a debug link, as long as it can
17121 contain a section named @code{.gnu_debuglink} with the contents
17124 @cindex @code{.note.gnu.build-id} sections
17125 @cindex build ID sections
17126 The build ID is a special section in the executable file (and in other
17127 ELF binary files that @value{GDBN} may consider). This section is
17128 often named @code{.note.gnu.build-id}, but that name is not mandatory.
17129 It contains unique identification for the built files---the ID remains
17130 the same across multiple builds of the same build tree. The default
17131 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
17132 content for the build ID string. The same section with an identical
17133 value is present in the original built binary with symbols, in its
17134 stripped variant, and in the separate debugging information file.
17136 The debugging information file itself should be an ordinary
17137 executable, containing a full set of linker symbols, sections, and
17138 debugging information. The sections of the debugging information file
17139 should have the same names, addresses, and sizes as the original file,
17140 but they need not contain any data---much like a @code{.bss} section
17141 in an ordinary executable.
17143 The @sc{gnu} binary utilities (Binutils) package includes the
17144 @samp{objcopy} utility that can produce
17145 the separated executable / debugging information file pairs using the
17146 following commands:
17149 @kbd{objcopy --only-keep-debug foo foo.debug}
17154 These commands remove the debugging
17155 information from the executable file @file{foo} and place it in the file
17156 @file{foo.debug}. You can use the first, second or both methods to link the
17161 The debug link method needs the following additional command to also leave
17162 behind a debug link in @file{foo}:
17165 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
17168 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
17169 a version of the @code{strip} command such that the command @kbd{strip foo -f
17170 foo.debug} has the same functionality as the two @code{objcopy} commands and
17171 the @code{ln -s} command above, together.
17174 Build ID gets embedded into the main executable using @code{ld --build-id} or
17175 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
17176 compatibility fixes for debug files separation are present in @sc{gnu} binary
17177 utilities (Binutils) package since version 2.18.
17182 @cindex CRC algorithm definition
17183 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
17184 IEEE 802.3 using the polynomial:
17186 @c TexInfo requires naked braces for multi-digit exponents for Tex
17187 @c output, but this causes HTML output to barf. HTML has to be set using
17188 @c raw commands. So we end up having to specify this equation in 2
17193 <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>
17194 + <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
17200 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
17201 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
17205 The function is computed byte at a time, taking the least
17206 significant bit of each byte first. The initial pattern
17207 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
17208 the final result is inverted to ensure trailing zeros also affect the
17211 @emph{Note:} This is the same CRC polynomial as used in handling the
17212 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
17213 , @value{GDBN} Remote Serial Protocol}). However in the
17214 case of the Remote Serial Protocol, the CRC is computed @emph{most}
17215 significant bit first, and the result is not inverted, so trailing
17216 zeros have no effect on the CRC value.
17218 To complete the description, we show below the code of the function
17219 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
17220 initially supplied @code{crc} argument means that an initial call to
17221 this function passing in zero will start computing the CRC using
17224 @kindex gnu_debuglink_crc32
17227 gnu_debuglink_crc32 (unsigned long crc,
17228 unsigned char *buf, size_t len)
17230 static const unsigned long crc32_table[256] =
17232 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
17233 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
17234 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
17235 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
17236 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
17237 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
17238 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
17239 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
17240 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
17241 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
17242 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
17243 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
17244 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
17245 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
17246 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
17247 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
17248 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
17249 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
17250 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
17251 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
17252 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
17253 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
17254 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
17255 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
17256 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
17257 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
17258 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
17259 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
17260 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
17261 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
17262 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
17263 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
17264 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
17265 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
17266 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
17267 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
17268 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
17269 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
17270 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
17271 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
17272 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
17273 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
17274 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
17275 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
17276 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
17277 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
17278 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
17279 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
17280 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
17281 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
17282 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
17285 unsigned char *end;
17287 crc = ~crc & 0xffffffff;
17288 for (end = buf + len; buf < end; ++buf)
17289 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17290 return ~crc & 0xffffffff;
17295 This computation does not apply to the ``build ID'' method.
17297 @node MiniDebugInfo
17298 @section Debugging information in a special section
17299 @cindex separate debug sections
17300 @cindex @samp{.gnu_debugdata} section
17302 Some systems ship pre-built executables and libraries that have a
17303 special @samp{.gnu_debugdata} section. This feature is called
17304 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17305 is used to supply extra symbols for backtraces.
17307 The intent of this section is to provide extra minimal debugging
17308 information for use in simple backtraces. It is not intended to be a
17309 replacement for full separate debugging information (@pxref{Separate
17310 Debug Files}). The example below shows the intended use; however,
17311 @value{GDBN} does not currently put restrictions on what sort of
17312 debugging information might be included in the section.
17314 @value{GDBN} has support for this extension. If the section exists,
17315 then it is used provided that no other source of debugging information
17316 can be found, and that @value{GDBN} was configured with LZMA support.
17318 This section can be easily created using @command{objcopy} and other
17319 standard utilities:
17322 # Extract the dynamic symbols from the main binary, there is no need
17323 # to also have these in the normal symbol table
17324 nm -D @var{binary} --format=posix --defined-only \
17325 | awk '@{ print $1 @}' | sort > dynsyms
17327 # Extract all the text (i.e. function) symbols from the debuginfo .
17328 nm @var{binary} --format=posix --defined-only \
17329 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
17332 # Keep all the function symbols not already in the dynamic symbol
17334 comm -13 dynsyms funcsyms > keep_symbols
17336 # Copy the full debuginfo, keeping only a minimal set of symbols and
17337 # removing some unnecessary sections.
17338 objcopy -S --remove-section .gdb_index --remove-section .comment \
17339 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
17341 # Inject the compressed data into the .gnu_debugdata section of the
17344 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17348 @section Index Files Speed Up @value{GDBN}
17349 @cindex index files
17350 @cindex @samp{.gdb_index} section
17352 When @value{GDBN} finds a symbol file, it scans the symbols in the
17353 file in order to construct an internal symbol table. This lets most
17354 @value{GDBN} operations work quickly---at the cost of a delay early
17355 on. For large programs, this delay can be quite lengthy, so
17356 @value{GDBN} provides a way to build an index, which speeds up
17359 The index is stored as a section in the symbol file. @value{GDBN} can
17360 write the index to a file, then you can put it into the symbol file
17361 using @command{objcopy}.
17363 To create an index file, use the @code{save gdb-index} command:
17366 @item save gdb-index @var{directory}
17367 @kindex save gdb-index
17368 Create an index file for each symbol file currently known by
17369 @value{GDBN}. Each file is named after its corresponding symbol file,
17370 with @samp{.gdb-index} appended, and is written into the given
17374 Once you have created an index file you can merge it into your symbol
17375 file, here named @file{symfile}, using @command{objcopy}:
17378 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17379 --set-section-flags .gdb_index=readonly symfile symfile
17382 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17383 sections that have been deprecated. Usually they are deprecated because
17384 they are missing a new feature or have performance issues.
17385 To tell @value{GDBN} to use a deprecated index section anyway
17386 specify @code{set use-deprecated-index-sections on}.
17387 The default is @code{off}.
17388 This can speed up startup, but may result in some functionality being lost.
17389 @xref{Index Section Format}.
17391 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17392 must be done before gdb reads the file. The following will not work:
17395 $ gdb -ex "set use-deprecated-index-sections on" <program>
17398 Instead you must do, for example,
17401 $ gdb -iex "set use-deprecated-index-sections on" <program>
17404 There are currently some limitation on indices. They only work when
17405 for DWARF debugging information, not stabs. And, they do not
17406 currently work for programs using Ada.
17408 @node Symbol Errors
17409 @section Errors Reading Symbol Files
17411 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17412 such as symbol types it does not recognize, or known bugs in compiler
17413 output. By default, @value{GDBN} does not notify you of such problems, since
17414 they are relatively common and primarily of interest to people
17415 debugging compilers. If you are interested in seeing information
17416 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17417 only one message about each such type of problem, no matter how many
17418 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17419 to see how many times the problems occur, with the @code{set
17420 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17423 The messages currently printed, and their meanings, include:
17426 @item inner block not inside outer block in @var{symbol}
17428 The symbol information shows where symbol scopes begin and end
17429 (such as at the start of a function or a block of statements). This
17430 error indicates that an inner scope block is not fully contained
17431 in its outer scope blocks.
17433 @value{GDBN} circumvents the problem by treating the inner block as if it had
17434 the same scope as the outer block. In the error message, @var{symbol}
17435 may be shown as ``@code{(don't know)}'' if the outer block is not a
17438 @item block at @var{address} out of order
17440 The symbol information for symbol scope blocks should occur in
17441 order of increasing addresses. This error indicates that it does not
17444 @value{GDBN} does not circumvent this problem, and has trouble
17445 locating symbols in the source file whose symbols it is reading. (You
17446 can often determine what source file is affected by specifying
17447 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17450 @item bad block start address patched
17452 The symbol information for a symbol scope block has a start address
17453 smaller than the address of the preceding source line. This is known
17454 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17456 @value{GDBN} circumvents the problem by treating the symbol scope block as
17457 starting on the previous source line.
17459 @item bad string table offset in symbol @var{n}
17462 Symbol number @var{n} contains a pointer into the string table which is
17463 larger than the size of the string table.
17465 @value{GDBN} circumvents the problem by considering the symbol to have the
17466 name @code{foo}, which may cause other problems if many symbols end up
17469 @item unknown symbol type @code{0x@var{nn}}
17471 The symbol information contains new data types that @value{GDBN} does
17472 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17473 uncomprehended information, in hexadecimal.
17475 @value{GDBN} circumvents the error by ignoring this symbol information.
17476 This usually allows you to debug your program, though certain symbols
17477 are not accessible. If you encounter such a problem and feel like
17478 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17479 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17480 and examine @code{*bufp} to see the symbol.
17482 @item stub type has NULL name
17484 @value{GDBN} could not find the full definition for a struct or class.
17486 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17487 The symbol information for a C@t{++} member function is missing some
17488 information that recent versions of the compiler should have output for
17491 @item info mismatch between compiler and debugger
17493 @value{GDBN} could not parse a type specification output by the compiler.
17498 @section GDB Data Files
17500 @cindex prefix for data files
17501 @value{GDBN} will sometimes read an auxiliary data file. These files
17502 are kept in a directory known as the @dfn{data directory}.
17504 You can set the data directory's name, and view the name @value{GDBN}
17505 is currently using.
17508 @kindex set data-directory
17509 @item set data-directory @var{directory}
17510 Set the directory which @value{GDBN} searches for auxiliary data files
17511 to @var{directory}.
17513 @kindex show data-directory
17514 @item show data-directory
17515 Show the directory @value{GDBN} searches for auxiliary data files.
17518 @cindex default data directory
17519 @cindex @samp{--with-gdb-datadir}
17520 You can set the default data directory by using the configure-time
17521 @samp{--with-gdb-datadir} option. If the data directory is inside
17522 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17523 @samp{--exec-prefix}), then the default data directory will be updated
17524 automatically if the installed @value{GDBN} is moved to a new
17527 The data directory may also be specified with the
17528 @code{--data-directory} command line option.
17529 @xref{Mode Options}.
17532 @chapter Specifying a Debugging Target
17534 @cindex debugging target
17535 A @dfn{target} is the execution environment occupied by your program.
17537 Often, @value{GDBN} runs in the same host environment as your program;
17538 in that case, the debugging target is specified as a side effect when
17539 you use the @code{file} or @code{core} commands. When you need more
17540 flexibility---for example, running @value{GDBN} on a physically separate
17541 host, or controlling a standalone system over a serial port or a
17542 realtime system over a TCP/IP connection---you can use the @code{target}
17543 command to specify one of the target types configured for @value{GDBN}
17544 (@pxref{Target Commands, ,Commands for Managing Targets}).
17546 @cindex target architecture
17547 It is possible to build @value{GDBN} for several different @dfn{target
17548 architectures}. When @value{GDBN} is built like that, you can choose
17549 one of the available architectures with the @kbd{set architecture}
17553 @kindex set architecture
17554 @kindex show architecture
17555 @item set architecture @var{arch}
17556 This command sets the current target architecture to @var{arch}. The
17557 value of @var{arch} can be @code{"auto"}, in addition to one of the
17558 supported architectures.
17560 @item show architecture
17561 Show the current target architecture.
17563 @item set processor
17565 @kindex set processor
17566 @kindex show processor
17567 These are alias commands for, respectively, @code{set architecture}
17568 and @code{show architecture}.
17572 * Active Targets:: Active targets
17573 * Target Commands:: Commands for managing targets
17574 * Byte Order:: Choosing target byte order
17577 @node Active Targets
17578 @section Active Targets
17580 @cindex stacking targets
17581 @cindex active targets
17582 @cindex multiple targets
17584 There are multiple classes of targets such as: processes, executable files or
17585 recording sessions. Core files belong to the process class, making core file
17586 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17587 on multiple active targets, one in each class. This allows you to (for
17588 example) start a process and inspect its activity, while still having access to
17589 the executable file after the process finishes. Or if you start process
17590 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17591 presented a virtual layer of the recording target, while the process target
17592 remains stopped at the chronologically last point of the process execution.
17594 Use the @code{core-file} and @code{exec-file} commands to select a new core
17595 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17596 specify as a target a process that is already running, use the @code{attach}
17597 command (@pxref{Attach, ,Debugging an Already-running Process}).
17599 @node Target Commands
17600 @section Commands for Managing Targets
17603 @item target @var{type} @var{parameters}
17604 Connects the @value{GDBN} host environment to a target machine or
17605 process. A target is typically a protocol for talking to debugging
17606 facilities. You use the argument @var{type} to specify the type or
17607 protocol of the target machine.
17609 Further @var{parameters} are interpreted by the target protocol, but
17610 typically include things like device names or host names to connect
17611 with, process numbers, and baud rates.
17613 The @code{target} command does not repeat if you press @key{RET} again
17614 after executing the command.
17616 @kindex help target
17618 Displays the names of all targets available. To display targets
17619 currently selected, use either @code{info target} or @code{info files}
17620 (@pxref{Files, ,Commands to Specify Files}).
17622 @item help target @var{name}
17623 Describe a particular target, including any parameters necessary to
17626 @kindex set gnutarget
17627 @item set gnutarget @var{args}
17628 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17629 knows whether it is reading an @dfn{executable},
17630 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17631 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17632 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17635 @emph{Warning:} To specify a file format with @code{set gnutarget},
17636 you must know the actual BFD name.
17640 @xref{Files, , Commands to Specify Files}.
17642 @kindex show gnutarget
17643 @item show gnutarget
17644 Use the @code{show gnutarget} command to display what file format
17645 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17646 @value{GDBN} will determine the file format for each file automatically,
17647 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17650 @cindex common targets
17651 Here are some common targets (available, or not, depending on the GDB
17656 @item target exec @var{program}
17657 @cindex executable file target
17658 An executable file. @samp{target exec @var{program}} is the same as
17659 @samp{exec-file @var{program}}.
17661 @item target core @var{filename}
17662 @cindex core dump file target
17663 A core dump file. @samp{target core @var{filename}} is the same as
17664 @samp{core-file @var{filename}}.
17666 @item target remote @var{medium}
17667 @cindex remote target
17668 A remote system connected to @value{GDBN} via a serial line or network
17669 connection. This command tells @value{GDBN} to use its own remote
17670 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17672 For example, if you have a board connected to @file{/dev/ttya} on the
17673 machine running @value{GDBN}, you could say:
17676 target remote /dev/ttya
17679 @code{target remote} supports the @code{load} command. This is only
17680 useful if you have some other way of getting the stub to the target
17681 system, and you can put it somewhere in memory where it won't get
17682 clobbered by the download.
17684 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17685 @cindex built-in simulator target
17686 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17694 works; however, you cannot assume that a specific memory map, device
17695 drivers, or even basic I/O is available, although some simulators do
17696 provide these. For info about any processor-specific simulator details,
17697 see the appropriate section in @ref{Embedded Processors, ,Embedded
17702 Different targets are available on different configurations of @value{GDBN};
17703 your configuration may have more or fewer targets.
17705 Many remote targets require you to download the executable's code once
17706 you've successfully established a connection. You may wish to control
17707 various aspects of this process.
17712 @kindex set hash@r{, for remote monitors}
17713 @cindex hash mark while downloading
17714 This command controls whether a hash mark @samp{#} is displayed while
17715 downloading a file to the remote monitor. If on, a hash mark is
17716 displayed after each S-record is successfully downloaded to the
17720 @kindex show hash@r{, for remote monitors}
17721 Show the current status of displaying the hash mark.
17723 @item set debug monitor
17724 @kindex set debug monitor
17725 @cindex display remote monitor communications
17726 Enable or disable display of communications messages between
17727 @value{GDBN} and the remote monitor.
17729 @item show debug monitor
17730 @kindex show debug monitor
17731 Show the current status of displaying communications between
17732 @value{GDBN} and the remote monitor.
17737 @kindex load @var{filename}
17738 @item load @var{filename}
17740 Depending on what remote debugging facilities are configured into
17741 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17742 is meant to make @var{filename} (an executable) available for debugging
17743 on the remote system---by downloading, or dynamic linking, for example.
17744 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17745 the @code{add-symbol-file} command.
17747 If your @value{GDBN} does not have a @code{load} command, attempting to
17748 execute it gets the error message ``@code{You can't do that when your
17749 target is @dots{}}''
17751 The file is loaded at whatever address is specified in the executable.
17752 For some object file formats, you can specify the load address when you
17753 link the program; for other formats, like a.out, the object file format
17754 specifies a fixed address.
17755 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17757 Depending on the remote side capabilities, @value{GDBN} may be able to
17758 load programs into flash memory.
17760 @code{load} does not repeat if you press @key{RET} again after using it.
17764 @section Choosing Target Byte Order
17766 @cindex choosing target byte order
17767 @cindex target byte order
17769 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17770 offer the ability to run either big-endian or little-endian byte
17771 orders. Usually the executable or symbol will include a bit to
17772 designate the endian-ness, and you will not need to worry about
17773 which to use. However, you may still find it useful to adjust
17774 @value{GDBN}'s idea of processor endian-ness manually.
17778 @item set endian big
17779 Instruct @value{GDBN} to assume the target is big-endian.
17781 @item set endian little
17782 Instruct @value{GDBN} to assume the target is little-endian.
17784 @item set endian auto
17785 Instruct @value{GDBN} to use the byte order associated with the
17789 Display @value{GDBN}'s current idea of the target byte order.
17793 Note that these commands merely adjust interpretation of symbolic
17794 data on the host, and that they have absolutely no effect on the
17798 @node Remote Debugging
17799 @chapter Debugging Remote Programs
17800 @cindex remote debugging
17802 If you are trying to debug a program running on a machine that cannot run
17803 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17804 For example, you might use remote debugging on an operating system kernel,
17805 or on a small system which does not have a general purpose operating system
17806 powerful enough to run a full-featured debugger.
17808 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17809 to make this work with particular debugging targets. In addition,
17810 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17811 but not specific to any particular target system) which you can use if you
17812 write the remote stubs---the code that runs on the remote system to
17813 communicate with @value{GDBN}.
17815 Other remote targets may be available in your
17816 configuration of @value{GDBN}; use @code{help target} to list them.
17819 * Connecting:: Connecting to a remote target
17820 * File Transfer:: Sending files to a remote system
17821 * Server:: Using the gdbserver program
17822 * Remote Configuration:: Remote configuration
17823 * Remote Stub:: Implementing a remote stub
17827 @section Connecting to a Remote Target
17829 On the @value{GDBN} host machine, you will need an unstripped copy of
17830 your program, since @value{GDBN} needs symbol and debugging information.
17831 Start up @value{GDBN} as usual, using the name of the local copy of your
17832 program as the first argument.
17834 @cindex @code{target remote}
17835 @value{GDBN} can communicate with the target over a serial line, or
17836 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17837 each case, @value{GDBN} uses the same protocol for debugging your
17838 program; only the medium carrying the debugging packets varies. The
17839 @code{target remote} command establishes a connection to the target.
17840 Its arguments indicate which medium to use:
17844 @item target remote @var{serial-device}
17845 @cindex serial line, @code{target remote}
17846 Use @var{serial-device} to communicate with the target. For example,
17847 to use a serial line connected to the device named @file{/dev/ttyb}:
17850 target remote /dev/ttyb
17853 If you're using a serial line, you may want to give @value{GDBN} the
17854 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17855 (@pxref{Remote Configuration, set remotebaud}) before the
17856 @code{target} command.
17858 @item target remote @code{@var{host}:@var{port}}
17859 @itemx target remote @code{tcp:@var{host}:@var{port}}
17860 @cindex @acronym{TCP} port, @code{target remote}
17861 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17862 The @var{host} may be either a host name or a numeric @acronym{IP}
17863 address; @var{port} must be a decimal number. The @var{host} could be
17864 the target machine itself, if it is directly connected to the net, or
17865 it might be a terminal server which in turn has a serial line to the
17868 For example, to connect to port 2828 on a terminal server named
17872 target remote manyfarms:2828
17875 If your remote target is actually running on the same machine as your
17876 debugger session (e.g.@: a simulator for your target running on the
17877 same host), you can omit the hostname. For example, to connect to
17878 port 1234 on your local machine:
17881 target remote :1234
17885 Note that the colon is still required here.
17887 @item target remote @code{udp:@var{host}:@var{port}}
17888 @cindex @acronym{UDP} port, @code{target remote}
17889 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17890 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17893 target remote udp:manyfarms:2828
17896 When using a @acronym{UDP} connection for remote debugging, you should
17897 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17898 can silently drop packets on busy or unreliable networks, which will
17899 cause havoc with your debugging session.
17901 @item target remote | @var{command}
17902 @cindex pipe, @code{target remote} to
17903 Run @var{command} in the background and communicate with it using a
17904 pipe. The @var{command} is a shell command, to be parsed and expanded
17905 by the system's command shell, @code{/bin/sh}; it should expect remote
17906 protocol packets on its standard input, and send replies on its
17907 standard output. You could use this to run a stand-alone simulator
17908 that speaks the remote debugging protocol, to make net connections
17909 using programs like @code{ssh}, or for other similar tricks.
17911 If @var{command} closes its standard output (perhaps by exiting),
17912 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17913 program has already exited, this will have no effect.)
17917 Once the connection has been established, you can use all the usual
17918 commands to examine and change data. The remote program is already
17919 running; you can use @kbd{step} and @kbd{continue}, and you do not
17920 need to use @kbd{run}.
17922 @cindex interrupting remote programs
17923 @cindex remote programs, interrupting
17924 Whenever @value{GDBN} is waiting for the remote program, if you type the
17925 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17926 program. This may or may not succeed, depending in part on the hardware
17927 and the serial drivers the remote system uses. If you type the
17928 interrupt character once again, @value{GDBN} displays this prompt:
17931 Interrupted while waiting for the program.
17932 Give up (and stop debugging it)? (y or n)
17935 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17936 (If you decide you want to try again later, you can use @samp{target
17937 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17938 goes back to waiting.
17941 @kindex detach (remote)
17943 When you have finished debugging the remote program, you can use the
17944 @code{detach} command to release it from @value{GDBN} control.
17945 Detaching from the target normally resumes its execution, but the results
17946 will depend on your particular remote stub. After the @code{detach}
17947 command, @value{GDBN} is free to connect to another target.
17951 The @code{disconnect} command behaves like @code{detach}, except that
17952 the target is generally not resumed. It will wait for @value{GDBN}
17953 (this instance or another one) to connect and continue debugging. After
17954 the @code{disconnect} command, @value{GDBN} is again free to connect to
17957 @cindex send command to remote monitor
17958 @cindex extend @value{GDBN} for remote targets
17959 @cindex add new commands for external monitor
17961 @item monitor @var{cmd}
17962 This command allows you to send arbitrary commands directly to the
17963 remote monitor. Since @value{GDBN} doesn't care about the commands it
17964 sends like this, this command is the way to extend @value{GDBN}---you
17965 can add new commands that only the external monitor will understand
17969 @node File Transfer
17970 @section Sending files to a remote system
17971 @cindex remote target, file transfer
17972 @cindex file transfer
17973 @cindex sending files to remote systems
17975 Some remote targets offer the ability to transfer files over the same
17976 connection used to communicate with @value{GDBN}. This is convenient
17977 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17978 running @code{gdbserver} over a network interface. For other targets,
17979 e.g.@: embedded devices with only a single serial port, this may be
17980 the only way to upload or download files.
17982 Not all remote targets support these commands.
17986 @item remote put @var{hostfile} @var{targetfile}
17987 Copy file @var{hostfile} from the host system (the machine running
17988 @value{GDBN}) to @var{targetfile} on the target system.
17991 @item remote get @var{targetfile} @var{hostfile}
17992 Copy file @var{targetfile} from the target system to @var{hostfile}
17993 on the host system.
17995 @kindex remote delete
17996 @item remote delete @var{targetfile}
17997 Delete @var{targetfile} from the target system.
18002 @section Using the @code{gdbserver} Program
18005 @cindex remote connection without stubs
18006 @code{gdbserver} is a control program for Unix-like systems, which
18007 allows you to connect your program with a remote @value{GDBN} via
18008 @code{target remote}---but without linking in the usual debugging stub.
18010 @code{gdbserver} is not a complete replacement for the debugging stubs,
18011 because it requires essentially the same operating-system facilities
18012 that @value{GDBN} itself does. In fact, a system that can run
18013 @code{gdbserver} to connect to a remote @value{GDBN} could also run
18014 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
18015 because it is a much smaller program than @value{GDBN} itself. It is
18016 also easier to port than all of @value{GDBN}, so you may be able to get
18017 started more quickly on a new system by using @code{gdbserver}.
18018 Finally, if you develop code for real-time systems, you may find that
18019 the tradeoffs involved in real-time operation make it more convenient to
18020 do as much development work as possible on another system, for example
18021 by cross-compiling. You can use @code{gdbserver} to make a similar
18022 choice for debugging.
18024 @value{GDBN} and @code{gdbserver} communicate via either a serial line
18025 or a TCP connection, using the standard @value{GDBN} remote serial
18029 @emph{Warning:} @code{gdbserver} does not have any built-in security.
18030 Do not run @code{gdbserver} connected to any public network; a
18031 @value{GDBN} connection to @code{gdbserver} provides access to the
18032 target system with the same privileges as the user running
18036 @subsection Running @code{gdbserver}
18037 @cindex arguments, to @code{gdbserver}
18038 @cindex @code{gdbserver}, command-line arguments
18040 Run @code{gdbserver} on the target system. You need a copy of the
18041 program you want to debug, including any libraries it requires.
18042 @code{gdbserver} does not need your program's symbol table, so you can
18043 strip the program if necessary to save space. @value{GDBN} on the host
18044 system does all the symbol handling.
18046 To use the server, you must tell it how to communicate with @value{GDBN};
18047 the name of your program; and the arguments for your program. The usual
18051 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
18054 @var{comm} is either a device name (to use a serial line), or a TCP
18055 hostname and portnumber, or @code{-} or @code{stdio} to use
18056 stdin/stdout of @code{gdbserver}.
18057 For example, to debug Emacs with the argument
18058 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
18062 target> gdbserver /dev/com1 emacs foo.txt
18065 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
18068 To use a TCP connection instead of a serial line:
18071 target> gdbserver host:2345 emacs foo.txt
18074 The only difference from the previous example is the first argument,
18075 specifying that you are communicating with the host @value{GDBN} via
18076 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
18077 expect a TCP connection from machine @samp{host} to local TCP port 2345.
18078 (Currently, the @samp{host} part is ignored.) You can choose any number
18079 you want for the port number as long as it does not conflict with any
18080 TCP ports already in use on the target system (for example, @code{23} is
18081 reserved for @code{telnet}).@footnote{If you choose a port number that
18082 conflicts with another service, @code{gdbserver} prints an error message
18083 and exits.} You must use the same port number with the host @value{GDBN}
18084 @code{target remote} command.
18086 The @code{stdio} connection is useful when starting @code{gdbserver}
18090 (gdb) target remote | ssh -T hostname gdbserver - hello
18093 The @samp{-T} option to ssh is provided because we don't need a remote pty,
18094 and we don't want escape-character handling. Ssh does this by default when
18095 a command is provided, the flag is provided to make it explicit.
18096 You could elide it if you want to.
18098 Programs started with stdio-connected gdbserver have @file{/dev/null} for
18099 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
18100 display through a pipe connected to gdbserver.
18101 Both @code{stdout} and @code{stderr} use the same pipe.
18103 @subsubsection Attaching to a Running Program
18104 @cindex attach to a program, @code{gdbserver}
18105 @cindex @option{--attach}, @code{gdbserver} option
18107 On some targets, @code{gdbserver} can also attach to running programs.
18108 This is accomplished via the @code{--attach} argument. The syntax is:
18111 target> gdbserver --attach @var{comm} @var{pid}
18114 @var{pid} is the process ID of a currently running process. It isn't necessary
18115 to point @code{gdbserver} at a binary for the running process.
18118 You can debug processes by name instead of process ID if your target has the
18119 @code{pidof} utility:
18122 target> gdbserver --attach @var{comm} `pidof @var{program}`
18125 In case more than one copy of @var{program} is running, or @var{program}
18126 has multiple threads, most versions of @code{pidof} support the
18127 @code{-s} option to only return the first process ID.
18129 @subsubsection Multi-Process Mode for @code{gdbserver}
18130 @cindex @code{gdbserver}, multiple processes
18131 @cindex multiple processes with @code{gdbserver}
18133 When you connect to @code{gdbserver} using @code{target remote},
18134 @code{gdbserver} debugs the specified program only once. When the
18135 program exits, or you detach from it, @value{GDBN} closes the connection
18136 and @code{gdbserver} exits.
18138 If you connect using @kbd{target extended-remote}, @code{gdbserver}
18139 enters multi-process mode. When the debugged program exits, or you
18140 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
18141 though no program is running. The @code{run} and @code{attach}
18142 commands instruct @code{gdbserver} to run or attach to a new program.
18143 The @code{run} command uses @code{set remote exec-file} (@pxref{set
18144 remote exec-file}) to select the program to run. Command line
18145 arguments are supported, except for wildcard expansion and I/O
18146 redirection (@pxref{Arguments}).
18148 @cindex @option{--multi}, @code{gdbserver} option
18149 To start @code{gdbserver} without supplying an initial command to run
18150 or process ID to attach, use the @option{--multi} command line option.
18151 Then you can connect using @kbd{target extended-remote} and start
18152 the program you want to debug.
18154 In multi-process mode @code{gdbserver} does not automatically exit unless you
18155 use the option @option{--once}. You can terminate it by using
18156 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
18157 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
18158 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
18159 @option{--multi} option to @code{gdbserver} has no influence on that.
18161 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
18163 This section applies only when @code{gdbserver} is run to listen on a TCP port.
18165 @code{gdbserver} normally terminates after all of its debugged processes have
18166 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
18167 extended-remote}, @code{gdbserver} stays running even with no processes left.
18168 @value{GDBN} normally terminates the spawned debugged process on its exit,
18169 which normally also terminates @code{gdbserver} in the @kbd{target remote}
18170 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
18171 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
18172 stays running even in the @kbd{target remote} mode.
18174 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
18175 Such reconnecting is useful for features like @ref{disconnected tracing}. For
18176 completeness, at most one @value{GDBN} can be connected at a time.
18178 @cindex @option{--once}, @code{gdbserver} option
18179 By default, @code{gdbserver} keeps the listening TCP port open, so that
18180 additional connections are possible. However, if you start @code{gdbserver}
18181 with the @option{--once} option, it will stop listening for any further
18182 connection attempts after connecting to the first @value{GDBN} session. This
18183 means no further connections to @code{gdbserver} will be possible after the
18184 first one. It also means @code{gdbserver} will terminate after the first
18185 connection with remote @value{GDBN} has closed, even for unexpectedly closed
18186 connections and even in the @kbd{target extended-remote} mode. The
18187 @option{--once} option allows reusing the same port number for connecting to
18188 multiple instances of @code{gdbserver} running on the same host, since each
18189 instance closes its port after the first connection.
18191 @subsubsection Other Command-Line Arguments for @code{gdbserver}
18193 @cindex @option{--debug}, @code{gdbserver} option
18194 The @option{--debug} option tells @code{gdbserver} to display extra
18195 status information about the debugging process.
18196 @cindex @option{--remote-debug}, @code{gdbserver} option
18197 The @option{--remote-debug} option tells @code{gdbserver} to display
18198 remote protocol debug output. These options are intended for
18199 @code{gdbserver} development and for bug reports to the developers.
18201 @cindex @option{--wrapper}, @code{gdbserver} option
18202 The @option{--wrapper} option specifies a wrapper to launch programs
18203 for debugging. The option should be followed by the name of the
18204 wrapper, then any command-line arguments to pass to the wrapper, then
18205 @kbd{--} indicating the end of the wrapper arguments.
18207 @code{gdbserver} runs the specified wrapper program with a combined
18208 command line including the wrapper arguments, then the name of the
18209 program to debug, then any arguments to the program. The wrapper
18210 runs until it executes your program, and then @value{GDBN} gains control.
18212 You can use any program that eventually calls @code{execve} with
18213 its arguments as a wrapper. Several standard Unix utilities do
18214 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
18215 with @code{exec "$@@"} will also work.
18217 For example, you can use @code{env} to pass an environment variable to
18218 the debugged program, without setting the variable in @code{gdbserver}'s
18222 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
18225 @subsection Connecting to @code{gdbserver}
18227 Run @value{GDBN} on the host system.
18229 First make sure you have the necessary symbol files. Load symbols for
18230 your application using the @code{file} command before you connect. Use
18231 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
18232 was compiled with the correct sysroot using @code{--with-sysroot}).
18234 The symbol file and target libraries must exactly match the executable
18235 and libraries on the target, with one exception: the files on the host
18236 system should not be stripped, even if the files on the target system
18237 are. Mismatched or missing files will lead to confusing results
18238 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
18239 files may also prevent @code{gdbserver} from debugging multi-threaded
18242 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
18243 For TCP connections, you must start up @code{gdbserver} prior to using
18244 the @code{target remote} command. Otherwise you may get an error whose
18245 text depends on the host system, but which usually looks something like
18246 @samp{Connection refused}. Don't use the @code{load}
18247 command in @value{GDBN} when using @code{gdbserver}, since the program is
18248 already on the target.
18250 @subsection Monitor Commands for @code{gdbserver}
18251 @cindex monitor commands, for @code{gdbserver}
18252 @anchor{Monitor Commands for gdbserver}
18254 During a @value{GDBN} session using @code{gdbserver}, you can use the
18255 @code{monitor} command to send special requests to @code{gdbserver}.
18256 Here are the available commands.
18260 List the available monitor commands.
18262 @item monitor set debug 0
18263 @itemx monitor set debug 1
18264 Disable or enable general debugging messages.
18266 @item monitor set remote-debug 0
18267 @itemx monitor set remote-debug 1
18268 Disable or enable specific debugging messages associated with the remote
18269 protocol (@pxref{Remote Protocol}).
18271 @item monitor set libthread-db-search-path [PATH]
18272 @cindex gdbserver, search path for @code{libthread_db}
18273 When this command is issued, @var{path} is a colon-separated list of
18274 directories to search for @code{libthread_db} (@pxref{Threads,,set
18275 libthread-db-search-path}). If you omit @var{path},
18276 @samp{libthread-db-search-path} will be reset to its default value.
18278 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18279 not supported in @code{gdbserver}.
18282 Tell gdbserver to exit immediately. This command should be followed by
18283 @code{disconnect} to close the debugging session. @code{gdbserver} will
18284 detach from any attached processes and kill any processes it created.
18285 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18286 of a multi-process mode debug session.
18290 @subsection Tracepoints support in @code{gdbserver}
18291 @cindex tracepoints support in @code{gdbserver}
18293 On some targets, @code{gdbserver} supports tracepoints, fast
18294 tracepoints and static tracepoints.
18296 For fast or static tracepoints to work, a special library called the
18297 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18298 This library is built and distributed as an integral part of
18299 @code{gdbserver}. In addition, support for static tracepoints
18300 requires building the in-process agent library with static tracepoints
18301 support. At present, the UST (LTTng Userspace Tracer,
18302 @url{http://lttng.org/ust}) tracing engine is supported. This support
18303 is automatically available if UST development headers are found in the
18304 standard include path when @code{gdbserver} is built, or if
18305 @code{gdbserver} was explicitly configured using @option{--with-ust}
18306 to point at such headers. You can explicitly disable the support
18307 using @option{--with-ust=no}.
18309 There are several ways to load the in-process agent in your program:
18312 @item Specifying it as dependency at link time
18314 You can link your program dynamically with the in-process agent
18315 library. On most systems, this is accomplished by adding
18316 @code{-linproctrace} to the link command.
18318 @item Using the system's preloading mechanisms
18320 You can force loading the in-process agent at startup time by using
18321 your system's support for preloading shared libraries. Many Unixes
18322 support the concept of preloading user defined libraries. In most
18323 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18324 in the environment. See also the description of @code{gdbserver}'s
18325 @option{--wrapper} command line option.
18327 @item Using @value{GDBN} to force loading the agent at run time
18329 On some systems, you can force the inferior to load a shared library,
18330 by calling a dynamic loader function in the inferior that takes care
18331 of dynamically looking up and loading a shared library. On most Unix
18332 systems, the function is @code{dlopen}. You'll use the @code{call}
18333 command for that. For example:
18336 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18339 Note that on most Unix systems, for the @code{dlopen} function to be
18340 available, the program needs to be linked with @code{-ldl}.
18343 On systems that have a userspace dynamic loader, like most Unix
18344 systems, when you connect to @code{gdbserver} using @code{target
18345 remote}, you'll find that the program is stopped at the dynamic
18346 loader's entry point, and no shared library has been loaded in the
18347 program's address space yet, including the in-process agent. In that
18348 case, before being able to use any of the fast or static tracepoints
18349 features, you need to let the loader run and load the shared
18350 libraries. The simplest way to do that is to run the program to the
18351 main procedure. E.g., if debugging a C or C@t{++} program, start
18352 @code{gdbserver} like so:
18355 $ gdbserver :9999 myprogram
18358 Start GDB and connect to @code{gdbserver} like so, and run to main:
18362 (@value{GDBP}) target remote myhost:9999
18363 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18364 (@value{GDBP}) b main
18365 (@value{GDBP}) continue
18368 The in-process tracing agent library should now be loaded into the
18369 process; you can confirm it with the @code{info sharedlibrary}
18370 command, which will list @file{libinproctrace.so} as loaded in the
18371 process. You are now ready to install fast tracepoints, list static
18372 tracepoint markers, probe static tracepoints markers, and start
18375 @node Remote Configuration
18376 @section Remote Configuration
18379 @kindex show remote
18380 This section documents the configuration options available when
18381 debugging remote programs. For the options related to the File I/O
18382 extensions of the remote protocol, see @ref{system,
18383 system-call-allowed}.
18386 @item set remoteaddresssize @var{bits}
18387 @cindex address size for remote targets
18388 @cindex bits in remote address
18389 Set the maximum size of address in a memory packet to the specified
18390 number of bits. @value{GDBN} will mask off the address bits above
18391 that number, when it passes addresses to the remote target. The
18392 default value is the number of bits in the target's address.
18394 @item show remoteaddresssize
18395 Show the current value of remote address size in bits.
18397 @item set remotebaud @var{n}
18398 @cindex baud rate for remote targets
18399 Set the baud rate for the remote serial I/O to @var{n} baud. The
18400 value is used to set the speed of the serial port used for debugging
18403 @item show remotebaud
18404 Show the current speed of the remote connection.
18406 @item set remotebreak
18407 @cindex interrupt remote programs
18408 @cindex BREAK signal instead of Ctrl-C
18409 @anchor{set remotebreak}
18410 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18411 when you type @kbd{Ctrl-c} to interrupt the program running
18412 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18413 character instead. The default is off, since most remote systems
18414 expect to see @samp{Ctrl-C} as the interrupt signal.
18416 @item show remotebreak
18417 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18418 interrupt the remote program.
18420 @item set remoteflow on
18421 @itemx set remoteflow off
18422 @kindex set remoteflow
18423 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18424 on the serial port used to communicate to the remote target.
18426 @item show remoteflow
18427 @kindex show remoteflow
18428 Show the current setting of hardware flow control.
18430 @item set remotelogbase @var{base}
18431 Set the base (a.k.a.@: radix) of logging serial protocol
18432 communications to @var{base}. Supported values of @var{base} are:
18433 @code{ascii}, @code{octal}, and @code{hex}. The default is
18436 @item show remotelogbase
18437 Show the current setting of the radix for logging remote serial
18440 @item set remotelogfile @var{file}
18441 @cindex record serial communications on file
18442 Record remote serial communications on the named @var{file}. The
18443 default is not to record at all.
18445 @item show remotelogfile.
18446 Show the current setting of the file name on which to record the
18447 serial communications.
18449 @item set remotetimeout @var{num}
18450 @cindex timeout for serial communications
18451 @cindex remote timeout
18452 Set the timeout limit to wait for the remote target to respond to
18453 @var{num} seconds. The default is 2 seconds.
18455 @item show remotetimeout
18456 Show the current number of seconds to wait for the remote target
18459 @cindex limit hardware breakpoints and watchpoints
18460 @cindex remote target, limit break- and watchpoints
18461 @anchor{set remote hardware-watchpoint-limit}
18462 @anchor{set remote hardware-breakpoint-limit}
18463 @item set remote hardware-watchpoint-limit @var{limit}
18464 @itemx set remote hardware-breakpoint-limit @var{limit}
18465 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18466 watchpoints. A limit of -1, the default, is treated as unlimited.
18468 @cindex limit hardware watchpoints length
18469 @cindex remote target, limit watchpoints length
18470 @anchor{set remote hardware-watchpoint-length-limit}
18471 @item set remote hardware-watchpoint-length-limit @var{limit}
18472 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18473 a remote hardware watchpoint. A limit of -1, the default, is treated
18476 @item show remote hardware-watchpoint-length-limit
18477 Show the current limit (in bytes) of the maximum length of
18478 a remote hardware watchpoint.
18480 @item set remote exec-file @var{filename}
18481 @itemx show remote exec-file
18482 @anchor{set remote exec-file}
18483 @cindex executable file, for remote target
18484 Select the file used for @code{run} with @code{target
18485 extended-remote}. This should be set to a filename valid on the
18486 target system. If it is not set, the target will use a default
18487 filename (e.g.@: the last program run).
18489 @item set remote interrupt-sequence
18490 @cindex interrupt remote programs
18491 @cindex select Ctrl-C, BREAK or BREAK-g
18492 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18493 @samp{BREAK-g} as the
18494 sequence to the remote target in order to interrupt the execution.
18495 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18496 is high level of serial line for some certain time.
18497 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18498 It is @code{BREAK} signal followed by character @code{g}.
18500 @item show interrupt-sequence
18501 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18502 is sent by @value{GDBN} to interrupt the remote program.
18503 @code{BREAK-g} is BREAK signal followed by @code{g} and
18504 also known as Magic SysRq g.
18506 @item set remote interrupt-on-connect
18507 @cindex send interrupt-sequence on start
18508 Specify whether interrupt-sequence is sent to remote target when
18509 @value{GDBN} connects to it. This is mostly needed when you debug
18510 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18511 which is known as Magic SysRq g in order to connect @value{GDBN}.
18513 @item show interrupt-on-connect
18514 Show whether interrupt-sequence is sent
18515 to remote target when @value{GDBN} connects to it.
18519 @item set tcp auto-retry on
18520 @cindex auto-retry, for remote TCP target
18521 Enable auto-retry for remote TCP connections. This is useful if the remote
18522 debugging agent is launched in parallel with @value{GDBN}; there is a race
18523 condition because the agent may not become ready to accept the connection
18524 before @value{GDBN} attempts to connect. When auto-retry is
18525 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18526 to establish the connection using the timeout specified by
18527 @code{set tcp connect-timeout}.
18529 @item set tcp auto-retry off
18530 Do not auto-retry failed TCP connections.
18532 @item show tcp auto-retry
18533 Show the current auto-retry setting.
18535 @item set tcp connect-timeout @var{seconds}
18536 @itemx set tcp connect-timeout unlimited
18537 @cindex connection timeout, for remote TCP target
18538 @cindex timeout, for remote target connection
18539 Set the timeout for establishing a TCP connection to the remote target to
18540 @var{seconds}. The timeout affects both polling to retry failed connections
18541 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18542 that are merely slow to complete, and represents an approximate cumulative
18543 value. If @var{seconds} is @code{unlimited}, there is no timeout and
18544 @value{GDBN} will keep attempting to establish a connection forever,
18545 unless interrupted with @kbd{Ctrl-c}. The default is 15 seconds.
18547 @item show tcp connect-timeout
18548 Show the current connection timeout setting.
18551 @cindex remote packets, enabling and disabling
18552 The @value{GDBN} remote protocol autodetects the packets supported by
18553 your debugging stub. If you need to override the autodetection, you
18554 can use these commands to enable or disable individual packets. Each
18555 packet can be set to @samp{on} (the remote target supports this
18556 packet), @samp{off} (the remote target does not support this packet),
18557 or @samp{auto} (detect remote target support for this packet). They
18558 all default to @samp{auto}. For more information about each packet,
18559 see @ref{Remote Protocol}.
18561 During normal use, you should not have to use any of these commands.
18562 If you do, that may be a bug in your remote debugging stub, or a bug
18563 in @value{GDBN}. You may want to report the problem to the
18564 @value{GDBN} developers.
18566 For each packet @var{name}, the command to enable or disable the
18567 packet is @code{set remote @var{name}-packet}. The available settings
18570 @multitable @columnfractions 0.28 0.32 0.25
18573 @tab Related Features
18575 @item @code{fetch-register}
18577 @tab @code{info registers}
18579 @item @code{set-register}
18583 @item @code{binary-download}
18585 @tab @code{load}, @code{set}
18587 @item @code{read-aux-vector}
18588 @tab @code{qXfer:auxv:read}
18589 @tab @code{info auxv}
18591 @item @code{symbol-lookup}
18592 @tab @code{qSymbol}
18593 @tab Detecting multiple threads
18595 @item @code{attach}
18596 @tab @code{vAttach}
18599 @item @code{verbose-resume}
18601 @tab Stepping or resuming multiple threads
18607 @item @code{software-breakpoint}
18611 @item @code{hardware-breakpoint}
18615 @item @code{write-watchpoint}
18619 @item @code{read-watchpoint}
18623 @item @code{access-watchpoint}
18627 @item @code{target-features}
18628 @tab @code{qXfer:features:read}
18629 @tab @code{set architecture}
18631 @item @code{library-info}
18632 @tab @code{qXfer:libraries:read}
18633 @tab @code{info sharedlibrary}
18635 @item @code{memory-map}
18636 @tab @code{qXfer:memory-map:read}
18637 @tab @code{info mem}
18639 @item @code{read-sdata-object}
18640 @tab @code{qXfer:sdata:read}
18641 @tab @code{print $_sdata}
18643 @item @code{read-spu-object}
18644 @tab @code{qXfer:spu:read}
18645 @tab @code{info spu}
18647 @item @code{write-spu-object}
18648 @tab @code{qXfer:spu:write}
18649 @tab @code{info spu}
18651 @item @code{read-siginfo-object}
18652 @tab @code{qXfer:siginfo:read}
18653 @tab @code{print $_siginfo}
18655 @item @code{write-siginfo-object}
18656 @tab @code{qXfer:siginfo:write}
18657 @tab @code{set $_siginfo}
18659 @item @code{threads}
18660 @tab @code{qXfer:threads:read}
18661 @tab @code{info threads}
18663 @item @code{get-thread-local-@*storage-address}
18664 @tab @code{qGetTLSAddr}
18665 @tab Displaying @code{__thread} variables
18667 @item @code{get-thread-information-block-address}
18668 @tab @code{qGetTIBAddr}
18669 @tab Display MS-Windows Thread Information Block.
18671 @item @code{search-memory}
18672 @tab @code{qSearch:memory}
18675 @item @code{supported-packets}
18676 @tab @code{qSupported}
18677 @tab Remote communications parameters
18679 @item @code{pass-signals}
18680 @tab @code{QPassSignals}
18681 @tab @code{handle @var{signal}}
18683 @item @code{program-signals}
18684 @tab @code{QProgramSignals}
18685 @tab @code{handle @var{signal}}
18687 @item @code{hostio-close-packet}
18688 @tab @code{vFile:close}
18689 @tab @code{remote get}, @code{remote put}
18691 @item @code{hostio-open-packet}
18692 @tab @code{vFile:open}
18693 @tab @code{remote get}, @code{remote put}
18695 @item @code{hostio-pread-packet}
18696 @tab @code{vFile:pread}
18697 @tab @code{remote get}, @code{remote put}
18699 @item @code{hostio-pwrite-packet}
18700 @tab @code{vFile:pwrite}
18701 @tab @code{remote get}, @code{remote put}
18703 @item @code{hostio-unlink-packet}
18704 @tab @code{vFile:unlink}
18705 @tab @code{remote delete}
18707 @item @code{hostio-readlink-packet}
18708 @tab @code{vFile:readlink}
18711 @item @code{noack-packet}
18712 @tab @code{QStartNoAckMode}
18713 @tab Packet acknowledgment
18715 @item @code{osdata}
18716 @tab @code{qXfer:osdata:read}
18717 @tab @code{info os}
18719 @item @code{query-attached}
18720 @tab @code{qAttached}
18721 @tab Querying remote process attach state.
18723 @item @code{trace-buffer-size}
18724 @tab @code{QTBuffer:size}
18725 @tab @code{set trace-buffer-size}
18727 @item @code{trace-status}
18728 @tab @code{qTStatus}
18729 @tab @code{tstatus}
18731 @item @code{traceframe-info}
18732 @tab @code{qXfer:traceframe-info:read}
18733 @tab Traceframe info
18735 @item @code{install-in-trace}
18736 @tab @code{InstallInTrace}
18737 @tab Install tracepoint in tracing
18739 @item @code{disable-randomization}
18740 @tab @code{QDisableRandomization}
18741 @tab @code{set disable-randomization}
18743 @item @code{conditional-breakpoints-packet}
18744 @tab @code{Z0 and Z1}
18745 @tab @code{Support for target-side breakpoint condition evaluation}
18749 @section Implementing a Remote Stub
18751 @cindex debugging stub, example
18752 @cindex remote stub, example
18753 @cindex stub example, remote debugging
18754 The stub files provided with @value{GDBN} implement the target side of the
18755 communication protocol, and the @value{GDBN} side is implemented in the
18756 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18757 these subroutines to communicate, and ignore the details. (If you're
18758 implementing your own stub file, you can still ignore the details: start
18759 with one of the existing stub files. @file{sparc-stub.c} is the best
18760 organized, and therefore the easiest to read.)
18762 @cindex remote serial debugging, overview
18763 To debug a program running on another machine (the debugging
18764 @dfn{target} machine), you must first arrange for all the usual
18765 prerequisites for the program to run by itself. For example, for a C
18770 A startup routine to set up the C runtime environment; these usually
18771 have a name like @file{crt0}. The startup routine may be supplied by
18772 your hardware supplier, or you may have to write your own.
18775 A C subroutine library to support your program's
18776 subroutine calls, notably managing input and output.
18779 A way of getting your program to the other machine---for example, a
18780 download program. These are often supplied by the hardware
18781 manufacturer, but you may have to write your own from hardware
18785 The next step is to arrange for your program to use a serial port to
18786 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18787 machine). In general terms, the scheme looks like this:
18791 @value{GDBN} already understands how to use this protocol; when everything
18792 else is set up, you can simply use the @samp{target remote} command
18793 (@pxref{Targets,,Specifying a Debugging Target}).
18795 @item On the target,
18796 you must link with your program a few special-purpose subroutines that
18797 implement the @value{GDBN} remote serial protocol. The file containing these
18798 subroutines is called a @dfn{debugging stub}.
18800 On certain remote targets, you can use an auxiliary program
18801 @code{gdbserver} instead of linking a stub into your program.
18802 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18805 The debugging stub is specific to the architecture of the remote
18806 machine; for example, use @file{sparc-stub.c} to debug programs on
18809 @cindex remote serial stub list
18810 These working remote stubs are distributed with @value{GDBN}:
18815 @cindex @file{i386-stub.c}
18818 For Intel 386 and compatible architectures.
18821 @cindex @file{m68k-stub.c}
18822 @cindex Motorola 680x0
18824 For Motorola 680x0 architectures.
18827 @cindex @file{sh-stub.c}
18830 For Renesas SH architectures.
18833 @cindex @file{sparc-stub.c}
18835 For @sc{sparc} architectures.
18837 @item sparcl-stub.c
18838 @cindex @file{sparcl-stub.c}
18841 For Fujitsu @sc{sparclite} architectures.
18845 The @file{README} file in the @value{GDBN} distribution may list other
18846 recently added stubs.
18849 * Stub Contents:: What the stub can do for you
18850 * Bootstrapping:: What you must do for the stub
18851 * Debug Session:: Putting it all together
18854 @node Stub Contents
18855 @subsection What the Stub Can Do for You
18857 @cindex remote serial stub
18858 The debugging stub for your architecture supplies these three
18862 @item set_debug_traps
18863 @findex set_debug_traps
18864 @cindex remote serial stub, initialization
18865 This routine arranges for @code{handle_exception} to run when your
18866 program stops. You must call this subroutine explicitly in your
18867 program's startup code.
18869 @item handle_exception
18870 @findex handle_exception
18871 @cindex remote serial stub, main routine
18872 This is the central workhorse, but your program never calls it
18873 explicitly---the setup code arranges for @code{handle_exception} to
18874 run when a trap is triggered.
18876 @code{handle_exception} takes control when your program stops during
18877 execution (for example, on a breakpoint), and mediates communications
18878 with @value{GDBN} on the host machine. This is where the communications
18879 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18880 representative on the target machine. It begins by sending summary
18881 information on the state of your program, then continues to execute,
18882 retrieving and transmitting any information @value{GDBN} needs, until you
18883 execute a @value{GDBN} command that makes your program resume; at that point,
18884 @code{handle_exception} returns control to your own code on the target
18888 @cindex @code{breakpoint} subroutine, remote
18889 Use this auxiliary subroutine to make your program contain a
18890 breakpoint. Depending on the particular situation, this may be the only
18891 way for @value{GDBN} to get control. For instance, if your target
18892 machine has some sort of interrupt button, you won't need to call this;
18893 pressing the interrupt button transfers control to
18894 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18895 simply receiving characters on the serial port may also trigger a trap;
18896 again, in that situation, you don't need to call @code{breakpoint} from
18897 your own program---simply running @samp{target remote} from the host
18898 @value{GDBN} session gets control.
18900 Call @code{breakpoint} if none of these is true, or if you simply want
18901 to make certain your program stops at a predetermined point for the
18902 start of your debugging session.
18905 @node Bootstrapping
18906 @subsection What You Must Do for the Stub
18908 @cindex remote stub, support routines
18909 The debugging stubs that come with @value{GDBN} are set up for a particular
18910 chip architecture, but they have no information about the rest of your
18911 debugging target machine.
18913 First of all you need to tell the stub how to communicate with the
18917 @item int getDebugChar()
18918 @findex getDebugChar
18919 Write this subroutine to read a single character from the serial port.
18920 It may be identical to @code{getchar} for your target system; a
18921 different name is used to allow you to distinguish the two if you wish.
18923 @item void putDebugChar(int)
18924 @findex putDebugChar
18925 Write this subroutine to write a single character to the serial port.
18926 It may be identical to @code{putchar} for your target system; a
18927 different name is used to allow you to distinguish the two if you wish.
18930 @cindex control C, and remote debugging
18931 @cindex interrupting remote targets
18932 If you want @value{GDBN} to be able to stop your program while it is
18933 running, you need to use an interrupt-driven serial driver, and arrange
18934 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18935 character). That is the character which @value{GDBN} uses to tell the
18936 remote system to stop.
18938 Getting the debugging target to return the proper status to @value{GDBN}
18939 probably requires changes to the standard stub; one quick and dirty way
18940 is to just execute a breakpoint instruction (the ``dirty'' part is that
18941 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18943 Other routines you need to supply are:
18946 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18947 @findex exceptionHandler
18948 Write this function to install @var{exception_address} in the exception
18949 handling tables. You need to do this because the stub does not have any
18950 way of knowing what the exception handling tables on your target system
18951 are like (for example, the processor's table might be in @sc{rom},
18952 containing entries which point to a table in @sc{ram}).
18953 @var{exception_number} is the exception number which should be changed;
18954 its meaning is architecture-dependent (for example, different numbers
18955 might represent divide by zero, misaligned access, etc). When this
18956 exception occurs, control should be transferred directly to
18957 @var{exception_address}, and the processor state (stack, registers,
18958 and so on) should be just as it is when a processor exception occurs. So if
18959 you want to use a jump instruction to reach @var{exception_address}, it
18960 should be a simple jump, not a jump to subroutine.
18962 For the 386, @var{exception_address} should be installed as an interrupt
18963 gate so that interrupts are masked while the handler runs. The gate
18964 should be at privilege level 0 (the most privileged level). The
18965 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18966 help from @code{exceptionHandler}.
18968 @item void flush_i_cache()
18969 @findex flush_i_cache
18970 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18971 instruction cache, if any, on your target machine. If there is no
18972 instruction cache, this subroutine may be a no-op.
18974 On target machines that have instruction caches, @value{GDBN} requires this
18975 function to make certain that the state of your program is stable.
18979 You must also make sure this library routine is available:
18982 @item void *memset(void *, int, int)
18984 This is the standard library function @code{memset} that sets an area of
18985 memory to a known value. If you have one of the free versions of
18986 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18987 either obtain it from your hardware manufacturer, or write your own.
18990 If you do not use the GNU C compiler, you may need other standard
18991 library subroutines as well; this varies from one stub to another,
18992 but in general the stubs are likely to use any of the common library
18993 subroutines which @code{@value{NGCC}} generates as inline code.
18996 @node Debug Session
18997 @subsection Putting it All Together
18999 @cindex remote serial debugging summary
19000 In summary, when your program is ready to debug, you must follow these
19005 Make sure you have defined the supporting low-level routines
19006 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
19008 @code{getDebugChar}, @code{putDebugChar},
19009 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
19013 Insert these lines in your program's startup code, before the main
19014 procedure is called:
19021 On some machines, when a breakpoint trap is raised, the hardware
19022 automatically makes the PC point to the instruction after the
19023 breakpoint. If your machine doesn't do that, you may need to adjust
19024 @code{handle_exception} to arrange for it to return to the instruction
19025 after the breakpoint on this first invocation, so that your program
19026 doesn't keep hitting the initial breakpoint instead of making
19030 For the 680x0 stub only, you need to provide a variable called
19031 @code{exceptionHook}. Normally you just use:
19034 void (*exceptionHook)() = 0;
19038 but if before calling @code{set_debug_traps}, you set it to point to a
19039 function in your program, that function is called when
19040 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
19041 error). The function indicated by @code{exceptionHook} is called with
19042 one parameter: an @code{int} which is the exception number.
19045 Compile and link together: your program, the @value{GDBN} debugging stub for
19046 your target architecture, and the supporting subroutines.
19049 Make sure you have a serial connection between your target machine and
19050 the @value{GDBN} host, and identify the serial port on the host.
19053 @c The "remote" target now provides a `load' command, so we should
19054 @c document that. FIXME.
19055 Download your program to your target machine (or get it there by
19056 whatever means the manufacturer provides), and start it.
19059 Start @value{GDBN} on the host, and connect to the target
19060 (@pxref{Connecting,,Connecting to a Remote Target}).
19064 @node Configurations
19065 @chapter Configuration-Specific Information
19067 While nearly all @value{GDBN} commands are available for all native and
19068 cross versions of the debugger, there are some exceptions. This chapter
19069 describes things that are only available in certain configurations.
19071 There are three major categories of configurations: native
19072 configurations, where the host and target are the same, embedded
19073 operating system configurations, which are usually the same for several
19074 different processor architectures, and bare embedded processors, which
19075 are quite different from each other.
19080 * Embedded Processors::
19087 This section describes details specific to particular native
19092 * BSD libkvm Interface:: Debugging BSD kernel memory images
19093 * SVR4 Process Information:: SVR4 process information
19094 * DJGPP Native:: Features specific to the DJGPP port
19095 * Cygwin Native:: Features specific to the Cygwin port
19096 * Hurd Native:: Features specific to @sc{gnu} Hurd
19097 * Darwin:: Features specific to Darwin
19103 On HP-UX systems, if you refer to a function or variable name that
19104 begins with a dollar sign, @value{GDBN} searches for a user or system
19105 name first, before it searches for a convenience variable.
19108 @node BSD libkvm Interface
19109 @subsection BSD libkvm Interface
19112 @cindex kernel memory image
19113 @cindex kernel crash dump
19115 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
19116 interface that provides a uniform interface for accessing kernel virtual
19117 memory images, including live systems and crash dumps. @value{GDBN}
19118 uses this interface to allow you to debug live kernels and kernel crash
19119 dumps on many native BSD configurations. This is implemented as a
19120 special @code{kvm} debugging target. For debugging a live system, load
19121 the currently running kernel into @value{GDBN} and connect to the
19125 (@value{GDBP}) @b{target kvm}
19128 For debugging crash dumps, provide the file name of the crash dump as an
19132 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
19135 Once connected to the @code{kvm} target, the following commands are
19141 Set current context from the @dfn{Process Control Block} (PCB) address.
19144 Set current context from proc address. This command isn't available on
19145 modern FreeBSD systems.
19148 @node SVR4 Process Information
19149 @subsection SVR4 Process Information
19151 @cindex examine process image
19152 @cindex process info via @file{/proc}
19154 Many versions of SVR4 and compatible systems provide a facility called
19155 @samp{/proc} that can be used to examine the image of a running
19156 process using file-system subroutines.
19158 If @value{GDBN} is configured for an operating system with this
19159 facility, the command @code{info proc} is available to report
19160 information about the process running your program, or about any
19161 process running on your system. This includes, as of this writing,
19162 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
19163 not HP-UX, for example.
19165 This command may also work on core files that were created on a system
19166 that has the @samp{/proc} facility.
19172 @itemx info proc @var{process-id}
19173 Summarize available information about any running process. If a
19174 process ID is specified by @var{process-id}, display information about
19175 that process; otherwise display information about the program being
19176 debugged. The summary includes the debugged process ID, the command
19177 line used to invoke it, its current working directory, and its
19178 executable file's absolute file name.
19180 On some systems, @var{process-id} can be of the form
19181 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
19182 within a process. If the optional @var{pid} part is missing, it means
19183 a thread from the process being debugged (the leading @samp{/} still
19184 needs to be present, or else @value{GDBN} will interpret the number as
19185 a process ID rather than a thread ID).
19187 @item info proc cmdline
19188 @cindex info proc cmdline
19189 Show the original command line of the process. This command is
19190 specific to @sc{gnu}/Linux.
19192 @item info proc cwd
19193 @cindex info proc cwd
19194 Show the current working directory of the process. This command is
19195 specific to @sc{gnu}/Linux.
19197 @item info proc exe
19198 @cindex info proc exe
19199 Show the name of executable of the process. This command is specific
19202 @item info proc mappings
19203 @cindex memory address space mappings
19204 Report the memory address space ranges accessible in the program, with
19205 information on whether the process has read, write, or execute access
19206 rights to each range. On @sc{gnu}/Linux systems, each memory range
19207 includes the object file which is mapped to that range, instead of the
19208 memory access rights to that range.
19210 @item info proc stat
19211 @itemx info proc status
19212 @cindex process detailed status information
19213 These subcommands are specific to @sc{gnu}/Linux systems. They show
19214 the process-related information, including the user ID and group ID;
19215 how many threads are there in the process; its virtual memory usage;
19216 the signals that are pending, blocked, and ignored; its TTY; its
19217 consumption of system and user time; its stack size; its @samp{nice}
19218 value; etc. For more information, see the @samp{proc} man page
19219 (type @kbd{man 5 proc} from your shell prompt).
19221 @item info proc all
19222 Show all the information about the process described under all of the
19223 above @code{info proc} subcommands.
19226 @comment These sub-options of 'info proc' were not included when
19227 @comment procfs.c was re-written. Keep their descriptions around
19228 @comment against the day when someone finds the time to put them back in.
19229 @kindex info proc times
19230 @item info proc times
19231 Starting time, user CPU time, and system CPU time for your program and
19234 @kindex info proc id
19236 Report on the process IDs related to your program: its own process ID,
19237 the ID of its parent, the process group ID, and the session ID.
19240 @item set procfs-trace
19241 @kindex set procfs-trace
19242 @cindex @code{procfs} API calls
19243 This command enables and disables tracing of @code{procfs} API calls.
19245 @item show procfs-trace
19246 @kindex show procfs-trace
19247 Show the current state of @code{procfs} API call tracing.
19249 @item set procfs-file @var{file}
19250 @kindex set procfs-file
19251 Tell @value{GDBN} to write @code{procfs} API trace to the named
19252 @var{file}. @value{GDBN} appends the trace info to the previous
19253 contents of the file. The default is to display the trace on the
19256 @item show procfs-file
19257 @kindex show procfs-file
19258 Show the file to which @code{procfs} API trace is written.
19260 @item proc-trace-entry
19261 @itemx proc-trace-exit
19262 @itemx proc-untrace-entry
19263 @itemx proc-untrace-exit
19264 @kindex proc-trace-entry
19265 @kindex proc-trace-exit
19266 @kindex proc-untrace-entry
19267 @kindex proc-untrace-exit
19268 These commands enable and disable tracing of entries into and exits
19269 from the @code{syscall} interface.
19272 @kindex info pidlist
19273 @cindex process list, QNX Neutrino
19274 For QNX Neutrino only, this command displays the list of all the
19275 processes and all the threads within each process.
19278 @kindex info meminfo
19279 @cindex mapinfo list, QNX Neutrino
19280 For QNX Neutrino only, this command displays the list of all mapinfos.
19284 @subsection Features for Debugging @sc{djgpp} Programs
19285 @cindex @sc{djgpp} debugging
19286 @cindex native @sc{djgpp} debugging
19287 @cindex MS-DOS-specific commands
19290 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19291 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19292 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19293 top of real-mode DOS systems and their emulations.
19295 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19296 defines a few commands specific to the @sc{djgpp} port. This
19297 subsection describes those commands.
19302 This is a prefix of @sc{djgpp}-specific commands which print
19303 information about the target system and important OS structures.
19306 @cindex MS-DOS system info
19307 @cindex free memory information (MS-DOS)
19308 @item info dos sysinfo
19309 This command displays assorted information about the underlying
19310 platform: the CPU type and features, the OS version and flavor, the
19311 DPMI version, and the available conventional and DPMI memory.
19316 @cindex segment descriptor tables
19317 @cindex descriptor tables display
19319 @itemx info dos ldt
19320 @itemx info dos idt
19321 These 3 commands display entries from, respectively, Global, Local,
19322 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19323 tables are data structures which store a descriptor for each segment
19324 that is currently in use. The segment's selector is an index into a
19325 descriptor table; the table entry for that index holds the
19326 descriptor's base address and limit, and its attributes and access
19329 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19330 segment (used for both data and the stack), and a DOS segment (which
19331 allows access to DOS/BIOS data structures and absolute addresses in
19332 conventional memory). However, the DPMI host will usually define
19333 additional segments in order to support the DPMI environment.
19335 @cindex garbled pointers
19336 These commands allow to display entries from the descriptor tables.
19337 Without an argument, all entries from the specified table are
19338 displayed. An argument, which should be an integer expression, means
19339 display a single entry whose index is given by the argument. For
19340 example, here's a convenient way to display information about the
19341 debugged program's data segment:
19344 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19345 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19349 This comes in handy when you want to see whether a pointer is outside
19350 the data segment's limit (i.e.@: @dfn{garbled}).
19352 @cindex page tables display (MS-DOS)
19354 @itemx info dos pte
19355 These two commands display entries from, respectively, the Page
19356 Directory and the Page Tables. Page Directories and Page Tables are
19357 data structures which control how virtual memory addresses are mapped
19358 into physical addresses. A Page Table includes an entry for every
19359 page of memory that is mapped into the program's address space; there
19360 may be several Page Tables, each one holding up to 4096 entries. A
19361 Page Directory has up to 4096 entries, one each for every Page Table
19362 that is currently in use.
19364 Without an argument, @kbd{info dos pde} displays the entire Page
19365 Directory, and @kbd{info dos pte} displays all the entries in all of
19366 the Page Tables. An argument, an integer expression, given to the
19367 @kbd{info dos pde} command means display only that entry from the Page
19368 Directory table. An argument given to the @kbd{info dos pte} command
19369 means display entries from a single Page Table, the one pointed to by
19370 the specified entry in the Page Directory.
19372 @cindex direct memory access (DMA) on MS-DOS
19373 These commands are useful when your program uses @dfn{DMA} (Direct
19374 Memory Access), which needs physical addresses to program the DMA
19377 These commands are supported only with some DPMI servers.
19379 @cindex physical address from linear address
19380 @item info dos address-pte @var{addr}
19381 This command displays the Page Table entry for a specified linear
19382 address. The argument @var{addr} is a linear address which should
19383 already have the appropriate segment's base address added to it,
19384 because this command accepts addresses which may belong to @emph{any}
19385 segment. For example, here's how to display the Page Table entry for
19386 the page where a variable @code{i} is stored:
19389 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19390 @exdent @code{Page Table entry for address 0x11a00d30:}
19391 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19395 This says that @code{i} is stored at offset @code{0xd30} from the page
19396 whose physical base address is @code{0x02698000}, and shows all the
19397 attributes of that page.
19399 Note that you must cast the addresses of variables to a @code{char *},
19400 since otherwise the value of @code{__djgpp_base_address}, the base
19401 address of all variables and functions in a @sc{djgpp} program, will
19402 be added using the rules of C pointer arithmetics: if @code{i} is
19403 declared an @code{int}, @value{GDBN} will add 4 times the value of
19404 @code{__djgpp_base_address} to the address of @code{i}.
19406 Here's another example, it displays the Page Table entry for the
19410 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19411 @exdent @code{Page Table entry for address 0x29110:}
19412 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19416 (The @code{+ 3} offset is because the transfer buffer's address is the
19417 3rd member of the @code{_go32_info_block} structure.) The output
19418 clearly shows that this DPMI server maps the addresses in conventional
19419 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19420 linear (@code{0x29110}) addresses are identical.
19422 This command is supported only with some DPMI servers.
19425 @cindex DOS serial data link, remote debugging
19426 In addition to native debugging, the DJGPP port supports remote
19427 debugging via a serial data link. The following commands are specific
19428 to remote serial debugging in the DJGPP port of @value{GDBN}.
19431 @kindex set com1base
19432 @kindex set com1irq
19433 @kindex set com2base
19434 @kindex set com2irq
19435 @kindex set com3base
19436 @kindex set com3irq
19437 @kindex set com4base
19438 @kindex set com4irq
19439 @item set com1base @var{addr}
19440 This command sets the base I/O port address of the @file{COM1} serial
19443 @item set com1irq @var{irq}
19444 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19445 for the @file{COM1} serial port.
19447 There are similar commands @samp{set com2base}, @samp{set com3irq},
19448 etc.@: for setting the port address and the @code{IRQ} lines for the
19451 @kindex show com1base
19452 @kindex show com1irq
19453 @kindex show com2base
19454 @kindex show com2irq
19455 @kindex show com3base
19456 @kindex show com3irq
19457 @kindex show com4base
19458 @kindex show com4irq
19459 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19460 display the current settings of the base address and the @code{IRQ}
19461 lines used by the COM ports.
19464 @kindex info serial
19465 @cindex DOS serial port status
19466 This command prints the status of the 4 DOS serial ports. For each
19467 port, it prints whether it's active or not, its I/O base address and
19468 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19469 counts of various errors encountered so far.
19473 @node Cygwin Native
19474 @subsection Features for Debugging MS Windows PE Executables
19475 @cindex MS Windows debugging
19476 @cindex native Cygwin debugging
19477 @cindex Cygwin-specific commands
19479 @value{GDBN} supports native debugging of MS Windows programs, including
19480 DLLs with and without symbolic debugging information.
19482 @cindex Ctrl-BREAK, MS-Windows
19483 @cindex interrupt debuggee on MS-Windows
19484 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19485 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19486 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19487 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19488 sequence, which can be used to interrupt the debuggee even if it
19491 There are various additional Cygwin-specific commands, described in
19492 this section. Working with DLLs that have no debugging symbols is
19493 described in @ref{Non-debug DLL Symbols}.
19498 This is a prefix of MS Windows-specific commands which print
19499 information about the target system and important OS structures.
19501 @item info w32 selector
19502 This command displays information returned by
19503 the Win32 API @code{GetThreadSelectorEntry} function.
19504 It takes an optional argument that is evaluated to
19505 a long value to give the information about this given selector.
19506 Without argument, this command displays information
19507 about the six segment registers.
19509 @item info w32 thread-information-block
19510 This command displays thread specific information stored in the
19511 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19512 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19516 This is a Cygwin-specific alias of @code{info shared}.
19518 @kindex dll-symbols
19520 This command loads symbols from a dll similarly to
19521 add-sym command but without the need to specify a base address.
19523 @kindex set cygwin-exceptions
19524 @cindex debugging the Cygwin DLL
19525 @cindex Cygwin DLL, debugging
19526 @item set cygwin-exceptions @var{mode}
19527 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19528 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19529 @value{GDBN} will delay recognition of exceptions, and may ignore some
19530 exceptions which seem to be caused by internal Cygwin DLL
19531 ``bookkeeping''. This option is meant primarily for debugging the
19532 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19533 @value{GDBN} users with false @code{SIGSEGV} signals.
19535 @kindex show cygwin-exceptions
19536 @item show cygwin-exceptions
19537 Displays whether @value{GDBN} will break on exceptions that happen
19538 inside the Cygwin DLL itself.
19540 @kindex set new-console
19541 @item set new-console @var{mode}
19542 If @var{mode} is @code{on} the debuggee will
19543 be started in a new console on next start.
19544 If @var{mode} is @code{off}, the debuggee will
19545 be started in the same console as the debugger.
19547 @kindex show new-console
19548 @item show new-console
19549 Displays whether a new console is used
19550 when the debuggee is started.
19552 @kindex set new-group
19553 @item set new-group @var{mode}
19554 This boolean value controls whether the debuggee should
19555 start a new group or stay in the same group as the debugger.
19556 This affects the way the Windows OS handles
19559 @kindex show new-group
19560 @item show new-group
19561 Displays current value of new-group boolean.
19563 @kindex set debugevents
19564 @item set debugevents
19565 This boolean value adds debug output concerning kernel events related
19566 to the debuggee seen by the debugger. This includes events that
19567 signal thread and process creation and exit, DLL loading and
19568 unloading, console interrupts, and debugging messages produced by the
19569 Windows @code{OutputDebugString} API call.
19571 @kindex set debugexec
19572 @item set debugexec
19573 This boolean value adds debug output concerning execute events
19574 (such as resume thread) seen by the debugger.
19576 @kindex set debugexceptions
19577 @item set debugexceptions
19578 This boolean value adds debug output concerning exceptions in the
19579 debuggee seen by the debugger.
19581 @kindex set debugmemory
19582 @item set debugmemory
19583 This boolean value adds debug output concerning debuggee memory reads
19584 and writes by the debugger.
19588 This boolean values specifies whether the debuggee is called
19589 via a shell or directly (default value is on).
19593 Displays if the debuggee will be started with a shell.
19598 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19601 @node Non-debug DLL Symbols
19602 @subsubsection Support for DLLs without Debugging Symbols
19603 @cindex DLLs with no debugging symbols
19604 @cindex Minimal symbols and DLLs
19606 Very often on windows, some of the DLLs that your program relies on do
19607 not include symbolic debugging information (for example,
19608 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19609 symbols in a DLL, it relies on the minimal amount of symbolic
19610 information contained in the DLL's export table. This section
19611 describes working with such symbols, known internally to @value{GDBN} as
19612 ``minimal symbols''.
19614 Note that before the debugged program has started execution, no DLLs
19615 will have been loaded. The easiest way around this problem is simply to
19616 start the program --- either by setting a breakpoint or letting the
19617 program run once to completion. It is also possible to force
19618 @value{GDBN} to load a particular DLL before starting the executable ---
19619 see the shared library information in @ref{Files}, or the
19620 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19621 explicitly loading symbols from a DLL with no debugging information will
19622 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19623 which may adversely affect symbol lookup performance.
19625 @subsubsection DLL Name Prefixes
19627 In keeping with the naming conventions used by the Microsoft debugging
19628 tools, DLL export symbols are made available with a prefix based on the
19629 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19630 also entered into the symbol table, so @code{CreateFileA} is often
19631 sufficient. In some cases there will be name clashes within a program
19632 (particularly if the executable itself includes full debugging symbols)
19633 necessitating the use of the fully qualified name when referring to the
19634 contents of the DLL. Use single-quotes around the name to avoid the
19635 exclamation mark (``!'') being interpreted as a language operator.
19637 Note that the internal name of the DLL may be all upper-case, even
19638 though the file name of the DLL is lower-case, or vice-versa. Since
19639 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19640 some confusion. If in doubt, try the @code{info functions} and
19641 @code{info variables} commands or even @code{maint print msymbols}
19642 (@pxref{Symbols}). Here's an example:
19645 (@value{GDBP}) info function CreateFileA
19646 All functions matching regular expression "CreateFileA":
19648 Non-debugging symbols:
19649 0x77e885f4 CreateFileA
19650 0x77e885f4 KERNEL32!CreateFileA
19654 (@value{GDBP}) info function !
19655 All functions matching regular expression "!":
19657 Non-debugging symbols:
19658 0x6100114c cygwin1!__assert
19659 0x61004034 cygwin1!_dll_crt0@@0
19660 0x61004240 cygwin1!dll_crt0(per_process *)
19664 @subsubsection Working with Minimal Symbols
19666 Symbols extracted from a DLL's export table do not contain very much
19667 type information. All that @value{GDBN} can do is guess whether a symbol
19668 refers to a function or variable depending on the linker section that
19669 contains the symbol. Also note that the actual contents of the memory
19670 contained in a DLL are not available unless the program is running. This
19671 means that you cannot examine the contents of a variable or disassemble
19672 a function within a DLL without a running program.
19674 Variables are generally treated as pointers and dereferenced
19675 automatically. For this reason, it is often necessary to prefix a
19676 variable name with the address-of operator (``&'') and provide explicit
19677 type information in the command. Here's an example of the type of
19681 (@value{GDBP}) print 'cygwin1!__argv'
19686 (@value{GDBP}) x 'cygwin1!__argv'
19687 0x10021610: "\230y\""
19690 And two possible solutions:
19693 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19694 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19698 (@value{GDBP}) x/2x &'cygwin1!__argv'
19699 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19700 (@value{GDBP}) x/x 0x10021608
19701 0x10021608: 0x0022fd98
19702 (@value{GDBP}) x/s 0x0022fd98
19703 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19706 Setting a break point within a DLL is possible even before the program
19707 starts execution. However, under these circumstances, @value{GDBN} can't
19708 examine the initial instructions of the function in order to skip the
19709 function's frame set-up code. You can work around this by using ``*&''
19710 to set the breakpoint at a raw memory address:
19713 (@value{GDBP}) break *&'python22!PyOS_Readline'
19714 Breakpoint 1 at 0x1e04eff0
19717 The author of these extensions is not entirely convinced that setting a
19718 break point within a shared DLL like @file{kernel32.dll} is completely
19722 @subsection Commands Specific to @sc{gnu} Hurd Systems
19723 @cindex @sc{gnu} Hurd debugging
19725 This subsection describes @value{GDBN} commands specific to the
19726 @sc{gnu} Hurd native debugging.
19731 @kindex set signals@r{, Hurd command}
19732 @kindex set sigs@r{, Hurd command}
19733 This command toggles the state of inferior signal interception by
19734 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19735 affected by this command. @code{sigs} is a shorthand alias for
19740 @kindex show signals@r{, Hurd command}
19741 @kindex show sigs@r{, Hurd command}
19742 Show the current state of intercepting inferior's signals.
19744 @item set signal-thread
19745 @itemx set sigthread
19746 @kindex set signal-thread
19747 @kindex set sigthread
19748 This command tells @value{GDBN} which thread is the @code{libc} signal
19749 thread. That thread is run when a signal is delivered to a running
19750 process. @code{set sigthread} is the shorthand alias of @code{set
19753 @item show signal-thread
19754 @itemx show sigthread
19755 @kindex show signal-thread
19756 @kindex show sigthread
19757 These two commands show which thread will run when the inferior is
19758 delivered a signal.
19761 @kindex set stopped@r{, Hurd command}
19762 This commands tells @value{GDBN} that the inferior process is stopped,
19763 as with the @code{SIGSTOP} signal. The stopped process can be
19764 continued by delivering a signal to it.
19767 @kindex show stopped@r{, Hurd command}
19768 This command shows whether @value{GDBN} thinks the debuggee is
19771 @item set exceptions
19772 @kindex set exceptions@r{, Hurd command}
19773 Use this command to turn off trapping of exceptions in the inferior.
19774 When exception trapping is off, neither breakpoints nor
19775 single-stepping will work. To restore the default, set exception
19778 @item show exceptions
19779 @kindex show exceptions@r{, Hurd command}
19780 Show the current state of trapping exceptions in the inferior.
19782 @item set task pause
19783 @kindex set task@r{, Hurd commands}
19784 @cindex task attributes (@sc{gnu} Hurd)
19785 @cindex pause current task (@sc{gnu} Hurd)
19786 This command toggles task suspension when @value{GDBN} has control.
19787 Setting it to on takes effect immediately, and the task is suspended
19788 whenever @value{GDBN} gets control. Setting it to off will take
19789 effect the next time the inferior is continued. If this option is set
19790 to off, you can use @code{set thread default pause on} or @code{set
19791 thread pause on} (see below) to pause individual threads.
19793 @item show task pause
19794 @kindex show task@r{, Hurd commands}
19795 Show the current state of task suspension.
19797 @item set task detach-suspend-count
19798 @cindex task suspend count
19799 @cindex detach from task, @sc{gnu} Hurd
19800 This command sets the suspend count the task will be left with when
19801 @value{GDBN} detaches from it.
19803 @item show task detach-suspend-count
19804 Show the suspend count the task will be left with when detaching.
19806 @item set task exception-port
19807 @itemx set task excp
19808 @cindex task exception port, @sc{gnu} Hurd
19809 This command sets the task exception port to which @value{GDBN} will
19810 forward exceptions. The argument should be the value of the @dfn{send
19811 rights} of the task. @code{set task excp} is a shorthand alias.
19813 @item set noninvasive
19814 @cindex noninvasive task options
19815 This command switches @value{GDBN} to a mode that is the least
19816 invasive as far as interfering with the inferior is concerned. This
19817 is the same as using @code{set task pause}, @code{set exceptions}, and
19818 @code{set signals} to values opposite to the defaults.
19820 @item info send-rights
19821 @itemx info receive-rights
19822 @itemx info port-rights
19823 @itemx info port-sets
19824 @itemx info dead-names
19827 @cindex send rights, @sc{gnu} Hurd
19828 @cindex receive rights, @sc{gnu} Hurd
19829 @cindex port rights, @sc{gnu} Hurd
19830 @cindex port sets, @sc{gnu} Hurd
19831 @cindex dead names, @sc{gnu} Hurd
19832 These commands display information about, respectively, send rights,
19833 receive rights, port rights, port sets, and dead names of a task.
19834 There are also shorthand aliases: @code{info ports} for @code{info
19835 port-rights} and @code{info psets} for @code{info port-sets}.
19837 @item set thread pause
19838 @kindex set thread@r{, Hurd command}
19839 @cindex thread properties, @sc{gnu} Hurd
19840 @cindex pause current thread (@sc{gnu} Hurd)
19841 This command toggles current thread suspension when @value{GDBN} has
19842 control. Setting it to on takes effect immediately, and the current
19843 thread is suspended whenever @value{GDBN} gets control. Setting it to
19844 off will take effect the next time the inferior is continued.
19845 Normally, this command has no effect, since when @value{GDBN} has
19846 control, the whole task is suspended. However, if you used @code{set
19847 task pause off} (see above), this command comes in handy to suspend
19848 only the current thread.
19850 @item show thread pause
19851 @kindex show thread@r{, Hurd command}
19852 This command shows the state of current thread suspension.
19854 @item set thread run
19855 This command sets whether the current thread is allowed to run.
19857 @item show thread run
19858 Show whether the current thread is allowed to run.
19860 @item set thread detach-suspend-count
19861 @cindex thread suspend count, @sc{gnu} Hurd
19862 @cindex detach from thread, @sc{gnu} Hurd
19863 This command sets the suspend count @value{GDBN} will leave on a
19864 thread when detaching. This number is relative to the suspend count
19865 found by @value{GDBN} when it notices the thread; use @code{set thread
19866 takeover-suspend-count} to force it to an absolute value.
19868 @item show thread detach-suspend-count
19869 Show the suspend count @value{GDBN} will leave on the thread when
19872 @item set thread exception-port
19873 @itemx set thread excp
19874 Set the thread exception port to which to forward exceptions. This
19875 overrides the port set by @code{set task exception-port} (see above).
19876 @code{set thread excp} is the shorthand alias.
19878 @item set thread takeover-suspend-count
19879 Normally, @value{GDBN}'s thread suspend counts are relative to the
19880 value @value{GDBN} finds when it notices each thread. This command
19881 changes the suspend counts to be absolute instead.
19883 @item set thread default
19884 @itemx show thread default
19885 @cindex thread default settings, @sc{gnu} Hurd
19886 Each of the above @code{set thread} commands has a @code{set thread
19887 default} counterpart (e.g., @code{set thread default pause}, @code{set
19888 thread default exception-port}, etc.). The @code{thread default}
19889 variety of commands sets the default thread properties for all
19890 threads; you can then change the properties of individual threads with
19891 the non-default commands.
19898 @value{GDBN} provides the following commands specific to the Darwin target:
19901 @item set debug darwin @var{num}
19902 @kindex set debug darwin
19903 When set to a non zero value, enables debugging messages specific to
19904 the Darwin support. Higher values produce more verbose output.
19906 @item show debug darwin
19907 @kindex show debug darwin
19908 Show the current state of Darwin messages.
19910 @item set debug mach-o @var{num}
19911 @kindex set debug mach-o
19912 When set to a non zero value, enables debugging messages while
19913 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19914 file format used on Darwin for object and executable files.) Higher
19915 values produce more verbose output. This is a command to diagnose
19916 problems internal to @value{GDBN} and should not be needed in normal
19919 @item show debug mach-o
19920 @kindex show debug mach-o
19921 Show the current state of Mach-O file messages.
19923 @item set mach-exceptions on
19924 @itemx set mach-exceptions off
19925 @kindex set mach-exceptions
19926 On Darwin, faults are first reported as a Mach exception and are then
19927 mapped to a Posix signal. Use this command to turn on trapping of
19928 Mach exceptions in the inferior. This might be sometimes useful to
19929 better understand the cause of a fault. The default is off.
19931 @item show mach-exceptions
19932 @kindex show mach-exceptions
19933 Show the current state of exceptions trapping.
19938 @section Embedded Operating Systems
19940 This section describes configurations involving the debugging of
19941 embedded operating systems that are available for several different
19945 * VxWorks:: Using @value{GDBN} with VxWorks
19948 @value{GDBN} includes the ability to debug programs running on
19949 various real-time operating systems.
19952 @subsection Using @value{GDBN} with VxWorks
19958 @kindex target vxworks
19959 @item target vxworks @var{machinename}
19960 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19961 is the target system's machine name or IP address.
19965 On VxWorks, @code{load} links @var{filename} dynamically on the
19966 current target system as well as adding its symbols in @value{GDBN}.
19968 @value{GDBN} enables developers to spawn and debug tasks running on networked
19969 VxWorks targets from a Unix host. Already-running tasks spawned from
19970 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19971 both the Unix host and on the VxWorks target. The program
19972 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19973 installed with the name @code{vxgdb}, to distinguish it from a
19974 @value{GDBN} for debugging programs on the host itself.)
19977 @item VxWorks-timeout @var{args}
19978 @kindex vxworks-timeout
19979 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19980 This option is set by the user, and @var{args} represents the number of
19981 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19982 your VxWorks target is a slow software simulator or is on the far side
19983 of a thin network line.
19986 The following information on connecting to VxWorks was current when
19987 this manual was produced; newer releases of VxWorks may use revised
19990 @findex INCLUDE_RDB
19991 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19992 to include the remote debugging interface routines in the VxWorks
19993 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19994 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19995 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19996 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19997 information on configuring and remaking VxWorks, see the manufacturer's
19999 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
20001 Once you have included @file{rdb.a} in your VxWorks system image and set
20002 your Unix execution search path to find @value{GDBN}, you are ready to
20003 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
20004 @code{vxgdb}, depending on your installation).
20006 @value{GDBN} comes up showing the prompt:
20013 * VxWorks Connection:: Connecting to VxWorks
20014 * VxWorks Download:: VxWorks download
20015 * VxWorks Attach:: Running tasks
20018 @node VxWorks Connection
20019 @subsubsection Connecting to VxWorks
20021 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
20022 network. To connect to a target whose host name is ``@code{tt}'', type:
20025 (vxgdb) target vxworks tt
20029 @value{GDBN} displays messages like these:
20032 Attaching remote machine across net...
20037 @value{GDBN} then attempts to read the symbol tables of any object modules
20038 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
20039 these files by searching the directories listed in the command search
20040 path (@pxref{Environment, ,Your Program's Environment}); if it fails
20041 to find an object file, it displays a message such as:
20044 prog.o: No such file or directory.
20047 When this happens, add the appropriate directory to the search path with
20048 the @value{GDBN} command @code{path}, and execute the @code{target}
20051 @node VxWorks Download
20052 @subsubsection VxWorks Download
20054 @cindex download to VxWorks
20055 If you have connected to the VxWorks target and you want to debug an
20056 object that has not yet been loaded, you can use the @value{GDBN}
20057 @code{load} command to download a file from Unix to VxWorks
20058 incrementally. The object file given as an argument to the @code{load}
20059 command is actually opened twice: first by the VxWorks target in order
20060 to download the code, then by @value{GDBN} in order to read the symbol
20061 table. This can lead to problems if the current working directories on
20062 the two systems differ. If both systems have NFS mounted the same
20063 filesystems, you can avoid these problems by using absolute paths.
20064 Otherwise, it is simplest to set the working directory on both systems
20065 to the directory in which the object file resides, and then to reference
20066 the file by its name, without any path. For instance, a program
20067 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
20068 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
20069 program, type this on VxWorks:
20072 -> cd "@var{vxpath}/vw/demo/rdb"
20076 Then, in @value{GDBN}, type:
20079 (vxgdb) cd @var{hostpath}/vw/demo/rdb
20080 (vxgdb) load prog.o
20083 @value{GDBN} displays a response similar to this:
20086 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
20089 You can also use the @code{load} command to reload an object module
20090 after editing and recompiling the corresponding source file. Note that
20091 this makes @value{GDBN} delete all currently-defined breakpoints,
20092 auto-displays, and convenience variables, and to clear the value
20093 history. (This is necessary in order to preserve the integrity of
20094 debugger's data structures that reference the target system's symbol
20097 @node VxWorks Attach
20098 @subsubsection Running Tasks
20100 @cindex running VxWorks tasks
20101 You can also attach to an existing task using the @code{attach} command as
20105 (vxgdb) attach @var{task}
20109 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
20110 or suspended when you attach to it. Running tasks are suspended at
20111 the time of attachment.
20113 @node Embedded Processors
20114 @section Embedded Processors
20116 This section goes into details specific to particular embedded
20119 @cindex send command to simulator
20120 Whenever a specific embedded processor has a simulator, @value{GDBN}
20121 allows to send an arbitrary command to the simulator.
20124 @item sim @var{command}
20125 @kindex sim@r{, a command}
20126 Send an arbitrary @var{command} string to the simulator. Consult the
20127 documentation for the specific simulator in use for information about
20128 acceptable commands.
20134 * M32R/D:: Renesas M32R/D
20135 * M68K:: Motorola M68K
20136 * MicroBlaze:: Xilinx MicroBlaze
20137 * MIPS Embedded:: MIPS Embedded
20138 * PowerPC Embedded:: PowerPC Embedded
20139 * PA:: HP PA Embedded
20140 * Sparclet:: Tsqware Sparclet
20141 * Sparclite:: Fujitsu Sparclite
20142 * Z8000:: Zilog Z8000
20145 * Super-H:: Renesas Super-H
20154 @item target rdi @var{dev}
20155 ARM Angel monitor, via RDI library interface to ADP protocol. You may
20156 use this target to communicate with both boards running the Angel
20157 monitor, or with the EmbeddedICE JTAG debug device.
20160 @item target rdp @var{dev}
20165 @value{GDBN} provides the following ARM-specific commands:
20168 @item set arm disassembler
20170 This commands selects from a list of disassembly styles. The
20171 @code{"std"} style is the standard style.
20173 @item show arm disassembler
20175 Show the current disassembly style.
20177 @item set arm apcs32
20178 @cindex ARM 32-bit mode
20179 This command toggles ARM operation mode between 32-bit and 26-bit.
20181 @item show arm apcs32
20182 Display the current usage of the ARM 32-bit mode.
20184 @item set arm fpu @var{fputype}
20185 This command sets the ARM floating-point unit (FPU) type. The
20186 argument @var{fputype} can be one of these:
20190 Determine the FPU type by querying the OS ABI.
20192 Software FPU, with mixed-endian doubles on little-endian ARM
20195 GCC-compiled FPA co-processor.
20197 Software FPU with pure-endian doubles.
20203 Show the current type of the FPU.
20206 This command forces @value{GDBN} to use the specified ABI.
20209 Show the currently used ABI.
20211 @item set arm fallback-mode (arm|thumb|auto)
20212 @value{GDBN} uses the symbol table, when available, to determine
20213 whether instructions are ARM or Thumb. This command controls
20214 @value{GDBN}'s default behavior when the symbol table is not
20215 available. The default is @samp{auto}, which causes @value{GDBN} to
20216 use the current execution mode (from the @code{T} bit in the @code{CPSR}
20219 @item show arm fallback-mode
20220 Show the current fallback instruction mode.
20222 @item set arm force-mode (arm|thumb|auto)
20223 This command overrides use of the symbol table to determine whether
20224 instructions are ARM or Thumb. The default is @samp{auto}, which
20225 causes @value{GDBN} to use the symbol table and then the setting
20226 of @samp{set arm fallback-mode}.
20228 @item show arm force-mode
20229 Show the current forced instruction mode.
20231 @item set debug arm
20232 Toggle whether to display ARM-specific debugging messages from the ARM
20233 target support subsystem.
20235 @item show debug arm
20236 Show whether ARM-specific debugging messages are enabled.
20239 The following commands are available when an ARM target is debugged
20240 using the RDI interface:
20243 @item rdilogfile @r{[}@var{file}@r{]}
20245 @cindex ADP (Angel Debugger Protocol) logging
20246 Set the filename for the ADP (Angel Debugger Protocol) packet log.
20247 With an argument, sets the log file to the specified @var{file}. With
20248 no argument, show the current log file name. The default log file is
20251 @item rdilogenable @r{[}@var{arg}@r{]}
20252 @kindex rdilogenable
20253 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
20254 enables logging, with an argument 0 or @code{"no"} disables it. With
20255 no arguments displays the current setting. When logging is enabled,
20256 ADP packets exchanged between @value{GDBN} and the RDI target device
20257 are logged to a file.
20259 @item set rdiromatzero
20260 @kindex set rdiromatzero
20261 @cindex ROM at zero address, RDI
20262 Tell @value{GDBN} whether the target has ROM at address 0. If on,
20263 vector catching is disabled, so that zero address can be used. If off
20264 (the default), vector catching is enabled. For this command to take
20265 effect, it needs to be invoked prior to the @code{target rdi} command.
20267 @item show rdiromatzero
20268 @kindex show rdiromatzero
20269 Show the current setting of ROM at zero address.
20271 @item set rdiheartbeat
20272 @kindex set rdiheartbeat
20273 @cindex RDI heartbeat
20274 Enable or disable RDI heartbeat packets. It is not recommended to
20275 turn on this option, since it confuses ARM and EPI JTAG interface, as
20276 well as the Angel monitor.
20278 @item show rdiheartbeat
20279 @kindex show rdiheartbeat
20280 Show the setting of RDI heartbeat packets.
20284 @item target sim @r{[}@var{simargs}@r{]} @dots{}
20285 The @value{GDBN} ARM simulator accepts the following optional arguments.
20288 @item --swi-support=@var{type}
20289 Tell the simulator which SWI interfaces to support.
20290 @var{type} may be a comma separated list of the following values.
20291 The default value is @code{all}.
20304 @subsection Renesas M32R/D and M32R/SDI
20307 @kindex target m32r
20308 @item target m32r @var{dev}
20309 Renesas M32R/D ROM monitor.
20311 @kindex target m32rsdi
20312 @item target m32rsdi @var{dev}
20313 Renesas M32R SDI server, connected via parallel port to the board.
20316 The following @value{GDBN} commands are specific to the M32R monitor:
20319 @item set download-path @var{path}
20320 @kindex set download-path
20321 @cindex find downloadable @sc{srec} files (M32R)
20322 Set the default path for finding downloadable @sc{srec} files.
20324 @item show download-path
20325 @kindex show download-path
20326 Show the default path for downloadable @sc{srec} files.
20328 @item set board-address @var{addr}
20329 @kindex set board-address
20330 @cindex M32-EVA target board address
20331 Set the IP address for the M32R-EVA target board.
20333 @item show board-address
20334 @kindex show board-address
20335 Show the current IP address of the target board.
20337 @item set server-address @var{addr}
20338 @kindex set server-address
20339 @cindex download server address (M32R)
20340 Set the IP address for the download server, which is the @value{GDBN}'s
20343 @item show server-address
20344 @kindex show server-address
20345 Display the IP address of the download server.
20347 @item upload @r{[}@var{file}@r{]}
20348 @kindex upload@r{, M32R}
20349 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20350 upload capability. If no @var{file} argument is given, the current
20351 executable file is uploaded.
20353 @item tload @r{[}@var{file}@r{]}
20354 @kindex tload@r{, M32R}
20355 Test the @code{upload} command.
20358 The following commands are available for M32R/SDI:
20363 @cindex reset SDI connection, M32R
20364 This command resets the SDI connection.
20368 This command shows the SDI connection status.
20371 @kindex debug_chaos
20372 @cindex M32R/Chaos debugging
20373 Instructs the remote that M32R/Chaos debugging is to be used.
20375 @item use_debug_dma
20376 @kindex use_debug_dma
20377 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20380 @kindex use_mon_code
20381 Instructs the remote to use the MON_CODE method of accessing memory.
20384 @kindex use_ib_break
20385 Instructs the remote to set breakpoints by IB break.
20387 @item use_dbt_break
20388 @kindex use_dbt_break
20389 Instructs the remote to set breakpoints by DBT.
20395 The Motorola m68k configuration includes ColdFire support, and a
20396 target command for the following ROM monitor.
20400 @kindex target dbug
20401 @item target dbug @var{dev}
20402 dBUG ROM monitor for Motorola ColdFire.
20407 @subsection MicroBlaze
20408 @cindex Xilinx MicroBlaze
20409 @cindex XMD, Xilinx Microprocessor Debugger
20411 The MicroBlaze is a soft-core processor supported on various Xilinx
20412 FPGAs, such as Spartan or Virtex series. Boards with these processors
20413 usually have JTAG ports which connect to a host system running the Xilinx
20414 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20415 This host system is used to download the configuration bitstream to
20416 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20417 communicates with the target board using the JTAG interface and
20418 presents a @code{gdbserver} interface to the board. By default
20419 @code{xmd} uses port @code{1234}. (While it is possible to change
20420 this default port, it requires the use of undocumented @code{xmd}
20421 commands. Contact Xilinx support if you need to do this.)
20423 Use these GDB commands to connect to the MicroBlaze target processor.
20426 @item target remote :1234
20427 Use this command to connect to the target if you are running @value{GDBN}
20428 on the same system as @code{xmd}.
20430 @item target remote @var{xmd-host}:1234
20431 Use this command to connect to the target if it is connected to @code{xmd}
20432 running on a different system named @var{xmd-host}.
20435 Use this command to download a program to the MicroBlaze target.
20437 @item set debug microblaze @var{n}
20438 Enable MicroBlaze-specific debugging messages if non-zero.
20440 @item show debug microblaze @var{n}
20441 Show MicroBlaze-specific debugging level.
20444 @node MIPS Embedded
20445 @subsection @acronym{MIPS} Embedded
20447 @cindex @acronym{MIPS} boards
20448 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20449 @acronym{MIPS} board attached to a serial line. This is available when
20450 you configure @value{GDBN} with @samp{--target=mips-elf}.
20453 Use these @value{GDBN} commands to specify the connection to your target board:
20456 @item target mips @var{port}
20457 @kindex target mips @var{port}
20458 To run a program on the board, start up @code{@value{GDBP}} with the
20459 name of your program as the argument. To connect to the board, use the
20460 command @samp{target mips @var{port}}, where @var{port} is the name of
20461 the serial port connected to the board. If the program has not already
20462 been downloaded to the board, you may use the @code{load} command to
20463 download it. You can then use all the usual @value{GDBN} commands.
20465 For example, this sequence connects to the target board through a serial
20466 port, and loads and runs a program called @var{prog} through the
20470 host$ @value{GDBP} @var{prog}
20471 @value{GDBN} is free software and @dots{}
20472 (@value{GDBP}) target mips /dev/ttyb
20473 (@value{GDBP}) load @var{prog}
20477 @item target mips @var{hostname}:@var{portnumber}
20478 On some @value{GDBN} host configurations, you can specify a TCP
20479 connection (for instance, to a serial line managed by a terminal
20480 concentrator) instead of a serial port, using the syntax
20481 @samp{@var{hostname}:@var{portnumber}}.
20483 @item target pmon @var{port}
20484 @kindex target pmon @var{port}
20487 @item target ddb @var{port}
20488 @kindex target ddb @var{port}
20489 NEC's DDB variant of PMON for Vr4300.
20491 @item target lsi @var{port}
20492 @kindex target lsi @var{port}
20493 LSI variant of PMON.
20495 @kindex target r3900
20496 @item target r3900 @var{dev}
20497 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20499 @kindex target array
20500 @item target array @var{dev}
20501 Array Tech LSI33K RAID controller board.
20507 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20510 @item set mipsfpu double
20511 @itemx set mipsfpu single
20512 @itemx set mipsfpu none
20513 @itemx set mipsfpu auto
20514 @itemx show mipsfpu
20515 @kindex set mipsfpu
20516 @kindex show mipsfpu
20517 @cindex @acronym{MIPS} remote floating point
20518 @cindex floating point, @acronym{MIPS} remote
20519 If your target board does not support the @acronym{MIPS} floating point
20520 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20521 need this, you may wish to put the command in your @value{GDBN} init
20522 file). This tells @value{GDBN} how to find the return value of
20523 functions which return floating point values. It also allows
20524 @value{GDBN} to avoid saving the floating point registers when calling
20525 functions on the board. If you are using a floating point coprocessor
20526 with only single precision floating point support, as on the @sc{r4650}
20527 processor, use the command @samp{set mipsfpu single}. The default
20528 double precision floating point coprocessor may be selected using
20529 @samp{set mipsfpu double}.
20531 In previous versions the only choices were double precision or no
20532 floating point, so @samp{set mipsfpu on} will select double precision
20533 and @samp{set mipsfpu off} will select no floating point.
20535 As usual, you can inquire about the @code{mipsfpu} variable with
20536 @samp{show mipsfpu}.
20538 @item set timeout @var{seconds}
20539 @itemx set retransmit-timeout @var{seconds}
20540 @itemx show timeout
20541 @itemx show retransmit-timeout
20542 @cindex @code{timeout}, @acronym{MIPS} protocol
20543 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20544 @kindex set timeout
20545 @kindex show timeout
20546 @kindex set retransmit-timeout
20547 @kindex show retransmit-timeout
20548 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20549 remote protocol, with the @code{set timeout @var{seconds}} command. The
20550 default is 5 seconds. Similarly, you can control the timeout used while
20551 waiting for an acknowledgment of a packet with the @code{set
20552 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20553 You can inspect both values with @code{show timeout} and @code{show
20554 retransmit-timeout}. (These commands are @emph{only} available when
20555 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20557 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20558 is waiting for your program to stop. In that case, @value{GDBN} waits
20559 forever because it has no way of knowing how long the program is going
20560 to run before stopping.
20562 @item set syn-garbage-limit @var{num}
20563 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20564 @cindex synchronize with remote @acronym{MIPS} target
20565 Limit the maximum number of characters @value{GDBN} should ignore when
20566 it tries to synchronize with the remote target. The default is 10
20567 characters. Setting the limit to -1 means there's no limit.
20569 @item show syn-garbage-limit
20570 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20571 Show the current limit on the number of characters to ignore when
20572 trying to synchronize with the remote system.
20574 @item set monitor-prompt @var{prompt}
20575 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20576 @cindex remote monitor prompt
20577 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20578 remote monitor. The default depends on the target:
20588 @item show monitor-prompt
20589 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20590 Show the current strings @value{GDBN} expects as the prompt from the
20593 @item set monitor-warnings
20594 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20595 Enable or disable monitor warnings about hardware breakpoints. This
20596 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20597 display warning messages whose codes are returned by the @code{lsi}
20598 PMON monitor for breakpoint commands.
20600 @item show monitor-warnings
20601 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20602 Show the current setting of printing monitor warnings.
20604 @item pmon @var{command}
20605 @kindex pmon@r{, @acronym{MIPS} remote}
20606 @cindex send PMON command
20607 This command allows sending an arbitrary @var{command} string to the
20608 monitor. The monitor must be in debug mode for this to work.
20611 @node PowerPC Embedded
20612 @subsection PowerPC Embedded
20614 @cindex DVC register
20615 @value{GDBN} supports using the DVC (Data Value Compare) register to
20616 implement in hardware simple hardware watchpoint conditions of the form:
20619 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20620 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20623 The DVC register will be automatically used when @value{GDBN} detects
20624 such pattern in a condition expression, and the created watchpoint uses one
20625 debug register (either the @code{exact-watchpoints} option is on and the
20626 variable is scalar, or the variable has a length of one byte). This feature
20627 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20630 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20631 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20632 in which case watchpoints using only one debug register are created when
20633 watching variables of scalar types.
20635 You can create an artificial array to watch an arbitrary memory
20636 region using one of the following commands (@pxref{Expressions}):
20639 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20640 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20643 PowerPC embedded processors support masked watchpoints. See the discussion
20644 about the @code{mask} argument in @ref{Set Watchpoints}.
20646 @cindex ranged breakpoint
20647 PowerPC embedded processors support hardware accelerated
20648 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20649 the inferior whenever it executes an instruction at any address within
20650 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20651 use the @code{break-range} command.
20653 @value{GDBN} provides the following PowerPC-specific commands:
20656 @kindex break-range
20657 @item break-range @var{start-location}, @var{end-location}
20658 Set a breakpoint for an address range.
20659 @var{start-location} and @var{end-location} can specify a function name,
20660 a line number, an offset of lines from the current line or from the start
20661 location, or an address of an instruction (see @ref{Specify Location},
20662 for a list of all the possible ways to specify a @var{location}.)
20663 The breakpoint will stop execution of the inferior whenever it
20664 executes an instruction at any address within the specified range,
20665 (including @var{start-location} and @var{end-location}.)
20667 @kindex set powerpc
20668 @item set powerpc soft-float
20669 @itemx show powerpc soft-float
20670 Force @value{GDBN} to use (or not use) a software floating point calling
20671 convention. By default, @value{GDBN} selects the calling convention based
20672 on the selected architecture and the provided executable file.
20674 @item set powerpc vector-abi
20675 @itemx show powerpc vector-abi
20676 Force @value{GDBN} to use the specified calling convention for vector
20677 arguments and return values. The valid options are @samp{auto};
20678 @samp{generic}, to avoid vector registers even if they are present;
20679 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20680 registers. By default, @value{GDBN} selects the calling convention
20681 based on the selected architecture and the provided executable file.
20683 @item set powerpc exact-watchpoints
20684 @itemx show powerpc exact-watchpoints
20685 Allow @value{GDBN} to use only one debug register when watching a variable
20686 of scalar type, thus assuming that the variable is accessed through the
20687 address of its first byte.
20689 @kindex target dink32
20690 @item target dink32 @var{dev}
20691 DINK32 ROM monitor.
20693 @kindex target ppcbug
20694 @item target ppcbug @var{dev}
20695 @kindex target ppcbug1
20696 @item target ppcbug1 @var{dev}
20697 PPCBUG ROM monitor for PowerPC.
20700 @item target sds @var{dev}
20701 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20704 @cindex SDS protocol
20705 The following commands specific to the SDS protocol are supported
20709 @item set sdstimeout @var{nsec}
20710 @kindex set sdstimeout
20711 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20712 default is 2 seconds.
20714 @item show sdstimeout
20715 @kindex show sdstimeout
20716 Show the current value of the SDS timeout.
20718 @item sds @var{command}
20719 @kindex sds@r{, a command}
20720 Send the specified @var{command} string to the SDS monitor.
20725 @subsection HP PA Embedded
20729 @kindex target op50n
20730 @item target op50n @var{dev}
20731 OP50N monitor, running on an OKI HPPA board.
20733 @kindex target w89k
20734 @item target w89k @var{dev}
20735 W89K monitor, running on a Winbond HPPA board.
20740 @subsection Tsqware Sparclet
20744 @value{GDBN} enables developers to debug tasks running on
20745 Sparclet targets from a Unix host.
20746 @value{GDBN} uses code that runs on
20747 both the Unix host and on the Sparclet target. The program
20748 @code{@value{GDBP}} is installed and executed on the Unix host.
20751 @item remotetimeout @var{args}
20752 @kindex remotetimeout
20753 @value{GDBN} supports the option @code{remotetimeout}.
20754 This option is set by the user, and @var{args} represents the number of
20755 seconds @value{GDBN} waits for responses.
20758 @cindex compiling, on Sparclet
20759 When compiling for debugging, include the options @samp{-g} to get debug
20760 information and @samp{-Ttext} to relocate the program to where you wish to
20761 load it on the target. You may also want to add the options @samp{-n} or
20762 @samp{-N} in order to reduce the size of the sections. Example:
20765 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20768 You can use @code{objdump} to verify that the addresses are what you intended:
20771 sparclet-aout-objdump --headers --syms prog
20774 @cindex running, on Sparclet
20776 your Unix execution search path to find @value{GDBN}, you are ready to
20777 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20778 (or @code{sparclet-aout-gdb}, depending on your installation).
20780 @value{GDBN} comes up showing the prompt:
20787 * Sparclet File:: Setting the file to debug
20788 * Sparclet Connection:: Connecting to Sparclet
20789 * Sparclet Download:: Sparclet download
20790 * Sparclet Execution:: Running and debugging
20793 @node Sparclet File
20794 @subsubsection Setting File to Debug
20796 The @value{GDBN} command @code{file} lets you choose with program to debug.
20799 (gdbslet) file prog
20803 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20804 @value{GDBN} locates
20805 the file by searching the directories listed in the command search
20807 If the file was compiled with debug information (option @samp{-g}), source
20808 files will be searched as well.
20809 @value{GDBN} locates
20810 the source files by searching the directories listed in the directory search
20811 path (@pxref{Environment, ,Your Program's Environment}).
20813 to find a file, it displays a message such as:
20816 prog: No such file or directory.
20819 When this happens, add the appropriate directories to the search paths with
20820 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20821 @code{target} command again.
20823 @node Sparclet Connection
20824 @subsubsection Connecting to Sparclet
20826 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20827 To connect to a target on serial port ``@code{ttya}'', type:
20830 (gdbslet) target sparclet /dev/ttya
20831 Remote target sparclet connected to /dev/ttya
20832 main () at ../prog.c:3
20836 @value{GDBN} displays messages like these:
20842 @node Sparclet Download
20843 @subsubsection Sparclet Download
20845 @cindex download to Sparclet
20846 Once connected to the Sparclet target,
20847 you can use the @value{GDBN}
20848 @code{load} command to download the file from the host to the target.
20849 The file name and load offset should be given as arguments to the @code{load}
20851 Since the file format is aout, the program must be loaded to the starting
20852 address. You can use @code{objdump} to find out what this value is. The load
20853 offset is an offset which is added to the VMA (virtual memory address)
20854 of each of the file's sections.
20855 For instance, if the program
20856 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20857 and bss at 0x12010170, in @value{GDBN}, type:
20860 (gdbslet) load prog 0x12010000
20861 Loading section .text, size 0xdb0 vma 0x12010000
20864 If the code is loaded at a different address then what the program was linked
20865 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20866 to tell @value{GDBN} where to map the symbol table.
20868 @node Sparclet Execution
20869 @subsubsection Running and Debugging
20871 @cindex running and debugging Sparclet programs
20872 You can now begin debugging the task using @value{GDBN}'s execution control
20873 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20874 manual for the list of commands.
20878 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20880 Starting program: prog
20881 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20882 3 char *symarg = 0;
20884 4 char *execarg = "hello!";
20889 @subsection Fujitsu Sparclite
20893 @kindex target sparclite
20894 @item target sparclite @var{dev}
20895 Fujitsu sparclite boards, used only for the purpose of loading.
20896 You must use an additional command to debug the program.
20897 For example: target remote @var{dev} using @value{GDBN} standard
20903 @subsection Zilog Z8000
20906 @cindex simulator, Z8000
20907 @cindex Zilog Z8000 simulator
20909 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20912 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20913 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20914 segmented variant). The simulator recognizes which architecture is
20915 appropriate by inspecting the object code.
20918 @item target sim @var{args}
20920 @kindex target sim@r{, with Z8000}
20921 Debug programs on a simulated CPU. If the simulator supports setup
20922 options, specify them via @var{args}.
20926 After specifying this target, you can debug programs for the simulated
20927 CPU in the same style as programs for your host computer; use the
20928 @code{file} command to load a new program image, the @code{run} command
20929 to run your program, and so on.
20931 As well as making available all the usual machine registers
20932 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20933 additional items of information as specially named registers:
20938 Counts clock-ticks in the simulator.
20941 Counts instructions run in the simulator.
20944 Execution time in 60ths of a second.
20948 You can refer to these values in @value{GDBN} expressions with the usual
20949 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20950 conditional breakpoint that suspends only after at least 5000
20951 simulated clock ticks.
20954 @subsection Atmel AVR
20957 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20958 following AVR-specific commands:
20961 @item info io_registers
20962 @kindex info io_registers@r{, AVR}
20963 @cindex I/O registers (Atmel AVR)
20964 This command displays information about the AVR I/O registers. For
20965 each register, @value{GDBN} prints its number and value.
20972 When configured for debugging CRIS, @value{GDBN} provides the
20973 following CRIS-specific commands:
20976 @item set cris-version @var{ver}
20977 @cindex CRIS version
20978 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20979 The CRIS version affects register names and sizes. This command is useful in
20980 case autodetection of the CRIS version fails.
20982 @item show cris-version
20983 Show the current CRIS version.
20985 @item set cris-dwarf2-cfi
20986 @cindex DWARF-2 CFI and CRIS
20987 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20988 Change to @samp{off} when using @code{gcc-cris} whose version is below
20991 @item show cris-dwarf2-cfi
20992 Show the current state of using DWARF-2 CFI.
20994 @item set cris-mode @var{mode}
20996 Set the current CRIS mode to @var{mode}. It should only be changed when
20997 debugging in guru mode, in which case it should be set to
20998 @samp{guru} (the default is @samp{normal}).
21000 @item show cris-mode
21001 Show the current CRIS mode.
21005 @subsection Renesas Super-H
21008 For the Renesas Super-H processor, @value{GDBN} provides these
21012 @item set sh calling-convention @var{convention}
21013 @kindex set sh calling-convention
21014 Set the calling-convention used when calling functions from @value{GDBN}.
21015 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
21016 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
21017 convention. If the DWARF-2 information of the called function specifies
21018 that the function follows the Renesas calling convention, the function
21019 is called using the Renesas calling convention. If the calling convention
21020 is set to @samp{renesas}, the Renesas calling convention is always used,
21021 regardless of the DWARF-2 information. This can be used to override the
21022 default of @samp{gcc} if debug information is missing, or the compiler
21023 does not emit the DWARF-2 calling convention entry for a function.
21025 @item show sh calling-convention
21026 @kindex show sh calling-convention
21027 Show the current calling convention setting.
21032 @node Architectures
21033 @section Architectures
21035 This section describes characteristics of architectures that affect
21036 all uses of @value{GDBN} with the architecture, both native and cross.
21043 * HPPA:: HP PA architecture
21044 * SPU:: Cell Broadband Engine SPU architecture
21050 @subsection AArch64
21051 @cindex AArch64 support
21053 When @value{GDBN} is debugging the AArch64 architecture, it provides the
21054 following special commands:
21057 @item set debug aarch64
21058 @kindex set debug aarch64
21059 This command determines whether AArch64 architecture-specific debugging
21060 messages are to be displayed.
21062 @item show debug aarch64
21063 Show whether AArch64 debugging messages are displayed.
21068 @subsection x86 Architecture-specific Issues
21071 @item set struct-convention @var{mode}
21072 @kindex set struct-convention
21073 @cindex struct return convention
21074 @cindex struct/union returned in registers
21075 Set the convention used by the inferior to return @code{struct}s and
21076 @code{union}s from functions to @var{mode}. Possible values of
21077 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
21078 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
21079 are returned on the stack, while @code{"reg"} means that a
21080 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
21081 be returned in a register.
21083 @item show struct-convention
21084 @kindex show struct-convention
21085 Show the current setting of the convention to return @code{struct}s
21092 See the following section.
21095 @subsection @acronym{MIPS}
21097 @cindex stack on Alpha
21098 @cindex stack on @acronym{MIPS}
21099 @cindex Alpha stack
21100 @cindex @acronym{MIPS} stack
21101 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
21102 sometimes requires @value{GDBN} to search backward in the object code to
21103 find the beginning of a function.
21105 @cindex response time, @acronym{MIPS} debugging
21106 To improve response time (especially for embedded applications, where
21107 @value{GDBN} may be restricted to a slow serial line for this search)
21108 you may want to limit the size of this search, using one of these
21112 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
21113 @item set heuristic-fence-post @var{limit}
21114 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
21115 search for the beginning of a function. A value of @var{0} (the
21116 default) means there is no limit. However, except for @var{0}, the
21117 larger the limit the more bytes @code{heuristic-fence-post} must search
21118 and therefore the longer it takes to run. You should only need to use
21119 this command when debugging a stripped executable.
21121 @item show heuristic-fence-post
21122 Display the current limit.
21126 These commands are available @emph{only} when @value{GDBN} is configured
21127 for debugging programs on Alpha or @acronym{MIPS} processors.
21129 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
21133 @item set mips abi @var{arg}
21134 @kindex set mips abi
21135 @cindex set ABI for @acronym{MIPS}
21136 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
21137 values of @var{arg} are:
21141 The default ABI associated with the current binary (this is the
21151 @item show mips abi
21152 @kindex show mips abi
21153 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
21155 @item set mips compression @var{arg}
21156 @kindex set mips compression
21157 @cindex code compression, @acronym{MIPS}
21158 Tell @value{GDBN} which @acronym{MIPS} compressed
21159 @acronym{ISA, Instruction Set Architecture} encoding is used by the
21160 inferior. @value{GDBN} uses this for code disassembly and other
21161 internal interpretation purposes. This setting is only referred to
21162 when no executable has been associated with the debugging session or
21163 the executable does not provide information about the encoding it uses.
21164 Otherwise this setting is automatically updated from information
21165 provided by the executable.
21167 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
21168 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
21169 executables containing @acronym{MIPS16} code frequently are not
21170 identified as such.
21172 This setting is ``sticky''; that is, it retains its value across
21173 debugging sessions until reset either explicitly with this command or
21174 implicitly from an executable.
21176 The compiler and/or assembler typically add symbol table annotations to
21177 identify functions compiled for the @acronym{MIPS16} or
21178 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21179 are present, @value{GDBN} uses them in preference to the global
21180 compressed @acronym{ISA} encoding setting.
21182 @item show mips compression
21183 @kindex show mips compression
21184 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21185 @value{GDBN} to debug the inferior.
21188 @itemx show mipsfpu
21189 @xref{MIPS Embedded, set mipsfpu}.
21191 @item set mips mask-address @var{arg}
21192 @kindex set mips mask-address
21193 @cindex @acronym{MIPS} addresses, masking
21194 This command determines whether the most-significant 32 bits of 64-bit
21195 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21196 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21197 setting, which lets @value{GDBN} determine the correct value.
21199 @item show mips mask-address
21200 @kindex show mips mask-address
21201 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21204 @item set remote-mips64-transfers-32bit-regs
21205 @kindex set remote-mips64-transfers-32bit-regs
21206 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21207 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21208 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21209 and 64 bits for other registers, set this option to @samp{on}.
21211 @item show remote-mips64-transfers-32bit-regs
21212 @kindex show remote-mips64-transfers-32bit-regs
21213 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21215 @item set debug mips
21216 @kindex set debug mips
21217 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21218 target code in @value{GDBN}.
21220 @item show debug mips
21221 @kindex show debug mips
21222 Show the current setting of @acronym{MIPS} debugging messages.
21228 @cindex HPPA support
21230 When @value{GDBN} is debugging the HP PA architecture, it provides the
21231 following special commands:
21234 @item set debug hppa
21235 @kindex set debug hppa
21236 This command determines whether HPPA architecture-specific debugging
21237 messages are to be displayed.
21239 @item show debug hppa
21240 Show whether HPPA debugging messages are displayed.
21242 @item maint print unwind @var{address}
21243 @kindex maint print unwind@r{, HPPA}
21244 This command displays the contents of the unwind table entry at the
21245 given @var{address}.
21251 @subsection Cell Broadband Engine SPU architecture
21252 @cindex Cell Broadband Engine
21255 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21256 it provides the following special commands:
21259 @item info spu event
21261 Display SPU event facility status. Shows current event mask
21262 and pending event status.
21264 @item info spu signal
21265 Display SPU signal notification facility status. Shows pending
21266 signal-control word and signal notification mode of both signal
21267 notification channels.
21269 @item info spu mailbox
21270 Display SPU mailbox facility status. Shows all pending entries,
21271 in order of processing, in each of the SPU Write Outbound,
21272 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21275 Display MFC DMA status. Shows all pending commands in the MFC
21276 DMA queue. For each entry, opcode, tag, class IDs, effective
21277 and local store addresses and transfer size are shown.
21279 @item info spu proxydma
21280 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21281 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21282 and local store addresses and transfer size are shown.
21286 When @value{GDBN} is debugging a combined PowerPC/SPU application
21287 on the Cell Broadband Engine, it provides in addition the following
21291 @item set spu stop-on-load @var{arg}
21293 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21294 will give control to the user when a new SPE thread enters its @code{main}
21295 function. The default is @code{off}.
21297 @item show spu stop-on-load
21299 Show whether to stop for new SPE threads.
21301 @item set spu auto-flush-cache @var{arg}
21302 Set whether to automatically flush the software-managed cache. When set to
21303 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21304 cache to be flushed whenever SPE execution stops. This provides a consistent
21305 view of PowerPC memory that is accessed via the cache. If an application
21306 does not use the software-managed cache, this option has no effect.
21308 @item show spu auto-flush-cache
21309 Show whether to automatically flush the software-managed cache.
21314 @subsection PowerPC
21315 @cindex PowerPC architecture
21317 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21318 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21319 numbers stored in the floating point registers. These values must be stored
21320 in two consecutive registers, always starting at an even register like
21321 @code{f0} or @code{f2}.
21323 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21324 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21325 @code{f2} and @code{f3} for @code{$dl1} and so on.
21327 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21328 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21331 @subsection Nios II
21332 @cindex Nios II architecture
21334 When @value{GDBN} is debugging the Nios II architecture,
21335 it provides the following special commands:
21339 @item set debug nios2
21340 @kindex set debug nios2
21341 This command turns on and off debugging messages for the Nios II
21342 target code in @value{GDBN}.
21344 @item show debug nios2
21345 @kindex show debug nios2
21346 Show the current setting of Nios II debugging messages.
21349 @node Controlling GDB
21350 @chapter Controlling @value{GDBN}
21352 You can alter the way @value{GDBN} interacts with you by using the
21353 @code{set} command. For commands controlling how @value{GDBN} displays
21354 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21359 * Editing:: Command editing
21360 * Command History:: Command history
21361 * Screen Size:: Screen size
21362 * Numbers:: Numbers
21363 * ABI:: Configuring the current ABI
21364 * Auto-loading:: Automatically loading associated files
21365 * Messages/Warnings:: Optional warnings and messages
21366 * Debugging Output:: Optional messages about internal happenings
21367 * Other Misc Settings:: Other Miscellaneous Settings
21375 @value{GDBN} indicates its readiness to read a command by printing a string
21376 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21377 can change the prompt string with the @code{set prompt} command. For
21378 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21379 the prompt in one of the @value{GDBN} sessions so that you can always tell
21380 which one you are talking to.
21382 @emph{Note:} @code{set prompt} does not add a space for you after the
21383 prompt you set. This allows you to set a prompt which ends in a space
21384 or a prompt that does not.
21388 @item set prompt @var{newprompt}
21389 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21391 @kindex show prompt
21393 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21396 Versions of @value{GDBN} that ship with Python scripting enabled have
21397 prompt extensions. The commands for interacting with these extensions
21401 @kindex set extended-prompt
21402 @item set extended-prompt @var{prompt}
21403 Set an extended prompt that allows for substitutions.
21404 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21405 substitution. Any escape sequences specified as part of the prompt
21406 string are replaced with the corresponding strings each time the prompt
21412 set extended-prompt Current working directory: \w (gdb)
21415 Note that when an extended-prompt is set, it takes control of the
21416 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21418 @kindex show extended-prompt
21419 @item show extended-prompt
21420 Prints the extended prompt. Any escape sequences specified as part of
21421 the prompt string with @code{set extended-prompt}, are replaced with the
21422 corresponding strings each time the prompt is displayed.
21426 @section Command Editing
21428 @cindex command line editing
21430 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21431 @sc{gnu} library provides consistent behavior for programs which provide a
21432 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21433 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21434 substitution, and a storage and recall of command history across
21435 debugging sessions.
21437 You may control the behavior of command line editing in @value{GDBN} with the
21438 command @code{set}.
21441 @kindex set editing
21444 @itemx set editing on
21445 Enable command line editing (enabled by default).
21447 @item set editing off
21448 Disable command line editing.
21450 @kindex show editing
21452 Show whether command line editing is enabled.
21455 @ifset SYSTEM_READLINE
21456 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21458 @ifclear SYSTEM_READLINE
21459 @xref{Command Line Editing},
21461 for more details about the Readline
21462 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21463 encouraged to read that chapter.
21465 @node Command History
21466 @section Command History
21467 @cindex command history
21469 @value{GDBN} can keep track of the commands you type during your
21470 debugging sessions, so that you can be certain of precisely what
21471 happened. Use these commands to manage the @value{GDBN} command
21474 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21475 package, to provide the history facility.
21476 @ifset SYSTEM_READLINE
21477 @xref{Using History Interactively, , , history, GNU History Library},
21479 @ifclear SYSTEM_READLINE
21480 @xref{Using History Interactively},
21482 for the detailed description of the History library.
21484 To issue a command to @value{GDBN} without affecting certain aspects of
21485 the state which is seen by users, prefix it with @samp{server }
21486 (@pxref{Server Prefix}). This
21487 means that this command will not affect the command history, nor will it
21488 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21489 pressed on a line by itself.
21491 @cindex @code{server}, command prefix
21492 The server prefix does not affect the recording of values into the value
21493 history; to print a value without recording it into the value history,
21494 use the @code{output} command instead of the @code{print} command.
21496 Here is the description of @value{GDBN} commands related to command
21500 @cindex history substitution
21501 @cindex history file
21502 @kindex set history filename
21503 @cindex @env{GDBHISTFILE}, environment variable
21504 @item set history filename @var{fname}
21505 Set the name of the @value{GDBN} command history file to @var{fname}.
21506 This is the file where @value{GDBN} reads an initial command history
21507 list, and where it writes the command history from this session when it
21508 exits. You can access this list through history expansion or through
21509 the history command editing characters listed below. This file defaults
21510 to the value of the environment variable @code{GDBHISTFILE}, or to
21511 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21514 @cindex save command history
21515 @kindex set history save
21516 @item set history save
21517 @itemx set history save on
21518 Record command history in a file, whose name may be specified with the
21519 @code{set history filename} command. By default, this option is disabled.
21521 @item set history save off
21522 Stop recording command history in a file.
21524 @cindex history size
21525 @kindex set history size
21526 @cindex @env{HISTSIZE}, environment variable
21527 @item set history size @var{size}
21528 @itemx set history size unlimited
21529 Set the number of commands which @value{GDBN} keeps in its history list.
21530 This defaults to the value of the environment variable
21531 @code{HISTSIZE}, or to 256 if this variable is not set. If @var{size}
21532 is @code{unlimited}, the number of commands @value{GDBN} keeps in the
21533 history list is unlimited.
21536 History expansion assigns special meaning to the character @kbd{!}.
21537 @ifset SYSTEM_READLINE
21538 @xref{Event Designators, , , history, GNU History Library},
21540 @ifclear SYSTEM_READLINE
21541 @xref{Event Designators},
21545 @cindex history expansion, turn on/off
21546 Since @kbd{!} is also the logical not operator in C, history expansion
21547 is off by default. If you decide to enable history expansion with the
21548 @code{set history expansion on} command, you may sometimes need to
21549 follow @kbd{!} (when it is used as logical not, in an expression) with
21550 a space or a tab to prevent it from being expanded. The readline
21551 history facilities do not attempt substitution on the strings
21552 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21554 The commands to control history expansion are:
21557 @item set history expansion on
21558 @itemx set history expansion
21559 @kindex set history expansion
21560 Enable history expansion. History expansion is off by default.
21562 @item set history expansion off
21563 Disable history expansion.
21566 @kindex show history
21568 @itemx show history filename
21569 @itemx show history save
21570 @itemx show history size
21571 @itemx show history expansion
21572 These commands display the state of the @value{GDBN} history parameters.
21573 @code{show history} by itself displays all four states.
21578 @kindex show commands
21579 @cindex show last commands
21580 @cindex display command history
21581 @item show commands
21582 Display the last ten commands in the command history.
21584 @item show commands @var{n}
21585 Print ten commands centered on command number @var{n}.
21587 @item show commands +
21588 Print ten commands just after the commands last printed.
21592 @section Screen Size
21593 @cindex size of screen
21594 @cindex pauses in output
21596 Certain commands to @value{GDBN} may produce large amounts of
21597 information output to the screen. To help you read all of it,
21598 @value{GDBN} pauses and asks you for input at the end of each page of
21599 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21600 to discard the remaining output. Also, the screen width setting
21601 determines when to wrap lines of output. Depending on what is being
21602 printed, @value{GDBN} tries to break the line at a readable place,
21603 rather than simply letting it overflow onto the following line.
21605 Normally @value{GDBN} knows the size of the screen from the terminal
21606 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21607 together with the value of the @code{TERM} environment variable and the
21608 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21609 you can override it with the @code{set height} and @code{set
21616 @kindex show height
21617 @item set height @var{lpp}
21618 @itemx set height unlimited
21620 @itemx set width @var{cpl}
21621 @itemx set width unlimited
21623 These @code{set} commands specify a screen height of @var{lpp} lines and
21624 a screen width of @var{cpl} characters. The associated @code{show}
21625 commands display the current settings.
21627 If you specify a height of either @code{unlimited} or zero lines,
21628 @value{GDBN} does not pause during output no matter how long the
21629 output is. This is useful if output is to a file or to an editor
21632 Likewise, you can specify @samp{set width unlimited} or @samp{set
21633 width 0} to prevent @value{GDBN} from wrapping its output.
21635 @item set pagination on
21636 @itemx set pagination off
21637 @kindex set pagination
21638 Turn the output pagination on or off; the default is on. Turning
21639 pagination off is the alternative to @code{set height unlimited}. Note that
21640 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21641 Options, -batch}) also automatically disables pagination.
21643 @item show pagination
21644 @kindex show pagination
21645 Show the current pagination mode.
21650 @cindex number representation
21651 @cindex entering numbers
21653 You can always enter numbers in octal, decimal, or hexadecimal in
21654 @value{GDBN} by the usual conventions: octal numbers begin with
21655 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21656 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21657 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21658 10; likewise, the default display for numbers---when no particular
21659 format is specified---is base 10. You can change the default base for
21660 both input and output with the commands described below.
21663 @kindex set input-radix
21664 @item set input-radix @var{base}
21665 Set the default base for numeric input. Supported choices
21666 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21667 specified either unambiguously or using the current input radix; for
21671 set input-radix 012
21672 set input-radix 10.
21673 set input-radix 0xa
21677 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21678 leaves the input radix unchanged, no matter what it was, since
21679 @samp{10}, being without any leading or trailing signs of its base, is
21680 interpreted in the current radix. Thus, if the current radix is 16,
21681 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21684 @kindex set output-radix
21685 @item set output-radix @var{base}
21686 Set the default base for numeric display. Supported choices
21687 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21688 specified either unambiguously or using the current input radix.
21690 @kindex show input-radix
21691 @item show input-radix
21692 Display the current default base for numeric input.
21694 @kindex show output-radix
21695 @item show output-radix
21696 Display the current default base for numeric display.
21698 @item set radix @r{[}@var{base}@r{]}
21702 These commands set and show the default base for both input and output
21703 of numbers. @code{set radix} sets the radix of input and output to
21704 the same base; without an argument, it resets the radix back to its
21705 default value of 10.
21710 @section Configuring the Current ABI
21712 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21713 application automatically. However, sometimes you need to override its
21714 conclusions. Use these commands to manage @value{GDBN}'s view of the
21720 @cindex Newlib OS ABI and its influence on the longjmp handling
21722 One @value{GDBN} configuration can debug binaries for multiple operating
21723 system targets, either via remote debugging or native emulation.
21724 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21725 but you can override its conclusion using the @code{set osabi} command.
21726 One example where this is useful is in debugging of binaries which use
21727 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21728 not have the same identifying marks that the standard C library for your
21731 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21732 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21733 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21734 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21738 Show the OS ABI currently in use.
21741 With no argument, show the list of registered available OS ABI's.
21743 @item set osabi @var{abi}
21744 Set the current OS ABI to @var{abi}.
21747 @cindex float promotion
21749 Generally, the way that an argument of type @code{float} is passed to a
21750 function depends on whether the function is prototyped. For a prototyped
21751 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21752 according to the architecture's convention for @code{float}. For unprototyped
21753 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21754 @code{double} and then passed.
21756 Unfortunately, some forms of debug information do not reliably indicate whether
21757 a function is prototyped. If @value{GDBN} calls a function that is not marked
21758 as prototyped, it consults @kbd{set coerce-float-to-double}.
21761 @kindex set coerce-float-to-double
21762 @item set coerce-float-to-double
21763 @itemx set coerce-float-to-double on
21764 Arguments of type @code{float} will be promoted to @code{double} when passed
21765 to an unprototyped function. This is the default setting.
21767 @item set coerce-float-to-double off
21768 Arguments of type @code{float} will be passed directly to unprototyped
21771 @kindex show coerce-float-to-double
21772 @item show coerce-float-to-double
21773 Show the current setting of promoting @code{float} to @code{double}.
21777 @kindex show cp-abi
21778 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21779 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21780 used to build your application. @value{GDBN} only fully supports
21781 programs with a single C@t{++} ABI; if your program contains code using
21782 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21783 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21784 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21785 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21786 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21787 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21792 Show the C@t{++} ABI currently in use.
21795 With no argument, show the list of supported C@t{++} ABI's.
21797 @item set cp-abi @var{abi}
21798 @itemx set cp-abi auto
21799 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21803 @section Automatically loading associated files
21804 @cindex auto-loading
21806 @value{GDBN} sometimes reads files with commands and settings automatically,
21807 without being explicitly told so by the user. We call this feature
21808 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21809 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21810 results or introduce security risks (e.g., if the file comes from untrusted
21813 Note that loading of these associated files (including the local @file{.gdbinit}
21814 file) requires accordingly configured @code{auto-load safe-path}
21815 (@pxref{Auto-loading safe path}).
21817 For these reasons, @value{GDBN} includes commands and options to let you
21818 control when to auto-load files and which files should be auto-loaded.
21821 @anchor{set auto-load off}
21822 @kindex set auto-load off
21823 @item set auto-load off
21824 Globally disable loading of all auto-loaded files.
21825 You may want to use this command with the @samp{-iex} option
21826 (@pxref{Option -init-eval-command}) such as:
21828 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21831 Be aware that system init file (@pxref{System-wide configuration})
21832 and init files from your home directory (@pxref{Home Directory Init File})
21833 still get read (as they come from generally trusted directories).
21834 To prevent @value{GDBN} from auto-loading even those init files, use the
21835 @option{-nx} option (@pxref{Mode Options}), in addition to
21836 @code{set auto-load no}.
21838 @anchor{show auto-load}
21839 @kindex show auto-load
21840 @item show auto-load
21841 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21845 (gdb) show auto-load
21846 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21847 libthread-db: Auto-loading of inferior specific libthread_db is on.
21848 local-gdbinit: Auto-loading of .gdbinit script from current directory
21850 python-scripts: Auto-loading of Python scripts is on.
21851 safe-path: List of directories from which it is safe to auto-load files
21852 is $debugdir:$datadir/auto-load.
21853 scripts-directory: List of directories from which to load auto-loaded scripts
21854 is $debugdir:$datadir/auto-load.
21857 @anchor{info auto-load}
21858 @kindex info auto-load
21859 @item info auto-load
21860 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21864 (gdb) info auto-load
21867 Yes /home/user/gdb/gdb-gdb.gdb
21868 libthread-db: No auto-loaded libthread-db.
21869 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21873 Yes /home/user/gdb/gdb-gdb.py
21877 These are various kinds of files @value{GDBN} can automatically load:
21881 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21883 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21885 @xref{dotdebug_gdb_scripts section},
21886 controlled by @ref{set auto-load python-scripts}.
21888 @xref{Init File in the Current Directory},
21889 controlled by @ref{set auto-load local-gdbinit}.
21891 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21894 These are @value{GDBN} control commands for the auto-loading:
21896 @multitable @columnfractions .5 .5
21897 @item @xref{set auto-load off}.
21898 @tab Disable auto-loading globally.
21899 @item @xref{show auto-load}.
21900 @tab Show setting of all kinds of files.
21901 @item @xref{info auto-load}.
21902 @tab Show state of all kinds of files.
21903 @item @xref{set auto-load gdb-scripts}.
21904 @tab Control for @value{GDBN} command scripts.
21905 @item @xref{show auto-load gdb-scripts}.
21906 @tab Show setting of @value{GDBN} command scripts.
21907 @item @xref{info auto-load gdb-scripts}.
21908 @tab Show state of @value{GDBN} command scripts.
21909 @item @xref{set auto-load python-scripts}.
21910 @tab Control for @value{GDBN} Python scripts.
21911 @item @xref{show auto-load python-scripts}.
21912 @tab Show setting of @value{GDBN} Python scripts.
21913 @item @xref{info auto-load python-scripts}.
21914 @tab Show state of @value{GDBN} Python scripts.
21915 @item @xref{set auto-load scripts-directory}.
21916 @tab Control for @value{GDBN} auto-loaded scripts location.
21917 @item @xref{show auto-load scripts-directory}.
21918 @tab Show @value{GDBN} auto-loaded scripts location.
21919 @item @xref{set auto-load local-gdbinit}.
21920 @tab Control for init file in the current directory.
21921 @item @xref{show auto-load local-gdbinit}.
21922 @tab Show setting of init file in the current directory.
21923 @item @xref{info auto-load local-gdbinit}.
21924 @tab Show state of init file in the current directory.
21925 @item @xref{set auto-load libthread-db}.
21926 @tab Control for thread debugging library.
21927 @item @xref{show auto-load libthread-db}.
21928 @tab Show setting of thread debugging library.
21929 @item @xref{info auto-load libthread-db}.
21930 @tab Show state of thread debugging library.
21931 @item @xref{set auto-load safe-path}.
21932 @tab Control directories trusted for automatic loading.
21933 @item @xref{show auto-load safe-path}.
21934 @tab Show directories trusted for automatic loading.
21935 @item @xref{add-auto-load-safe-path}.
21936 @tab Add directory trusted for automatic loading.
21940 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21941 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21942 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21943 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21944 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21945 @xref{Python Auto-loading}.
21948 @node Init File in the Current Directory
21949 @subsection Automatically loading init file in the current directory
21950 @cindex auto-loading init file in the current directory
21952 By default, @value{GDBN} reads and executes the canned sequences of commands
21953 from init file (if any) in the current working directory,
21954 see @ref{Init File in the Current Directory during Startup}.
21956 Note that loading of this local @file{.gdbinit} file also requires accordingly
21957 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21960 @anchor{set auto-load local-gdbinit}
21961 @kindex set auto-load local-gdbinit
21962 @item set auto-load local-gdbinit [on|off]
21963 Enable or disable the auto-loading of canned sequences of commands
21964 (@pxref{Sequences}) found in init file in the current directory.
21966 @anchor{show auto-load local-gdbinit}
21967 @kindex show auto-load local-gdbinit
21968 @item show auto-load local-gdbinit
21969 Show whether auto-loading of canned sequences of commands from init file in the
21970 current directory is enabled or disabled.
21972 @anchor{info auto-load local-gdbinit}
21973 @kindex info auto-load local-gdbinit
21974 @item info auto-load local-gdbinit
21975 Print whether canned sequences of commands from init file in the
21976 current directory have been auto-loaded.
21979 @node libthread_db.so.1 file
21980 @subsection Automatically loading thread debugging library
21981 @cindex auto-loading libthread_db.so.1
21983 This feature is currently present only on @sc{gnu}/Linux native hosts.
21985 @value{GDBN} reads in some cases thread debugging library from places specific
21986 to the inferior (@pxref{set libthread-db-search-path}).
21988 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21989 without checking this @samp{set auto-load libthread-db} switch as system
21990 libraries have to be trusted in general. In all other cases of
21991 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21992 auto-load libthread-db} is enabled before trying to open such thread debugging
21995 Note that loading of this debugging library also requires accordingly configured
21996 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21999 @anchor{set auto-load libthread-db}
22000 @kindex set auto-load libthread-db
22001 @item set auto-load libthread-db [on|off]
22002 Enable or disable the auto-loading of inferior specific thread debugging library.
22004 @anchor{show auto-load libthread-db}
22005 @kindex show auto-load libthread-db
22006 @item show auto-load libthread-db
22007 Show whether auto-loading of inferior specific thread debugging library is
22008 enabled or disabled.
22010 @anchor{info auto-load libthread-db}
22011 @kindex info auto-load libthread-db
22012 @item info auto-load libthread-db
22013 Print the list of all loaded inferior specific thread debugging libraries and
22014 for each such library print list of inferior @var{pid}s using it.
22017 @node objfile-gdb.gdb file
22018 @subsection The @file{@var{objfile}-gdb.gdb} file
22019 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
22021 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
22022 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
22023 auto-load gdb-scripts} is set to @samp{on}.
22025 Note that loading of this script file also requires accordingly configured
22026 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
22028 For more background refer to the similar Python scripts auto-loading
22029 description (@pxref{objfile-gdb.py file}).
22032 @anchor{set auto-load gdb-scripts}
22033 @kindex set auto-load gdb-scripts
22034 @item set auto-load gdb-scripts [on|off]
22035 Enable or disable the auto-loading of canned sequences of commands scripts.
22037 @anchor{show auto-load gdb-scripts}
22038 @kindex show auto-load gdb-scripts
22039 @item show auto-load gdb-scripts
22040 Show whether auto-loading of canned sequences of commands scripts is enabled or
22043 @anchor{info auto-load gdb-scripts}
22044 @kindex info auto-load gdb-scripts
22045 @cindex print list of auto-loaded canned sequences of commands scripts
22046 @item info auto-load gdb-scripts [@var{regexp}]
22047 Print the list of all canned sequences of commands scripts that @value{GDBN}
22051 If @var{regexp} is supplied only canned sequences of commands scripts with
22052 matching names are printed.
22054 @node Auto-loading safe path
22055 @subsection Security restriction for auto-loading
22056 @cindex auto-loading safe-path
22058 As the files of inferior can come from untrusted source (such as submitted by
22059 an application user) @value{GDBN} does not always load any files automatically.
22060 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
22061 directories trusted for loading files not explicitly requested by user.
22062 Each directory can also be a shell wildcard pattern.
22064 If the path is not set properly you will see a warning and the file will not
22069 Reading symbols from /home/user/gdb/gdb...done.
22070 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
22071 declined by your `auto-load safe-path' set
22072 to "$debugdir:$datadir/auto-load".
22073 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
22074 declined by your `auto-load safe-path' set
22075 to "$debugdir:$datadir/auto-load".
22079 To instruct @value{GDBN} to go ahead and use the init files anyway,
22080 invoke @value{GDBN} like this:
22083 $ gdb -q -iex "set auto-load safe-path /home/user/gdb" ./gdb
22086 The list of trusted directories is controlled by the following commands:
22089 @anchor{set auto-load safe-path}
22090 @kindex set auto-load safe-path
22091 @item set auto-load safe-path @r{[}@var{directories}@r{]}
22092 Set the list of directories (and their subdirectories) trusted for automatic
22093 loading and execution of scripts. You can also enter a specific trusted file.
22094 Each directory can also be a shell wildcard pattern; wildcards do not match
22095 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
22096 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
22097 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
22098 its default value as specified during @value{GDBN} compilation.
22100 The list of directories uses path separator (@samp{:} on GNU and Unix
22101 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
22102 to the @env{PATH} environment variable.
22104 @anchor{show auto-load safe-path}
22105 @kindex show auto-load safe-path
22106 @item show auto-load safe-path
22107 Show the list of directories trusted for automatic loading and execution of
22110 @anchor{add-auto-load-safe-path}
22111 @kindex add-auto-load-safe-path
22112 @item add-auto-load-safe-path
22113 Add an entry (or list of entries) the list of directories trusted for automatic
22114 loading and execution of scripts. Multiple entries may be delimited by the
22115 host platform path separator in use.
22118 This variable defaults to what @code{--with-auto-load-dir} has been configured
22119 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
22120 substitution applies the same as for @ref{set auto-load scripts-directory}.
22121 The default @code{set auto-load safe-path} value can be also overriden by
22122 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
22124 Setting this variable to @file{/} disables this security protection,
22125 corresponding @value{GDBN} configuration option is
22126 @option{--without-auto-load-safe-path}.
22127 This variable is supposed to be set to the system directories writable by the
22128 system superuser only. Users can add their source directories in init files in
22129 their home directories (@pxref{Home Directory Init File}). See also deprecated
22130 init file in the current directory
22131 (@pxref{Init File in the Current Directory during Startup}).
22133 To force @value{GDBN} to load the files it declined to load in the previous
22134 example, you could use one of the following ways:
22137 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
22138 Specify this trusted directory (or a file) as additional component of the list.
22139 You have to specify also any existing directories displayed by
22140 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
22142 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
22143 Specify this directory as in the previous case but just for a single
22144 @value{GDBN} session.
22146 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
22147 Disable auto-loading safety for a single @value{GDBN} session.
22148 This assumes all the files you debug during this @value{GDBN} session will come
22149 from trusted sources.
22151 @item @kbd{./configure --without-auto-load-safe-path}
22152 During compilation of @value{GDBN} you may disable any auto-loading safety.
22153 This assumes all the files you will ever debug with this @value{GDBN} come from
22157 On the other hand you can also explicitly forbid automatic files loading which
22158 also suppresses any such warning messages:
22161 @item @kbd{gdb -iex "set auto-load no" @dots{}}
22162 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
22164 @item @file{~/.gdbinit}: @samp{set auto-load no}
22165 Disable auto-loading globally for the user
22166 (@pxref{Home Directory Init File}). While it is improbable, you could also
22167 use system init file instead (@pxref{System-wide configuration}).
22170 This setting applies to the file names as entered by user. If no entry matches
22171 @value{GDBN} tries as a last resort to also resolve all the file names into
22172 their canonical form (typically resolving symbolic links) and compare the
22173 entries again. @value{GDBN} already canonicalizes most of the filenames on its
22174 own before starting the comparison so a canonical form of directories is
22175 recommended to be entered.
22177 @node Auto-loading verbose mode
22178 @subsection Displaying files tried for auto-load
22179 @cindex auto-loading verbose mode
22181 For better visibility of all the file locations where you can place scripts to
22182 be auto-loaded with inferior --- or to protect yourself against accidental
22183 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
22184 all the files attempted to be loaded. Both existing and non-existing files may
22187 For example the list of directories from which it is safe to auto-load files
22188 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
22189 may not be too obvious while setting it up.
22192 (gdb) set debug auto-load on
22193 (gdb) file ~/src/t/true
22194 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
22195 for objfile "/tmp/true".
22196 auto-load: Updating directories of "/usr:/opt".
22197 auto-load: Using directory "/usr".
22198 auto-load: Using directory "/opt".
22199 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
22200 by your `auto-load safe-path' set to "/usr:/opt".
22204 @anchor{set debug auto-load}
22205 @kindex set debug auto-load
22206 @item set debug auto-load [on|off]
22207 Set whether to print the filenames attempted to be auto-loaded.
22209 @anchor{show debug auto-load}
22210 @kindex show debug auto-load
22211 @item show debug auto-load
22212 Show whether printing of the filenames attempted to be auto-loaded is turned
22216 @node Messages/Warnings
22217 @section Optional Warnings and Messages
22219 @cindex verbose operation
22220 @cindex optional warnings
22221 By default, @value{GDBN} is silent about its inner workings. If you are
22222 running on a slow machine, you may want to use the @code{set verbose}
22223 command. This makes @value{GDBN} tell you when it does a lengthy
22224 internal operation, so you will not think it has crashed.
22226 Currently, the messages controlled by @code{set verbose} are those
22227 which announce that the symbol table for a source file is being read;
22228 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22231 @kindex set verbose
22232 @item set verbose on
22233 Enables @value{GDBN} output of certain informational messages.
22235 @item set verbose off
22236 Disables @value{GDBN} output of certain informational messages.
22238 @kindex show verbose
22240 Displays whether @code{set verbose} is on or off.
22243 By default, if @value{GDBN} encounters bugs in the symbol table of an
22244 object file, it is silent; but if you are debugging a compiler, you may
22245 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22250 @kindex set complaints
22251 @item set complaints @var{limit}
22252 Permits @value{GDBN} to output @var{limit} complaints about each type of
22253 unusual symbols before becoming silent about the problem. Set
22254 @var{limit} to zero to suppress all complaints; set it to a large number
22255 to prevent complaints from being suppressed.
22257 @kindex show complaints
22258 @item show complaints
22259 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22263 @anchor{confirmation requests}
22264 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22265 lot of stupid questions to confirm certain commands. For example, if
22266 you try to run a program which is already running:
22270 The program being debugged has been started already.
22271 Start it from the beginning? (y or n)
22274 If you are willing to unflinchingly face the consequences of your own
22275 commands, you can disable this ``feature'':
22279 @kindex set confirm
22281 @cindex confirmation
22282 @cindex stupid questions
22283 @item set confirm off
22284 Disables confirmation requests. Note that running @value{GDBN} with
22285 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22286 automatically disables confirmation requests.
22288 @item set confirm on
22289 Enables confirmation requests (the default).
22291 @kindex show confirm
22293 Displays state of confirmation requests.
22297 @cindex command tracing
22298 If you need to debug user-defined commands or sourced files you may find it
22299 useful to enable @dfn{command tracing}. In this mode each command will be
22300 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22301 quantity denoting the call depth of each command.
22304 @kindex set trace-commands
22305 @cindex command scripts, debugging
22306 @item set trace-commands on
22307 Enable command tracing.
22308 @item set trace-commands off
22309 Disable command tracing.
22310 @item show trace-commands
22311 Display the current state of command tracing.
22314 @node Debugging Output
22315 @section Optional Messages about Internal Happenings
22316 @cindex optional debugging messages
22318 @value{GDBN} has commands that enable optional debugging messages from
22319 various @value{GDBN} subsystems; normally these commands are of
22320 interest to @value{GDBN} maintainers, or when reporting a bug. This
22321 section documents those commands.
22324 @kindex set exec-done-display
22325 @item set exec-done-display
22326 Turns on or off the notification of asynchronous commands'
22327 completion. When on, @value{GDBN} will print a message when an
22328 asynchronous command finishes its execution. The default is off.
22329 @kindex show exec-done-display
22330 @item show exec-done-display
22331 Displays the current setting of asynchronous command completion
22334 @cindex ARM AArch64
22335 @item set debug aarch64
22336 Turns on or off display of debugging messages related to ARM AArch64.
22337 The default is off.
22339 @item show debug aarch64
22340 Displays the current state of displaying debugging messages related to
22342 @cindex gdbarch debugging info
22343 @cindex architecture debugging info
22344 @item set debug arch
22345 Turns on or off display of gdbarch debugging info. The default is off
22346 @item show debug arch
22347 Displays the current state of displaying gdbarch debugging info.
22348 @item set debug aix-solib
22349 @cindex AIX shared library debugging
22350 Control display of debugging messages from the AIX shared library
22351 support module. The default is off.
22352 @item show debug aix-thread
22353 Show the current state of displaying AIX shared library debugging messages.
22354 @item set debug aix-thread
22355 @cindex AIX threads
22356 Display debugging messages about inner workings of the AIX thread
22358 @item show debug aix-thread
22359 Show the current state of AIX thread debugging info display.
22360 @item set debug check-physname
22362 Check the results of the ``physname'' computation. When reading DWARF
22363 debugging information for C@t{++}, @value{GDBN} attempts to compute
22364 each entity's name. @value{GDBN} can do this computation in two
22365 different ways, depending on exactly what information is present.
22366 When enabled, this setting causes @value{GDBN} to compute the names
22367 both ways and display any discrepancies.
22368 @item show debug check-physname
22369 Show the current state of ``physname'' checking.
22370 @item set debug coff-pe-read
22371 @cindex COFF/PE exported symbols
22372 Control display of debugging messages related to reading of COFF/PE
22373 exported symbols. The default is off.
22374 @item show debug coff-pe-read
22375 Displays the current state of displaying debugging messages related to
22376 reading of COFF/PE exported symbols.
22377 @item set debug dwarf2-die
22378 @cindex DWARF2 DIEs
22379 Dump DWARF2 DIEs after they are read in.
22380 The value is the number of nesting levels to print.
22381 A value of zero turns off the display.
22382 @item show debug dwarf2-die
22383 Show the current state of DWARF2 DIE debugging.
22384 @item set debug dwarf2-read
22385 @cindex DWARF2 Reading
22386 Turns on or off display of debugging messages related to reading
22387 DWARF debug info. The default is off.
22388 @item show debug dwarf2-read
22389 Show the current state of DWARF2 reader debugging.
22390 @item set debug displaced
22391 @cindex displaced stepping debugging info
22392 Turns on or off display of @value{GDBN} debugging info for the
22393 displaced stepping support. The default is off.
22394 @item show debug displaced
22395 Displays the current state of displaying @value{GDBN} debugging info
22396 related to displaced stepping.
22397 @item set debug event
22398 @cindex event debugging info
22399 Turns on or off display of @value{GDBN} event debugging info. The
22401 @item show debug event
22402 Displays the current state of displaying @value{GDBN} event debugging
22404 @item set debug expression
22405 @cindex expression debugging info
22406 Turns on or off display of debugging info about @value{GDBN}
22407 expression parsing. The default is off.
22408 @item show debug expression
22409 Displays the current state of displaying debugging info about
22410 @value{GDBN} expression parsing.
22411 @item set debug frame
22412 @cindex frame debugging info
22413 Turns on or off display of @value{GDBN} frame debugging info. The
22415 @item show debug frame
22416 Displays the current state of displaying @value{GDBN} frame debugging
22418 @item set debug gnu-nat
22419 @cindex @sc{gnu}/Hurd debug messages
22420 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22421 @item show debug gnu-nat
22422 Show the current state of @sc{gnu}/Hurd debugging messages.
22423 @item set debug infrun
22424 @cindex inferior debugging info
22425 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22426 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22427 for implementing operations such as single-stepping the inferior.
22428 @item show debug infrun
22429 Displays the current state of @value{GDBN} inferior debugging.
22430 @item set debug jit
22431 @cindex just-in-time compilation, debugging messages
22432 Turns on or off debugging messages from JIT debug support.
22433 @item show debug jit
22434 Displays the current state of @value{GDBN} JIT debugging.
22435 @item set debug lin-lwp
22436 @cindex @sc{gnu}/Linux LWP debug messages
22437 @cindex Linux lightweight processes
22438 Turns on or off debugging messages from the Linux LWP debug support.
22439 @item show debug lin-lwp
22440 Show the current state of Linux LWP debugging messages.
22441 @item set debug mach-o
22442 @cindex Mach-O symbols processing
22443 Control display of debugging messages related to Mach-O symbols
22444 processing. The default is off.
22445 @item show debug mach-o
22446 Displays the current state of displaying debugging messages related to
22447 reading of COFF/PE exported symbols.
22448 @item set debug notification
22449 @cindex remote async notification debugging info
22450 Turns on or off debugging messages about remote async notification.
22451 The default is off.
22452 @item show debug notification
22453 Displays the current state of remote async notification debugging messages.
22454 @item set debug observer
22455 @cindex observer debugging info
22456 Turns on or off display of @value{GDBN} observer debugging. This
22457 includes info such as the notification of observable events.
22458 @item show debug observer
22459 Displays the current state of observer debugging.
22460 @item set debug overload
22461 @cindex C@t{++} overload debugging info
22462 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22463 info. This includes info such as ranking of functions, etc. The default
22465 @item show debug overload
22466 Displays the current state of displaying @value{GDBN} C@t{++} overload
22468 @cindex expression parser, debugging info
22469 @cindex debug expression parser
22470 @item set debug parser
22471 Turns on or off the display of expression parser debugging output.
22472 Internally, this sets the @code{yydebug} variable in the expression
22473 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22474 details. The default is off.
22475 @item show debug parser
22476 Show the current state of expression parser debugging.
22477 @cindex packets, reporting on stdout
22478 @cindex serial connections, debugging
22479 @cindex debug remote protocol
22480 @cindex remote protocol debugging
22481 @cindex display remote packets
22482 @item set debug remote
22483 Turns on or off display of reports on all packets sent back and forth across
22484 the serial line to the remote machine. The info is printed on the
22485 @value{GDBN} standard output stream. The default is off.
22486 @item show debug remote
22487 Displays the state of display of remote packets.
22488 @item set debug serial
22489 Turns on or off display of @value{GDBN} serial debugging info. The
22491 @item show debug serial
22492 Displays the current state of displaying @value{GDBN} serial debugging
22494 @item set debug solib-frv
22495 @cindex FR-V shared-library debugging
22496 Turns on or off debugging messages for FR-V shared-library code.
22497 @item show debug solib-frv
22498 Display the current state of FR-V shared-library code debugging
22500 @item set debug symtab-create
22501 @cindex symbol table creation
22502 Turns on or off display of debugging messages related to symbol table creation.
22503 The default is off.
22504 @item show debug symtab-create
22505 Show the current state of symbol table creation debugging.
22506 @item set debug target
22507 @cindex target debugging info
22508 Turns on or off display of @value{GDBN} target debugging info. This info
22509 includes what is going on at the target level of GDB, as it happens. The
22510 default is 0. Set it to 1 to track events, and to 2 to also track the
22511 value of large memory transfers. Changes to this flag do not take effect
22512 until the next time you connect to a target or use the @code{run} command.
22513 @item show debug target
22514 Displays the current state of displaying @value{GDBN} target debugging
22516 @item set debug timestamp
22517 @cindex timestampping debugging info
22518 Turns on or off display of timestamps with @value{GDBN} debugging info.
22519 When enabled, seconds and microseconds are displayed before each debugging
22521 @item show debug timestamp
22522 Displays the current state of displaying timestamps with @value{GDBN}
22524 @item set debugvarobj
22525 @cindex variable object debugging info
22526 Turns on or off display of @value{GDBN} variable object debugging
22527 info. The default is off.
22528 @item show debugvarobj
22529 Displays the current state of displaying @value{GDBN} variable object
22531 @item set debug xml
22532 @cindex XML parser debugging
22533 Turns on or off debugging messages for built-in XML parsers.
22534 @item show debug xml
22535 Displays the current state of XML debugging messages.
22538 @node Other Misc Settings
22539 @section Other Miscellaneous Settings
22540 @cindex miscellaneous settings
22543 @kindex set interactive-mode
22544 @item set interactive-mode
22545 If @code{on}, forces @value{GDBN} to assume that GDB was started
22546 in a terminal. In practice, this means that @value{GDBN} should wait
22547 for the user to answer queries generated by commands entered at
22548 the command prompt. If @code{off}, forces @value{GDBN} to operate
22549 in the opposite mode, and it uses the default answers to all queries.
22550 If @code{auto} (the default), @value{GDBN} tries to determine whether
22551 its standard input is a terminal, and works in interactive-mode if it
22552 is, non-interactively otherwise.
22554 In the vast majority of cases, the debugger should be able to guess
22555 correctly which mode should be used. But this setting can be useful
22556 in certain specific cases, such as running a MinGW @value{GDBN}
22557 inside a cygwin window.
22559 @kindex show interactive-mode
22560 @item show interactive-mode
22561 Displays whether the debugger is operating in interactive mode or not.
22564 @node Extending GDB
22565 @chapter Extending @value{GDBN}
22566 @cindex extending GDB
22568 @value{GDBN} provides three mechanisms for extension. The first is based
22569 on composition of @value{GDBN} commands, the second is based on the
22570 Python scripting language, and the third is for defining new aliases of
22573 To facilitate the use of the first two extensions, @value{GDBN} is capable
22574 of evaluating the contents of a file. When doing so, @value{GDBN}
22575 can recognize which scripting language is being used by looking at
22576 the filename extension. Files with an unrecognized filename extension
22577 are always treated as a @value{GDBN} Command Files.
22578 @xref{Command Files,, Command files}.
22580 You can control how @value{GDBN} evaluates these files with the following
22584 @kindex set script-extension
22585 @kindex show script-extension
22586 @item set script-extension off
22587 All scripts are always evaluated as @value{GDBN} Command Files.
22589 @item set script-extension soft
22590 The debugger determines the scripting language based on filename
22591 extension. If this scripting language is supported, @value{GDBN}
22592 evaluates the script using that language. Otherwise, it evaluates
22593 the file as a @value{GDBN} Command File.
22595 @item set script-extension strict
22596 The debugger determines the scripting language based on filename
22597 extension, and evaluates the script using that language. If the
22598 language is not supported, then the evaluation fails.
22600 @item show script-extension
22601 Display the current value of the @code{script-extension} option.
22606 * Sequences:: Canned Sequences of Commands
22607 * Python:: Scripting @value{GDBN} using Python
22608 * Aliases:: Creating new spellings of existing commands
22612 @section Canned Sequences of Commands
22614 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22615 Command Lists}), @value{GDBN} provides two ways to store sequences of
22616 commands for execution as a unit: user-defined commands and command
22620 * Define:: How to define your own commands
22621 * Hooks:: Hooks for user-defined commands
22622 * Command Files:: How to write scripts of commands to be stored in a file
22623 * Output:: Commands for controlled output
22627 @subsection User-defined Commands
22629 @cindex user-defined command
22630 @cindex arguments, to user-defined commands
22631 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22632 which you assign a new name as a command. This is done with the
22633 @code{define} command. User commands may accept up to 10 arguments
22634 separated by whitespace. Arguments are accessed within the user command
22635 via @code{$arg0@dots{}$arg9}. A trivial example:
22639 print $arg0 + $arg1 + $arg2
22644 To execute the command use:
22651 This defines the command @code{adder}, which prints the sum of
22652 its three arguments. Note the arguments are text substitutions, so they may
22653 reference variables, use complex expressions, or even perform inferior
22656 @cindex argument count in user-defined commands
22657 @cindex how many arguments (user-defined commands)
22658 In addition, @code{$argc} may be used to find out how many arguments have
22659 been passed. This expands to a number in the range 0@dots{}10.
22664 print $arg0 + $arg1
22667 print $arg0 + $arg1 + $arg2
22675 @item define @var{commandname}
22676 Define a command named @var{commandname}. If there is already a command
22677 by that name, you are asked to confirm that you want to redefine it.
22678 @var{commandname} may be a bare command name consisting of letters,
22679 numbers, dashes, and underscores. It may also start with any predefined
22680 prefix command. For example, @samp{define target my-target} creates
22681 a user-defined @samp{target my-target} command.
22683 The definition of the command is made up of other @value{GDBN} command lines,
22684 which are given following the @code{define} command. The end of these
22685 commands is marked by a line containing @code{end}.
22688 @kindex end@r{ (user-defined commands)}
22689 @item document @var{commandname}
22690 Document the user-defined command @var{commandname}, so that it can be
22691 accessed by @code{help}. The command @var{commandname} must already be
22692 defined. This command reads lines of documentation just as @code{define}
22693 reads the lines of the command definition, ending with @code{end}.
22694 After the @code{document} command is finished, @code{help} on command
22695 @var{commandname} displays the documentation you have written.
22697 You may use the @code{document} command again to change the
22698 documentation of a command. Redefining the command with @code{define}
22699 does not change the documentation.
22701 @kindex dont-repeat
22702 @cindex don't repeat command
22704 Used inside a user-defined command, this tells @value{GDBN} that this
22705 command should not be repeated when the user hits @key{RET}
22706 (@pxref{Command Syntax, repeat last command}).
22708 @kindex help user-defined
22709 @item help user-defined
22710 List all user-defined commands and all python commands defined in class
22711 COMAND_USER. The first line of the documentation or docstring is
22716 @itemx show user @var{commandname}
22717 Display the @value{GDBN} commands used to define @var{commandname} (but
22718 not its documentation). If no @var{commandname} is given, display the
22719 definitions for all user-defined commands.
22720 This does not work for user-defined python commands.
22722 @cindex infinite recursion in user-defined commands
22723 @kindex show max-user-call-depth
22724 @kindex set max-user-call-depth
22725 @item show max-user-call-depth
22726 @itemx set max-user-call-depth
22727 The value of @code{max-user-call-depth} controls how many recursion
22728 levels are allowed in user-defined commands before @value{GDBN} suspects an
22729 infinite recursion and aborts the command.
22730 This does not apply to user-defined python commands.
22733 In addition to the above commands, user-defined commands frequently
22734 use control flow commands, described in @ref{Command Files}.
22736 When user-defined commands are executed, the
22737 commands of the definition are not printed. An error in any command
22738 stops execution of the user-defined command.
22740 If used interactively, commands that would ask for confirmation proceed
22741 without asking when used inside a user-defined command. Many @value{GDBN}
22742 commands that normally print messages to say what they are doing omit the
22743 messages when used in a user-defined command.
22746 @subsection User-defined Command Hooks
22747 @cindex command hooks
22748 @cindex hooks, for commands
22749 @cindex hooks, pre-command
22752 You may define @dfn{hooks}, which are a special kind of user-defined
22753 command. Whenever you run the command @samp{foo}, if the user-defined
22754 command @samp{hook-foo} exists, it is executed (with no arguments)
22755 before that command.
22757 @cindex hooks, post-command
22759 A hook may also be defined which is run after the command you executed.
22760 Whenever you run the command @samp{foo}, if the user-defined command
22761 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22762 that command. Post-execution hooks may exist simultaneously with
22763 pre-execution hooks, for the same command.
22765 It is valid for a hook to call the command which it hooks. If this
22766 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22768 @c It would be nice if hookpost could be passed a parameter indicating
22769 @c if the command it hooks executed properly or not. FIXME!
22771 @kindex stop@r{, a pseudo-command}
22772 In addition, a pseudo-command, @samp{stop} exists. Defining
22773 (@samp{hook-stop}) makes the associated commands execute every time
22774 execution stops in your program: before breakpoint commands are run,
22775 displays are printed, or the stack frame is printed.
22777 For example, to ignore @code{SIGALRM} signals while
22778 single-stepping, but treat them normally during normal execution,
22783 handle SIGALRM nopass
22787 handle SIGALRM pass
22790 define hook-continue
22791 handle SIGALRM pass
22795 As a further example, to hook at the beginning and end of the @code{echo}
22796 command, and to add extra text to the beginning and end of the message,
22804 define hookpost-echo
22808 (@value{GDBP}) echo Hello World
22809 <<<---Hello World--->>>
22814 You can define a hook for any single-word command in @value{GDBN}, but
22815 not for command aliases; you should define a hook for the basic command
22816 name, e.g.@: @code{backtrace} rather than @code{bt}.
22817 @c FIXME! So how does Joe User discover whether a command is an alias
22819 You can hook a multi-word command by adding @code{hook-} or
22820 @code{hookpost-} to the last word of the command, e.g.@:
22821 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22823 If an error occurs during the execution of your hook, execution of
22824 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22825 (before the command that you actually typed had a chance to run).
22827 If you try to define a hook which does not match any known command, you
22828 get a warning from the @code{define} command.
22830 @node Command Files
22831 @subsection Command Files
22833 @cindex command files
22834 @cindex scripting commands
22835 A command file for @value{GDBN} is a text file made of lines that are
22836 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22837 also be included. An empty line in a command file does nothing; it
22838 does not mean to repeat the last command, as it would from the
22841 You can request the execution of a command file with the @code{source}
22842 command. Note that the @code{source} command is also used to evaluate
22843 scripts that are not Command Files. The exact behavior can be configured
22844 using the @code{script-extension} setting.
22845 @xref{Extending GDB,, Extending GDB}.
22849 @cindex execute commands from a file
22850 @item source [-s] [-v] @var{filename}
22851 Execute the command file @var{filename}.
22854 The lines in a command file are generally executed sequentially,
22855 unless the order of execution is changed by one of the
22856 @emph{flow-control commands} described below. The commands are not
22857 printed as they are executed. An error in any command terminates
22858 execution of the command file and control is returned to the console.
22860 @value{GDBN} first searches for @var{filename} in the current directory.
22861 If the file is not found there, and @var{filename} does not specify a
22862 directory, then @value{GDBN} also looks for the file on the source search path
22863 (specified with the @samp{directory} command);
22864 except that @file{$cdir} is not searched because the compilation directory
22865 is not relevant to scripts.
22867 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22868 on the search path even if @var{filename} specifies a directory.
22869 The search is done by appending @var{filename} to each element of the
22870 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22871 and the search path contains @file{/home/user} then @value{GDBN} will
22872 look for the script @file{/home/user/mylib/myscript}.
22873 The search is also done if @var{filename} is an absolute path.
22874 For example, if @var{filename} is @file{/tmp/myscript} and
22875 the search path contains @file{/home/user} then @value{GDBN} will
22876 look for the script @file{/home/user/tmp/myscript}.
22877 For DOS-like systems, if @var{filename} contains a drive specification,
22878 it is stripped before concatenation. For example, if @var{filename} is
22879 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22880 will look for the script @file{c:/tmp/myscript}.
22882 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22883 each command as it is executed. The option must be given before
22884 @var{filename}, and is interpreted as part of the filename anywhere else.
22886 Commands that would ask for confirmation if used interactively proceed
22887 without asking when used in a command file. Many @value{GDBN} commands that
22888 normally print messages to say what they are doing omit the messages
22889 when called from command files.
22891 @value{GDBN} also accepts command input from standard input. In this
22892 mode, normal output goes to standard output and error output goes to
22893 standard error. Errors in a command file supplied on standard input do
22894 not terminate execution of the command file---execution continues with
22898 gdb < cmds > log 2>&1
22901 (The syntax above will vary depending on the shell used.) This example
22902 will execute commands from the file @file{cmds}. All output and errors
22903 would be directed to @file{log}.
22905 Since commands stored on command files tend to be more general than
22906 commands typed interactively, they frequently need to deal with
22907 complicated situations, such as different or unexpected values of
22908 variables and symbols, changes in how the program being debugged is
22909 built, etc. @value{GDBN} provides a set of flow-control commands to
22910 deal with these complexities. Using these commands, you can write
22911 complex scripts that loop over data structures, execute commands
22912 conditionally, etc.
22919 This command allows to include in your script conditionally executed
22920 commands. The @code{if} command takes a single argument, which is an
22921 expression to evaluate. It is followed by a series of commands that
22922 are executed only if the expression is true (its value is nonzero).
22923 There can then optionally be an @code{else} line, followed by a series
22924 of commands that are only executed if the expression was false. The
22925 end of the list is marked by a line containing @code{end}.
22929 This command allows to write loops. Its syntax is similar to
22930 @code{if}: the command takes a single argument, which is an expression
22931 to evaluate, and must be followed by the commands to execute, one per
22932 line, terminated by an @code{end}. These commands are called the
22933 @dfn{body} of the loop. The commands in the body of @code{while} are
22934 executed repeatedly as long as the expression evaluates to true.
22938 This command exits the @code{while} loop in whose body it is included.
22939 Execution of the script continues after that @code{while}s @code{end}
22942 @kindex loop_continue
22943 @item loop_continue
22944 This command skips the execution of the rest of the body of commands
22945 in the @code{while} loop in whose body it is included. Execution
22946 branches to the beginning of the @code{while} loop, where it evaluates
22947 the controlling expression.
22949 @kindex end@r{ (if/else/while commands)}
22951 Terminate the block of commands that are the body of @code{if},
22952 @code{else}, or @code{while} flow-control commands.
22957 @subsection Commands for Controlled Output
22959 During the execution of a command file or a user-defined command, normal
22960 @value{GDBN} output is suppressed; the only output that appears is what is
22961 explicitly printed by the commands in the definition. This section
22962 describes three commands useful for generating exactly the output you
22967 @item echo @var{text}
22968 @c I do not consider backslash-space a standard C escape sequence
22969 @c because it is not in ANSI.
22970 Print @var{text}. Nonprinting characters can be included in
22971 @var{text} using C escape sequences, such as @samp{\n} to print a
22972 newline. @strong{No newline is printed unless you specify one.}
22973 In addition to the standard C escape sequences, a backslash followed
22974 by a space stands for a space. This is useful for displaying a
22975 string with spaces at the beginning or the end, since leading and
22976 trailing spaces are otherwise trimmed from all arguments.
22977 To print @samp{@w{ }and foo =@w{ }}, use the command
22978 @samp{echo \@w{ }and foo = \@w{ }}.
22980 A backslash at the end of @var{text} can be used, as in C, to continue
22981 the command onto subsequent lines. For example,
22984 echo This is some text\n\
22985 which is continued\n\
22986 onto several lines.\n
22989 produces the same output as
22992 echo This is some text\n
22993 echo which is continued\n
22994 echo onto several lines.\n
22998 @item output @var{expression}
22999 Print the value of @var{expression} and nothing but that value: no
23000 newlines, no @samp{$@var{nn} = }. The value is not entered in the
23001 value history either. @xref{Expressions, ,Expressions}, for more information
23004 @item output/@var{fmt} @var{expression}
23005 Print the value of @var{expression} in format @var{fmt}. You can use
23006 the same formats as for @code{print}. @xref{Output Formats,,Output
23007 Formats}, for more information.
23010 @item printf @var{template}, @var{expressions}@dots{}
23011 Print the values of one or more @var{expressions} under the control of
23012 the string @var{template}. To print several values, make
23013 @var{expressions} be a comma-separated list of individual expressions,
23014 which may be either numbers or pointers. Their values are printed as
23015 specified by @var{template}, exactly as a C program would do by
23016 executing the code below:
23019 printf (@var{template}, @var{expressions}@dots{});
23022 As in @code{C} @code{printf}, ordinary characters in @var{template}
23023 are printed verbatim, while @dfn{conversion specification} introduced
23024 by the @samp{%} character cause subsequent @var{expressions} to be
23025 evaluated, their values converted and formatted according to type and
23026 style information encoded in the conversion specifications, and then
23029 For example, you can print two values in hex like this:
23032 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
23035 @code{printf} supports all the standard @code{C} conversion
23036 specifications, including the flags and modifiers between the @samp{%}
23037 character and the conversion letter, with the following exceptions:
23041 The argument-ordering modifiers, such as @samp{2$}, are not supported.
23044 The modifier @samp{*} is not supported for specifying precision or
23048 The @samp{'} flag (for separation of digits into groups according to
23049 @code{LC_NUMERIC'}) is not supported.
23052 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
23056 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
23059 The conversion letters @samp{a} and @samp{A} are not supported.
23063 Note that the @samp{ll} type modifier is supported only if the
23064 underlying @code{C} implementation used to build @value{GDBN} supports
23065 the @code{long long int} type, and the @samp{L} type modifier is
23066 supported only if @code{long double} type is available.
23068 As in @code{C}, @code{printf} supports simple backslash-escape
23069 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
23070 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
23071 single character. Octal and hexadecimal escape sequences are not
23074 Additionally, @code{printf} supports conversion specifications for DFP
23075 (@dfn{Decimal Floating Point}) types using the following length modifiers
23076 together with a floating point specifier.
23081 @samp{H} for printing @code{Decimal32} types.
23084 @samp{D} for printing @code{Decimal64} types.
23087 @samp{DD} for printing @code{Decimal128} types.
23090 If the underlying @code{C} implementation used to build @value{GDBN} has
23091 support for the three length modifiers for DFP types, other modifiers
23092 such as width and precision will also be available for @value{GDBN} to use.
23094 In case there is no such @code{C} support, no additional modifiers will be
23095 available and the value will be printed in the standard way.
23097 Here's an example of printing DFP types using the above conversion letters:
23099 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
23103 @item eval @var{template}, @var{expressions}@dots{}
23104 Convert the values of one or more @var{expressions} under the control of
23105 the string @var{template} to a command line, and call it.
23110 @section Scripting @value{GDBN} using Python
23111 @cindex python scripting
23112 @cindex scripting with python
23114 You can script @value{GDBN} using the @uref{http://www.python.org/,
23115 Python programming language}. This feature is available only if
23116 @value{GDBN} was configured using @option{--with-python}.
23118 @cindex python directory
23119 Python scripts used by @value{GDBN} should be installed in
23120 @file{@var{data-directory}/python}, where @var{data-directory} is
23121 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
23122 This directory, known as the @dfn{python directory},
23123 is automatically added to the Python Search Path in order to allow
23124 the Python interpreter to locate all scripts installed at this location.
23126 Additionally, @value{GDBN} commands and convenience functions which
23127 are written in Python and are located in the
23128 @file{@var{data-directory}/python/gdb/command} or
23129 @file{@var{data-directory}/python/gdb/function} directories are
23130 automatically imported when @value{GDBN} starts.
23133 * Python Commands:: Accessing Python from @value{GDBN}.
23134 * Python API:: Accessing @value{GDBN} from Python.
23135 * Python Auto-loading:: Automatically loading Python code.
23136 * Python modules:: Python modules provided by @value{GDBN}.
23139 @node Python Commands
23140 @subsection Python Commands
23141 @cindex python commands
23142 @cindex commands to access python
23144 @value{GDBN} provides two commands for accessing the Python interpreter,
23145 and one related setting:
23148 @kindex python-interactive
23150 @item python-interactive @r{[}@var{command}@r{]}
23151 @itemx pi @r{[}@var{command}@r{]}
23152 Without an argument, the @code{python-interactive} command can be used
23153 to start an interactive Python prompt. To return to @value{GDBN},
23154 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
23156 Alternatively, a single-line Python command can be given as an
23157 argument and evaluated. If the command is an expression, the result
23158 will be printed; otherwise, nothing will be printed. For example:
23161 (@value{GDBP}) python-interactive 2 + 3
23167 @item python @r{[}@var{command}@r{]}
23168 @itemx py @r{[}@var{command}@r{]}
23169 The @code{python} command can be used to evaluate Python code.
23171 If given an argument, the @code{python} command will evaluate the
23172 argument as a Python command. For example:
23175 (@value{GDBP}) python print 23
23179 If you do not provide an argument to @code{python}, it will act as a
23180 multi-line command, like @code{define}. In this case, the Python
23181 script is made up of subsequent command lines, given after the
23182 @code{python} command. This command list is terminated using a line
23183 containing @code{end}. For example:
23186 (@value{GDBP}) python
23188 End with a line saying just "end".
23194 @kindex set python print-stack
23195 @item set python print-stack
23196 By default, @value{GDBN} will print only the message component of a
23197 Python exception when an error occurs in a Python script. This can be
23198 controlled using @code{set python print-stack}: if @code{full}, then
23199 full Python stack printing is enabled; if @code{none}, then Python stack
23200 and message printing is disabled; if @code{message}, the default, only
23201 the message component of the error is printed.
23204 It is also possible to execute a Python script from the @value{GDBN}
23208 @item source @file{script-name}
23209 The script name must end with @samp{.py} and @value{GDBN} must be configured
23210 to recognize the script language based on filename extension using
23211 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
23213 @item python execfile ("script-name")
23214 This method is based on the @code{execfile} Python built-in function,
23215 and thus is always available.
23219 @subsection Python API
23221 @cindex programming in python
23223 You can get quick online help for @value{GDBN}'s Python API by issuing
23224 the command @w{@kbd{python help (gdb)}}.
23226 Functions and methods which have two or more optional arguments allow
23227 them to be specified using keyword syntax. This allows passing some
23228 optional arguments while skipping others. Example:
23229 @w{@code{gdb.some_function ('foo', bar = 1, baz = 2)}}.
23232 * Basic Python:: Basic Python Functions.
23233 * Exception Handling:: How Python exceptions are translated.
23234 * Values From Inferior:: Python representation of values.
23235 * Types In Python:: Python representation of types.
23236 * Pretty Printing API:: Pretty-printing values.
23237 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23238 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23239 * Type Printing API:: Pretty-printing types.
23240 * Frame Filter API:: Filtering Frames.
23241 * Frame Decorator API:: Decorating Frames.
23242 * Writing a Frame Filter:: Writing a Frame Filter.
23243 * Inferiors In Python:: Python representation of inferiors (processes)
23244 * Events In Python:: Listening for events from @value{GDBN}.
23245 * Threads In Python:: Accessing inferior threads from Python.
23246 * Commands In Python:: Implementing new commands in Python.
23247 * Parameters In Python:: Adding new @value{GDBN} parameters.
23248 * Functions In Python:: Writing new convenience functions.
23249 * Progspaces In Python:: Program spaces.
23250 * Objfiles In Python:: Object files.
23251 * Frames In Python:: Accessing inferior stack frames from Python.
23252 * Blocks In Python:: Accessing blocks from Python.
23253 * Symbols In Python:: Python representation of symbols.
23254 * Symbol Tables In Python:: Python representation of symbol tables.
23255 * Breakpoints In Python:: Manipulating breakpoints using Python.
23256 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23258 * Lazy Strings In Python:: Python representation of lazy strings.
23259 * Architectures In Python:: Python representation of architectures.
23263 @subsubsection Basic Python
23265 @cindex python stdout
23266 @cindex python pagination
23267 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
23268 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
23269 A Python program which outputs to one of these streams may have its
23270 output interrupted by the user (@pxref{Screen Size}). In this
23271 situation, a Python @code{KeyboardInterrupt} exception is thrown.
23273 Some care must be taken when writing Python code to run in
23274 @value{GDBN}. Two things worth noting in particular:
23278 @value{GDBN} install handlers for @code{SIGCHLD} and @code{SIGINT}.
23279 Python code must not override these, or even change the options using
23280 @code{sigaction}. If your program changes the handling of these
23281 signals, @value{GDBN} will most likely stop working correctly. Note
23282 that it is unfortunately common for GUI toolkits to install a
23283 @code{SIGCHLD} handler.
23286 @value{GDBN} takes care to mark its internal file descriptors as
23287 close-on-exec. However, this cannot be done in a thread-safe way on
23288 all platforms. Your Python programs should be aware of this and
23289 should both create new file descriptors with the close-on-exec flag
23290 set and arrange to close unneeded file descriptors before starting a
23294 @cindex python functions
23295 @cindex python module
23297 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23298 methods and classes added by @value{GDBN} are placed in this module.
23299 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23300 use in all scripts evaluated by the @code{python} command.
23302 @findex gdb.PYTHONDIR
23303 @defvar gdb.PYTHONDIR
23304 A string containing the python directory (@pxref{Python}).
23307 @findex gdb.execute
23308 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23309 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23310 If a GDB exception happens while @var{command} runs, it is
23311 translated as described in @ref{Exception Handling,,Exception Handling}.
23313 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23314 command as having originated from the user invoking it interactively.
23315 It must be a boolean value. If omitted, it defaults to @code{False}.
23317 By default, any output produced by @var{command} is sent to
23318 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23319 @code{True}, then output will be collected by @code{gdb.execute} and
23320 returned as a string. The default is @code{False}, in which case the
23321 return value is @code{None}. If @var{to_string} is @code{True}, the
23322 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23323 and height, and its pagination will be disabled; @pxref{Screen Size}.
23326 @findex gdb.breakpoints
23327 @defun gdb.breakpoints ()
23328 Return a sequence holding all of @value{GDBN}'s breakpoints.
23329 @xref{Breakpoints In Python}, for more information.
23332 @findex gdb.parameter
23333 @defun gdb.parameter (parameter)
23334 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23335 string naming the parameter to look up; @var{parameter} may contain
23336 spaces if the parameter has a multi-part name. For example,
23337 @samp{print object} is a valid parameter name.
23339 If the named parameter does not exist, this function throws a
23340 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23341 parameter's value is converted to a Python value of the appropriate
23342 type, and returned.
23345 @findex gdb.history
23346 @defun gdb.history (number)
23347 Return a value from @value{GDBN}'s value history (@pxref{Value
23348 History}). @var{number} indicates which history element to return.
23349 If @var{number} is negative, then @value{GDBN} will take its absolute value
23350 and count backward from the last element (i.e., the most recent element) to
23351 find the value to return. If @var{number} is zero, then @value{GDBN} will
23352 return the most recent element. If the element specified by @var{number}
23353 doesn't exist in the value history, a @code{gdb.error} exception will be
23356 If no exception is raised, the return value is always an instance of
23357 @code{gdb.Value} (@pxref{Values From Inferior}).
23360 @findex gdb.parse_and_eval
23361 @defun gdb.parse_and_eval (expression)
23362 Parse @var{expression} as an expression in the current language,
23363 evaluate it, and return the result as a @code{gdb.Value}.
23364 @var{expression} must be a string.
23366 This function can be useful when implementing a new command
23367 (@pxref{Commands In Python}), as it provides a way to parse the
23368 command's argument as an expression. It is also useful simply to
23369 compute values, for example, it is the only way to get the value of a
23370 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23373 @findex gdb.find_pc_line
23374 @defun gdb.find_pc_line (pc)
23375 Return the @code{gdb.Symtab_and_line} object corresponding to the
23376 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23377 value of @var{pc} is passed as an argument, then the @code{symtab} and
23378 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23379 will be @code{None} and 0 respectively.
23382 @findex gdb.post_event
23383 @defun gdb.post_event (event)
23384 Put @var{event}, a callable object taking no arguments, into
23385 @value{GDBN}'s internal event queue. This callable will be invoked at
23386 some later point, during @value{GDBN}'s event processing. Events
23387 posted using @code{post_event} will be run in the order in which they
23388 were posted; however, there is no way to know when they will be
23389 processed relative to other events inside @value{GDBN}.
23391 @value{GDBN} is not thread-safe. If your Python program uses multiple
23392 threads, you must be careful to only call @value{GDBN}-specific
23393 functions in the main @value{GDBN} thread. @code{post_event} ensures
23397 (@value{GDBP}) python
23401 > def __init__(self, message):
23402 > self.message = message;
23403 > def __call__(self):
23404 > gdb.write(self.message)
23406 >class MyThread1 (threading.Thread):
23408 > gdb.post_event(Writer("Hello "))
23410 >class MyThread2 (threading.Thread):
23412 > gdb.post_event(Writer("World\n"))
23414 >MyThread1().start()
23415 >MyThread2().start()
23417 (@value{GDBP}) Hello World
23422 @defun gdb.write (string @r{[}, stream{]})
23423 Print a string to @value{GDBN}'s paginated output stream. The
23424 optional @var{stream} determines the stream to print to. The default
23425 stream is @value{GDBN}'s standard output stream. Possible stream
23432 @value{GDBN}'s standard output stream.
23437 @value{GDBN}'s standard error stream.
23442 @value{GDBN}'s log stream (@pxref{Logging Output}).
23445 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23446 call this function and will automatically direct the output to the
23451 @defun gdb.flush ()
23452 Flush the buffer of a @value{GDBN} paginated stream so that the
23453 contents are displayed immediately. @value{GDBN} will flush the
23454 contents of a stream automatically when it encounters a newline in the
23455 buffer. The optional @var{stream} determines the stream to flush. The
23456 default stream is @value{GDBN}'s standard output stream. Possible
23463 @value{GDBN}'s standard output stream.
23468 @value{GDBN}'s standard error stream.
23473 @value{GDBN}'s log stream (@pxref{Logging Output}).
23477 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23478 call this function for the relevant stream.
23481 @findex gdb.target_charset
23482 @defun gdb.target_charset ()
23483 Return the name of the current target character set (@pxref{Character
23484 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23485 that @samp{auto} is never returned.
23488 @findex gdb.target_wide_charset
23489 @defun gdb.target_wide_charset ()
23490 Return the name of the current target wide character set
23491 (@pxref{Character Sets}). This differs from
23492 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23496 @findex gdb.solib_name
23497 @defun gdb.solib_name (address)
23498 Return the name of the shared library holding the given @var{address}
23499 as a string, or @code{None}.
23502 @findex gdb.decode_line
23503 @defun gdb.decode_line @r{[}expression@r{]}
23504 Return locations of the line specified by @var{expression}, or of the
23505 current line if no argument was given. This function returns a Python
23506 tuple containing two elements. The first element contains a string
23507 holding any unparsed section of @var{expression} (or @code{None} if
23508 the expression has been fully parsed). The second element contains
23509 either @code{None} or another tuple that contains all the locations
23510 that match the expression represented as @code{gdb.Symtab_and_line}
23511 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23512 provided, it is decoded the way that @value{GDBN}'s inbuilt
23513 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23516 @defun gdb.prompt_hook (current_prompt)
23517 @anchor{prompt_hook}
23519 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23520 assigned to this operation before a prompt is displayed by
23523 The parameter @code{current_prompt} contains the current @value{GDBN}
23524 prompt. This method must return a Python string, or @code{None}. If
23525 a string is returned, the @value{GDBN} prompt will be set to that
23526 string. If @code{None} is returned, @value{GDBN} will continue to use
23527 the current prompt.
23529 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23530 such as those used by readline for command input, and annotation
23531 related prompts are prohibited from being changed.
23534 @node Exception Handling
23535 @subsubsection Exception Handling
23536 @cindex python exceptions
23537 @cindex exceptions, python
23539 When executing the @code{python} command, Python exceptions
23540 uncaught within the Python code are translated to calls to
23541 @value{GDBN} error-reporting mechanism. If the command that called
23542 @code{python} does not handle the error, @value{GDBN} will
23543 terminate it and print an error message containing the Python
23544 exception name, the associated value, and the Python call stack
23545 backtrace at the point where the exception was raised. Example:
23548 (@value{GDBP}) python print foo
23549 Traceback (most recent call last):
23550 File "<string>", line 1, in <module>
23551 NameError: name 'foo' is not defined
23554 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23555 Python code are converted to Python exceptions. The type of the
23556 Python exception depends on the error.
23560 This is the base class for most exceptions generated by @value{GDBN}.
23561 It is derived from @code{RuntimeError}, for compatibility with earlier
23562 versions of @value{GDBN}.
23564 If an error occurring in @value{GDBN} does not fit into some more
23565 specific category, then the generated exception will have this type.
23567 @item gdb.MemoryError
23568 This is a subclass of @code{gdb.error} which is thrown when an
23569 operation tried to access invalid memory in the inferior.
23571 @item KeyboardInterrupt
23572 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23573 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23576 In all cases, your exception handler will see the @value{GDBN} error
23577 message as its value and the Python call stack backtrace at the Python
23578 statement closest to where the @value{GDBN} error occured as the
23581 @findex gdb.GdbError
23582 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23583 it is useful to be able to throw an exception that doesn't cause a
23584 traceback to be printed. For example, the user may have invoked the
23585 command incorrectly. Use the @code{gdb.GdbError} exception
23586 to handle this case. Example:
23590 >class HelloWorld (gdb.Command):
23591 > """Greet the whole world."""
23592 > def __init__ (self):
23593 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23594 > def invoke (self, args, from_tty):
23595 > argv = gdb.string_to_argv (args)
23596 > if len (argv) != 0:
23597 > raise gdb.GdbError ("hello-world takes no arguments")
23598 > print "Hello, World!"
23601 (gdb) hello-world 42
23602 hello-world takes no arguments
23605 @node Values From Inferior
23606 @subsubsection Values From Inferior
23607 @cindex values from inferior, with Python
23608 @cindex python, working with values from inferior
23610 @cindex @code{gdb.Value}
23611 @value{GDBN} provides values it obtains from the inferior program in
23612 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23613 for its internal bookkeeping of the inferior's values, and for
23614 fetching values when necessary.
23616 Inferior values that are simple scalars can be used directly in
23617 Python expressions that are valid for the value's data type. Here's
23618 an example for an integer or floating-point value @code{some_val}:
23625 As result of this, @code{bar} will also be a @code{gdb.Value} object
23626 whose values are of the same type as those of @code{some_val}.
23628 Inferior values that are structures or instances of some class can
23629 be accessed using the Python @dfn{dictionary syntax}. For example, if
23630 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23631 can access its @code{foo} element with:
23634 bar = some_val['foo']
23637 Again, @code{bar} will also be a @code{gdb.Value} object.
23639 A @code{gdb.Value} that represents a function can be executed via
23640 inferior function call. Any arguments provided to the call must match
23641 the function's prototype, and must be provided in the order specified
23644 For example, @code{some_val} is a @code{gdb.Value} instance
23645 representing a function that takes two integers as arguments. To
23646 execute this function, call it like so:
23649 result = some_val (10,20)
23652 Any values returned from a function call will be stored as a
23655 The following attributes are provided:
23657 @defvar Value.address
23658 If this object is addressable, this read-only attribute holds a
23659 @code{gdb.Value} object representing the address. Otherwise,
23660 this attribute holds @code{None}.
23663 @cindex optimized out value in Python
23664 @defvar Value.is_optimized_out
23665 This read-only boolean attribute is true if the compiler optimized out
23666 this value, thus it is not available for fetching from the inferior.
23670 The type of this @code{gdb.Value}. The value of this attribute is a
23671 @code{gdb.Type} object (@pxref{Types In Python}).
23674 @defvar Value.dynamic_type
23675 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23676 type information (@acronym{RTTI}) to determine the dynamic type of the
23677 value. If this value is of class type, it will return the class in
23678 which the value is embedded, if any. If this value is of pointer or
23679 reference to a class type, it will compute the dynamic type of the
23680 referenced object, and return a pointer or reference to that type,
23681 respectively. In all other cases, it will return the value's static
23684 Note that this feature will only work when debugging a C@t{++} program
23685 that includes @acronym{RTTI} for the object in question. Otherwise,
23686 it will just return the static type of the value as in @kbd{ptype foo}
23687 (@pxref{Symbols, ptype}).
23690 @defvar Value.is_lazy
23691 The value of this read-only boolean attribute is @code{True} if this
23692 @code{gdb.Value} has not yet been fetched from the inferior.
23693 @value{GDBN} does not fetch values until necessary, for efficiency.
23697 myval = gdb.parse_and_eval ('somevar')
23700 The value of @code{somevar} is not fetched at this time. It will be
23701 fetched when the value is needed, or when the @code{fetch_lazy}
23705 The following methods are provided:
23707 @defun Value.__init__ (@var{val})
23708 Many Python values can be converted directly to a @code{gdb.Value} via
23709 this object initializer. Specifically:
23712 @item Python boolean
23713 A Python boolean is converted to the boolean type from the current
23716 @item Python integer
23717 A Python integer is converted to the C @code{long} type for the
23718 current architecture.
23721 A Python long is converted to the C @code{long long} type for the
23722 current architecture.
23725 A Python float is converted to the C @code{double} type for the
23726 current architecture.
23728 @item Python string
23729 A Python string is converted to a target string, using the current
23732 @item @code{gdb.Value}
23733 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23735 @item @code{gdb.LazyString}
23736 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23737 Python}), then the lazy string's @code{value} method is called, and
23738 its result is used.
23742 @defun Value.cast (type)
23743 Return a new instance of @code{gdb.Value} that is the result of
23744 casting this instance to the type described by @var{type}, which must
23745 be a @code{gdb.Type} object. If the cast cannot be performed for some
23746 reason, this method throws an exception.
23749 @defun Value.dereference ()
23750 For pointer data types, this method returns a new @code{gdb.Value} object
23751 whose contents is the object pointed to by the pointer. For example, if
23752 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23759 then you can use the corresponding @code{gdb.Value} to access what
23760 @code{foo} points to like this:
23763 bar = foo.dereference ()
23766 The result @code{bar} will be a @code{gdb.Value} object holding the
23767 value pointed to by @code{foo}.
23769 A similar function @code{Value.referenced_value} exists which also
23770 returns @code{gdb.Value} objects corresonding to the values pointed to
23771 by pointer values (and additionally, values referenced by reference
23772 values). However, the behavior of @code{Value.dereference}
23773 differs from @code{Value.referenced_value} by the fact that the
23774 behavior of @code{Value.dereference} is identical to applying the C
23775 unary operator @code{*} on a given value. For example, consider a
23776 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23780 typedef int *intptr;
23784 intptr &ptrref = ptr;
23787 Though @code{ptrref} is a reference value, one can apply the method
23788 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23789 to it and obtain a @code{gdb.Value} which is identical to that
23790 corresponding to @code{val}. However, if you apply the method
23791 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23792 object identical to that corresponding to @code{ptr}.
23795 py_ptrref = gdb.parse_and_eval ("ptrref")
23796 py_val = py_ptrref.dereference ()
23797 py_ptr = py_ptrref.referenced_value ()
23800 The @code{gdb.Value} object @code{py_val} is identical to that
23801 corresponding to @code{val}, and @code{py_ptr} is identical to that
23802 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23803 be applied whenever the C unary operator @code{*} can be applied
23804 to the corresponding C value. For those cases where applying both
23805 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23806 the results obtained need not be identical (as we have seen in the above
23807 example). The results are however identical when applied on
23808 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23809 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23812 @defun Value.referenced_value ()
23813 For pointer or reference data types, this method returns a new
23814 @code{gdb.Value} object corresponding to the value referenced by the
23815 pointer/reference value. For pointer data types,
23816 @code{Value.dereference} and @code{Value.referenced_value} produce
23817 identical results. The difference between these methods is that
23818 @code{Value.dereference} cannot get the values referenced by reference
23819 values. For example, consider a reference to an @code{int}, declared
23820 in your C@t{++} program as
23828 then applying @code{Value.dereference} to the @code{gdb.Value} object
23829 corresponding to @code{ref} will result in an error, while applying
23830 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23831 identical to that corresponding to @code{val}.
23834 py_ref = gdb.parse_and_eval ("ref")
23835 er_ref = py_ref.dereference () # Results in error
23836 py_val = py_ref.referenced_value () # Returns the referenced value
23839 The @code{gdb.Value} object @code{py_val} is identical to that
23840 corresponding to @code{val}.
23843 @defun Value.dynamic_cast (type)
23844 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23845 operator were used. Consult a C@t{++} reference for details.
23848 @defun Value.reinterpret_cast (type)
23849 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23850 operator were used. Consult a C@t{++} reference for details.
23853 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23854 If this @code{gdb.Value} represents a string, then this method
23855 converts the contents to a Python string. Otherwise, this method will
23856 throw an exception.
23858 Strings are recognized in a language-specific way; whether a given
23859 @code{gdb.Value} represents a string is determined by the current
23862 For C-like languages, a value is a string if it is a pointer to or an
23863 array of characters or ints. The string is assumed to be terminated
23864 by a zero of the appropriate width. However if the optional length
23865 argument is given, the string will be converted to that given length,
23866 ignoring any embedded zeros that the string may contain.
23868 If the optional @var{encoding} argument is given, it must be a string
23869 naming the encoding of the string in the @code{gdb.Value}, such as
23870 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23871 the same encodings as the corresponding argument to Python's
23872 @code{string.decode} method, and the Python codec machinery will be used
23873 to convert the string. If @var{encoding} is not given, or if
23874 @var{encoding} is the empty string, then either the @code{target-charset}
23875 (@pxref{Character Sets}) will be used, or a language-specific encoding
23876 will be used, if the current language is able to supply one.
23878 The optional @var{errors} argument is the same as the corresponding
23879 argument to Python's @code{string.decode} method.
23881 If the optional @var{length} argument is given, the string will be
23882 fetched and converted to the given length.
23885 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23886 If this @code{gdb.Value} represents a string, then this method
23887 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23888 In Python}). Otherwise, this method will throw an exception.
23890 If the optional @var{encoding} argument is given, it must be a string
23891 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23892 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23893 @var{encoding} argument is an encoding that @value{GDBN} does
23894 recognize, @value{GDBN} will raise an error.
23896 When a lazy string is printed, the @value{GDBN} encoding machinery is
23897 used to convert the string during printing. If the optional
23898 @var{encoding} argument is not provided, or is an empty string,
23899 @value{GDBN} will automatically select the encoding most suitable for
23900 the string type. For further information on encoding in @value{GDBN}
23901 please see @ref{Character Sets}.
23903 If the optional @var{length} argument is given, the string will be
23904 fetched and encoded to the length of characters specified. If
23905 the @var{length} argument is not provided, the string will be fetched
23906 and encoded until a null of appropriate width is found.
23909 @defun Value.fetch_lazy ()
23910 If the @code{gdb.Value} object is currently a lazy value
23911 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23912 fetched from the inferior. Any errors that occur in the process
23913 will produce a Python exception.
23915 If the @code{gdb.Value} object is not a lazy value, this method
23918 This method does not return a value.
23922 @node Types In Python
23923 @subsubsection Types In Python
23924 @cindex types in Python
23925 @cindex Python, working with types
23928 @value{GDBN} represents types from the inferior using the class
23931 The following type-related functions are available in the @code{gdb}
23934 @findex gdb.lookup_type
23935 @defun gdb.lookup_type (name @r{[}, block@r{]})
23936 This function looks up a type by name. @var{name} is the name of the
23937 type to look up. It must be a string.
23939 If @var{block} is given, then @var{name} is looked up in that scope.
23940 Otherwise, it is searched for globally.
23942 Ordinarily, this function will return an instance of @code{gdb.Type}.
23943 If the named type cannot be found, it will throw an exception.
23946 If the type is a structure or class type, or an enum type, the fields
23947 of that type can be accessed using the Python @dfn{dictionary syntax}.
23948 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23949 a structure type, you can access its @code{foo} field with:
23952 bar = some_type['foo']
23955 @code{bar} will be a @code{gdb.Field} object; see below under the
23956 description of the @code{Type.fields} method for a description of the
23957 @code{gdb.Field} class.
23959 An instance of @code{Type} has the following attributes:
23962 The type code for this type. The type code will be one of the
23963 @code{TYPE_CODE_} constants defined below.
23966 @defvar Type.sizeof
23967 The size of this type, in target @code{char} units. Usually, a
23968 target's @code{char} type will be an 8-bit byte. However, on some
23969 unusual platforms, this type may have a different size.
23973 The tag name for this type. The tag name is the name after
23974 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23975 languages have this concept. If this type has no tag name, then
23976 @code{None} is returned.
23979 The following methods are provided:
23981 @defun Type.fields ()
23982 For structure and union types, this method returns the fields. Range
23983 types have two fields, the minimum and maximum values. Enum types
23984 have one field per enum constant. Function and method types have one
23985 field per parameter. The base types of C@t{++} classes are also
23986 represented as fields. If the type has no fields, or does not fit
23987 into one of these categories, an empty sequence will be returned.
23989 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23992 This attribute is not available for @code{static} fields (as in
23993 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23994 position of the field. For @code{enum} fields, the value is the
23995 enumeration member's integer representation.
23998 The name of the field, or @code{None} for anonymous fields.
24001 This is @code{True} if the field is artificial, usually meaning that
24002 it was provided by the compiler and not the user. This attribute is
24003 always provided, and is @code{False} if the field is not artificial.
24005 @item is_base_class
24006 This is @code{True} if the field represents a base class of a C@t{++}
24007 structure. This attribute is always provided, and is @code{False}
24008 if the field is not a base class of the type that is the argument of
24009 @code{fields}, or if that type was not a C@t{++} class.
24012 If the field is packed, or is a bitfield, then this will have a
24013 non-zero value, which is the size of the field in bits. Otherwise,
24014 this will be zero; in this case the field's size is given by its type.
24017 The type of the field. This is usually an instance of @code{Type},
24018 but it can be @code{None} in some situations.
24022 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
24023 Return a new @code{gdb.Type} object which represents an array of this
24024 type. If one argument is given, it is the inclusive upper bound of
24025 the array; in this case the lower bound is zero. If two arguments are
24026 given, the first argument is the lower bound of the array, and the
24027 second argument is the upper bound of the array. An array's length
24028 must not be negative, but the bounds can be.
24031 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
24032 Return a new @code{gdb.Type} object which represents a vector of this
24033 type. If one argument is given, it is the inclusive upper bound of
24034 the vector; in this case the lower bound is zero. If two arguments are
24035 given, the first argument is the lower bound of the vector, and the
24036 second argument is the upper bound of the vector. A vector's length
24037 must not be negative, but the bounds can be.
24039 The difference between an @code{array} and a @code{vector} is that
24040 arrays behave like in C: when used in expressions they decay to a pointer
24041 to the first element whereas vectors are treated as first class values.
24044 @defun Type.const ()
24045 Return a new @code{gdb.Type} object which represents a
24046 @code{const}-qualified variant of this type.
24049 @defun Type.volatile ()
24050 Return a new @code{gdb.Type} object which represents a
24051 @code{volatile}-qualified variant of this type.
24054 @defun Type.unqualified ()
24055 Return a new @code{gdb.Type} object which represents an unqualified
24056 variant of this type. That is, the result is neither @code{const} nor
24060 @defun Type.range ()
24061 Return a Python @code{Tuple} object that contains two elements: the
24062 low bound of the argument type and the high bound of that type. If
24063 the type does not have a range, @value{GDBN} will raise a
24064 @code{gdb.error} exception (@pxref{Exception Handling}).
24067 @defun Type.reference ()
24068 Return a new @code{gdb.Type} object which represents a reference to this
24072 @defun Type.pointer ()
24073 Return a new @code{gdb.Type} object which represents a pointer to this
24077 @defun Type.strip_typedefs ()
24078 Return a new @code{gdb.Type} that represents the real type,
24079 after removing all layers of typedefs.
24082 @defun Type.target ()
24083 Return a new @code{gdb.Type} object which represents the target type
24086 For a pointer type, the target type is the type of the pointed-to
24087 object. For an array type (meaning C-like arrays), the target type is
24088 the type of the elements of the array. For a function or method type,
24089 the target type is the type of the return value. For a complex type,
24090 the target type is the type of the elements. For a typedef, the
24091 target type is the aliased type.
24093 If the type does not have a target, this method will throw an
24097 @defun Type.template_argument (n @r{[}, block@r{]})
24098 If this @code{gdb.Type} is an instantiation of a template, this will
24099 return a new @code{gdb.Type} which represents the type of the
24100 @var{n}th template argument.
24102 If this @code{gdb.Type} is not a template type, this will throw an
24103 exception. Ordinarily, only C@t{++} code will have template types.
24105 If @var{block} is given, then @var{name} is looked up in that scope.
24106 Otherwise, it is searched for globally.
24110 Each type has a code, which indicates what category this type falls
24111 into. The available type categories are represented by constants
24112 defined in the @code{gdb} module:
24115 @findex TYPE_CODE_PTR
24116 @findex gdb.TYPE_CODE_PTR
24117 @item gdb.TYPE_CODE_PTR
24118 The type is a pointer.
24120 @findex TYPE_CODE_ARRAY
24121 @findex gdb.TYPE_CODE_ARRAY
24122 @item gdb.TYPE_CODE_ARRAY
24123 The type is an array.
24125 @findex TYPE_CODE_STRUCT
24126 @findex gdb.TYPE_CODE_STRUCT
24127 @item gdb.TYPE_CODE_STRUCT
24128 The type is a structure.
24130 @findex TYPE_CODE_UNION
24131 @findex gdb.TYPE_CODE_UNION
24132 @item gdb.TYPE_CODE_UNION
24133 The type is a union.
24135 @findex TYPE_CODE_ENUM
24136 @findex gdb.TYPE_CODE_ENUM
24137 @item gdb.TYPE_CODE_ENUM
24138 The type is an enum.
24140 @findex TYPE_CODE_FLAGS
24141 @findex gdb.TYPE_CODE_FLAGS
24142 @item gdb.TYPE_CODE_FLAGS
24143 A bit flags type, used for things such as status registers.
24145 @findex TYPE_CODE_FUNC
24146 @findex gdb.TYPE_CODE_FUNC
24147 @item gdb.TYPE_CODE_FUNC
24148 The type is a function.
24150 @findex TYPE_CODE_INT
24151 @findex gdb.TYPE_CODE_INT
24152 @item gdb.TYPE_CODE_INT
24153 The type is an integer type.
24155 @findex TYPE_CODE_FLT
24156 @findex gdb.TYPE_CODE_FLT
24157 @item gdb.TYPE_CODE_FLT
24158 A floating point type.
24160 @findex TYPE_CODE_VOID
24161 @findex gdb.TYPE_CODE_VOID
24162 @item gdb.TYPE_CODE_VOID
24163 The special type @code{void}.
24165 @findex TYPE_CODE_SET
24166 @findex gdb.TYPE_CODE_SET
24167 @item gdb.TYPE_CODE_SET
24170 @findex TYPE_CODE_RANGE
24171 @findex gdb.TYPE_CODE_RANGE
24172 @item gdb.TYPE_CODE_RANGE
24173 A range type, that is, an integer type with bounds.
24175 @findex TYPE_CODE_STRING
24176 @findex gdb.TYPE_CODE_STRING
24177 @item gdb.TYPE_CODE_STRING
24178 A string type. Note that this is only used for certain languages with
24179 language-defined string types; C strings are not represented this way.
24181 @findex TYPE_CODE_BITSTRING
24182 @findex gdb.TYPE_CODE_BITSTRING
24183 @item gdb.TYPE_CODE_BITSTRING
24184 A string of bits. It is deprecated.
24186 @findex TYPE_CODE_ERROR
24187 @findex gdb.TYPE_CODE_ERROR
24188 @item gdb.TYPE_CODE_ERROR
24189 An unknown or erroneous type.
24191 @findex TYPE_CODE_METHOD
24192 @findex gdb.TYPE_CODE_METHOD
24193 @item gdb.TYPE_CODE_METHOD
24194 A method type, as found in C@t{++} or Java.
24196 @findex TYPE_CODE_METHODPTR
24197 @findex gdb.TYPE_CODE_METHODPTR
24198 @item gdb.TYPE_CODE_METHODPTR
24199 A pointer-to-member-function.
24201 @findex TYPE_CODE_MEMBERPTR
24202 @findex gdb.TYPE_CODE_MEMBERPTR
24203 @item gdb.TYPE_CODE_MEMBERPTR
24204 A pointer-to-member.
24206 @findex TYPE_CODE_REF
24207 @findex gdb.TYPE_CODE_REF
24208 @item gdb.TYPE_CODE_REF
24211 @findex TYPE_CODE_CHAR
24212 @findex gdb.TYPE_CODE_CHAR
24213 @item gdb.TYPE_CODE_CHAR
24216 @findex TYPE_CODE_BOOL
24217 @findex gdb.TYPE_CODE_BOOL
24218 @item gdb.TYPE_CODE_BOOL
24221 @findex TYPE_CODE_COMPLEX
24222 @findex gdb.TYPE_CODE_COMPLEX
24223 @item gdb.TYPE_CODE_COMPLEX
24224 A complex float type.
24226 @findex TYPE_CODE_TYPEDEF
24227 @findex gdb.TYPE_CODE_TYPEDEF
24228 @item gdb.TYPE_CODE_TYPEDEF
24229 A typedef to some other type.
24231 @findex TYPE_CODE_NAMESPACE
24232 @findex gdb.TYPE_CODE_NAMESPACE
24233 @item gdb.TYPE_CODE_NAMESPACE
24234 A C@t{++} namespace.
24236 @findex TYPE_CODE_DECFLOAT
24237 @findex gdb.TYPE_CODE_DECFLOAT
24238 @item gdb.TYPE_CODE_DECFLOAT
24239 A decimal floating point type.
24241 @findex TYPE_CODE_INTERNAL_FUNCTION
24242 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
24243 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
24244 A function internal to @value{GDBN}. This is the type used to represent
24245 convenience functions.
24248 Further support for types is provided in the @code{gdb.types}
24249 Python module (@pxref{gdb.types}).
24251 @node Pretty Printing API
24252 @subsubsection Pretty Printing API
24254 An example output is provided (@pxref{Pretty Printing}).
24256 A pretty-printer is just an object that holds a value and implements a
24257 specific interface, defined here.
24259 @defun pretty_printer.children (self)
24260 @value{GDBN} will call this method on a pretty-printer to compute the
24261 children of the pretty-printer's value.
24263 This method must return an object conforming to the Python iterator
24264 protocol. Each item returned by the iterator must be a tuple holding
24265 two elements. The first element is the ``name'' of the child; the
24266 second element is the child's value. The value can be any Python
24267 object which is convertible to a @value{GDBN} value.
24269 This method is optional. If it does not exist, @value{GDBN} will act
24270 as though the value has no children.
24273 @defun pretty_printer.display_hint (self)
24274 The CLI may call this method and use its result to change the
24275 formatting of a value. The result will also be supplied to an MI
24276 consumer as a @samp{displayhint} attribute of the variable being
24279 This method is optional. If it does exist, this method must return a
24282 Some display hints are predefined by @value{GDBN}:
24286 Indicate that the object being printed is ``array-like''. The CLI
24287 uses this to respect parameters such as @code{set print elements} and
24288 @code{set print array}.
24291 Indicate that the object being printed is ``map-like'', and that the
24292 children of this value can be assumed to alternate between keys and
24296 Indicate that the object being printed is ``string-like''. If the
24297 printer's @code{to_string} method returns a Python string of some
24298 kind, then @value{GDBN} will call its internal language-specific
24299 string-printing function to format the string. For the CLI this means
24300 adding quotation marks, possibly escaping some characters, respecting
24301 @code{set print elements}, and the like.
24305 @defun pretty_printer.to_string (self)
24306 @value{GDBN} will call this method to display the string
24307 representation of the value passed to the object's constructor.
24309 When printing from the CLI, if the @code{to_string} method exists,
24310 then @value{GDBN} will prepend its result to the values returned by
24311 @code{children}. Exactly how this formatting is done is dependent on
24312 the display hint, and may change as more hints are added. Also,
24313 depending on the print settings (@pxref{Print Settings}), the CLI may
24314 print just the result of @code{to_string} in a stack trace, omitting
24315 the result of @code{children}.
24317 If this method returns a string, it is printed verbatim.
24319 Otherwise, if this method returns an instance of @code{gdb.Value},
24320 then @value{GDBN} prints this value. This may result in a call to
24321 another pretty-printer.
24323 If instead the method returns a Python value which is convertible to a
24324 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24325 the resulting value. Again, this may result in a call to another
24326 pretty-printer. Python scalars (integers, floats, and booleans) and
24327 strings are convertible to @code{gdb.Value}; other types are not.
24329 Finally, if this method returns @code{None} then no further operations
24330 are peformed in this method and nothing is printed.
24332 If the result is not one of these types, an exception is raised.
24335 @value{GDBN} provides a function which can be used to look up the
24336 default pretty-printer for a @code{gdb.Value}:
24338 @findex gdb.default_visualizer
24339 @defun gdb.default_visualizer (value)
24340 This function takes a @code{gdb.Value} object as an argument. If a
24341 pretty-printer for this value exists, then it is returned. If no such
24342 printer exists, then this returns @code{None}.
24345 @node Selecting Pretty-Printers
24346 @subsubsection Selecting Pretty-Printers
24348 The Python list @code{gdb.pretty_printers} contains an array of
24349 functions or callable objects that have been registered via addition
24350 as a pretty-printer. Printers in this list are called @code{global}
24351 printers, they're available when debugging all inferiors.
24352 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24353 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24356 Each function on these lists is passed a single @code{gdb.Value}
24357 argument and should return a pretty-printer object conforming to the
24358 interface definition above (@pxref{Pretty Printing API}). If a function
24359 cannot create a pretty-printer for the value, it should return
24362 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24363 @code{gdb.Objfile} in the current program space and iteratively calls
24364 each enabled lookup routine in the list for that @code{gdb.Objfile}
24365 until it receives a pretty-printer object.
24366 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24367 searches the pretty-printer list of the current program space,
24368 calling each enabled function until an object is returned.
24369 After these lists have been exhausted, it tries the global
24370 @code{gdb.pretty_printers} list, again calling each enabled function until an
24371 object is returned.
24373 The order in which the objfiles are searched is not specified. For a
24374 given list, functions are always invoked from the head of the list,
24375 and iterated over sequentially until the end of the list, or a printer
24376 object is returned.
24378 For various reasons a pretty-printer may not work.
24379 For example, the underlying data structure may have changed and
24380 the pretty-printer is out of date.
24382 The consequences of a broken pretty-printer are severe enough that
24383 @value{GDBN} provides support for enabling and disabling individual
24384 printers. For example, if @code{print frame-arguments} is on,
24385 a backtrace can become highly illegible if any argument is printed
24386 with a broken printer.
24388 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24389 attribute to the registered function or callable object. If this attribute
24390 is present and its value is @code{False}, the printer is disabled, otherwise
24391 the printer is enabled.
24393 @node Writing a Pretty-Printer
24394 @subsubsection Writing a Pretty-Printer
24395 @cindex writing a pretty-printer
24397 A pretty-printer consists of two parts: a lookup function to detect
24398 if the type is supported, and the printer itself.
24400 Here is an example showing how a @code{std::string} printer might be
24401 written. @xref{Pretty Printing API}, for details on the API this class
24405 class StdStringPrinter(object):
24406 "Print a std::string"
24408 def __init__(self, val):
24411 def to_string(self):
24412 return self.val['_M_dataplus']['_M_p']
24414 def display_hint(self):
24418 And here is an example showing how a lookup function for the printer
24419 example above might be written.
24422 def str_lookup_function(val):
24423 lookup_tag = val.type.tag
24424 if lookup_tag == None:
24426 regex = re.compile("^std::basic_string<char,.*>$")
24427 if regex.match(lookup_tag):
24428 return StdStringPrinter(val)
24432 The example lookup function extracts the value's type, and attempts to
24433 match it to a type that it can pretty-print. If it is a type the
24434 printer can pretty-print, it will return a printer object. If not, it
24435 returns @code{None}.
24437 We recommend that you put your core pretty-printers into a Python
24438 package. If your pretty-printers are for use with a library, we
24439 further recommend embedding a version number into the package name.
24440 This practice will enable @value{GDBN} to load multiple versions of
24441 your pretty-printers at the same time, because they will have
24444 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24445 can be evaluated multiple times without changing its meaning. An
24446 ideal auto-load file will consist solely of @code{import}s of your
24447 printer modules, followed by a call to a register pretty-printers with
24448 the current objfile.
24450 Taken as a whole, this approach will scale nicely to multiple
24451 inferiors, each potentially using a different library version.
24452 Embedding a version number in the Python package name will ensure that
24453 @value{GDBN} is able to load both sets of printers simultaneously.
24454 Then, because the search for pretty-printers is done by objfile, and
24455 because your auto-loaded code took care to register your library's
24456 printers with a specific objfile, @value{GDBN} will find the correct
24457 printers for the specific version of the library used by each
24460 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24461 this code might appear in @code{gdb.libstdcxx.v6}:
24464 def register_printers(objfile):
24465 objfile.pretty_printers.append(str_lookup_function)
24469 And then the corresponding contents of the auto-load file would be:
24472 import gdb.libstdcxx.v6
24473 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24476 The previous example illustrates a basic pretty-printer.
24477 There are a few things that can be improved on.
24478 The printer doesn't have a name, making it hard to identify in a
24479 list of installed printers. The lookup function has a name, but
24480 lookup functions can have arbitrary, even identical, names.
24482 Second, the printer only handles one type, whereas a library typically has
24483 several types. One could install a lookup function for each desired type
24484 in the library, but one could also have a single lookup function recognize
24485 several types. The latter is the conventional way this is handled.
24486 If a pretty-printer can handle multiple data types, then its
24487 @dfn{subprinters} are the printers for the individual data types.
24489 The @code{gdb.printing} module provides a formal way of solving these
24490 problems (@pxref{gdb.printing}).
24491 Here is another example that handles multiple types.
24493 These are the types we are going to pretty-print:
24496 struct foo @{ int a, b; @};
24497 struct bar @{ struct foo x, y; @};
24500 Here are the printers:
24504 """Print a foo object."""
24506 def __init__(self, val):
24509 def to_string(self):
24510 return ("a=<" + str(self.val["a"]) +
24511 "> b=<" + str(self.val["b"]) + ">")
24514 """Print a bar object."""
24516 def __init__(self, val):
24519 def to_string(self):
24520 return ("x=<" + str(self.val["x"]) +
24521 "> y=<" + str(self.val["y"]) + ">")
24524 This example doesn't need a lookup function, that is handled by the
24525 @code{gdb.printing} module. Instead a function is provided to build up
24526 the object that handles the lookup.
24529 import gdb.printing
24531 def build_pretty_printer():
24532 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24534 pp.add_printer('foo', '^foo$', fooPrinter)
24535 pp.add_printer('bar', '^bar$', barPrinter)
24539 And here is the autoload support:
24542 import gdb.printing
24544 gdb.printing.register_pretty_printer(
24545 gdb.current_objfile(),
24546 my_library.build_pretty_printer())
24549 Finally, when this printer is loaded into @value{GDBN}, here is the
24550 corresponding output of @samp{info pretty-printer}:
24553 (gdb) info pretty-printer
24560 @node Type Printing API
24561 @subsubsection Type Printing API
24562 @cindex type printing API for Python
24564 @value{GDBN} provides a way for Python code to customize type display.
24565 This is mainly useful for substituting canonical typedef names for
24568 @cindex type printer
24569 A @dfn{type printer} is just a Python object conforming to a certain
24570 protocol. A simple base class implementing the protocol is provided;
24571 see @ref{gdb.types}. A type printer must supply at least:
24573 @defivar type_printer enabled
24574 A boolean which is True if the printer is enabled, and False
24575 otherwise. This is manipulated by the @code{enable type-printer}
24576 and @code{disable type-printer} commands.
24579 @defivar type_printer name
24580 The name of the type printer. This must be a string. This is used by
24581 the @code{enable type-printer} and @code{disable type-printer}
24585 @defmethod type_printer instantiate (self)
24586 This is called by @value{GDBN} at the start of type-printing. It is
24587 only called if the type printer is enabled. This method must return a
24588 new object that supplies a @code{recognize} method, as described below.
24592 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24593 will compute a list of type recognizers. This is done by iterating
24594 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24595 followed by the per-progspace type printers (@pxref{Progspaces In
24596 Python}), and finally the global type printers.
24598 @value{GDBN} will call the @code{instantiate} method of each enabled
24599 type printer. If this method returns @code{None}, then the result is
24600 ignored; otherwise, it is appended to the list of recognizers.
24602 Then, when @value{GDBN} is going to display a type name, it iterates
24603 over the list of recognizers. For each one, it calls the recognition
24604 function, stopping if the function returns a non-@code{None} value.
24605 The recognition function is defined as:
24607 @defmethod type_recognizer recognize (self, type)
24608 If @var{type} is not recognized, return @code{None}. Otherwise,
24609 return a string which is to be printed as the name of @var{type}.
24610 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24614 @value{GDBN} uses this two-pass approach so that type printers can
24615 efficiently cache information without holding on to it too long. For
24616 example, it can be convenient to look up type information in a type
24617 printer and hold it for a recognizer's lifetime; if a single pass were
24618 done then type printers would have to make use of the event system in
24619 order to avoid holding information that could become stale as the
24622 @node Frame Filter API
24623 @subsubsection Filtering Frames.
24624 @cindex frame filters api
24626 Frame filters are Python objects that manipulate the visibility of a
24627 frame or frames when a backtrace (@pxref{Backtrace}) is printed by
24630 Only commands that print a backtrace, or, in the case of @sc{gdb/mi}
24631 commands (@pxref{GDB/MI}), those that return a collection of frames
24632 are affected. The commands that work with frame filters are:
24634 @code{backtrace} (@pxref{backtrace-command,, The backtrace command}),
24635 @code{-stack-list-frames}
24636 (@pxref{-stack-list-frames,, The -stack-list-frames command}),
24637 @code{-stack-list-variables} (@pxref{-stack-list-variables,, The
24638 -stack-list-variables command}), @code{-stack-list-arguments}
24639 @pxref{-stack-list-arguments,, The -stack-list-arguments command}) and
24640 @code{-stack-list-locals} (@pxref{-stack-list-locals,, The
24641 -stack-list-locals command}).
24643 A frame filter works by taking an iterator as an argument, applying
24644 actions to the contents of that iterator, and returning another
24645 iterator (or, possibly, the same iterator it was provided in the case
24646 where the filter does not perform any operations). Typically, frame
24647 filters utilize tools such as the Python's @code{itertools} module to
24648 work with and create new iterators from the source iterator.
24649 Regardless of how a filter chooses to apply actions, it must not alter
24650 the underlying @value{GDBN} frame or frames, or attempt to alter the
24651 call-stack within @value{GDBN}. This preserves data integrity within
24652 @value{GDBN}. Frame filters are executed on a priority basis and care
24653 should be taken that some frame filters may have been executed before,
24654 and that some frame filters will be executed after.
24656 An important consideration when designing frame filters, and well
24657 worth reflecting upon, is that frame filters should avoid unwinding
24658 the call stack if possible. Some stacks can run very deep, into the
24659 tens of thousands in some cases. To search every frame when a frame
24660 filter executes may be too expensive at that step. The frame filter
24661 cannot know how many frames it has to iterate over, and it may have to
24662 iterate through them all. This ends up duplicating effort as
24663 @value{GDBN} performs this iteration when it prints the frames. If
24664 the filter can defer unwinding frames until frame decorators are
24665 executed, after the last filter has executed, it should. @xref{Frame
24666 Decorator API}, for more information on decorators. Also, there are
24667 examples for both frame decorators and filters in later chapters.
24668 @xref{Writing a Frame Filter}, for more information.
24670 The Python dictionary @code{gdb.frame_filters} contains key/object
24671 pairings that comprise a frame filter. Frame filters in this
24672 dictionary are called @code{global} frame filters, and they are
24673 available when debugging all inferiors. These frame filters must
24674 register with the dictionary directly. In addition to the
24675 @code{global} dictionary, there are other dictionaries that are loaded
24676 with different inferiors via auto-loading (@pxref{Python
24677 Auto-loading}). The two other areas where frame filter dictionaries
24678 can be found are: @code{gdb.Progspace} which contains a
24679 @code{frame_filters} dictionary attribute, and each @code{gdb.Objfile}
24680 object which also contains a @code{frame_filters} dictionary
24683 When a command is executed from @value{GDBN} that is compatible with
24684 frame filters, @value{GDBN} combines the @code{global},
24685 @code{gdb.Progspace} and all @code{gdb.Objfile} dictionaries currently
24686 loaded. All of the @code{gdb.Objfile} dictionaries are combined, as
24687 several frames, and thus several object files, might be in use.
24688 @value{GDBN} then prunes any frame filter whose @code{enabled}
24689 attribute is @code{False}. This pruned list is then sorted according
24690 to the @code{priority} attribute in each filter.
24692 Once the dictionaries are combined, pruned and sorted, @value{GDBN}
24693 creates an iterator which wraps each frame in the call stack in a
24694 @code{FrameDecorator} object, and calls each filter in order. The
24695 output from the previous filter will always be the input to the next
24698 Frame filters have a mandatory interface which each frame filter must
24699 implement, defined here:
24701 @defun FrameFilter.filter (iterator)
24702 @value{GDBN} will call this method on a frame filter when it has
24703 reached the order in the priority list for that filter.
24705 For example, if there are four frame filters:
24716 The order that the frame filters will be called is:
24719 Filter3 -> Filter2 -> Filter1 -> Filter4
24722 Note that the output from @code{Filter3} is passed to the input of
24723 @code{Filter2}, and so on.
24725 This @code{filter} method is passed a Python iterator. This iterator
24726 contains a sequence of frame decorators that wrap each
24727 @code{gdb.Frame}, or a frame decorator that wraps another frame
24728 decorator. The first filter that is executed in the sequence of frame
24729 filters will receive an iterator entirely comprised of default
24730 @code{FrameDecorator} objects. However, after each frame filter is
24731 executed, the previous frame filter may have wrapped some or all of
24732 the frame decorators with their own frame decorator. As frame
24733 decorators must also conform to a mandatory interface, these
24734 decorators can be assumed to act in a uniform manner (@pxref{Frame
24737 This method must return an object conforming to the Python iterator
24738 protocol. Each item in the iterator must be an object conforming to
24739 the frame decorator interface. If a frame filter does not wish to
24740 perform any operations on this iterator, it should return that
24741 iterator untouched.
24743 This method is not optional. If it does not exist, @value{GDBN} will
24744 raise and print an error.
24747 @defvar FrameFilter.name
24748 The @code{name} attribute must be Python string which contains the
24749 name of the filter displayed by @value{GDBN} (@pxref{Frame Filter
24750 Management}). This attribute may contain any combination of letters
24751 or numbers. Care should be taken to ensure that it is unique. This
24752 attribute is mandatory.
24755 @defvar FrameFilter.enabled
24756 The @code{enabled} attribute must be Python boolean. This attribute
24757 indicates to @value{GDBN} whether the frame filter is enabled, and
24758 should be considered when frame filters are executed. If
24759 @code{enabled} is @code{True}, then the frame filter will be executed
24760 when any of the backtrace commands detailed earlier in this chapter
24761 are executed. If @code{enabled} is @code{False}, then the frame
24762 filter will not be executed. This attribute is mandatory.
24765 @defvar FrameFilter.priority
24766 The @code{priority} attribute must be Python integer. This attribute
24767 controls the order of execution in relation to other frame filters.
24768 There are no imposed limits on the range of @code{priority} other than
24769 it must be a valid integer. The higher the @code{priority} attribute,
24770 the sooner the frame filter will be executed in relation to other
24771 frame filters. Although @code{priority} can be negative, it is
24772 recommended practice to assume zero is the lowest priority that a
24773 frame filter can be assigned. Frame filters that have the same
24774 priority are executed in unsorted order in that priority slot. This
24775 attribute is mandatory.
24778 @node Frame Decorator API
24779 @subsubsection Decorating Frames.
24780 @cindex frame decorator api
24782 Frame decorators are sister objects to frame filters (@pxref{Frame
24783 Filter API}). Frame decorators are applied by a frame filter and can
24784 only be used in conjunction with frame filters.
24786 The purpose of a frame decorator is to customize the printed content
24787 of each @code{gdb.Frame} in commands where frame filters are executed.
24788 This concept is called decorating a frame. Frame decorators decorate
24789 a @code{gdb.Frame} with Python code contained within each API call.
24790 This separates the actual data contained in a @code{gdb.Frame} from
24791 the decorated data produced by a frame decorator. This abstraction is
24792 necessary to maintain integrity of the data contained in each
24795 Frame decorators have a mandatory interface, defined below.
24797 @value{GDBN} already contains a frame decorator called
24798 @code{FrameDecorator}. This contains substantial amounts of
24799 boilerplate code to decorate the content of a @code{gdb.Frame}. It is
24800 recommended that other frame decorators inherit and extend this
24801 object, and only to override the methods needed.
24803 @defun FrameDecorator.elided (self)
24805 The @code{elided} method groups frames together in a hierarchical
24806 system. An example would be an interpreter, where multiple low-level
24807 frames make up a single call in the interpreted language. In this
24808 example, the frame filter would elide the low-level frames and present
24809 a single high-level frame, representing the call in the interpreted
24810 language, to the user.
24812 The @code{elided} function must return an iterable and this iterable
24813 must contain the frames that are being elided wrapped in a suitable
24814 frame decorator. If no frames are being elided this function may
24815 return an empty iterable, or @code{None}. Elided frames are indented
24816 from normal frames in a @code{CLI} backtrace, or in the case of
24817 @code{GDB/MI}, are placed in the @code{children} field of the eliding
24820 It is the frame filter's task to also filter out the elided frames from
24821 the source iterator. This will avoid printing the frame twice.
24824 @defun FrameDecorator.function (self)
24826 This method returns the name of the function in the frame that is to
24829 This method must return a Python string describing the function, or
24832 If this function returns @code{None}, @value{GDBN} will not print any
24833 data for this field.
24836 @defun FrameDecorator.address (self)
24838 This method returns the address of the frame that is to be printed.
24840 This method must return a Python numeric integer type of sufficient
24841 size to describe the address of the frame, or @code{None}.
24843 If this function returns a @code{None}, @value{GDBN} will not print
24844 any data for this field.
24847 @defun FrameDecorator.filename (self)
24849 This method returns the filename and path associated with this frame.
24851 This method must return a Python string containing the filename and
24852 the path to the object file backing the frame, or @code{None}.
24854 If this function returns a @code{None}, @value{GDBN} will not print
24855 any data for this field.
24858 @defun FrameDecorator.line (self):
24860 This method returns the line number associated with the current
24861 position within the function addressed by this frame.
24863 This method must return a Python integer type, or @code{None}.
24865 If this function returns a @code{None}, @value{GDBN} will not print
24866 any data for this field.
24869 @defun FrameDecorator.frame_args (self)
24870 @anchor{frame_args}
24872 This method must return an iterable, or @code{None}. Returning an
24873 empty iterable, or @code{None} means frame arguments will not be
24874 printed for this frame. This iterable must contain objects that
24875 implement two methods, described here.
24877 This object must implement a @code{argument} method which takes a
24878 single @code{self} parameter and must return a @code{gdb.Symbol}
24879 (@pxref{Symbols In Python}), or a Python string. The object must also
24880 implement a @code{value} method which takes a single @code{self}
24881 parameter and must return a @code{gdb.Value} (@pxref{Values From
24882 Inferior}), a Python value, or @code{None}. If the @code{value}
24883 method returns @code{None}, and the @code{argument} method returns a
24884 @code{gdb.Symbol}, @value{GDBN} will look-up and print the value of
24885 the @code{gdb.Symbol} automatically.
24890 class SymValueWrapper():
24892 def __init__(self, symbol, value):
24902 class SomeFrameDecorator()
24905 def frame_args(self):
24908 block = self.inferior_frame.block()
24912 # Iterate over all symbols in a block. Only add
24913 # symbols that are arguments.
24915 if not sym.is_argument:
24917 args.append(SymValueWrapper(sym,None))
24919 # Add example synthetic argument.
24920 args.append(SymValueWrapper(``foo'', 42))
24926 @defun FrameDecorator.frame_locals (self)
24928 This method must return an iterable or @code{None}. Returning an
24929 empty iterable, or @code{None} means frame local arguments will not be
24930 printed for this frame.
24932 The object interface, the description of the various strategies for
24933 reading frame locals, and the example are largely similar to those
24934 described in the @code{frame_args} function, (@pxref{frame_args,,The
24935 frame filter frame_args function}). Below is a modified example:
24938 class SomeFrameDecorator()
24941 def frame_locals(self):
24944 block = self.inferior_frame.block()
24948 # Iterate over all symbols in a block. Add all
24949 # symbols, except arguments.
24951 if sym.is_argument:
24953 vars.append(SymValueWrapper(sym,None))
24955 # Add an example of a synthetic local variable.
24956 vars.append(SymValueWrapper(``bar'', 99))
24962 @defun FrameDecorator.inferior_frame (self):
24964 This method must return the underlying @code{gdb.Frame} that this
24965 frame decorator is decorating. @value{GDBN} requires the underlying
24966 frame for internal frame information to determine how to print certain
24967 values when printing a frame.
24970 @node Writing a Frame Filter
24971 @subsubsection Writing a Frame Filter
24972 @cindex writing a frame filter
24974 There are three basic elements that a frame filter must implement: it
24975 must correctly implement the documented interface (@pxref{Frame Filter
24976 API}), it must register itself with @value{GDBN}, and finally, it must
24977 decide if it is to work on the data provided by @value{GDBN}. In all
24978 cases, whether it works on the iterator or not, each frame filter must
24979 return an iterator. A bare-bones frame filter follows the pattern in
24980 the following example.
24985 class FrameFilter():
24987 def __init__(self):
24988 # Frame filter attribute creation.
24990 # 'name' is the name of the filter that GDB will display.
24992 # 'priority' is the priority of the filter relative to other
24995 # 'enabled' is a boolean that indicates whether this filter is
24996 # enabled and should be executed.
24999 self.priority = 100
25000 self.enabled = True
25002 # Register this frame filter with the global frame_filters
25004 gdb.frame_filters[self.name] = self
25006 def filter(self, frame_iter):
25007 # Just return the iterator.
25011 The frame filter in the example above implements the three
25012 requirements for all frame filters. It implements the API, self
25013 registers, and makes a decision on the iterator (in this case, it just
25014 returns the iterator untouched).
25016 The first step is attribute creation and assignment, and as shown in
25017 the comments the filter assigns the following attributes: @code{name},
25018 @code{priority} and whether the filter should be enabled with the
25019 @code{enabled} attribute.
25021 The second step is registering the frame filter with the dictionary or
25022 dictionaries that the frame filter has interest in. As shown in the
25023 comments, this filter just registers itself with the global dictionary
25024 @code{gdb.frame_filters}. As noted earlier, @code{gdb.frame_filters}
25025 is a dictionary that is initialized in the @code{gdb} module when
25026 @value{GDBN} starts. What dictionary a filter registers with is an
25027 important consideration. Generally, if a filter is specific to a set
25028 of code, it should be registered either in the @code{objfile} or
25029 @code{progspace} dictionaries as they are specific to the program
25030 currently loaded in @value{GDBN}. The global dictionary is always
25031 present in @value{GDBN} and is never unloaded. Any filters registered
25032 with the global dictionary will exist until @value{GDBN} exits. To
25033 avoid filters that may conflict, it is generally better to register
25034 frame filters against the dictionaries that more closely align with
25035 the usage of the filter currently in question. @xref{Python
25036 Auto-loading}, for further information on auto-loading Python scripts.
25038 @value{GDBN} takes a hands-off approach to frame filter registration,
25039 therefore it is the frame filter's responsibility to ensure
25040 registration has occurred, and that any exceptions are handled
25041 appropriately. In particular, you may wish to handle exceptions
25042 relating to Python dictionary key uniqueness. It is mandatory that
25043 the dictionary key is the same as frame filter's @code{name}
25044 attribute. When a user manages frame filters (@pxref{Frame Filter
25045 Management}), the names @value{GDBN} will display are those contained
25046 in the @code{name} attribute.
25048 The final step of this example is the implementation of the
25049 @code{filter} method. As shown in the example comments, we define the
25050 @code{filter} method and note that the method must take an iterator,
25051 and also must return an iterator. In this bare-bones example, the
25052 frame filter is not very useful as it just returns the iterator
25053 untouched. However this is a valid operation for frame filters that
25054 have the @code{enabled} attribute set, but decide not to operate on
25057 In the next example, the frame filter operates on all frames and
25058 utilizes a frame decorator to perform some work on the frames.
25059 @xref{Frame Decorator API}, for further information on the frame
25060 decorator interface.
25062 This example works on inlined frames. It highlights frames which are
25063 inlined by tagging them with an ``[inlined]'' tag. By applying a
25064 frame decorator to all frames with the Python @code{itertools imap}
25065 method, the example defers actions to the frame decorator. Frame
25066 decorators are only processed when @value{GDBN} prints the backtrace.
25068 This introduces a new decision making topic: whether to perform
25069 decision making operations at the filtering step, or at the printing
25070 step. In this example's approach, it does not perform any filtering
25071 decisions at the filtering step beyond mapping a frame decorator to
25072 each frame. This allows the actual decision making to be performed
25073 when each frame is printed. This is an important consideration, and
25074 well worth reflecting upon when designing a frame filter. An issue
25075 that frame filters should avoid is unwinding the stack if possible.
25076 Some stacks can run very deep, into the tens of thousands in some
25077 cases. To search every frame to determine if it is inlined ahead of
25078 time may be too expensive at the filtering step. The frame filter
25079 cannot know how many frames it has to iterate over, and it would have
25080 to iterate through them all. This ends up duplicating effort as
25081 @value{GDBN} performs this iteration when it prints the frames.
25083 In this example decision making can be deferred to the printing step.
25084 As each frame is printed, the frame decorator can examine each frame
25085 in turn when @value{GDBN} iterates. From a performance viewpoint,
25086 this is the most appropriate decision to make as it avoids duplicating
25087 the effort that the printing step would undertake anyway. Also, if
25088 there are many frame filters unwinding the stack during filtering, it
25089 can substantially delay the printing of the backtrace which will
25090 result in large memory usage, and a poor user experience.
25093 class InlineFilter():
25095 def __init__(self):
25096 self.name = "InlinedFrameFilter"
25097 self.priority = 100
25098 self.enabled = True
25099 gdb.frame_filters[self.name] = self
25101 def filter(self, frame_iter):
25102 frame_iter = itertools.imap(InlinedFrameDecorator,
25107 This frame filter is somewhat similar to the earlier example, except
25108 that the @code{filter} method applies a frame decorator object called
25109 @code{InlinedFrameDecorator} to each element in the iterator. The
25110 @code{imap} Python method is light-weight. It does not proactively
25111 iterate over the iterator, but rather creates a new iterator which
25112 wraps the existing one.
25114 Below is the frame decorator for this example.
25117 class InlinedFrameDecorator(FrameDecorator):
25119 def __init__(self, fobj):
25120 super(InlinedFrameDecorator, self).__init__(fobj)
25122 def function(self):
25123 frame = fobj.inferior_frame()
25124 name = str(frame.name())
25126 if frame.type() == gdb.INLINE_FRAME:
25127 name = name + " [inlined]"
25132 This frame decorator only defines and overrides the @code{function}
25133 method. It lets the supplied @code{FrameDecorator}, which is shipped
25134 with @value{GDBN}, perform the other work associated with printing
25137 The combination of these two objects create this output from a
25141 #0 0x004004e0 in bar () at inline.c:11
25142 #1 0x00400566 in max [inlined] (b=6, a=12) at inline.c:21
25143 #2 0x00400566 in main () at inline.c:31
25146 So in the case of this example, a frame decorator is applied to all
25147 frames, regardless of whether they may be inlined or not. As
25148 @value{GDBN} iterates over the iterator produced by the frame filters,
25149 @value{GDBN} executes each frame decorator which then makes a decision
25150 on what to print in the @code{function} callback. Using a strategy
25151 like this is a way to defer decisions on the frame content to printing
25154 @subheading Eliding Frames
25156 It might be that the above example is not desirable for representing
25157 inlined frames, and a hierarchical approach may be preferred. If we
25158 want to hierarchically represent frames, the @code{elided} frame
25159 decorator interface might be preferable.
25161 This example approaches the issue with the @code{elided} method. This
25162 example is quite long, but very simplistic. It is out-of-scope for
25163 this section to write a complete example that comprehensively covers
25164 all approaches of finding and printing inlined frames. However, this
25165 example illustrates the approach an author might use.
25167 This example comprises of three sections.
25170 class InlineFrameFilter():
25172 def __init__(self):
25173 self.name = "InlinedFrameFilter"
25174 self.priority = 100
25175 self.enabled = True
25176 gdb.frame_filters[self.name] = self
25178 def filter(self, frame_iter):
25179 return ElidingInlineIterator(frame_iter)
25182 This frame filter is very similar to the other examples. The only
25183 difference is this frame filter is wrapping the iterator provided to
25184 it (@code{frame_iter}) with a custom iterator called
25185 @code{ElidingInlineIterator}. This again defers actions to when
25186 @value{GDBN} prints the backtrace, as the iterator is not traversed
25189 The iterator for this example is as follows. It is in this section of
25190 the example where decisions are made on the content of the backtrace.
25193 class ElidingInlineIterator:
25194 def __init__(self, ii):
25195 self.input_iterator = ii
25197 def __iter__(self):
25201 frame = next(self.input_iterator)
25203 if frame.inferior_frame().type() != gdb.INLINE_FRAME:
25207 eliding_frame = next(self.input_iterator)
25208 except StopIteration:
25210 return ElidingFrameDecorator(eliding_frame, [frame])
25213 This iterator implements the Python iterator protocol. When the
25214 @code{next} function is called (when @value{GDBN} prints each frame),
25215 the iterator checks if this frame decorator, @code{frame}, is wrapping
25216 an inlined frame. If it is not, it returns the existing frame decorator
25217 untouched. If it is wrapping an inlined frame, it assumes that the
25218 inlined frame was contained within the next oldest frame,
25219 @code{eliding_frame}, which it fetches. It then creates and returns a
25220 frame decorator, @code{ElidingFrameDecorator}, which contains both the
25221 elided frame, and the eliding frame.
25224 class ElidingInlineDecorator(FrameDecorator):
25226 def __init__(self, frame, elided_frames):
25227 super(ElidingInlineDecorator, self).__init__(frame)
25229 self.elided_frames = elided_frames
25232 return iter(self.elided_frames)
25235 This frame decorator overrides one function and returns the inlined
25236 frame in the @code{elided} method. As before it lets
25237 @code{FrameDecorator} do the rest of the work involved in printing
25238 this frame. This produces the following output.
25241 #0 0x004004e0 in bar () at inline.c:11
25242 #2 0x00400529 in main () at inline.c:25
25243 #1 0x00400529 in max (b=6, a=12) at inline.c:15
25246 In that output, @code{max} which has been inlined into @code{main} is
25247 printed hierarchically. Another approach would be to combine the
25248 @code{function} method, and the @code{elided} method to both print a
25249 marker in the inlined frame, and also show the hierarchical
25252 @node Inferiors In Python
25253 @subsubsection Inferiors In Python
25254 @cindex inferiors in Python
25256 @findex gdb.Inferior
25257 Programs which are being run under @value{GDBN} are called inferiors
25258 (@pxref{Inferiors and Programs}). Python scripts can access
25259 information about and manipulate inferiors controlled by @value{GDBN}
25260 via objects of the @code{gdb.Inferior} class.
25262 The following inferior-related functions are available in the @code{gdb}
25265 @defun gdb.inferiors ()
25266 Return a tuple containing all inferior objects.
25269 @defun gdb.selected_inferior ()
25270 Return an object representing the current inferior.
25273 A @code{gdb.Inferior} object has the following attributes:
25275 @defvar Inferior.num
25276 ID of inferior, as assigned by GDB.
25279 @defvar Inferior.pid
25280 Process ID of the inferior, as assigned by the underlying operating
25284 @defvar Inferior.was_attached
25285 Boolean signaling whether the inferior was created using `attach', or
25286 started by @value{GDBN} itself.
25289 A @code{gdb.Inferior} object has the following methods:
25291 @defun Inferior.is_valid ()
25292 Returns @code{True} if the @code{gdb.Inferior} object is valid,
25293 @code{False} if not. A @code{gdb.Inferior} object will become invalid
25294 if the inferior no longer exists within @value{GDBN}. All other
25295 @code{gdb.Inferior} methods will throw an exception if it is invalid
25296 at the time the method is called.
25299 @defun Inferior.threads ()
25300 This method returns a tuple holding all the threads which are valid
25301 when it is called. If there are no valid threads, the method will
25302 return an empty tuple.
25305 @findex Inferior.read_memory
25306 @defun Inferior.read_memory (address, length)
25307 Read @var{length} bytes of memory from the inferior, starting at
25308 @var{address}. Returns a buffer object, which behaves much like an array
25309 or a string. It can be modified and given to the
25310 @code{Inferior.write_memory} function. In @code{Python} 3, the return
25311 value is a @code{memoryview} object.
25314 @findex Inferior.write_memory
25315 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
25316 Write the contents of @var{buffer} to the inferior, starting at
25317 @var{address}. The @var{buffer} parameter must be a Python object
25318 which supports the buffer protocol, i.e., a string, an array or the
25319 object returned from @code{Inferior.read_memory}. If given, @var{length}
25320 determines the number of bytes from @var{buffer} to be written.
25323 @findex gdb.search_memory
25324 @defun Inferior.search_memory (address, length, pattern)
25325 Search a region of the inferior memory starting at @var{address} with
25326 the given @var{length} using the search pattern supplied in
25327 @var{pattern}. The @var{pattern} parameter must be a Python object
25328 which supports the buffer protocol, i.e., a string, an array or the
25329 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
25330 containing the address where the pattern was found, or @code{None} if
25331 the pattern could not be found.
25334 @node Events In Python
25335 @subsubsection Events In Python
25336 @cindex inferior events in Python
25338 @value{GDBN} provides a general event facility so that Python code can be
25339 notified of various state changes, particularly changes that occur in
25342 An @dfn{event} is just an object that describes some state change. The
25343 type of the object and its attributes will vary depending on the details
25344 of the change. All the existing events are described below.
25346 In order to be notified of an event, you must register an event handler
25347 with an @dfn{event registry}. An event registry is an object in the
25348 @code{gdb.events} module which dispatches particular events. A registry
25349 provides methods to register and unregister event handlers:
25351 @defun EventRegistry.connect (object)
25352 Add the given callable @var{object} to the registry. This object will be
25353 called when an event corresponding to this registry occurs.
25356 @defun EventRegistry.disconnect (object)
25357 Remove the given @var{object} from the registry. Once removed, the object
25358 will no longer receive notifications of events.
25361 Here is an example:
25364 def exit_handler (event):
25365 print "event type: exit"
25366 print "exit code: %d" % (event.exit_code)
25368 gdb.events.exited.connect (exit_handler)
25371 In the above example we connect our handler @code{exit_handler} to the
25372 registry @code{events.exited}. Once connected, @code{exit_handler} gets
25373 called when the inferior exits. The argument @dfn{event} in this example is
25374 of type @code{gdb.ExitedEvent}. As you can see in the example the
25375 @code{ExitedEvent} object has an attribute which indicates the exit code of
25378 The following is a listing of the event registries that are available and
25379 details of the events they emit:
25384 Emits @code{gdb.ThreadEvent}.
25386 Some events can be thread specific when @value{GDBN} is running in non-stop
25387 mode. When represented in Python, these events all extend
25388 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
25389 events which are emitted by this or other modules might extend this event.
25390 Examples of these events are @code{gdb.BreakpointEvent} and
25391 @code{gdb.ContinueEvent}.
25393 @defvar ThreadEvent.inferior_thread
25394 In non-stop mode this attribute will be set to the specific thread which was
25395 involved in the emitted event. Otherwise, it will be set to @code{None}.
25398 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
25400 This event indicates that the inferior has been continued after a stop. For
25401 inherited attribute refer to @code{gdb.ThreadEvent} above.
25403 @item events.exited
25404 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
25405 @code{events.ExitedEvent} has two attributes:
25406 @defvar ExitedEvent.exit_code
25407 An integer representing the exit code, if available, which the inferior
25408 has returned. (The exit code could be unavailable if, for example,
25409 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
25410 the attribute does not exist.
25412 @defvar ExitedEvent inferior
25413 A reference to the inferior which triggered the @code{exited} event.
25417 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
25419 Indicates that the inferior has stopped. All events emitted by this registry
25420 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
25421 will indicate the stopped thread when @value{GDBN} is running in non-stop
25422 mode. Refer to @code{gdb.ThreadEvent} above for more details.
25424 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
25426 This event indicates that the inferior or one of its threads has received as
25427 signal. @code{gdb.SignalEvent} has the following attributes:
25429 @defvar SignalEvent.stop_signal
25430 A string representing the signal received by the inferior. A list of possible
25431 signal values can be obtained by running the command @code{info signals} in
25432 the @value{GDBN} command prompt.
25435 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
25437 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
25438 been hit, and has the following attributes:
25440 @defvar BreakpointEvent.breakpoints
25441 A sequence containing references to all the breakpoints (type
25442 @code{gdb.Breakpoint}) that were hit.
25443 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
25445 @defvar BreakpointEvent.breakpoint
25446 A reference to the first breakpoint that was hit.
25447 This function is maintained for backward compatibility and is now deprecated
25448 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
25451 @item events.new_objfile
25452 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
25453 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
25455 @defvar NewObjFileEvent.new_objfile
25456 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
25457 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
25462 @node Threads In Python
25463 @subsubsection Threads In Python
25464 @cindex threads in python
25466 @findex gdb.InferiorThread
25467 Python scripts can access information about, and manipulate inferior threads
25468 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
25470 The following thread-related functions are available in the @code{gdb}
25473 @findex gdb.selected_thread
25474 @defun gdb.selected_thread ()
25475 This function returns the thread object for the selected thread. If there
25476 is no selected thread, this will return @code{None}.
25479 A @code{gdb.InferiorThread} object has the following attributes:
25481 @defvar InferiorThread.name
25482 The name of the thread. If the user specified a name using
25483 @code{thread name}, then this returns that name. Otherwise, if an
25484 OS-supplied name is available, then it is returned. Otherwise, this
25485 returns @code{None}.
25487 This attribute can be assigned to. The new value must be a string
25488 object, which sets the new name, or @code{None}, which removes any
25489 user-specified thread name.
25492 @defvar InferiorThread.num
25493 ID of the thread, as assigned by GDB.
25496 @defvar InferiorThread.ptid
25497 ID of the thread, as assigned by the operating system. This attribute is a
25498 tuple containing three integers. The first is the Process ID (PID); the second
25499 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
25500 Either the LWPID or TID may be 0, which indicates that the operating system
25501 does not use that identifier.
25504 A @code{gdb.InferiorThread} object has the following methods:
25506 @defun InferiorThread.is_valid ()
25507 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
25508 @code{False} if not. A @code{gdb.InferiorThread} object will become
25509 invalid if the thread exits, or the inferior that the thread belongs
25510 is deleted. All other @code{gdb.InferiorThread} methods will throw an
25511 exception if it is invalid at the time the method is called.
25514 @defun InferiorThread.switch ()
25515 This changes @value{GDBN}'s currently selected thread to the one represented
25519 @defun InferiorThread.is_stopped ()
25520 Return a Boolean indicating whether the thread is stopped.
25523 @defun InferiorThread.is_running ()
25524 Return a Boolean indicating whether the thread is running.
25527 @defun InferiorThread.is_exited ()
25528 Return a Boolean indicating whether the thread is exited.
25531 @node Commands In Python
25532 @subsubsection Commands In Python
25534 @cindex commands in python
25535 @cindex python commands
25536 You can implement new @value{GDBN} CLI commands in Python. A CLI
25537 command is implemented using an instance of the @code{gdb.Command}
25538 class, most commonly using a subclass.
25540 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
25541 The object initializer for @code{Command} registers the new command
25542 with @value{GDBN}. This initializer is normally invoked from the
25543 subclass' own @code{__init__} method.
25545 @var{name} is the name of the command. If @var{name} consists of
25546 multiple words, then the initial words are looked for as prefix
25547 commands. In this case, if one of the prefix commands does not exist,
25548 an exception is raised.
25550 There is no support for multi-line commands.
25552 @var{command_class} should be one of the @samp{COMMAND_} constants
25553 defined below. This argument tells @value{GDBN} how to categorize the
25554 new command in the help system.
25556 @var{completer_class} is an optional argument. If given, it should be
25557 one of the @samp{COMPLETE_} constants defined below. This argument
25558 tells @value{GDBN} how to perform completion for this command. If not
25559 given, @value{GDBN} will attempt to complete using the object's
25560 @code{complete} method (see below); if no such method is found, an
25561 error will occur when completion is attempted.
25563 @var{prefix} is an optional argument. If @code{True}, then the new
25564 command is a prefix command; sub-commands of this command may be
25567 The help text for the new command is taken from the Python
25568 documentation string for the command's class, if there is one. If no
25569 documentation string is provided, the default value ``This command is
25570 not documented.'' is used.
25573 @cindex don't repeat Python command
25574 @defun Command.dont_repeat ()
25575 By default, a @value{GDBN} command is repeated when the user enters a
25576 blank line at the command prompt. A command can suppress this
25577 behavior by invoking the @code{dont_repeat} method. This is similar
25578 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
25581 @defun Command.invoke (argument, from_tty)
25582 This method is called by @value{GDBN} when this command is invoked.
25584 @var{argument} is a string. It is the argument to the command, after
25585 leading and trailing whitespace has been stripped.
25587 @var{from_tty} is a boolean argument. When true, this means that the
25588 command was entered by the user at the terminal; when false it means
25589 that the command came from elsewhere.
25591 If this method throws an exception, it is turned into a @value{GDBN}
25592 @code{error} call. Otherwise, the return value is ignored.
25594 @findex gdb.string_to_argv
25595 To break @var{argument} up into an argv-like string use
25596 @code{gdb.string_to_argv}. This function behaves identically to
25597 @value{GDBN}'s internal argument lexer @code{buildargv}.
25598 It is recommended to use this for consistency.
25599 Arguments are separated by spaces and may be quoted.
25603 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
25604 ['1', '2 "3', '4 "5', "6 '7"]
25609 @cindex completion of Python commands
25610 @defun Command.complete (text, word)
25611 This method is called by @value{GDBN} when the user attempts
25612 completion on this command. All forms of completion are handled by
25613 this method, that is, the @key{TAB} and @key{M-?} key bindings
25614 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
25617 The arguments @var{text} and @var{word} are both strings. @var{text}
25618 holds the complete command line up to the cursor's location.
25619 @var{word} holds the last word of the command line; this is computed
25620 using a word-breaking heuristic.
25622 The @code{complete} method can return several values:
25625 If the return value is a sequence, the contents of the sequence are
25626 used as the completions. It is up to @code{complete} to ensure that the
25627 contents actually do complete the word. A zero-length sequence is
25628 allowed, it means that there were no completions available. Only
25629 string elements of the sequence are used; other elements in the
25630 sequence are ignored.
25633 If the return value is one of the @samp{COMPLETE_} constants defined
25634 below, then the corresponding @value{GDBN}-internal completion
25635 function is invoked, and its result is used.
25638 All other results are treated as though there were no available
25643 When a new command is registered, it must be declared as a member of
25644 some general class of commands. This is used to classify top-level
25645 commands in the on-line help system; note that prefix commands are not
25646 listed under their own category but rather that of their top-level
25647 command. The available classifications are represented by constants
25648 defined in the @code{gdb} module:
25651 @findex COMMAND_NONE
25652 @findex gdb.COMMAND_NONE
25653 @item gdb.COMMAND_NONE
25654 The command does not belong to any particular class. A command in
25655 this category will not be displayed in any of the help categories.
25657 @findex COMMAND_RUNNING
25658 @findex gdb.COMMAND_RUNNING
25659 @item gdb.COMMAND_RUNNING
25660 The command is related to running the inferior. For example,
25661 @code{start}, @code{step}, and @code{continue} are in this category.
25662 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
25663 commands in this category.
25665 @findex COMMAND_DATA
25666 @findex gdb.COMMAND_DATA
25667 @item gdb.COMMAND_DATA
25668 The command is related to data or variables. For example,
25669 @code{call}, @code{find}, and @code{print} are in this category. Type
25670 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
25673 @findex COMMAND_STACK
25674 @findex gdb.COMMAND_STACK
25675 @item gdb.COMMAND_STACK
25676 The command has to do with manipulation of the stack. For example,
25677 @code{backtrace}, @code{frame}, and @code{return} are in this
25678 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
25679 list of commands in this category.
25681 @findex COMMAND_FILES
25682 @findex gdb.COMMAND_FILES
25683 @item gdb.COMMAND_FILES
25684 This class is used for file-related commands. For example,
25685 @code{file}, @code{list} and @code{section} are in this category.
25686 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
25687 commands in this category.
25689 @findex COMMAND_SUPPORT
25690 @findex gdb.COMMAND_SUPPORT
25691 @item gdb.COMMAND_SUPPORT
25692 This should be used for ``support facilities'', generally meaning
25693 things that are useful to the user when interacting with @value{GDBN},
25694 but not related to the state of the inferior. For example,
25695 @code{help}, @code{make}, and @code{shell} are in this category. Type
25696 @kbd{help support} at the @value{GDBN} prompt to see a list of
25697 commands in this category.
25699 @findex COMMAND_STATUS
25700 @findex gdb.COMMAND_STATUS
25701 @item gdb.COMMAND_STATUS
25702 The command is an @samp{info}-related command, that is, related to the
25703 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
25704 and @code{show} are in this category. Type @kbd{help status} at the
25705 @value{GDBN} prompt to see a list of commands in this category.
25707 @findex COMMAND_BREAKPOINTS
25708 @findex gdb.COMMAND_BREAKPOINTS
25709 @item gdb.COMMAND_BREAKPOINTS
25710 The command has to do with breakpoints. For example, @code{break},
25711 @code{clear}, and @code{delete} are in this category. Type @kbd{help
25712 breakpoints} at the @value{GDBN} prompt to see a list of commands in
25715 @findex COMMAND_TRACEPOINTS
25716 @findex gdb.COMMAND_TRACEPOINTS
25717 @item gdb.COMMAND_TRACEPOINTS
25718 The command has to do with tracepoints. For example, @code{trace},
25719 @code{actions}, and @code{tfind} are in this category. Type
25720 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
25721 commands in this category.
25723 @findex COMMAND_USER
25724 @findex gdb.COMMAND_USER
25725 @item gdb.COMMAND_USER
25726 The command is a general purpose command for the user, and typically
25727 does not fit in one of the other categories.
25728 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
25729 a list of commands in this category, as well as the list of gdb macros
25730 (@pxref{Sequences}).
25732 @findex COMMAND_OBSCURE
25733 @findex gdb.COMMAND_OBSCURE
25734 @item gdb.COMMAND_OBSCURE
25735 The command is only used in unusual circumstances, or is not of
25736 general interest to users. For example, @code{checkpoint},
25737 @code{fork}, and @code{stop} are in this category. Type @kbd{help
25738 obscure} at the @value{GDBN} prompt to see a list of commands in this
25741 @findex COMMAND_MAINTENANCE
25742 @findex gdb.COMMAND_MAINTENANCE
25743 @item gdb.COMMAND_MAINTENANCE
25744 The command is only useful to @value{GDBN} maintainers. The
25745 @code{maintenance} and @code{flushregs} commands are in this category.
25746 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
25747 commands in this category.
25750 A new command can use a predefined completion function, either by
25751 specifying it via an argument at initialization, or by returning it
25752 from the @code{complete} method. These predefined completion
25753 constants are all defined in the @code{gdb} module:
25756 @findex COMPLETE_NONE
25757 @findex gdb.COMPLETE_NONE
25758 @item gdb.COMPLETE_NONE
25759 This constant means that no completion should be done.
25761 @findex COMPLETE_FILENAME
25762 @findex gdb.COMPLETE_FILENAME
25763 @item gdb.COMPLETE_FILENAME
25764 This constant means that filename completion should be performed.
25766 @findex COMPLETE_LOCATION
25767 @findex gdb.COMPLETE_LOCATION
25768 @item gdb.COMPLETE_LOCATION
25769 This constant means that location completion should be done.
25770 @xref{Specify Location}.
25772 @findex COMPLETE_COMMAND
25773 @findex gdb.COMPLETE_COMMAND
25774 @item gdb.COMPLETE_COMMAND
25775 This constant means that completion should examine @value{GDBN}
25778 @findex COMPLETE_SYMBOL
25779 @findex gdb.COMPLETE_SYMBOL
25780 @item gdb.COMPLETE_SYMBOL
25781 This constant means that completion should be done using symbol names
25785 The following code snippet shows how a trivial CLI command can be
25786 implemented in Python:
25789 class HelloWorld (gdb.Command):
25790 """Greet the whole world."""
25792 def __init__ (self):
25793 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
25795 def invoke (self, arg, from_tty):
25796 print "Hello, World!"
25801 The last line instantiates the class, and is necessary to trigger the
25802 registration of the command with @value{GDBN}. Depending on how the
25803 Python code is read into @value{GDBN}, you may need to import the
25804 @code{gdb} module explicitly.
25806 @node Parameters In Python
25807 @subsubsection Parameters In Python
25809 @cindex parameters in python
25810 @cindex python parameters
25811 @tindex gdb.Parameter
25813 You can implement new @value{GDBN} parameters using Python. A new
25814 parameter is implemented as an instance of the @code{gdb.Parameter}
25817 Parameters are exposed to the user via the @code{set} and
25818 @code{show} commands. @xref{Help}.
25820 There are many parameters that already exist and can be set in
25821 @value{GDBN}. Two examples are: @code{set follow fork} and
25822 @code{set charset}. Setting these parameters influences certain
25823 behavior in @value{GDBN}. Similarly, you can define parameters that
25824 can be used to influence behavior in custom Python scripts and commands.
25826 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
25827 The object initializer for @code{Parameter} registers the new
25828 parameter with @value{GDBN}. This initializer is normally invoked
25829 from the subclass' own @code{__init__} method.
25831 @var{name} is the name of the new parameter. If @var{name} consists
25832 of multiple words, then the initial words are looked for as prefix
25833 parameters. An example of this can be illustrated with the
25834 @code{set print} set of parameters. If @var{name} is
25835 @code{print foo}, then @code{print} will be searched as the prefix
25836 parameter. In this case the parameter can subsequently be accessed in
25837 @value{GDBN} as @code{set print foo}.
25839 If @var{name} consists of multiple words, and no prefix parameter group
25840 can be found, an exception is raised.
25842 @var{command-class} should be one of the @samp{COMMAND_} constants
25843 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
25844 categorize the new parameter in the help system.
25846 @var{parameter-class} should be one of the @samp{PARAM_} constants
25847 defined below. This argument tells @value{GDBN} the type of the new
25848 parameter; this information is used for input validation and
25851 If @var{parameter-class} is @code{PARAM_ENUM}, then
25852 @var{enum-sequence} must be a sequence of strings. These strings
25853 represent the possible values for the parameter.
25855 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
25856 of a fourth argument will cause an exception to be thrown.
25858 The help text for the new parameter is taken from the Python
25859 documentation string for the parameter's class, if there is one. If
25860 there is no documentation string, a default value is used.
25863 @defvar Parameter.set_doc
25864 If this attribute exists, and is a string, then its value is used as
25865 the help text for this parameter's @code{set} command. The value is
25866 examined when @code{Parameter.__init__} is invoked; subsequent changes
25870 @defvar Parameter.show_doc
25871 If this attribute exists, and is a string, then its value is used as
25872 the help text for this parameter's @code{show} command. The value is
25873 examined when @code{Parameter.__init__} is invoked; subsequent changes
25877 @defvar Parameter.value
25878 The @code{value} attribute holds the underlying value of the
25879 parameter. It can be read and assigned to just as any other
25880 attribute. @value{GDBN} does validation when assignments are made.
25883 There are two methods that should be implemented in any
25884 @code{Parameter} class. These are:
25886 @defun Parameter.get_set_string (self)
25887 @value{GDBN} will call this method when a @var{parameter}'s value has
25888 been changed via the @code{set} API (for example, @kbd{set foo off}).
25889 The @code{value} attribute has already been populated with the new
25890 value and may be used in output. This method must return a string.
25893 @defun Parameter.get_show_string (self, svalue)
25894 @value{GDBN} will call this method when a @var{parameter}'s
25895 @code{show} API has been invoked (for example, @kbd{show foo}). The
25896 argument @code{svalue} receives the string representation of the
25897 current value. This method must return a string.
25900 When a new parameter is defined, its type must be specified. The
25901 available types are represented by constants defined in the @code{gdb}
25905 @findex PARAM_BOOLEAN
25906 @findex gdb.PARAM_BOOLEAN
25907 @item gdb.PARAM_BOOLEAN
25908 The value is a plain boolean. The Python boolean values, @code{True}
25909 and @code{False} are the only valid values.
25911 @findex PARAM_AUTO_BOOLEAN
25912 @findex gdb.PARAM_AUTO_BOOLEAN
25913 @item gdb.PARAM_AUTO_BOOLEAN
25914 The value has three possible states: true, false, and @samp{auto}. In
25915 Python, true and false are represented using boolean constants, and
25916 @samp{auto} is represented using @code{None}.
25918 @findex PARAM_UINTEGER
25919 @findex gdb.PARAM_UINTEGER
25920 @item gdb.PARAM_UINTEGER
25921 The value is an unsigned integer. The value of 0 should be
25922 interpreted to mean ``unlimited''.
25924 @findex PARAM_INTEGER
25925 @findex gdb.PARAM_INTEGER
25926 @item gdb.PARAM_INTEGER
25927 The value is a signed integer. The value of 0 should be interpreted
25928 to mean ``unlimited''.
25930 @findex PARAM_STRING
25931 @findex gdb.PARAM_STRING
25932 @item gdb.PARAM_STRING
25933 The value is a string. When the user modifies the string, any escape
25934 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
25935 translated into corresponding characters and encoded into the current
25938 @findex PARAM_STRING_NOESCAPE
25939 @findex gdb.PARAM_STRING_NOESCAPE
25940 @item gdb.PARAM_STRING_NOESCAPE
25941 The value is a string. When the user modifies the string, escapes are
25942 passed through untranslated.
25944 @findex PARAM_OPTIONAL_FILENAME
25945 @findex gdb.PARAM_OPTIONAL_FILENAME
25946 @item gdb.PARAM_OPTIONAL_FILENAME
25947 The value is a either a filename (a string), or @code{None}.
25949 @findex PARAM_FILENAME
25950 @findex gdb.PARAM_FILENAME
25951 @item gdb.PARAM_FILENAME
25952 The value is a filename. This is just like
25953 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
25955 @findex PARAM_ZINTEGER
25956 @findex gdb.PARAM_ZINTEGER
25957 @item gdb.PARAM_ZINTEGER
25958 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
25959 is interpreted as itself.
25962 @findex gdb.PARAM_ENUM
25963 @item gdb.PARAM_ENUM
25964 The value is a string, which must be one of a collection string
25965 constants provided when the parameter is created.
25968 @node Functions In Python
25969 @subsubsection Writing new convenience functions
25971 @cindex writing convenience functions
25972 @cindex convenience functions in python
25973 @cindex python convenience functions
25974 @tindex gdb.Function
25976 You can implement new convenience functions (@pxref{Convenience Vars})
25977 in Python. A convenience function is an instance of a subclass of the
25978 class @code{gdb.Function}.
25980 @defun Function.__init__ (name)
25981 The initializer for @code{Function} registers the new function with
25982 @value{GDBN}. The argument @var{name} is the name of the function,
25983 a string. The function will be visible to the user as a convenience
25984 variable of type @code{internal function}, whose name is the same as
25985 the given @var{name}.
25987 The documentation for the new function is taken from the documentation
25988 string for the new class.
25991 @defun Function.invoke (@var{*args})
25992 When a convenience function is evaluated, its arguments are converted
25993 to instances of @code{gdb.Value}, and then the function's
25994 @code{invoke} method is called. Note that @value{GDBN} does not
25995 predetermine the arity of convenience functions. Instead, all
25996 available arguments are passed to @code{invoke}, following the
25997 standard Python calling convention. In particular, a convenience
25998 function can have default values for parameters without ill effect.
26000 The return value of this method is used as its value in the enclosing
26001 expression. If an ordinary Python value is returned, it is converted
26002 to a @code{gdb.Value} following the usual rules.
26005 The following code snippet shows how a trivial convenience function can
26006 be implemented in Python:
26009 class Greet (gdb.Function):
26010 """Return string to greet someone.
26011 Takes a name as argument."""
26013 def __init__ (self):
26014 super (Greet, self).__init__ ("greet")
26016 def invoke (self, name):
26017 return "Hello, %s!" % name.string ()
26022 The last line instantiates the class, and is necessary to trigger the
26023 registration of the function with @value{GDBN}. Depending on how the
26024 Python code is read into @value{GDBN}, you may need to import the
26025 @code{gdb} module explicitly.
26027 Now you can use the function in an expression:
26030 (gdb) print $greet("Bob")
26034 @node Progspaces In Python
26035 @subsubsection Program Spaces In Python
26037 @cindex progspaces in python
26038 @tindex gdb.Progspace
26040 A program space, or @dfn{progspace}, represents a symbolic view
26041 of an address space.
26042 It consists of all of the objfiles of the program.
26043 @xref{Objfiles In Python}.
26044 @xref{Inferiors and Programs, program spaces}, for more details
26045 about program spaces.
26047 The following progspace-related functions are available in the
26050 @findex gdb.current_progspace
26051 @defun gdb.current_progspace ()
26052 This function returns the program space of the currently selected inferior.
26053 @xref{Inferiors and Programs}.
26056 @findex gdb.progspaces
26057 @defun gdb.progspaces ()
26058 Return a sequence of all the progspaces currently known to @value{GDBN}.
26061 Each progspace is represented by an instance of the @code{gdb.Progspace}
26064 @defvar Progspace.filename
26065 The file name of the progspace as a string.
26068 @defvar Progspace.pretty_printers
26069 The @code{pretty_printers} attribute is a list of functions. It is
26070 used to look up pretty-printers. A @code{Value} is passed to each
26071 function in order; if the function returns @code{None}, then the
26072 search continues. Otherwise, the return value should be an object
26073 which is used to format the value. @xref{Pretty Printing API}, for more
26077 @defvar Progspace.type_printers
26078 The @code{type_printers} attribute is a list of type printer objects.
26079 @xref{Type Printing API}, for more information.
26082 @defvar Progspace.frame_filters
26083 The @code{frame_filters} attribute is a dictionary of frame filter
26084 objects. @xref{Frame Filter API}, for more information.
26087 @node Objfiles In Python
26088 @subsubsection Objfiles In Python
26090 @cindex objfiles in python
26091 @tindex gdb.Objfile
26093 @value{GDBN} loads symbols for an inferior from various
26094 symbol-containing files (@pxref{Files}). These include the primary
26095 executable file, any shared libraries used by the inferior, and any
26096 separate debug info files (@pxref{Separate Debug Files}).
26097 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
26099 The following objfile-related functions are available in the
26102 @findex gdb.current_objfile
26103 @defun gdb.current_objfile ()
26104 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
26105 sets the ``current objfile'' to the corresponding objfile. This
26106 function returns the current objfile. If there is no current objfile,
26107 this function returns @code{None}.
26110 @findex gdb.objfiles
26111 @defun gdb.objfiles ()
26112 Return a sequence of all the objfiles current known to @value{GDBN}.
26113 @xref{Objfiles In Python}.
26116 Each objfile is represented by an instance of the @code{gdb.Objfile}
26119 @defvar Objfile.filename
26120 The file name of the objfile as a string.
26123 @defvar Objfile.pretty_printers
26124 The @code{pretty_printers} attribute is a list of functions. It is
26125 used to look up pretty-printers. A @code{Value} is passed to each
26126 function in order; if the function returns @code{None}, then the
26127 search continues. Otherwise, the return value should be an object
26128 which is used to format the value. @xref{Pretty Printing API}, for more
26132 @defvar Objfile.type_printers
26133 The @code{type_printers} attribute is a list of type printer objects.
26134 @xref{Type Printing API}, for more information.
26137 @defvar Objfile.frame_filters
26138 The @code{frame_filters} attribute is a dictionary of frame filter
26139 objects. @xref{Frame Filter API}, for more information.
26142 A @code{gdb.Objfile} object has the following methods:
26144 @defun Objfile.is_valid ()
26145 Returns @code{True} if the @code{gdb.Objfile} object is valid,
26146 @code{False} if not. A @code{gdb.Objfile} object can become invalid
26147 if the object file it refers to is not loaded in @value{GDBN} any
26148 longer. All other @code{gdb.Objfile} methods will throw an exception
26149 if it is invalid at the time the method is called.
26152 @node Frames In Python
26153 @subsubsection Accessing inferior stack frames from Python.
26155 @cindex frames in python
26156 When the debugged program stops, @value{GDBN} is able to analyze its call
26157 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
26158 represents a frame in the stack. A @code{gdb.Frame} object is only valid
26159 while its corresponding frame exists in the inferior's stack. If you try
26160 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
26161 exception (@pxref{Exception Handling}).
26163 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
26167 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
26171 The following frame-related functions are available in the @code{gdb} module:
26173 @findex gdb.selected_frame
26174 @defun gdb.selected_frame ()
26175 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
26178 @findex gdb.newest_frame
26179 @defun gdb.newest_frame ()
26180 Return the newest frame object for the selected thread.
26183 @defun gdb.frame_stop_reason_string (reason)
26184 Return a string explaining the reason why @value{GDBN} stopped unwinding
26185 frames, as expressed by the given @var{reason} code (an integer, see the
26186 @code{unwind_stop_reason} method further down in this section).
26189 A @code{gdb.Frame} object has the following methods:
26191 @defun Frame.is_valid ()
26192 Returns true if the @code{gdb.Frame} object is valid, false if not.
26193 A frame object can become invalid if the frame it refers to doesn't
26194 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
26195 an exception if it is invalid at the time the method is called.
26198 @defun Frame.name ()
26199 Returns the function name of the frame, or @code{None} if it can't be
26203 @defun Frame.architecture ()
26204 Returns the @code{gdb.Architecture} object corresponding to the frame's
26205 architecture. @xref{Architectures In Python}.
26208 @defun Frame.type ()
26209 Returns the type of the frame. The value can be one of:
26211 @item gdb.NORMAL_FRAME
26212 An ordinary stack frame.
26214 @item gdb.DUMMY_FRAME
26215 A fake stack frame that was created by @value{GDBN} when performing an
26216 inferior function call.
26218 @item gdb.INLINE_FRAME
26219 A frame representing an inlined function. The function was inlined
26220 into a @code{gdb.NORMAL_FRAME} that is older than this one.
26222 @item gdb.TAILCALL_FRAME
26223 A frame representing a tail call. @xref{Tail Call Frames}.
26225 @item gdb.SIGTRAMP_FRAME
26226 A signal trampoline frame. This is the frame created by the OS when
26227 it calls into a signal handler.
26229 @item gdb.ARCH_FRAME
26230 A fake stack frame representing a cross-architecture call.
26232 @item gdb.SENTINEL_FRAME
26233 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
26238 @defun Frame.unwind_stop_reason ()
26239 Return an integer representing the reason why it's not possible to find
26240 more frames toward the outermost frame. Use
26241 @code{gdb.frame_stop_reason_string} to convert the value returned by this
26242 function to a string. The value can be one of:
26245 @item gdb.FRAME_UNWIND_NO_REASON
26246 No particular reason (older frames should be available).
26248 @item gdb.FRAME_UNWIND_NULL_ID
26249 The previous frame's analyzer returns an invalid result.
26251 @item gdb.FRAME_UNWIND_OUTERMOST
26252 This frame is the outermost.
26254 @item gdb.FRAME_UNWIND_UNAVAILABLE
26255 Cannot unwind further, because that would require knowing the
26256 values of registers or memory that have not been collected.
26258 @item gdb.FRAME_UNWIND_INNER_ID
26259 This frame ID looks like it ought to belong to a NEXT frame,
26260 but we got it for a PREV frame. Normally, this is a sign of
26261 unwinder failure. It could also indicate stack corruption.
26263 @item gdb.FRAME_UNWIND_SAME_ID
26264 This frame has the same ID as the previous one. That means
26265 that unwinding further would almost certainly give us another
26266 frame with exactly the same ID, so break the chain. Normally,
26267 this is a sign of unwinder failure. It could also indicate
26270 @item gdb.FRAME_UNWIND_NO_SAVED_PC
26271 The frame unwinder did not find any saved PC, but we needed
26272 one to unwind further.
26274 @item gdb.FRAME_UNWIND_FIRST_ERROR
26275 Any stop reason greater or equal to this value indicates some kind
26276 of error. This special value facilitates writing code that tests
26277 for errors in unwinding in a way that will work correctly even if
26278 the list of the other values is modified in future @value{GDBN}
26279 versions. Using it, you could write:
26281 reason = gdb.selected_frame().unwind_stop_reason ()
26282 reason_str = gdb.frame_stop_reason_string (reason)
26283 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
26284 print "An error occured: %s" % reason_str
26291 Returns the frame's resume address.
26294 @defun Frame.block ()
26295 Return the frame's code block. @xref{Blocks In Python}.
26298 @defun Frame.function ()
26299 Return the symbol for the function corresponding to this frame.
26300 @xref{Symbols In Python}.
26303 @defun Frame.older ()
26304 Return the frame that called this frame.
26307 @defun Frame.newer ()
26308 Return the frame called by this frame.
26311 @defun Frame.find_sal ()
26312 Return the frame's symtab and line object.
26313 @xref{Symbol Tables In Python}.
26316 @defun Frame.read_var (variable @r{[}, block@r{]})
26317 Return the value of @var{variable} in this frame. If the optional
26318 argument @var{block} is provided, search for the variable from that
26319 block; otherwise start at the frame's current block (which is
26320 determined by the frame's current program counter). @var{variable}
26321 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
26322 @code{gdb.Block} object.
26325 @defun Frame.select ()
26326 Set this frame to be the selected frame. @xref{Stack, ,Examining the
26330 @node Blocks In Python
26331 @subsubsection Accessing blocks from Python.
26333 @cindex blocks in python
26336 In @value{GDBN}, symbols are stored in blocks. A block corresponds
26337 roughly to a scope in the source code. Blocks are organized
26338 hierarchically, and are represented individually in Python as a
26339 @code{gdb.Block}. Blocks rely on debugging information being
26342 A frame has a block. Please see @ref{Frames In Python}, for a more
26343 in-depth discussion of frames.
26345 The outermost block is known as the @dfn{global block}. The global
26346 block typically holds public global variables and functions.
26348 The block nested just inside the global block is the @dfn{static
26349 block}. The static block typically holds file-scoped variables and
26352 @value{GDBN} provides a method to get a block's superblock, but there
26353 is currently no way to examine the sub-blocks of a block, or to
26354 iterate over all the blocks in a symbol table (@pxref{Symbol Tables In
26357 Here is a short example that should help explain blocks:
26360 /* This is in the global block. */
26363 /* This is in the static block. */
26364 static int file_scope;
26366 /* 'function' is in the global block, and 'argument' is
26367 in a block nested inside of 'function'. */
26368 int function (int argument)
26370 /* 'local' is in a block inside 'function'. It may or may
26371 not be in the same block as 'argument'. */
26375 /* 'inner' is in a block whose superblock is the one holding
26379 /* If this call is expanded by the compiler, you may see
26380 a nested block here whose function is 'inline_function'
26381 and whose superblock is the one holding 'inner'. */
26382 inline_function ();
26387 A @code{gdb.Block} is iterable. The iterator returns the symbols
26388 (@pxref{Symbols In Python}) local to the block. Python programs
26389 should not assume that a specific block object will always contain a
26390 given symbol, since changes in @value{GDBN} features and
26391 infrastructure may cause symbols move across blocks in a symbol
26394 The following block-related functions are available in the @code{gdb}
26397 @findex gdb.block_for_pc
26398 @defun gdb.block_for_pc (pc)
26399 Return the innermost @code{gdb.Block} containing the given @var{pc}
26400 value. If the block cannot be found for the @var{pc} value specified,
26401 the function will return @code{None}.
26404 A @code{gdb.Block} object has the following methods:
26406 @defun Block.is_valid ()
26407 Returns @code{True} if the @code{gdb.Block} object is valid,
26408 @code{False} if not. A block object can become invalid if the block it
26409 refers to doesn't exist anymore in the inferior. All other
26410 @code{gdb.Block} methods will throw an exception if it is invalid at
26411 the time the method is called. The block's validity is also checked
26412 during iteration over symbols of the block.
26415 A @code{gdb.Block} object has the following attributes:
26417 @defvar Block.start
26418 The start address of the block. This attribute is not writable.
26422 The end address of the block. This attribute is not writable.
26425 @defvar Block.function
26426 The name of the block represented as a @code{gdb.Symbol}. If the
26427 block is not named, then this attribute holds @code{None}. This
26428 attribute is not writable.
26430 For ordinary function blocks, the superblock is the static block.
26431 However, you should note that it is possible for a function block to
26432 have a superblock that is not the static block -- for instance this
26433 happens for an inlined function.
26436 @defvar Block.superblock
26437 The block containing this block. If this parent block does not exist,
26438 this attribute holds @code{None}. This attribute is not writable.
26441 @defvar Block.global_block
26442 The global block associated with this block. This attribute is not
26446 @defvar Block.static_block
26447 The static block associated with this block. This attribute is not
26451 @defvar Block.is_global
26452 @code{True} if the @code{gdb.Block} object is a global block,
26453 @code{False} if not. This attribute is not
26457 @defvar Block.is_static
26458 @code{True} if the @code{gdb.Block} object is a static block,
26459 @code{False} if not. This attribute is not writable.
26462 @node Symbols In Python
26463 @subsubsection Python representation of Symbols.
26465 @cindex symbols in python
26468 @value{GDBN} represents every variable, function and type as an
26469 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
26470 Similarly, Python represents these symbols in @value{GDBN} with the
26471 @code{gdb.Symbol} object.
26473 The following symbol-related functions are available in the @code{gdb}
26476 @findex gdb.lookup_symbol
26477 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
26478 This function searches for a symbol by name. The search scope can be
26479 restricted to the parameters defined in the optional domain and block
26482 @var{name} is the name of the symbol. It must be a string. The
26483 optional @var{block} argument restricts the search to symbols visible
26484 in that @var{block}. The @var{block} argument must be a
26485 @code{gdb.Block} object. If omitted, the block for the current frame
26486 is used. The optional @var{domain} argument restricts
26487 the search to the domain type. The @var{domain} argument must be a
26488 domain constant defined in the @code{gdb} module and described later
26491 The result is a tuple of two elements.
26492 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
26494 If the symbol is found, the second element is @code{True} if the symbol
26495 is a field of a method's object (e.g., @code{this} in C@t{++}),
26496 otherwise it is @code{False}.
26497 If the symbol is not found, the second element is @code{False}.
26500 @findex gdb.lookup_global_symbol
26501 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
26502 This function searches for a global symbol by name.
26503 The search scope can be restricted to by the domain argument.
26505 @var{name} is the name of the symbol. It must be a string.
26506 The optional @var{domain} argument restricts the search to the domain type.
26507 The @var{domain} argument must be a domain constant defined in the @code{gdb}
26508 module and described later in this chapter.
26510 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
26514 A @code{gdb.Symbol} object has the following attributes:
26516 @defvar Symbol.type
26517 The type of the symbol or @code{None} if no type is recorded.
26518 This attribute is represented as a @code{gdb.Type} object.
26519 @xref{Types In Python}. This attribute is not writable.
26522 @defvar Symbol.symtab
26523 The symbol table in which the symbol appears. This attribute is
26524 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
26525 Python}. This attribute is not writable.
26528 @defvar Symbol.line
26529 The line number in the source code at which the symbol was defined.
26530 This is an integer.
26533 @defvar Symbol.name
26534 The name of the symbol as a string. This attribute is not writable.
26537 @defvar Symbol.linkage_name
26538 The name of the symbol, as used by the linker (i.e., may be mangled).
26539 This attribute is not writable.
26542 @defvar Symbol.print_name
26543 The name of the symbol in a form suitable for output. This is either
26544 @code{name} or @code{linkage_name}, depending on whether the user
26545 asked @value{GDBN} to display demangled or mangled names.
26548 @defvar Symbol.addr_class
26549 The address class of the symbol. This classifies how to find the value
26550 of a symbol. Each address class is a constant defined in the
26551 @code{gdb} module and described later in this chapter.
26554 @defvar Symbol.needs_frame
26555 This is @code{True} if evaluating this symbol's value requires a frame
26556 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
26557 local variables will require a frame, but other symbols will not.
26560 @defvar Symbol.is_argument
26561 @code{True} if the symbol is an argument of a function.
26564 @defvar Symbol.is_constant
26565 @code{True} if the symbol is a constant.
26568 @defvar Symbol.is_function
26569 @code{True} if the symbol is a function or a method.
26572 @defvar Symbol.is_variable
26573 @code{True} if the symbol is a variable.
26576 A @code{gdb.Symbol} object has the following methods:
26578 @defun Symbol.is_valid ()
26579 Returns @code{True} if the @code{gdb.Symbol} object is valid,
26580 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
26581 the symbol it refers to does not exist in @value{GDBN} any longer.
26582 All other @code{gdb.Symbol} methods will throw an exception if it is
26583 invalid at the time the method is called.
26586 @defun Symbol.value (@r{[}frame@r{]})
26587 Compute the value of the symbol, as a @code{gdb.Value}. For
26588 functions, this computes the address of the function, cast to the
26589 appropriate type. If the symbol requires a frame in order to compute
26590 its value, then @var{frame} must be given. If @var{frame} is not
26591 given, or if @var{frame} is invalid, then this method will throw an
26595 The available domain categories in @code{gdb.Symbol} are represented
26596 as constants in the @code{gdb} module:
26599 @findex SYMBOL_UNDEF_DOMAIN
26600 @findex gdb.SYMBOL_UNDEF_DOMAIN
26601 @item gdb.SYMBOL_UNDEF_DOMAIN
26602 This is used when a domain has not been discovered or none of the
26603 following domains apply. This usually indicates an error either
26604 in the symbol information or in @value{GDBN}'s handling of symbols.
26605 @findex SYMBOL_VAR_DOMAIN
26606 @findex gdb.SYMBOL_VAR_DOMAIN
26607 @item gdb.SYMBOL_VAR_DOMAIN
26608 This domain contains variables, function names, typedef names and enum
26610 @findex SYMBOL_STRUCT_DOMAIN
26611 @findex gdb.SYMBOL_STRUCT_DOMAIN
26612 @item gdb.SYMBOL_STRUCT_DOMAIN
26613 This domain holds struct, union and enum type names.
26614 @findex SYMBOL_LABEL_DOMAIN
26615 @findex gdb.SYMBOL_LABEL_DOMAIN
26616 @item gdb.SYMBOL_LABEL_DOMAIN
26617 This domain contains names of labels (for gotos).
26618 @findex SYMBOL_VARIABLES_DOMAIN
26619 @findex gdb.SYMBOL_VARIABLES_DOMAIN
26620 @item gdb.SYMBOL_VARIABLES_DOMAIN
26621 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
26622 contains everything minus functions and types.
26623 @findex SYMBOL_FUNCTIONS_DOMAIN
26624 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
26625 @item gdb.SYMBOL_FUNCTION_DOMAIN
26626 This domain contains all functions.
26627 @findex SYMBOL_TYPES_DOMAIN
26628 @findex gdb.SYMBOL_TYPES_DOMAIN
26629 @item gdb.SYMBOL_TYPES_DOMAIN
26630 This domain contains all types.
26633 The available address class categories in @code{gdb.Symbol} are represented
26634 as constants in the @code{gdb} module:
26637 @findex SYMBOL_LOC_UNDEF
26638 @findex gdb.SYMBOL_LOC_UNDEF
26639 @item gdb.SYMBOL_LOC_UNDEF
26640 If this is returned by address class, it indicates an error either in
26641 the symbol information or in @value{GDBN}'s handling of symbols.
26642 @findex SYMBOL_LOC_CONST
26643 @findex gdb.SYMBOL_LOC_CONST
26644 @item gdb.SYMBOL_LOC_CONST
26645 Value is constant int.
26646 @findex SYMBOL_LOC_STATIC
26647 @findex gdb.SYMBOL_LOC_STATIC
26648 @item gdb.SYMBOL_LOC_STATIC
26649 Value is at a fixed address.
26650 @findex SYMBOL_LOC_REGISTER
26651 @findex gdb.SYMBOL_LOC_REGISTER
26652 @item gdb.SYMBOL_LOC_REGISTER
26653 Value is in a register.
26654 @findex SYMBOL_LOC_ARG
26655 @findex gdb.SYMBOL_LOC_ARG
26656 @item gdb.SYMBOL_LOC_ARG
26657 Value is an argument. This value is at the offset stored within the
26658 symbol inside the frame's argument list.
26659 @findex SYMBOL_LOC_REF_ARG
26660 @findex gdb.SYMBOL_LOC_REF_ARG
26661 @item gdb.SYMBOL_LOC_REF_ARG
26662 Value address is stored in the frame's argument list. Just like
26663 @code{LOC_ARG} except that the value's address is stored at the
26664 offset, not the value itself.
26665 @findex SYMBOL_LOC_REGPARM_ADDR
26666 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
26667 @item gdb.SYMBOL_LOC_REGPARM_ADDR
26668 Value is a specified register. Just like @code{LOC_REGISTER} except
26669 the register holds the address of the argument instead of the argument
26671 @findex SYMBOL_LOC_LOCAL
26672 @findex gdb.SYMBOL_LOC_LOCAL
26673 @item gdb.SYMBOL_LOC_LOCAL
26674 Value is a local variable.
26675 @findex SYMBOL_LOC_TYPEDEF
26676 @findex gdb.SYMBOL_LOC_TYPEDEF
26677 @item gdb.SYMBOL_LOC_TYPEDEF
26678 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
26680 @findex SYMBOL_LOC_BLOCK
26681 @findex gdb.SYMBOL_LOC_BLOCK
26682 @item gdb.SYMBOL_LOC_BLOCK
26684 @findex SYMBOL_LOC_CONST_BYTES
26685 @findex gdb.SYMBOL_LOC_CONST_BYTES
26686 @item gdb.SYMBOL_LOC_CONST_BYTES
26687 Value is a byte-sequence.
26688 @findex SYMBOL_LOC_UNRESOLVED
26689 @findex gdb.SYMBOL_LOC_UNRESOLVED
26690 @item gdb.SYMBOL_LOC_UNRESOLVED
26691 Value is at a fixed address, but the address of the variable has to be
26692 determined from the minimal symbol table whenever the variable is
26694 @findex SYMBOL_LOC_OPTIMIZED_OUT
26695 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
26696 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
26697 The value does not actually exist in the program.
26698 @findex SYMBOL_LOC_COMPUTED
26699 @findex gdb.SYMBOL_LOC_COMPUTED
26700 @item gdb.SYMBOL_LOC_COMPUTED
26701 The value's address is a computed location.
26704 @node Symbol Tables In Python
26705 @subsubsection Symbol table representation in Python.
26707 @cindex symbol tables in python
26709 @tindex gdb.Symtab_and_line
26711 Access to symbol table data maintained by @value{GDBN} on the inferior
26712 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
26713 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
26714 from the @code{find_sal} method in @code{gdb.Frame} object.
26715 @xref{Frames In Python}.
26717 For more information on @value{GDBN}'s symbol table management, see
26718 @ref{Symbols, ,Examining the Symbol Table}, for more information.
26720 A @code{gdb.Symtab_and_line} object has the following attributes:
26722 @defvar Symtab_and_line.symtab
26723 The symbol table object (@code{gdb.Symtab}) for this frame.
26724 This attribute is not writable.
26727 @defvar Symtab_and_line.pc
26728 Indicates the start of the address range occupied by code for the
26729 current source line. This attribute is not writable.
26732 @defvar Symtab_and_line.last
26733 Indicates the end of the address range occupied by code for the current
26734 source line. This attribute is not writable.
26737 @defvar Symtab_and_line.line
26738 Indicates the current line number for this object. This
26739 attribute is not writable.
26742 A @code{gdb.Symtab_and_line} object has the following methods:
26744 @defun Symtab_and_line.is_valid ()
26745 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
26746 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
26747 invalid if the Symbol table and line object it refers to does not
26748 exist in @value{GDBN} any longer. All other
26749 @code{gdb.Symtab_and_line} methods will throw an exception if it is
26750 invalid at the time the method is called.
26753 A @code{gdb.Symtab} object has the following attributes:
26755 @defvar Symtab.filename
26756 The symbol table's source filename. This attribute is not writable.
26759 @defvar Symtab.objfile
26760 The symbol table's backing object file. @xref{Objfiles In Python}.
26761 This attribute is not writable.
26764 A @code{gdb.Symtab} object has the following methods:
26766 @defun Symtab.is_valid ()
26767 Returns @code{True} if the @code{gdb.Symtab} object is valid,
26768 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
26769 the symbol table it refers to does not exist in @value{GDBN} any
26770 longer. All other @code{gdb.Symtab} methods will throw an exception
26771 if it is invalid at the time the method is called.
26774 @defun Symtab.fullname ()
26775 Return the symbol table's source absolute file name.
26778 @defun Symtab.global_block ()
26779 Return the global block of the underlying symbol table.
26780 @xref{Blocks In Python}.
26783 @defun Symtab.static_block ()
26784 Return the static block of the underlying symbol table.
26785 @xref{Blocks In Python}.
26788 @node Breakpoints In Python
26789 @subsubsection Manipulating breakpoints using Python
26791 @cindex breakpoints in python
26792 @tindex gdb.Breakpoint
26794 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
26797 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
26798 Create a new breakpoint. @var{spec} is a string naming the
26799 location of the breakpoint, or an expression that defines a
26800 watchpoint. The contents can be any location recognized by the
26801 @code{break} command, or in the case of a watchpoint, by the @code{watch}
26802 command. The optional @var{type} denotes the breakpoint to create
26803 from the types defined later in this chapter. This argument can be
26804 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
26805 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
26806 allows the breakpoint to become invisible to the user. The breakpoint
26807 will neither be reported when created, nor will it be listed in the
26808 output from @code{info breakpoints} (but will be listed with the
26809 @code{maint info breakpoints} command). The optional @var{wp_class}
26810 argument defines the class of watchpoint to create, if @var{type} is
26811 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
26812 assumed to be a @code{gdb.WP_WRITE} class.
26815 @defun Breakpoint.stop (self)
26816 The @code{gdb.Breakpoint} class can be sub-classed and, in
26817 particular, you may choose to implement the @code{stop} method.
26818 If this method is defined as a sub-class of @code{gdb.Breakpoint},
26819 it will be called when the inferior reaches any location of a
26820 breakpoint which instantiates that sub-class. If the method returns
26821 @code{True}, the inferior will be stopped at the location of the
26822 breakpoint, otherwise the inferior will continue.
26824 If there are multiple breakpoints at the same location with a
26825 @code{stop} method, each one will be called regardless of the
26826 return status of the previous. This ensures that all @code{stop}
26827 methods have a chance to execute at that location. In this scenario
26828 if one of the methods returns @code{True} but the others return
26829 @code{False}, the inferior will still be stopped.
26831 You should not alter the execution state of the inferior (i.e.@:, step,
26832 next, etc.), alter the current frame context (i.e.@:, change the current
26833 active frame), or alter, add or delete any breakpoint. As a general
26834 rule, you should not alter any data within @value{GDBN} or the inferior
26837 Example @code{stop} implementation:
26840 class MyBreakpoint (gdb.Breakpoint):
26842 inf_val = gdb.parse_and_eval("foo")
26849 The available watchpoint types represented by constants are defined in the
26854 @findex gdb.WP_READ
26856 Read only watchpoint.
26859 @findex gdb.WP_WRITE
26861 Write only watchpoint.
26864 @findex gdb.WP_ACCESS
26865 @item gdb.WP_ACCESS
26866 Read/Write watchpoint.
26869 @defun Breakpoint.is_valid ()
26870 Return @code{True} if this @code{Breakpoint} object is valid,
26871 @code{False} otherwise. A @code{Breakpoint} object can become invalid
26872 if the user deletes the breakpoint. In this case, the object still
26873 exists, but the underlying breakpoint does not. In the cases of
26874 watchpoint scope, the watchpoint remains valid even if execution of the
26875 inferior leaves the scope of that watchpoint.
26878 @defun Breakpoint.delete
26879 Permanently deletes the @value{GDBN} breakpoint. This also
26880 invalidates the Python @code{Breakpoint} object. Any further access
26881 to this object's attributes or methods will raise an error.
26884 @defvar Breakpoint.enabled
26885 This attribute is @code{True} if the breakpoint is enabled, and
26886 @code{False} otherwise. This attribute is writable.
26889 @defvar Breakpoint.silent
26890 This attribute is @code{True} if the breakpoint is silent, and
26891 @code{False} otherwise. This attribute is writable.
26893 Note that a breakpoint can also be silent if it has commands and the
26894 first command is @code{silent}. This is not reported by the
26895 @code{silent} attribute.
26898 @defvar Breakpoint.thread
26899 If the breakpoint is thread-specific, this attribute holds the thread
26900 id. If the breakpoint is not thread-specific, this attribute is
26901 @code{None}. This attribute is writable.
26904 @defvar Breakpoint.task
26905 If the breakpoint is Ada task-specific, this attribute holds the Ada task
26906 id. If the breakpoint is not task-specific (or the underlying
26907 language is not Ada), this attribute is @code{None}. This attribute
26911 @defvar Breakpoint.ignore_count
26912 This attribute holds the ignore count for the breakpoint, an integer.
26913 This attribute is writable.
26916 @defvar Breakpoint.number
26917 This attribute holds the breakpoint's number --- the identifier used by
26918 the user to manipulate the breakpoint. This attribute is not writable.
26921 @defvar Breakpoint.type
26922 This attribute holds the breakpoint's type --- the identifier used to
26923 determine the actual breakpoint type or use-case. This attribute is not
26927 @defvar Breakpoint.visible
26928 This attribute tells whether the breakpoint is visible to the user
26929 when set, or when the @samp{info breakpoints} command is run. This
26930 attribute is not writable.
26933 The available types are represented by constants defined in the @code{gdb}
26937 @findex BP_BREAKPOINT
26938 @findex gdb.BP_BREAKPOINT
26939 @item gdb.BP_BREAKPOINT
26940 Normal code breakpoint.
26942 @findex BP_WATCHPOINT
26943 @findex gdb.BP_WATCHPOINT
26944 @item gdb.BP_WATCHPOINT
26945 Watchpoint breakpoint.
26947 @findex BP_HARDWARE_WATCHPOINT
26948 @findex gdb.BP_HARDWARE_WATCHPOINT
26949 @item gdb.BP_HARDWARE_WATCHPOINT
26950 Hardware assisted watchpoint.
26952 @findex BP_READ_WATCHPOINT
26953 @findex gdb.BP_READ_WATCHPOINT
26954 @item gdb.BP_READ_WATCHPOINT
26955 Hardware assisted read watchpoint.
26957 @findex BP_ACCESS_WATCHPOINT
26958 @findex gdb.BP_ACCESS_WATCHPOINT
26959 @item gdb.BP_ACCESS_WATCHPOINT
26960 Hardware assisted access watchpoint.
26963 @defvar Breakpoint.hit_count
26964 This attribute holds the hit count for the breakpoint, an integer.
26965 This attribute is writable, but currently it can only be set to zero.
26968 @defvar Breakpoint.location
26969 This attribute holds the location of the breakpoint, as specified by
26970 the user. It is a string. If the breakpoint does not have a location
26971 (that is, it is a watchpoint) the attribute's value is @code{None}. This
26972 attribute is not writable.
26975 @defvar Breakpoint.expression
26976 This attribute holds a breakpoint expression, as specified by
26977 the user. It is a string. If the breakpoint does not have an
26978 expression (the breakpoint is not a watchpoint) the attribute's value
26979 is @code{None}. This attribute is not writable.
26982 @defvar Breakpoint.condition
26983 This attribute holds the condition of the breakpoint, as specified by
26984 the user. It is a string. If there is no condition, this attribute's
26985 value is @code{None}. This attribute is writable.
26988 @defvar Breakpoint.commands
26989 This attribute holds the commands attached to the breakpoint. If
26990 there are commands, this attribute's value is a string holding all the
26991 commands, separated by newlines. If there are no commands, this
26992 attribute is @code{None}. This attribute is not writable.
26995 @node Finish Breakpoints in Python
26996 @subsubsection Finish Breakpoints
26998 @cindex python finish breakpoints
26999 @tindex gdb.FinishBreakpoint
27001 A finish breakpoint is a temporary breakpoint set at the return address of
27002 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
27003 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
27004 and deleted when the execution will run out of the breakpoint scope (i.e.@:
27005 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
27006 Finish breakpoints are thread specific and must be create with the right
27009 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
27010 Create a finish breakpoint at the return address of the @code{gdb.Frame}
27011 object @var{frame}. If @var{frame} is not provided, this defaults to the
27012 newest frame. The optional @var{internal} argument allows the breakpoint to
27013 become invisible to the user. @xref{Breakpoints In Python}, for further
27014 details about this argument.
27017 @defun FinishBreakpoint.out_of_scope (self)
27018 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
27019 @code{return} command, @dots{}), a function may not properly terminate, and
27020 thus never hit the finish breakpoint. When @value{GDBN} notices such a
27021 situation, the @code{out_of_scope} callback will be triggered.
27023 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
27027 class MyFinishBreakpoint (gdb.FinishBreakpoint)
27029 print "normal finish"
27032 def out_of_scope ():
27033 print "abnormal finish"
27037 @defvar FinishBreakpoint.return_value
27038 When @value{GDBN} is stopped at a finish breakpoint and the frame
27039 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
27040 attribute will contain a @code{gdb.Value} object corresponding to the return
27041 value of the function. The value will be @code{None} if the function return
27042 type is @code{void} or if the return value was not computable. This attribute
27046 @node Lazy Strings In Python
27047 @subsubsection Python representation of lazy strings.
27049 @cindex lazy strings in python
27050 @tindex gdb.LazyString
27052 A @dfn{lazy string} is a string whose contents is not retrieved or
27053 encoded until it is needed.
27055 A @code{gdb.LazyString} is represented in @value{GDBN} as an
27056 @code{address} that points to a region of memory, an @code{encoding}
27057 that will be used to encode that region of memory, and a @code{length}
27058 to delimit the region of memory that represents the string. The
27059 difference between a @code{gdb.LazyString} and a string wrapped within
27060 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
27061 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
27062 retrieved and encoded during printing, while a @code{gdb.Value}
27063 wrapping a string is immediately retrieved and encoded on creation.
27065 A @code{gdb.LazyString} object has the following functions:
27067 @defun LazyString.value ()
27068 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
27069 will point to the string in memory, but will lose all the delayed
27070 retrieval, encoding and handling that @value{GDBN} applies to a
27071 @code{gdb.LazyString}.
27074 @defvar LazyString.address
27075 This attribute holds the address of the string. This attribute is not
27079 @defvar LazyString.length
27080 This attribute holds the length of the string in characters. If the
27081 length is -1, then the string will be fetched and encoded up to the
27082 first null of appropriate width. This attribute is not writable.
27085 @defvar LazyString.encoding
27086 This attribute holds the encoding that will be applied to the string
27087 when the string is printed by @value{GDBN}. If the encoding is not
27088 set, or contains an empty string, then @value{GDBN} will select the
27089 most appropriate encoding when the string is printed. This attribute
27093 @defvar LazyString.type
27094 This attribute holds the type that is represented by the lazy string's
27095 type. For a lazy string this will always be a pointer type. To
27096 resolve this to the lazy string's character type, use the type's
27097 @code{target} method. @xref{Types In Python}. This attribute is not
27101 @node Architectures In Python
27102 @subsubsection Python representation of architectures
27103 @cindex Python architectures
27105 @value{GDBN} uses architecture specific parameters and artifacts in a
27106 number of its various computations. An architecture is represented
27107 by an instance of the @code{gdb.Architecture} class.
27109 A @code{gdb.Architecture} class has the following methods:
27111 @defun Architecture.name ()
27112 Return the name (string value) of the architecture.
27115 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
27116 Return a list of disassembled instructions starting from the memory
27117 address @var{start_pc}. The optional arguments @var{end_pc} and
27118 @var{count} determine the number of instructions in the returned list.
27119 If both the optional arguments @var{end_pc} and @var{count} are
27120 specified, then a list of at most @var{count} disassembled instructions
27121 whose start address falls in the closed memory address interval from
27122 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
27123 specified, but @var{count} is specified, then @var{count} number of
27124 instructions starting from the address @var{start_pc} are returned. If
27125 @var{count} is not specified but @var{end_pc} is specified, then all
27126 instructions whose start address falls in the closed memory address
27127 interval from @var{start_pc} to @var{end_pc} are returned. If neither
27128 @var{end_pc} nor @var{count} are specified, then a single instruction at
27129 @var{start_pc} is returned. For all of these cases, each element of the
27130 returned list is a Python @code{dict} with the following string keys:
27135 The value corresponding to this key is a Python long integer capturing
27136 the memory address of the instruction.
27139 The value corresponding to this key is a string value which represents
27140 the instruction with assembly language mnemonics. The assembly
27141 language flavor used is the same as that specified by the current CLI
27142 variable @code{disassembly-flavor}. @xref{Machine Code}.
27145 The value corresponding to this key is the length (integer value) of the
27146 instruction in bytes.
27151 @node Python Auto-loading
27152 @subsection Python Auto-loading
27153 @cindex Python auto-loading
27155 When a new object file is read (for example, due to the @code{file}
27156 command, or because the inferior has loaded a shared library),
27157 @value{GDBN} will look for Python support scripts in several ways:
27158 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
27159 and @code{.debug_gdb_scripts} section
27160 (@pxref{dotdebug_gdb_scripts section}).
27162 The auto-loading feature is useful for supplying application-specific
27163 debugging commands and scripts.
27165 Auto-loading can be enabled or disabled,
27166 and the list of auto-loaded scripts can be printed.
27169 @anchor{set auto-load python-scripts}
27170 @kindex set auto-load python-scripts
27171 @item set auto-load python-scripts [on|off]
27172 Enable or disable the auto-loading of Python scripts.
27174 @anchor{show auto-load python-scripts}
27175 @kindex show auto-load python-scripts
27176 @item show auto-load python-scripts
27177 Show whether auto-loading of Python scripts is enabled or disabled.
27179 @anchor{info auto-load python-scripts}
27180 @kindex info auto-load python-scripts
27181 @cindex print list of auto-loaded Python scripts
27182 @item info auto-load python-scripts [@var{regexp}]
27183 Print the list of all Python scripts that @value{GDBN} auto-loaded.
27185 Also printed is the list of Python scripts that were mentioned in
27186 the @code{.debug_gdb_scripts} section and were not found
27187 (@pxref{dotdebug_gdb_scripts section}).
27188 This is useful because their names are not printed when @value{GDBN}
27189 tries to load them and fails. There may be many of them, and printing
27190 an error message for each one is problematic.
27192 If @var{regexp} is supplied only Python scripts with matching names are printed.
27197 (gdb) info auto-load python-scripts
27199 Yes py-section-script.py
27200 full name: /tmp/py-section-script.py
27201 No my-foo-pretty-printers.py
27205 When reading an auto-loaded file, @value{GDBN} sets the
27206 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
27207 function (@pxref{Objfiles In Python}). This can be useful for
27208 registering objfile-specific pretty-printers and frame-filters.
27211 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
27212 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
27213 * Which flavor to choose?::
27216 @node objfile-gdb.py file
27217 @subsubsection The @file{@var{objfile}-gdb.py} file
27218 @cindex @file{@var{objfile}-gdb.py}
27220 When a new object file is read, @value{GDBN} looks for
27221 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
27222 where @var{objfile} is the object file's real name, formed by ensuring
27223 that the file name is absolute, following all symlinks, and resolving
27224 @code{.} and @code{..} components. If this file exists and is
27225 readable, @value{GDBN} will evaluate it as a Python script.
27227 If this file does not exist, then @value{GDBN} will look for
27228 @var{script-name} file in all of the directories as specified below.
27230 Note that loading of this script file also requires accordingly configured
27231 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27233 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
27234 scripts normally according to its @file{.exe} filename. But if no scripts are
27235 found @value{GDBN} also tries script filenames matching the object file without
27236 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
27237 is attempted on any platform. This makes the script filenames compatible
27238 between Unix and MS-Windows hosts.
27241 @anchor{set auto-load scripts-directory}
27242 @kindex set auto-load scripts-directory
27243 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
27244 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
27245 may be delimited by the host platform path separator in use
27246 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
27248 Each entry here needs to be covered also by the security setting
27249 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
27251 @anchor{with-auto-load-dir}
27252 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
27253 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
27254 configuration option @option{--with-auto-load-dir}.
27256 Any reference to @file{$debugdir} will get replaced by
27257 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
27258 reference to @file{$datadir} will get replaced by @var{data-directory} which is
27259 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
27260 @file{$datadir} must be placed as a directory component --- either alone or
27261 delimited by @file{/} or @file{\} directory separators, depending on the host
27264 The list of directories uses path separator (@samp{:} on GNU and Unix
27265 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
27266 to the @env{PATH} environment variable.
27268 @anchor{show auto-load scripts-directory}
27269 @kindex show auto-load scripts-directory
27270 @item show auto-load scripts-directory
27271 Show @value{GDBN} auto-loaded scripts location.
27274 @value{GDBN} does not track which files it has already auto-loaded this way.
27275 @value{GDBN} will load the associated script every time the corresponding
27276 @var{objfile} is opened.
27277 So your @file{-gdb.py} file should be careful to avoid errors if it
27278 is evaluated more than once.
27280 @node dotdebug_gdb_scripts section
27281 @subsubsection The @code{.debug_gdb_scripts} section
27282 @cindex @code{.debug_gdb_scripts} section
27284 For systems using file formats like ELF and COFF,
27285 when @value{GDBN} loads a new object file
27286 it will look for a special section named @samp{.debug_gdb_scripts}.
27287 If this section exists, its contents is a list of names of scripts to load.
27289 @value{GDBN} will look for each specified script file first in the
27290 current directory and then along the source search path
27291 (@pxref{Source Path, ,Specifying Source Directories}),
27292 except that @file{$cdir} is not searched, since the compilation
27293 directory is not relevant to scripts.
27295 Entries can be placed in section @code{.debug_gdb_scripts} with,
27296 for example, this GCC macro:
27299 /* Note: The "MS" section flags are to remove duplicates. */
27300 #define DEFINE_GDB_SCRIPT(script_name) \
27302 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
27304 .asciz \"" script_name "\"\n\
27310 Then one can reference the macro in a header or source file like this:
27313 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
27316 The script name may include directories if desired.
27318 Note that loading of this script file also requires accordingly configured
27319 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
27321 If the macro is put in a header, any application or library
27322 using this header will get a reference to the specified script.
27324 @node Which flavor to choose?
27325 @subsubsection Which flavor to choose?
27327 Given the multiple ways of auto-loading Python scripts, it might not always
27328 be clear which one to choose. This section provides some guidance.
27330 Benefits of the @file{-gdb.py} way:
27334 Can be used with file formats that don't support multiple sections.
27337 Ease of finding scripts for public libraries.
27339 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
27340 in the source search path.
27341 For publicly installed libraries, e.g., @file{libstdc++}, there typically
27342 isn't a source directory in which to find the script.
27345 Doesn't require source code additions.
27348 Benefits of the @code{.debug_gdb_scripts} way:
27352 Works with static linking.
27354 Scripts for libraries done the @file{-gdb.py} way require an objfile to
27355 trigger their loading. When an application is statically linked the only
27356 objfile available is the executable, and it is cumbersome to attach all the
27357 scripts from all the input libraries to the executable's @file{-gdb.py} script.
27360 Works with classes that are entirely inlined.
27362 Some classes can be entirely inlined, and thus there may not be an associated
27363 shared library to attach a @file{-gdb.py} script to.
27366 Scripts needn't be copied out of the source tree.
27368 In some circumstances, apps can be built out of large collections of internal
27369 libraries, and the build infrastructure necessary to install the
27370 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
27371 cumbersome. It may be easier to specify the scripts in the
27372 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
27373 top of the source tree to the source search path.
27376 @node Python modules
27377 @subsection Python modules
27378 @cindex python modules
27380 @value{GDBN} comes with several modules to assist writing Python code.
27383 * gdb.printing:: Building and registering pretty-printers.
27384 * gdb.types:: Utilities for working with types.
27385 * gdb.prompt:: Utilities for prompt value substitution.
27389 @subsubsection gdb.printing
27390 @cindex gdb.printing
27392 This module provides a collection of utilities for working with
27396 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
27397 This class specifies the API that makes @samp{info pretty-printer},
27398 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
27399 Pretty-printers should generally inherit from this class.
27401 @item SubPrettyPrinter (@var{name})
27402 For printers that handle multiple types, this class specifies the
27403 corresponding API for the subprinters.
27405 @item RegexpCollectionPrettyPrinter (@var{name})
27406 Utility class for handling multiple printers, all recognized via
27407 regular expressions.
27408 @xref{Writing a Pretty-Printer}, for an example.
27410 @item FlagEnumerationPrinter (@var{name})
27411 A pretty-printer which handles printing of @code{enum} values. Unlike
27412 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
27413 work properly when there is some overlap between the enumeration
27414 constants. @var{name} is the name of the printer and also the name of
27415 the @code{enum} type to look up.
27417 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
27418 Register @var{printer} with the pretty-printer list of @var{obj}.
27419 If @var{replace} is @code{True} then any existing copy of the printer
27420 is replaced. Otherwise a @code{RuntimeError} exception is raised
27421 if a printer with the same name already exists.
27425 @subsubsection gdb.types
27428 This module provides a collection of utilities for working with
27429 @code{gdb.Type} objects.
27432 @item get_basic_type (@var{type})
27433 Return @var{type} with const and volatile qualifiers stripped,
27434 and with typedefs and C@t{++} references converted to the underlying type.
27439 typedef const int const_int;
27441 const_int& foo_ref (foo);
27442 int main () @{ return 0; @}
27449 (gdb) python import gdb.types
27450 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
27451 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
27455 @item has_field (@var{type}, @var{field})
27456 Return @code{True} if @var{type}, assumed to be a type with fields
27457 (e.g., a structure or union), has field @var{field}.
27459 @item make_enum_dict (@var{enum_type})
27460 Return a Python @code{dictionary} type produced from @var{enum_type}.
27462 @item deep_items (@var{type})
27463 Returns a Python iterator similar to the standard
27464 @code{gdb.Type.iteritems} method, except that the iterator returned
27465 by @code{deep_items} will recursively traverse anonymous struct or
27466 union fields. For example:
27480 Then in @value{GDBN}:
27482 (@value{GDBP}) python import gdb.types
27483 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
27484 (@value{GDBP}) python print struct_a.keys ()
27486 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
27487 @{['a', 'b0', 'b1']@}
27490 @item get_type_recognizers ()
27491 Return a list of the enabled type recognizers for the current context.
27492 This is called by @value{GDBN} during the type-printing process
27493 (@pxref{Type Printing API}).
27495 @item apply_type_recognizers (recognizers, type_obj)
27496 Apply the type recognizers, @var{recognizers}, to the type object
27497 @var{type_obj}. If any recognizer returns a string, return that
27498 string. Otherwise, return @code{None}. This is called by
27499 @value{GDBN} during the type-printing process (@pxref{Type Printing
27502 @item register_type_printer (locus, printer)
27503 This is a convenience function to register a type printer.
27504 @var{printer} is the type printer to register. It must implement the
27505 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
27506 which case the printer is registered with that objfile; a
27507 @code{gdb.Progspace}, in which case the printer is registered with
27508 that progspace; or @code{None}, in which case the printer is
27509 registered globally.
27512 This is a base class that implements the type printer protocol. Type
27513 printers are encouraged, but not required, to derive from this class.
27514 It defines a constructor:
27516 @defmethod TypePrinter __init__ (self, name)
27517 Initialize the type printer with the given name. The new printer
27518 starts in the enabled state.
27524 @subsubsection gdb.prompt
27527 This module provides a method for prompt value-substitution.
27530 @item substitute_prompt (@var{string})
27531 Return @var{string} with escape sequences substituted by values. Some
27532 escape sequences take arguments. You can specify arguments inside
27533 ``@{@}'' immediately following the escape sequence.
27535 The escape sequences you can pass to this function are:
27539 Substitute a backslash.
27541 Substitute an ESC character.
27543 Substitute the selected frame; an argument names a frame parameter.
27545 Substitute a newline.
27547 Substitute a parameter's value; the argument names the parameter.
27549 Substitute a carriage return.
27551 Substitute the selected thread; an argument names a thread parameter.
27553 Substitute the version of GDB.
27555 Substitute the current working directory.
27557 Begin a sequence of non-printing characters. These sequences are
27558 typically used with the ESC character, and are not counted in the string
27559 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
27560 blue-colored ``(gdb)'' prompt where the length is five.
27562 End a sequence of non-printing characters.
27568 substitute_prompt (``frame: \f,
27569 print arguments: \p@{print frame-arguments@}'')
27572 @exdent will return the string:
27575 "frame: main, print arguments: scalars"
27580 @section Creating new spellings of existing commands
27581 @cindex aliases for commands
27583 It is often useful to define alternate spellings of existing commands.
27584 For example, if a new @value{GDBN} command defined in Python has
27585 a long name to type, it is handy to have an abbreviated version of it
27586 that involves less typing.
27588 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
27589 of the @samp{step} command even though it is otherwise an ambiguous
27590 abbreviation of other commands like @samp{set} and @samp{show}.
27592 Aliases are also used to provide shortened or more common versions
27593 of multi-word commands. For example, @value{GDBN} provides the
27594 @samp{tty} alias of the @samp{set inferior-tty} command.
27596 You can define a new alias with the @samp{alias} command.
27601 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
27605 @var{ALIAS} specifies the name of the new alias.
27606 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
27609 @var{COMMAND} specifies the name of an existing command
27610 that is being aliased.
27612 The @samp{-a} option specifies that the new alias is an abbreviation
27613 of the command. Abbreviations are not shown in command
27614 lists displayed by the @samp{help} command.
27616 The @samp{--} option specifies the end of options,
27617 and is useful when @var{ALIAS} begins with a dash.
27619 Here is a simple example showing how to make an abbreviation
27620 of a command so that there is less to type.
27621 Suppose you were tired of typing @samp{disas}, the current
27622 shortest unambiguous abbreviation of the @samp{disassemble} command
27623 and you wanted an even shorter version named @samp{di}.
27624 The following will accomplish this.
27627 (gdb) alias -a di = disas
27630 Note that aliases are different from user-defined commands.
27631 With a user-defined command, you also need to write documentation
27632 for it with the @samp{document} command.
27633 An alias automatically picks up the documentation of the existing command.
27635 Here is an example where we make @samp{elms} an abbreviation of
27636 @samp{elements} in the @samp{set print elements} command.
27637 This is to show that you can make an abbreviation of any part
27641 (gdb) alias -a set print elms = set print elements
27642 (gdb) alias -a show print elms = show print elements
27643 (gdb) set p elms 20
27645 Limit on string chars or array elements to print is 200.
27648 Note that if you are defining an alias of a @samp{set} command,
27649 and you want to have an alias for the corresponding @samp{show}
27650 command, then you need to define the latter separately.
27652 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
27653 @var{ALIAS}, just as they are normally.
27656 (gdb) alias -a set pr elms = set p ele
27659 Finally, here is an example showing the creation of a one word
27660 alias for a more complex command.
27661 This creates alias @samp{spe} of the command @samp{set print elements}.
27664 (gdb) alias spe = set print elements
27669 @chapter Command Interpreters
27670 @cindex command interpreters
27672 @value{GDBN} supports multiple command interpreters, and some command
27673 infrastructure to allow users or user interface writers to switch
27674 between interpreters or run commands in other interpreters.
27676 @value{GDBN} currently supports two command interpreters, the console
27677 interpreter (sometimes called the command-line interpreter or @sc{cli})
27678 and the machine interface interpreter (or @sc{gdb/mi}). This manual
27679 describes both of these interfaces in great detail.
27681 By default, @value{GDBN} will start with the console interpreter.
27682 However, the user may choose to start @value{GDBN} with another
27683 interpreter by specifying the @option{-i} or @option{--interpreter}
27684 startup options. Defined interpreters include:
27688 @cindex console interpreter
27689 The traditional console or command-line interpreter. This is the most often
27690 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
27691 @value{GDBN} will use this interpreter.
27694 @cindex mi interpreter
27695 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
27696 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
27697 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
27701 @cindex mi2 interpreter
27702 The current @sc{gdb/mi} interface.
27705 @cindex mi1 interpreter
27706 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
27710 @cindex invoke another interpreter
27711 The interpreter being used by @value{GDBN} may not be dynamically
27712 switched at runtime. Although possible, this could lead to a very
27713 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
27714 enters the command "interpreter-set console" in a console view,
27715 @value{GDBN} would switch to using the console interpreter, rendering
27716 the IDE inoperable!
27718 @kindex interpreter-exec
27719 Although you may only choose a single interpreter at startup, you may execute
27720 commands in any interpreter from the current interpreter using the appropriate
27721 command. If you are running the console interpreter, simply use the
27722 @code{interpreter-exec} command:
27725 interpreter-exec mi "-data-list-register-names"
27728 @sc{gdb/mi} has a similar command, although it is only available in versions of
27729 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
27732 @chapter @value{GDBN} Text User Interface
27734 @cindex Text User Interface
27737 * TUI Overview:: TUI overview
27738 * TUI Keys:: TUI key bindings
27739 * TUI Single Key Mode:: TUI single key mode
27740 * TUI Commands:: TUI-specific commands
27741 * TUI Configuration:: TUI configuration variables
27744 The @value{GDBN} Text User Interface (TUI) is a terminal
27745 interface which uses the @code{curses} library to show the source
27746 file, the assembly output, the program registers and @value{GDBN}
27747 commands in separate text windows. The TUI mode is supported only
27748 on platforms where a suitable version of the @code{curses} library
27751 The TUI mode is enabled by default when you invoke @value{GDBN} as
27752 @samp{@value{GDBP} -tui}.
27753 You can also switch in and out of TUI mode while @value{GDBN} runs by
27754 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
27755 @xref{TUI Keys, ,TUI Key Bindings}.
27758 @section TUI Overview
27760 In TUI mode, @value{GDBN} can display several text windows:
27764 This window is the @value{GDBN} command window with the @value{GDBN}
27765 prompt and the @value{GDBN} output. The @value{GDBN} input is still
27766 managed using readline.
27769 The source window shows the source file of the program. The current
27770 line and active breakpoints are displayed in this window.
27773 The assembly window shows the disassembly output of the program.
27776 This window shows the processor registers. Registers are highlighted
27777 when their values change.
27780 The source and assembly windows show the current program position
27781 by highlighting the current line and marking it with a @samp{>} marker.
27782 Breakpoints are indicated with two markers. The first marker
27783 indicates the breakpoint type:
27787 Breakpoint which was hit at least once.
27790 Breakpoint which was never hit.
27793 Hardware breakpoint which was hit at least once.
27796 Hardware breakpoint which was never hit.
27799 The second marker indicates whether the breakpoint is enabled or not:
27803 Breakpoint is enabled.
27806 Breakpoint is disabled.
27809 The source, assembly and register windows are updated when the current
27810 thread changes, when the frame changes, or when the program counter
27813 These windows are not all visible at the same time. The command
27814 window is always visible. The others can be arranged in several
27825 source and assembly,
27828 source and registers, or
27831 assembly and registers.
27834 A status line above the command window shows the following information:
27838 Indicates the current @value{GDBN} target.
27839 (@pxref{Targets, ,Specifying a Debugging Target}).
27842 Gives the current process or thread number.
27843 When no process is being debugged, this field is set to @code{No process}.
27846 Gives the current function name for the selected frame.
27847 The name is demangled if demangling is turned on (@pxref{Print Settings}).
27848 When there is no symbol corresponding to the current program counter,
27849 the string @code{??} is displayed.
27852 Indicates the current line number for the selected frame.
27853 When the current line number is not known, the string @code{??} is displayed.
27856 Indicates the current program counter address.
27860 @section TUI Key Bindings
27861 @cindex TUI key bindings
27863 The TUI installs several key bindings in the readline keymaps
27864 @ifset SYSTEM_READLINE
27865 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
27867 @ifclear SYSTEM_READLINE
27868 (@pxref{Command Line Editing}).
27870 The following key bindings are installed for both TUI mode and the
27871 @value{GDBN} standard mode.
27880 Enter or leave the TUI mode. When leaving the TUI mode,
27881 the curses window management stops and @value{GDBN} operates using
27882 its standard mode, writing on the terminal directly. When reentering
27883 the TUI mode, control is given back to the curses windows.
27884 The screen is then refreshed.
27888 Use a TUI layout with only one window. The layout will
27889 either be @samp{source} or @samp{assembly}. When the TUI mode
27890 is not active, it will switch to the TUI mode.
27892 Think of this key binding as the Emacs @kbd{C-x 1} binding.
27896 Use a TUI layout with at least two windows. When the current
27897 layout already has two windows, the next layout with two windows is used.
27898 When a new layout is chosen, one window will always be common to the
27899 previous layout and the new one.
27901 Think of it as the Emacs @kbd{C-x 2} binding.
27905 Change the active window. The TUI associates several key bindings
27906 (like scrolling and arrow keys) with the active window. This command
27907 gives the focus to the next TUI window.
27909 Think of it as the Emacs @kbd{C-x o} binding.
27913 Switch in and out of the TUI SingleKey mode that binds single
27914 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
27917 The following key bindings only work in the TUI mode:
27922 Scroll the active window one page up.
27926 Scroll the active window one page down.
27930 Scroll the active window one line up.
27934 Scroll the active window one line down.
27938 Scroll the active window one column left.
27942 Scroll the active window one column right.
27946 Refresh the screen.
27949 Because the arrow keys scroll the active window in the TUI mode, they
27950 are not available for their normal use by readline unless the command
27951 window has the focus. When another window is active, you must use
27952 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
27953 and @kbd{C-f} to control the command window.
27955 @node TUI Single Key Mode
27956 @section TUI Single Key Mode
27957 @cindex TUI single key mode
27959 The TUI also provides a @dfn{SingleKey} mode, which binds several
27960 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
27961 switch into this mode, where the following key bindings are used:
27964 @kindex c @r{(SingleKey TUI key)}
27968 @kindex d @r{(SingleKey TUI key)}
27972 @kindex f @r{(SingleKey TUI key)}
27976 @kindex n @r{(SingleKey TUI key)}
27980 @kindex q @r{(SingleKey TUI key)}
27982 exit the SingleKey mode.
27984 @kindex r @r{(SingleKey TUI key)}
27988 @kindex s @r{(SingleKey TUI key)}
27992 @kindex u @r{(SingleKey TUI key)}
27996 @kindex v @r{(SingleKey TUI key)}
28000 @kindex w @r{(SingleKey TUI key)}
28005 Other keys temporarily switch to the @value{GDBN} command prompt.
28006 The key that was pressed is inserted in the editing buffer so that
28007 it is possible to type most @value{GDBN} commands without interaction
28008 with the TUI SingleKey mode. Once the command is entered the TUI
28009 SingleKey mode is restored. The only way to permanently leave
28010 this mode is by typing @kbd{q} or @kbd{C-x s}.
28014 @section TUI-specific Commands
28015 @cindex TUI commands
28017 The TUI has specific commands to control the text windows.
28018 These commands are always available, even when @value{GDBN} is not in
28019 the TUI mode. When @value{GDBN} is in the standard mode, most
28020 of these commands will automatically switch to the TUI mode.
28022 Note that if @value{GDBN}'s @code{stdout} is not connected to a
28023 terminal, or @value{GDBN} has been started with the machine interface
28024 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
28025 these commands will fail with an error, because it would not be
28026 possible or desirable to enable curses window management.
28031 List and give the size of all displayed windows.
28035 Display the next layout.
28038 Display the previous layout.
28041 Display the source window only.
28044 Display the assembly window only.
28047 Display the source and assembly window.
28050 Display the register window together with the source or assembly window.
28054 Make the next window active for scrolling.
28057 Make the previous window active for scrolling.
28060 Make the source window active for scrolling.
28063 Make the assembly window active for scrolling.
28066 Make the register window active for scrolling.
28069 Make the command window active for scrolling.
28073 Refresh the screen. This is similar to typing @kbd{C-L}.
28075 @item tui reg float
28077 Show the floating point registers in the register window.
28079 @item tui reg general
28080 Show the general registers in the register window.
28083 Show the next register group. The list of register groups as well as
28084 their order is target specific. The predefined register groups are the
28085 following: @code{general}, @code{float}, @code{system}, @code{vector},
28086 @code{all}, @code{save}, @code{restore}.
28088 @item tui reg system
28089 Show the system registers in the register window.
28093 Update the source window and the current execution point.
28095 @item winheight @var{name} +@var{count}
28096 @itemx winheight @var{name} -@var{count}
28098 Change the height of the window @var{name} by @var{count}
28099 lines. Positive counts increase the height, while negative counts
28102 @item tabset @var{nchars}
28104 Set the width of tab stops to be @var{nchars} characters.
28107 @node TUI Configuration
28108 @section TUI Configuration Variables
28109 @cindex TUI configuration variables
28111 Several configuration variables control the appearance of TUI windows.
28114 @item set tui border-kind @var{kind}
28115 @kindex set tui border-kind
28116 Select the border appearance for the source, assembly and register windows.
28117 The possible values are the following:
28120 Use a space character to draw the border.
28123 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
28126 Use the Alternate Character Set to draw the border. The border is
28127 drawn using character line graphics if the terminal supports them.
28130 @item set tui border-mode @var{mode}
28131 @kindex set tui border-mode
28132 @itemx set tui active-border-mode @var{mode}
28133 @kindex set tui active-border-mode
28134 Select the display attributes for the borders of the inactive windows
28135 or the active window. The @var{mode} can be one of the following:
28138 Use normal attributes to display the border.
28144 Use reverse video mode.
28147 Use half bright mode.
28149 @item half-standout
28150 Use half bright and standout mode.
28153 Use extra bright or bold mode.
28155 @item bold-standout
28156 Use extra bright or bold and standout mode.
28161 @chapter Using @value{GDBN} under @sc{gnu} Emacs
28164 @cindex @sc{gnu} Emacs
28165 A special interface allows you to use @sc{gnu} Emacs to view (and
28166 edit) the source files for the program you are debugging with
28169 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
28170 executable file you want to debug as an argument. This command starts
28171 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
28172 created Emacs buffer.
28173 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
28175 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
28180 All ``terminal'' input and output goes through an Emacs buffer, called
28183 This applies both to @value{GDBN} commands and their output, and to the input
28184 and output done by the program you are debugging.
28186 This is useful because it means that you can copy the text of previous
28187 commands and input them again; you can even use parts of the output
28190 All the facilities of Emacs' Shell mode are available for interacting
28191 with your program. In particular, you can send signals the usual
28192 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
28196 @value{GDBN} displays source code through Emacs.
28198 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
28199 source file for that frame and puts an arrow (@samp{=>}) at the
28200 left margin of the current line. Emacs uses a separate buffer for
28201 source display, and splits the screen to show both your @value{GDBN} session
28204 Explicit @value{GDBN} @code{list} or search commands still produce output as
28205 usual, but you probably have no reason to use them from Emacs.
28208 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
28209 a graphical mode, enabled by default, which provides further buffers
28210 that can control the execution and describe the state of your program.
28211 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
28213 If you specify an absolute file name when prompted for the @kbd{M-x
28214 gdb} argument, then Emacs sets your current working directory to where
28215 your program resides. If you only specify the file name, then Emacs
28216 sets your current working directory to the directory associated
28217 with the previous buffer. In this case, @value{GDBN} may find your
28218 program by searching your environment's @code{PATH} variable, but on
28219 some operating systems it might not find the source. So, although the
28220 @value{GDBN} input and output session proceeds normally, the auxiliary
28221 buffer does not display the current source and line of execution.
28223 The initial working directory of @value{GDBN} is printed on the top
28224 line of the GUD buffer and this serves as a default for the commands
28225 that specify files for @value{GDBN} to operate on. @xref{Files,
28226 ,Commands to Specify Files}.
28228 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
28229 need to call @value{GDBN} by a different name (for example, if you
28230 keep several configurations around, with different names) you can
28231 customize the Emacs variable @code{gud-gdb-command-name} to run the
28234 In the GUD buffer, you can use these special Emacs commands in
28235 addition to the standard Shell mode commands:
28239 Describe the features of Emacs' GUD Mode.
28242 Execute to another source line, like the @value{GDBN} @code{step} command; also
28243 update the display window to show the current file and location.
28246 Execute to next source line in this function, skipping all function
28247 calls, like the @value{GDBN} @code{next} command. Then update the display window
28248 to show the current file and location.
28251 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
28252 display window accordingly.
28255 Execute until exit from the selected stack frame, like the @value{GDBN}
28256 @code{finish} command.
28259 Continue execution of your program, like the @value{GDBN} @code{continue}
28263 Go up the number of frames indicated by the numeric argument
28264 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
28265 like the @value{GDBN} @code{up} command.
28268 Go down the number of frames indicated by the numeric argument, like the
28269 @value{GDBN} @code{down} command.
28272 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
28273 tells @value{GDBN} to set a breakpoint on the source line point is on.
28275 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
28276 separate frame which shows a backtrace when the GUD buffer is current.
28277 Move point to any frame in the stack and type @key{RET} to make it
28278 become the current frame and display the associated source in the
28279 source buffer. Alternatively, click @kbd{Mouse-2} to make the
28280 selected frame become the current one. In graphical mode, the
28281 speedbar displays watch expressions.
28283 If you accidentally delete the source-display buffer, an easy way to get
28284 it back is to type the command @code{f} in the @value{GDBN} buffer, to
28285 request a frame display; when you run under Emacs, this recreates
28286 the source buffer if necessary to show you the context of the current
28289 The source files displayed in Emacs are in ordinary Emacs buffers
28290 which are visiting the source files in the usual way. You can edit
28291 the files with these buffers if you wish; but keep in mind that @value{GDBN}
28292 communicates with Emacs in terms of line numbers. If you add or
28293 delete lines from the text, the line numbers that @value{GDBN} knows cease
28294 to correspond properly with the code.
28296 A more detailed description of Emacs' interaction with @value{GDBN} is
28297 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
28301 @chapter The @sc{gdb/mi} Interface
28303 @unnumberedsec Function and Purpose
28305 @cindex @sc{gdb/mi}, its purpose
28306 @sc{gdb/mi} is a line based machine oriented text interface to
28307 @value{GDBN} and is activated by specifying using the
28308 @option{--interpreter} command line option (@pxref{Mode Options}). It
28309 is specifically intended to support the development of systems which
28310 use the debugger as just one small component of a larger system.
28312 This chapter is a specification of the @sc{gdb/mi} interface. It is written
28313 in the form of a reference manual.
28315 Note that @sc{gdb/mi} is still under construction, so some of the
28316 features described below are incomplete and subject to change
28317 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
28319 @unnumberedsec Notation and Terminology
28321 @cindex notational conventions, for @sc{gdb/mi}
28322 This chapter uses the following notation:
28326 @code{|} separates two alternatives.
28329 @code{[ @var{something} ]} indicates that @var{something} is optional:
28330 it may or may not be given.
28333 @code{( @var{group} )*} means that @var{group} inside the parentheses
28334 may repeat zero or more times.
28337 @code{( @var{group} )+} means that @var{group} inside the parentheses
28338 may repeat one or more times.
28341 @code{"@var{string}"} means a literal @var{string}.
28345 @heading Dependencies
28349 * GDB/MI General Design::
28350 * GDB/MI Command Syntax::
28351 * GDB/MI Compatibility with CLI::
28352 * GDB/MI Development and Front Ends::
28353 * GDB/MI Output Records::
28354 * GDB/MI Simple Examples::
28355 * GDB/MI Command Description Format::
28356 * GDB/MI Breakpoint Commands::
28357 * GDB/MI Catchpoint Commands::
28358 * GDB/MI Program Context::
28359 * GDB/MI Thread Commands::
28360 * GDB/MI Ada Tasking Commands::
28361 * GDB/MI Program Execution::
28362 * GDB/MI Stack Manipulation::
28363 * GDB/MI Variable Objects::
28364 * GDB/MI Data Manipulation::
28365 * GDB/MI Tracepoint Commands::
28366 * GDB/MI Symbol Query::
28367 * GDB/MI File Commands::
28369 * GDB/MI Kod Commands::
28370 * GDB/MI Memory Overlay Commands::
28371 * GDB/MI Signal Handling Commands::
28373 * GDB/MI Target Manipulation::
28374 * GDB/MI File Transfer Commands::
28375 * GDB/MI Miscellaneous Commands::
28378 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28379 @node GDB/MI General Design
28380 @section @sc{gdb/mi} General Design
28381 @cindex GDB/MI General Design
28383 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
28384 parts---commands sent to @value{GDBN}, responses to those commands
28385 and notifications. Each command results in exactly one response,
28386 indicating either successful completion of the command, or an error.
28387 For the commands that do not resume the target, the response contains the
28388 requested information. For the commands that resume the target, the
28389 response only indicates whether the target was successfully resumed.
28390 Notifications is the mechanism for reporting changes in the state of the
28391 target, or in @value{GDBN} state, that cannot conveniently be associated with
28392 a command and reported as part of that command response.
28394 The important examples of notifications are:
28398 Exec notifications. These are used to report changes in
28399 target state---when a target is resumed, or stopped. It would not
28400 be feasible to include this information in response of resuming
28401 commands, because one resume commands can result in multiple events in
28402 different threads. Also, quite some time may pass before any event
28403 happens in the target, while a frontend needs to know whether the resuming
28404 command itself was successfully executed.
28407 Console output, and status notifications. Console output
28408 notifications are used to report output of CLI commands, as well as
28409 diagnostics for other commands. Status notifications are used to
28410 report the progress of a long-running operation. Naturally, including
28411 this information in command response would mean no output is produced
28412 until the command is finished, which is undesirable.
28415 General notifications. Commands may have various side effects on
28416 the @value{GDBN} or target state beyond their official purpose. For example,
28417 a command may change the selected thread. Although such changes can
28418 be included in command response, using notification allows for more
28419 orthogonal frontend design.
28423 There's no guarantee that whenever an MI command reports an error,
28424 @value{GDBN} or the target are in any specific state, and especially,
28425 the state is not reverted to the state before the MI command was
28426 processed. Therefore, whenever an MI command results in an error,
28427 we recommend that the frontend refreshes all the information shown in
28428 the user interface.
28432 * Context management::
28433 * Asynchronous and non-stop modes::
28437 @node Context management
28438 @subsection Context management
28440 In most cases when @value{GDBN} accesses the target, this access is
28441 done in context of a specific thread and frame (@pxref{Frames}).
28442 Often, even when accessing global data, the target requires that a thread
28443 be specified. The CLI interface maintains the selected thread and frame,
28444 and supplies them to target on each command. This is convenient,
28445 because a command line user would not want to specify that information
28446 explicitly on each command, and because user interacts with
28447 @value{GDBN} via a single terminal, so no confusion is possible as
28448 to what thread and frame are the current ones.
28450 In the case of MI, the concept of selected thread and frame is less
28451 useful. First, a frontend can easily remember this information
28452 itself. Second, a graphical frontend can have more than one window,
28453 each one used for debugging a different thread, and the frontend might
28454 want to access additional threads for internal purposes. This
28455 increases the risk that by relying on implicitly selected thread, the
28456 frontend may be operating on a wrong one. Therefore, each MI command
28457 should explicitly specify which thread and frame to operate on. To
28458 make it possible, each MI command accepts the @samp{--thread} and
28459 @samp{--frame} options, the value to each is @value{GDBN} identifier
28460 for thread and frame to operate on.
28462 Usually, each top-level window in a frontend allows the user to select
28463 a thread and a frame, and remembers the user selection for further
28464 operations. However, in some cases @value{GDBN} may suggest that the
28465 current thread be changed. For example, when stopping on a breakpoint
28466 it is reasonable to switch to the thread where breakpoint is hit. For
28467 another example, if the user issues the CLI @samp{thread} command via
28468 the frontend, it is desirable to change the frontend's selected thread to the
28469 one specified by user. @value{GDBN} communicates the suggestion to
28470 change current thread using the @samp{=thread-selected} notification.
28471 No such notification is available for the selected frame at the moment.
28473 Note that historically, MI shares the selected thread with CLI, so
28474 frontends used the @code{-thread-select} to execute commands in the
28475 right context. However, getting this to work right is cumbersome. The
28476 simplest way is for frontend to emit @code{-thread-select} command
28477 before every command. This doubles the number of commands that need
28478 to be sent. The alternative approach is to suppress @code{-thread-select}
28479 if the selected thread in @value{GDBN} is supposed to be identical to the
28480 thread the frontend wants to operate on. However, getting this
28481 optimization right can be tricky. In particular, if the frontend
28482 sends several commands to @value{GDBN}, and one of the commands changes the
28483 selected thread, then the behaviour of subsequent commands will
28484 change. So, a frontend should either wait for response from such
28485 problematic commands, or explicitly add @code{-thread-select} for
28486 all subsequent commands. No frontend is known to do this exactly
28487 right, so it is suggested to just always pass the @samp{--thread} and
28488 @samp{--frame} options.
28490 @node Asynchronous and non-stop modes
28491 @subsection Asynchronous command execution and non-stop mode
28493 On some targets, @value{GDBN} is capable of processing MI commands
28494 even while the target is running. This is called @dfn{asynchronous
28495 command execution} (@pxref{Background Execution}). The frontend may
28496 specify a preferrence for asynchronous execution using the
28497 @code{-gdb-set target-async 1} command, which should be emitted before
28498 either running the executable or attaching to the target. After the
28499 frontend has started the executable or attached to the target, it can
28500 find if asynchronous execution is enabled using the
28501 @code{-list-target-features} command.
28503 Even if @value{GDBN} can accept a command while target is running,
28504 many commands that access the target do not work when the target is
28505 running. Therefore, asynchronous command execution is most useful
28506 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
28507 it is possible to examine the state of one thread, while other threads
28510 When a given thread is running, MI commands that try to access the
28511 target in the context of that thread may not work, or may work only on
28512 some targets. In particular, commands that try to operate on thread's
28513 stack will not work, on any target. Commands that read memory, or
28514 modify breakpoints, may work or not work, depending on the target. Note
28515 that even commands that operate on global state, such as @code{print},
28516 @code{set}, and breakpoint commands, still access the target in the
28517 context of a specific thread, so frontend should try to find a
28518 stopped thread and perform the operation on that thread (using the
28519 @samp{--thread} option).
28521 Which commands will work in the context of a running thread is
28522 highly target dependent. However, the two commands
28523 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
28524 to find the state of a thread, will always work.
28526 @node Thread groups
28527 @subsection Thread groups
28528 @value{GDBN} may be used to debug several processes at the same time.
28529 On some platfroms, @value{GDBN} may support debugging of several
28530 hardware systems, each one having several cores with several different
28531 processes running on each core. This section describes the MI
28532 mechanism to support such debugging scenarios.
28534 The key observation is that regardless of the structure of the
28535 target, MI can have a global list of threads, because most commands that
28536 accept the @samp{--thread} option do not need to know what process that
28537 thread belongs to. Therefore, it is not necessary to introduce
28538 neither additional @samp{--process} option, nor an notion of the
28539 current process in the MI interface. The only strictly new feature
28540 that is required is the ability to find how the threads are grouped
28543 To allow the user to discover such grouping, and to support arbitrary
28544 hierarchy of machines/cores/processes, MI introduces the concept of a
28545 @dfn{thread group}. Thread group is a collection of threads and other
28546 thread groups. A thread group always has a string identifier, a type,
28547 and may have additional attributes specific to the type. A new
28548 command, @code{-list-thread-groups}, returns the list of top-level
28549 thread groups, which correspond to processes that @value{GDBN} is
28550 debugging at the moment. By passing an identifier of a thread group
28551 to the @code{-list-thread-groups} command, it is possible to obtain
28552 the members of specific thread group.
28554 To allow the user to easily discover processes, and other objects, he
28555 wishes to debug, a concept of @dfn{available thread group} is
28556 introduced. Available thread group is an thread group that
28557 @value{GDBN} is not debugging, but that can be attached to, using the
28558 @code{-target-attach} command. The list of available top-level thread
28559 groups can be obtained using @samp{-list-thread-groups --available}.
28560 In general, the content of a thread group may be only retrieved only
28561 after attaching to that thread group.
28563 Thread groups are related to inferiors (@pxref{Inferiors and
28564 Programs}). Each inferior corresponds to a thread group of a special
28565 type @samp{process}, and some additional operations are permitted on
28566 such thread groups.
28568 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28569 @node GDB/MI Command Syntax
28570 @section @sc{gdb/mi} Command Syntax
28573 * GDB/MI Input Syntax::
28574 * GDB/MI Output Syntax::
28577 @node GDB/MI Input Syntax
28578 @subsection @sc{gdb/mi} Input Syntax
28580 @cindex input syntax for @sc{gdb/mi}
28581 @cindex @sc{gdb/mi}, input syntax
28583 @item @var{command} @expansion{}
28584 @code{@var{cli-command} | @var{mi-command}}
28586 @item @var{cli-command} @expansion{}
28587 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
28588 @var{cli-command} is any existing @value{GDBN} CLI command.
28590 @item @var{mi-command} @expansion{}
28591 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
28592 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
28594 @item @var{token} @expansion{}
28595 "any sequence of digits"
28597 @item @var{option} @expansion{}
28598 @code{"-" @var{parameter} [ " " @var{parameter} ]}
28600 @item @var{parameter} @expansion{}
28601 @code{@var{non-blank-sequence} | @var{c-string}}
28603 @item @var{operation} @expansion{}
28604 @emph{any of the operations described in this chapter}
28606 @item @var{non-blank-sequence} @expansion{}
28607 @emph{anything, provided it doesn't contain special characters such as
28608 "-", @var{nl}, """ and of course " "}
28610 @item @var{c-string} @expansion{}
28611 @code{""" @var{seven-bit-iso-c-string-content} """}
28613 @item @var{nl} @expansion{}
28622 The CLI commands are still handled by the @sc{mi} interpreter; their
28623 output is described below.
28626 The @code{@var{token}}, when present, is passed back when the command
28630 Some @sc{mi} commands accept optional arguments as part of the parameter
28631 list. Each option is identified by a leading @samp{-} (dash) and may be
28632 followed by an optional argument parameter. Options occur first in the
28633 parameter list and can be delimited from normal parameters using
28634 @samp{--} (this is useful when some parameters begin with a dash).
28641 We want easy access to the existing CLI syntax (for debugging).
28644 We want it to be easy to spot a @sc{mi} operation.
28647 @node GDB/MI Output Syntax
28648 @subsection @sc{gdb/mi} Output Syntax
28650 @cindex output syntax of @sc{gdb/mi}
28651 @cindex @sc{gdb/mi}, output syntax
28652 The output from @sc{gdb/mi} consists of zero or more out-of-band records
28653 followed, optionally, by a single result record. This result record
28654 is for the most recent command. The sequence of output records is
28655 terminated by @samp{(gdb)}.
28657 If an input command was prefixed with a @code{@var{token}} then the
28658 corresponding output for that command will also be prefixed by that same
28662 @item @var{output} @expansion{}
28663 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
28665 @item @var{result-record} @expansion{}
28666 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
28668 @item @var{out-of-band-record} @expansion{}
28669 @code{@var{async-record} | @var{stream-record}}
28671 @item @var{async-record} @expansion{}
28672 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
28674 @item @var{exec-async-output} @expansion{}
28675 @code{[ @var{token} ] "*" @var{async-output}}
28677 @item @var{status-async-output} @expansion{}
28678 @code{[ @var{token} ] "+" @var{async-output}}
28680 @item @var{notify-async-output} @expansion{}
28681 @code{[ @var{token} ] "=" @var{async-output}}
28683 @item @var{async-output} @expansion{}
28684 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
28686 @item @var{result-class} @expansion{}
28687 @code{"done" | "running" | "connected" | "error" | "exit"}
28689 @item @var{async-class} @expansion{}
28690 @code{"stopped" | @var{others}} (where @var{others} will be added
28691 depending on the needs---this is still in development).
28693 @item @var{result} @expansion{}
28694 @code{ @var{variable} "=" @var{value}}
28696 @item @var{variable} @expansion{}
28697 @code{ @var{string} }
28699 @item @var{value} @expansion{}
28700 @code{ @var{const} | @var{tuple} | @var{list} }
28702 @item @var{const} @expansion{}
28703 @code{@var{c-string}}
28705 @item @var{tuple} @expansion{}
28706 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
28708 @item @var{list} @expansion{}
28709 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
28710 @var{result} ( "," @var{result} )* "]" }
28712 @item @var{stream-record} @expansion{}
28713 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
28715 @item @var{console-stream-output} @expansion{}
28716 @code{"~" @var{c-string}}
28718 @item @var{target-stream-output} @expansion{}
28719 @code{"@@" @var{c-string}}
28721 @item @var{log-stream-output} @expansion{}
28722 @code{"&" @var{c-string}}
28724 @item @var{nl} @expansion{}
28727 @item @var{token} @expansion{}
28728 @emph{any sequence of digits}.
28736 All output sequences end in a single line containing a period.
28739 The @code{@var{token}} is from the corresponding request. Note that
28740 for all async output, while the token is allowed by the grammar and
28741 may be output by future versions of @value{GDBN} for select async
28742 output messages, it is generally omitted. Frontends should treat
28743 all async output as reporting general changes in the state of the
28744 target and there should be no need to associate async output to any
28748 @cindex status output in @sc{gdb/mi}
28749 @var{status-async-output} contains on-going status information about the
28750 progress of a slow operation. It can be discarded. All status output is
28751 prefixed by @samp{+}.
28754 @cindex async output in @sc{gdb/mi}
28755 @var{exec-async-output} contains asynchronous state change on the target
28756 (stopped, started, disappeared). All async output is prefixed by
28760 @cindex notify output in @sc{gdb/mi}
28761 @var{notify-async-output} contains supplementary information that the
28762 client should handle (e.g., a new breakpoint information). All notify
28763 output is prefixed by @samp{=}.
28766 @cindex console output in @sc{gdb/mi}
28767 @var{console-stream-output} is output that should be displayed as is in the
28768 console. It is the textual response to a CLI command. All the console
28769 output is prefixed by @samp{~}.
28772 @cindex target output in @sc{gdb/mi}
28773 @var{target-stream-output} is the output produced by the target program.
28774 All the target output is prefixed by @samp{@@}.
28777 @cindex log output in @sc{gdb/mi}
28778 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
28779 instance messages that should be displayed as part of an error log. All
28780 the log output is prefixed by @samp{&}.
28783 @cindex list output in @sc{gdb/mi}
28784 New @sc{gdb/mi} commands should only output @var{lists} containing
28790 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
28791 details about the various output records.
28793 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28794 @node GDB/MI Compatibility with CLI
28795 @section @sc{gdb/mi} Compatibility with CLI
28797 @cindex compatibility, @sc{gdb/mi} and CLI
28798 @cindex @sc{gdb/mi}, compatibility with CLI
28800 For the developers convenience CLI commands can be entered directly,
28801 but there may be some unexpected behaviour. For example, commands
28802 that query the user will behave as if the user replied yes, breakpoint
28803 command lists are not executed and some CLI commands, such as
28804 @code{if}, @code{when} and @code{define}, prompt for further input with
28805 @samp{>}, which is not valid MI output.
28807 This feature may be removed at some stage in the future and it is
28808 recommended that front ends use the @code{-interpreter-exec} command
28809 (@pxref{-interpreter-exec}).
28811 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28812 @node GDB/MI Development and Front Ends
28813 @section @sc{gdb/mi} Development and Front Ends
28814 @cindex @sc{gdb/mi} development
28816 The application which takes the MI output and presents the state of the
28817 program being debugged to the user is called a @dfn{front end}.
28819 Although @sc{gdb/mi} is still incomplete, it is currently being used
28820 by a variety of front ends to @value{GDBN}. This makes it difficult
28821 to introduce new functionality without breaking existing usage. This
28822 section tries to minimize the problems by describing how the protocol
28825 Some changes in MI need not break a carefully designed front end, and
28826 for these the MI version will remain unchanged. The following is a
28827 list of changes that may occur within one level, so front ends should
28828 parse MI output in a way that can handle them:
28832 New MI commands may be added.
28835 New fields may be added to the output of any MI command.
28838 The range of values for fields with specified values, e.g.,
28839 @code{in_scope} (@pxref{-var-update}) may be extended.
28841 @c The format of field's content e.g type prefix, may change so parse it
28842 @c at your own risk. Yes, in general?
28844 @c The order of fields may change? Shouldn't really matter but it might
28845 @c resolve inconsistencies.
28848 If the changes are likely to break front ends, the MI version level
28849 will be increased by one. This will allow the front end to parse the
28850 output according to the MI version. Apart from mi0, new versions of
28851 @value{GDBN} will not support old versions of MI and it will be the
28852 responsibility of the front end to work with the new one.
28854 @c Starting with mi3, add a new command -mi-version that prints the MI
28857 The best way to avoid unexpected changes in MI that might break your front
28858 end is to make your project known to @value{GDBN} developers and
28859 follow development on @email{gdb@@sourceware.org} and
28860 @email{gdb-patches@@sourceware.org}.
28861 @cindex mailing lists
28863 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28864 @node GDB/MI Output Records
28865 @section @sc{gdb/mi} Output Records
28868 * GDB/MI Result Records::
28869 * GDB/MI Stream Records::
28870 * GDB/MI Async Records::
28871 * GDB/MI Breakpoint Information::
28872 * GDB/MI Frame Information::
28873 * GDB/MI Thread Information::
28874 * GDB/MI Ada Exception Information::
28877 @node GDB/MI Result Records
28878 @subsection @sc{gdb/mi} Result Records
28880 @cindex result records in @sc{gdb/mi}
28881 @cindex @sc{gdb/mi}, result records
28882 In addition to a number of out-of-band notifications, the response to a
28883 @sc{gdb/mi} command includes one of the following result indications:
28887 @item "^done" [ "," @var{results} ]
28888 The synchronous operation was successful, @code{@var{results}} are the return
28893 This result record is equivalent to @samp{^done}. Historically, it
28894 was output instead of @samp{^done} if the command has resumed the
28895 target. This behaviour is maintained for backward compatibility, but
28896 all frontends should treat @samp{^done} and @samp{^running}
28897 identically and rely on the @samp{*running} output record to determine
28898 which threads are resumed.
28902 @value{GDBN} has connected to a remote target.
28904 @item "^error" "," @var{c-string}
28906 The operation failed. The @code{@var{c-string}} contains the corresponding
28911 @value{GDBN} has terminated.
28915 @node GDB/MI Stream Records
28916 @subsection @sc{gdb/mi} Stream Records
28918 @cindex @sc{gdb/mi}, stream records
28919 @cindex stream records in @sc{gdb/mi}
28920 @value{GDBN} internally maintains a number of output streams: the console, the
28921 target, and the log. The output intended for each of these streams is
28922 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
28924 Each stream record begins with a unique @dfn{prefix character} which
28925 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
28926 Syntax}). In addition to the prefix, each stream record contains a
28927 @code{@var{string-output}}. This is either raw text (with an implicit new
28928 line) or a quoted C string (which does not contain an implicit newline).
28931 @item "~" @var{string-output}
28932 The console output stream contains text that should be displayed in the
28933 CLI console window. It contains the textual responses to CLI commands.
28935 @item "@@" @var{string-output}
28936 The target output stream contains any textual output from the running
28937 target. This is only present when GDB's event loop is truly
28938 asynchronous, which is currently only the case for remote targets.
28940 @item "&" @var{string-output}
28941 The log stream contains debugging messages being produced by @value{GDBN}'s
28945 @node GDB/MI Async Records
28946 @subsection @sc{gdb/mi} Async Records
28948 @cindex async records in @sc{gdb/mi}
28949 @cindex @sc{gdb/mi}, async records
28950 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
28951 additional changes that have occurred. Those changes can either be a
28952 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28953 target activity (e.g., target stopped).
28955 The following is the list of possible async records:
28959 @item *running,thread-id="@var{thread}"
28960 The target is now running. The @var{thread} field tells which
28961 specific thread is now running, and can be @samp{all} if all threads
28962 are running. The frontend should assume that no interaction with a
28963 running thread is possible after this notification is produced.
28964 The frontend should not assume that this notification is output
28965 only once for any command. @value{GDBN} may emit this notification
28966 several times, either for different threads, because it cannot resume
28967 all threads together, or even for a single thread, if the thread must
28968 be stepped though some code before letting it run freely.
28970 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28971 The target has stopped. The @var{reason} field can have one of the
28975 @item breakpoint-hit
28976 A breakpoint was reached.
28977 @item watchpoint-trigger
28978 A watchpoint was triggered.
28979 @item read-watchpoint-trigger
28980 A read watchpoint was triggered.
28981 @item access-watchpoint-trigger
28982 An access watchpoint was triggered.
28983 @item function-finished
28984 An -exec-finish or similar CLI command was accomplished.
28985 @item location-reached
28986 An -exec-until or similar CLI command was accomplished.
28987 @item watchpoint-scope
28988 A watchpoint has gone out of scope.
28989 @item end-stepping-range
28990 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28991 similar CLI command was accomplished.
28992 @item exited-signalled
28993 The inferior exited because of a signal.
28995 The inferior exited.
28996 @item exited-normally
28997 The inferior exited normally.
28998 @item signal-received
28999 A signal was received by the inferior.
29001 The inferior has stopped due to a library being loaded or unloaded.
29002 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
29003 set or when a @code{catch load} or @code{catch unload} catchpoint is
29004 in use (@pxref{Set Catchpoints}).
29006 The inferior has forked. This is reported when @code{catch fork}
29007 (@pxref{Set Catchpoints}) has been used.
29009 The inferior has vforked. This is reported in when @code{catch vfork}
29010 (@pxref{Set Catchpoints}) has been used.
29011 @item syscall-entry
29012 The inferior entered a system call. This is reported when @code{catch
29013 syscall} (@pxref{Set Catchpoints}) has been used.
29014 @item syscall-entry
29015 The inferior returned from a system call. This is reported when
29016 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
29018 The inferior called @code{exec}. This is reported when @code{catch exec}
29019 (@pxref{Set Catchpoints}) has been used.
29022 The @var{id} field identifies the thread that directly caused the stop
29023 -- for example by hitting a breakpoint. Depending on whether all-stop
29024 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
29025 stop all threads, or only the thread that directly triggered the stop.
29026 If all threads are stopped, the @var{stopped} field will have the
29027 value of @code{"all"}. Otherwise, the value of the @var{stopped}
29028 field will be a list of thread identifiers. Presently, this list will
29029 always include a single thread, but frontend should be prepared to see
29030 several threads in the list. The @var{core} field reports the
29031 processor core on which the stop event has happened. This field may be absent
29032 if such information is not available.
29034 @item =thread-group-added,id="@var{id}"
29035 @itemx =thread-group-removed,id="@var{id}"
29036 A thread group was either added or removed. The @var{id} field
29037 contains the @value{GDBN} identifier of the thread group. When a thread
29038 group is added, it generally might not be associated with a running
29039 process. When a thread group is removed, its id becomes invalid and
29040 cannot be used in any way.
29042 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
29043 A thread group became associated with a running program,
29044 either because the program was just started or the thread group
29045 was attached to a program. The @var{id} field contains the
29046 @value{GDBN} identifier of the thread group. The @var{pid} field
29047 contains process identifier, specific to the operating system.
29049 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
29050 A thread group is no longer associated with a running program,
29051 either because the program has exited, or because it was detached
29052 from. The @var{id} field contains the @value{GDBN} identifier of the
29053 thread group. @var{code} is the exit code of the inferior; it exists
29054 only when the inferior exited with some code.
29056 @item =thread-created,id="@var{id}",group-id="@var{gid}"
29057 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
29058 A thread either was created, or has exited. The @var{id} field
29059 contains the @value{GDBN} identifier of the thread. The @var{gid}
29060 field identifies the thread group this thread belongs to.
29062 @item =thread-selected,id="@var{id}"
29063 Informs that the selected thread was changed as result of the last
29064 command. This notification is not emitted as result of @code{-thread-select}
29065 command but is emitted whenever an MI command that is not documented
29066 to change the selected thread actually changes it. In particular,
29067 invoking, directly or indirectly (via user-defined command), the CLI
29068 @code{thread} command, will generate this notification.
29070 We suggest that in response to this notification, front ends
29071 highlight the selected thread and cause subsequent commands to apply to
29074 @item =library-loaded,...
29075 Reports that a new library file was loaded by the program. This
29076 notification has 4 fields---@var{id}, @var{target-name},
29077 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
29078 opaque identifier of the library. For remote debugging case,
29079 @var{target-name} and @var{host-name} fields give the name of the
29080 library file on the target, and on the host respectively. For native
29081 debugging, both those fields have the same value. The
29082 @var{symbols-loaded} field is emitted only for backward compatibility
29083 and should not be relied on to convey any useful information. The
29084 @var{thread-group} field, if present, specifies the id of the thread
29085 group in whose context the library was loaded. If the field is
29086 absent, it means the library was loaded in the context of all present
29089 @item =library-unloaded,...
29090 Reports that a library was unloaded by the program. This notification
29091 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
29092 the same meaning as for the @code{=library-loaded} notification.
29093 The @var{thread-group} field, if present, specifies the id of the
29094 thread group in whose context the library was unloaded. If the field is
29095 absent, it means the library was unloaded in the context of all present
29098 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
29099 @itemx =traceframe-changed,end
29100 Reports that the trace frame was changed and its new number is
29101 @var{tfnum}. The number of the tracepoint associated with this trace
29102 frame is @var{tpnum}.
29104 @item =tsv-created,name=@var{name},initial=@var{initial}
29105 Reports that the new trace state variable @var{name} is created with
29106 initial value @var{initial}.
29108 @item =tsv-deleted,name=@var{name}
29109 @itemx =tsv-deleted
29110 Reports that the trace state variable @var{name} is deleted or all
29111 trace state variables are deleted.
29113 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
29114 Reports that the trace state variable @var{name} is modified with
29115 the initial value @var{initial}. The current value @var{current} of
29116 trace state variable is optional and is reported if the current
29117 value of trace state variable is known.
29119 @item =breakpoint-created,bkpt=@{...@}
29120 @itemx =breakpoint-modified,bkpt=@{...@}
29121 @itemx =breakpoint-deleted,id=@var{number}
29122 Reports that a breakpoint was created, modified, or deleted,
29123 respectively. Only user-visible breakpoints are reported to the MI
29126 The @var{bkpt} argument is of the same form as returned by the various
29127 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
29128 @var{number} is the ordinal number of the breakpoint.
29130 Note that if a breakpoint is emitted in the result record of a
29131 command, then it will not also be emitted in an async record.
29133 @item =record-started,thread-group="@var{id}"
29134 @itemx =record-stopped,thread-group="@var{id}"
29135 Execution log recording was either started or stopped on an
29136 inferior. The @var{id} is the @value{GDBN} identifier of the thread
29137 group corresponding to the affected inferior.
29139 @item =cmd-param-changed,param=@var{param},value=@var{value}
29140 Reports that a parameter of the command @code{set @var{param}} is
29141 changed to @var{value}. In the multi-word @code{set} command,
29142 the @var{param} is the whole parameter list to @code{set} command.
29143 For example, In command @code{set check type on}, @var{param}
29144 is @code{check type} and @var{value} is @code{on}.
29146 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
29147 Reports that bytes from @var{addr} to @var{data} + @var{len} were
29148 written in an inferior. The @var{id} is the identifier of the
29149 thread group corresponding to the affected inferior. The optional
29150 @code{type="code"} part is reported if the memory written to holds
29154 @node GDB/MI Breakpoint Information
29155 @subsection @sc{gdb/mi} Breakpoint Information
29157 When @value{GDBN} reports information about a breakpoint, a
29158 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
29163 The breakpoint number. For a breakpoint that represents one location
29164 of a multi-location breakpoint, this will be a dotted pair, like
29168 The type of the breakpoint. For ordinary breakpoints this will be
29169 @samp{breakpoint}, but many values are possible.
29172 If the type of the breakpoint is @samp{catchpoint}, then this
29173 indicates the exact type of catchpoint.
29176 This is the breakpoint disposition---either @samp{del}, meaning that
29177 the breakpoint will be deleted at the next stop, or @samp{keep},
29178 meaning that the breakpoint will not be deleted.
29181 This indicates whether the breakpoint is enabled, in which case the
29182 value is @samp{y}, or disabled, in which case the value is @samp{n}.
29183 Note that this is not the same as the field @code{enable}.
29186 The address of the breakpoint. This may be a hexidecimal number,
29187 giving the address; or the string @samp{<PENDING>}, for a pending
29188 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
29189 multiple locations. This field will not be present if no address can
29190 be determined. For example, a watchpoint does not have an address.
29193 If known, the function in which the breakpoint appears.
29194 If not known, this field is not present.
29197 The name of the source file which contains this function, if known.
29198 If not known, this field is not present.
29201 The full file name of the source file which contains this function, if
29202 known. If not known, this field is not present.
29205 The line number at which this breakpoint appears, if known.
29206 If not known, this field is not present.
29209 If the source file is not known, this field may be provided. If
29210 provided, this holds the address of the breakpoint, possibly followed
29214 If this breakpoint is pending, this field is present and holds the
29215 text used to set the breakpoint, as entered by the user.
29218 Where this breakpoint's condition is evaluated, either @samp{host} or
29222 If this is a thread-specific breakpoint, then this identifies the
29223 thread in which the breakpoint can trigger.
29226 If this breakpoint is restricted to a particular Ada task, then this
29227 field will hold the task identifier.
29230 If the breakpoint is conditional, this is the condition expression.
29233 The ignore count of the breakpoint.
29236 The enable count of the breakpoint.
29238 @item traceframe-usage
29241 @item static-tracepoint-marker-string-id
29242 For a static tracepoint, the name of the static tracepoint marker.
29245 For a masked watchpoint, this is the mask.
29248 A tracepoint's pass count.
29250 @item original-location
29251 The location of the breakpoint as originally specified by the user.
29252 This field is optional.
29255 The number of times the breakpoint has been hit.
29258 This field is only given for tracepoints. This is either @samp{y},
29259 meaning that the tracepoint is installed, or @samp{n}, meaning that it
29263 Some extra data, the exact contents of which are type-dependent.
29267 For example, here is what the output of @code{-break-insert}
29268 (@pxref{GDB/MI Breakpoint Commands}) might be:
29271 -> -break-insert main
29272 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29273 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29274 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29279 @node GDB/MI Frame Information
29280 @subsection @sc{gdb/mi} Frame Information
29282 Response from many MI commands includes an information about stack
29283 frame. This information is a tuple that may have the following
29288 The level of the stack frame. The innermost frame has the level of
29289 zero. This field is always present.
29292 The name of the function corresponding to the frame. This field may
29293 be absent if @value{GDBN} is unable to determine the function name.
29296 The code address for the frame. This field is always present.
29299 The name of the source files that correspond to the frame's code
29300 address. This field may be absent.
29303 The source line corresponding to the frames' code address. This field
29307 The name of the binary file (either executable or shared library) the
29308 corresponds to the frame's code address. This field may be absent.
29312 @node GDB/MI Thread Information
29313 @subsection @sc{gdb/mi} Thread Information
29315 Whenever @value{GDBN} has to report an information about a thread, it
29316 uses a tuple with the following fields:
29320 The numeric id assigned to the thread by @value{GDBN}. This field is
29324 Target-specific string identifying the thread. This field is always present.
29327 Additional information about the thread provided by the target.
29328 It is supposed to be human-readable and not interpreted by the
29329 frontend. This field is optional.
29332 Either @samp{stopped} or @samp{running}, depending on whether the
29333 thread is presently running. This field is always present.
29336 The value of this field is an integer number of the processor core the
29337 thread was last seen on. This field is optional.
29340 @node GDB/MI Ada Exception Information
29341 @subsection @sc{gdb/mi} Ada Exception Information
29343 Whenever a @code{*stopped} record is emitted because the program
29344 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
29345 @value{GDBN} provides the name of the exception that was raised via
29346 the @code{exception-name} field.
29348 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29349 @node GDB/MI Simple Examples
29350 @section Simple Examples of @sc{gdb/mi} Interaction
29351 @cindex @sc{gdb/mi}, simple examples
29353 This subsection presents several simple examples of interaction using
29354 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
29355 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
29356 the output received from @sc{gdb/mi}.
29358 Note the line breaks shown in the examples are here only for
29359 readability, they don't appear in the real output.
29361 @subheading Setting a Breakpoint
29363 Setting a breakpoint generates synchronous output which contains detailed
29364 information of the breakpoint.
29367 -> -break-insert main
29368 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29369 enabled="y",addr="0x08048564",func="main",file="myprog.c",
29370 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
29375 @subheading Program Execution
29377 Program execution generates asynchronous records and MI gives the
29378 reason that execution stopped.
29384 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
29385 frame=@{addr="0x08048564",func="main",
29386 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
29387 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
29392 <- *stopped,reason="exited-normally"
29396 @subheading Quitting @value{GDBN}
29398 Quitting @value{GDBN} just prints the result class @samp{^exit}.
29406 Please note that @samp{^exit} is printed immediately, but it might
29407 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
29408 performs necessary cleanups, including killing programs being debugged
29409 or disconnecting from debug hardware, so the frontend should wait till
29410 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
29411 fails to exit in reasonable time.
29413 @subheading A Bad Command
29415 Here's what happens if you pass a non-existent command:
29419 <- ^error,msg="Undefined MI command: rubbish"
29424 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29425 @node GDB/MI Command Description Format
29426 @section @sc{gdb/mi} Command Description Format
29428 The remaining sections describe blocks of commands. Each block of
29429 commands is laid out in a fashion similar to this section.
29431 @subheading Motivation
29433 The motivation for this collection of commands.
29435 @subheading Introduction
29437 A brief introduction to this collection of commands as a whole.
29439 @subheading Commands
29441 For each command in the block, the following is described:
29443 @subsubheading Synopsis
29446 -command @var{args}@dots{}
29449 @subsubheading Result
29451 @subsubheading @value{GDBN} Command
29453 The corresponding @value{GDBN} CLI command(s), if any.
29455 @subsubheading Example
29457 Example(s) formatted for readability. Some of the described commands have
29458 not been implemented yet and these are labeled N.A.@: (not available).
29461 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29462 @node GDB/MI Breakpoint Commands
29463 @section @sc{gdb/mi} Breakpoint Commands
29465 @cindex breakpoint commands for @sc{gdb/mi}
29466 @cindex @sc{gdb/mi}, breakpoint commands
29467 This section documents @sc{gdb/mi} commands for manipulating
29470 @subheading The @code{-break-after} Command
29471 @findex -break-after
29473 @subsubheading Synopsis
29476 -break-after @var{number} @var{count}
29479 The breakpoint number @var{number} is not in effect until it has been
29480 hit @var{count} times. To see how this is reflected in the output of
29481 the @samp{-break-list} command, see the description of the
29482 @samp{-break-list} command below.
29484 @subsubheading @value{GDBN} Command
29486 The corresponding @value{GDBN} command is @samp{ignore}.
29488 @subsubheading Example
29493 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29494 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29495 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29503 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29504 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29505 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29506 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29507 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29508 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29509 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29510 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29511 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29512 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
29517 @subheading The @code{-break-catch} Command
29518 @findex -break-catch
29521 @subheading The @code{-break-commands} Command
29522 @findex -break-commands
29524 @subsubheading Synopsis
29527 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
29530 Specifies the CLI commands that should be executed when breakpoint
29531 @var{number} is hit. The parameters @var{command1} to @var{commandN}
29532 are the commands. If no command is specified, any previously-set
29533 commands are cleared. @xref{Break Commands}. Typical use of this
29534 functionality is tracing a program, that is, printing of values of
29535 some variables whenever breakpoint is hit and then continuing.
29537 @subsubheading @value{GDBN} Command
29539 The corresponding @value{GDBN} command is @samp{commands}.
29541 @subsubheading Example
29546 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
29547 enabled="y",addr="0x000100d0",func="main",file="hello.c",
29548 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
29551 -break-commands 1 "print v" "continue"
29556 @subheading The @code{-break-condition} Command
29557 @findex -break-condition
29559 @subsubheading Synopsis
29562 -break-condition @var{number} @var{expr}
29565 Breakpoint @var{number} will stop the program only if the condition in
29566 @var{expr} is true. The condition becomes part of the
29567 @samp{-break-list} output (see the description of the @samp{-break-list}
29570 @subsubheading @value{GDBN} Command
29572 The corresponding @value{GDBN} command is @samp{condition}.
29574 @subsubheading Example
29578 -break-condition 1 1
29582 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29583 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29584 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29585 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29586 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29587 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29588 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29589 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29590 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29591 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
29595 @subheading The @code{-break-delete} Command
29596 @findex -break-delete
29598 @subsubheading Synopsis
29601 -break-delete ( @var{breakpoint} )+
29604 Delete the breakpoint(s) whose number(s) are specified in the argument
29605 list. This is obviously reflected in the breakpoint list.
29607 @subsubheading @value{GDBN} Command
29609 The corresponding @value{GDBN} command is @samp{delete}.
29611 @subsubheading Example
29619 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29620 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29621 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29622 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29623 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29624 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29625 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29630 @subheading The @code{-break-disable} Command
29631 @findex -break-disable
29633 @subsubheading Synopsis
29636 -break-disable ( @var{breakpoint} )+
29639 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
29640 break list is now set to @samp{n} for the named @var{breakpoint}(s).
29642 @subsubheading @value{GDBN} Command
29644 The corresponding @value{GDBN} command is @samp{disable}.
29646 @subsubheading Example
29654 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29655 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29656 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29657 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29658 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29659 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29660 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29661 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
29662 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29663 line="5",thread-groups=["i1"],times="0"@}]@}
29667 @subheading The @code{-break-enable} Command
29668 @findex -break-enable
29670 @subsubheading Synopsis
29673 -break-enable ( @var{breakpoint} )+
29676 Enable (previously disabled) @var{breakpoint}(s).
29678 @subsubheading @value{GDBN} Command
29680 The corresponding @value{GDBN} command is @samp{enable}.
29682 @subsubheading Example
29690 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29691 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29692 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29693 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29694 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29695 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29696 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29697 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29698 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
29699 line="5",thread-groups=["i1"],times="0"@}]@}
29703 @subheading The @code{-break-info} Command
29704 @findex -break-info
29706 @subsubheading Synopsis
29709 -break-info @var{breakpoint}
29713 Get information about a single breakpoint.
29715 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
29716 Information}, for details on the format of each breakpoint in the
29719 @subsubheading @value{GDBN} Command
29721 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
29723 @subsubheading Example
29726 @subheading The @code{-break-insert} Command
29727 @findex -break-insert
29729 @subsubheading Synopsis
29732 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
29733 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29734 [ -p @var{thread-id} ] [ @var{location} ]
29738 If specified, @var{location}, can be one of:
29745 @item filename:linenum
29746 @item filename:function
29750 The possible optional parameters of this command are:
29754 Insert a temporary breakpoint.
29756 Insert a hardware breakpoint.
29758 If @var{location} cannot be parsed (for example if it
29759 refers to unknown files or functions), create a pending
29760 breakpoint. Without this flag, @value{GDBN} will report
29761 an error, and won't create a breakpoint, if @var{location}
29764 Create a disabled breakpoint.
29766 Create a tracepoint. @xref{Tracepoints}. When this parameter
29767 is used together with @samp{-h}, a fast tracepoint is created.
29768 @item -c @var{condition}
29769 Make the breakpoint conditional on @var{condition}.
29770 @item -i @var{ignore-count}
29771 Initialize the @var{ignore-count}.
29772 @item -p @var{thread-id}
29773 Restrict the breakpoint to the specified @var{thread-id}.
29776 @subsubheading Result
29778 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29779 resulting breakpoint.
29781 Note: this format is open to change.
29782 @c An out-of-band breakpoint instead of part of the result?
29784 @subsubheading @value{GDBN} Command
29786 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
29787 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
29789 @subsubheading Example
29794 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
29795 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
29798 -break-insert -t foo
29799 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
29800 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
29804 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29805 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29806 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29807 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29808 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29809 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29810 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29811 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29812 addr="0x0001072c", func="main",file="recursive2.c",
29813 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
29815 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
29816 addr="0x00010774",func="foo",file="recursive2.c",
29817 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29820 @c -break-insert -r foo.*
29821 @c ~int foo(int, int);
29822 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
29823 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
29828 @subheading The @code{-dprintf-insert} Command
29829 @findex -dprintf-insert
29831 @subsubheading Synopsis
29834 -dprintf-insert [ -t ] [ -f ] [ -d ]
29835 [ -c @var{condition} ] [ -i @var{ignore-count} ]
29836 [ -p @var{thread-id} ] [ @var{location} ] [ @var{format} ]
29841 If specified, @var{location}, can be one of:
29844 @item @var{function}
29847 @c @item @var{linenum}
29848 @item @var{filename}:@var{linenum}
29849 @item @var{filename}:function
29850 @item *@var{address}
29853 The possible optional parameters of this command are:
29857 Insert a temporary breakpoint.
29859 If @var{location} cannot be parsed (for example, if it
29860 refers to unknown files or functions), create a pending
29861 breakpoint. Without this flag, @value{GDBN} will report
29862 an error, and won't create a breakpoint, if @var{location}
29865 Create a disabled breakpoint.
29866 @item -c @var{condition}
29867 Make the breakpoint conditional on @var{condition}.
29868 @item -i @var{ignore-count}
29869 Set the ignore count of the breakpoint (@pxref{Conditions, ignore count})
29870 to @var{ignore-count}.
29871 @item -p @var{thread-id}
29872 Restrict the breakpoint to the specified @var{thread-id}.
29875 @subsubheading Result
29877 @xref{GDB/MI Breakpoint Information}, for details on the format of the
29878 resulting breakpoint.
29880 @c An out-of-band breakpoint instead of part of the result?
29882 @subsubheading @value{GDBN} Command
29884 The corresponding @value{GDBN} command is @samp{dprintf}.
29886 @subsubheading Example
29890 4-dprintf-insert foo "At foo entry\n"
29891 4^done,bkpt=@{number="1",type="dprintf",disp="keep",enabled="y",
29892 addr="0x000000000040061b",func="foo",file="mi-dprintf.c",
29893 fullname="mi-dprintf.c",line="25",thread-groups=["i1"],
29894 times="0",script=@{"printf \"At foo entry\\n\"","continue"@},
29895 original-location="foo"@}
29897 5-dprintf-insert 26 "arg=%d, g=%d\n" arg g
29898 5^done,bkpt=@{number="2",type="dprintf",disp="keep",enabled="y",
29899 addr="0x000000000040062a",func="foo",file="mi-dprintf.c",
29900 fullname="mi-dprintf.c",line="26",thread-groups=["i1"],
29901 times="0",script=@{"printf \"arg=%d, g=%d\\n\", arg, g","continue"@},
29902 original-location="mi-dprintf.c:26"@}
29906 @subheading The @code{-break-list} Command
29907 @findex -break-list
29909 @subsubheading Synopsis
29915 Displays the list of inserted breakpoints, showing the following fields:
29919 number of the breakpoint
29921 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
29923 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
29926 is the breakpoint enabled or no: @samp{y} or @samp{n}
29928 memory location at which the breakpoint is set
29930 logical location of the breakpoint, expressed by function name, file
29932 @item Thread-groups
29933 list of thread groups to which this breakpoint applies
29935 number of times the breakpoint has been hit
29938 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
29939 @code{body} field is an empty list.
29941 @subsubheading @value{GDBN} Command
29943 The corresponding @value{GDBN} command is @samp{info break}.
29945 @subsubheading Example
29950 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29951 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29952 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29953 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29954 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29955 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29956 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29957 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29958 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
29960 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
29961 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
29962 line="13",thread-groups=["i1"],times="0"@}]@}
29966 Here's an example of the result when there are no breakpoints:
29971 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
29972 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29973 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29974 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29975 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29976 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29977 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29982 @subheading The @code{-break-passcount} Command
29983 @findex -break-passcount
29985 @subsubheading Synopsis
29988 -break-passcount @var{tracepoint-number} @var{passcount}
29991 Set the passcount for tracepoint @var{tracepoint-number} to
29992 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
29993 is not a tracepoint, error is emitted. This corresponds to CLI
29994 command @samp{passcount}.
29996 @subheading The @code{-break-watch} Command
29997 @findex -break-watch
29999 @subsubheading Synopsis
30002 -break-watch [ -a | -r ]
30005 Create a watchpoint. With the @samp{-a} option it will create an
30006 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
30007 read from or on a write to the memory location. With the @samp{-r}
30008 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
30009 trigger only when the memory location is accessed for reading. Without
30010 either of the options, the watchpoint created is a regular watchpoint,
30011 i.e., it will trigger when the memory location is accessed for writing.
30012 @xref{Set Watchpoints, , Setting Watchpoints}.
30014 Note that @samp{-break-list} will report a single list of watchpoints and
30015 breakpoints inserted.
30017 @subsubheading @value{GDBN} Command
30019 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
30022 @subsubheading Example
30024 Setting a watchpoint on a variable in the @code{main} function:
30029 ^done,wpt=@{number="2",exp="x"@}
30034 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
30035 value=@{old="-268439212",new="55"@},
30036 frame=@{func="main",args=[],file="recursive2.c",
30037 fullname="/home/foo/bar/recursive2.c",line="5"@}
30041 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
30042 the program execution twice: first for the variable changing value, then
30043 for the watchpoint going out of scope.
30048 ^done,wpt=@{number="5",exp="C"@}
30053 *stopped,reason="watchpoint-trigger",
30054 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
30055 frame=@{func="callee4",args=[],
30056 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30057 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30062 *stopped,reason="watchpoint-scope",wpnum="5",
30063 frame=@{func="callee3",args=[@{name="strarg",
30064 value="0x11940 \"A string argument.\""@}],
30065 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30066 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30070 Listing breakpoints and watchpoints, at different points in the program
30071 execution. Note that once the watchpoint goes out of scope, it is
30077 ^done,wpt=@{number="2",exp="C"@}
30080 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30081 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30082 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30083 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30084 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30085 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30086 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30087 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30088 addr="0x00010734",func="callee4",
30089 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30090 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
30092 bkpt=@{number="2",type="watchpoint",disp="keep",
30093 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
30098 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
30099 value=@{old="-276895068",new="3"@},
30100 frame=@{func="callee4",args=[],
30101 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30102 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
30105 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
30106 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30107 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30108 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30109 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30110 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30111 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30112 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30113 addr="0x00010734",func="callee4",
30114 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30115 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
30117 bkpt=@{number="2",type="watchpoint",disp="keep",
30118 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
30122 ^done,reason="watchpoint-scope",wpnum="2",
30123 frame=@{func="callee3",args=[@{name="strarg",
30124 value="0x11940 \"A string argument.\""@}],
30125 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30126 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30129 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
30130 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
30131 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
30132 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
30133 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
30134 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
30135 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
30136 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
30137 addr="0x00010734",func="callee4",
30138 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30139 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
30140 thread-groups=["i1"],times="1"@}]@}
30145 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30146 @node GDB/MI Catchpoint Commands
30147 @section @sc{gdb/mi} Catchpoint Commands
30149 This section documents @sc{gdb/mi} commands for manipulating
30152 @subheading The @code{-catch-load} Command
30153 @findex -catch-load
30155 @subsubheading Synopsis
30158 -catch-load [ -t ] [ -d ] @var{regexp}
30161 Add a catchpoint for library load events. If the @samp{-t} option is used,
30162 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30163 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
30164 in a disabled state. The @samp{regexp} argument is a regular
30165 expression used to match the name of the loaded library.
30168 @subsubheading @value{GDBN} Command
30170 The corresponding @value{GDBN} command is @samp{catch load}.
30172 @subsubheading Example
30175 -catch-load -t foo.so
30176 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
30177 what="load of library matching foo.so",catch-type="load",times="0"@}
30182 @subheading The @code{-catch-unload} Command
30183 @findex -catch-unload
30185 @subsubheading Synopsis
30188 -catch-unload [ -t ] [ -d ] @var{regexp}
30191 Add a catchpoint for library unload events. If the @samp{-t} option is
30192 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
30193 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
30194 created in a disabled state. The @samp{regexp} argument is a regular
30195 expression used to match the name of the unloaded library.
30197 @subsubheading @value{GDBN} Command
30199 The corresponding @value{GDBN} command is @samp{catch unload}.
30201 @subsubheading Example
30204 -catch-unload -d bar.so
30205 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
30206 what="load of library matching bar.so",catch-type="unload",times="0"@}
30211 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30212 @node GDB/MI Program Context
30213 @section @sc{gdb/mi} Program Context
30215 @subheading The @code{-exec-arguments} Command
30216 @findex -exec-arguments
30219 @subsubheading Synopsis
30222 -exec-arguments @var{args}
30225 Set the inferior program arguments, to be used in the next
30228 @subsubheading @value{GDBN} Command
30230 The corresponding @value{GDBN} command is @samp{set args}.
30232 @subsubheading Example
30236 -exec-arguments -v word
30243 @subheading The @code{-exec-show-arguments} Command
30244 @findex -exec-show-arguments
30246 @subsubheading Synopsis
30249 -exec-show-arguments
30252 Print the arguments of the program.
30254 @subsubheading @value{GDBN} Command
30256 The corresponding @value{GDBN} command is @samp{show args}.
30258 @subsubheading Example
30263 @subheading The @code{-environment-cd} Command
30264 @findex -environment-cd
30266 @subsubheading Synopsis
30269 -environment-cd @var{pathdir}
30272 Set @value{GDBN}'s working directory.
30274 @subsubheading @value{GDBN} Command
30276 The corresponding @value{GDBN} command is @samp{cd}.
30278 @subsubheading Example
30282 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30288 @subheading The @code{-environment-directory} Command
30289 @findex -environment-directory
30291 @subsubheading Synopsis
30294 -environment-directory [ -r ] [ @var{pathdir} ]+
30297 Add directories @var{pathdir} to beginning of search path for source files.
30298 If the @samp{-r} option is used, the search path is reset to the default
30299 search path. If directories @var{pathdir} are supplied in addition to the
30300 @samp{-r} option, the search path is first reset and then addition
30302 Multiple directories may be specified, separated by blanks. Specifying
30303 multiple directories in a single command
30304 results in the directories added to the beginning of the
30305 search path in the same order they were presented in the command.
30306 If blanks are needed as
30307 part of a directory name, double-quotes should be used around
30308 the name. In the command output, the path will show up separated
30309 by the system directory-separator character. The directory-separator
30310 character must not be used
30311 in any directory name.
30312 If no directories are specified, the current search path is displayed.
30314 @subsubheading @value{GDBN} Command
30316 The corresponding @value{GDBN} command is @samp{dir}.
30318 @subsubheading Example
30322 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
30323 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30325 -environment-directory ""
30326 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
30328 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
30329 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
30331 -environment-directory -r
30332 ^done,source-path="$cdir:$cwd"
30337 @subheading The @code{-environment-path} Command
30338 @findex -environment-path
30340 @subsubheading Synopsis
30343 -environment-path [ -r ] [ @var{pathdir} ]+
30346 Add directories @var{pathdir} to beginning of search path for object files.
30347 If the @samp{-r} option is used, the search path is reset to the original
30348 search path that existed at gdb start-up. If directories @var{pathdir} are
30349 supplied in addition to the
30350 @samp{-r} option, the search path is first reset and then addition
30352 Multiple directories may be specified, separated by blanks. Specifying
30353 multiple directories in a single command
30354 results in the directories added to the beginning of the
30355 search path in the same order they were presented in the command.
30356 If blanks are needed as
30357 part of a directory name, double-quotes should be used around
30358 the name. In the command output, the path will show up separated
30359 by the system directory-separator character. The directory-separator
30360 character must not be used
30361 in any directory name.
30362 If no directories are specified, the current path is displayed.
30365 @subsubheading @value{GDBN} Command
30367 The corresponding @value{GDBN} command is @samp{path}.
30369 @subsubheading Example
30374 ^done,path="/usr/bin"
30376 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
30377 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
30379 -environment-path -r /usr/local/bin
30380 ^done,path="/usr/local/bin:/usr/bin"
30385 @subheading The @code{-environment-pwd} Command
30386 @findex -environment-pwd
30388 @subsubheading Synopsis
30394 Show the current working directory.
30396 @subsubheading @value{GDBN} Command
30398 The corresponding @value{GDBN} command is @samp{pwd}.
30400 @subsubheading Example
30405 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
30409 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30410 @node GDB/MI Thread Commands
30411 @section @sc{gdb/mi} Thread Commands
30414 @subheading The @code{-thread-info} Command
30415 @findex -thread-info
30417 @subsubheading Synopsis
30420 -thread-info [ @var{thread-id} ]
30423 Reports information about either a specific thread, if
30424 the @var{thread-id} parameter is present, or about all
30425 threads. When printing information about all threads,
30426 also reports the current thread.
30428 @subsubheading @value{GDBN} Command
30430 The @samp{info thread} command prints the same information
30433 @subsubheading Result
30435 The result is a list of threads. The following attributes are
30436 defined for a given thread:
30440 This field exists only for the current thread. It has the value @samp{*}.
30443 The identifier that @value{GDBN} uses to refer to the thread.
30446 The identifier that the target uses to refer to the thread.
30449 Extra information about the thread, in a target-specific format. This
30453 The name of the thread. If the user specified a name using the
30454 @code{thread name} command, then this name is given. Otherwise, if
30455 @value{GDBN} can extract the thread name from the target, then that
30456 name is given. If @value{GDBN} cannot find the thread name, then this
30460 The stack frame currently executing in the thread.
30463 The thread's state. The @samp{state} field may have the following
30468 The thread is stopped. Frame information is available for stopped
30472 The thread is running. There's no frame information for running
30478 If @value{GDBN} can find the CPU core on which this thread is running,
30479 then this field is the core identifier. This field is optional.
30483 @subsubheading Example
30488 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
30489 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
30490 args=[]@},state="running"@},
30491 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
30492 frame=@{level="0",addr="0x0804891f",func="foo",
30493 args=[@{name="i",value="10"@}],
30494 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
30495 state="running"@}],
30496 current-thread-id="1"
30500 @subheading The @code{-thread-list-ids} Command
30501 @findex -thread-list-ids
30503 @subsubheading Synopsis
30509 Produces a list of the currently known @value{GDBN} thread ids. At the
30510 end of the list it also prints the total number of such threads.
30512 This command is retained for historical reasons, the
30513 @code{-thread-info} command should be used instead.
30515 @subsubheading @value{GDBN} Command
30517 Part of @samp{info threads} supplies the same information.
30519 @subsubheading Example
30524 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30525 current-thread-id="1",number-of-threads="3"
30530 @subheading The @code{-thread-select} Command
30531 @findex -thread-select
30533 @subsubheading Synopsis
30536 -thread-select @var{threadnum}
30539 Make @var{threadnum} the current thread. It prints the number of the new
30540 current thread, and the topmost frame for that thread.
30542 This command is deprecated in favor of explicitly using the
30543 @samp{--thread} option to each command.
30545 @subsubheading @value{GDBN} Command
30547 The corresponding @value{GDBN} command is @samp{thread}.
30549 @subsubheading Example
30556 *stopped,reason="end-stepping-range",thread-id="2",line="187",
30557 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
30561 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
30562 number-of-threads="3"
30565 ^done,new-thread-id="3",
30566 frame=@{level="0",func="vprintf",
30567 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
30568 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
30572 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30573 @node GDB/MI Ada Tasking Commands
30574 @section @sc{gdb/mi} Ada Tasking Commands
30576 @subheading The @code{-ada-task-info} Command
30577 @findex -ada-task-info
30579 @subsubheading Synopsis
30582 -ada-task-info [ @var{task-id} ]
30585 Reports information about either a specific Ada task, if the
30586 @var{task-id} parameter is present, or about all Ada tasks.
30588 @subsubheading @value{GDBN} Command
30590 The @samp{info tasks} command prints the same information
30591 about all Ada tasks (@pxref{Ada Tasks}).
30593 @subsubheading Result
30595 The result is a table of Ada tasks. The following columns are
30596 defined for each Ada task:
30600 This field exists only for the current thread. It has the value @samp{*}.
30603 The identifier that @value{GDBN} uses to refer to the Ada task.
30606 The identifier that the target uses to refer to the Ada task.
30609 The identifier of the thread corresponding to the Ada task.
30611 This field should always exist, as Ada tasks are always implemented
30612 on top of a thread. But if @value{GDBN} cannot find this corresponding
30613 thread for any reason, the field is omitted.
30616 This field exists only when the task was created by another task.
30617 In this case, it provides the ID of the parent task.
30620 The base priority of the task.
30623 The current state of the task. For a detailed description of the
30624 possible states, see @ref{Ada Tasks}.
30627 The name of the task.
30631 @subsubheading Example
30635 ^done,tasks=@{nr_rows="3",nr_cols="8",
30636 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
30637 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
30638 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
30639 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
30640 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
30641 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
30642 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
30643 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
30644 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
30645 state="Child Termination Wait",name="main_task"@}]@}
30649 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30650 @node GDB/MI Program Execution
30651 @section @sc{gdb/mi} Program Execution
30653 These are the asynchronous commands which generate the out-of-band
30654 record @samp{*stopped}. Currently @value{GDBN} only really executes
30655 asynchronously with remote targets and this interaction is mimicked in
30658 @subheading The @code{-exec-continue} Command
30659 @findex -exec-continue
30661 @subsubheading Synopsis
30664 -exec-continue [--reverse] [--all|--thread-group N]
30667 Resumes the execution of the inferior program, which will continue
30668 to execute until it reaches a debugger stop event. If the
30669 @samp{--reverse} option is specified, execution resumes in reverse until
30670 it reaches a stop event. Stop events may include
30673 breakpoints or watchpoints
30675 signals or exceptions
30677 the end of the process (or its beginning under @samp{--reverse})
30679 the end or beginning of a replay log if one is being used.
30681 In all-stop mode (@pxref{All-Stop
30682 Mode}), may resume only one thread, or all threads, depending on the
30683 value of the @samp{scheduler-locking} variable. If @samp{--all} is
30684 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
30685 ignored in all-stop mode. If the @samp{--thread-group} options is
30686 specified, then all threads in that thread group are resumed.
30688 @subsubheading @value{GDBN} Command
30690 The corresponding @value{GDBN} corresponding is @samp{continue}.
30692 @subsubheading Example
30699 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
30700 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
30706 @subheading The @code{-exec-finish} Command
30707 @findex -exec-finish
30709 @subsubheading Synopsis
30712 -exec-finish [--reverse]
30715 Resumes the execution of the inferior program until the current
30716 function is exited. Displays the results returned by the function.
30717 If the @samp{--reverse} option is specified, resumes the reverse
30718 execution of the inferior program until the point where current
30719 function was called.
30721 @subsubheading @value{GDBN} Command
30723 The corresponding @value{GDBN} command is @samp{finish}.
30725 @subsubheading Example
30727 Function returning @code{void}.
30734 *stopped,reason="function-finished",frame=@{func="main",args=[],
30735 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
30739 Function returning other than @code{void}. The name of the internal
30740 @value{GDBN} variable storing the result is printed, together with the
30747 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
30748 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
30749 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30750 gdb-result-var="$1",return-value="0"
30755 @subheading The @code{-exec-interrupt} Command
30756 @findex -exec-interrupt
30758 @subsubheading Synopsis
30761 -exec-interrupt [--all|--thread-group N]
30764 Interrupts the background execution of the target. Note how the token
30765 associated with the stop message is the one for the execution command
30766 that has been interrupted. The token for the interrupt itself only
30767 appears in the @samp{^done} output. If the user is trying to
30768 interrupt a non-running program, an error message will be printed.
30770 Note that when asynchronous execution is enabled, this command is
30771 asynchronous just like other execution commands. That is, first the
30772 @samp{^done} response will be printed, and the target stop will be
30773 reported after that using the @samp{*stopped} notification.
30775 In non-stop mode, only the context thread is interrupted by default.
30776 All threads (in all inferiors) will be interrupted if the
30777 @samp{--all} option is specified. If the @samp{--thread-group}
30778 option is specified, all threads in that group will be interrupted.
30780 @subsubheading @value{GDBN} Command
30782 The corresponding @value{GDBN} command is @samp{interrupt}.
30784 @subsubheading Example
30795 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
30796 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
30797 fullname="/home/foo/bar/try.c",line="13"@}
30802 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
30806 @subheading The @code{-exec-jump} Command
30809 @subsubheading Synopsis
30812 -exec-jump @var{location}
30815 Resumes execution of the inferior program at the location specified by
30816 parameter. @xref{Specify Location}, for a description of the
30817 different forms of @var{location}.
30819 @subsubheading @value{GDBN} Command
30821 The corresponding @value{GDBN} command is @samp{jump}.
30823 @subsubheading Example
30826 -exec-jump foo.c:10
30827 *running,thread-id="all"
30832 @subheading The @code{-exec-next} Command
30835 @subsubheading Synopsis
30838 -exec-next [--reverse]
30841 Resumes execution of the inferior program, stopping when the beginning
30842 of the next source line is reached.
30844 If the @samp{--reverse} option is specified, resumes reverse execution
30845 of the inferior program, stopping at the beginning of the previous
30846 source line. If you issue this command on the first line of a
30847 function, it will take you back to the caller of that function, to the
30848 source line where the function was called.
30851 @subsubheading @value{GDBN} Command
30853 The corresponding @value{GDBN} command is @samp{next}.
30855 @subsubheading Example
30861 *stopped,reason="end-stepping-range",line="8",file="hello.c"
30866 @subheading The @code{-exec-next-instruction} Command
30867 @findex -exec-next-instruction
30869 @subsubheading Synopsis
30872 -exec-next-instruction [--reverse]
30875 Executes one machine instruction. If the instruction is a function
30876 call, continues until the function returns. If the program stops at an
30877 instruction in the middle of a source line, the address will be
30880 If the @samp{--reverse} option is specified, resumes reverse execution
30881 of the inferior program, stopping at the previous instruction. If the
30882 previously executed instruction was a return from another function,
30883 it will continue to execute in reverse until the call to that function
30884 (from the current stack frame) is reached.
30886 @subsubheading @value{GDBN} Command
30888 The corresponding @value{GDBN} command is @samp{nexti}.
30890 @subsubheading Example
30894 -exec-next-instruction
30898 *stopped,reason="end-stepping-range",
30899 addr="0x000100d4",line="5",file="hello.c"
30904 @subheading The @code{-exec-return} Command
30905 @findex -exec-return
30907 @subsubheading Synopsis
30913 Makes current function return immediately. Doesn't execute the inferior.
30914 Displays the new current frame.
30916 @subsubheading @value{GDBN} Command
30918 The corresponding @value{GDBN} command is @samp{return}.
30920 @subsubheading Example
30924 200-break-insert callee4
30925 200^done,bkpt=@{number="1",addr="0x00010734",
30926 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30931 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30932 frame=@{func="callee4",args=[],
30933 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30934 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
30940 111^done,frame=@{level="0",func="callee3",
30941 args=[@{name="strarg",
30942 value="0x11940 \"A string argument.\""@}],
30943 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30944 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
30949 @subheading The @code{-exec-run} Command
30952 @subsubheading Synopsis
30955 -exec-run [--all | --thread-group N]
30958 Starts execution of the inferior from the beginning. The inferior
30959 executes until either a breakpoint is encountered or the program
30960 exits. In the latter case the output will include an exit code, if
30961 the program has exited exceptionally.
30963 When no option is specified, the current inferior is started. If the
30964 @samp{--thread-group} option is specified, it should refer to a thread
30965 group of type @samp{process}, and that thread group will be started.
30966 If the @samp{--all} option is specified, then all inferiors will be started.
30968 @subsubheading @value{GDBN} Command
30970 The corresponding @value{GDBN} command is @samp{run}.
30972 @subsubheading Examples
30977 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
30982 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
30983 frame=@{func="main",args=[],file="recursive2.c",
30984 fullname="/home/foo/bar/recursive2.c",line="4"@}
30989 Program exited normally:
30997 *stopped,reason="exited-normally"
31002 Program exited exceptionally:
31010 *stopped,reason="exited",exit-code="01"
31014 Another way the program can terminate is if it receives a signal such as
31015 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
31019 *stopped,reason="exited-signalled",signal-name="SIGINT",
31020 signal-meaning="Interrupt"
31024 @c @subheading -exec-signal
31027 @subheading The @code{-exec-step} Command
31030 @subsubheading Synopsis
31033 -exec-step [--reverse]
31036 Resumes execution of the inferior program, stopping when the beginning
31037 of the next source line is reached, if the next source line is not a
31038 function call. If it is, stop at the first instruction of the called
31039 function. If the @samp{--reverse} option is specified, resumes reverse
31040 execution of the inferior program, stopping at the beginning of the
31041 previously executed source line.
31043 @subsubheading @value{GDBN} Command
31045 The corresponding @value{GDBN} command is @samp{step}.
31047 @subsubheading Example
31049 Stepping into a function:
31055 *stopped,reason="end-stepping-range",
31056 frame=@{func="foo",args=[@{name="a",value="10"@},
31057 @{name="b",value="0"@}],file="recursive2.c",
31058 fullname="/home/foo/bar/recursive2.c",line="11"@}
31068 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
31073 @subheading The @code{-exec-step-instruction} Command
31074 @findex -exec-step-instruction
31076 @subsubheading Synopsis
31079 -exec-step-instruction [--reverse]
31082 Resumes the inferior which executes one machine instruction. If the
31083 @samp{--reverse} option is specified, resumes reverse execution of the
31084 inferior program, stopping at the previously executed instruction.
31085 The output, once @value{GDBN} has stopped, will vary depending on
31086 whether we have stopped in the middle of a source line or not. In the
31087 former case, the address at which the program stopped will be printed
31090 @subsubheading @value{GDBN} Command
31092 The corresponding @value{GDBN} command is @samp{stepi}.
31094 @subsubheading Example
31098 -exec-step-instruction
31102 *stopped,reason="end-stepping-range",
31103 frame=@{func="foo",args=[],file="try.c",
31104 fullname="/home/foo/bar/try.c",line="10"@}
31106 -exec-step-instruction
31110 *stopped,reason="end-stepping-range",
31111 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
31112 fullname="/home/foo/bar/try.c",line="10"@}
31117 @subheading The @code{-exec-until} Command
31118 @findex -exec-until
31120 @subsubheading Synopsis
31123 -exec-until [ @var{location} ]
31126 Executes the inferior until the @var{location} specified in the
31127 argument is reached. If there is no argument, the inferior executes
31128 until a source line greater than the current one is reached. The
31129 reason for stopping in this case will be @samp{location-reached}.
31131 @subsubheading @value{GDBN} Command
31133 The corresponding @value{GDBN} command is @samp{until}.
31135 @subsubheading Example
31139 -exec-until recursive2.c:6
31143 *stopped,reason="location-reached",frame=@{func="main",args=[],
31144 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
31149 @subheading -file-clear
31150 Is this going away????
31153 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31154 @node GDB/MI Stack Manipulation
31155 @section @sc{gdb/mi} Stack Manipulation Commands
31157 @subheading The @code{-enable-frame-filters} Command
31158 @findex -enable-frame-filters
31161 -enable-frame-filters
31164 @value{GDBN} allows Python-based frame filters to affect the output of
31165 the MI commands relating to stack traces. As there is no way to
31166 implement this in a fully backward-compatible way, a front end must
31167 request that this functionality be enabled.
31169 Once enabled, this feature cannot be disabled.
31171 Note that if Python support has not been compiled into @value{GDBN},
31172 this command will still succeed (and do nothing).
31174 @subheading The @code{-stack-info-frame} Command
31175 @findex -stack-info-frame
31177 @subsubheading Synopsis
31183 Get info on the selected frame.
31185 @subsubheading @value{GDBN} Command
31187 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
31188 (without arguments).
31190 @subsubheading Example
31195 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
31196 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31197 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
31201 @subheading The @code{-stack-info-depth} Command
31202 @findex -stack-info-depth
31204 @subsubheading Synopsis
31207 -stack-info-depth [ @var{max-depth} ]
31210 Return the depth of the stack. If the integer argument @var{max-depth}
31211 is specified, do not count beyond @var{max-depth} frames.
31213 @subsubheading @value{GDBN} Command
31215 There's no equivalent @value{GDBN} command.
31217 @subsubheading Example
31219 For a stack with frame levels 0 through 11:
31226 -stack-info-depth 4
31229 -stack-info-depth 12
31232 -stack-info-depth 11
31235 -stack-info-depth 13
31240 @anchor{-stack-list-arguments}
31241 @subheading The @code{-stack-list-arguments} Command
31242 @findex -stack-list-arguments
31244 @subsubheading Synopsis
31247 -stack-list-arguments [ --no-frame-filters ] @var{print-values}
31248 [ @var{low-frame} @var{high-frame} ]
31251 Display a list of the arguments for the frames between @var{low-frame}
31252 and @var{high-frame} (inclusive). If @var{low-frame} and
31253 @var{high-frame} are not provided, list the arguments for the whole
31254 call stack. If the two arguments are equal, show the single frame
31255 at the corresponding level. It is an error if @var{low-frame} is
31256 larger than the actual number of frames. On the other hand,
31257 @var{high-frame} may be larger than the actual number of frames, in
31258 which case only existing frames will be returned.
31260 If @var{print-values} is 0 or @code{--no-values}, print only the names of
31261 the variables; if it is 1 or @code{--all-values}, print also their
31262 values; and if it is 2 or @code{--simple-values}, print the name,
31263 type and value for simple data types, and the name and type for arrays,
31264 structures and unions. If the option @code{--no-frame-filters} is
31265 supplied, then Python frame filters will not be executed.
31268 Use of this command to obtain arguments in a single frame is
31269 deprecated in favor of the @samp{-stack-list-variables} command.
31271 @subsubheading @value{GDBN} Command
31273 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
31274 @samp{gdb_get_args} command which partially overlaps with the
31275 functionality of @samp{-stack-list-arguments}.
31277 @subsubheading Example
31284 frame=@{level="0",addr="0x00010734",func="callee4",
31285 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31286 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
31287 frame=@{level="1",addr="0x0001076c",func="callee3",
31288 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31289 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
31290 frame=@{level="2",addr="0x0001078c",func="callee2",
31291 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31292 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
31293 frame=@{level="3",addr="0x000107b4",func="callee1",
31294 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31295 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
31296 frame=@{level="4",addr="0x000107e0",func="main",
31297 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
31298 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
31300 -stack-list-arguments 0
31303 frame=@{level="0",args=[]@},
31304 frame=@{level="1",args=[name="strarg"]@},
31305 frame=@{level="2",args=[name="intarg",name="strarg"]@},
31306 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
31307 frame=@{level="4",args=[]@}]
31309 -stack-list-arguments 1
31312 frame=@{level="0",args=[]@},
31314 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31315 frame=@{level="2",args=[
31316 @{name="intarg",value="2"@},
31317 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
31318 @{frame=@{level="3",args=[
31319 @{name="intarg",value="2"@},
31320 @{name="strarg",value="0x11940 \"A string argument.\""@},
31321 @{name="fltarg",value="3.5"@}]@},
31322 frame=@{level="4",args=[]@}]
31324 -stack-list-arguments 0 2 2
31325 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
31327 -stack-list-arguments 1 2 2
31328 ^done,stack-args=[frame=@{level="2",
31329 args=[@{name="intarg",value="2"@},
31330 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
31334 @c @subheading -stack-list-exception-handlers
31337 @anchor{-stack-list-frames}
31338 @subheading The @code{-stack-list-frames} Command
31339 @findex -stack-list-frames
31341 @subsubheading Synopsis
31344 -stack-list-frames [ --no-frame-filters @var{low-frame} @var{high-frame} ]
31347 List the frames currently on the stack. For each frame it displays the
31352 The frame number, 0 being the topmost frame, i.e., the innermost function.
31354 The @code{$pc} value for that frame.
31358 File name of the source file where the function lives.
31359 @item @var{fullname}
31360 The full file name of the source file where the function lives.
31362 Line number corresponding to the @code{$pc}.
31364 The shared library where this function is defined. This is only given
31365 if the frame's function is not known.
31368 If invoked without arguments, this command prints a backtrace for the
31369 whole stack. If given two integer arguments, it shows the frames whose
31370 levels are between the two arguments (inclusive). If the two arguments
31371 are equal, it shows the single frame at the corresponding level. It is
31372 an error if @var{low-frame} is larger than the actual number of
31373 frames. On the other hand, @var{high-frame} may be larger than the
31374 actual number of frames, in which case only existing frames will be
31375 returned. If the option @code{--no-frame-filters} is supplied, then
31376 Python frame filters will not be executed.
31378 @subsubheading @value{GDBN} Command
31380 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
31382 @subsubheading Example
31384 Full stack backtrace:
31390 [frame=@{level="0",addr="0x0001076c",func="foo",
31391 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
31392 frame=@{level="1",addr="0x000107a4",func="foo",
31393 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31394 frame=@{level="2",addr="0x000107a4",func="foo",
31395 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31396 frame=@{level="3",addr="0x000107a4",func="foo",
31397 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31398 frame=@{level="4",addr="0x000107a4",func="foo",
31399 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31400 frame=@{level="5",addr="0x000107a4",func="foo",
31401 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31402 frame=@{level="6",addr="0x000107a4",func="foo",
31403 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31404 frame=@{level="7",addr="0x000107a4",func="foo",
31405 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31406 frame=@{level="8",addr="0x000107a4",func="foo",
31407 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31408 frame=@{level="9",addr="0x000107a4",func="foo",
31409 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31410 frame=@{level="10",addr="0x000107a4",func="foo",
31411 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31412 frame=@{level="11",addr="0x00010738",func="main",
31413 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
31417 Show frames between @var{low_frame} and @var{high_frame}:
31421 -stack-list-frames 3 5
31423 [frame=@{level="3",addr="0x000107a4",func="foo",
31424 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31425 frame=@{level="4",addr="0x000107a4",func="foo",
31426 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
31427 frame=@{level="5",addr="0x000107a4",func="foo",
31428 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31432 Show a single frame:
31436 -stack-list-frames 3 3
31438 [frame=@{level="3",addr="0x000107a4",func="foo",
31439 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
31444 @subheading The @code{-stack-list-locals} Command
31445 @findex -stack-list-locals
31446 @anchor{-stack-list-locals}
31448 @subsubheading Synopsis
31451 -stack-list-locals [ --no-frame-filters ] @var{print-values}
31454 Display the local variable names for the selected frame. If
31455 @var{print-values} is 0 or @code{--no-values}, print only the names of
31456 the variables; if it is 1 or @code{--all-values}, print also their
31457 values; and if it is 2 or @code{--simple-values}, print the name,
31458 type and value for simple data types, and the name and type for arrays,
31459 structures and unions. In this last case, a frontend can immediately
31460 display the value of simple data types and create variable objects for
31461 other data types when the user wishes to explore their values in
31462 more detail. If the option @code{--no-frame-filters} is supplied, then
31463 Python frame filters will not be executed.
31465 This command is deprecated in favor of the
31466 @samp{-stack-list-variables} command.
31468 @subsubheading @value{GDBN} Command
31470 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
31472 @subsubheading Example
31476 -stack-list-locals 0
31477 ^done,locals=[name="A",name="B",name="C"]
31479 -stack-list-locals --all-values
31480 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
31481 @{name="C",value="@{1, 2, 3@}"@}]
31482 -stack-list-locals --simple-values
31483 ^done,locals=[@{name="A",type="int",value="1"@},
31484 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
31488 @anchor{-stack-list-variables}
31489 @subheading The @code{-stack-list-variables} Command
31490 @findex -stack-list-variables
31492 @subsubheading Synopsis
31495 -stack-list-variables [ --no-frame-filters ] @var{print-values}
31498 Display the names of local variables and function arguments for the selected frame. If
31499 @var{print-values} is 0 or @code{--no-values}, print only the names of
31500 the variables; if it is 1 or @code{--all-values}, print also their
31501 values; and if it is 2 or @code{--simple-values}, print the name,
31502 type and value for simple data types, and the name and type for arrays,
31503 structures and unions. If the option @code{--no-frame-filters} is
31504 supplied, then Python frame filters will not be executed.
31506 @subsubheading Example
31510 -stack-list-variables --thread 1 --frame 0 --all-values
31511 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
31516 @subheading The @code{-stack-select-frame} Command
31517 @findex -stack-select-frame
31519 @subsubheading Synopsis
31522 -stack-select-frame @var{framenum}
31525 Change the selected frame. Select a different frame @var{framenum} on
31528 This command in deprecated in favor of passing the @samp{--frame}
31529 option to every command.
31531 @subsubheading @value{GDBN} Command
31533 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
31534 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
31536 @subsubheading Example
31540 -stack-select-frame 2
31545 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31546 @node GDB/MI Variable Objects
31547 @section @sc{gdb/mi} Variable Objects
31551 @subheading Motivation for Variable Objects in @sc{gdb/mi}
31553 For the implementation of a variable debugger window (locals, watched
31554 expressions, etc.), we are proposing the adaptation of the existing code
31555 used by @code{Insight}.
31557 The two main reasons for that are:
31561 It has been proven in practice (it is already on its second generation).
31564 It will shorten development time (needless to say how important it is
31568 The original interface was designed to be used by Tcl code, so it was
31569 slightly changed so it could be used through @sc{gdb/mi}. This section
31570 describes the @sc{gdb/mi} operations that will be available and gives some
31571 hints about their use.
31573 @emph{Note}: In addition to the set of operations described here, we
31574 expect the @sc{gui} implementation of a variable window to require, at
31575 least, the following operations:
31578 @item @code{-gdb-show} @code{output-radix}
31579 @item @code{-stack-list-arguments}
31580 @item @code{-stack-list-locals}
31581 @item @code{-stack-select-frame}
31586 @subheading Introduction to Variable Objects
31588 @cindex variable objects in @sc{gdb/mi}
31590 Variable objects are "object-oriented" MI interface for examining and
31591 changing values of expressions. Unlike some other MI interfaces that
31592 work with expressions, variable objects are specifically designed for
31593 simple and efficient presentation in the frontend. A variable object
31594 is identified by string name. When a variable object is created, the
31595 frontend specifies the expression for that variable object. The
31596 expression can be a simple variable, or it can be an arbitrary complex
31597 expression, and can even involve CPU registers. After creating a
31598 variable object, the frontend can invoke other variable object
31599 operations---for example to obtain or change the value of a variable
31600 object, or to change display format.
31602 Variable objects have hierarchical tree structure. Any variable object
31603 that corresponds to a composite type, such as structure in C, has
31604 a number of child variable objects, for example corresponding to each
31605 element of a structure. A child variable object can itself have
31606 children, recursively. Recursion ends when we reach
31607 leaf variable objects, which always have built-in types. Child variable
31608 objects are created only by explicit request, so if a frontend
31609 is not interested in the children of a particular variable object, no
31610 child will be created.
31612 For a leaf variable object it is possible to obtain its value as a
31613 string, or set the value from a string. String value can be also
31614 obtained for a non-leaf variable object, but it's generally a string
31615 that only indicates the type of the object, and does not list its
31616 contents. Assignment to a non-leaf variable object is not allowed.
31618 A frontend does not need to read the values of all variable objects each time
31619 the program stops. Instead, MI provides an update command that lists all
31620 variable objects whose values has changed since the last update
31621 operation. This considerably reduces the amount of data that must
31622 be transferred to the frontend. As noted above, children variable
31623 objects are created on demand, and only leaf variable objects have a
31624 real value. As result, gdb will read target memory only for leaf
31625 variables that frontend has created.
31627 The automatic update is not always desirable. For example, a frontend
31628 might want to keep a value of some expression for future reference,
31629 and never update it. For another example, fetching memory is
31630 relatively slow for embedded targets, so a frontend might want
31631 to disable automatic update for the variables that are either not
31632 visible on the screen, or ``closed''. This is possible using so
31633 called ``frozen variable objects''. Such variable objects are never
31634 implicitly updated.
31636 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
31637 fixed variable object, the expression is parsed when the variable
31638 object is created, including associating identifiers to specific
31639 variables. The meaning of expression never changes. For a floating
31640 variable object the values of variables whose names appear in the
31641 expressions are re-evaluated every time in the context of the current
31642 frame. Consider this example:
31647 struct work_state state;
31654 If a fixed variable object for the @code{state} variable is created in
31655 this function, and we enter the recursive call, the variable
31656 object will report the value of @code{state} in the top-level
31657 @code{do_work} invocation. On the other hand, a floating variable
31658 object will report the value of @code{state} in the current frame.
31660 If an expression specified when creating a fixed variable object
31661 refers to a local variable, the variable object becomes bound to the
31662 thread and frame in which the variable object is created. When such
31663 variable object is updated, @value{GDBN} makes sure that the
31664 thread/frame combination the variable object is bound to still exists,
31665 and re-evaluates the variable object in context of that thread/frame.
31667 The following is the complete set of @sc{gdb/mi} operations defined to
31668 access this functionality:
31670 @multitable @columnfractions .4 .6
31671 @item @strong{Operation}
31672 @tab @strong{Description}
31674 @item @code{-enable-pretty-printing}
31675 @tab enable Python-based pretty-printing
31676 @item @code{-var-create}
31677 @tab create a variable object
31678 @item @code{-var-delete}
31679 @tab delete the variable object and/or its children
31680 @item @code{-var-set-format}
31681 @tab set the display format of this variable
31682 @item @code{-var-show-format}
31683 @tab show the display format of this variable
31684 @item @code{-var-info-num-children}
31685 @tab tells how many children this object has
31686 @item @code{-var-list-children}
31687 @tab return a list of the object's children
31688 @item @code{-var-info-type}
31689 @tab show the type of this variable object
31690 @item @code{-var-info-expression}
31691 @tab print parent-relative expression that this variable object represents
31692 @item @code{-var-info-path-expression}
31693 @tab print full expression that this variable object represents
31694 @item @code{-var-show-attributes}
31695 @tab is this variable editable? does it exist here?
31696 @item @code{-var-evaluate-expression}
31697 @tab get the value of this variable
31698 @item @code{-var-assign}
31699 @tab set the value of this variable
31700 @item @code{-var-update}
31701 @tab update the variable and its children
31702 @item @code{-var-set-frozen}
31703 @tab set frozeness attribute
31704 @item @code{-var-set-update-range}
31705 @tab set range of children to display on update
31708 In the next subsection we describe each operation in detail and suggest
31709 how it can be used.
31711 @subheading Description And Use of Operations on Variable Objects
31713 @subheading The @code{-enable-pretty-printing} Command
31714 @findex -enable-pretty-printing
31717 -enable-pretty-printing
31720 @value{GDBN} allows Python-based visualizers to affect the output of the
31721 MI variable object commands. However, because there was no way to
31722 implement this in a fully backward-compatible way, a front end must
31723 request that this functionality be enabled.
31725 Once enabled, this feature cannot be disabled.
31727 Note that if Python support has not been compiled into @value{GDBN},
31728 this command will still succeed (and do nothing).
31730 This feature is currently (as of @value{GDBN} 7.0) experimental, and
31731 may work differently in future versions of @value{GDBN}.
31733 @subheading The @code{-var-create} Command
31734 @findex -var-create
31736 @subsubheading Synopsis
31739 -var-create @{@var{name} | "-"@}
31740 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
31743 This operation creates a variable object, which allows the monitoring of
31744 a variable, the result of an expression, a memory cell or a CPU
31747 The @var{name} parameter is the string by which the object can be
31748 referenced. It must be unique. If @samp{-} is specified, the varobj
31749 system will generate a string ``varNNNNNN'' automatically. It will be
31750 unique provided that one does not specify @var{name} of that format.
31751 The command fails if a duplicate name is found.
31753 The frame under which the expression should be evaluated can be
31754 specified by @var{frame-addr}. A @samp{*} indicates that the current
31755 frame should be used. A @samp{@@} indicates that a floating variable
31756 object must be created.
31758 @var{expression} is any expression valid on the current language set (must not
31759 begin with a @samp{*}), or one of the following:
31763 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
31766 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
31769 @samp{$@var{regname}} --- a CPU register name
31772 @cindex dynamic varobj
31773 A varobj's contents may be provided by a Python-based pretty-printer. In this
31774 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
31775 have slightly different semantics in some cases. If the
31776 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
31777 will never create a dynamic varobj. This ensures backward
31778 compatibility for existing clients.
31780 @subsubheading Result
31782 This operation returns attributes of the newly-created varobj. These
31787 The name of the varobj.
31790 The number of children of the varobj. This number is not necessarily
31791 reliable for a dynamic varobj. Instead, you must examine the
31792 @samp{has_more} attribute.
31795 The varobj's scalar value. For a varobj whose type is some sort of
31796 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
31797 will not be interesting.
31800 The varobj's type. This is a string representation of the type, as
31801 would be printed by the @value{GDBN} CLI. If @samp{print object}
31802 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31803 @emph{actual} (derived) type of the object is shown rather than the
31804 @emph{declared} one.
31807 If a variable object is bound to a specific thread, then this is the
31808 thread's identifier.
31811 For a dynamic varobj, this indicates whether there appear to be any
31812 children available. For a non-dynamic varobj, this will be 0.
31815 This attribute will be present and have the value @samp{1} if the
31816 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31817 then this attribute will not be present.
31820 A dynamic varobj can supply a display hint to the front end. The
31821 value comes directly from the Python pretty-printer object's
31822 @code{display_hint} method. @xref{Pretty Printing API}.
31825 Typical output will look like this:
31828 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
31829 has_more="@var{has_more}"
31833 @subheading The @code{-var-delete} Command
31834 @findex -var-delete
31836 @subsubheading Synopsis
31839 -var-delete [ -c ] @var{name}
31842 Deletes a previously created variable object and all of its children.
31843 With the @samp{-c} option, just deletes the children.
31845 Returns an error if the object @var{name} is not found.
31848 @subheading The @code{-var-set-format} Command
31849 @findex -var-set-format
31851 @subsubheading Synopsis
31854 -var-set-format @var{name} @var{format-spec}
31857 Sets the output format for the value of the object @var{name} to be
31860 @anchor{-var-set-format}
31861 The syntax for the @var{format-spec} is as follows:
31864 @var{format-spec} @expansion{}
31865 @{binary | decimal | hexadecimal | octal | natural@}
31868 The natural format is the default format choosen automatically
31869 based on the variable type (like decimal for an @code{int}, hex
31870 for pointers, etc.).
31872 For a variable with children, the format is set only on the
31873 variable itself, and the children are not affected.
31875 @subheading The @code{-var-show-format} Command
31876 @findex -var-show-format
31878 @subsubheading Synopsis
31881 -var-show-format @var{name}
31884 Returns the format used to display the value of the object @var{name}.
31887 @var{format} @expansion{}
31892 @subheading The @code{-var-info-num-children} Command
31893 @findex -var-info-num-children
31895 @subsubheading Synopsis
31898 -var-info-num-children @var{name}
31901 Returns the number of children of a variable object @var{name}:
31907 Note that this number is not completely reliable for a dynamic varobj.
31908 It will return the current number of children, but more children may
31912 @subheading The @code{-var-list-children} Command
31913 @findex -var-list-children
31915 @subsubheading Synopsis
31918 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
31920 @anchor{-var-list-children}
31922 Return a list of the children of the specified variable object and
31923 create variable objects for them, if they do not already exist. With
31924 a single argument or if @var{print-values} has a value of 0 or
31925 @code{--no-values}, print only the names of the variables; if
31926 @var{print-values} is 1 or @code{--all-values}, also print their
31927 values; and if it is 2 or @code{--simple-values} print the name and
31928 value for simple data types and just the name for arrays, structures
31931 @var{from} and @var{to}, if specified, indicate the range of children
31932 to report. If @var{from} or @var{to} is less than zero, the range is
31933 reset and all children will be reported. Otherwise, children starting
31934 at @var{from} (zero-based) and up to and excluding @var{to} will be
31937 If a child range is requested, it will only affect the current call to
31938 @code{-var-list-children}, but not future calls to @code{-var-update}.
31939 For this, you must instead use @code{-var-set-update-range}. The
31940 intent of this approach is to enable a front end to implement any
31941 update approach it likes; for example, scrolling a view may cause the
31942 front end to request more children with @code{-var-list-children}, and
31943 then the front end could call @code{-var-set-update-range} with a
31944 different range to ensure that future updates are restricted to just
31947 For each child the following results are returned:
31952 Name of the variable object created for this child.
31955 The expression to be shown to the user by the front end to designate this child.
31956 For example this may be the name of a structure member.
31958 For a dynamic varobj, this value cannot be used to form an
31959 expression. There is no way to do this at all with a dynamic varobj.
31961 For C/C@t{++} structures there are several pseudo children returned to
31962 designate access qualifiers. For these pseudo children @var{exp} is
31963 @samp{public}, @samp{private}, or @samp{protected}. In this case the
31964 type and value are not present.
31966 A dynamic varobj will not report the access qualifying
31967 pseudo-children, regardless of the language. This information is not
31968 available at all with a dynamic varobj.
31971 Number of children this child has. For a dynamic varobj, this will be
31975 The type of the child. If @samp{print object}
31976 (@pxref{Print Settings, set print object}) is set to @code{on}, the
31977 @emph{actual} (derived) type of the object is shown rather than the
31978 @emph{declared} one.
31981 If values were requested, this is the value.
31984 If this variable object is associated with a thread, this is the thread id.
31985 Otherwise this result is not present.
31988 If the variable object is frozen, this variable will be present with a value of 1.
31991 The result may have its own attributes:
31995 A dynamic varobj can supply a display hint to the front end. The
31996 value comes directly from the Python pretty-printer object's
31997 @code{display_hint} method. @xref{Pretty Printing API}.
32000 This is an integer attribute which is nonzero if there are children
32001 remaining after the end of the selected range.
32004 @subsubheading Example
32008 -var-list-children n
32009 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32010 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
32012 -var-list-children --all-values n
32013 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
32014 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
32018 @subheading The @code{-var-info-type} Command
32019 @findex -var-info-type
32021 @subsubheading Synopsis
32024 -var-info-type @var{name}
32027 Returns the type of the specified variable @var{name}. The type is
32028 returned as a string in the same format as it is output by the
32032 type=@var{typename}
32036 @subheading The @code{-var-info-expression} Command
32037 @findex -var-info-expression
32039 @subsubheading Synopsis
32042 -var-info-expression @var{name}
32045 Returns a string that is suitable for presenting this
32046 variable object in user interface. The string is generally
32047 not valid expression in the current language, and cannot be evaluated.
32049 For example, if @code{a} is an array, and variable object
32050 @code{A} was created for @code{a}, then we'll get this output:
32053 (gdb) -var-info-expression A.1
32054 ^done,lang="C",exp="1"
32058 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
32060 Note that the output of the @code{-var-list-children} command also
32061 includes those expressions, so the @code{-var-info-expression} command
32064 @subheading The @code{-var-info-path-expression} Command
32065 @findex -var-info-path-expression
32067 @subsubheading Synopsis
32070 -var-info-path-expression @var{name}
32073 Returns an expression that can be evaluated in the current
32074 context and will yield the same value that a variable object has.
32075 Compare this with the @code{-var-info-expression} command, which
32076 result can be used only for UI presentation. Typical use of
32077 the @code{-var-info-path-expression} command is creating a
32078 watchpoint from a variable object.
32080 This command is currently not valid for children of a dynamic varobj,
32081 and will give an error when invoked on one.
32083 For example, suppose @code{C} is a C@t{++} class, derived from class
32084 @code{Base}, and that the @code{Base} class has a member called
32085 @code{m_size}. Assume a variable @code{c} is has the type of
32086 @code{C} and a variable object @code{C} was created for variable
32087 @code{c}. Then, we'll get this output:
32089 (gdb) -var-info-path-expression C.Base.public.m_size
32090 ^done,path_expr=((Base)c).m_size)
32093 @subheading The @code{-var-show-attributes} Command
32094 @findex -var-show-attributes
32096 @subsubheading Synopsis
32099 -var-show-attributes @var{name}
32102 List attributes of the specified variable object @var{name}:
32105 status=@var{attr} [ ( ,@var{attr} )* ]
32109 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
32111 @subheading The @code{-var-evaluate-expression} Command
32112 @findex -var-evaluate-expression
32114 @subsubheading Synopsis
32117 -var-evaluate-expression [-f @var{format-spec}] @var{name}
32120 Evaluates the expression that is represented by the specified variable
32121 object and returns its value as a string. The format of the string
32122 can be specified with the @samp{-f} option. The possible values of
32123 this option are the same as for @code{-var-set-format}
32124 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
32125 the current display format will be used. The current display format
32126 can be changed using the @code{-var-set-format} command.
32132 Note that one must invoke @code{-var-list-children} for a variable
32133 before the value of a child variable can be evaluated.
32135 @subheading The @code{-var-assign} Command
32136 @findex -var-assign
32138 @subsubheading Synopsis
32141 -var-assign @var{name} @var{expression}
32144 Assigns the value of @var{expression} to the variable object specified
32145 by @var{name}. The object must be @samp{editable}. If the variable's
32146 value is altered by the assign, the variable will show up in any
32147 subsequent @code{-var-update} list.
32149 @subsubheading Example
32157 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
32161 @subheading The @code{-var-update} Command
32162 @findex -var-update
32164 @subsubheading Synopsis
32167 -var-update [@var{print-values}] @{@var{name} | "*"@}
32170 Reevaluate the expressions corresponding to the variable object
32171 @var{name} and all its direct and indirect children, and return the
32172 list of variable objects whose values have changed; @var{name} must
32173 be a root variable object. Here, ``changed'' means that the result of
32174 @code{-var-evaluate-expression} before and after the
32175 @code{-var-update} is different. If @samp{*} is used as the variable
32176 object names, all existing variable objects are updated, except
32177 for frozen ones (@pxref{-var-set-frozen}). The option
32178 @var{print-values} determines whether both names and values, or just
32179 names are printed. The possible values of this option are the same
32180 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
32181 recommended to use the @samp{--all-values} option, to reduce the
32182 number of MI commands needed on each program stop.
32184 With the @samp{*} parameter, if a variable object is bound to a
32185 currently running thread, it will not be updated, without any
32188 If @code{-var-set-update-range} was previously used on a varobj, then
32189 only the selected range of children will be reported.
32191 @code{-var-update} reports all the changed varobjs in a tuple named
32194 Each item in the change list is itself a tuple holding:
32198 The name of the varobj.
32201 If values were requested for this update, then this field will be
32202 present and will hold the value of the varobj.
32205 @anchor{-var-update}
32206 This field is a string which may take one of three values:
32210 The variable object's current value is valid.
32213 The variable object does not currently hold a valid value but it may
32214 hold one in the future if its associated expression comes back into
32218 The variable object no longer holds a valid value.
32219 This can occur when the executable file being debugged has changed,
32220 either through recompilation or by using the @value{GDBN} @code{file}
32221 command. The front end should normally choose to delete these variable
32225 In the future new values may be added to this list so the front should
32226 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
32229 This is only present if the varobj is still valid. If the type
32230 changed, then this will be the string @samp{true}; otherwise it will
32233 When a varobj's type changes, its children are also likely to have
32234 become incorrect. Therefore, the varobj's children are automatically
32235 deleted when this attribute is @samp{true}. Also, the varobj's update
32236 range, when set using the @code{-var-set-update-range} command, is
32240 If the varobj's type changed, then this field will be present and will
32243 @item new_num_children
32244 For a dynamic varobj, if the number of children changed, or if the
32245 type changed, this will be the new number of children.
32247 The @samp{numchild} field in other varobj responses is generally not
32248 valid for a dynamic varobj -- it will show the number of children that
32249 @value{GDBN} knows about, but because dynamic varobjs lazily
32250 instantiate their children, this will not reflect the number of
32251 children which may be available.
32253 The @samp{new_num_children} attribute only reports changes to the
32254 number of children known by @value{GDBN}. This is the only way to
32255 detect whether an update has removed children (which necessarily can
32256 only happen at the end of the update range).
32259 The display hint, if any.
32262 This is an integer value, which will be 1 if there are more children
32263 available outside the varobj's update range.
32266 This attribute will be present and have the value @samp{1} if the
32267 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
32268 then this attribute will not be present.
32271 If new children were added to a dynamic varobj within the selected
32272 update range (as set by @code{-var-set-update-range}), then they will
32273 be listed in this attribute.
32276 @subsubheading Example
32283 -var-update --all-values var1
32284 ^done,changelist=[@{name="var1",value="3",in_scope="true",
32285 type_changed="false"@}]
32289 @subheading The @code{-var-set-frozen} Command
32290 @findex -var-set-frozen
32291 @anchor{-var-set-frozen}
32293 @subsubheading Synopsis
32296 -var-set-frozen @var{name} @var{flag}
32299 Set the frozenness flag on the variable object @var{name}. The
32300 @var{flag} parameter should be either @samp{1} to make the variable
32301 frozen or @samp{0} to make it unfrozen. If a variable object is
32302 frozen, then neither itself, nor any of its children, are
32303 implicitly updated by @code{-var-update} of
32304 a parent variable or by @code{-var-update *}. Only
32305 @code{-var-update} of the variable itself will update its value and
32306 values of its children. After a variable object is unfrozen, it is
32307 implicitly updated by all subsequent @code{-var-update} operations.
32308 Unfreezing a variable does not update it, only subsequent
32309 @code{-var-update} does.
32311 @subsubheading Example
32315 -var-set-frozen V 1
32320 @subheading The @code{-var-set-update-range} command
32321 @findex -var-set-update-range
32322 @anchor{-var-set-update-range}
32324 @subsubheading Synopsis
32327 -var-set-update-range @var{name} @var{from} @var{to}
32330 Set the range of children to be returned by future invocations of
32331 @code{-var-update}.
32333 @var{from} and @var{to} indicate the range of children to report. If
32334 @var{from} or @var{to} is less than zero, the range is reset and all
32335 children will be reported. Otherwise, children starting at @var{from}
32336 (zero-based) and up to and excluding @var{to} will be reported.
32338 @subsubheading Example
32342 -var-set-update-range V 1 2
32346 @subheading The @code{-var-set-visualizer} command
32347 @findex -var-set-visualizer
32348 @anchor{-var-set-visualizer}
32350 @subsubheading Synopsis
32353 -var-set-visualizer @var{name} @var{visualizer}
32356 Set a visualizer for the variable object @var{name}.
32358 @var{visualizer} is the visualizer to use. The special value
32359 @samp{None} means to disable any visualizer in use.
32361 If not @samp{None}, @var{visualizer} must be a Python expression.
32362 This expression must evaluate to a callable object which accepts a
32363 single argument. @value{GDBN} will call this object with the value of
32364 the varobj @var{name} as an argument (this is done so that the same
32365 Python pretty-printing code can be used for both the CLI and MI).
32366 When called, this object must return an object which conforms to the
32367 pretty-printing interface (@pxref{Pretty Printing API}).
32369 The pre-defined function @code{gdb.default_visualizer} may be used to
32370 select a visualizer by following the built-in process
32371 (@pxref{Selecting Pretty-Printers}). This is done automatically when
32372 a varobj is created, and so ordinarily is not needed.
32374 This feature is only available if Python support is enabled. The MI
32375 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
32376 can be used to check this.
32378 @subsubheading Example
32380 Resetting the visualizer:
32384 -var-set-visualizer V None
32388 Reselecting the default (type-based) visualizer:
32392 -var-set-visualizer V gdb.default_visualizer
32396 Suppose @code{SomeClass} is a visualizer class. A lambda expression
32397 can be used to instantiate this class for a varobj:
32401 -var-set-visualizer V "lambda val: SomeClass()"
32405 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32406 @node GDB/MI Data Manipulation
32407 @section @sc{gdb/mi} Data Manipulation
32409 @cindex data manipulation, in @sc{gdb/mi}
32410 @cindex @sc{gdb/mi}, data manipulation
32411 This section describes the @sc{gdb/mi} commands that manipulate data:
32412 examine memory and registers, evaluate expressions, etc.
32414 @c REMOVED FROM THE INTERFACE.
32415 @c @subheading -data-assign
32416 @c Change the value of a program variable. Plenty of side effects.
32417 @c @subsubheading GDB Command
32419 @c @subsubheading Example
32422 @subheading The @code{-data-disassemble} Command
32423 @findex -data-disassemble
32425 @subsubheading Synopsis
32429 [ -s @var{start-addr} -e @var{end-addr} ]
32430 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
32438 @item @var{start-addr}
32439 is the beginning address (or @code{$pc})
32440 @item @var{end-addr}
32442 @item @var{filename}
32443 is the name of the file to disassemble
32444 @item @var{linenum}
32445 is the line number to disassemble around
32447 is the number of disassembly lines to be produced. If it is -1,
32448 the whole function will be disassembled, in case no @var{end-addr} is
32449 specified. If @var{end-addr} is specified as a non-zero value, and
32450 @var{lines} is lower than the number of disassembly lines between
32451 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
32452 displayed; if @var{lines} is higher than the number of lines between
32453 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
32456 is either 0 (meaning only disassembly), 1 (meaning mixed source and
32457 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
32458 mixed source and disassembly with raw opcodes).
32461 @subsubheading Result
32463 The result of the @code{-data-disassemble} command will be a list named
32464 @samp{asm_insns}, the contents of this list depend on the @var{mode}
32465 used with the @code{-data-disassemble} command.
32467 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
32472 The address at which this instruction was disassembled.
32475 The name of the function this instruction is within.
32478 The decimal offset in bytes from the start of @samp{func-name}.
32481 The text disassembly for this @samp{address}.
32484 This field is only present for mode 2. This contains the raw opcode
32485 bytes for the @samp{inst} field.
32489 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
32490 @samp{src_and_asm_line}, each of which has the following fields:
32494 The line number within @samp{file}.
32497 The file name from the compilation unit. This might be an absolute
32498 file name or a relative file name depending on the compile command
32502 Absolute file name of @samp{file}. It is converted to a canonical form
32503 using the source file search path
32504 (@pxref{Source Path, ,Specifying Source Directories})
32505 and after resolving all the symbolic links.
32507 If the source file is not found this field will contain the path as
32508 present in the debug information.
32510 @item line_asm_insn
32511 This is a list of tuples containing the disassembly for @samp{line} in
32512 @samp{file}. The fields of each tuple are the same as for
32513 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
32514 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
32519 Note that whatever included in the @samp{inst} field, is not
32520 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
32523 @subsubheading @value{GDBN} Command
32525 The corresponding @value{GDBN} command is @samp{disassemble}.
32527 @subsubheading Example
32529 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
32533 -data-disassemble -s $pc -e "$pc + 20" -- 0
32536 @{address="0x000107c0",func-name="main",offset="4",
32537 inst="mov 2, %o0"@},
32538 @{address="0x000107c4",func-name="main",offset="8",
32539 inst="sethi %hi(0x11800), %o2"@},
32540 @{address="0x000107c8",func-name="main",offset="12",
32541 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
32542 @{address="0x000107cc",func-name="main",offset="16",
32543 inst="sethi %hi(0x11800), %o2"@},
32544 @{address="0x000107d0",func-name="main",offset="20",
32545 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
32549 Disassemble the whole @code{main} function. Line 32 is part of
32553 -data-disassemble -f basics.c -l 32 -- 0
32555 @{address="0x000107bc",func-name="main",offset="0",
32556 inst="save %sp, -112, %sp"@},
32557 @{address="0x000107c0",func-name="main",offset="4",
32558 inst="mov 2, %o0"@},
32559 @{address="0x000107c4",func-name="main",offset="8",
32560 inst="sethi %hi(0x11800), %o2"@},
32562 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
32563 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
32567 Disassemble 3 instructions from the start of @code{main}:
32571 -data-disassemble -f basics.c -l 32 -n 3 -- 0
32573 @{address="0x000107bc",func-name="main",offset="0",
32574 inst="save %sp, -112, %sp"@},
32575 @{address="0x000107c0",func-name="main",offset="4",
32576 inst="mov 2, %o0"@},
32577 @{address="0x000107c4",func-name="main",offset="8",
32578 inst="sethi %hi(0x11800), %o2"@}]
32582 Disassemble 3 instructions from the start of @code{main} in mixed mode:
32586 -data-disassemble -f basics.c -l 32 -n 3 -- 1
32588 src_and_asm_line=@{line="31",
32589 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32590 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32591 line_asm_insn=[@{address="0x000107bc",
32592 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
32593 src_and_asm_line=@{line="32",
32594 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
32595 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
32596 line_asm_insn=[@{address="0x000107c0",
32597 func-name="main",offset="4",inst="mov 2, %o0"@},
32598 @{address="0x000107c4",func-name="main",offset="8",
32599 inst="sethi %hi(0x11800), %o2"@}]@}]
32604 @subheading The @code{-data-evaluate-expression} Command
32605 @findex -data-evaluate-expression
32607 @subsubheading Synopsis
32610 -data-evaluate-expression @var{expr}
32613 Evaluate @var{expr} as an expression. The expression could contain an
32614 inferior function call. The function call will execute synchronously.
32615 If the expression contains spaces, it must be enclosed in double quotes.
32617 @subsubheading @value{GDBN} Command
32619 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
32620 @samp{call}. In @code{gdbtk} only, there's a corresponding
32621 @samp{gdb_eval} command.
32623 @subsubheading Example
32625 In the following example, the numbers that precede the commands are the
32626 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
32627 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
32631 211-data-evaluate-expression A
32634 311-data-evaluate-expression &A
32635 311^done,value="0xefffeb7c"
32637 411-data-evaluate-expression A+3
32640 511-data-evaluate-expression "A + 3"
32646 @subheading The @code{-data-list-changed-registers} Command
32647 @findex -data-list-changed-registers
32649 @subsubheading Synopsis
32652 -data-list-changed-registers
32655 Display a list of the registers that have changed.
32657 @subsubheading @value{GDBN} Command
32659 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
32660 has the corresponding command @samp{gdb_changed_register_list}.
32662 @subsubheading Example
32664 On a PPC MBX board:
32672 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
32673 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
32676 -data-list-changed-registers
32677 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
32678 "10","11","13","14","15","16","17","18","19","20","21","22","23",
32679 "24","25","26","27","28","30","31","64","65","66","67","69"]
32684 @subheading The @code{-data-list-register-names} Command
32685 @findex -data-list-register-names
32687 @subsubheading Synopsis
32690 -data-list-register-names [ ( @var{regno} )+ ]
32693 Show a list of register names for the current target. If no arguments
32694 are given, it shows a list of the names of all the registers. If
32695 integer numbers are given as arguments, it will print a list of the
32696 names of the registers corresponding to the arguments. To ensure
32697 consistency between a register name and its number, the output list may
32698 include empty register names.
32700 @subsubheading @value{GDBN} Command
32702 @value{GDBN} does not have a command which corresponds to
32703 @samp{-data-list-register-names}. In @code{gdbtk} there is a
32704 corresponding command @samp{gdb_regnames}.
32706 @subsubheading Example
32708 For the PPC MBX board:
32711 -data-list-register-names
32712 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
32713 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
32714 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
32715 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
32716 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
32717 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
32718 "", "pc","ps","cr","lr","ctr","xer"]
32720 -data-list-register-names 1 2 3
32721 ^done,register-names=["r1","r2","r3"]
32725 @subheading The @code{-data-list-register-values} Command
32726 @findex -data-list-register-values
32728 @subsubheading Synopsis
32731 -data-list-register-values
32732 [ @code{--skip-unavailable} ] @var{fmt} [ ( @var{regno} )*]
32735 Display the registers' contents. @var{fmt} is the format according to
32736 which the registers' contents are to be returned, followed by an optional
32737 list of numbers specifying the registers to display. A missing list of
32738 numbers indicates that the contents of all the registers must be
32739 returned. The @code{--skip-unavailable} option indicates that only
32740 the available registers are to be returned.
32742 Allowed formats for @var{fmt} are:
32759 @subsubheading @value{GDBN} Command
32761 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
32762 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
32764 @subsubheading Example
32766 For a PPC MBX board (note: line breaks are for readability only, they
32767 don't appear in the actual output):
32771 -data-list-register-values r 64 65
32772 ^done,register-values=[@{number="64",value="0xfe00a300"@},
32773 @{number="65",value="0x00029002"@}]
32775 -data-list-register-values x
32776 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
32777 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
32778 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
32779 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
32780 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
32781 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
32782 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
32783 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
32784 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
32785 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
32786 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
32787 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
32788 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
32789 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
32790 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
32791 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
32792 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
32793 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
32794 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
32795 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
32796 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
32797 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
32798 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
32799 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
32800 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
32801 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
32802 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
32803 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
32804 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
32805 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
32806 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
32807 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
32808 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
32809 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
32810 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
32811 @{number="69",value="0x20002b03"@}]
32816 @subheading The @code{-data-read-memory} Command
32817 @findex -data-read-memory
32819 This command is deprecated, use @code{-data-read-memory-bytes} instead.
32821 @subsubheading Synopsis
32824 -data-read-memory [ -o @var{byte-offset} ]
32825 @var{address} @var{word-format} @var{word-size}
32826 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
32833 @item @var{address}
32834 An expression specifying the address of the first memory word to be
32835 read. Complex expressions containing embedded white space should be
32836 quoted using the C convention.
32838 @item @var{word-format}
32839 The format to be used to print the memory words. The notation is the
32840 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
32843 @item @var{word-size}
32844 The size of each memory word in bytes.
32846 @item @var{nr-rows}
32847 The number of rows in the output table.
32849 @item @var{nr-cols}
32850 The number of columns in the output table.
32853 If present, indicates that each row should include an @sc{ascii} dump. The
32854 value of @var{aschar} is used as a padding character when a byte is not a
32855 member of the printable @sc{ascii} character set (printable @sc{ascii}
32856 characters are those whose code is between 32 and 126, inclusively).
32858 @item @var{byte-offset}
32859 An offset to add to the @var{address} before fetching memory.
32862 This command displays memory contents as a table of @var{nr-rows} by
32863 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
32864 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
32865 (returned as @samp{total-bytes}). Should less than the requested number
32866 of bytes be returned by the target, the missing words are identified
32867 using @samp{N/A}. The number of bytes read from the target is returned
32868 in @samp{nr-bytes} and the starting address used to read memory in
32871 The address of the next/previous row or page is available in
32872 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
32875 @subsubheading @value{GDBN} Command
32877 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
32878 @samp{gdb_get_mem} memory read command.
32880 @subsubheading Example
32882 Read six bytes of memory starting at @code{bytes+6} but then offset by
32883 @code{-6} bytes. Format as three rows of two columns. One byte per
32884 word. Display each word in hex.
32888 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
32889 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
32890 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
32891 prev-page="0x0000138a",memory=[
32892 @{addr="0x00001390",data=["0x00","0x01"]@},
32893 @{addr="0x00001392",data=["0x02","0x03"]@},
32894 @{addr="0x00001394",data=["0x04","0x05"]@}]
32898 Read two bytes of memory starting at address @code{shorts + 64} and
32899 display as a single word formatted in decimal.
32903 5-data-read-memory shorts+64 d 2 1 1
32904 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
32905 next-row="0x00001512",prev-row="0x0000150e",
32906 next-page="0x00001512",prev-page="0x0000150e",memory=[
32907 @{addr="0x00001510",data=["128"]@}]
32911 Read thirty two bytes of memory starting at @code{bytes+16} and format
32912 as eight rows of four columns. Include a string encoding with @samp{x}
32913 used as the non-printable character.
32917 4-data-read-memory bytes+16 x 1 8 4 x
32918 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
32919 next-row="0x000013c0",prev-row="0x0000139c",
32920 next-page="0x000013c0",prev-page="0x00001380",memory=[
32921 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
32922 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
32923 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
32924 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
32925 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
32926 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
32927 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
32928 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
32932 @subheading The @code{-data-read-memory-bytes} Command
32933 @findex -data-read-memory-bytes
32935 @subsubheading Synopsis
32938 -data-read-memory-bytes [ -o @var{byte-offset} ]
32939 @var{address} @var{count}
32946 @item @var{address}
32947 An expression specifying the address of the first memory word to be
32948 read. Complex expressions containing embedded white space should be
32949 quoted using the C convention.
32952 The number of bytes to read. This should be an integer literal.
32954 @item @var{byte-offset}
32955 The offsets in bytes relative to @var{address} at which to start
32956 reading. This should be an integer literal. This option is provided
32957 so that a frontend is not required to first evaluate address and then
32958 perform address arithmetics itself.
32962 This command attempts to read all accessible memory regions in the
32963 specified range. First, all regions marked as unreadable in the memory
32964 map (if one is defined) will be skipped. @xref{Memory Region
32965 Attributes}. Second, @value{GDBN} will attempt to read the remaining
32966 regions. For each one, if reading full region results in an errors,
32967 @value{GDBN} will try to read a subset of the region.
32969 In general, every single byte in the region may be readable or not,
32970 and the only way to read every readable byte is to try a read at
32971 every address, which is not practical. Therefore, @value{GDBN} will
32972 attempt to read all accessible bytes at either beginning or the end
32973 of the region, using a binary division scheme. This heuristic works
32974 well for reading accross a memory map boundary. Note that if a region
32975 has a readable range that is neither at the beginning or the end,
32976 @value{GDBN} will not read it.
32978 The result record (@pxref{GDB/MI Result Records}) that is output of
32979 the command includes a field named @samp{memory} whose content is a
32980 list of tuples. Each tuple represent a successfully read memory block
32981 and has the following fields:
32985 The start address of the memory block, as hexadecimal literal.
32988 The end address of the memory block, as hexadecimal literal.
32991 The offset of the memory block, as hexadecimal literal, relative to
32992 the start address passed to @code{-data-read-memory-bytes}.
32995 The contents of the memory block, in hex.
33001 @subsubheading @value{GDBN} Command
33003 The corresponding @value{GDBN} command is @samp{x}.
33005 @subsubheading Example
33009 -data-read-memory-bytes &a 10
33010 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
33012 contents="01000000020000000300"@}]
33017 @subheading The @code{-data-write-memory-bytes} Command
33018 @findex -data-write-memory-bytes
33020 @subsubheading Synopsis
33023 -data-write-memory-bytes @var{address} @var{contents}
33024 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
33031 @item @var{address}
33032 An expression specifying the address of the first memory word to be
33033 read. Complex expressions containing embedded white space should be
33034 quoted using the C convention.
33036 @item @var{contents}
33037 The hex-encoded bytes to write.
33040 Optional argument indicating the number of bytes to be written. If @var{count}
33041 is greater than @var{contents}' length, @value{GDBN} will repeatedly
33042 write @var{contents} until it fills @var{count} bytes.
33046 @subsubheading @value{GDBN} Command
33048 There's no corresponding @value{GDBN} command.
33050 @subsubheading Example
33054 -data-write-memory-bytes &a "aabbccdd"
33061 -data-write-memory-bytes &a "aabbccdd" 16e
33066 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33067 @node GDB/MI Tracepoint Commands
33068 @section @sc{gdb/mi} Tracepoint Commands
33070 The commands defined in this section implement MI support for
33071 tracepoints. For detailed introduction, see @ref{Tracepoints}.
33073 @subheading The @code{-trace-find} Command
33074 @findex -trace-find
33076 @subsubheading Synopsis
33079 -trace-find @var{mode} [@var{parameters}@dots{}]
33082 Find a trace frame using criteria defined by @var{mode} and
33083 @var{parameters}. The following table lists permissible
33084 modes and their parameters. For details of operation, see @ref{tfind}.
33089 No parameters are required. Stops examining trace frames.
33092 An integer is required as parameter. Selects tracepoint frame with
33095 @item tracepoint-number
33096 An integer is required as parameter. Finds next
33097 trace frame that corresponds to tracepoint with the specified number.
33100 An address is required as parameter. Finds
33101 next trace frame that corresponds to any tracepoint at the specified
33104 @item pc-inside-range
33105 Two addresses are required as parameters. Finds next trace
33106 frame that corresponds to a tracepoint at an address inside the
33107 specified range. Both bounds are considered to be inside the range.
33109 @item pc-outside-range
33110 Two addresses are required as parameters. Finds
33111 next trace frame that corresponds to a tracepoint at an address outside
33112 the specified range. Both bounds are considered to be inside the range.
33115 Line specification is required as parameter. @xref{Specify Location}.
33116 Finds next trace frame that corresponds to a tracepoint at
33117 the specified location.
33121 If @samp{none} was passed as @var{mode}, the response does not
33122 have fields. Otherwise, the response may have the following fields:
33126 This field has either @samp{0} or @samp{1} as the value, depending
33127 on whether a matching tracepoint was found.
33130 The index of the found traceframe. This field is present iff
33131 the @samp{found} field has value of @samp{1}.
33134 The index of the found tracepoint. This field is present iff
33135 the @samp{found} field has value of @samp{1}.
33138 The information about the frame corresponding to the found trace
33139 frame. This field is present only if a trace frame was found.
33140 @xref{GDB/MI Frame Information}, for description of this field.
33144 @subsubheading @value{GDBN} Command
33146 The corresponding @value{GDBN} command is @samp{tfind}.
33148 @subheading -trace-define-variable
33149 @findex -trace-define-variable
33151 @subsubheading Synopsis
33154 -trace-define-variable @var{name} [ @var{value} ]
33157 Create trace variable @var{name} if it does not exist. If
33158 @var{value} is specified, sets the initial value of the specified
33159 trace variable to that value. Note that the @var{name} should start
33160 with the @samp{$} character.
33162 @subsubheading @value{GDBN} Command
33164 The corresponding @value{GDBN} command is @samp{tvariable}.
33166 @subheading The @code{-trace-frame-collected} Command
33167 @findex -trace-frame-collected
33169 @subsubheading Synopsis
33172 -trace-frame-collected
33173 [--var-print-values @var{var_pval}]
33174 [--comp-print-values @var{comp_pval}]
33175 [--registers-format @var{regformat}]
33176 [--memory-contents]
33179 This command returns the set of collected objects, register names,
33180 trace state variable names, memory ranges and computed expressions
33181 that have been collected at a particular trace frame. The optional
33182 parameters to the command affect the output format in different ways.
33183 See the output description table below for more details.
33185 The reported names can be used in the normal manner to create
33186 varobjs and inspect the objects themselves. The items returned by
33187 this command are categorized so that it is clear which is a variable,
33188 which is a register, which is a trace state variable, which is a
33189 memory range and which is a computed expression.
33191 For instance, if the actions were
33193 collect myVar, myArray[myIndex], myObj.field, myPtr->field, myCount + 2
33194 collect *(int*)0xaf02bef0@@40
33198 the object collected in its entirety would be @code{myVar}. The
33199 object @code{myArray} would be partially collected, because only the
33200 element at index @code{myIndex} would be collected. The remaining
33201 objects would be computed expressions.
33203 An example output would be:
33207 -trace-frame-collected
33209 explicit-variables=[@{name="myVar",value="1"@}],
33210 computed-expressions=[@{name="myArray[myIndex]",value="0"@},
33211 @{name="myObj.field",value="0"@},
33212 @{name="myPtr->field",value="1"@},
33213 @{name="myCount + 2",value="3"@},
33214 @{name="$tvar1 + 1",value="43970027"@}],
33215 registers=[@{number="0",value="0x7fe2c6e79ec8"@},
33216 @{number="1",value="0x0"@},
33217 @{number="2",value="0x4"@},
33219 @{number="125",value="0x0"@}],
33220 tvars=[@{name="$tvar1",current="43970026"@}],
33221 memory=[@{address="0x0000000000602264",length="4"@},
33222 @{address="0x0000000000615bc0",length="4"@}]
33229 @item explicit-variables
33230 The set of objects that have been collected in their entirety (as
33231 opposed to collecting just a few elements of an array or a few struct
33232 members). For each object, its name and value are printed.
33233 The @code{--var-print-values} option affects how or whether the value
33234 field is output. If @var{var_pval} is 0, then print only the names;
33235 if it is 1, print also their values; and if it is 2, print the name,
33236 type and value for simple data types, and the name and type for
33237 arrays, structures and unions.
33239 @item computed-expressions
33240 The set of computed expressions that have been collected at the
33241 current trace frame. The @code{--comp-print-values} option affects
33242 this set like the @code{--var-print-values} option affects the
33243 @code{explicit-variables} set. See above.
33246 The registers that have been collected at the current trace frame.
33247 For each register collected, the name and current value are returned.
33248 The value is formatted according to the @code{--registers-format}
33249 option. See the @command{-data-list-register-values} command for a
33250 list of the allowed formats. The default is @samp{x}.
33253 The trace state variables that have been collected at the current
33254 trace frame. For each trace state variable collected, the name and
33255 current value are returned.
33258 The set of memory ranges that have been collected at the current trace
33259 frame. Its content is a list of tuples. Each tuple represents a
33260 collected memory range and has the following fields:
33264 The start address of the memory range, as hexadecimal literal.
33267 The length of the memory range, as decimal literal.
33270 The contents of the memory block, in hex. This field is only present
33271 if the @code{--memory-contents} option is specified.
33277 @subsubheading @value{GDBN} Command
33279 There is no corresponding @value{GDBN} command.
33281 @subsubheading Example
33283 @subheading -trace-list-variables
33284 @findex -trace-list-variables
33286 @subsubheading Synopsis
33289 -trace-list-variables
33292 Return a table of all defined trace variables. Each element of the
33293 table has the following fields:
33297 The name of the trace variable. This field is always present.
33300 The initial value. This is a 64-bit signed integer. This
33301 field is always present.
33304 The value the trace variable has at the moment. This is a 64-bit
33305 signed integer. This field is absent iff current value is
33306 not defined, for example if the trace was never run, or is
33311 @subsubheading @value{GDBN} Command
33313 The corresponding @value{GDBN} command is @samp{tvariables}.
33315 @subsubheading Example
33319 -trace-list-variables
33320 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
33321 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
33322 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
33323 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
33324 body=[variable=@{name="$trace_timestamp",initial="0"@}
33325 variable=@{name="$foo",initial="10",current="15"@}]@}
33329 @subheading -trace-save
33330 @findex -trace-save
33332 @subsubheading Synopsis
33335 -trace-save [-r ] @var{filename}
33338 Saves the collected trace data to @var{filename}. Without the
33339 @samp{-r} option, the data is downloaded from the target and saved
33340 in a local file. With the @samp{-r} option the target is asked
33341 to perform the save.
33343 @subsubheading @value{GDBN} Command
33345 The corresponding @value{GDBN} command is @samp{tsave}.
33348 @subheading -trace-start
33349 @findex -trace-start
33351 @subsubheading Synopsis
33357 Starts a tracing experiments. The result of this command does not
33360 @subsubheading @value{GDBN} Command
33362 The corresponding @value{GDBN} command is @samp{tstart}.
33364 @subheading -trace-status
33365 @findex -trace-status
33367 @subsubheading Synopsis
33373 Obtains the status of a tracing experiment. The result may include
33374 the following fields:
33379 May have a value of either @samp{0}, when no tracing operations are
33380 supported, @samp{1}, when all tracing operations are supported, or
33381 @samp{file} when examining trace file. In the latter case, examining
33382 of trace frame is possible but new tracing experiement cannot be
33383 started. This field is always present.
33386 May have a value of either @samp{0} or @samp{1} depending on whether
33387 tracing experiement is in progress on target. This field is present
33388 if @samp{supported} field is not @samp{0}.
33391 Report the reason why the tracing was stopped last time. This field
33392 may be absent iff tracing was never stopped on target yet. The
33393 value of @samp{request} means the tracing was stopped as result of
33394 the @code{-trace-stop} command. The value of @samp{overflow} means
33395 the tracing buffer is full. The value of @samp{disconnection} means
33396 tracing was automatically stopped when @value{GDBN} has disconnected.
33397 The value of @samp{passcount} means tracing was stopped when a
33398 tracepoint was passed a maximal number of times for that tracepoint.
33399 This field is present if @samp{supported} field is not @samp{0}.
33401 @item stopping-tracepoint
33402 The number of tracepoint whose passcount as exceeded. This field is
33403 present iff the @samp{stop-reason} field has the value of
33407 @itemx frames-created
33408 The @samp{frames} field is a count of the total number of trace frames
33409 in the trace buffer, while @samp{frames-created} is the total created
33410 during the run, including ones that were discarded, such as when a
33411 circular trace buffer filled up. Both fields are optional.
33415 These fields tell the current size of the tracing buffer and the
33416 remaining space. These fields are optional.
33419 The value of the circular trace buffer flag. @code{1} means that the
33420 trace buffer is circular and old trace frames will be discarded if
33421 necessary to make room, @code{0} means that the trace buffer is linear
33425 The value of the disconnected tracing flag. @code{1} means that
33426 tracing will continue after @value{GDBN} disconnects, @code{0} means
33427 that the trace run will stop.
33430 The filename of the trace file being examined. This field is
33431 optional, and only present when examining a trace file.
33435 @subsubheading @value{GDBN} Command
33437 The corresponding @value{GDBN} command is @samp{tstatus}.
33439 @subheading -trace-stop
33440 @findex -trace-stop
33442 @subsubheading Synopsis
33448 Stops a tracing experiment. The result of this command has the same
33449 fields as @code{-trace-status}, except that the @samp{supported} and
33450 @samp{running} fields are not output.
33452 @subsubheading @value{GDBN} Command
33454 The corresponding @value{GDBN} command is @samp{tstop}.
33457 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33458 @node GDB/MI Symbol Query
33459 @section @sc{gdb/mi} Symbol Query Commands
33463 @subheading The @code{-symbol-info-address} Command
33464 @findex -symbol-info-address
33466 @subsubheading Synopsis
33469 -symbol-info-address @var{symbol}
33472 Describe where @var{symbol} is stored.
33474 @subsubheading @value{GDBN} Command
33476 The corresponding @value{GDBN} command is @samp{info address}.
33478 @subsubheading Example
33482 @subheading The @code{-symbol-info-file} Command
33483 @findex -symbol-info-file
33485 @subsubheading Synopsis
33491 Show the file for the symbol.
33493 @subsubheading @value{GDBN} Command
33495 There's no equivalent @value{GDBN} command. @code{gdbtk} has
33496 @samp{gdb_find_file}.
33498 @subsubheading Example
33502 @subheading The @code{-symbol-info-function} Command
33503 @findex -symbol-info-function
33505 @subsubheading Synopsis
33508 -symbol-info-function
33511 Show which function the symbol lives in.
33513 @subsubheading @value{GDBN} Command
33515 @samp{gdb_get_function} in @code{gdbtk}.
33517 @subsubheading Example
33521 @subheading The @code{-symbol-info-line} Command
33522 @findex -symbol-info-line
33524 @subsubheading Synopsis
33530 Show the core addresses of the code for a source line.
33532 @subsubheading @value{GDBN} Command
33534 The corresponding @value{GDBN} command is @samp{info line}.
33535 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
33537 @subsubheading Example
33541 @subheading The @code{-symbol-info-symbol} Command
33542 @findex -symbol-info-symbol
33544 @subsubheading Synopsis
33547 -symbol-info-symbol @var{addr}
33550 Describe what symbol is at location @var{addr}.
33552 @subsubheading @value{GDBN} Command
33554 The corresponding @value{GDBN} command is @samp{info symbol}.
33556 @subsubheading Example
33560 @subheading The @code{-symbol-list-functions} Command
33561 @findex -symbol-list-functions
33563 @subsubheading Synopsis
33566 -symbol-list-functions
33569 List the functions in the executable.
33571 @subsubheading @value{GDBN} Command
33573 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
33574 @samp{gdb_search} in @code{gdbtk}.
33576 @subsubheading Example
33581 @subheading The @code{-symbol-list-lines} Command
33582 @findex -symbol-list-lines
33584 @subsubheading Synopsis
33587 -symbol-list-lines @var{filename}
33590 Print the list of lines that contain code and their associated program
33591 addresses for the given source filename. The entries are sorted in
33592 ascending PC order.
33594 @subsubheading @value{GDBN} Command
33596 There is no corresponding @value{GDBN} command.
33598 @subsubheading Example
33601 -symbol-list-lines basics.c
33602 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
33608 @subheading The @code{-symbol-list-types} Command
33609 @findex -symbol-list-types
33611 @subsubheading Synopsis
33617 List all the type names.
33619 @subsubheading @value{GDBN} Command
33621 The corresponding commands are @samp{info types} in @value{GDBN},
33622 @samp{gdb_search} in @code{gdbtk}.
33624 @subsubheading Example
33628 @subheading The @code{-symbol-list-variables} Command
33629 @findex -symbol-list-variables
33631 @subsubheading Synopsis
33634 -symbol-list-variables
33637 List all the global and static variable names.
33639 @subsubheading @value{GDBN} Command
33641 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
33643 @subsubheading Example
33647 @subheading The @code{-symbol-locate} Command
33648 @findex -symbol-locate
33650 @subsubheading Synopsis
33656 @subsubheading @value{GDBN} Command
33658 @samp{gdb_loc} in @code{gdbtk}.
33660 @subsubheading Example
33664 @subheading The @code{-symbol-type} Command
33665 @findex -symbol-type
33667 @subsubheading Synopsis
33670 -symbol-type @var{variable}
33673 Show type of @var{variable}.
33675 @subsubheading @value{GDBN} Command
33677 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
33678 @samp{gdb_obj_variable}.
33680 @subsubheading Example
33685 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33686 @node GDB/MI File Commands
33687 @section @sc{gdb/mi} File Commands
33689 This section describes the GDB/MI commands to specify executable file names
33690 and to read in and obtain symbol table information.
33692 @subheading The @code{-file-exec-and-symbols} Command
33693 @findex -file-exec-and-symbols
33695 @subsubheading Synopsis
33698 -file-exec-and-symbols @var{file}
33701 Specify the executable file to be debugged. This file is the one from
33702 which the symbol table is also read. If no file is specified, the
33703 command clears the executable and symbol information. If breakpoints
33704 are set when using this command with no arguments, @value{GDBN} will produce
33705 error messages. Otherwise, no output is produced, except a completion
33708 @subsubheading @value{GDBN} Command
33710 The corresponding @value{GDBN} command is @samp{file}.
33712 @subsubheading Example
33716 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33722 @subheading The @code{-file-exec-file} Command
33723 @findex -file-exec-file
33725 @subsubheading Synopsis
33728 -file-exec-file @var{file}
33731 Specify the executable file to be debugged. Unlike
33732 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
33733 from this file. If used without argument, @value{GDBN} clears the information
33734 about the executable file. No output is produced, except a completion
33737 @subsubheading @value{GDBN} Command
33739 The corresponding @value{GDBN} command is @samp{exec-file}.
33741 @subsubheading Example
33745 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33752 @subheading The @code{-file-list-exec-sections} Command
33753 @findex -file-list-exec-sections
33755 @subsubheading Synopsis
33758 -file-list-exec-sections
33761 List the sections of the current executable file.
33763 @subsubheading @value{GDBN} Command
33765 The @value{GDBN} command @samp{info file} shows, among the rest, the same
33766 information as this command. @code{gdbtk} has a corresponding command
33767 @samp{gdb_load_info}.
33769 @subsubheading Example
33774 @subheading The @code{-file-list-exec-source-file} Command
33775 @findex -file-list-exec-source-file
33777 @subsubheading Synopsis
33780 -file-list-exec-source-file
33783 List the line number, the current source file, and the absolute path
33784 to the current source file for the current executable. The macro
33785 information field has a value of @samp{1} or @samp{0} depending on
33786 whether or not the file includes preprocessor macro information.
33788 @subsubheading @value{GDBN} Command
33790 The @value{GDBN} equivalent is @samp{info source}
33792 @subsubheading Example
33796 123-file-list-exec-source-file
33797 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
33802 @subheading The @code{-file-list-exec-source-files} Command
33803 @findex -file-list-exec-source-files
33805 @subsubheading Synopsis
33808 -file-list-exec-source-files
33811 List the source files for the current executable.
33813 It will always output both the filename and fullname (absolute file
33814 name) of a source file.
33816 @subsubheading @value{GDBN} Command
33818 The @value{GDBN} equivalent is @samp{info sources}.
33819 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
33821 @subsubheading Example
33824 -file-list-exec-source-files
33826 @{file=foo.c,fullname=/home/foo.c@},
33827 @{file=/home/bar.c,fullname=/home/bar.c@},
33828 @{file=gdb_could_not_find_fullpath.c@}]
33833 @subheading The @code{-file-list-shared-libraries} Command
33834 @findex -file-list-shared-libraries
33836 @subsubheading Synopsis
33839 -file-list-shared-libraries
33842 List the shared libraries in the program.
33844 @subsubheading @value{GDBN} Command
33846 The corresponding @value{GDBN} command is @samp{info shared}.
33848 @subsubheading Example
33852 @subheading The @code{-file-list-symbol-files} Command
33853 @findex -file-list-symbol-files
33855 @subsubheading Synopsis
33858 -file-list-symbol-files
33863 @subsubheading @value{GDBN} Command
33865 The corresponding @value{GDBN} command is @samp{info file} (part of it).
33867 @subsubheading Example
33872 @subheading The @code{-file-symbol-file} Command
33873 @findex -file-symbol-file
33875 @subsubheading Synopsis
33878 -file-symbol-file @var{file}
33881 Read symbol table info from the specified @var{file} argument. When
33882 used without arguments, clears @value{GDBN}'s symbol table info. No output is
33883 produced, except for a completion notification.
33885 @subsubheading @value{GDBN} Command
33887 The corresponding @value{GDBN} command is @samp{symbol-file}.
33889 @subsubheading Example
33893 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
33899 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33900 @node GDB/MI Memory Overlay Commands
33901 @section @sc{gdb/mi} Memory Overlay Commands
33903 The memory overlay commands are not implemented.
33905 @c @subheading -overlay-auto
33907 @c @subheading -overlay-list-mapping-state
33909 @c @subheading -overlay-list-overlays
33911 @c @subheading -overlay-map
33913 @c @subheading -overlay-off
33915 @c @subheading -overlay-on
33917 @c @subheading -overlay-unmap
33919 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33920 @node GDB/MI Signal Handling Commands
33921 @section @sc{gdb/mi} Signal Handling Commands
33923 Signal handling commands are not implemented.
33925 @c @subheading -signal-handle
33927 @c @subheading -signal-list-handle-actions
33929 @c @subheading -signal-list-signal-types
33933 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33934 @node GDB/MI Target Manipulation
33935 @section @sc{gdb/mi} Target Manipulation Commands
33938 @subheading The @code{-target-attach} Command
33939 @findex -target-attach
33941 @subsubheading Synopsis
33944 -target-attach @var{pid} | @var{gid} | @var{file}
33947 Attach to a process @var{pid} or a file @var{file} outside of
33948 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
33949 group, the id previously returned by
33950 @samp{-list-thread-groups --available} must be used.
33952 @subsubheading @value{GDBN} Command
33954 The corresponding @value{GDBN} command is @samp{attach}.
33956 @subsubheading Example
33960 =thread-created,id="1"
33961 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
33967 @subheading The @code{-target-compare-sections} Command
33968 @findex -target-compare-sections
33970 @subsubheading Synopsis
33973 -target-compare-sections [ @var{section} ]
33976 Compare data of section @var{section} on target to the exec file.
33977 Without the argument, all sections are compared.
33979 @subsubheading @value{GDBN} Command
33981 The @value{GDBN} equivalent is @samp{compare-sections}.
33983 @subsubheading Example
33988 @subheading The @code{-target-detach} Command
33989 @findex -target-detach
33991 @subsubheading Synopsis
33994 -target-detach [ @var{pid} | @var{gid} ]
33997 Detach from the remote target which normally resumes its execution.
33998 If either @var{pid} or @var{gid} is specified, detaches from either
33999 the specified process, or specified thread group. There's no output.
34001 @subsubheading @value{GDBN} Command
34003 The corresponding @value{GDBN} command is @samp{detach}.
34005 @subsubheading Example
34015 @subheading The @code{-target-disconnect} Command
34016 @findex -target-disconnect
34018 @subsubheading Synopsis
34024 Disconnect from the remote target. There's no output and the target is
34025 generally not resumed.
34027 @subsubheading @value{GDBN} Command
34029 The corresponding @value{GDBN} command is @samp{disconnect}.
34031 @subsubheading Example
34041 @subheading The @code{-target-download} Command
34042 @findex -target-download
34044 @subsubheading Synopsis
34050 Loads the executable onto the remote target.
34051 It prints out an update message every half second, which includes the fields:
34055 The name of the section.
34057 The size of what has been sent so far for that section.
34059 The size of the section.
34061 The total size of what was sent so far (the current and the previous sections).
34063 The size of the overall executable to download.
34067 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
34068 @sc{gdb/mi} Output Syntax}).
34070 In addition, it prints the name and size of the sections, as they are
34071 downloaded. These messages include the following fields:
34075 The name of the section.
34077 The size of the section.
34079 The size of the overall executable to download.
34083 At the end, a summary is printed.
34085 @subsubheading @value{GDBN} Command
34087 The corresponding @value{GDBN} command is @samp{load}.
34089 @subsubheading Example
34091 Note: each status message appears on a single line. Here the messages
34092 have been broken down so that they can fit onto a page.
34097 +download,@{section=".text",section-size="6668",total-size="9880"@}
34098 +download,@{section=".text",section-sent="512",section-size="6668",
34099 total-sent="512",total-size="9880"@}
34100 +download,@{section=".text",section-sent="1024",section-size="6668",
34101 total-sent="1024",total-size="9880"@}
34102 +download,@{section=".text",section-sent="1536",section-size="6668",
34103 total-sent="1536",total-size="9880"@}
34104 +download,@{section=".text",section-sent="2048",section-size="6668",
34105 total-sent="2048",total-size="9880"@}
34106 +download,@{section=".text",section-sent="2560",section-size="6668",
34107 total-sent="2560",total-size="9880"@}
34108 +download,@{section=".text",section-sent="3072",section-size="6668",
34109 total-sent="3072",total-size="9880"@}
34110 +download,@{section=".text",section-sent="3584",section-size="6668",
34111 total-sent="3584",total-size="9880"@}
34112 +download,@{section=".text",section-sent="4096",section-size="6668",
34113 total-sent="4096",total-size="9880"@}
34114 +download,@{section=".text",section-sent="4608",section-size="6668",
34115 total-sent="4608",total-size="9880"@}
34116 +download,@{section=".text",section-sent="5120",section-size="6668",
34117 total-sent="5120",total-size="9880"@}
34118 +download,@{section=".text",section-sent="5632",section-size="6668",
34119 total-sent="5632",total-size="9880"@}
34120 +download,@{section=".text",section-sent="6144",section-size="6668",
34121 total-sent="6144",total-size="9880"@}
34122 +download,@{section=".text",section-sent="6656",section-size="6668",
34123 total-sent="6656",total-size="9880"@}
34124 +download,@{section=".init",section-size="28",total-size="9880"@}
34125 +download,@{section=".fini",section-size="28",total-size="9880"@}
34126 +download,@{section=".data",section-size="3156",total-size="9880"@}
34127 +download,@{section=".data",section-sent="512",section-size="3156",
34128 total-sent="7236",total-size="9880"@}
34129 +download,@{section=".data",section-sent="1024",section-size="3156",
34130 total-sent="7748",total-size="9880"@}
34131 +download,@{section=".data",section-sent="1536",section-size="3156",
34132 total-sent="8260",total-size="9880"@}
34133 +download,@{section=".data",section-sent="2048",section-size="3156",
34134 total-sent="8772",total-size="9880"@}
34135 +download,@{section=".data",section-sent="2560",section-size="3156",
34136 total-sent="9284",total-size="9880"@}
34137 +download,@{section=".data",section-sent="3072",section-size="3156",
34138 total-sent="9796",total-size="9880"@}
34139 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
34146 @subheading The @code{-target-exec-status} Command
34147 @findex -target-exec-status
34149 @subsubheading Synopsis
34152 -target-exec-status
34155 Provide information on the state of the target (whether it is running or
34156 not, for instance).
34158 @subsubheading @value{GDBN} Command
34160 There's no equivalent @value{GDBN} command.
34162 @subsubheading Example
34166 @subheading The @code{-target-list-available-targets} Command
34167 @findex -target-list-available-targets
34169 @subsubheading Synopsis
34172 -target-list-available-targets
34175 List the possible targets to connect to.
34177 @subsubheading @value{GDBN} Command
34179 The corresponding @value{GDBN} command is @samp{help target}.
34181 @subsubheading Example
34185 @subheading The @code{-target-list-current-targets} Command
34186 @findex -target-list-current-targets
34188 @subsubheading Synopsis
34191 -target-list-current-targets
34194 Describe the current target.
34196 @subsubheading @value{GDBN} Command
34198 The corresponding information is printed by @samp{info file} (among
34201 @subsubheading Example
34205 @subheading The @code{-target-list-parameters} Command
34206 @findex -target-list-parameters
34208 @subsubheading Synopsis
34211 -target-list-parameters
34217 @subsubheading @value{GDBN} Command
34221 @subsubheading Example
34225 @subheading The @code{-target-select} Command
34226 @findex -target-select
34228 @subsubheading Synopsis
34231 -target-select @var{type} @var{parameters @dots{}}
34234 Connect @value{GDBN} to the remote target. This command takes two args:
34238 The type of target, for instance @samp{remote}, etc.
34239 @item @var{parameters}
34240 Device names, host names and the like. @xref{Target Commands, ,
34241 Commands for Managing Targets}, for more details.
34244 The output is a connection notification, followed by the address at
34245 which the target program is, in the following form:
34248 ^connected,addr="@var{address}",func="@var{function name}",
34249 args=[@var{arg list}]
34252 @subsubheading @value{GDBN} Command
34254 The corresponding @value{GDBN} command is @samp{target}.
34256 @subsubheading Example
34260 -target-select remote /dev/ttya
34261 ^connected,addr="0xfe00a300",func="??",args=[]
34265 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34266 @node GDB/MI File Transfer Commands
34267 @section @sc{gdb/mi} File Transfer Commands
34270 @subheading The @code{-target-file-put} Command
34271 @findex -target-file-put
34273 @subsubheading Synopsis
34276 -target-file-put @var{hostfile} @var{targetfile}
34279 Copy file @var{hostfile} from the host system (the machine running
34280 @value{GDBN}) to @var{targetfile} on the target system.
34282 @subsubheading @value{GDBN} Command
34284 The corresponding @value{GDBN} command is @samp{remote put}.
34286 @subsubheading Example
34290 -target-file-put localfile remotefile
34296 @subheading The @code{-target-file-get} Command
34297 @findex -target-file-get
34299 @subsubheading Synopsis
34302 -target-file-get @var{targetfile} @var{hostfile}
34305 Copy file @var{targetfile} from the target system to @var{hostfile}
34306 on the host system.
34308 @subsubheading @value{GDBN} Command
34310 The corresponding @value{GDBN} command is @samp{remote get}.
34312 @subsubheading Example
34316 -target-file-get remotefile localfile
34322 @subheading The @code{-target-file-delete} Command
34323 @findex -target-file-delete
34325 @subsubheading Synopsis
34328 -target-file-delete @var{targetfile}
34331 Delete @var{targetfile} from the target system.
34333 @subsubheading @value{GDBN} Command
34335 The corresponding @value{GDBN} command is @samp{remote delete}.
34337 @subsubheading Example
34341 -target-file-delete remotefile
34347 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
34348 @node GDB/MI Miscellaneous Commands
34349 @section Miscellaneous @sc{gdb/mi} Commands
34351 @c @subheading -gdb-complete
34353 @subheading The @code{-gdb-exit} Command
34356 @subsubheading Synopsis
34362 Exit @value{GDBN} immediately.
34364 @subsubheading @value{GDBN} Command
34366 Approximately corresponds to @samp{quit}.
34368 @subsubheading Example
34378 @subheading The @code{-exec-abort} Command
34379 @findex -exec-abort
34381 @subsubheading Synopsis
34387 Kill the inferior running program.
34389 @subsubheading @value{GDBN} Command
34391 The corresponding @value{GDBN} command is @samp{kill}.
34393 @subsubheading Example
34398 @subheading The @code{-gdb-set} Command
34401 @subsubheading Synopsis
34407 Set an internal @value{GDBN} variable.
34408 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
34410 @subsubheading @value{GDBN} Command
34412 The corresponding @value{GDBN} command is @samp{set}.
34414 @subsubheading Example
34424 @subheading The @code{-gdb-show} Command
34427 @subsubheading Synopsis
34433 Show the current value of a @value{GDBN} variable.
34435 @subsubheading @value{GDBN} Command
34437 The corresponding @value{GDBN} command is @samp{show}.
34439 @subsubheading Example
34448 @c @subheading -gdb-source
34451 @subheading The @code{-gdb-version} Command
34452 @findex -gdb-version
34454 @subsubheading Synopsis
34460 Show version information for @value{GDBN}. Used mostly in testing.
34462 @subsubheading @value{GDBN} Command
34464 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
34465 default shows this information when you start an interactive session.
34467 @subsubheading Example
34469 @c This example modifies the actual output from GDB to avoid overfull
34475 ~Copyright 2000 Free Software Foundation, Inc.
34476 ~GDB is free software, covered by the GNU General Public License, and
34477 ~you are welcome to change it and/or distribute copies of it under
34478 ~ certain conditions.
34479 ~Type "show copying" to see the conditions.
34480 ~There is absolutely no warranty for GDB. Type "show warranty" for
34482 ~This GDB was configured as
34483 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
34488 @subheading The @code{-list-features} Command
34489 @findex -list-features
34491 Returns a list of particular features of the MI protocol that
34492 this version of gdb implements. A feature can be a command,
34493 or a new field in an output of some command, or even an
34494 important bugfix. While a frontend can sometimes detect presence
34495 of a feature at runtime, it is easier to perform detection at debugger
34498 The command returns a list of strings, with each string naming an
34499 available feature. Each returned string is just a name, it does not
34500 have any internal structure. The list of possible feature names
34506 (gdb) -list-features
34507 ^done,result=["feature1","feature2"]
34510 The current list of features is:
34513 @item frozen-varobjs
34514 Indicates support for the @code{-var-set-frozen} command, as well
34515 as possible presense of the @code{frozen} field in the output
34516 of @code{-varobj-create}.
34517 @item pending-breakpoints
34518 Indicates support for the @option{-f} option to the @code{-break-insert}
34521 Indicates Python scripting support, Python-based
34522 pretty-printing commands, and possible presence of the
34523 @samp{display_hint} field in the output of @code{-var-list-children}
34525 Indicates support for the @code{-thread-info} command.
34526 @item data-read-memory-bytes
34527 Indicates support for the @code{-data-read-memory-bytes} and the
34528 @code{-data-write-memory-bytes} commands.
34529 @item breakpoint-notifications
34530 Indicates that changes to breakpoints and breakpoints created via the
34531 CLI will be announced via async records.
34532 @item ada-task-info
34533 Indicates support for the @code{-ada-task-info} command.
34536 @subheading The @code{-list-target-features} Command
34537 @findex -list-target-features
34539 Returns a list of particular features that are supported by the
34540 target. Those features affect the permitted MI commands, but
34541 unlike the features reported by the @code{-list-features} command, the
34542 features depend on which target GDB is using at the moment. Whenever
34543 a target can change, due to commands such as @code{-target-select},
34544 @code{-target-attach} or @code{-exec-run}, the list of target features
34545 may change, and the frontend should obtain it again.
34549 (gdb) -list-features
34550 ^done,result=["async"]
34553 The current list of features is:
34557 Indicates that the target is capable of asynchronous command
34558 execution, which means that @value{GDBN} will accept further commands
34559 while the target is running.
34562 Indicates that the target is capable of reverse execution.
34563 @xref{Reverse Execution}, for more information.
34567 @subheading The @code{-list-thread-groups} Command
34568 @findex -list-thread-groups
34570 @subheading Synopsis
34573 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
34576 Lists thread groups (@pxref{Thread groups}). When a single thread
34577 group is passed as the argument, lists the children of that group.
34578 When several thread group are passed, lists information about those
34579 thread groups. Without any parameters, lists information about all
34580 top-level thread groups.
34582 Normally, thread groups that are being debugged are reported.
34583 With the @samp{--available} option, @value{GDBN} reports thread groups
34584 available on the target.
34586 The output of this command may have either a @samp{threads} result or
34587 a @samp{groups} result. The @samp{thread} result has a list of tuples
34588 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
34589 Information}). The @samp{groups} result has a list of tuples as value,
34590 each tuple describing a thread group. If top-level groups are
34591 requested (that is, no parameter is passed), or when several groups
34592 are passed, the output always has a @samp{groups} result. The format
34593 of the @samp{group} result is described below.
34595 To reduce the number of roundtrips it's possible to list thread groups
34596 together with their children, by passing the @samp{--recurse} option
34597 and the recursion depth. Presently, only recursion depth of 1 is
34598 permitted. If this option is present, then every reported thread group
34599 will also include its children, either as @samp{group} or
34600 @samp{threads} field.
34602 In general, any combination of option and parameters is permitted, with
34603 the following caveats:
34607 When a single thread group is passed, the output will typically
34608 be the @samp{threads} result. Because threads may not contain
34609 anything, the @samp{recurse} option will be ignored.
34612 When the @samp{--available} option is passed, limited information may
34613 be available. In particular, the list of threads of a process might
34614 be inaccessible. Further, specifying specific thread groups might
34615 not give any performance advantage over listing all thread groups.
34616 The frontend should assume that @samp{-list-thread-groups --available}
34617 is always an expensive operation and cache the results.
34621 The @samp{groups} result is a list of tuples, where each tuple may
34622 have the following fields:
34626 Identifier of the thread group. This field is always present.
34627 The identifier is an opaque string; frontends should not try to
34628 convert it to an integer, even though it might look like one.
34631 The type of the thread group. At present, only @samp{process} is a
34635 The target-specific process identifier. This field is only present
34636 for thread groups of type @samp{process} and only if the process exists.
34639 The number of children this thread group has. This field may be
34640 absent for an available thread group.
34643 This field has a list of tuples as value, each tuple describing a
34644 thread. It may be present if the @samp{--recurse} option is
34645 specified, and it's actually possible to obtain the threads.
34648 This field is a list of integers, each identifying a core that one
34649 thread of the group is running on. This field may be absent if
34650 such information is not available.
34653 The name of the executable file that corresponds to this thread group.
34654 The field is only present for thread groups of type @samp{process},
34655 and only if there is a corresponding executable file.
34659 @subheading Example
34663 -list-thread-groups
34664 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
34665 -list-thread-groups 17
34666 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
34667 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
34668 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
34669 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
34670 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
34671 -list-thread-groups --available
34672 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
34673 -list-thread-groups --available --recurse 1
34674 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34675 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34676 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
34677 -list-thread-groups --available --recurse 1 17 18
34678 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
34679 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
34680 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
34683 @subheading The @code{-info-os} Command
34686 @subsubheading Synopsis
34689 -info-os [ @var{type} ]
34692 If no argument is supplied, the command returns a table of available
34693 operating-system-specific information types. If one of these types is
34694 supplied as an argument @var{type}, then the command returns a table
34695 of data of that type.
34697 The types of information available depend on the target operating
34700 @subsubheading @value{GDBN} Command
34702 The corresponding @value{GDBN} command is @samp{info os}.
34704 @subsubheading Example
34706 When run on a @sc{gnu}/Linux system, the output will look something
34712 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
34713 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
34714 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
34715 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
34716 body=[item=@{col0="processes",col1="Listing of all processes",
34717 col2="Processes"@},
34718 item=@{col0="procgroups",col1="Listing of all process groups",
34719 col2="Process groups"@},
34720 item=@{col0="threads",col1="Listing of all threads",
34722 item=@{col0="files",col1="Listing of all file descriptors",
34723 col2="File descriptors"@},
34724 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
34726 item=@{col0="shm",col1="Listing of all shared-memory regions",
34727 col2="Shared-memory regions"@},
34728 item=@{col0="semaphores",col1="Listing of all semaphores",
34729 col2="Semaphores"@},
34730 item=@{col0="msg",col1="Listing of all message queues",
34731 col2="Message queues"@},
34732 item=@{col0="modules",col1="Listing of all loaded kernel modules",
34733 col2="Kernel modules"@}]@}
34736 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
34737 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
34738 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
34739 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
34740 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
34741 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
34742 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
34743 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
34745 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
34746 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
34750 (Note that the MI output here includes a @code{"Title"} column that
34751 does not appear in command-line @code{info os}; this column is useful
34752 for MI clients that want to enumerate the types of data, such as in a
34753 popup menu, but is needless clutter on the command line, and
34754 @code{info os} omits it.)
34756 @subheading The @code{-add-inferior} Command
34757 @findex -add-inferior
34759 @subheading Synopsis
34765 Creates a new inferior (@pxref{Inferiors and Programs}). The created
34766 inferior is not associated with any executable. Such association may
34767 be established with the @samp{-file-exec-and-symbols} command
34768 (@pxref{GDB/MI File Commands}). The command response has a single
34769 field, @samp{inferior}, whose value is the identifier of the
34770 thread group corresponding to the new inferior.
34772 @subheading Example
34777 ^done,inferior="i3"
34780 @subheading The @code{-interpreter-exec} Command
34781 @findex -interpreter-exec
34783 @subheading Synopsis
34786 -interpreter-exec @var{interpreter} @var{command}
34788 @anchor{-interpreter-exec}
34790 Execute the specified @var{command} in the given @var{interpreter}.
34792 @subheading @value{GDBN} Command
34794 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
34796 @subheading Example
34800 -interpreter-exec console "break main"
34801 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
34802 &"During symbol reading, bad structure-type format.\n"
34803 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
34808 @subheading The @code{-inferior-tty-set} Command
34809 @findex -inferior-tty-set
34811 @subheading Synopsis
34814 -inferior-tty-set /dev/pts/1
34817 Set terminal for future runs of the program being debugged.
34819 @subheading @value{GDBN} Command
34821 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
34823 @subheading Example
34827 -inferior-tty-set /dev/pts/1
34832 @subheading The @code{-inferior-tty-show} Command
34833 @findex -inferior-tty-show
34835 @subheading Synopsis
34841 Show terminal for future runs of program being debugged.
34843 @subheading @value{GDBN} Command
34845 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
34847 @subheading Example
34851 -inferior-tty-set /dev/pts/1
34855 ^done,inferior_tty_terminal="/dev/pts/1"
34859 @subheading The @code{-enable-timings} Command
34860 @findex -enable-timings
34862 @subheading Synopsis
34865 -enable-timings [yes | no]
34868 Toggle the printing of the wallclock, user and system times for an MI
34869 command as a field in its output. This command is to help frontend
34870 developers optimize the performance of their code. No argument is
34871 equivalent to @samp{yes}.
34873 @subheading @value{GDBN} Command
34877 @subheading Example
34885 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
34886 addr="0x080484ed",func="main",file="myprog.c",
34887 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
34889 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
34897 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
34898 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
34899 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
34900 fullname="/home/nickrob/myprog.c",line="73"@}
34905 @chapter @value{GDBN} Annotations
34907 This chapter describes annotations in @value{GDBN}. Annotations were
34908 designed to interface @value{GDBN} to graphical user interfaces or other
34909 similar programs which want to interact with @value{GDBN} at a
34910 relatively high level.
34912 The annotation mechanism has largely been superseded by @sc{gdb/mi}
34916 This is Edition @value{EDITION}, @value{DATE}.
34920 * Annotations Overview:: What annotations are; the general syntax.
34921 * Server Prefix:: Issuing a command without affecting user state.
34922 * Prompting:: Annotations marking @value{GDBN}'s need for input.
34923 * Errors:: Annotations for error messages.
34924 * Invalidation:: Some annotations describe things now invalid.
34925 * Annotations for Running::
34926 Whether the program is running, how it stopped, etc.
34927 * Source Annotations:: Annotations describing source code.
34930 @node Annotations Overview
34931 @section What is an Annotation?
34932 @cindex annotations
34934 Annotations start with a newline character, two @samp{control-z}
34935 characters, and the name of the annotation. If there is no additional
34936 information associated with this annotation, the name of the annotation
34937 is followed immediately by a newline. If there is additional
34938 information, the name of the annotation is followed by a space, the
34939 additional information, and a newline. The additional information
34940 cannot contain newline characters.
34942 Any output not beginning with a newline and two @samp{control-z}
34943 characters denotes literal output from @value{GDBN}. Currently there is
34944 no need for @value{GDBN} to output a newline followed by two
34945 @samp{control-z} characters, but if there was such a need, the
34946 annotations could be extended with an @samp{escape} annotation which
34947 means those three characters as output.
34949 The annotation @var{level}, which is specified using the
34950 @option{--annotate} command line option (@pxref{Mode Options}), controls
34951 how much information @value{GDBN} prints together with its prompt,
34952 values of expressions, source lines, and other types of output. Level 0
34953 is for no annotations, level 1 is for use when @value{GDBN} is run as a
34954 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
34955 for programs that control @value{GDBN}, and level 2 annotations have
34956 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
34957 Interface, annotate, GDB's Obsolete Annotations}).
34960 @kindex set annotate
34961 @item set annotate @var{level}
34962 The @value{GDBN} command @code{set annotate} sets the level of
34963 annotations to the specified @var{level}.
34965 @item show annotate
34966 @kindex show annotate
34967 Show the current annotation level.
34970 This chapter describes level 3 annotations.
34972 A simple example of starting up @value{GDBN} with annotations is:
34975 $ @kbd{gdb --annotate=3}
34977 Copyright 2003 Free Software Foundation, Inc.
34978 GDB is free software, covered by the GNU General Public License,
34979 and you are welcome to change it and/or distribute copies of it
34980 under certain conditions.
34981 Type "show copying" to see the conditions.
34982 There is absolutely no warranty for GDB. Type "show warranty"
34984 This GDB was configured as "i386-pc-linux-gnu"
34995 Here @samp{quit} is input to @value{GDBN}; the rest is output from
34996 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
34997 denotes a @samp{control-z} character) are annotations; the rest is
34998 output from @value{GDBN}.
35000 @node Server Prefix
35001 @section The Server Prefix
35002 @cindex server prefix
35004 If you prefix a command with @samp{server } then it will not affect
35005 the command history, nor will it affect @value{GDBN}'s notion of which
35006 command to repeat if @key{RET} is pressed on a line by itself. This
35007 means that commands can be run behind a user's back by a front-end in
35008 a transparent manner.
35010 The @code{server } prefix does not affect the recording of values into
35011 the value history; to print a value without recording it into the
35012 value history, use the @code{output} command instead of the
35013 @code{print} command.
35015 Using this prefix also disables confirmation requests
35016 (@pxref{confirmation requests}).
35019 @section Annotation for @value{GDBN} Input
35021 @cindex annotations for prompts
35022 When @value{GDBN} prompts for input, it annotates this fact so it is possible
35023 to know when to send output, when the output from a given command is
35026 Different kinds of input each have a different @dfn{input type}. Each
35027 input type has three annotations: a @code{pre-} annotation, which
35028 denotes the beginning of any prompt which is being output, a plain
35029 annotation, which denotes the end of the prompt, and then a @code{post-}
35030 annotation which denotes the end of any echo which may (or may not) be
35031 associated with the input. For example, the @code{prompt} input type
35032 features the following annotations:
35040 The input types are
35043 @findex pre-prompt annotation
35044 @findex prompt annotation
35045 @findex post-prompt annotation
35047 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
35049 @findex pre-commands annotation
35050 @findex commands annotation
35051 @findex post-commands annotation
35053 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
35054 command. The annotations are repeated for each command which is input.
35056 @findex pre-overload-choice annotation
35057 @findex overload-choice annotation
35058 @findex post-overload-choice annotation
35059 @item overload-choice
35060 When @value{GDBN} wants the user to select between various overloaded functions.
35062 @findex pre-query annotation
35063 @findex query annotation
35064 @findex post-query annotation
35066 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
35068 @findex pre-prompt-for-continue annotation
35069 @findex prompt-for-continue annotation
35070 @findex post-prompt-for-continue annotation
35071 @item prompt-for-continue
35072 When @value{GDBN} is asking the user to press return to continue. Note: Don't
35073 expect this to work well; instead use @code{set height 0} to disable
35074 prompting. This is because the counting of lines is buggy in the
35075 presence of annotations.
35080 @cindex annotations for errors, warnings and interrupts
35082 @findex quit annotation
35087 This annotation occurs right before @value{GDBN} responds to an interrupt.
35089 @findex error annotation
35094 This annotation occurs right before @value{GDBN} responds to an error.
35096 Quit and error annotations indicate that any annotations which @value{GDBN} was
35097 in the middle of may end abruptly. For example, if a
35098 @code{value-history-begin} annotation is followed by a @code{error}, one
35099 cannot expect to receive the matching @code{value-history-end}. One
35100 cannot expect not to receive it either, however; an error annotation
35101 does not necessarily mean that @value{GDBN} is immediately returning all the way
35104 @findex error-begin annotation
35105 A quit or error annotation may be preceded by
35111 Any output between that and the quit or error annotation is the error
35114 Warning messages are not yet annotated.
35115 @c If we want to change that, need to fix warning(), type_error(),
35116 @c range_error(), and possibly other places.
35119 @section Invalidation Notices
35121 @cindex annotations for invalidation messages
35122 The following annotations say that certain pieces of state may have
35126 @findex frames-invalid annotation
35127 @item ^Z^Zframes-invalid
35129 The frames (for example, output from the @code{backtrace} command) may
35132 @findex breakpoints-invalid annotation
35133 @item ^Z^Zbreakpoints-invalid
35135 The breakpoints may have changed. For example, the user just added or
35136 deleted a breakpoint.
35139 @node Annotations for Running
35140 @section Running the Program
35141 @cindex annotations for running programs
35143 @findex starting annotation
35144 @findex stopping annotation
35145 When the program starts executing due to a @value{GDBN} command such as
35146 @code{step} or @code{continue},
35152 is output. When the program stops,
35158 is output. Before the @code{stopped} annotation, a variety of
35159 annotations describe how the program stopped.
35162 @findex exited annotation
35163 @item ^Z^Zexited @var{exit-status}
35164 The program exited, and @var{exit-status} is the exit status (zero for
35165 successful exit, otherwise nonzero).
35167 @findex signalled annotation
35168 @findex signal-name annotation
35169 @findex signal-name-end annotation
35170 @findex signal-string annotation
35171 @findex signal-string-end annotation
35172 @item ^Z^Zsignalled
35173 The program exited with a signal. After the @code{^Z^Zsignalled}, the
35174 annotation continues:
35180 ^Z^Zsignal-name-end
35184 ^Z^Zsignal-string-end
35189 where @var{name} is the name of the signal, such as @code{SIGILL} or
35190 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
35191 as @code{Illegal Instruction} or @code{Segmentation fault}.
35192 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
35193 user's benefit and have no particular format.
35195 @findex signal annotation
35197 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
35198 just saying that the program received the signal, not that it was
35199 terminated with it.
35201 @findex breakpoint annotation
35202 @item ^Z^Zbreakpoint @var{number}
35203 The program hit breakpoint number @var{number}.
35205 @findex watchpoint annotation
35206 @item ^Z^Zwatchpoint @var{number}
35207 The program hit watchpoint number @var{number}.
35210 @node Source Annotations
35211 @section Displaying Source
35212 @cindex annotations for source display
35214 @findex source annotation
35215 The following annotation is used instead of displaying source code:
35218 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
35221 where @var{filename} is an absolute file name indicating which source
35222 file, @var{line} is the line number within that file (where 1 is the
35223 first line in the file), @var{character} is the character position
35224 within the file (where 0 is the first character in the file) (for most
35225 debug formats this will necessarily point to the beginning of a line),
35226 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
35227 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
35228 @var{addr} is the address in the target program associated with the
35229 source which is being displayed. @var{addr} is in the form @samp{0x}
35230 followed by one or more lowercase hex digits (note that this does not
35231 depend on the language).
35233 @node JIT Interface
35234 @chapter JIT Compilation Interface
35235 @cindex just-in-time compilation
35236 @cindex JIT compilation interface
35238 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
35239 interface. A JIT compiler is a program or library that generates native
35240 executable code at runtime and executes it, usually in order to achieve good
35241 performance while maintaining platform independence.
35243 Programs that use JIT compilation are normally difficult to debug because
35244 portions of their code are generated at runtime, instead of being loaded from
35245 object files, which is where @value{GDBN} normally finds the program's symbols
35246 and debug information. In order to debug programs that use JIT compilation,
35247 @value{GDBN} has an interface that allows the program to register in-memory
35248 symbol files with @value{GDBN} at runtime.
35250 If you are using @value{GDBN} to debug a program that uses this interface, then
35251 it should work transparently so long as you have not stripped the binary. If
35252 you are developing a JIT compiler, then the interface is documented in the rest
35253 of this chapter. At this time, the only known client of this interface is the
35256 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
35257 JIT compiler communicates with @value{GDBN} by writing data into a global
35258 variable and calling a fuction at a well-known symbol. When @value{GDBN}
35259 attaches, it reads a linked list of symbol files from the global variable to
35260 find existing code, and puts a breakpoint in the function so that it can find
35261 out about additional code.
35264 * Declarations:: Relevant C struct declarations
35265 * Registering Code:: Steps to register code
35266 * Unregistering Code:: Steps to unregister code
35267 * Custom Debug Info:: Emit debug information in a custom format
35271 @section JIT Declarations
35273 These are the relevant struct declarations that a C program should include to
35274 implement the interface:
35284 struct jit_code_entry
35286 struct jit_code_entry *next_entry;
35287 struct jit_code_entry *prev_entry;
35288 const char *symfile_addr;
35289 uint64_t symfile_size;
35292 struct jit_descriptor
35295 /* This type should be jit_actions_t, but we use uint32_t
35296 to be explicit about the bitwidth. */
35297 uint32_t action_flag;
35298 struct jit_code_entry *relevant_entry;
35299 struct jit_code_entry *first_entry;
35302 /* GDB puts a breakpoint in this function. */
35303 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
35305 /* Make sure to specify the version statically, because the
35306 debugger may check the version before we can set it. */
35307 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
35310 If the JIT is multi-threaded, then it is important that the JIT synchronize any
35311 modifications to this global data properly, which can easily be done by putting
35312 a global mutex around modifications to these structures.
35314 @node Registering Code
35315 @section Registering Code
35317 To register code with @value{GDBN}, the JIT should follow this protocol:
35321 Generate an object file in memory with symbols and other desired debug
35322 information. The file must include the virtual addresses of the sections.
35325 Create a code entry for the file, which gives the start and size of the symbol
35329 Add it to the linked list in the JIT descriptor.
35332 Point the relevant_entry field of the descriptor at the entry.
35335 Set @code{action_flag} to @code{JIT_REGISTER} and call
35336 @code{__jit_debug_register_code}.
35339 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
35340 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
35341 new code. However, the linked list must still be maintained in order to allow
35342 @value{GDBN} to attach to a running process and still find the symbol files.
35344 @node Unregistering Code
35345 @section Unregistering Code
35347 If code is freed, then the JIT should use the following protocol:
35351 Remove the code entry corresponding to the code from the linked list.
35354 Point the @code{relevant_entry} field of the descriptor at the code entry.
35357 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
35358 @code{__jit_debug_register_code}.
35361 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
35362 and the JIT will leak the memory used for the associated symbol files.
35364 @node Custom Debug Info
35365 @section Custom Debug Info
35366 @cindex custom JIT debug info
35367 @cindex JIT debug info reader
35369 Generating debug information in platform-native file formats (like ELF
35370 or COFF) may be an overkill for JIT compilers; especially if all the
35371 debug info is used for is displaying a meaningful backtrace. The
35372 issue can be resolved by having the JIT writers decide on a debug info
35373 format and also provide a reader that parses the debug info generated
35374 by the JIT compiler. This section gives a brief overview on writing
35375 such a parser. More specific details can be found in the source file
35376 @file{gdb/jit-reader.in}, which is also installed as a header at
35377 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
35379 The reader is implemented as a shared object (so this functionality is
35380 not available on platforms which don't allow loading shared objects at
35381 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
35382 @code{jit-reader-unload} are provided, to be used to load and unload
35383 the readers from a preconfigured directory. Once loaded, the shared
35384 object is used the parse the debug information emitted by the JIT
35388 * Using JIT Debug Info Readers:: How to use supplied readers correctly
35389 * Writing JIT Debug Info Readers:: Creating a debug-info reader
35392 @node Using JIT Debug Info Readers
35393 @subsection Using JIT Debug Info Readers
35394 @kindex jit-reader-load
35395 @kindex jit-reader-unload
35397 Readers can be loaded and unloaded using the @code{jit-reader-load}
35398 and @code{jit-reader-unload} commands.
35401 @item jit-reader-load @var{reader}
35402 Load the JIT reader named @var{reader}. @var{reader} is a shared
35403 object specified as either an absolute or a relative file name. In
35404 the latter case, @value{GDBN} will try to load the reader from a
35405 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
35406 system (here @var{libdir} is the system library directory, often
35407 @file{/usr/local/lib}).
35409 Only one reader can be active at a time; trying to load a second
35410 reader when one is already loaded will result in @value{GDBN}
35411 reporting an error. A new JIT reader can be loaded by first unloading
35412 the current one using @code{jit-reader-unload} and then invoking
35413 @code{jit-reader-load}.
35415 @item jit-reader-unload
35416 Unload the currently loaded JIT reader.
35420 @node Writing JIT Debug Info Readers
35421 @subsection Writing JIT Debug Info Readers
35422 @cindex writing JIT debug info readers
35424 As mentioned, a reader is essentially a shared object conforming to a
35425 certain ABI. This ABI is described in @file{jit-reader.h}.
35427 @file{jit-reader.h} defines the structures, macros and functions
35428 required to write a reader. It is installed (along with
35429 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
35430 the system include directory.
35432 Readers need to be released under a GPL compatible license. A reader
35433 can be declared as released under such a license by placing the macro
35434 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
35436 The entry point for readers is the symbol @code{gdb_init_reader},
35437 which is expected to be a function with the prototype
35439 @findex gdb_init_reader
35441 extern struct gdb_reader_funcs *gdb_init_reader (void);
35444 @cindex @code{struct gdb_reader_funcs}
35446 @code{struct gdb_reader_funcs} contains a set of pointers to callback
35447 functions. These functions are executed to read the debug info
35448 generated by the JIT compiler (@code{read}), to unwind stack frames
35449 (@code{unwind}) and to create canonical frame IDs
35450 (@code{get_Frame_id}). It also has a callback that is called when the
35451 reader is being unloaded (@code{destroy}). The struct looks like this
35454 struct gdb_reader_funcs
35456 /* Must be set to GDB_READER_INTERFACE_VERSION. */
35457 int reader_version;
35459 /* For use by the reader. */
35462 gdb_read_debug_info *read;
35463 gdb_unwind_frame *unwind;
35464 gdb_get_frame_id *get_frame_id;
35465 gdb_destroy_reader *destroy;
35469 @cindex @code{struct gdb_symbol_callbacks}
35470 @cindex @code{struct gdb_unwind_callbacks}
35472 The callbacks are provided with another set of callbacks by
35473 @value{GDBN} to do their job. For @code{read}, these callbacks are
35474 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
35475 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
35476 @code{struct gdb_symbol_callbacks} has callbacks to create new object
35477 files and new symbol tables inside those object files. @code{struct
35478 gdb_unwind_callbacks} has callbacks to read registers off the current
35479 frame and to write out the values of the registers in the previous
35480 frame. Both have a callback (@code{target_read}) to read bytes off the
35481 target's address space.
35483 @node In-Process Agent
35484 @chapter In-Process Agent
35485 @cindex debugging agent
35486 The traditional debugging model is conceptually low-speed, but works fine,
35487 because most bugs can be reproduced in debugging-mode execution. However,
35488 as multi-core or many-core processors are becoming mainstream, and
35489 multi-threaded programs become more and more popular, there should be more
35490 and more bugs that only manifest themselves at normal-mode execution, for
35491 example, thread races, because debugger's interference with the program's
35492 timing may conceal the bugs. On the other hand, in some applications,
35493 it is not feasible for the debugger to interrupt the program's execution
35494 long enough for the developer to learn anything helpful about its behavior.
35495 If the program's correctness depends on its real-time behavior, delays
35496 introduced by a debugger might cause the program to fail, even when the
35497 code itself is correct. It is useful to be able to observe the program's
35498 behavior without interrupting it.
35500 Therefore, traditional debugging model is too intrusive to reproduce
35501 some bugs. In order to reduce the interference with the program, we can
35502 reduce the number of operations performed by debugger. The
35503 @dfn{In-Process Agent}, a shared library, is running within the same
35504 process with inferior, and is able to perform some debugging operations
35505 itself. As a result, debugger is only involved when necessary, and
35506 performance of debugging can be improved accordingly. Note that
35507 interference with program can be reduced but can't be removed completely,
35508 because the in-process agent will still stop or slow down the program.
35510 The in-process agent can interpret and execute Agent Expressions
35511 (@pxref{Agent Expressions}) during performing debugging operations. The
35512 agent expressions can be used for different purposes, such as collecting
35513 data in tracepoints, and condition evaluation in breakpoints.
35515 @anchor{Control Agent}
35516 You can control whether the in-process agent is used as an aid for
35517 debugging with the following commands:
35520 @kindex set agent on
35522 Causes the in-process agent to perform some operations on behalf of the
35523 debugger. Just which operations requested by the user will be done
35524 by the in-process agent depends on the its capabilities. For example,
35525 if you request to evaluate breakpoint conditions in the in-process agent,
35526 and the in-process agent has such capability as well, then breakpoint
35527 conditions will be evaluated in the in-process agent.
35529 @kindex set agent off
35530 @item set agent off
35531 Disables execution of debugging operations by the in-process agent. All
35532 of the operations will be performed by @value{GDBN}.
35536 Display the current setting of execution of debugging operations by
35537 the in-process agent.
35541 * In-Process Agent Protocol::
35544 @node In-Process Agent Protocol
35545 @section In-Process Agent Protocol
35546 @cindex in-process agent protocol
35548 The in-process agent is able to communicate with both @value{GDBN} and
35549 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
35550 used for communications between @value{GDBN} or GDBserver and the IPA.
35551 In general, @value{GDBN} or GDBserver sends commands
35552 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
35553 in-process agent replies back with the return result of the command, or
35554 some other information. The data sent to in-process agent is composed
35555 of primitive data types, such as 4-byte or 8-byte type, and composite
35556 types, which are called objects (@pxref{IPA Protocol Objects}).
35559 * IPA Protocol Objects::
35560 * IPA Protocol Commands::
35563 @node IPA Protocol Objects
35564 @subsection IPA Protocol Objects
35565 @cindex ipa protocol objects
35567 The commands sent to and results received from agent may contain some
35568 complex data types called @dfn{objects}.
35570 The in-process agent is running on the same machine with @value{GDBN}
35571 or GDBserver, so it doesn't have to handle as much differences between
35572 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
35573 However, there are still some differences of two ends in two processes:
35577 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
35578 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
35580 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
35581 GDBserver is compiled with one, and in-process agent is compiled with
35585 Here are the IPA Protocol Objects:
35589 agent expression object. It represents an agent expression
35590 (@pxref{Agent Expressions}).
35591 @anchor{agent expression object}
35593 tracepoint action object. It represents a tracepoint action
35594 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
35595 memory, static trace data and to evaluate expression.
35596 @anchor{tracepoint action object}
35598 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
35599 @anchor{tracepoint object}
35603 The following table describes important attributes of each IPA protocol
35606 @multitable @columnfractions .30 .20 .50
35607 @headitem Name @tab Size @tab Description
35608 @item @emph{agent expression object} @tab @tab
35609 @item length @tab 4 @tab length of bytes code
35610 @item byte code @tab @var{length} @tab contents of byte code
35611 @item @emph{tracepoint action for collecting memory} @tab @tab
35612 @item 'M' @tab 1 @tab type of tracepoint action
35613 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
35614 address of the lowest byte to collect, otherwise @var{addr} is the offset
35615 of @var{basereg} for memory collecting.
35616 @item len @tab 8 @tab length of memory for collecting
35617 @item basereg @tab 4 @tab the register number containing the starting
35618 memory address for collecting.
35619 @item @emph{tracepoint action for collecting registers} @tab @tab
35620 @item 'R' @tab 1 @tab type of tracepoint action
35621 @item @emph{tracepoint action for collecting static trace data} @tab @tab
35622 @item 'L' @tab 1 @tab type of tracepoint action
35623 @item @emph{tracepoint action for expression evaluation} @tab @tab
35624 @item 'X' @tab 1 @tab type of tracepoint action
35625 @item agent expression @tab length of @tab @ref{agent expression object}
35626 @item @emph{tracepoint object} @tab @tab
35627 @item number @tab 4 @tab number of tracepoint
35628 @item address @tab 8 @tab address of tracepoint inserted on
35629 @item type @tab 4 @tab type of tracepoint
35630 @item enabled @tab 1 @tab enable or disable of tracepoint
35631 @item step_count @tab 8 @tab step
35632 @item pass_count @tab 8 @tab pass
35633 @item numactions @tab 4 @tab number of tracepoint actions
35634 @item hit count @tab 8 @tab hit count
35635 @item trace frame usage @tab 8 @tab trace frame usage
35636 @item compiled_cond @tab 8 @tab compiled condition
35637 @item orig_size @tab 8 @tab orig size
35638 @item condition @tab 4 if condition is NULL otherwise length of
35639 @ref{agent expression object}
35640 @tab zero if condition is NULL, otherwise is
35641 @ref{agent expression object}
35642 @item actions @tab variable
35643 @tab numactions number of @ref{tracepoint action object}
35646 @node IPA Protocol Commands
35647 @subsection IPA Protocol Commands
35648 @cindex ipa protocol commands
35650 The spaces in each command are delimiters to ease reading this commands
35651 specification. They don't exist in real commands.
35655 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
35656 Installs a new fast tracepoint described by @var{tracepoint_object}
35657 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
35658 head of @dfn{jumppad}, which is used to jump to data collection routine
35663 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
35664 @var{target_address} is address of tracepoint in the inferior.
35665 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
35666 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
35667 @var{fjump} contains a sequence of instructions jump to jumppad entry.
35668 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
35675 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
35676 is about to kill inferiors.
35684 @item probe_marker_at:@var{address}
35685 Asks in-process agent to probe the marker at @var{address}.
35692 @item unprobe_marker_at:@var{address}
35693 Asks in-process agent to unprobe the marker at @var{address}.
35697 @chapter Reporting Bugs in @value{GDBN}
35698 @cindex bugs in @value{GDBN}
35699 @cindex reporting bugs in @value{GDBN}
35701 Your bug reports play an essential role in making @value{GDBN} reliable.
35703 Reporting a bug may help you by bringing a solution to your problem, or it
35704 may not. But in any case the principal function of a bug report is to help
35705 the entire community by making the next version of @value{GDBN} work better. Bug
35706 reports are your contribution to the maintenance of @value{GDBN}.
35708 In order for a bug report to serve its purpose, you must include the
35709 information that enables us to fix the bug.
35712 * Bug Criteria:: Have you found a bug?
35713 * Bug Reporting:: How to report bugs
35717 @section Have You Found a Bug?
35718 @cindex bug criteria
35720 If you are not sure whether you have found a bug, here are some guidelines:
35723 @cindex fatal signal
35724 @cindex debugger crash
35725 @cindex crash of debugger
35727 If the debugger gets a fatal signal, for any input whatever, that is a
35728 @value{GDBN} bug. Reliable debuggers never crash.
35730 @cindex error on valid input
35732 If @value{GDBN} produces an error message for valid input, that is a
35733 bug. (Note that if you're cross debugging, the problem may also be
35734 somewhere in the connection to the target.)
35736 @cindex invalid input
35738 If @value{GDBN} does not produce an error message for invalid input,
35739 that is a bug. However, you should note that your idea of
35740 ``invalid input'' might be our idea of ``an extension'' or ``support
35741 for traditional practice''.
35744 If you are an experienced user of debugging tools, your suggestions
35745 for improvement of @value{GDBN} are welcome in any case.
35748 @node Bug Reporting
35749 @section How to Report Bugs
35750 @cindex bug reports
35751 @cindex @value{GDBN} bugs, reporting
35753 A number of companies and individuals offer support for @sc{gnu} products.
35754 If you obtained @value{GDBN} from a support organization, we recommend you
35755 contact that organization first.
35757 You can find contact information for many support companies and
35758 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
35760 @c should add a web page ref...
35763 @ifset BUGURL_DEFAULT
35764 In any event, we also recommend that you submit bug reports for
35765 @value{GDBN}. The preferred method is to submit them directly using
35766 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
35767 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
35770 @strong{Do not send bug reports to @samp{info-gdb}, or to
35771 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
35772 not want to receive bug reports. Those that do have arranged to receive
35775 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
35776 serves as a repeater. The mailing list and the newsgroup carry exactly
35777 the same messages. Often people think of posting bug reports to the
35778 newsgroup instead of mailing them. This appears to work, but it has one
35779 problem which can be crucial: a newsgroup posting often lacks a mail
35780 path back to the sender. Thus, if we need to ask for more information,
35781 we may be unable to reach you. For this reason, it is better to send
35782 bug reports to the mailing list.
35784 @ifclear BUGURL_DEFAULT
35785 In any event, we also recommend that you submit bug reports for
35786 @value{GDBN} to @value{BUGURL}.
35790 The fundamental principle of reporting bugs usefully is this:
35791 @strong{report all the facts}. If you are not sure whether to state a
35792 fact or leave it out, state it!
35794 Often people omit facts because they think they know what causes the
35795 problem and assume that some details do not matter. Thus, you might
35796 assume that the name of the variable you use in an example does not matter.
35797 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
35798 stray memory reference which happens to fetch from the location where that
35799 name is stored in memory; perhaps, if the name were different, the contents
35800 of that location would fool the debugger into doing the right thing despite
35801 the bug. Play it safe and give a specific, complete example. That is the
35802 easiest thing for you to do, and the most helpful.
35804 Keep in mind that the purpose of a bug report is to enable us to fix the
35805 bug. It may be that the bug has been reported previously, but neither
35806 you nor we can know that unless your bug report is complete and
35809 Sometimes people give a few sketchy facts and ask, ``Does this ring a
35810 bell?'' Those bug reports are useless, and we urge everyone to
35811 @emph{refuse to respond to them} except to chide the sender to report
35814 To enable us to fix the bug, you should include all these things:
35818 The version of @value{GDBN}. @value{GDBN} announces it if you start
35819 with no arguments; you can also print it at any time using @code{show
35822 Without this, we will not know whether there is any point in looking for
35823 the bug in the current version of @value{GDBN}.
35826 The type of machine you are using, and the operating system name and
35830 The details of the @value{GDBN} build-time configuration.
35831 @value{GDBN} shows these details if you invoke it with the
35832 @option{--configuration} command-line option, or if you type
35833 @code{show configuration} at @value{GDBN}'s prompt.
35836 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
35837 ``@value{GCC}--2.8.1''.
35840 What compiler (and its version) was used to compile the program you are
35841 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
35842 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
35843 to get this information; for other compilers, see the documentation for
35847 The command arguments you gave the compiler to compile your example and
35848 observe the bug. For example, did you use @samp{-O}? To guarantee
35849 you will not omit something important, list them all. A copy of the
35850 Makefile (or the output from make) is sufficient.
35852 If we were to try to guess the arguments, we would probably guess wrong
35853 and then we might not encounter the bug.
35856 A complete input script, and all necessary source files, that will
35860 A description of what behavior you observe that you believe is
35861 incorrect. For example, ``It gets a fatal signal.''
35863 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
35864 will certainly notice it. But if the bug is incorrect output, we might
35865 not notice unless it is glaringly wrong. You might as well not give us
35866 a chance to make a mistake.
35868 Even if the problem you experience is a fatal signal, you should still
35869 say so explicitly. Suppose something strange is going on, such as, your
35870 copy of @value{GDBN} is out of synch, or you have encountered a bug in
35871 the C library on your system. (This has happened!) Your copy might
35872 crash and ours would not. If you told us to expect a crash, then when
35873 ours fails to crash, we would know that the bug was not happening for
35874 us. If you had not told us to expect a crash, then we would not be able
35875 to draw any conclusion from our observations.
35878 @cindex recording a session script
35879 To collect all this information, you can use a session recording program
35880 such as @command{script}, which is available on many Unix systems.
35881 Just run your @value{GDBN} session inside @command{script} and then
35882 include the @file{typescript} file with your bug report.
35884 Another way to record a @value{GDBN} session is to run @value{GDBN}
35885 inside Emacs and then save the entire buffer to a file.
35888 If you wish to suggest changes to the @value{GDBN} source, send us context
35889 diffs. If you even discuss something in the @value{GDBN} source, refer to
35890 it by context, not by line number.
35892 The line numbers in our development sources will not match those in your
35893 sources. Your line numbers would convey no useful information to us.
35897 Here are some things that are not necessary:
35901 A description of the envelope of the bug.
35903 Often people who encounter a bug spend a lot of time investigating
35904 which changes to the input file will make the bug go away and which
35905 changes will not affect it.
35907 This is often time consuming and not very useful, because the way we
35908 will find the bug is by running a single example under the debugger
35909 with breakpoints, not by pure deduction from a series of examples.
35910 We recommend that you save your time for something else.
35912 Of course, if you can find a simpler example to report @emph{instead}
35913 of the original one, that is a convenience for us. Errors in the
35914 output will be easier to spot, running under the debugger will take
35915 less time, and so on.
35917 However, simplification is not vital; if you do not want to do this,
35918 report the bug anyway and send us the entire test case you used.
35921 A patch for the bug.
35923 A patch for the bug does help us if it is a good one. But do not omit
35924 the necessary information, such as the test case, on the assumption that
35925 a patch is all we need. We might see problems with your patch and decide
35926 to fix the problem another way, or we might not understand it at all.
35928 Sometimes with a program as complicated as @value{GDBN} it is very hard to
35929 construct an example that will make the program follow a certain path
35930 through the code. If you do not send us the example, we will not be able
35931 to construct one, so we will not be able to verify that the bug is fixed.
35933 And if we cannot understand what bug you are trying to fix, or why your
35934 patch should be an improvement, we will not install it. A test case will
35935 help us to understand.
35938 A guess about what the bug is or what it depends on.
35940 Such guesses are usually wrong. Even we cannot guess right about such
35941 things without first using the debugger to find the facts.
35944 @c The readline documentation is distributed with the readline code
35945 @c and consists of the two following files:
35948 @c Use -I with makeinfo to point to the appropriate directory,
35949 @c environment var TEXINPUTS with TeX.
35950 @ifclear SYSTEM_READLINE
35951 @include rluser.texi
35952 @include hsuser.texi
35956 @appendix In Memoriam
35958 The @value{GDBN} project mourns the loss of the following long-time
35963 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
35964 to Free Software in general. Outside of @value{GDBN}, he was known in
35965 the Amiga world for his series of Fish Disks, and the GeekGadget project.
35967 @item Michael Snyder
35968 Michael was one of the Global Maintainers of the @value{GDBN} project,
35969 with contributions recorded as early as 1996, until 2011. In addition
35970 to his day to day participation, he was a large driving force behind
35971 adding Reverse Debugging to @value{GDBN}.
35974 Beyond their technical contributions to the project, they were also
35975 enjoyable members of the Free Software Community. We will miss them.
35977 @node Formatting Documentation
35978 @appendix Formatting Documentation
35980 @cindex @value{GDBN} reference card
35981 @cindex reference card
35982 The @value{GDBN} 4 release includes an already-formatted reference card, ready
35983 for printing with PostScript or Ghostscript, in the @file{gdb}
35984 subdirectory of the main source directory@footnote{In
35985 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
35986 release.}. If you can use PostScript or Ghostscript with your printer,
35987 you can print the reference card immediately with @file{refcard.ps}.
35989 The release also includes the source for the reference card. You
35990 can format it, using @TeX{}, by typing:
35996 The @value{GDBN} reference card is designed to print in @dfn{landscape}
35997 mode on US ``letter'' size paper;
35998 that is, on a sheet 11 inches wide by 8.5 inches
35999 high. You will need to specify this form of printing as an option to
36000 your @sc{dvi} output program.
36002 @cindex documentation
36004 All the documentation for @value{GDBN} comes as part of the machine-readable
36005 distribution. The documentation is written in Texinfo format, which is
36006 a documentation system that uses a single source file to produce both
36007 on-line information and a printed manual. You can use one of the Info
36008 formatting commands to create the on-line version of the documentation
36009 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
36011 @value{GDBN} includes an already formatted copy of the on-line Info
36012 version of this manual in the @file{gdb} subdirectory. The main Info
36013 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
36014 subordinate files matching @samp{gdb.info*} in the same directory. If
36015 necessary, you can print out these files, or read them with any editor;
36016 but they are easier to read using the @code{info} subsystem in @sc{gnu}
36017 Emacs or the standalone @code{info} program, available as part of the
36018 @sc{gnu} Texinfo distribution.
36020 If you want to format these Info files yourself, you need one of the
36021 Info formatting programs, such as @code{texinfo-format-buffer} or
36024 If you have @code{makeinfo} installed, and are in the top level
36025 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
36026 version @value{GDBVN}), you can make the Info file by typing:
36033 If you want to typeset and print copies of this manual, you need @TeX{},
36034 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
36035 Texinfo definitions file.
36037 @TeX{} is a typesetting program; it does not print files directly, but
36038 produces output files called @sc{dvi} files. To print a typeset
36039 document, you need a program to print @sc{dvi} files. If your system
36040 has @TeX{} installed, chances are it has such a program. The precise
36041 command to use depends on your system; @kbd{lpr -d} is common; another
36042 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
36043 require a file name without any extension or a @samp{.dvi} extension.
36045 @TeX{} also requires a macro definitions file called
36046 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
36047 written in Texinfo format. On its own, @TeX{} cannot either read or
36048 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
36049 and is located in the @file{gdb-@var{version-number}/texinfo}
36052 If you have @TeX{} and a @sc{dvi} printer program installed, you can
36053 typeset and print this manual. First switch to the @file{gdb}
36054 subdirectory of the main source directory (for example, to
36055 @file{gdb-@value{GDBVN}/gdb}) and type:
36061 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
36063 @node Installing GDB
36064 @appendix Installing @value{GDBN}
36065 @cindex installation
36068 * Requirements:: Requirements for building @value{GDBN}
36069 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
36070 * Separate Objdir:: Compiling @value{GDBN} in another directory
36071 * Config Names:: Specifying names for hosts and targets
36072 * Configure Options:: Summary of options for configure
36073 * System-wide configuration:: Having a system-wide init file
36077 @section Requirements for Building @value{GDBN}
36078 @cindex building @value{GDBN}, requirements for
36080 Building @value{GDBN} requires various tools and packages to be available.
36081 Other packages will be used only if they are found.
36083 @heading Tools/Packages Necessary for Building @value{GDBN}
36085 @item ISO C90 compiler
36086 @value{GDBN} is written in ISO C90. It should be buildable with any
36087 working C90 compiler, e.g.@: GCC.
36091 @heading Tools/Packages Optional for Building @value{GDBN}
36095 @value{GDBN} can use the Expat XML parsing library. This library may be
36096 included with your operating system distribution; if it is not, you
36097 can get the latest version from @url{http://expat.sourceforge.net}.
36098 The @file{configure} script will search for this library in several
36099 standard locations; if it is installed in an unusual path, you can
36100 use the @option{--with-libexpat-prefix} option to specify its location.
36106 Remote protocol memory maps (@pxref{Memory Map Format})
36108 Target descriptions (@pxref{Target Descriptions})
36110 Remote shared library lists (@xref{Library List Format},
36111 or alternatively @pxref{Library List Format for SVR4 Targets})
36113 MS-Windows shared libraries (@pxref{Shared Libraries})
36115 Traceframe info (@pxref{Traceframe Info Format})
36117 Branch trace (@pxref{Branch Trace Format})
36121 @cindex compressed debug sections
36122 @value{GDBN} will use the @samp{zlib} library, if available, to read
36123 compressed debug sections. Some linkers, such as GNU gold, are capable
36124 of producing binaries with compressed debug sections. If @value{GDBN}
36125 is compiled with @samp{zlib}, it will be able to read the debug
36126 information in such binaries.
36128 The @samp{zlib} library is likely included with your operating system
36129 distribution; if it is not, you can get the latest version from
36130 @url{http://zlib.net}.
36133 @value{GDBN}'s features related to character sets (@pxref{Character
36134 Sets}) require a functioning @code{iconv} implementation. If you are
36135 on a GNU system, then this is provided by the GNU C Library. Some
36136 other systems also provide a working @code{iconv}.
36138 If @value{GDBN} is using the @code{iconv} program which is installed
36139 in a non-standard place, you will need to tell @value{GDBN} where to find it.
36140 This is done with @option{--with-iconv-bin} which specifies the
36141 directory that contains the @code{iconv} program.
36143 On systems without @code{iconv}, you can install GNU Libiconv. If you
36144 have previously installed Libiconv, you can use the
36145 @option{--with-libiconv-prefix} option to configure.
36147 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
36148 arrange to build Libiconv if a directory named @file{libiconv} appears
36149 in the top-most source directory. If Libiconv is built this way, and
36150 if the operating system does not provide a suitable @code{iconv}
36151 implementation, then the just-built library will automatically be used
36152 by @value{GDBN}. One easy way to set this up is to download GNU
36153 Libiconv, unpack it, and then rename the directory holding the
36154 Libiconv source code to @samp{libiconv}.
36157 @node Running Configure
36158 @section Invoking the @value{GDBN} @file{configure} Script
36159 @cindex configuring @value{GDBN}
36160 @value{GDBN} comes with a @file{configure} script that automates the process
36161 of preparing @value{GDBN} for installation; you can then use @code{make} to
36162 build the @code{gdb} program.
36164 @c irrelevant in info file; it's as current as the code it lives with.
36165 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
36166 look at the @file{README} file in the sources; we may have improved the
36167 installation procedures since publishing this manual.}
36170 The @value{GDBN} distribution includes all the source code you need for
36171 @value{GDBN} in a single directory, whose name is usually composed by
36172 appending the version number to @samp{gdb}.
36174 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
36175 @file{gdb-@value{GDBVN}} directory. That directory contains:
36178 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
36179 script for configuring @value{GDBN} and all its supporting libraries
36181 @item gdb-@value{GDBVN}/gdb
36182 the source specific to @value{GDBN} itself
36184 @item gdb-@value{GDBVN}/bfd
36185 source for the Binary File Descriptor library
36187 @item gdb-@value{GDBVN}/include
36188 @sc{gnu} include files
36190 @item gdb-@value{GDBVN}/libiberty
36191 source for the @samp{-liberty} free software library
36193 @item gdb-@value{GDBVN}/opcodes
36194 source for the library of opcode tables and disassemblers
36196 @item gdb-@value{GDBVN}/readline
36197 source for the @sc{gnu} command-line interface
36199 @item gdb-@value{GDBVN}/glob
36200 source for the @sc{gnu} filename pattern-matching subroutine
36202 @item gdb-@value{GDBVN}/mmalloc
36203 source for the @sc{gnu} memory-mapped malloc package
36206 The simplest way to configure and build @value{GDBN} is to run @file{configure}
36207 from the @file{gdb-@var{version-number}} source directory, which in
36208 this example is the @file{gdb-@value{GDBVN}} directory.
36210 First switch to the @file{gdb-@var{version-number}} source directory
36211 if you are not already in it; then run @file{configure}. Pass the
36212 identifier for the platform on which @value{GDBN} will run as an
36218 cd gdb-@value{GDBVN}
36219 ./configure @var{host}
36224 where @var{host} is an identifier such as @samp{sun4} or
36225 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
36226 (You can often leave off @var{host}; @file{configure} tries to guess the
36227 correct value by examining your system.)
36229 Running @samp{configure @var{host}} and then running @code{make} builds the
36230 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
36231 libraries, then @code{gdb} itself. The configured source files, and the
36232 binaries, are left in the corresponding source directories.
36235 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
36236 system does not recognize this automatically when you run a different
36237 shell, you may need to run @code{sh} on it explicitly:
36240 sh configure @var{host}
36243 If you run @file{configure} from a directory that contains source
36244 directories for multiple libraries or programs, such as the
36245 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
36247 creates configuration files for every directory level underneath (unless
36248 you tell it not to, with the @samp{--norecursion} option).
36250 You should run the @file{configure} script from the top directory in the
36251 source tree, the @file{gdb-@var{version-number}} directory. If you run
36252 @file{configure} from one of the subdirectories, you will configure only
36253 that subdirectory. That is usually not what you want. In particular,
36254 if you run the first @file{configure} from the @file{gdb} subdirectory
36255 of the @file{gdb-@var{version-number}} directory, you will omit the
36256 configuration of @file{bfd}, @file{readline}, and other sibling
36257 directories of the @file{gdb} subdirectory. This leads to build errors
36258 about missing include files such as @file{bfd/bfd.h}.
36260 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
36261 However, you should make sure that the shell on your path (named by
36262 the @samp{SHELL} environment variable) is publicly readable. Remember
36263 that @value{GDBN} uses the shell to start your program---some systems refuse to
36264 let @value{GDBN} debug child processes whose programs are not readable.
36266 @node Separate Objdir
36267 @section Compiling @value{GDBN} in Another Directory
36269 If you want to run @value{GDBN} versions for several host or target machines,
36270 you need a different @code{gdb} compiled for each combination of
36271 host and target. @file{configure} is designed to make this easy by
36272 allowing you to generate each configuration in a separate subdirectory,
36273 rather than in the source directory. If your @code{make} program
36274 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
36275 @code{make} in each of these directories builds the @code{gdb}
36276 program specified there.
36278 To build @code{gdb} in a separate directory, run @file{configure}
36279 with the @samp{--srcdir} option to specify where to find the source.
36280 (You also need to specify a path to find @file{configure}
36281 itself from your working directory. If the path to @file{configure}
36282 would be the same as the argument to @samp{--srcdir}, you can leave out
36283 the @samp{--srcdir} option; it is assumed.)
36285 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
36286 separate directory for a Sun 4 like this:
36290 cd gdb-@value{GDBVN}
36293 ../gdb-@value{GDBVN}/configure sun4
36298 When @file{configure} builds a configuration using a remote source
36299 directory, it creates a tree for the binaries with the same structure
36300 (and using the same names) as the tree under the source directory. In
36301 the example, you'd find the Sun 4 library @file{libiberty.a} in the
36302 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
36303 @file{gdb-sun4/gdb}.
36305 Make sure that your path to the @file{configure} script has just one
36306 instance of @file{gdb} in it. If your path to @file{configure} looks
36307 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
36308 one subdirectory of @value{GDBN}, not the whole package. This leads to
36309 build errors about missing include files such as @file{bfd/bfd.h}.
36311 One popular reason to build several @value{GDBN} configurations in separate
36312 directories is to configure @value{GDBN} for cross-compiling (where
36313 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
36314 programs that run on another machine---the @dfn{target}).
36315 You specify a cross-debugging target by
36316 giving the @samp{--target=@var{target}} option to @file{configure}.
36318 When you run @code{make} to build a program or library, you must run
36319 it in a configured directory---whatever directory you were in when you
36320 called @file{configure} (or one of its subdirectories).
36322 The @code{Makefile} that @file{configure} generates in each source
36323 directory also runs recursively. If you type @code{make} in a source
36324 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
36325 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
36326 will build all the required libraries, and then build GDB.
36328 When you have multiple hosts or targets configured in separate
36329 directories, you can run @code{make} on them in parallel (for example,
36330 if they are NFS-mounted on each of the hosts); they will not interfere
36334 @section Specifying Names for Hosts and Targets
36336 The specifications used for hosts and targets in the @file{configure}
36337 script are based on a three-part naming scheme, but some short predefined
36338 aliases are also supported. The full naming scheme encodes three pieces
36339 of information in the following pattern:
36342 @var{architecture}-@var{vendor}-@var{os}
36345 For example, you can use the alias @code{sun4} as a @var{host} argument,
36346 or as the value for @var{target} in a @code{--target=@var{target}}
36347 option. The equivalent full name is @samp{sparc-sun-sunos4}.
36349 The @file{configure} script accompanying @value{GDBN} does not provide
36350 any query facility to list all supported host and target names or
36351 aliases. @file{configure} calls the Bourne shell script
36352 @code{config.sub} to map abbreviations to full names; you can read the
36353 script, if you wish, or you can use it to test your guesses on
36354 abbreviations---for example:
36357 % sh config.sub i386-linux
36359 % sh config.sub alpha-linux
36360 alpha-unknown-linux-gnu
36361 % sh config.sub hp9k700
36363 % sh config.sub sun4
36364 sparc-sun-sunos4.1.1
36365 % sh config.sub sun3
36366 m68k-sun-sunos4.1.1
36367 % sh config.sub i986v
36368 Invalid configuration `i986v': machine `i986v' not recognized
36372 @code{config.sub} is also distributed in the @value{GDBN} source
36373 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
36375 @node Configure Options
36376 @section @file{configure} Options
36378 Here is a summary of the @file{configure} options and arguments that
36379 are most often useful for building @value{GDBN}. @file{configure} also has
36380 several other options not listed here. @inforef{What Configure
36381 Does,,configure.info}, for a full explanation of @file{configure}.
36384 configure @r{[}--help@r{]}
36385 @r{[}--prefix=@var{dir}@r{]}
36386 @r{[}--exec-prefix=@var{dir}@r{]}
36387 @r{[}--srcdir=@var{dirname}@r{]}
36388 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
36389 @r{[}--target=@var{target}@r{]}
36394 You may introduce options with a single @samp{-} rather than
36395 @samp{--} if you prefer; but you may abbreviate option names if you use
36400 Display a quick summary of how to invoke @file{configure}.
36402 @item --prefix=@var{dir}
36403 Configure the source to install programs and files under directory
36406 @item --exec-prefix=@var{dir}
36407 Configure the source to install programs under directory
36410 @c avoid splitting the warning from the explanation:
36412 @item --srcdir=@var{dirname}
36413 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
36414 @code{make} that implements the @code{VPATH} feature.}@*
36415 Use this option to make configurations in directories separate from the
36416 @value{GDBN} source directories. Among other things, you can use this to
36417 build (or maintain) several configurations simultaneously, in separate
36418 directories. @file{configure} writes configuration-specific files in
36419 the current directory, but arranges for them to use the source in the
36420 directory @var{dirname}. @file{configure} creates directories under
36421 the working directory in parallel to the source directories below
36424 @item --norecursion
36425 Configure only the directory level where @file{configure} is executed; do not
36426 propagate configuration to subdirectories.
36428 @item --target=@var{target}
36429 Configure @value{GDBN} for cross-debugging programs running on the specified
36430 @var{target}. Without this option, @value{GDBN} is configured to debug
36431 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
36433 There is no convenient way to generate a list of all available targets.
36435 @item @var{host} @dots{}
36436 Configure @value{GDBN} to run on the specified @var{host}.
36438 There is no convenient way to generate a list of all available hosts.
36441 There are many other options available as well, but they are generally
36442 needed for special purposes only.
36444 @node System-wide configuration
36445 @section System-wide configuration and settings
36446 @cindex system-wide init file
36448 @value{GDBN} can be configured to have a system-wide init file;
36449 this file will be read and executed at startup (@pxref{Startup, , What
36450 @value{GDBN} does during startup}).
36452 Here is the corresponding configure option:
36455 @item --with-system-gdbinit=@var{file}
36456 Specify that the default location of the system-wide init file is
36460 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
36461 it may be subject to relocation. Two possible cases:
36465 If the default location of this init file contains @file{$prefix},
36466 it will be subject to relocation. Suppose that the configure options
36467 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
36468 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
36469 init file is looked for as @file{$install/etc/gdbinit} instead of
36470 @file{$prefix/etc/gdbinit}.
36473 By contrast, if the default location does not contain the prefix,
36474 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
36475 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
36476 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
36477 wherever @value{GDBN} is installed.
36480 If the configured location of the system-wide init file (as given by the
36481 @option{--with-system-gdbinit} option at configure time) is in the
36482 data-directory (as specified by @option{--with-gdb-datadir} at configure
36483 time) or in one of its subdirectories, then @value{GDBN} will look for the
36484 system-wide init file in the directory specified by the
36485 @option{--data-directory} command-line option.
36486 Note that the system-wide init file is only read once, during @value{GDBN}
36487 initialization. If the data-directory is changed after @value{GDBN} has
36488 started with the @code{set data-directory} command, the file will not be
36492 * System-wide Configuration Scripts:: Installed System-wide Configuration Scripts
36495 @node System-wide Configuration Scripts
36496 @subsection Installed System-wide Configuration Scripts
36497 @cindex system-wide configuration scripts
36499 The @file{system-gdbinit} directory, located inside the data-directory
36500 (as specified by @option{--with-gdb-datadir} at configure time) contains
36501 a number of scripts which can be used as system-wide init files. To
36502 automatically source those scripts at startup, @value{GDBN} should be
36503 configured with @option{--with-system-gdbinit}. Otherwise, any user
36504 should be able to source them by hand as needed.
36506 The following scripts are currently available:
36509 @item @file{elinos.py}
36511 @cindex ELinOS system-wide configuration script
36512 This script is useful when debugging a program on an ELinOS target.
36513 It takes advantage of the environment variables defined in a standard
36514 ELinOS environment in order to determine the location of the system
36515 shared libraries, and then sets the @samp{solib-absolute-prefix}
36516 and @samp{solib-search-path} variables appropriately.
36518 @item @file{wrs-linux.py}
36519 @pindex wrs-linux.py
36520 @cindex Wind River Linux system-wide configuration script
36521 This script is useful when debugging a program on a target running
36522 Wind River Linux. It expects the @env{ENV_PREFIX} to be set to
36523 the host-side sysroot used by the target system.
36527 @node Maintenance Commands
36528 @appendix Maintenance Commands
36529 @cindex maintenance commands
36530 @cindex internal commands
36532 In addition to commands intended for @value{GDBN} users, @value{GDBN}
36533 includes a number of commands intended for @value{GDBN} developers,
36534 that are not documented elsewhere in this manual. These commands are
36535 provided here for reference. (For commands that turn on debugging
36536 messages, see @ref{Debugging Output}.)
36539 @kindex maint agent
36540 @kindex maint agent-eval
36541 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36542 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
36543 Translate the given @var{expression} into remote agent bytecodes.
36544 This command is useful for debugging the Agent Expression mechanism
36545 (@pxref{Agent Expressions}). The @samp{agent} version produces an
36546 expression useful for data collection, such as by tracepoints, while
36547 @samp{maint agent-eval} produces an expression that evaluates directly
36548 to a result. For instance, a collection expression for @code{globa +
36549 globb} will include bytecodes to record four bytes of memory at each
36550 of the addresses of @code{globa} and @code{globb}, while discarding
36551 the result of the addition, while an evaluation expression will do the
36552 addition and return the sum.
36553 If @code{-at} is given, generate remote agent bytecode for @var{location}.
36554 If not, generate remote agent bytecode for current frame PC address.
36556 @kindex maint agent-printf
36557 @item maint agent-printf @var{format},@var{expr},...
36558 Translate the given format string and list of argument expressions
36559 into remote agent bytecodes and display them as a disassembled list.
36560 This command is useful for debugging the agent version of dynamic
36561 printf (@pxref{Dynamic Printf}).
36563 @kindex maint info breakpoints
36564 @item @anchor{maint info breakpoints}maint info breakpoints
36565 Using the same format as @samp{info breakpoints}, display both the
36566 breakpoints you've set explicitly, and those @value{GDBN} is using for
36567 internal purposes. Internal breakpoints are shown with negative
36568 breakpoint numbers. The type column identifies what kind of breakpoint
36573 Normal, explicitly set breakpoint.
36576 Normal, explicitly set watchpoint.
36579 Internal breakpoint, used to handle correctly stepping through
36580 @code{longjmp} calls.
36582 @item longjmp resume
36583 Internal breakpoint at the target of a @code{longjmp}.
36586 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
36589 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
36592 Shared library events.
36596 @kindex maint info bfds
36597 @item maint info bfds
36598 This prints information about each @code{bfd} object that is known to
36599 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
36601 @kindex set displaced-stepping
36602 @kindex show displaced-stepping
36603 @cindex displaced stepping support
36604 @cindex out-of-line single-stepping
36605 @item set displaced-stepping
36606 @itemx show displaced-stepping
36607 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
36608 if the target supports it. Displaced stepping is a way to single-step
36609 over breakpoints without removing them from the inferior, by executing
36610 an out-of-line copy of the instruction that was originally at the
36611 breakpoint location. It is also known as out-of-line single-stepping.
36614 @item set displaced-stepping on
36615 If the target architecture supports it, @value{GDBN} will use
36616 displaced stepping to step over breakpoints.
36618 @item set displaced-stepping off
36619 @value{GDBN} will not use displaced stepping to step over breakpoints,
36620 even if such is supported by the target architecture.
36622 @cindex non-stop mode, and @samp{set displaced-stepping}
36623 @item set displaced-stepping auto
36624 This is the default mode. @value{GDBN} will use displaced stepping
36625 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
36626 architecture supports displaced stepping.
36629 @kindex maint check-psymtabs
36630 @item maint check-psymtabs
36631 Check the consistency of currently expanded psymtabs versus symtabs.
36632 Use this to check, for example, whether a symbol is in one but not the other.
36634 @kindex maint check-symtabs
36635 @item maint check-symtabs
36636 Check the consistency of currently expanded symtabs.
36638 @kindex maint expand-symtabs
36639 @item maint expand-symtabs [@var{regexp}]
36640 Expand symbol tables.
36641 If @var{regexp} is specified, only expand symbol tables for file
36642 names matching @var{regexp}.
36644 @kindex maint cplus first_component
36645 @item maint cplus first_component @var{name}
36646 Print the first C@t{++} class/namespace component of @var{name}.
36648 @kindex maint cplus namespace
36649 @item maint cplus namespace
36650 Print the list of possible C@t{++} namespaces.
36652 @kindex maint demangle
36653 @item maint demangle @var{name}
36654 Demangle a C@t{++} or Objective-C mangled @var{name}.
36656 @kindex maint deprecate
36657 @kindex maint undeprecate
36658 @cindex deprecated commands
36659 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
36660 @itemx maint undeprecate @var{command}
36661 Deprecate or undeprecate the named @var{command}. Deprecated commands
36662 cause @value{GDBN} to issue a warning when you use them. The optional
36663 argument @var{replacement} says which newer command should be used in
36664 favor of the deprecated one; if it is given, @value{GDBN} will mention
36665 the replacement as part of the warning.
36667 @kindex maint dump-me
36668 @item maint dump-me
36669 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
36670 Cause a fatal signal in the debugger and force it to dump its core.
36671 This is supported only on systems which support aborting a program
36672 with the @code{SIGQUIT} signal.
36674 @kindex maint internal-error
36675 @kindex maint internal-warning
36676 @item maint internal-error @r{[}@var{message-text}@r{]}
36677 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
36678 Cause @value{GDBN} to call the internal function @code{internal_error}
36679 or @code{internal_warning} and hence behave as though an internal error
36680 or internal warning has been detected. In addition to reporting the
36681 internal problem, these functions give the user the opportunity to
36682 either quit @value{GDBN} or create a core file of the current
36683 @value{GDBN} session.
36685 These commands take an optional parameter @var{message-text} that is
36686 used as the text of the error or warning message.
36688 Here's an example of using @code{internal-error}:
36691 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
36692 @dots{}/maint.c:121: internal-error: testing, 1, 2
36693 A problem internal to GDB has been detected. Further
36694 debugging may prove unreliable.
36695 Quit this debugging session? (y or n) @kbd{n}
36696 Create a core file? (y or n) @kbd{n}
36700 @cindex @value{GDBN} internal error
36701 @cindex internal errors, control of @value{GDBN} behavior
36703 @kindex maint set internal-error
36704 @kindex maint show internal-error
36705 @kindex maint set internal-warning
36706 @kindex maint show internal-warning
36707 @item maint set internal-error @var{action} [ask|yes|no]
36708 @itemx maint show internal-error @var{action}
36709 @itemx maint set internal-warning @var{action} [ask|yes|no]
36710 @itemx maint show internal-warning @var{action}
36711 When @value{GDBN} reports an internal problem (error or warning) it
36712 gives the user the opportunity to both quit @value{GDBN} and create a
36713 core file of the current @value{GDBN} session. These commands let you
36714 override the default behaviour for each particular @var{action},
36715 described in the table below.
36719 You can specify that @value{GDBN} should always (yes) or never (no)
36720 quit. The default is to ask the user what to do.
36723 You can specify that @value{GDBN} should always (yes) or never (no)
36724 create a core file. The default is to ask the user what to do.
36727 @kindex maint packet
36728 @item maint packet @var{text}
36729 If @value{GDBN} is talking to an inferior via the serial protocol,
36730 then this command sends the string @var{text} to the inferior, and
36731 displays the response packet. @value{GDBN} supplies the initial
36732 @samp{$} character, the terminating @samp{#} character, and the
36735 @kindex maint print architecture
36736 @item maint print architecture @r{[}@var{file}@r{]}
36737 Print the entire architecture configuration. The optional argument
36738 @var{file} names the file where the output goes.
36740 @kindex maint print c-tdesc
36741 @item maint print c-tdesc
36742 Print the current target description (@pxref{Target Descriptions}) as
36743 a C source file. The created source file can be used in @value{GDBN}
36744 when an XML parser is not available to parse the description.
36746 @kindex maint print dummy-frames
36747 @item maint print dummy-frames
36748 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
36751 (@value{GDBP}) @kbd{b add}
36753 (@value{GDBP}) @kbd{print add(2,3)}
36754 Breakpoint 2, add (a=2, b=3) at @dots{}
36756 The program being debugged stopped while in a function called from GDB.
36758 (@value{GDBP}) @kbd{maint print dummy-frames}
36759 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
36760 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
36761 call_lo=0x01014000 call_hi=0x01014001
36765 Takes an optional file parameter.
36767 @kindex maint print registers
36768 @kindex maint print raw-registers
36769 @kindex maint print cooked-registers
36770 @kindex maint print register-groups
36771 @kindex maint print remote-registers
36772 @item maint print registers @r{[}@var{file}@r{]}
36773 @itemx maint print raw-registers @r{[}@var{file}@r{]}
36774 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
36775 @itemx maint print register-groups @r{[}@var{file}@r{]}
36776 @itemx maint print remote-registers @r{[}@var{file}@r{]}
36777 Print @value{GDBN}'s internal register data structures.
36779 The command @code{maint print raw-registers} includes the contents of
36780 the raw register cache; the command @code{maint print
36781 cooked-registers} includes the (cooked) value of all registers,
36782 including registers which aren't available on the target nor visible
36783 to user; the command @code{maint print register-groups} includes the
36784 groups that each register is a member of; and the command @code{maint
36785 print remote-registers} includes the remote target's register numbers
36786 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
36787 @value{GDBN} Internals}.
36789 These commands take an optional parameter, a file name to which to
36790 write the information.
36792 @kindex maint print reggroups
36793 @item maint print reggroups @r{[}@var{file}@r{]}
36794 Print @value{GDBN}'s internal register group data structures. The
36795 optional argument @var{file} tells to what file to write the
36798 The register groups info looks like this:
36801 (@value{GDBP}) @kbd{maint print reggroups}
36814 This command forces @value{GDBN} to flush its internal register cache.
36816 @kindex maint print objfiles
36817 @cindex info for known object files
36818 @item maint print objfiles
36819 Print a dump of all known object files. For each object file, this
36820 command prints its name, address in memory, and all of its psymtabs
36823 @kindex maint print section-scripts
36824 @cindex info for known .debug_gdb_scripts-loaded scripts
36825 @item maint print section-scripts [@var{regexp}]
36826 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
36827 If @var{regexp} is specified, only print scripts loaded by object files
36828 matching @var{regexp}.
36829 For each script, this command prints its name as specified in the objfile,
36830 and the full path if known.
36831 @xref{dotdebug_gdb_scripts section}.
36833 @kindex maint print statistics
36834 @cindex bcache statistics
36835 @item maint print statistics
36836 This command prints, for each object file in the program, various data
36837 about that object file followed by the byte cache (@dfn{bcache})
36838 statistics for the object file. The objfile data includes the number
36839 of minimal, partial, full, and stabs symbols, the number of types
36840 defined by the objfile, the number of as yet unexpanded psym tables,
36841 the number of line tables and string tables, and the amount of memory
36842 used by the various tables. The bcache statistics include the counts,
36843 sizes, and counts of duplicates of all and unique objects, max,
36844 average, and median entry size, total memory used and its overhead and
36845 savings, and various measures of the hash table size and chain
36848 @kindex maint print target-stack
36849 @cindex target stack description
36850 @item maint print target-stack
36851 A @dfn{target} is an interface between the debugger and a particular
36852 kind of file or process. Targets can be stacked in @dfn{strata},
36853 so that more than one target can potentially respond to a request.
36854 In particular, memory accesses will walk down the stack of targets
36855 until they find a target that is interested in handling that particular
36858 This command prints a short description of each layer that was pushed on
36859 the @dfn{target stack}, starting from the top layer down to the bottom one.
36861 @kindex maint print type
36862 @cindex type chain of a data type
36863 @item maint print type @var{expr}
36864 Print the type chain for a type specified by @var{expr}. The argument
36865 can be either a type name or a symbol. If it is a symbol, the type of
36866 that symbol is described. The type chain produced by this command is
36867 a recursive definition of the data type as stored in @value{GDBN}'s
36868 data structures, including its flags and contained types.
36870 @kindex maint set dwarf2 always-disassemble
36871 @kindex maint show dwarf2 always-disassemble
36872 @item maint set dwarf2 always-disassemble
36873 @item maint show dwarf2 always-disassemble
36874 Control the behavior of @code{info address} when using DWARF debugging
36877 The default is @code{off}, which means that @value{GDBN} should try to
36878 describe a variable's location in an easily readable format. When
36879 @code{on}, @value{GDBN} will instead display the DWARF location
36880 expression in an assembly-like format. Note that some locations are
36881 too complex for @value{GDBN} to describe simply; in this case you will
36882 always see the disassembly form.
36884 Here is an example of the resulting disassembly:
36887 (gdb) info addr argc
36888 Symbol "argc" is a complex DWARF expression:
36892 For more information on these expressions, see
36893 @uref{http://www.dwarfstd.org/, the DWARF standard}.
36895 @kindex maint set dwarf2 max-cache-age
36896 @kindex maint show dwarf2 max-cache-age
36897 @item maint set dwarf2 max-cache-age
36898 @itemx maint show dwarf2 max-cache-age
36899 Control the DWARF 2 compilation unit cache.
36901 @cindex DWARF 2 compilation units cache
36902 In object files with inter-compilation-unit references, such as those
36903 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
36904 reader needs to frequently refer to previously read compilation units.
36905 This setting controls how long a compilation unit will remain in the
36906 cache if it is not referenced. A higher limit means that cached
36907 compilation units will be stored in memory longer, and more total
36908 memory will be used. Setting it to zero disables caching, which will
36909 slow down @value{GDBN} startup, but reduce memory consumption.
36911 @kindex maint set profile
36912 @kindex maint show profile
36913 @cindex profiling GDB
36914 @item maint set profile
36915 @itemx maint show profile
36916 Control profiling of @value{GDBN}.
36918 Profiling will be disabled until you use the @samp{maint set profile}
36919 command to enable it. When you enable profiling, the system will begin
36920 collecting timing and execution count data; when you disable profiling or
36921 exit @value{GDBN}, the results will be written to a log file. Remember that
36922 if you use profiling, @value{GDBN} will overwrite the profiling log file
36923 (often called @file{gmon.out}). If you have a record of important profiling
36924 data in a @file{gmon.out} file, be sure to move it to a safe location.
36926 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
36927 compiled with the @samp{-pg} compiler option.
36929 @kindex maint set show-debug-regs
36930 @kindex maint show show-debug-regs
36931 @cindex hardware debug registers
36932 @item maint set show-debug-regs
36933 @itemx maint show show-debug-regs
36934 Control whether to show variables that mirror the hardware debug
36935 registers. Use @code{ON} to enable, @code{OFF} to disable. If
36936 enabled, the debug registers values are shown when @value{GDBN} inserts or
36937 removes a hardware breakpoint or watchpoint, and when the inferior
36938 triggers a hardware-assisted breakpoint or watchpoint.
36940 @kindex maint set show-all-tib
36941 @kindex maint show show-all-tib
36942 @item maint set show-all-tib
36943 @itemx maint show show-all-tib
36944 Control whether to show all non zero areas within a 1k block starting
36945 at thread local base, when using the @samp{info w32 thread-information-block}
36948 @kindex maint set per-command
36949 @kindex maint show per-command
36950 @item maint set per-command
36951 @itemx maint show per-command
36952 @cindex resources used by commands
36954 @value{GDBN} can display the resources used by each command.
36955 This is useful in debugging performance problems.
36958 @item maint set per-command space [on|off]
36959 @itemx maint show per-command space
36960 Enable or disable the printing of the memory used by GDB for each command.
36961 If enabled, @value{GDBN} will display how much memory each command
36962 took, following the command's own output.
36963 This can also be requested by invoking @value{GDBN} with the
36964 @option{--statistics} command-line switch (@pxref{Mode Options}).
36966 @item maint set per-command time [on|off]
36967 @itemx maint show per-command time
36968 Enable or disable the printing of the execution time of @value{GDBN}
36970 If enabled, @value{GDBN} will display how much time it
36971 took to execute each command, following the command's own output.
36972 Both CPU time and wallclock time are printed.
36973 Printing both is useful when trying to determine whether the cost is
36974 CPU or, e.g., disk/network latency.
36975 Note that the CPU time printed is for @value{GDBN} only, it does not include
36976 the execution time of the inferior because there's no mechanism currently
36977 to compute how much time was spent by @value{GDBN} and how much time was
36978 spent by the program been debugged.
36979 This can also be requested by invoking @value{GDBN} with the
36980 @option{--statistics} command-line switch (@pxref{Mode Options}).
36982 @item maint set per-command symtab [on|off]
36983 @itemx maint show per-command symtab
36984 Enable or disable the printing of basic symbol table statistics
36986 If enabled, @value{GDBN} will display the following information:
36990 number of symbol tables
36992 number of primary symbol tables
36994 number of blocks in the blockvector
36998 @kindex maint space
36999 @cindex memory used by commands
37000 @item maint space @var{value}
37001 An alias for @code{maint set per-command space}.
37002 A non-zero value enables it, zero disables it.
37005 @cindex time of command execution
37006 @item maint time @var{value}
37007 An alias for @code{maint set per-command time}.
37008 A non-zero value enables it, zero disables it.
37010 @kindex maint translate-address
37011 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
37012 Find the symbol stored at the location specified by the address
37013 @var{addr} and an optional section name @var{section}. If found,
37014 @value{GDBN} prints the name of the closest symbol and an offset from
37015 the symbol's location to the specified address. This is similar to
37016 the @code{info address} command (@pxref{Symbols}), except that this
37017 command also allows to find symbols in other sections.
37019 If section was not specified, the section in which the symbol was found
37020 is also printed. For dynamically linked executables, the name of
37021 executable or shared library containing the symbol is printed as well.
37025 The following command is useful for non-interactive invocations of
37026 @value{GDBN}, such as in the test suite.
37029 @item set watchdog @var{nsec}
37030 @kindex set watchdog
37031 @cindex watchdog timer
37032 @cindex timeout for commands
37033 Set the maximum number of seconds @value{GDBN} will wait for the
37034 target operation to finish. If this time expires, @value{GDBN}
37035 reports and error and the command is aborted.
37037 @item show watchdog
37038 Show the current setting of the target wait timeout.
37041 @node Remote Protocol
37042 @appendix @value{GDBN} Remote Serial Protocol
37047 * Stop Reply Packets::
37048 * General Query Packets::
37049 * Architecture-Specific Protocol Details::
37050 * Tracepoint Packets::
37051 * Host I/O Packets::
37053 * Notification Packets::
37054 * Remote Non-Stop::
37055 * Packet Acknowledgment::
37057 * File-I/O Remote Protocol Extension::
37058 * Library List Format::
37059 * Library List Format for SVR4 Targets::
37060 * Memory Map Format::
37061 * Thread List Format::
37062 * Traceframe Info Format::
37063 * Branch Trace Format::
37069 There may be occasions when you need to know something about the
37070 protocol---for example, if there is only one serial port to your target
37071 machine, you might want your program to do something special if it
37072 recognizes a packet meant for @value{GDBN}.
37074 In the examples below, @samp{->} and @samp{<-} are used to indicate
37075 transmitted and received data, respectively.
37077 @cindex protocol, @value{GDBN} remote serial
37078 @cindex serial protocol, @value{GDBN} remote
37079 @cindex remote serial protocol
37080 All @value{GDBN} commands and responses (other than acknowledgments
37081 and notifications, see @ref{Notification Packets}) are sent as a
37082 @var{packet}. A @var{packet} is introduced with the character
37083 @samp{$}, the actual @var{packet-data}, and the terminating character
37084 @samp{#} followed by a two-digit @var{checksum}:
37087 @code{$}@var{packet-data}@code{#}@var{checksum}
37091 @cindex checksum, for @value{GDBN} remote
37093 The two-digit @var{checksum} is computed as the modulo 256 sum of all
37094 characters between the leading @samp{$} and the trailing @samp{#} (an
37095 eight bit unsigned checksum).
37097 Implementors should note that prior to @value{GDBN} 5.0 the protocol
37098 specification also included an optional two-digit @var{sequence-id}:
37101 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
37104 @cindex sequence-id, for @value{GDBN} remote
37106 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
37107 has never output @var{sequence-id}s. Stubs that handle packets added
37108 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
37110 When either the host or the target machine receives a packet, the first
37111 response expected is an acknowledgment: either @samp{+} (to indicate
37112 the package was received correctly) or @samp{-} (to request
37116 -> @code{$}@var{packet-data}@code{#}@var{checksum}
37121 The @samp{+}/@samp{-} acknowledgments can be disabled
37122 once a connection is established.
37123 @xref{Packet Acknowledgment}, for details.
37125 The host (@value{GDBN}) sends @var{command}s, and the target (the
37126 debugging stub incorporated in your program) sends a @var{response}. In
37127 the case of step and continue @var{command}s, the response is only sent
37128 when the operation has completed, and the target has again stopped all
37129 threads in all attached processes. This is the default all-stop mode
37130 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
37131 execution mode; see @ref{Remote Non-Stop}, for details.
37133 @var{packet-data} consists of a sequence of characters with the
37134 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
37137 @cindex remote protocol, field separator
37138 Fields within the packet should be separated using @samp{,} @samp{;} or
37139 @samp{:}. Except where otherwise noted all numbers are represented in
37140 @sc{hex} with leading zeros suppressed.
37142 Implementors should note that prior to @value{GDBN} 5.0, the character
37143 @samp{:} could not appear as the third character in a packet (as it
37144 would potentially conflict with the @var{sequence-id}).
37146 @cindex remote protocol, binary data
37147 @anchor{Binary Data}
37148 Binary data in most packets is encoded either as two hexadecimal
37149 digits per byte of binary data. This allowed the traditional remote
37150 protocol to work over connections which were only seven-bit clean.
37151 Some packets designed more recently assume an eight-bit clean
37152 connection, and use a more efficient encoding to send and receive
37155 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
37156 as an escape character. Any escaped byte is transmitted as the escape
37157 character followed by the original character XORed with @code{0x20}.
37158 For example, the byte @code{0x7d} would be transmitted as the two
37159 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
37160 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
37161 @samp{@}}) must always be escaped. Responses sent by the stub
37162 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
37163 is not interpreted as the start of a run-length encoded sequence
37166 Response @var{data} can be run-length encoded to save space.
37167 Run-length encoding replaces runs of identical characters with one
37168 instance of the repeated character, followed by a @samp{*} and a
37169 repeat count. The repeat count is itself sent encoded, to avoid
37170 binary characters in @var{data}: a value of @var{n} is sent as
37171 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
37172 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
37173 code 32) for a repeat count of 3. (This is because run-length
37174 encoding starts to win for counts 3 or more.) Thus, for example,
37175 @samp{0* } is a run-length encoding of ``0000'': the space character
37176 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
37179 The printable characters @samp{#} and @samp{$} or with a numeric value
37180 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
37181 seven repeats (@samp{$}) can be expanded using a repeat count of only
37182 five (@samp{"}). For example, @samp{00000000} can be encoded as
37185 The error response returned for some packets includes a two character
37186 error number. That number is not well defined.
37188 @cindex empty response, for unsupported packets
37189 For any @var{command} not supported by the stub, an empty response
37190 (@samp{$#00}) should be returned. That way it is possible to extend the
37191 protocol. A newer @value{GDBN} can tell if a packet is supported based
37194 At a minimum, a stub is required to support the @samp{g} and @samp{G}
37195 commands for register access, and the @samp{m} and @samp{M} commands
37196 for memory access. Stubs that only control single-threaded targets
37197 can implement run control with the @samp{c} (continue), and @samp{s}
37198 (step) commands. Stubs that support multi-threading targets should
37199 support the @samp{vCont} command. All other commands are optional.
37204 The following table provides a complete list of all currently defined
37205 @var{command}s and their corresponding response @var{data}.
37206 @xref{File-I/O Remote Protocol Extension}, for details about the File
37207 I/O extension of the remote protocol.
37209 Each packet's description has a template showing the packet's overall
37210 syntax, followed by an explanation of the packet's meaning. We
37211 include spaces in some of the templates for clarity; these are not
37212 part of the packet's syntax. No @value{GDBN} packet uses spaces to
37213 separate its components. For example, a template like @samp{foo
37214 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
37215 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
37216 @var{baz}. @value{GDBN} does not transmit a space character between the
37217 @samp{foo} and the @var{bar}, or between the @var{bar} and the
37220 @cindex @var{thread-id}, in remote protocol
37221 @anchor{thread-id syntax}
37222 Several packets and replies include a @var{thread-id} field to identify
37223 a thread. Normally these are positive numbers with a target-specific
37224 interpretation, formatted as big-endian hex strings. A @var{thread-id}
37225 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
37228 In addition, the remote protocol supports a multiprocess feature in
37229 which the @var{thread-id} syntax is extended to optionally include both
37230 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
37231 The @var{pid} (process) and @var{tid} (thread) components each have the
37232 format described above: a positive number with target-specific
37233 interpretation formatted as a big-endian hex string, literal @samp{-1}
37234 to indicate all processes or threads (respectively), or @samp{0} to
37235 indicate an arbitrary process or thread. Specifying just a process, as
37236 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
37237 error to specify all processes but a specific thread, such as
37238 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
37239 for those packets and replies explicitly documented to include a process
37240 ID, rather than a @var{thread-id}.
37242 The multiprocess @var{thread-id} syntax extensions are only used if both
37243 @value{GDBN} and the stub report support for the @samp{multiprocess}
37244 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
37247 Note that all packet forms beginning with an upper- or lower-case
37248 letter, other than those described here, are reserved for future use.
37250 Here are the packet descriptions.
37255 @cindex @samp{!} packet
37256 @anchor{extended mode}
37257 Enable extended mode. In extended mode, the remote server is made
37258 persistent. The @samp{R} packet is used to restart the program being
37264 The remote target both supports and has enabled extended mode.
37268 @cindex @samp{?} packet
37269 Indicate the reason the target halted. The reply is the same as for
37270 step and continue. This packet has a special interpretation when the
37271 target is in non-stop mode; see @ref{Remote Non-Stop}.
37274 @xref{Stop Reply Packets}, for the reply specifications.
37276 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
37277 @cindex @samp{A} packet
37278 Initialized @code{argv[]} array passed into program. @var{arglen}
37279 specifies the number of bytes in the hex encoded byte stream
37280 @var{arg}. See @code{gdbserver} for more details.
37285 The arguments were set.
37291 @cindex @samp{b} packet
37292 (Don't use this packet; its behavior is not well-defined.)
37293 Change the serial line speed to @var{baud}.
37295 JTC: @emph{When does the transport layer state change? When it's
37296 received, or after the ACK is transmitted. In either case, there are
37297 problems if the command or the acknowledgment packet is dropped.}
37299 Stan: @emph{If people really wanted to add something like this, and get
37300 it working for the first time, they ought to modify ser-unix.c to send
37301 some kind of out-of-band message to a specially-setup stub and have the
37302 switch happen "in between" packets, so that from remote protocol's point
37303 of view, nothing actually happened.}
37305 @item B @var{addr},@var{mode}
37306 @cindex @samp{B} packet
37307 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
37308 breakpoint at @var{addr}.
37310 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
37311 (@pxref{insert breakpoint or watchpoint packet}).
37313 @cindex @samp{bc} packet
37316 Backward continue. Execute the target system in reverse. No parameter.
37317 @xref{Reverse Execution}, for more information.
37320 @xref{Stop Reply Packets}, for the reply specifications.
37322 @cindex @samp{bs} packet
37325 Backward single step. Execute one instruction in reverse. No parameter.
37326 @xref{Reverse Execution}, for more information.
37329 @xref{Stop Reply Packets}, for the reply specifications.
37331 @item c @r{[}@var{addr}@r{]}
37332 @cindex @samp{c} packet
37333 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
37334 resume at current address.
37336 This packet is deprecated for multi-threading support. @xref{vCont
37340 @xref{Stop Reply Packets}, for the reply specifications.
37342 @item C @var{sig}@r{[};@var{addr}@r{]}
37343 @cindex @samp{C} packet
37344 Continue with signal @var{sig} (hex signal number). If
37345 @samp{;@var{addr}} is omitted, resume at same address.
37347 This packet is deprecated for multi-threading support. @xref{vCont
37351 @xref{Stop Reply Packets}, for the reply specifications.
37354 @cindex @samp{d} packet
37357 Don't use this packet; instead, define a general set packet
37358 (@pxref{General Query Packets}).
37362 @cindex @samp{D} packet
37363 The first form of the packet is used to detach @value{GDBN} from the
37364 remote system. It is sent to the remote target
37365 before @value{GDBN} disconnects via the @code{detach} command.
37367 The second form, including a process ID, is used when multiprocess
37368 protocol extensions are enabled (@pxref{multiprocess extensions}), to
37369 detach only a specific process. The @var{pid} is specified as a
37370 big-endian hex string.
37380 @item F @var{RC},@var{EE},@var{CF};@var{XX}
37381 @cindex @samp{F} packet
37382 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
37383 This is part of the File-I/O protocol extension. @xref{File-I/O
37384 Remote Protocol Extension}, for the specification.
37387 @anchor{read registers packet}
37388 @cindex @samp{g} packet
37389 Read general registers.
37393 @item @var{XX@dots{}}
37394 Each byte of register data is described by two hex digits. The bytes
37395 with the register are transmitted in target byte order. The size of
37396 each register and their position within the @samp{g} packet are
37397 determined by the @value{GDBN} internal gdbarch functions
37398 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
37399 specification of several standard @samp{g} packets is specified below.
37401 When reading registers from a trace frame (@pxref{Analyze Collected
37402 Data,,Using the Collected Data}), the stub may also return a string of
37403 literal @samp{x}'s in place of the register data digits, to indicate
37404 that the corresponding register has not been collected, thus its value
37405 is unavailable. For example, for an architecture with 4 registers of
37406 4 bytes each, the following reply indicates to @value{GDBN} that
37407 registers 0 and 2 have not been collected, while registers 1 and 3
37408 have been collected, and both have zero value:
37412 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
37419 @item G @var{XX@dots{}}
37420 @cindex @samp{G} packet
37421 Write general registers. @xref{read registers packet}, for a
37422 description of the @var{XX@dots{}} data.
37432 @item H @var{op} @var{thread-id}
37433 @cindex @samp{H} packet
37434 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
37435 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
37436 it should be @samp{c} for step and continue operations (note that this
37437 is deprecated, supporting the @samp{vCont} command is a better
37438 option), @samp{g} for other operations. The thread designator
37439 @var{thread-id} has the format and interpretation described in
37440 @ref{thread-id syntax}.
37451 @c 'H': How restrictive (or permissive) is the thread model. If a
37452 @c thread is selected and stopped, are other threads allowed
37453 @c to continue to execute? As I mentioned above, I think the
37454 @c semantics of each command when a thread is selected must be
37455 @c described. For example:
37457 @c 'g': If the stub supports threads and a specific thread is
37458 @c selected, returns the register block from that thread;
37459 @c otherwise returns current registers.
37461 @c 'G' If the stub supports threads and a specific thread is
37462 @c selected, sets the registers of the register block of
37463 @c that thread; otherwise sets current registers.
37465 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
37466 @anchor{cycle step packet}
37467 @cindex @samp{i} packet
37468 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
37469 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
37470 step starting at that address.
37473 @cindex @samp{I} packet
37474 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
37478 @cindex @samp{k} packet
37481 FIXME: @emph{There is no description of how to operate when a specific
37482 thread context has been selected (i.e.@: does 'k' kill only that
37485 @item m @var{addr},@var{length}
37486 @cindex @samp{m} packet
37487 Read @var{length} bytes of memory starting at address @var{addr}.
37488 Note that @var{addr} may not be aligned to any particular boundary.
37490 The stub need not use any particular size or alignment when gathering
37491 data from memory for the response; even if @var{addr} is word-aligned
37492 and @var{length} is a multiple of the word size, the stub is free to
37493 use byte accesses, or not. For this reason, this packet may not be
37494 suitable for accessing memory-mapped I/O devices.
37495 @cindex alignment of remote memory accesses
37496 @cindex size of remote memory accesses
37497 @cindex memory, alignment and size of remote accesses
37501 @item @var{XX@dots{}}
37502 Memory contents; each byte is transmitted as a two-digit hexadecimal
37503 number. The reply may contain fewer bytes than requested if the
37504 server was able to read only part of the region of memory.
37509 @item M @var{addr},@var{length}:@var{XX@dots{}}
37510 @cindex @samp{M} packet
37511 Write @var{length} bytes of memory starting at address @var{addr}.
37512 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
37513 hexadecimal number.
37520 for an error (this includes the case where only part of the data was
37525 @cindex @samp{p} packet
37526 Read the value of register @var{n}; @var{n} is in hex.
37527 @xref{read registers packet}, for a description of how the returned
37528 register value is encoded.
37532 @item @var{XX@dots{}}
37533 the register's value
37537 Indicating an unrecognized @var{query}.
37540 @item P @var{n@dots{}}=@var{r@dots{}}
37541 @anchor{write register packet}
37542 @cindex @samp{P} packet
37543 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
37544 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
37545 digits for each byte in the register (target byte order).
37555 @item q @var{name} @var{params}@dots{}
37556 @itemx Q @var{name} @var{params}@dots{}
37557 @cindex @samp{q} packet
37558 @cindex @samp{Q} packet
37559 General query (@samp{q}) and set (@samp{Q}). These packets are
37560 described fully in @ref{General Query Packets}.
37563 @cindex @samp{r} packet
37564 Reset the entire system.
37566 Don't use this packet; use the @samp{R} packet instead.
37569 @cindex @samp{R} packet
37570 Restart the program being debugged. @var{XX}, while needed, is ignored.
37571 This packet is only available in extended mode (@pxref{extended mode}).
37573 The @samp{R} packet has no reply.
37575 @item s @r{[}@var{addr}@r{]}
37576 @cindex @samp{s} packet
37577 Single step. @var{addr} is the address at which to resume. If
37578 @var{addr} is omitted, resume at same address.
37580 This packet is deprecated for multi-threading support. @xref{vCont
37584 @xref{Stop Reply Packets}, for the reply specifications.
37586 @item S @var{sig}@r{[};@var{addr}@r{]}
37587 @anchor{step with signal packet}
37588 @cindex @samp{S} packet
37589 Step with signal. This is analogous to the @samp{C} packet, but
37590 requests a single-step, rather than a normal resumption of execution.
37592 This packet is deprecated for multi-threading support. @xref{vCont
37596 @xref{Stop Reply Packets}, for the reply specifications.
37598 @item t @var{addr}:@var{PP},@var{MM}
37599 @cindex @samp{t} packet
37600 Search backwards starting at address @var{addr} for a match with pattern
37601 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
37602 @var{addr} must be at least 3 digits.
37604 @item T @var{thread-id}
37605 @cindex @samp{T} packet
37606 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
37611 thread is still alive
37617 Packets starting with @samp{v} are identified by a multi-letter name,
37618 up to the first @samp{;} or @samp{?} (or the end of the packet).
37620 @item vAttach;@var{pid}
37621 @cindex @samp{vAttach} packet
37622 Attach to a new process with the specified process ID @var{pid}.
37623 The process ID is a
37624 hexadecimal integer identifying the process. In all-stop mode, all
37625 threads in the attached process are stopped; in non-stop mode, it may be
37626 attached without being stopped if that is supported by the target.
37628 @c In non-stop mode, on a successful vAttach, the stub should set the
37629 @c current thread to a thread of the newly-attached process. After
37630 @c attaching, GDB queries for the attached process's thread ID with qC.
37631 @c Also note that, from a user perspective, whether or not the
37632 @c target is stopped on attach in non-stop mode depends on whether you
37633 @c use the foreground or background version of the attach command, not
37634 @c on what vAttach does; GDB does the right thing with respect to either
37635 @c stopping or restarting threads.
37637 This packet is only available in extended mode (@pxref{extended mode}).
37643 @item @r{Any stop packet}
37644 for success in all-stop mode (@pxref{Stop Reply Packets})
37646 for success in non-stop mode (@pxref{Remote Non-Stop})
37649 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
37650 @cindex @samp{vCont} packet
37651 @anchor{vCont packet}
37652 Resume the inferior, specifying different actions for each thread.
37653 If an action is specified with no @var{thread-id}, then it is applied to any
37654 threads that don't have a specific action specified; if no default action is
37655 specified then other threads should remain stopped in all-stop mode and
37656 in their current state in non-stop mode.
37657 Specifying multiple
37658 default actions is an error; specifying no actions is also an error.
37659 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
37661 Currently supported actions are:
37667 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
37671 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
37674 @item r @var{start},@var{end}
37675 Step once, and then keep stepping as long as the thread stops at
37676 addresses between @var{start} (inclusive) and @var{end} (exclusive).
37677 The remote stub reports a stop reply when either the thread goes out
37678 of the range or is stopped due to an unrelated reason, such as hitting
37679 a breakpoint. @xref{range stepping}.
37681 If the range is empty (@var{start} == @var{end}), then the action
37682 becomes equivalent to the @samp{s} action. In other words,
37683 single-step once, and report the stop (even if the stepped instruction
37684 jumps to @var{start}).
37686 (A stop reply may be sent at any point even if the PC is still within
37687 the stepping range; for example, it is valid to implement this packet
37688 in a degenerate way as a single instruction step operation.)
37692 The optional argument @var{addr} normally associated with the
37693 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
37694 not supported in @samp{vCont}.
37696 The @samp{t} action is only relevant in non-stop mode
37697 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
37698 A stop reply should be generated for any affected thread not already stopped.
37699 When a thread is stopped by means of a @samp{t} action,
37700 the corresponding stop reply should indicate that the thread has stopped with
37701 signal @samp{0}, regardless of whether the target uses some other signal
37702 as an implementation detail.
37704 The stub must support @samp{vCont} if it reports support for
37705 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
37706 this case @samp{vCont} actions can be specified to apply to all threads
37707 in a process by using the @samp{p@var{pid}.-1} form of the
37711 @xref{Stop Reply Packets}, for the reply specifications.
37714 @cindex @samp{vCont?} packet
37715 Request a list of actions supported by the @samp{vCont} packet.
37719 @item vCont@r{[};@var{action}@dots{}@r{]}
37720 The @samp{vCont} packet is supported. Each @var{action} is a supported
37721 command in the @samp{vCont} packet.
37723 The @samp{vCont} packet is not supported.
37726 @item vFile:@var{operation}:@var{parameter}@dots{}
37727 @cindex @samp{vFile} packet
37728 Perform a file operation on the target system. For details,
37729 see @ref{Host I/O Packets}.
37731 @item vFlashErase:@var{addr},@var{length}
37732 @cindex @samp{vFlashErase} packet
37733 Direct the stub to erase @var{length} bytes of flash starting at
37734 @var{addr}. The region may enclose any number of flash blocks, but
37735 its start and end must fall on block boundaries, as indicated by the
37736 flash block size appearing in the memory map (@pxref{Memory Map
37737 Format}). @value{GDBN} groups flash memory programming operations
37738 together, and sends a @samp{vFlashDone} request after each group; the
37739 stub is allowed to delay erase operation until the @samp{vFlashDone}
37740 packet is received.
37750 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
37751 @cindex @samp{vFlashWrite} packet
37752 Direct the stub to write data to flash address @var{addr}. The data
37753 is passed in binary form using the same encoding as for the @samp{X}
37754 packet (@pxref{Binary Data}). The memory ranges specified by
37755 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
37756 not overlap, and must appear in order of increasing addresses
37757 (although @samp{vFlashErase} packets for higher addresses may already
37758 have been received; the ordering is guaranteed only between
37759 @samp{vFlashWrite} packets). If a packet writes to an address that was
37760 neither erased by a preceding @samp{vFlashErase} packet nor by some other
37761 target-specific method, the results are unpredictable.
37769 for vFlashWrite addressing non-flash memory
37775 @cindex @samp{vFlashDone} packet
37776 Indicate to the stub that flash programming operation is finished.
37777 The stub is permitted to delay or batch the effects of a group of
37778 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
37779 @samp{vFlashDone} packet is received. The contents of the affected
37780 regions of flash memory are unpredictable until the @samp{vFlashDone}
37781 request is completed.
37783 @item vKill;@var{pid}
37784 @cindex @samp{vKill} packet
37785 Kill the process with the specified process ID. @var{pid} is a
37786 hexadecimal integer identifying the process. This packet is used in
37787 preference to @samp{k} when multiprocess protocol extensions are
37788 supported; see @ref{multiprocess extensions}.
37798 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
37799 @cindex @samp{vRun} packet
37800 Run the program @var{filename}, passing it each @var{argument} on its
37801 command line. The file and arguments are hex-encoded strings. If
37802 @var{filename} is an empty string, the stub may use a default program
37803 (e.g.@: the last program run). The program is created in the stopped
37806 @c FIXME: What about non-stop mode?
37808 This packet is only available in extended mode (@pxref{extended mode}).
37814 @item @r{Any stop packet}
37815 for success (@pxref{Stop Reply Packets})
37819 @cindex @samp{vStopped} packet
37820 @xref{Notification Packets}.
37822 @item X @var{addr},@var{length}:@var{XX@dots{}}
37824 @cindex @samp{X} packet
37825 Write data to memory, where the data is transmitted in binary.
37826 @var{addr} is address, @var{length} is number of bytes,
37827 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
37837 @item z @var{type},@var{addr},@var{kind}
37838 @itemx Z @var{type},@var{addr},@var{kind}
37839 @anchor{insert breakpoint or watchpoint packet}
37840 @cindex @samp{z} packet
37841 @cindex @samp{Z} packets
37842 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
37843 watchpoint starting at address @var{address} of kind @var{kind}.
37845 Each breakpoint and watchpoint packet @var{type} is documented
37848 @emph{Implementation notes: A remote target shall return an empty string
37849 for an unrecognized breakpoint or watchpoint packet @var{type}. A
37850 remote target shall support either both or neither of a given
37851 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
37852 avoid potential problems with duplicate packets, the operations should
37853 be implemented in an idempotent way.}
37855 @item z0,@var{addr},@var{kind}
37856 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
37857 @cindex @samp{z0} packet
37858 @cindex @samp{Z0} packet
37859 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
37860 @var{addr} of type @var{kind}.
37862 A memory breakpoint is implemented by replacing the instruction at
37863 @var{addr} with a software breakpoint or trap instruction. The
37864 @var{kind} is target-specific and typically indicates the size of
37865 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
37866 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
37867 architectures have additional meanings for @var{kind};
37868 @var{cond_list} is an optional list of conditional expressions in bytecode
37869 form that should be evaluated on the target's side. These are the
37870 conditions that should be taken into consideration when deciding if
37871 the breakpoint trigger should be reported back to @var{GDBN}.
37873 The @var{cond_list} parameter is comprised of a series of expressions,
37874 concatenated without separators. Each expression has the following form:
37878 @item X @var{len},@var{expr}
37879 @var{len} is the length of the bytecode expression and @var{expr} is the
37880 actual conditional expression in bytecode form.
37884 The optional @var{cmd_list} parameter introduces commands that may be
37885 run on the target, rather than being reported back to @value{GDBN}.
37886 The parameter starts with a numeric flag @var{persist}; if the flag is
37887 nonzero, then the breakpoint may remain active and the commands
37888 continue to be run even when @value{GDBN} disconnects from the target.
37889 Following this flag is a series of expressions concatenated with no
37890 separators. Each expression has the following form:
37894 @item X @var{len},@var{expr}
37895 @var{len} is the length of the bytecode expression and @var{expr} is the
37896 actual conditional expression in bytecode form.
37900 see @ref{Architecture-Specific Protocol Details}.
37902 @emph{Implementation note: It is possible for a target to copy or move
37903 code that contains memory breakpoints (e.g., when implementing
37904 overlays). The behavior of this packet, in the presence of such a
37905 target, is not defined.}
37917 @item z1,@var{addr},@var{kind}
37918 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
37919 @cindex @samp{z1} packet
37920 @cindex @samp{Z1} packet
37921 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
37922 address @var{addr}.
37924 A hardware breakpoint is implemented using a mechanism that is not
37925 dependant on being able to modify the target's memory. @var{kind}
37926 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
37928 @emph{Implementation note: A hardware breakpoint is not affected by code
37941 @item z2,@var{addr},@var{kind}
37942 @itemx Z2,@var{addr},@var{kind}
37943 @cindex @samp{z2} packet
37944 @cindex @samp{Z2} packet
37945 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
37946 @var{kind} is interpreted as the number of bytes to watch.
37958 @item z3,@var{addr},@var{kind}
37959 @itemx Z3,@var{addr},@var{kind}
37960 @cindex @samp{z3} packet
37961 @cindex @samp{Z3} packet
37962 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
37963 @var{kind} is interpreted as the number of bytes to watch.
37975 @item z4,@var{addr},@var{kind}
37976 @itemx Z4,@var{addr},@var{kind}
37977 @cindex @samp{z4} packet
37978 @cindex @samp{Z4} packet
37979 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
37980 @var{kind} is interpreted as the number of bytes to watch.
37994 @node Stop Reply Packets
37995 @section Stop Reply Packets
37996 @cindex stop reply packets
37998 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
37999 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
38000 receive any of the below as a reply. Except for @samp{?}
38001 and @samp{vStopped}, that reply is only returned
38002 when the target halts. In the below the exact meaning of @dfn{signal
38003 number} is defined by the header @file{include/gdb/signals.h} in the
38004 @value{GDBN} source code.
38006 As in the description of request packets, we include spaces in the
38007 reply templates for clarity; these are not part of the reply packet's
38008 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
38014 The program received signal number @var{AA} (a two-digit hexadecimal
38015 number). This is equivalent to a @samp{T} response with no
38016 @var{n}:@var{r} pairs.
38018 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
38019 @cindex @samp{T} packet reply
38020 The program received signal number @var{AA} (a two-digit hexadecimal
38021 number). This is equivalent to an @samp{S} response, except that the
38022 @samp{@var{n}:@var{r}} pairs can carry values of important registers
38023 and other information directly in the stop reply packet, reducing
38024 round-trip latency. Single-step and breakpoint traps are reported
38025 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
38029 If @var{n} is a hexadecimal number, it is a register number, and the
38030 corresponding @var{r} gives that register's value. @var{r} is a
38031 series of bytes in target byte order, with each byte given by a
38032 two-digit hex number.
38035 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
38036 the stopped thread, as specified in @ref{thread-id syntax}.
38039 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
38040 the core on which the stop event was detected.
38043 If @var{n} is a recognized @dfn{stop reason}, it describes a more
38044 specific event that stopped the target. The currently defined stop
38045 reasons are listed below. @var{aa} should be @samp{05}, the trap
38046 signal. At most one stop reason should be present.
38049 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
38050 and go on to the next; this allows us to extend the protocol in the
38054 The currently defined stop reasons are:
38060 The packet indicates a watchpoint hit, and @var{r} is the data address, in
38063 @cindex shared library events, remote reply
38065 The packet indicates that the loaded libraries have changed.
38066 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
38067 list of loaded libraries. @var{r} is ignored.
38069 @cindex replay log events, remote reply
38071 The packet indicates that the target cannot continue replaying
38072 logged execution events, because it has reached the end (or the
38073 beginning when executing backward) of the log. The value of @var{r}
38074 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
38075 for more information.
38079 @itemx W @var{AA} ; process:@var{pid}
38080 The process exited, and @var{AA} is the exit status. This is only
38081 applicable to certain targets.
38083 The second form of the response, including the process ID of the exited
38084 process, can be used only when @value{GDBN} has reported support for
38085 multiprocess protocol extensions; see @ref{multiprocess extensions}.
38086 The @var{pid} is formatted as a big-endian hex string.
38089 @itemx X @var{AA} ; process:@var{pid}
38090 The process terminated with signal @var{AA}.
38092 The second form of the response, including the process ID of the
38093 terminated process, can be used only when @value{GDBN} has reported
38094 support for multiprocess protocol extensions; see @ref{multiprocess
38095 extensions}. The @var{pid} is formatted as a big-endian hex string.
38097 @item O @var{XX}@dots{}
38098 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
38099 written as the program's console output. This can happen at any time
38100 while the program is running and the debugger should continue to wait
38101 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
38103 @item F @var{call-id},@var{parameter}@dots{}
38104 @var{call-id} is the identifier which says which host system call should
38105 be called. This is just the name of the function. Translation into the
38106 correct system call is only applicable as it's defined in @value{GDBN}.
38107 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
38110 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
38111 this very system call.
38113 The target replies with this packet when it expects @value{GDBN} to
38114 call a host system call on behalf of the target. @value{GDBN} replies
38115 with an appropriate @samp{F} packet and keeps up waiting for the next
38116 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
38117 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
38118 Protocol Extension}, for more details.
38122 @node General Query Packets
38123 @section General Query Packets
38124 @cindex remote query requests
38126 Packets starting with @samp{q} are @dfn{general query packets};
38127 packets starting with @samp{Q} are @dfn{general set packets}. General
38128 query and set packets are a semi-unified form for retrieving and
38129 sending information to and from the stub.
38131 The initial letter of a query or set packet is followed by a name
38132 indicating what sort of thing the packet applies to. For example,
38133 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
38134 definitions with the stub. These packet names follow some
38139 The name must not contain commas, colons or semicolons.
38141 Most @value{GDBN} query and set packets have a leading upper case
38144 The names of custom vendor packets should use a company prefix, in
38145 lower case, followed by a period. For example, packets designed at
38146 the Acme Corporation might begin with @samp{qacme.foo} (for querying
38147 foos) or @samp{Qacme.bar} (for setting bars).
38150 The name of a query or set packet should be separated from any
38151 parameters by a @samp{:}; the parameters themselves should be
38152 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
38153 full packet name, and check for a separator or the end of the packet,
38154 in case two packet names share a common prefix. New packets should not begin
38155 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
38156 packets predate these conventions, and have arguments without any terminator
38157 for the packet name; we suspect they are in widespread use in places that
38158 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
38159 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
38162 Like the descriptions of the other packets, each description here
38163 has a template showing the packet's overall syntax, followed by an
38164 explanation of the packet's meaning. We include spaces in some of the
38165 templates for clarity; these are not part of the packet's syntax. No
38166 @value{GDBN} packet uses spaces to separate its components.
38168 Here are the currently defined query and set packets:
38174 Turn on or off the agent as a helper to perform some debugging operations
38175 delegated from @value{GDBN} (@pxref{Control Agent}).
38177 @item QAllow:@var{op}:@var{val}@dots{}
38178 @cindex @samp{QAllow} packet
38179 Specify which operations @value{GDBN} expects to request of the
38180 target, as a semicolon-separated list of operation name and value
38181 pairs. Possible values for @var{op} include @samp{WriteReg},
38182 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
38183 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
38184 indicating that @value{GDBN} will not request the operation, or 1,
38185 indicating that it may. (The target can then use this to set up its
38186 own internals optimally, for instance if the debugger never expects to
38187 insert breakpoints, it may not need to install its own trap handler.)
38190 @cindex current thread, remote request
38191 @cindex @samp{qC} packet
38192 Return the current thread ID.
38196 @item QC @var{thread-id}
38197 Where @var{thread-id} is a thread ID as documented in
38198 @ref{thread-id syntax}.
38199 @item @r{(anything else)}
38200 Any other reply implies the old thread ID.
38203 @item qCRC:@var{addr},@var{length}
38204 @cindex CRC of memory block, remote request
38205 @cindex @samp{qCRC} packet
38206 Compute the CRC checksum of a block of memory using CRC-32 defined in
38207 IEEE 802.3. The CRC is computed byte at a time, taking the most
38208 significant bit of each byte first. The initial pattern code
38209 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
38211 @emph{Note:} This is the same CRC used in validating separate debug
38212 files (@pxref{Separate Debug Files, , Debugging Information in Separate
38213 Files}). However the algorithm is slightly different. When validating
38214 separate debug files, the CRC is computed taking the @emph{least}
38215 significant bit of each byte first, and the final result is inverted to
38216 detect trailing zeros.
38221 An error (such as memory fault)
38222 @item C @var{crc32}
38223 The specified memory region's checksum is @var{crc32}.
38226 @item QDisableRandomization:@var{value}
38227 @cindex disable address space randomization, remote request
38228 @cindex @samp{QDisableRandomization} packet
38229 Some target operating systems will randomize the virtual address space
38230 of the inferior process as a security feature, but provide a feature
38231 to disable such randomization, e.g.@: to allow for a more deterministic
38232 debugging experience. On such systems, this packet with a @var{value}
38233 of 1 directs the target to disable address space randomization for
38234 processes subsequently started via @samp{vRun} packets, while a packet
38235 with a @var{value} of 0 tells the target to enable address space
38238 This packet is only available in extended mode (@pxref{extended mode}).
38243 The request succeeded.
38246 An error occurred. @var{nn} are hex digits.
38249 An empty reply indicates that @samp{QDisableRandomization} is not supported
38253 This packet is not probed by default; the remote stub must request it,
38254 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38255 This should only be done on targets that actually support disabling
38256 address space randomization.
38259 @itemx qsThreadInfo
38260 @cindex list active threads, remote request
38261 @cindex @samp{qfThreadInfo} packet
38262 @cindex @samp{qsThreadInfo} packet
38263 Obtain a list of all active thread IDs from the target (OS). Since there
38264 may be too many active threads to fit into one reply packet, this query
38265 works iteratively: it may require more than one query/reply sequence to
38266 obtain the entire list of threads. The first query of the sequence will
38267 be the @samp{qfThreadInfo} query; subsequent queries in the
38268 sequence will be the @samp{qsThreadInfo} query.
38270 NOTE: This packet replaces the @samp{qL} query (see below).
38274 @item m @var{thread-id}
38276 @item m @var{thread-id},@var{thread-id}@dots{}
38277 a comma-separated list of thread IDs
38279 (lower case letter @samp{L}) denotes end of list.
38282 In response to each query, the target will reply with a list of one or
38283 more thread IDs, separated by commas.
38284 @value{GDBN} will respond to each reply with a request for more thread
38285 ids (using the @samp{qs} form of the query), until the target responds
38286 with @samp{l} (lower-case ell, for @dfn{last}).
38287 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
38290 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
38291 @cindex get thread-local storage address, remote request
38292 @cindex @samp{qGetTLSAddr} packet
38293 Fetch the address associated with thread local storage specified
38294 by @var{thread-id}, @var{offset}, and @var{lm}.
38296 @var{thread-id} is the thread ID associated with the
38297 thread for which to fetch the TLS address. @xref{thread-id syntax}.
38299 @var{offset} is the (big endian, hex encoded) offset associated with the
38300 thread local variable. (This offset is obtained from the debug
38301 information associated with the variable.)
38303 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
38304 load module associated with the thread local storage. For example,
38305 a @sc{gnu}/Linux system will pass the link map address of the shared
38306 object associated with the thread local storage under consideration.
38307 Other operating environments may choose to represent the load module
38308 differently, so the precise meaning of this parameter will vary.
38312 @item @var{XX}@dots{}
38313 Hex encoded (big endian) bytes representing the address of the thread
38314 local storage requested.
38317 An error occurred. @var{nn} are hex digits.
38320 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
38323 @item qGetTIBAddr:@var{thread-id}
38324 @cindex get thread information block address
38325 @cindex @samp{qGetTIBAddr} packet
38326 Fetch address of the Windows OS specific Thread Information Block.
38328 @var{thread-id} is the thread ID associated with the thread.
38332 @item @var{XX}@dots{}
38333 Hex encoded (big endian) bytes representing the linear address of the
38334 thread information block.
38337 An error occured. This means that either the thread was not found, or the
38338 address could not be retrieved.
38341 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
38344 @item qL @var{startflag} @var{threadcount} @var{nextthread}
38345 Obtain thread information from RTOS. Where: @var{startflag} (one hex
38346 digit) is one to indicate the first query and zero to indicate a
38347 subsequent query; @var{threadcount} (two hex digits) is the maximum
38348 number of threads the response packet can contain; and @var{nextthread}
38349 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
38350 returned in the response as @var{argthread}.
38352 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
38356 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
38357 Where: @var{count} (two hex digits) is the number of threads being
38358 returned; @var{done} (one hex digit) is zero to indicate more threads
38359 and one indicates no further threads; @var{argthreadid} (eight hex
38360 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
38361 is a sequence of thread IDs from the target. @var{threadid} (eight hex
38362 digits). See @code{remote.c:parse_threadlist_response()}.
38366 @cindex section offsets, remote request
38367 @cindex @samp{qOffsets} packet
38368 Get section offsets that the target used when relocating the downloaded
38373 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
38374 Relocate the @code{Text} section by @var{xxx} from its original address.
38375 Relocate the @code{Data} section by @var{yyy} from its original address.
38376 If the object file format provides segment information (e.g.@: @sc{elf}
38377 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
38378 segments by the supplied offsets.
38380 @emph{Note: while a @code{Bss} offset may be included in the response,
38381 @value{GDBN} ignores this and instead applies the @code{Data} offset
38382 to the @code{Bss} section.}
38384 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
38385 Relocate the first segment of the object file, which conventionally
38386 contains program code, to a starting address of @var{xxx}. If
38387 @samp{DataSeg} is specified, relocate the second segment, which
38388 conventionally contains modifiable data, to a starting address of
38389 @var{yyy}. @value{GDBN} will report an error if the object file
38390 does not contain segment information, or does not contain at least
38391 as many segments as mentioned in the reply. Extra segments are
38392 kept at fixed offsets relative to the last relocated segment.
38395 @item qP @var{mode} @var{thread-id}
38396 @cindex thread information, remote request
38397 @cindex @samp{qP} packet
38398 Returns information on @var{thread-id}. Where: @var{mode} is a hex
38399 encoded 32 bit mode; @var{thread-id} is a thread ID
38400 (@pxref{thread-id syntax}).
38402 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
38405 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
38409 @cindex non-stop mode, remote request
38410 @cindex @samp{QNonStop} packet
38412 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
38413 @xref{Remote Non-Stop}, for more information.
38418 The request succeeded.
38421 An error occurred. @var{nn} are hex digits.
38424 An empty reply indicates that @samp{QNonStop} is not supported by
38428 This packet is not probed by default; the remote stub must request it,
38429 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38430 Use of this packet is controlled by the @code{set non-stop} command;
38431 @pxref{Non-Stop Mode}.
38433 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38434 @cindex pass signals to inferior, remote request
38435 @cindex @samp{QPassSignals} packet
38436 @anchor{QPassSignals}
38437 Each listed @var{signal} should be passed directly to the inferior process.
38438 Signals are numbered identically to continue packets and stop replies
38439 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38440 strictly greater than the previous item. These signals do not need to stop
38441 the inferior, or be reported to @value{GDBN}. All other signals should be
38442 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
38443 combine; any earlier @samp{QPassSignals} list is completely replaced by the
38444 new list. This packet improves performance when using @samp{handle
38445 @var{signal} nostop noprint pass}.
38450 The request succeeded.
38453 An error occurred. @var{nn} are hex digits.
38456 An empty reply indicates that @samp{QPassSignals} is not supported by
38460 Use of this packet is controlled by the @code{set remote pass-signals}
38461 command (@pxref{Remote Configuration, set remote pass-signals}).
38462 This packet is not probed by default; the remote stub must request it,
38463 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38465 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
38466 @cindex signals the inferior may see, remote request
38467 @cindex @samp{QProgramSignals} packet
38468 @anchor{QProgramSignals}
38469 Each listed @var{signal} may be delivered to the inferior process.
38470 Others should be silently discarded.
38472 In some cases, the remote stub may need to decide whether to deliver a
38473 signal to the program or not without @value{GDBN} involvement. One
38474 example of that is while detaching --- the program's threads may have
38475 stopped for signals that haven't yet had a chance of being reported to
38476 @value{GDBN}, and so the remote stub can use the signal list specified
38477 by this packet to know whether to deliver or ignore those pending
38480 This does not influence whether to deliver a signal as requested by a
38481 resumption packet (@pxref{vCont packet}).
38483 Signals are numbered identically to continue packets and stop replies
38484 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
38485 strictly greater than the previous item. Multiple
38486 @samp{QProgramSignals} packets do not combine; any earlier
38487 @samp{QProgramSignals} list is completely replaced by the new list.
38492 The request succeeded.
38495 An error occurred. @var{nn} are hex digits.
38498 An empty reply indicates that @samp{QProgramSignals} is not supported
38502 Use of this packet is controlled by the @code{set remote program-signals}
38503 command (@pxref{Remote Configuration, set remote program-signals}).
38504 This packet is not probed by default; the remote stub must request it,
38505 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38507 @item qRcmd,@var{command}
38508 @cindex execute remote command, remote request
38509 @cindex @samp{qRcmd} packet
38510 @var{command} (hex encoded) is passed to the local interpreter for
38511 execution. Invalid commands should be reported using the output
38512 string. Before the final result packet, the target may also respond
38513 with a number of intermediate @samp{O@var{output}} console output
38514 packets. @emph{Implementors should note that providing access to a
38515 stubs's interpreter may have security implications}.
38520 A command response with no output.
38522 A command response with the hex encoded output string @var{OUTPUT}.
38524 Indicate a badly formed request.
38526 An empty reply indicates that @samp{qRcmd} is not recognized.
38529 (Note that the @code{qRcmd} packet's name is separated from the
38530 command by a @samp{,}, not a @samp{:}, contrary to the naming
38531 conventions above. Please don't use this packet as a model for new
38534 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
38535 @cindex searching memory, in remote debugging
38537 @cindex @samp{qSearch:memory} packet
38539 @cindex @samp{qSearch memory} packet
38540 @anchor{qSearch memory}
38541 Search @var{length} bytes at @var{address} for @var{search-pattern}.
38542 @var{address} and @var{length} are encoded in hex.
38543 @var{search-pattern} is a sequence of bytes, hex encoded.
38548 The pattern was not found.
38550 The pattern was found at @var{address}.
38552 A badly formed request or an error was encountered while searching memory.
38554 An empty reply indicates that @samp{qSearch:memory} is not recognized.
38557 @item QStartNoAckMode
38558 @cindex @samp{QStartNoAckMode} packet
38559 @anchor{QStartNoAckMode}
38560 Request that the remote stub disable the normal @samp{+}/@samp{-}
38561 protocol acknowledgments (@pxref{Packet Acknowledgment}).
38566 The stub has switched to no-acknowledgment mode.
38567 @value{GDBN} acknowledges this reponse,
38568 but neither the stub nor @value{GDBN} shall send or expect further
38569 @samp{+}/@samp{-} acknowledgments in the current connection.
38571 An empty reply indicates that the stub does not support no-acknowledgment mode.
38574 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
38575 @cindex supported packets, remote query
38576 @cindex features of the remote protocol
38577 @cindex @samp{qSupported} packet
38578 @anchor{qSupported}
38579 Tell the remote stub about features supported by @value{GDBN}, and
38580 query the stub for features it supports. This packet allows
38581 @value{GDBN} and the remote stub to take advantage of each others'
38582 features. @samp{qSupported} also consolidates multiple feature probes
38583 at startup, to improve @value{GDBN} performance---a single larger
38584 packet performs better than multiple smaller probe packets on
38585 high-latency links. Some features may enable behavior which must not
38586 be on by default, e.g.@: because it would confuse older clients or
38587 stubs. Other features may describe packets which could be
38588 automatically probed for, but are not. These features must be
38589 reported before @value{GDBN} will use them. This ``default
38590 unsupported'' behavior is not appropriate for all packets, but it
38591 helps to keep the initial connection time under control with new
38592 versions of @value{GDBN} which support increasing numbers of packets.
38596 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
38597 The stub supports or does not support each returned @var{stubfeature},
38598 depending on the form of each @var{stubfeature} (see below for the
38601 An empty reply indicates that @samp{qSupported} is not recognized,
38602 or that no features needed to be reported to @value{GDBN}.
38605 The allowed forms for each feature (either a @var{gdbfeature} in the
38606 @samp{qSupported} packet, or a @var{stubfeature} in the response)
38610 @item @var{name}=@var{value}
38611 The remote protocol feature @var{name} is supported, and associated
38612 with the specified @var{value}. The format of @var{value} depends
38613 on the feature, but it must not include a semicolon.
38615 The remote protocol feature @var{name} is supported, and does not
38616 need an associated value.
38618 The remote protocol feature @var{name} is not supported.
38620 The remote protocol feature @var{name} may be supported, and
38621 @value{GDBN} should auto-detect support in some other way when it is
38622 needed. This form will not be used for @var{gdbfeature} notifications,
38623 but may be used for @var{stubfeature} responses.
38626 Whenever the stub receives a @samp{qSupported} request, the
38627 supplied set of @value{GDBN} features should override any previous
38628 request. This allows @value{GDBN} to put the stub in a known
38629 state, even if the stub had previously been communicating with
38630 a different version of @value{GDBN}.
38632 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
38637 This feature indicates whether @value{GDBN} supports multiprocess
38638 extensions to the remote protocol. @value{GDBN} does not use such
38639 extensions unless the stub also reports that it supports them by
38640 including @samp{multiprocess+} in its @samp{qSupported} reply.
38641 @xref{multiprocess extensions}, for details.
38644 This feature indicates that @value{GDBN} supports the XML target
38645 description. If the stub sees @samp{xmlRegisters=} with target
38646 specific strings separated by a comma, it will report register
38650 This feature indicates whether @value{GDBN} supports the
38651 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
38652 instruction reply packet}).
38655 Stubs should ignore any unknown values for
38656 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
38657 packet supports receiving packets of unlimited length (earlier
38658 versions of @value{GDBN} may reject overly long responses). Additional values
38659 for @var{gdbfeature} may be defined in the future to let the stub take
38660 advantage of new features in @value{GDBN}, e.g.@: incompatible
38661 improvements in the remote protocol---the @samp{multiprocess} feature is
38662 an example of such a feature. The stub's reply should be independent
38663 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
38664 describes all the features it supports, and then the stub replies with
38665 all the features it supports.
38667 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
38668 responses, as long as each response uses one of the standard forms.
38670 Some features are flags. A stub which supports a flag feature
38671 should respond with a @samp{+} form response. Other features
38672 require values, and the stub should respond with an @samp{=}
38675 Each feature has a default value, which @value{GDBN} will use if
38676 @samp{qSupported} is not available or if the feature is not mentioned
38677 in the @samp{qSupported} response. The default values are fixed; a
38678 stub is free to omit any feature responses that match the defaults.
38680 Not all features can be probed, but for those which can, the probing
38681 mechanism is useful: in some cases, a stub's internal
38682 architecture may not allow the protocol layer to know some information
38683 about the underlying target in advance. This is especially common in
38684 stubs which may be configured for multiple targets.
38686 These are the currently defined stub features and their properties:
38688 @multitable @columnfractions 0.35 0.2 0.12 0.2
38689 @c NOTE: The first row should be @headitem, but we do not yet require
38690 @c a new enough version of Texinfo (4.7) to use @headitem.
38692 @tab Value Required
38696 @item @samp{PacketSize}
38701 @item @samp{qXfer:auxv:read}
38706 @item @samp{qXfer:btrace:read}
38711 @item @samp{qXfer:features:read}
38716 @item @samp{qXfer:libraries:read}
38721 @item @samp{qXfer:libraries-svr4:read}
38726 @item @samp{augmented-libraries-svr4-read}
38731 @item @samp{qXfer:memory-map:read}
38736 @item @samp{qXfer:sdata:read}
38741 @item @samp{qXfer:spu:read}
38746 @item @samp{qXfer:spu:write}
38751 @item @samp{qXfer:siginfo:read}
38756 @item @samp{qXfer:siginfo:write}
38761 @item @samp{qXfer:threads:read}
38766 @item @samp{qXfer:traceframe-info:read}
38771 @item @samp{qXfer:uib:read}
38776 @item @samp{qXfer:fdpic:read}
38781 @item @samp{Qbtrace:off}
38786 @item @samp{Qbtrace:bts}
38791 @item @samp{QNonStop}
38796 @item @samp{QPassSignals}
38801 @item @samp{QStartNoAckMode}
38806 @item @samp{multiprocess}
38811 @item @samp{ConditionalBreakpoints}
38816 @item @samp{ConditionalTracepoints}
38821 @item @samp{ReverseContinue}
38826 @item @samp{ReverseStep}
38831 @item @samp{TracepointSource}
38836 @item @samp{QAgent}
38841 @item @samp{QAllow}
38846 @item @samp{QDisableRandomization}
38851 @item @samp{EnableDisableTracepoints}
38856 @item @samp{QTBuffer:size}
38861 @item @samp{tracenz}
38866 @item @samp{BreakpointCommands}
38873 These are the currently defined stub features, in more detail:
38876 @cindex packet size, remote protocol
38877 @item PacketSize=@var{bytes}
38878 The remote stub can accept packets up to at least @var{bytes} in
38879 length. @value{GDBN} will send packets up to this size for bulk
38880 transfers, and will never send larger packets. This is a limit on the
38881 data characters in the packet, including the frame and checksum.
38882 There is no trailing NUL byte in a remote protocol packet; if the stub
38883 stores packets in a NUL-terminated format, it should allow an extra
38884 byte in its buffer for the NUL. If this stub feature is not supported,
38885 @value{GDBN} guesses based on the size of the @samp{g} packet response.
38887 @item qXfer:auxv:read
38888 The remote stub understands the @samp{qXfer:auxv:read} packet
38889 (@pxref{qXfer auxiliary vector read}).
38891 @item qXfer:btrace:read
38892 The remote stub understands the @samp{qXfer:btrace:read}
38893 packet (@pxref{qXfer btrace read}).
38895 @item qXfer:features:read
38896 The remote stub understands the @samp{qXfer:features:read} packet
38897 (@pxref{qXfer target description read}).
38899 @item qXfer:libraries:read
38900 The remote stub understands the @samp{qXfer:libraries:read} packet
38901 (@pxref{qXfer library list read}).
38903 @item qXfer:libraries-svr4:read
38904 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
38905 (@pxref{qXfer svr4 library list read}).
38907 @item augmented-libraries-svr4-read
38908 The remote stub understands the augmented form of the
38909 @samp{qXfer:libraries-svr4:read} packet
38910 (@pxref{qXfer svr4 library list read}).
38912 @item qXfer:memory-map:read
38913 The remote stub understands the @samp{qXfer:memory-map:read} packet
38914 (@pxref{qXfer memory map read}).
38916 @item qXfer:sdata:read
38917 The remote stub understands the @samp{qXfer:sdata:read} packet
38918 (@pxref{qXfer sdata read}).
38920 @item qXfer:spu:read
38921 The remote stub understands the @samp{qXfer:spu:read} packet
38922 (@pxref{qXfer spu read}).
38924 @item qXfer:spu:write
38925 The remote stub understands the @samp{qXfer:spu:write} packet
38926 (@pxref{qXfer spu write}).
38928 @item qXfer:siginfo:read
38929 The remote stub understands the @samp{qXfer:siginfo:read} packet
38930 (@pxref{qXfer siginfo read}).
38932 @item qXfer:siginfo:write
38933 The remote stub understands the @samp{qXfer:siginfo:write} packet
38934 (@pxref{qXfer siginfo write}).
38936 @item qXfer:threads:read
38937 The remote stub understands the @samp{qXfer:threads:read} packet
38938 (@pxref{qXfer threads read}).
38940 @item qXfer:traceframe-info:read
38941 The remote stub understands the @samp{qXfer:traceframe-info:read}
38942 packet (@pxref{qXfer traceframe info read}).
38944 @item qXfer:uib:read
38945 The remote stub understands the @samp{qXfer:uib:read}
38946 packet (@pxref{qXfer unwind info block}).
38948 @item qXfer:fdpic:read
38949 The remote stub understands the @samp{qXfer:fdpic:read}
38950 packet (@pxref{qXfer fdpic loadmap read}).
38953 The remote stub understands the @samp{QNonStop} packet
38954 (@pxref{QNonStop}).
38957 The remote stub understands the @samp{QPassSignals} packet
38958 (@pxref{QPassSignals}).
38960 @item QStartNoAckMode
38961 The remote stub understands the @samp{QStartNoAckMode} packet and
38962 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
38965 @anchor{multiprocess extensions}
38966 @cindex multiprocess extensions, in remote protocol
38967 The remote stub understands the multiprocess extensions to the remote
38968 protocol syntax. The multiprocess extensions affect the syntax of
38969 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
38970 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
38971 replies. Note that reporting this feature indicates support for the
38972 syntactic extensions only, not that the stub necessarily supports
38973 debugging of more than one process at a time. The stub must not use
38974 multiprocess extensions in packet replies unless @value{GDBN} has also
38975 indicated it supports them in its @samp{qSupported} request.
38977 @item qXfer:osdata:read
38978 The remote stub understands the @samp{qXfer:osdata:read} packet
38979 ((@pxref{qXfer osdata read}).
38981 @item ConditionalBreakpoints
38982 The target accepts and implements evaluation of conditional expressions
38983 defined for breakpoints. The target will only report breakpoint triggers
38984 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
38986 @item ConditionalTracepoints
38987 The remote stub accepts and implements conditional expressions defined
38988 for tracepoints (@pxref{Tracepoint Conditions}).
38990 @item ReverseContinue
38991 The remote stub accepts and implements the reverse continue packet
38995 The remote stub accepts and implements the reverse step packet
38998 @item TracepointSource
38999 The remote stub understands the @samp{QTDPsrc} packet that supplies
39000 the source form of tracepoint definitions.
39003 The remote stub understands the @samp{QAgent} packet.
39006 The remote stub understands the @samp{QAllow} packet.
39008 @item QDisableRandomization
39009 The remote stub understands the @samp{QDisableRandomization} packet.
39011 @item StaticTracepoint
39012 @cindex static tracepoints, in remote protocol
39013 The remote stub supports static tracepoints.
39015 @item InstallInTrace
39016 @anchor{install tracepoint in tracing}
39017 The remote stub supports installing tracepoint in tracing.
39019 @item EnableDisableTracepoints
39020 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
39021 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
39022 to be enabled and disabled while a trace experiment is running.
39024 @item QTBuffer:size
39025 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
39026 packet that allows to change the size of the trace buffer.
39029 @cindex string tracing, in remote protocol
39030 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
39031 See @ref{Bytecode Descriptions} for details about the bytecode.
39033 @item BreakpointCommands
39034 @cindex breakpoint commands, in remote protocol
39035 The remote stub supports running a breakpoint's command list itself,
39036 rather than reporting the hit to @value{GDBN}.
39039 The remote stub understands the @samp{Qbtrace:off} packet.
39042 The remote stub understands the @samp{Qbtrace:bts} packet.
39047 @cindex symbol lookup, remote request
39048 @cindex @samp{qSymbol} packet
39049 Notify the target that @value{GDBN} is prepared to serve symbol lookup
39050 requests. Accept requests from the target for the values of symbols.
39055 The target does not need to look up any (more) symbols.
39056 @item qSymbol:@var{sym_name}
39057 The target requests the value of symbol @var{sym_name} (hex encoded).
39058 @value{GDBN} may provide the value by using the
39059 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
39063 @item qSymbol:@var{sym_value}:@var{sym_name}
39064 Set the value of @var{sym_name} to @var{sym_value}.
39066 @var{sym_name} (hex encoded) is the name of a symbol whose value the
39067 target has previously requested.
39069 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
39070 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
39076 The target does not need to look up any (more) symbols.
39077 @item qSymbol:@var{sym_name}
39078 The target requests the value of a new symbol @var{sym_name} (hex
39079 encoded). @value{GDBN} will continue to supply the values of symbols
39080 (if available), until the target ceases to request them.
39085 @itemx QTDisconnected
39092 @itemx qTMinFTPILen
39094 @xref{Tracepoint Packets}.
39096 @item qThreadExtraInfo,@var{thread-id}
39097 @cindex thread attributes info, remote request
39098 @cindex @samp{qThreadExtraInfo} packet
39099 Obtain a printable string description of a thread's attributes from
39100 the target OS. @var{thread-id} is a thread ID;
39101 see @ref{thread-id syntax}. This
39102 string may contain anything that the target OS thinks is interesting
39103 for @value{GDBN} to tell the user about the thread. The string is
39104 displayed in @value{GDBN}'s @code{info threads} display. Some
39105 examples of possible thread extra info strings are @samp{Runnable}, or
39106 @samp{Blocked on Mutex}.
39110 @item @var{XX}@dots{}
39111 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
39112 comprising the printable string containing the extra information about
39113 the thread's attributes.
39116 (Note that the @code{qThreadExtraInfo} packet's name is separated from
39117 the command by a @samp{,}, not a @samp{:}, contrary to the naming
39118 conventions above. Please don't use this packet as a model for new
39137 @xref{Tracepoint Packets}.
39139 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
39140 @cindex read special object, remote request
39141 @cindex @samp{qXfer} packet
39142 @anchor{qXfer read}
39143 Read uninterpreted bytes from the target's special data area
39144 identified by the keyword @var{object}. Request @var{length} bytes
39145 starting at @var{offset} bytes into the data. The content and
39146 encoding of @var{annex} is specific to @var{object}; it can supply
39147 additional details about what data to access.
39149 Here are the specific requests of this form defined so far. All
39150 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
39151 formats, listed below.
39154 @item qXfer:auxv:read::@var{offset},@var{length}
39155 @anchor{qXfer auxiliary vector read}
39156 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
39157 auxiliary vector}. Note @var{annex} must be empty.
39159 This packet is not probed by default; the remote stub must request it,
39160 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39162 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
39163 @anchor{qXfer btrace read}
39165 Return a description of the current branch trace.
39166 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
39167 packet may have one of the following values:
39171 Returns all available branch trace.
39174 Returns all available branch trace if the branch trace changed since
39175 the last read request.
39178 This packet is not probed by default; the remote stub must request it
39179 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39181 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
39182 @anchor{qXfer target description read}
39183 Access the @dfn{target description}. @xref{Target Descriptions}. The
39184 annex specifies which XML document to access. The main description is
39185 always loaded from the @samp{target.xml} annex.
39187 This packet is not probed by default; the remote stub must request it,
39188 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39190 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
39191 @anchor{qXfer library list read}
39192 Access the target's list of loaded libraries. @xref{Library List Format}.
39193 The annex part of the generic @samp{qXfer} packet must be empty
39194 (@pxref{qXfer read}).
39196 Targets which maintain a list of libraries in the program's memory do
39197 not need to implement this packet; it is designed for platforms where
39198 the operating system manages the list of loaded libraries.
39200 This packet is not probed by default; the remote stub must request it,
39201 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39203 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
39204 @anchor{qXfer svr4 library list read}
39205 Access the target's list of loaded libraries when the target is an SVR4
39206 platform. @xref{Library List Format for SVR4 Targets}. The annex part
39207 of the generic @samp{qXfer} packet must be empty unless the remote
39208 stub indicated it supports the augmented form of this packet
39209 by supplying an appropriate @samp{qSupported} response
39210 (@pxref{qXfer read}, @ref{qSupported}).
39212 This packet is optional for better performance on SVR4 targets.
39213 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
39215 This packet is not probed by default; the remote stub must request it,
39216 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39218 If the remote stub indicates it supports the augmented form of this
39219 packet then the annex part of the generic @samp{qXfer} packet may
39220 contain a semicolon-separated list of @samp{@var{name}=@var{value}}
39221 arguments. The currently supported arguments are:
39224 @item start=@var{address}
39225 A hexadecimal number specifying the address of the @samp{struct
39226 link_map} to start reading the library list from. If unset or zero
39227 then the first @samp{struct link_map} in the library list will be
39228 chosen as the starting point.
39230 @item prev=@var{address}
39231 A hexadecimal number specifying the address of the @samp{struct
39232 link_map} immediately preceding the @samp{struct link_map}
39233 specified by the @samp{start} argument. If unset or zero then
39234 the remote stub will expect that no @samp{struct link_map}
39235 exists prior to the starting point.
39239 Arguments that are not understood by the remote stub will be silently
39242 @item qXfer:memory-map:read::@var{offset},@var{length}
39243 @anchor{qXfer memory map read}
39244 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
39245 annex part of the generic @samp{qXfer} packet must be empty
39246 (@pxref{qXfer read}).
39248 This packet is not probed by default; the remote stub must request it,
39249 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39251 @item qXfer:sdata:read::@var{offset},@var{length}
39252 @anchor{qXfer sdata read}
39254 Read contents of the extra collected static tracepoint marker
39255 information. The annex part of the generic @samp{qXfer} packet must
39256 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
39259 This packet is not probed by default; the remote stub must request it,
39260 by supplying an appropriate @samp{qSupported} response
39261 (@pxref{qSupported}).
39263 @item qXfer:siginfo:read::@var{offset},@var{length}
39264 @anchor{qXfer siginfo read}
39265 Read contents of the extra signal information on the target
39266 system. The annex part of the generic @samp{qXfer} packet must be
39267 empty (@pxref{qXfer read}).
39269 This packet is not probed by default; the remote stub must request it,
39270 by supplying an appropriate @samp{qSupported} response
39271 (@pxref{qSupported}).
39273 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
39274 @anchor{qXfer spu read}
39275 Read contents of an @code{spufs} file on the target system. The
39276 annex specifies which file to read; it must be of the form
39277 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39278 in the target process, and @var{name} identifes the @code{spufs} file
39279 in that context to be accessed.
39281 This packet is not probed by default; the remote stub must request it,
39282 by supplying an appropriate @samp{qSupported} response
39283 (@pxref{qSupported}).
39285 @item qXfer:threads:read::@var{offset},@var{length}
39286 @anchor{qXfer threads read}
39287 Access the list of threads on target. @xref{Thread List Format}. The
39288 annex part of the generic @samp{qXfer} packet must be empty
39289 (@pxref{qXfer read}).
39291 This packet is not probed by default; the remote stub must request it,
39292 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39294 @item qXfer:traceframe-info:read::@var{offset},@var{length}
39295 @anchor{qXfer traceframe info read}
39297 Return a description of the current traceframe's contents.
39298 @xref{Traceframe Info Format}. The annex part of the generic
39299 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
39301 This packet is not probed by default; the remote stub must request it,
39302 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39304 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
39305 @anchor{qXfer unwind info block}
39307 Return the unwind information block for @var{pc}. This packet is used
39308 on OpenVMS/ia64 to ask the kernel unwind information.
39310 This packet is not probed by default.
39312 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
39313 @anchor{qXfer fdpic loadmap read}
39314 Read contents of @code{loadmap}s on the target system. The
39315 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
39316 executable @code{loadmap} or interpreter @code{loadmap} to read.
39318 This packet is not probed by default; the remote stub must request it,
39319 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39321 @item qXfer:osdata:read::@var{offset},@var{length}
39322 @anchor{qXfer osdata read}
39323 Access the target's @dfn{operating system information}.
39324 @xref{Operating System Information}.
39331 Data @var{data} (@pxref{Binary Data}) has been read from the
39332 target. There may be more data at a higher address (although
39333 it is permitted to return @samp{m} even for the last valid
39334 block of data, as long as at least one byte of data was read).
39335 @var{data} may have fewer bytes than the @var{length} in the
39339 Data @var{data} (@pxref{Binary Data}) has been read from the target.
39340 There is no more data to be read. @var{data} may have fewer bytes
39341 than the @var{length} in the request.
39344 The @var{offset} in the request is at the end of the data.
39345 There is no more data to be read.
39348 The request was malformed, or @var{annex} was invalid.
39351 The offset was invalid, or there was an error encountered reading the data.
39352 @var{nn} is a hex-encoded @code{errno} value.
39355 An empty reply indicates the @var{object} string was not recognized by
39356 the stub, or that the object does not support reading.
39359 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
39360 @cindex write data into object, remote request
39361 @anchor{qXfer write}
39362 Write uninterpreted bytes into the target's special data area
39363 identified by the keyword @var{object}, starting at @var{offset} bytes
39364 into the data. @var{data}@dots{} is the binary-encoded data
39365 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
39366 is specific to @var{object}; it can supply additional details about what data
39369 Here are the specific requests of this form defined so far. All
39370 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
39371 formats, listed below.
39374 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
39375 @anchor{qXfer siginfo write}
39376 Write @var{data} to the extra signal information on the target system.
39377 The annex part of the generic @samp{qXfer} packet must be
39378 empty (@pxref{qXfer write}).
39380 This packet is not probed by default; the remote stub must request it,
39381 by supplying an appropriate @samp{qSupported} response
39382 (@pxref{qSupported}).
39384 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
39385 @anchor{qXfer spu write}
39386 Write @var{data} to an @code{spufs} file on the target system. The
39387 annex specifies which file to write; it must be of the form
39388 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
39389 in the target process, and @var{name} identifes the @code{spufs} file
39390 in that context to be accessed.
39392 This packet is not probed by default; the remote stub must request it,
39393 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
39399 @var{nn} (hex encoded) is the number of bytes written.
39400 This may be fewer bytes than supplied in the request.
39403 The request was malformed, or @var{annex} was invalid.
39406 The offset was invalid, or there was an error encountered writing the data.
39407 @var{nn} is a hex-encoded @code{errno} value.
39410 An empty reply indicates the @var{object} string was not
39411 recognized by the stub, or that the object does not support writing.
39414 @item qXfer:@var{object}:@var{operation}:@dots{}
39415 Requests of this form may be added in the future. When a stub does
39416 not recognize the @var{object} keyword, or its support for
39417 @var{object} does not recognize the @var{operation} keyword, the stub
39418 must respond with an empty packet.
39420 @item qAttached:@var{pid}
39421 @cindex query attached, remote request
39422 @cindex @samp{qAttached} packet
39423 Return an indication of whether the remote server attached to an
39424 existing process or created a new process. When the multiprocess
39425 protocol extensions are supported (@pxref{multiprocess extensions}),
39426 @var{pid} is an integer in hexadecimal format identifying the target
39427 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
39428 the query packet will be simplified as @samp{qAttached}.
39430 This query is used, for example, to know whether the remote process
39431 should be detached or killed when a @value{GDBN} session is ended with
39432 the @code{quit} command.
39437 The remote server attached to an existing process.
39439 The remote server created a new process.
39441 A badly formed request or an error was encountered.
39445 Enable branch tracing for the current thread using bts tracing.
39450 Branch tracing has been enabled.
39452 A badly formed request or an error was encountered.
39456 Disable branch tracing for the current thread.
39461 Branch tracing has been disabled.
39463 A badly formed request or an error was encountered.
39468 @node Architecture-Specific Protocol Details
39469 @section Architecture-Specific Protocol Details
39471 This section describes how the remote protocol is applied to specific
39472 target architectures. Also see @ref{Standard Target Features}, for
39473 details of XML target descriptions for each architecture.
39476 * ARM-Specific Protocol Details::
39477 * MIPS-Specific Protocol Details::
39480 @node ARM-Specific Protocol Details
39481 @subsection @acronym{ARM}-specific Protocol Details
39484 * ARM Breakpoint Kinds::
39487 @node ARM Breakpoint Kinds
39488 @subsubsection @acronym{ARM} Breakpoint Kinds
39489 @cindex breakpoint kinds, @acronym{ARM}
39491 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39496 16-bit Thumb mode breakpoint.
39499 32-bit Thumb mode (Thumb-2) breakpoint.
39502 32-bit @acronym{ARM} mode breakpoint.
39506 @node MIPS-Specific Protocol Details
39507 @subsection @acronym{MIPS}-specific Protocol Details
39510 * MIPS Register packet Format::
39511 * MIPS Breakpoint Kinds::
39514 @node MIPS Register packet Format
39515 @subsubsection @acronym{MIPS} Register Packet Format
39516 @cindex register packet format, @acronym{MIPS}
39518 The following @code{g}/@code{G} packets have previously been defined.
39519 In the below, some thirty-two bit registers are transferred as
39520 sixty-four bits. Those registers should be zero/sign extended (which?)
39521 to fill the space allocated. Register bytes are transferred in target
39522 byte order. The two nibbles within a register byte are transferred
39523 most-significant -- least-significant.
39528 All registers are transferred as thirty-two bit quantities in the order:
39529 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
39530 registers; fsr; fir; fp.
39533 All registers are transferred as sixty-four bit quantities (including
39534 thirty-two bit registers such as @code{sr}). The ordering is the same
39539 @node MIPS Breakpoint Kinds
39540 @subsubsection @acronym{MIPS} Breakpoint Kinds
39541 @cindex breakpoint kinds, @acronym{MIPS}
39543 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
39548 16-bit @acronym{MIPS16} mode breakpoint.
39551 16-bit @acronym{microMIPS} mode breakpoint.
39554 32-bit standard @acronym{MIPS} mode breakpoint.
39557 32-bit @acronym{microMIPS} mode breakpoint.
39561 @node Tracepoint Packets
39562 @section Tracepoint Packets
39563 @cindex tracepoint packets
39564 @cindex packets, tracepoint
39566 Here we describe the packets @value{GDBN} uses to implement
39567 tracepoints (@pxref{Tracepoints}).
39571 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
39572 @cindex @samp{QTDP} packet
39573 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
39574 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
39575 the tracepoint is disabled. @var{step} is the tracepoint's step
39576 count, and @var{pass} is its pass count. If an @samp{F} is present,
39577 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
39578 the number of bytes that the target should copy elsewhere to make room
39579 for the tracepoint. If an @samp{X} is present, it introduces a
39580 tracepoint condition, which consists of a hexadecimal length, followed
39581 by a comma and hex-encoded bytes, in a manner similar to action
39582 encodings as described below. If the trailing @samp{-} is present,
39583 further @samp{QTDP} packets will follow to specify this tracepoint's
39589 The packet was understood and carried out.
39591 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39593 The packet was not recognized.
39596 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
39597 Define actions to be taken when a tracepoint is hit. @var{n} and
39598 @var{addr} must be the same as in the initial @samp{QTDP} packet for
39599 this tracepoint. This packet may only be sent immediately after
39600 another @samp{QTDP} packet that ended with a @samp{-}. If the
39601 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
39602 specifying more actions for this tracepoint.
39604 In the series of action packets for a given tracepoint, at most one
39605 can have an @samp{S} before its first @var{action}. If such a packet
39606 is sent, it and the following packets define ``while-stepping''
39607 actions. Any prior packets define ordinary actions --- that is, those
39608 taken when the tracepoint is first hit. If no action packet has an
39609 @samp{S}, then all the packets in the series specify ordinary
39610 tracepoint actions.
39612 The @samp{@var{action}@dots{}} portion of the packet is a series of
39613 actions, concatenated without separators. Each action has one of the
39619 Collect the registers whose bits are set in @var{mask}. @var{mask} is
39620 a hexadecimal number whose @var{i}'th bit is set if register number
39621 @var{i} should be collected. (The least significant bit is numbered
39622 zero.) Note that @var{mask} may be any number of digits long; it may
39623 not fit in a 32-bit word.
39625 @item M @var{basereg},@var{offset},@var{len}
39626 Collect @var{len} bytes of memory starting at the address in register
39627 number @var{basereg}, plus @var{offset}. If @var{basereg} is
39628 @samp{-1}, then the range has a fixed address: @var{offset} is the
39629 address of the lowest byte to collect. The @var{basereg},
39630 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
39631 values (the @samp{-1} value for @var{basereg} is a special case).
39633 @item X @var{len},@var{expr}
39634 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
39635 it directs. @var{expr} is an agent expression, as described in
39636 @ref{Agent Expressions}. Each byte of the expression is encoded as a
39637 two-digit hex number in the packet; @var{len} is the number of bytes
39638 in the expression (and thus one-half the number of hex digits in the
39643 Any number of actions may be packed together in a single @samp{QTDP}
39644 packet, as long as the packet does not exceed the maximum packet
39645 length (400 bytes, for many stubs). There may be only one @samp{R}
39646 action per tracepoint, and it must precede any @samp{M} or @samp{X}
39647 actions. Any registers referred to by @samp{M} and @samp{X} actions
39648 must be collected by a preceding @samp{R} action. (The
39649 ``while-stepping'' actions are treated as if they were attached to a
39650 separate tracepoint, as far as these restrictions are concerned.)
39655 The packet was understood and carried out.
39657 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
39659 The packet was not recognized.
39662 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
39663 @cindex @samp{QTDPsrc} packet
39664 Specify a source string of tracepoint @var{n} at address @var{addr}.
39665 This is useful to get accurate reproduction of the tracepoints
39666 originally downloaded at the beginning of the trace run. @var{type}
39667 is the name of the tracepoint part, such as @samp{cond} for the
39668 tracepoint's conditional expression (see below for a list of types), while
39669 @var{bytes} is the string, encoded in hexadecimal.
39671 @var{start} is the offset of the @var{bytes} within the overall source
39672 string, while @var{slen} is the total length of the source string.
39673 This is intended for handling source strings that are longer than will
39674 fit in a single packet.
39675 @c Add detailed example when this info is moved into a dedicated
39676 @c tracepoint descriptions section.
39678 The available string types are @samp{at} for the location,
39679 @samp{cond} for the conditional, and @samp{cmd} for an action command.
39680 @value{GDBN} sends a separate packet for each command in the action
39681 list, in the same order in which the commands are stored in the list.
39683 The target does not need to do anything with source strings except
39684 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
39687 Although this packet is optional, and @value{GDBN} will only send it
39688 if the target replies with @samp{TracepointSource} @xref{General
39689 Query Packets}, it makes both disconnected tracing and trace files
39690 much easier to use. Otherwise the user must be careful that the
39691 tracepoints in effect while looking at trace frames are identical to
39692 the ones in effect during the trace run; even a small discrepancy
39693 could cause @samp{tdump} not to work, or a particular trace frame not
39696 @item QTDV:@var{n}:@var{value}
39697 @cindex define trace state variable, remote request
39698 @cindex @samp{QTDV} packet
39699 Create a new trace state variable, number @var{n}, with an initial
39700 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
39701 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
39702 the option of not using this packet for initial values of zero; the
39703 target should simply create the trace state variables as they are
39704 mentioned in expressions.
39706 @item QTFrame:@var{n}
39707 @cindex @samp{QTFrame} packet
39708 Select the @var{n}'th tracepoint frame from the buffer, and use the
39709 register and memory contents recorded there to answer subsequent
39710 request packets from @value{GDBN}.
39712 A successful reply from the stub indicates that the stub has found the
39713 requested frame. The response is a series of parts, concatenated
39714 without separators, describing the frame we selected. Each part has
39715 one of the following forms:
39719 The selected frame is number @var{n} in the trace frame buffer;
39720 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
39721 was no frame matching the criteria in the request packet.
39724 The selected trace frame records a hit of tracepoint number @var{t};
39725 @var{t} is a hexadecimal number.
39729 @item QTFrame:pc:@var{addr}
39730 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39731 currently selected frame whose PC is @var{addr};
39732 @var{addr} is a hexadecimal number.
39734 @item QTFrame:tdp:@var{t}
39735 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39736 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
39737 is a hexadecimal number.
39739 @item QTFrame:range:@var{start}:@var{end}
39740 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
39741 currently selected frame whose PC is between @var{start} (inclusive)
39742 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
39745 @item QTFrame:outside:@var{start}:@var{end}
39746 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
39747 frame @emph{outside} the given range of addresses (exclusive).
39750 @cindex @samp{qTMinFTPILen} packet
39751 This packet requests the minimum length of instruction at which a fast
39752 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
39753 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
39754 it depends on the target system being able to create trampolines in
39755 the first 64K of memory, which might or might not be possible for that
39756 system. So the reply to this packet will be 4 if it is able to
39763 The minimum instruction length is currently unknown.
39765 The minimum instruction length is @var{length}, where @var{length} is greater
39766 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
39767 that a fast tracepoint may be placed on any instruction regardless of size.
39769 An error has occurred.
39771 An empty reply indicates that the request is not supported by the stub.
39775 @cindex @samp{QTStart} packet
39776 Begin the tracepoint experiment. Begin collecting data from
39777 tracepoint hits in the trace frame buffer. This packet supports the
39778 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
39779 instruction reply packet}).
39782 @cindex @samp{QTStop} packet
39783 End the tracepoint experiment. Stop collecting trace frames.
39785 @item QTEnable:@var{n}:@var{addr}
39787 @cindex @samp{QTEnable} packet
39788 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
39789 experiment. If the tracepoint was previously disabled, then collection
39790 of data from it will resume.
39792 @item QTDisable:@var{n}:@var{addr}
39794 @cindex @samp{QTDisable} packet
39795 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
39796 experiment. No more data will be collected from the tracepoint unless
39797 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
39800 @cindex @samp{QTinit} packet
39801 Clear the table of tracepoints, and empty the trace frame buffer.
39803 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
39804 @cindex @samp{QTro} packet
39805 Establish the given ranges of memory as ``transparent''. The stub
39806 will answer requests for these ranges from memory's current contents,
39807 if they were not collected as part of the tracepoint hit.
39809 @value{GDBN} uses this to mark read-only regions of memory, like those
39810 containing program code. Since these areas never change, they should
39811 still have the same contents they did when the tracepoint was hit, so
39812 there's no reason for the stub to refuse to provide their contents.
39814 @item QTDisconnected:@var{value}
39815 @cindex @samp{QTDisconnected} packet
39816 Set the choice to what to do with the tracing run when @value{GDBN}
39817 disconnects from the target. A @var{value} of 1 directs the target to
39818 continue the tracing run, while 0 tells the target to stop tracing if
39819 @value{GDBN} is no longer in the picture.
39822 @cindex @samp{qTStatus} packet
39823 Ask the stub if there is a trace experiment running right now.
39825 The reply has the form:
39829 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
39830 @var{running} is a single digit @code{1} if the trace is presently
39831 running, or @code{0} if not. It is followed by semicolon-separated
39832 optional fields that an agent may use to report additional status.
39836 If the trace is not running, the agent may report any of several
39837 explanations as one of the optional fields:
39842 No trace has been run yet.
39844 @item tstop[:@var{text}]:0
39845 The trace was stopped by a user-originated stop command. The optional
39846 @var{text} field is a user-supplied string supplied as part of the
39847 stop command (for instance, an explanation of why the trace was
39848 stopped manually). It is hex-encoded.
39851 The trace stopped because the trace buffer filled up.
39853 @item tdisconnected:0
39854 The trace stopped because @value{GDBN} disconnected from the target.
39856 @item tpasscount:@var{tpnum}
39857 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
39859 @item terror:@var{text}:@var{tpnum}
39860 The trace stopped because tracepoint @var{tpnum} had an error. The
39861 string @var{text} is available to describe the nature of the error
39862 (for instance, a divide by zero in the condition expression).
39863 @var{text} is hex encoded.
39866 The trace stopped for some other reason.
39870 Additional optional fields supply statistical and other information.
39871 Although not required, they are extremely useful for users monitoring
39872 the progress of a trace run. If a trace has stopped, and these
39873 numbers are reported, they must reflect the state of the just-stopped
39878 @item tframes:@var{n}
39879 The number of trace frames in the buffer.
39881 @item tcreated:@var{n}
39882 The total number of trace frames created during the run. This may
39883 be larger than the trace frame count, if the buffer is circular.
39885 @item tsize:@var{n}
39886 The total size of the trace buffer, in bytes.
39888 @item tfree:@var{n}
39889 The number of bytes still unused in the buffer.
39891 @item circular:@var{n}
39892 The value of the circular trace buffer flag. @code{1} means that the
39893 trace buffer is circular and old trace frames will be discarded if
39894 necessary to make room, @code{0} means that the trace buffer is linear
39897 @item disconn:@var{n}
39898 The value of the disconnected tracing flag. @code{1} means that
39899 tracing will continue after @value{GDBN} disconnects, @code{0} means
39900 that the trace run will stop.
39904 @item qTP:@var{tp}:@var{addr}
39905 @cindex tracepoint status, remote request
39906 @cindex @samp{qTP} packet
39907 Ask the stub for the current state of tracepoint number @var{tp} at
39908 address @var{addr}.
39912 @item V@var{hits}:@var{usage}
39913 The tracepoint has been hit @var{hits} times so far during the trace
39914 run, and accounts for @var{usage} in the trace buffer. Note that
39915 @code{while-stepping} steps are not counted as separate hits, but the
39916 steps' space consumption is added into the usage number.
39920 @item qTV:@var{var}
39921 @cindex trace state variable value, remote request
39922 @cindex @samp{qTV} packet
39923 Ask the stub for the value of the trace state variable number @var{var}.
39928 The value of the variable is @var{value}. This will be the current
39929 value of the variable if the user is examining a running target, or a
39930 saved value if the variable was collected in the trace frame that the
39931 user is looking at. Note that multiple requests may result in
39932 different reply values, such as when requesting values while the
39933 program is running.
39936 The value of the variable is unknown. This would occur, for example,
39937 if the user is examining a trace frame in which the requested variable
39942 @cindex @samp{qTfP} packet
39944 @cindex @samp{qTsP} packet
39945 These packets request data about tracepoints that are being used by
39946 the target. @value{GDBN} sends @code{qTfP} to get the first piece
39947 of data, and multiple @code{qTsP} to get additional pieces. Replies
39948 to these packets generally take the form of the @code{QTDP} packets
39949 that define tracepoints. (FIXME add detailed syntax)
39952 @cindex @samp{qTfV} packet
39954 @cindex @samp{qTsV} packet
39955 These packets request data about trace state variables that are on the
39956 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
39957 and multiple @code{qTsV} to get additional variables. Replies to
39958 these packets follow the syntax of the @code{QTDV} packets that define
39959 trace state variables.
39965 @cindex @samp{qTfSTM} packet
39966 @cindex @samp{qTsSTM} packet
39967 These packets request data about static tracepoint markers that exist
39968 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
39969 first piece of data, and multiple @code{qTsSTM} to get additional
39970 pieces. Replies to these packets take the following form:
39974 @item m @var{address}:@var{id}:@var{extra}
39976 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
39977 a comma-separated list of markers
39979 (lower case letter @samp{L}) denotes end of list.
39981 An error occurred. @var{nn} are hex digits.
39983 An empty reply indicates that the request is not supported by the
39987 @var{address} is encoded in hex.
39988 @var{id} and @var{extra} are strings encoded in hex.
39990 In response to each query, the target will reply with a list of one or
39991 more markers, separated by commas. @value{GDBN} will respond to each
39992 reply with a request for more markers (using the @samp{qs} form of the
39993 query), until the target responds with @samp{l} (lower-case ell, for
39996 @item qTSTMat:@var{address}
39998 @cindex @samp{qTSTMat} packet
39999 This packets requests data about static tracepoint markers in the
40000 target program at @var{address}. Replies to this packet follow the
40001 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
40002 tracepoint markers.
40004 @item QTSave:@var{filename}
40005 @cindex @samp{QTSave} packet
40006 This packet directs the target to save trace data to the file name
40007 @var{filename} in the target's filesystem. @var{filename} is encoded
40008 as a hex string; the interpretation of the file name (relative vs
40009 absolute, wild cards, etc) is up to the target.
40011 @item qTBuffer:@var{offset},@var{len}
40012 @cindex @samp{qTBuffer} packet
40013 Return up to @var{len} bytes of the current contents of trace buffer,
40014 starting at @var{offset}. The trace buffer is treated as if it were
40015 a contiguous collection of traceframes, as per the trace file format.
40016 The reply consists as many hex-encoded bytes as the target can deliver
40017 in a packet; it is not an error to return fewer than were asked for.
40018 A reply consisting of just @code{l} indicates that no bytes are
40021 @item QTBuffer:circular:@var{value}
40022 This packet directs the target to use a circular trace buffer if
40023 @var{value} is 1, or a linear buffer if the value is 0.
40025 @item QTBuffer:size:@var{size}
40026 @anchor{QTBuffer-size}
40027 @cindex @samp{QTBuffer size} packet
40028 This packet directs the target to make the trace buffer be of size
40029 @var{size} if possible. A value of @code{-1} tells the target to
40030 use whatever size it prefers.
40032 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
40033 @cindex @samp{QTNotes} packet
40034 This packet adds optional textual notes to the trace run. Allowable
40035 types include @code{user}, @code{notes}, and @code{tstop}, the
40036 @var{text} fields are arbitrary strings, hex-encoded.
40040 @subsection Relocate instruction reply packet
40041 When installing fast tracepoints in memory, the target may need to
40042 relocate the instruction currently at the tracepoint address to a
40043 different address in memory. For most instructions, a simple copy is
40044 enough, but, for example, call instructions that implicitly push the
40045 return address on the stack, and relative branches or other
40046 PC-relative instructions require offset adjustment, so that the effect
40047 of executing the instruction at a different address is the same as if
40048 it had executed in the original location.
40050 In response to several of the tracepoint packets, the target may also
40051 respond with a number of intermediate @samp{qRelocInsn} request
40052 packets before the final result packet, to have @value{GDBN} handle
40053 this relocation operation. If a packet supports this mechanism, its
40054 documentation will explicitly say so. See for example the above
40055 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
40056 format of the request is:
40059 @item qRelocInsn:@var{from};@var{to}
40061 This requests @value{GDBN} to copy instruction at address @var{from}
40062 to address @var{to}, possibly adjusted so that executing the
40063 instruction at @var{to} has the same effect as executing it at
40064 @var{from}. @value{GDBN} writes the adjusted instruction to target
40065 memory starting at @var{to}.
40070 @item qRelocInsn:@var{adjusted_size}
40071 Informs the stub the relocation is complete. @var{adjusted_size} is
40072 the length in bytes of resulting relocated instruction sequence.
40074 A badly formed request was detected, or an error was encountered while
40075 relocating the instruction.
40078 @node Host I/O Packets
40079 @section Host I/O Packets
40080 @cindex Host I/O, remote protocol
40081 @cindex file transfer, remote protocol
40083 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
40084 operations on the far side of a remote link. For example, Host I/O is
40085 used to upload and download files to a remote target with its own
40086 filesystem. Host I/O uses the same constant values and data structure
40087 layout as the target-initiated File-I/O protocol. However, the
40088 Host I/O packets are structured differently. The target-initiated
40089 protocol relies on target memory to store parameters and buffers.
40090 Host I/O requests are initiated by @value{GDBN}, and the
40091 target's memory is not involved. @xref{File-I/O Remote Protocol
40092 Extension}, for more details on the target-initiated protocol.
40094 The Host I/O request packets all encode a single operation along with
40095 its arguments. They have this format:
40099 @item vFile:@var{operation}: @var{parameter}@dots{}
40100 @var{operation} is the name of the particular request; the target
40101 should compare the entire packet name up to the second colon when checking
40102 for a supported operation. The format of @var{parameter} depends on
40103 the operation. Numbers are always passed in hexadecimal. Negative
40104 numbers have an explicit minus sign (i.e.@: two's complement is not
40105 used). Strings (e.g.@: filenames) are encoded as a series of
40106 hexadecimal bytes. The last argument to a system call may be a
40107 buffer of escaped binary data (@pxref{Binary Data}).
40111 The valid responses to Host I/O packets are:
40115 @item F @var{result} [, @var{errno}] [; @var{attachment}]
40116 @var{result} is the integer value returned by this operation, usually
40117 non-negative for success and -1 for errors. If an error has occured,
40118 @var{errno} will be included in the result. @var{errno} will have a
40119 value defined by the File-I/O protocol (@pxref{Errno Values}). For
40120 operations which return data, @var{attachment} supplies the data as a
40121 binary buffer. Binary buffers in response packets are escaped in the
40122 normal way (@pxref{Binary Data}). See the individual packet
40123 documentation for the interpretation of @var{result} and
40127 An empty response indicates that this operation is not recognized.
40131 These are the supported Host I/O operations:
40134 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
40135 Open a file at @var{pathname} and return a file descriptor for it, or
40136 return -1 if an error occurs. @var{pathname} is a string,
40137 @var{flags} is an integer indicating a mask of open flags
40138 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
40139 of mode bits to use if the file is created (@pxref{mode_t Values}).
40140 @xref{open}, for details of the open flags and mode values.
40142 @item vFile:close: @var{fd}
40143 Close the open file corresponding to @var{fd} and return 0, or
40144 -1 if an error occurs.
40146 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
40147 Read data from the open file corresponding to @var{fd}. Up to
40148 @var{count} bytes will be read from the file, starting at @var{offset}
40149 relative to the start of the file. The target may read fewer bytes;
40150 common reasons include packet size limits and an end-of-file
40151 condition. The number of bytes read is returned. Zero should only be
40152 returned for a successful read at the end of the file, or if
40153 @var{count} was zero.
40155 The data read should be returned as a binary attachment on success.
40156 If zero bytes were read, the response should include an empty binary
40157 attachment (i.e.@: a trailing semicolon). The return value is the
40158 number of target bytes read; the binary attachment may be longer if
40159 some characters were escaped.
40161 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
40162 Write @var{data} (a binary buffer) to the open file corresponding
40163 to @var{fd}. Start the write at @var{offset} from the start of the
40164 file. Unlike many @code{write} system calls, there is no
40165 separate @var{count} argument; the length of @var{data} in the
40166 packet is used. @samp{vFile:write} returns the number of bytes written,
40167 which may be shorter than the length of @var{data}, or -1 if an
40170 @item vFile:unlink: @var{pathname}
40171 Delete the file at @var{pathname} on the target. Return 0,
40172 or -1 if an error occurs. @var{pathname} is a string.
40174 @item vFile:readlink: @var{filename}
40175 Read value of symbolic link @var{filename} on the target. Return
40176 the number of bytes read, or -1 if an error occurs.
40178 The data read should be returned as a binary attachment on success.
40179 If zero bytes were read, the response should include an empty binary
40180 attachment (i.e.@: a trailing semicolon). The return value is the
40181 number of target bytes read; the binary attachment may be longer if
40182 some characters were escaped.
40187 @section Interrupts
40188 @cindex interrupts (remote protocol)
40190 When a program on the remote target is running, @value{GDBN} may
40191 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
40192 a @code{BREAK} followed by @code{g},
40193 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
40195 The precise meaning of @code{BREAK} is defined by the transport
40196 mechanism and may, in fact, be undefined. @value{GDBN} does not
40197 currently define a @code{BREAK} mechanism for any of the network
40198 interfaces except for TCP, in which case @value{GDBN} sends the
40199 @code{telnet} BREAK sequence.
40201 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
40202 transport mechanisms. It is represented by sending the single byte
40203 @code{0x03} without any of the usual packet overhead described in
40204 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
40205 transmitted as part of a packet, it is considered to be packet data
40206 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
40207 (@pxref{X packet}), used for binary downloads, may include an unescaped
40208 @code{0x03} as part of its packet.
40210 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
40211 When Linux kernel receives this sequence from serial port,
40212 it stops execution and connects to gdb.
40214 Stubs are not required to recognize these interrupt mechanisms and the
40215 precise meaning associated with receipt of the interrupt is
40216 implementation defined. If the target supports debugging of multiple
40217 threads and/or processes, it should attempt to interrupt all
40218 currently-executing threads and processes.
40219 If the stub is successful at interrupting the
40220 running program, it should send one of the stop
40221 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
40222 of successfully stopping the program in all-stop mode, and a stop reply
40223 for each stopped thread in non-stop mode.
40224 Interrupts received while the
40225 program is stopped are discarded.
40227 @node Notification Packets
40228 @section Notification Packets
40229 @cindex notification packets
40230 @cindex packets, notification
40232 The @value{GDBN} remote serial protocol includes @dfn{notifications},
40233 packets that require no acknowledgment. Both the GDB and the stub
40234 may send notifications (although the only notifications defined at
40235 present are sent by the stub). Notifications carry information
40236 without incurring the round-trip latency of an acknowledgment, and so
40237 are useful for low-impact communications where occasional packet loss
40240 A notification packet has the form @samp{% @var{data} #
40241 @var{checksum}}, where @var{data} is the content of the notification,
40242 and @var{checksum} is a checksum of @var{data}, computed and formatted
40243 as for ordinary @value{GDBN} packets. A notification's @var{data}
40244 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
40245 receiving a notification, the recipient sends no @samp{+} or @samp{-}
40246 to acknowledge the notification's receipt or to report its corruption.
40248 Every notification's @var{data} begins with a name, which contains no
40249 colon characters, followed by a colon character.
40251 Recipients should silently ignore corrupted notifications and
40252 notifications they do not understand. Recipients should restart
40253 timeout periods on receipt of a well-formed notification, whether or
40254 not they understand it.
40256 Senders should only send the notifications described here when this
40257 protocol description specifies that they are permitted. In the
40258 future, we may extend the protocol to permit existing notifications in
40259 new contexts; this rule helps older senders avoid confusing newer
40262 (Older versions of @value{GDBN} ignore bytes received until they see
40263 the @samp{$} byte that begins an ordinary packet, so new stubs may
40264 transmit notifications without fear of confusing older clients. There
40265 are no notifications defined for @value{GDBN} to send at the moment, but we
40266 assume that most older stubs would ignore them, as well.)
40268 Each notification is comprised of three parts:
40270 @item @var{name}:@var{event}
40271 The notification packet is sent by the side that initiates the
40272 exchange (currently, only the stub does that), with @var{event}
40273 carrying the specific information about the notification.
40274 @var{name} is the name of the notification.
40276 The acknowledge sent by the other side, usually @value{GDBN}, to
40277 acknowledge the exchange and request the event.
40280 The purpose of an asynchronous notification mechanism is to report to
40281 @value{GDBN} that something interesting happened in the remote stub.
40283 The remote stub may send notification @var{name}:@var{event}
40284 at any time, but @value{GDBN} acknowledges the notification when
40285 appropriate. The notification event is pending before @value{GDBN}
40286 acknowledges. Only one notification at a time may be pending; if
40287 additional events occur before @value{GDBN} has acknowledged the
40288 previous notification, they must be queued by the stub for later
40289 synchronous transmission in response to @var{ack} packets from
40290 @value{GDBN}. Because the notification mechanism is unreliable,
40291 the stub is permitted to resend a notification if it believes
40292 @value{GDBN} may not have received it.
40294 Specifically, notifications may appear when @value{GDBN} is not
40295 otherwise reading input from the stub, or when @value{GDBN} is
40296 expecting to read a normal synchronous response or a
40297 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
40298 Notification packets are distinct from any other communication from
40299 the stub so there is no ambiguity.
40301 After receiving a notification, @value{GDBN} shall acknowledge it by
40302 sending a @var{ack} packet as a regular, synchronous request to the
40303 stub. Such acknowledgment is not required to happen immediately, as
40304 @value{GDBN} is permitted to send other, unrelated packets to the
40305 stub first, which the stub should process normally.
40307 Upon receiving a @var{ack} packet, if the stub has other queued
40308 events to report to @value{GDBN}, it shall respond by sending a
40309 normal @var{event}. @value{GDBN} shall then send another @var{ack}
40310 packet to solicit further responses; again, it is permitted to send
40311 other, unrelated packets as well which the stub should process
40314 If the stub receives a @var{ack} packet and there are no additional
40315 @var{event} to report, the stub shall return an @samp{OK} response.
40316 At this point, @value{GDBN} has finished processing a notification
40317 and the stub has completed sending any queued events. @value{GDBN}
40318 won't accept any new notifications until the final @samp{OK} is
40319 received . If further notification events occur, the stub shall send
40320 a new notification, @value{GDBN} shall accept the notification, and
40321 the process shall be repeated.
40323 The process of asynchronous notification can be illustrated by the
40326 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
40329 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
40331 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
40336 The following notifications are defined:
40337 @multitable @columnfractions 0.12 0.12 0.38 0.38
40346 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
40347 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
40348 for information on how these notifications are acknowledged by
40350 @tab Report an asynchronous stop event in non-stop mode.
40354 @node Remote Non-Stop
40355 @section Remote Protocol Support for Non-Stop Mode
40357 @value{GDBN}'s remote protocol supports non-stop debugging of
40358 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
40359 supports non-stop mode, it should report that to @value{GDBN} by including
40360 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
40362 @value{GDBN} typically sends a @samp{QNonStop} packet only when
40363 establishing a new connection with the stub. Entering non-stop mode
40364 does not alter the state of any currently-running threads, but targets
40365 must stop all threads in any already-attached processes when entering
40366 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
40367 probe the target state after a mode change.
40369 In non-stop mode, when an attached process encounters an event that
40370 would otherwise be reported with a stop reply, it uses the
40371 asynchronous notification mechanism (@pxref{Notification Packets}) to
40372 inform @value{GDBN}. In contrast to all-stop mode, where all threads
40373 in all processes are stopped when a stop reply is sent, in non-stop
40374 mode only the thread reporting the stop event is stopped. That is,
40375 when reporting a @samp{S} or @samp{T} response to indicate completion
40376 of a step operation, hitting a breakpoint, or a fault, only the
40377 affected thread is stopped; any other still-running threads continue
40378 to run. When reporting a @samp{W} or @samp{X} response, all running
40379 threads belonging to other attached processes continue to run.
40381 In non-stop mode, the target shall respond to the @samp{?} packet as
40382 follows. First, any incomplete stop reply notification/@samp{vStopped}
40383 sequence in progress is abandoned. The target must begin a new
40384 sequence reporting stop events for all stopped threads, whether or not
40385 it has previously reported those events to @value{GDBN}. The first
40386 stop reply is sent as a synchronous reply to the @samp{?} packet, and
40387 subsequent stop replies are sent as responses to @samp{vStopped} packets
40388 using the mechanism described above. The target must not send
40389 asynchronous stop reply notifications until the sequence is complete.
40390 If all threads are running when the target receives the @samp{?} packet,
40391 or if the target is not attached to any process, it shall respond
40394 @node Packet Acknowledgment
40395 @section Packet Acknowledgment
40397 @cindex acknowledgment, for @value{GDBN} remote
40398 @cindex packet acknowledgment, for @value{GDBN} remote
40399 By default, when either the host or the target machine receives a packet,
40400 the first response expected is an acknowledgment: either @samp{+} (to indicate
40401 the package was received correctly) or @samp{-} (to request retransmission).
40402 This mechanism allows the @value{GDBN} remote protocol to operate over
40403 unreliable transport mechanisms, such as a serial line.
40405 In cases where the transport mechanism is itself reliable (such as a pipe or
40406 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
40407 It may be desirable to disable them in that case to reduce communication
40408 overhead, or for other reasons. This can be accomplished by means of the
40409 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
40411 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
40412 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
40413 and response format still includes the normal checksum, as described in
40414 @ref{Overview}, but the checksum may be ignored by the receiver.
40416 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
40417 no-acknowledgment mode, it should report that to @value{GDBN}
40418 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
40419 @pxref{qSupported}.
40420 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
40421 disabled via the @code{set remote noack-packet off} command
40422 (@pxref{Remote Configuration}),
40423 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
40424 Only then may the stub actually turn off packet acknowledgments.
40425 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
40426 response, which can be safely ignored by the stub.
40428 Note that @code{set remote noack-packet} command only affects negotiation
40429 between @value{GDBN} and the stub when subsequent connections are made;
40430 it does not affect the protocol acknowledgment state for any current
40432 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
40433 new connection is established,
40434 there is also no protocol request to re-enable the acknowledgments
40435 for the current connection, once disabled.
40440 Example sequence of a target being re-started. Notice how the restart
40441 does not get any direct output:
40446 @emph{target restarts}
40449 <- @code{T001:1234123412341234}
40453 Example sequence of a target being stepped by a single instruction:
40456 -> @code{G1445@dots{}}
40461 <- @code{T001:1234123412341234}
40465 <- @code{1455@dots{}}
40469 @node File-I/O Remote Protocol Extension
40470 @section File-I/O Remote Protocol Extension
40471 @cindex File-I/O remote protocol extension
40474 * File-I/O Overview::
40475 * Protocol Basics::
40476 * The F Request Packet::
40477 * The F Reply Packet::
40478 * The Ctrl-C Message::
40480 * List of Supported Calls::
40481 * Protocol-specific Representation of Datatypes::
40483 * File-I/O Examples::
40486 @node File-I/O Overview
40487 @subsection File-I/O Overview
40488 @cindex file-i/o overview
40490 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
40491 target to use the host's file system and console I/O to perform various
40492 system calls. System calls on the target system are translated into a
40493 remote protocol packet to the host system, which then performs the needed
40494 actions and returns a response packet to the target system.
40495 This simulates file system operations even on targets that lack file systems.
40497 The protocol is defined to be independent of both the host and target systems.
40498 It uses its own internal representation of datatypes and values. Both
40499 @value{GDBN} and the target's @value{GDBN} stub are responsible for
40500 translating the system-dependent value representations into the internal
40501 protocol representations when data is transmitted.
40503 The communication is synchronous. A system call is possible only when
40504 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
40505 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
40506 the target is stopped to allow deterministic access to the target's
40507 memory. Therefore File-I/O is not interruptible by target signals. On
40508 the other hand, it is possible to interrupt File-I/O by a user interrupt
40509 (@samp{Ctrl-C}) within @value{GDBN}.
40511 The target's request to perform a host system call does not finish
40512 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
40513 after finishing the system call, the target returns to continuing the
40514 previous activity (continue, step). No additional continue or step
40515 request from @value{GDBN} is required.
40518 (@value{GDBP}) continue
40519 <- target requests 'system call X'
40520 target is stopped, @value{GDBN} executes system call
40521 -> @value{GDBN} returns result
40522 ... target continues, @value{GDBN} returns to wait for the target
40523 <- target hits breakpoint and sends a Txx packet
40526 The protocol only supports I/O on the console and to regular files on
40527 the host file system. Character or block special devices, pipes,
40528 named pipes, sockets or any other communication method on the host
40529 system are not supported by this protocol.
40531 File I/O is not supported in non-stop mode.
40533 @node Protocol Basics
40534 @subsection Protocol Basics
40535 @cindex protocol basics, file-i/o
40537 The File-I/O protocol uses the @code{F} packet as the request as well
40538 as reply packet. Since a File-I/O system call can only occur when
40539 @value{GDBN} is waiting for a response from the continuing or stepping target,
40540 the File-I/O request is a reply that @value{GDBN} has to expect as a result
40541 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
40542 This @code{F} packet contains all information needed to allow @value{GDBN}
40543 to call the appropriate host system call:
40547 A unique identifier for the requested system call.
40550 All parameters to the system call. Pointers are given as addresses
40551 in the target memory address space. Pointers to strings are given as
40552 pointer/length pair. Numerical values are given as they are.
40553 Numerical control flags are given in a protocol-specific representation.
40557 At this point, @value{GDBN} has to perform the following actions.
40561 If the parameters include pointer values to data needed as input to a
40562 system call, @value{GDBN} requests this data from the target with a
40563 standard @code{m} packet request. This additional communication has to be
40564 expected by the target implementation and is handled as any other @code{m}
40568 @value{GDBN} translates all value from protocol representation to host
40569 representation as needed. Datatypes are coerced into the host types.
40572 @value{GDBN} calls the system call.
40575 It then coerces datatypes back to protocol representation.
40578 If the system call is expected to return data in buffer space specified
40579 by pointer parameters to the call, the data is transmitted to the
40580 target using a @code{M} or @code{X} packet. This packet has to be expected
40581 by the target implementation and is handled as any other @code{M} or @code{X}
40586 Eventually @value{GDBN} replies with another @code{F} packet which contains all
40587 necessary information for the target to continue. This at least contains
40594 @code{errno}, if has been changed by the system call.
40601 After having done the needed type and value coercion, the target continues
40602 the latest continue or step action.
40604 @node The F Request Packet
40605 @subsection The @code{F} Request Packet
40606 @cindex file-i/o request packet
40607 @cindex @code{F} request packet
40609 The @code{F} request packet has the following format:
40612 @item F@var{call-id},@var{parameter@dots{}}
40614 @var{call-id} is the identifier to indicate the host system call to be called.
40615 This is just the name of the function.
40617 @var{parameter@dots{}} are the parameters to the system call.
40618 Parameters are hexadecimal integer values, either the actual values in case
40619 of scalar datatypes, pointers to target buffer space in case of compound
40620 datatypes and unspecified memory areas, or pointer/length pairs in case
40621 of string parameters. These are appended to the @var{call-id} as a
40622 comma-delimited list. All values are transmitted in ASCII
40623 string representation, pointer/length pairs separated by a slash.
40629 @node The F Reply Packet
40630 @subsection The @code{F} Reply Packet
40631 @cindex file-i/o reply packet
40632 @cindex @code{F} reply packet
40634 The @code{F} reply packet has the following format:
40638 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
40640 @var{retcode} is the return code of the system call as hexadecimal value.
40642 @var{errno} is the @code{errno} set by the call, in protocol-specific
40644 This parameter can be omitted if the call was successful.
40646 @var{Ctrl-C flag} is only sent if the user requested a break. In this
40647 case, @var{errno} must be sent as well, even if the call was successful.
40648 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
40655 or, if the call was interrupted before the host call has been performed:
40662 assuming 4 is the protocol-specific representation of @code{EINTR}.
40667 @node The Ctrl-C Message
40668 @subsection The @samp{Ctrl-C} Message
40669 @cindex ctrl-c message, in file-i/o protocol
40671 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
40672 reply packet (@pxref{The F Reply Packet}),
40673 the target should behave as if it had
40674 gotten a break message. The meaning for the target is ``system call
40675 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
40676 (as with a break message) and return to @value{GDBN} with a @code{T02}
40679 It's important for the target to know in which
40680 state the system call was interrupted. There are two possible cases:
40684 The system call hasn't been performed on the host yet.
40687 The system call on the host has been finished.
40691 These two states can be distinguished by the target by the value of the
40692 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
40693 call hasn't been performed. This is equivalent to the @code{EINTR} handling
40694 on POSIX systems. In any other case, the target may presume that the
40695 system call has been finished --- successfully or not --- and should behave
40696 as if the break message arrived right after the system call.
40698 @value{GDBN} must behave reliably. If the system call has not been called
40699 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
40700 @code{errno} in the packet. If the system call on the host has been finished
40701 before the user requests a break, the full action must be finished by
40702 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
40703 The @code{F} packet may only be sent when either nothing has happened
40704 or the full action has been completed.
40707 @subsection Console I/O
40708 @cindex console i/o as part of file-i/o
40710 By default and if not explicitly closed by the target system, the file
40711 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
40712 on the @value{GDBN} console is handled as any other file output operation
40713 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
40714 by @value{GDBN} so that after the target read request from file descriptor
40715 0 all following typing is buffered until either one of the following
40720 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
40722 system call is treated as finished.
40725 The user presses @key{RET}. This is treated as end of input with a trailing
40729 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
40730 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
40734 If the user has typed more characters than fit in the buffer given to
40735 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
40736 either another @code{read(0, @dots{})} is requested by the target, or debugging
40737 is stopped at the user's request.
40740 @node List of Supported Calls
40741 @subsection List of Supported Calls
40742 @cindex list of supported file-i/o calls
40759 @unnumberedsubsubsec open
40760 @cindex open, file-i/o system call
40765 int open(const char *pathname, int flags);
40766 int open(const char *pathname, int flags, mode_t mode);
40770 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
40773 @var{flags} is the bitwise @code{OR} of the following values:
40777 If the file does not exist it will be created. The host
40778 rules apply as far as file ownership and time stamps
40782 When used with @code{O_CREAT}, if the file already exists it is
40783 an error and open() fails.
40786 If the file already exists and the open mode allows
40787 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
40788 truncated to zero length.
40791 The file is opened in append mode.
40794 The file is opened for reading only.
40797 The file is opened for writing only.
40800 The file is opened for reading and writing.
40804 Other bits are silently ignored.
40808 @var{mode} is the bitwise @code{OR} of the following values:
40812 User has read permission.
40815 User has write permission.
40818 Group has read permission.
40821 Group has write permission.
40824 Others have read permission.
40827 Others have write permission.
40831 Other bits are silently ignored.
40834 @item Return value:
40835 @code{open} returns the new file descriptor or -1 if an error
40842 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
40845 @var{pathname} refers to a directory.
40848 The requested access is not allowed.
40851 @var{pathname} was too long.
40854 A directory component in @var{pathname} does not exist.
40857 @var{pathname} refers to a device, pipe, named pipe or socket.
40860 @var{pathname} refers to a file on a read-only filesystem and
40861 write access was requested.
40864 @var{pathname} is an invalid pointer value.
40867 No space on device to create the file.
40870 The process already has the maximum number of files open.
40873 The limit on the total number of files open on the system
40877 The call was interrupted by the user.
40883 @unnumberedsubsubsec close
40884 @cindex close, file-i/o system call
40893 @samp{Fclose,@var{fd}}
40895 @item Return value:
40896 @code{close} returns zero on success, or -1 if an error occurred.
40902 @var{fd} isn't a valid open file descriptor.
40905 The call was interrupted by the user.
40911 @unnumberedsubsubsec read
40912 @cindex read, file-i/o system call
40917 int read(int fd, void *buf, unsigned int count);
40921 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
40923 @item Return value:
40924 On success, the number of bytes read is returned.
40925 Zero indicates end of file. If count is zero, read
40926 returns zero as well. On error, -1 is returned.
40932 @var{fd} is not a valid file descriptor or is not open for
40936 @var{bufptr} is an invalid pointer value.
40939 The call was interrupted by the user.
40945 @unnumberedsubsubsec write
40946 @cindex write, file-i/o system call
40951 int write(int fd, const void *buf, unsigned int count);
40955 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
40957 @item Return value:
40958 On success, the number of bytes written are returned.
40959 Zero indicates nothing was written. On error, -1
40966 @var{fd} is not a valid file descriptor or is not open for
40970 @var{bufptr} is an invalid pointer value.
40973 An attempt was made to write a file that exceeds the
40974 host-specific maximum file size allowed.
40977 No space on device to write the data.
40980 The call was interrupted by the user.
40986 @unnumberedsubsubsec lseek
40987 @cindex lseek, file-i/o system call
40992 long lseek (int fd, long offset, int flag);
40996 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
40998 @var{flag} is one of:
41002 The offset is set to @var{offset} bytes.
41005 The offset is set to its current location plus @var{offset}
41009 The offset is set to the size of the file plus @var{offset}
41013 @item Return value:
41014 On success, the resulting unsigned offset in bytes from
41015 the beginning of the file is returned. Otherwise, a
41016 value of -1 is returned.
41022 @var{fd} is not a valid open file descriptor.
41025 @var{fd} is associated with the @value{GDBN} console.
41028 @var{flag} is not a proper value.
41031 The call was interrupted by the user.
41037 @unnumberedsubsubsec rename
41038 @cindex rename, file-i/o system call
41043 int rename(const char *oldpath, const char *newpath);
41047 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
41049 @item Return value:
41050 On success, zero is returned. On error, -1 is returned.
41056 @var{newpath} is an existing directory, but @var{oldpath} is not a
41060 @var{newpath} is a non-empty directory.
41063 @var{oldpath} or @var{newpath} is a directory that is in use by some
41067 An attempt was made to make a directory a subdirectory
41071 A component used as a directory in @var{oldpath} or new
41072 path is not a directory. Or @var{oldpath} is a directory
41073 and @var{newpath} exists but is not a directory.
41076 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
41079 No access to the file or the path of the file.
41083 @var{oldpath} or @var{newpath} was too long.
41086 A directory component in @var{oldpath} or @var{newpath} does not exist.
41089 The file is on a read-only filesystem.
41092 The device containing the file has no room for the new
41096 The call was interrupted by the user.
41102 @unnumberedsubsubsec unlink
41103 @cindex unlink, file-i/o system call
41108 int unlink(const char *pathname);
41112 @samp{Funlink,@var{pathnameptr}/@var{len}}
41114 @item Return value:
41115 On success, zero is returned. On error, -1 is returned.
41121 No access to the file or the path of the file.
41124 The system does not allow unlinking of directories.
41127 The file @var{pathname} cannot be unlinked because it's
41128 being used by another process.
41131 @var{pathnameptr} is an invalid pointer value.
41134 @var{pathname} was too long.
41137 A directory component in @var{pathname} does not exist.
41140 A component of the path is not a directory.
41143 The file is on a read-only filesystem.
41146 The call was interrupted by the user.
41152 @unnumberedsubsubsec stat/fstat
41153 @cindex fstat, file-i/o system call
41154 @cindex stat, file-i/o system call
41159 int stat(const char *pathname, struct stat *buf);
41160 int fstat(int fd, struct stat *buf);
41164 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
41165 @samp{Ffstat,@var{fd},@var{bufptr}}
41167 @item Return value:
41168 On success, zero is returned. On error, -1 is returned.
41174 @var{fd} is not a valid open file.
41177 A directory component in @var{pathname} does not exist or the
41178 path is an empty string.
41181 A component of the path is not a directory.
41184 @var{pathnameptr} is an invalid pointer value.
41187 No access to the file or the path of the file.
41190 @var{pathname} was too long.
41193 The call was interrupted by the user.
41199 @unnumberedsubsubsec gettimeofday
41200 @cindex gettimeofday, file-i/o system call
41205 int gettimeofday(struct timeval *tv, void *tz);
41209 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
41211 @item Return value:
41212 On success, 0 is returned, -1 otherwise.
41218 @var{tz} is a non-NULL pointer.
41221 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
41227 @unnumberedsubsubsec isatty
41228 @cindex isatty, file-i/o system call
41233 int isatty(int fd);
41237 @samp{Fisatty,@var{fd}}
41239 @item Return value:
41240 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
41246 The call was interrupted by the user.
41251 Note that the @code{isatty} call is treated as a special case: it returns
41252 1 to the target if the file descriptor is attached
41253 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
41254 would require implementing @code{ioctl} and would be more complex than
41259 @unnumberedsubsubsec system
41260 @cindex system, file-i/o system call
41265 int system(const char *command);
41269 @samp{Fsystem,@var{commandptr}/@var{len}}
41271 @item Return value:
41272 If @var{len} is zero, the return value indicates whether a shell is
41273 available. A zero return value indicates a shell is not available.
41274 For non-zero @var{len}, the value returned is -1 on error and the
41275 return status of the command otherwise. Only the exit status of the
41276 command is returned, which is extracted from the host's @code{system}
41277 return value by calling @code{WEXITSTATUS(retval)}. In case
41278 @file{/bin/sh} could not be executed, 127 is returned.
41284 The call was interrupted by the user.
41289 @value{GDBN} takes over the full task of calling the necessary host calls
41290 to perform the @code{system} call. The return value of @code{system} on
41291 the host is simplified before it's returned
41292 to the target. Any termination signal information from the child process
41293 is discarded, and the return value consists
41294 entirely of the exit status of the called command.
41296 Due to security concerns, the @code{system} call is by default refused
41297 by @value{GDBN}. The user has to allow this call explicitly with the
41298 @code{set remote system-call-allowed 1} command.
41301 @item set remote system-call-allowed
41302 @kindex set remote system-call-allowed
41303 Control whether to allow the @code{system} calls in the File I/O
41304 protocol for the remote target. The default is zero (disabled).
41306 @item show remote system-call-allowed
41307 @kindex show remote system-call-allowed
41308 Show whether the @code{system} calls are allowed in the File I/O
41312 @node Protocol-specific Representation of Datatypes
41313 @subsection Protocol-specific Representation of Datatypes
41314 @cindex protocol-specific representation of datatypes, in file-i/o protocol
41317 * Integral Datatypes::
41319 * Memory Transfer::
41324 @node Integral Datatypes
41325 @unnumberedsubsubsec Integral Datatypes
41326 @cindex integral datatypes, in file-i/o protocol
41328 The integral datatypes used in the system calls are @code{int},
41329 @code{unsigned int}, @code{long}, @code{unsigned long},
41330 @code{mode_t}, and @code{time_t}.
41332 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
41333 implemented as 32 bit values in this protocol.
41335 @code{long} and @code{unsigned long} are implemented as 64 bit types.
41337 @xref{Limits}, for corresponding MIN and MAX values (similar to those
41338 in @file{limits.h}) to allow range checking on host and target.
41340 @code{time_t} datatypes are defined as seconds since the Epoch.
41342 All integral datatypes transferred as part of a memory read or write of a
41343 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
41346 @node Pointer Values
41347 @unnumberedsubsubsec Pointer Values
41348 @cindex pointer values, in file-i/o protocol
41350 Pointers to target data are transmitted as they are. An exception
41351 is made for pointers to buffers for which the length isn't
41352 transmitted as part of the function call, namely strings. Strings
41353 are transmitted as a pointer/length pair, both as hex values, e.g.@:
41360 which is a pointer to data of length 18 bytes at position 0x1aaf.
41361 The length is defined as the full string length in bytes, including
41362 the trailing null byte. For example, the string @code{"hello world"}
41363 at address 0x123456 is transmitted as
41369 @node Memory Transfer
41370 @unnumberedsubsubsec Memory Transfer
41371 @cindex memory transfer, in file-i/o protocol
41373 Structured data which is transferred using a memory read or write (for
41374 example, a @code{struct stat}) is expected to be in a protocol-specific format
41375 with all scalar multibyte datatypes being big endian. Translation to
41376 this representation needs to be done both by the target before the @code{F}
41377 packet is sent, and by @value{GDBN} before
41378 it transfers memory to the target. Transferred pointers to structured
41379 data should point to the already-coerced data at any time.
41383 @unnumberedsubsubsec struct stat
41384 @cindex struct stat, in file-i/o protocol
41386 The buffer of type @code{struct stat} used by the target and @value{GDBN}
41387 is defined as follows:
41391 unsigned int st_dev; /* device */
41392 unsigned int st_ino; /* inode */
41393 mode_t st_mode; /* protection */
41394 unsigned int st_nlink; /* number of hard links */
41395 unsigned int st_uid; /* user ID of owner */
41396 unsigned int st_gid; /* group ID of owner */
41397 unsigned int st_rdev; /* device type (if inode device) */
41398 unsigned long st_size; /* total size, in bytes */
41399 unsigned long st_blksize; /* blocksize for filesystem I/O */
41400 unsigned long st_blocks; /* number of blocks allocated */
41401 time_t st_atime; /* time of last access */
41402 time_t st_mtime; /* time of last modification */
41403 time_t st_ctime; /* time of last change */
41407 The integral datatypes conform to the definitions given in the
41408 appropriate section (see @ref{Integral Datatypes}, for details) so this
41409 structure is of size 64 bytes.
41411 The values of several fields have a restricted meaning and/or
41417 A value of 0 represents a file, 1 the console.
41420 No valid meaning for the target. Transmitted unchanged.
41423 Valid mode bits are described in @ref{Constants}. Any other
41424 bits have currently no meaning for the target.
41429 No valid meaning for the target. Transmitted unchanged.
41434 These values have a host and file system dependent
41435 accuracy. Especially on Windows hosts, the file system may not
41436 support exact timing values.
41439 The target gets a @code{struct stat} of the above representation and is
41440 responsible for coercing it to the target representation before
41443 Note that due to size differences between the host, target, and protocol
41444 representations of @code{struct stat} members, these members could eventually
41445 get truncated on the target.
41447 @node struct timeval
41448 @unnumberedsubsubsec struct timeval
41449 @cindex struct timeval, in file-i/o protocol
41451 The buffer of type @code{struct timeval} used by the File-I/O protocol
41452 is defined as follows:
41456 time_t tv_sec; /* second */
41457 long tv_usec; /* microsecond */
41461 The integral datatypes conform to the definitions given in the
41462 appropriate section (see @ref{Integral Datatypes}, for details) so this
41463 structure is of size 8 bytes.
41466 @subsection Constants
41467 @cindex constants, in file-i/o protocol
41469 The following values are used for the constants inside of the
41470 protocol. @value{GDBN} and target are responsible for translating these
41471 values before and after the call as needed.
41482 @unnumberedsubsubsec Open Flags
41483 @cindex open flags, in file-i/o protocol
41485 All values are given in hexadecimal representation.
41497 @node mode_t Values
41498 @unnumberedsubsubsec mode_t Values
41499 @cindex mode_t values, in file-i/o protocol
41501 All values are given in octal representation.
41518 @unnumberedsubsubsec Errno Values
41519 @cindex errno values, in file-i/o protocol
41521 All values are given in decimal representation.
41546 @code{EUNKNOWN} is used as a fallback error value if a host system returns
41547 any error value not in the list of supported error numbers.
41550 @unnumberedsubsubsec Lseek Flags
41551 @cindex lseek flags, in file-i/o protocol
41560 @unnumberedsubsubsec Limits
41561 @cindex limits, in file-i/o protocol
41563 All values are given in decimal representation.
41566 INT_MIN -2147483648
41568 UINT_MAX 4294967295
41569 LONG_MIN -9223372036854775808
41570 LONG_MAX 9223372036854775807
41571 ULONG_MAX 18446744073709551615
41574 @node File-I/O Examples
41575 @subsection File-I/O Examples
41576 @cindex file-i/o examples
41578 Example sequence of a write call, file descriptor 3, buffer is at target
41579 address 0x1234, 6 bytes should be written:
41582 <- @code{Fwrite,3,1234,6}
41583 @emph{request memory read from target}
41586 @emph{return "6 bytes written"}
41590 Example sequence of a read call, file descriptor 3, buffer is at target
41591 address 0x1234, 6 bytes should be read:
41594 <- @code{Fread,3,1234,6}
41595 @emph{request memory write to target}
41596 -> @code{X1234,6:XXXXXX}
41597 @emph{return "6 bytes read"}
41601 Example sequence of a read call, call fails on the host due to invalid
41602 file descriptor (@code{EBADF}):
41605 <- @code{Fread,3,1234,6}
41609 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
41613 <- @code{Fread,3,1234,6}
41618 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
41622 <- @code{Fread,3,1234,6}
41623 -> @code{X1234,6:XXXXXX}
41627 @node Library List Format
41628 @section Library List Format
41629 @cindex library list format, remote protocol
41631 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
41632 same process as your application to manage libraries. In this case,
41633 @value{GDBN} can use the loader's symbol table and normal memory
41634 operations to maintain a list of shared libraries. On other
41635 platforms, the operating system manages loaded libraries.
41636 @value{GDBN} can not retrieve the list of currently loaded libraries
41637 through memory operations, so it uses the @samp{qXfer:libraries:read}
41638 packet (@pxref{qXfer library list read}) instead. The remote stub
41639 queries the target's operating system and reports which libraries
41642 The @samp{qXfer:libraries:read} packet returns an XML document which
41643 lists loaded libraries and their offsets. Each library has an
41644 associated name and one or more segment or section base addresses,
41645 which report where the library was loaded in memory.
41647 For the common case of libraries that are fully linked binaries, the
41648 library should have a list of segments. If the target supports
41649 dynamic linking of a relocatable object file, its library XML element
41650 should instead include a list of allocated sections. The segment or
41651 section bases are start addresses, not relocation offsets; they do not
41652 depend on the library's link-time base addresses.
41654 @value{GDBN} must be linked with the Expat library to support XML
41655 library lists. @xref{Expat}.
41657 A simple memory map, with one loaded library relocated by a single
41658 offset, looks like this:
41662 <library name="/lib/libc.so.6">
41663 <segment address="0x10000000"/>
41668 Another simple memory map, with one loaded library with three
41669 allocated sections (.text, .data, .bss), looks like this:
41673 <library name="sharedlib.o">
41674 <section address="0x10000000"/>
41675 <section address="0x20000000"/>
41676 <section address="0x30000000"/>
41681 The format of a library list is described by this DTD:
41684 <!-- library-list: Root element with versioning -->
41685 <!ELEMENT library-list (library)*>
41686 <!ATTLIST library-list version CDATA #FIXED "1.0">
41687 <!ELEMENT library (segment*, section*)>
41688 <!ATTLIST library name CDATA #REQUIRED>
41689 <!ELEMENT segment EMPTY>
41690 <!ATTLIST segment address CDATA #REQUIRED>
41691 <!ELEMENT section EMPTY>
41692 <!ATTLIST section address CDATA #REQUIRED>
41695 In addition, segments and section descriptors cannot be mixed within a
41696 single library element, and you must supply at least one segment or
41697 section for each library.
41699 @node Library List Format for SVR4 Targets
41700 @section Library List Format for SVR4 Targets
41701 @cindex library list format, remote protocol
41703 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
41704 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
41705 shared libraries. Still a special library list provided by this packet is
41706 more efficient for the @value{GDBN} remote protocol.
41708 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
41709 loaded libraries and their SVR4 linker parameters. For each library on SVR4
41710 target, the following parameters are reported:
41714 @code{name}, the absolute file name from the @code{l_name} field of
41715 @code{struct link_map}.
41717 @code{lm} with address of @code{struct link_map} used for TLS
41718 (Thread Local Storage) access.
41720 @code{l_addr}, the displacement as read from the field @code{l_addr} of
41721 @code{struct link_map}. For prelinked libraries this is not an absolute
41722 memory address. It is a displacement of absolute memory address against
41723 address the file was prelinked to during the library load.
41725 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
41728 Additionally the single @code{main-lm} attribute specifies address of
41729 @code{struct link_map} used for the main executable. This parameter is used
41730 for TLS access and its presence is optional.
41732 @value{GDBN} must be linked with the Expat library to support XML
41733 SVR4 library lists. @xref{Expat}.
41735 A simple memory map, with two loaded libraries (which do not use prelink),
41739 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
41740 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
41742 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
41744 </library-list-svr>
41747 The format of an SVR4 library list is described by this DTD:
41750 <!-- library-list-svr4: Root element with versioning -->
41751 <!ELEMENT library-list-svr4 (library)*>
41752 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
41753 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
41754 <!ELEMENT library EMPTY>
41755 <!ATTLIST library name CDATA #REQUIRED>
41756 <!ATTLIST library lm CDATA #REQUIRED>
41757 <!ATTLIST library l_addr CDATA #REQUIRED>
41758 <!ATTLIST library l_ld CDATA #REQUIRED>
41761 @node Memory Map Format
41762 @section Memory Map Format
41763 @cindex memory map format
41765 To be able to write into flash memory, @value{GDBN} needs to obtain a
41766 memory map from the target. This section describes the format of the
41769 The memory map is obtained using the @samp{qXfer:memory-map:read}
41770 (@pxref{qXfer memory map read}) packet and is an XML document that
41771 lists memory regions.
41773 @value{GDBN} must be linked with the Expat library to support XML
41774 memory maps. @xref{Expat}.
41776 The top-level structure of the document is shown below:
41779 <?xml version="1.0"?>
41780 <!DOCTYPE memory-map
41781 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41782 "http://sourceware.org/gdb/gdb-memory-map.dtd">
41788 Each region can be either:
41793 A region of RAM starting at @var{addr} and extending for @var{length}
41797 <memory type="ram" start="@var{addr}" length="@var{length}"/>
41802 A region of read-only memory:
41805 <memory type="rom" start="@var{addr}" length="@var{length}"/>
41810 A region of flash memory, with erasure blocks @var{blocksize}
41814 <memory type="flash" start="@var{addr}" length="@var{length}">
41815 <property name="blocksize">@var{blocksize}</property>
41821 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
41822 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
41823 packets to write to addresses in such ranges.
41825 The formal DTD for memory map format is given below:
41828 <!-- ................................................... -->
41829 <!-- Memory Map XML DTD ................................ -->
41830 <!-- File: memory-map.dtd .............................. -->
41831 <!-- .................................... .............. -->
41832 <!-- memory-map.dtd -->
41833 <!-- memory-map: Root element with versioning -->
41834 <!ELEMENT memory-map (memory | property)>
41835 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
41836 <!ELEMENT memory (property)>
41837 <!-- memory: Specifies a memory region,
41838 and its type, or device. -->
41839 <!ATTLIST memory type CDATA #REQUIRED
41840 start CDATA #REQUIRED
41841 length CDATA #REQUIRED
41842 device CDATA #IMPLIED>
41843 <!-- property: Generic attribute tag -->
41844 <!ELEMENT property (#PCDATA | property)*>
41845 <!ATTLIST property name CDATA #REQUIRED>
41848 @node Thread List Format
41849 @section Thread List Format
41850 @cindex thread list format
41852 To efficiently update the list of threads and their attributes,
41853 @value{GDBN} issues the @samp{qXfer:threads:read} packet
41854 (@pxref{qXfer threads read}) and obtains the XML document with
41855 the following structure:
41858 <?xml version="1.0"?>
41860 <thread id="id" core="0">
41861 ... description ...
41866 Each @samp{thread} element must have the @samp{id} attribute that
41867 identifies the thread (@pxref{thread-id syntax}). The
41868 @samp{core} attribute, if present, specifies which processor core
41869 the thread was last executing on. The content of the of @samp{thread}
41870 element is interpreted as human-readable auxilliary information.
41872 @node Traceframe Info Format
41873 @section Traceframe Info Format
41874 @cindex traceframe info format
41876 To be able to know which objects in the inferior can be examined when
41877 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
41878 memory ranges, registers and trace state variables that have been
41879 collected in a traceframe.
41881 This list is obtained using the @samp{qXfer:traceframe-info:read}
41882 (@pxref{qXfer traceframe info read}) packet and is an XML document.
41884 @value{GDBN} must be linked with the Expat library to support XML
41885 traceframe info discovery. @xref{Expat}.
41887 The top-level structure of the document is shown below:
41890 <?xml version="1.0"?>
41891 <!DOCTYPE traceframe-info
41892 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
41893 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
41899 Each traceframe block can be either:
41904 A region of collected memory starting at @var{addr} and extending for
41905 @var{length} bytes from there:
41908 <memory start="@var{addr}" length="@var{length}"/>
41912 A block indicating trace state variable numbered @var{number} has been
41916 <tvar id="@var{number}"/>
41921 The formal DTD for the traceframe info format is given below:
41924 <!ELEMENT traceframe-info (memory | tvar)* >
41925 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
41927 <!ELEMENT memory EMPTY>
41928 <!ATTLIST memory start CDATA #REQUIRED
41929 length CDATA #REQUIRED>
41931 <!ATTLIST tvar id CDATA #REQUIRED>
41934 @node Branch Trace Format
41935 @section Branch Trace Format
41936 @cindex branch trace format
41938 In order to display the branch trace of an inferior thread,
41939 @value{GDBN} needs to obtain the list of branches. This list is
41940 represented as list of sequential code blocks that are connected via
41941 branches. The code in each block has been executed sequentially.
41943 This list is obtained using the @samp{qXfer:btrace:read}
41944 (@pxref{qXfer btrace read}) packet and is an XML document.
41946 @value{GDBN} must be linked with the Expat library to support XML
41947 traceframe info discovery. @xref{Expat}.
41949 The top-level structure of the document is shown below:
41952 <?xml version="1.0"?>
41954 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
41955 "http://sourceware.org/gdb/gdb-btrace.dtd">
41964 A block of sequentially executed instructions starting at @var{begin}
41965 and ending at @var{end}:
41968 <block begin="@var{begin}" end="@var{end}"/>
41973 The formal DTD for the branch trace format is given below:
41976 <!ELEMENT btrace (block)* >
41977 <!ATTLIST btrace version CDATA #FIXED "1.0">
41979 <!ELEMENT block EMPTY>
41980 <!ATTLIST block begin CDATA #REQUIRED
41981 end CDATA #REQUIRED>
41984 @include agentexpr.texi
41986 @node Target Descriptions
41987 @appendix Target Descriptions
41988 @cindex target descriptions
41990 One of the challenges of using @value{GDBN} to debug embedded systems
41991 is that there are so many minor variants of each processor
41992 architecture in use. It is common practice for vendors to start with
41993 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
41994 and then make changes to adapt it to a particular market niche. Some
41995 architectures have hundreds of variants, available from dozens of
41996 vendors. This leads to a number of problems:
42000 With so many different customized processors, it is difficult for
42001 the @value{GDBN} maintainers to keep up with the changes.
42003 Since individual variants may have short lifetimes or limited
42004 audiences, it may not be worthwhile to carry information about every
42005 variant in the @value{GDBN} source tree.
42007 When @value{GDBN} does support the architecture of the embedded system
42008 at hand, the task of finding the correct architecture name to give the
42009 @command{set architecture} command can be error-prone.
42012 To address these problems, the @value{GDBN} remote protocol allows a
42013 target system to not only identify itself to @value{GDBN}, but to
42014 actually describe its own features. This lets @value{GDBN} support
42015 processor variants it has never seen before --- to the extent that the
42016 descriptions are accurate, and that @value{GDBN} understands them.
42018 @value{GDBN} must be linked with the Expat library to support XML
42019 target descriptions. @xref{Expat}.
42022 * Retrieving Descriptions:: How descriptions are fetched from a target.
42023 * Target Description Format:: The contents of a target description.
42024 * Predefined Target Types:: Standard types available for target
42026 * Standard Target Features:: Features @value{GDBN} knows about.
42029 @node Retrieving Descriptions
42030 @section Retrieving Descriptions
42032 Target descriptions can be read from the target automatically, or
42033 specified by the user manually. The default behavior is to read the
42034 description from the target. @value{GDBN} retrieves it via the remote
42035 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
42036 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
42037 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
42038 XML document, of the form described in @ref{Target Description
42041 Alternatively, you can specify a file to read for the target description.
42042 If a file is set, the target will not be queried. The commands to
42043 specify a file are:
42046 @cindex set tdesc filename
42047 @item set tdesc filename @var{path}
42048 Read the target description from @var{path}.
42050 @cindex unset tdesc filename
42051 @item unset tdesc filename
42052 Do not read the XML target description from a file. @value{GDBN}
42053 will use the description supplied by the current target.
42055 @cindex show tdesc filename
42056 @item show tdesc filename
42057 Show the filename to read for a target description, if any.
42061 @node Target Description Format
42062 @section Target Description Format
42063 @cindex target descriptions, XML format
42065 A target description annex is an @uref{http://www.w3.org/XML/, XML}
42066 document which complies with the Document Type Definition provided in
42067 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
42068 means you can use generally available tools like @command{xmllint} to
42069 check that your feature descriptions are well-formed and valid.
42070 However, to help people unfamiliar with XML write descriptions for
42071 their targets, we also describe the grammar here.
42073 Target descriptions can identify the architecture of the remote target
42074 and (for some architectures) provide information about custom register
42075 sets. They can also identify the OS ABI of the remote target.
42076 @value{GDBN} can use this information to autoconfigure for your
42077 target, or to warn you if you connect to an unsupported target.
42079 Here is a simple target description:
42082 <target version="1.0">
42083 <architecture>i386:x86-64</architecture>
42088 This minimal description only says that the target uses
42089 the x86-64 architecture.
42091 A target description has the following overall form, with [ ] marking
42092 optional elements and @dots{} marking repeatable elements. The elements
42093 are explained further below.
42096 <?xml version="1.0"?>
42097 <!DOCTYPE target SYSTEM "gdb-target.dtd">
42098 <target version="1.0">
42099 @r{[}@var{architecture}@r{]}
42100 @r{[}@var{osabi}@r{]}
42101 @r{[}@var{compatible}@r{]}
42102 @r{[}@var{feature}@dots{}@r{]}
42107 The description is generally insensitive to whitespace and line
42108 breaks, under the usual common-sense rules. The XML version
42109 declaration and document type declaration can generally be omitted
42110 (@value{GDBN} does not require them), but specifying them may be
42111 useful for XML validation tools. The @samp{version} attribute for
42112 @samp{<target>} may also be omitted, but we recommend
42113 including it; if future versions of @value{GDBN} use an incompatible
42114 revision of @file{gdb-target.dtd}, they will detect and report
42115 the version mismatch.
42117 @subsection Inclusion
42118 @cindex target descriptions, inclusion
42121 @cindex <xi:include>
42124 It can sometimes be valuable to split a target description up into
42125 several different annexes, either for organizational purposes, or to
42126 share files between different possible target descriptions. You can
42127 divide a description into multiple files by replacing any element of
42128 the target description with an inclusion directive of the form:
42131 <xi:include href="@var{document}"/>
42135 When @value{GDBN} encounters an element of this form, it will retrieve
42136 the named XML @var{document}, and replace the inclusion directive with
42137 the contents of that document. If the current description was read
42138 using @samp{qXfer}, then so will be the included document;
42139 @var{document} will be interpreted as the name of an annex. If the
42140 current description was read from a file, @value{GDBN} will look for
42141 @var{document} as a file in the same directory where it found the
42142 original description.
42144 @subsection Architecture
42145 @cindex <architecture>
42147 An @samp{<architecture>} element has this form:
42150 <architecture>@var{arch}</architecture>
42153 @var{arch} is one of the architectures from the set accepted by
42154 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42157 @cindex @code{<osabi>}
42159 This optional field was introduced in @value{GDBN} version 7.0.
42160 Previous versions of @value{GDBN} ignore it.
42162 An @samp{<osabi>} element has this form:
42165 <osabi>@var{abi-name}</osabi>
42168 @var{abi-name} is an OS ABI name from the same selection accepted by
42169 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
42171 @subsection Compatible Architecture
42172 @cindex @code{<compatible>}
42174 This optional field was introduced in @value{GDBN} version 7.0.
42175 Previous versions of @value{GDBN} ignore it.
42177 A @samp{<compatible>} element has this form:
42180 <compatible>@var{arch}</compatible>
42183 @var{arch} is one of the architectures from the set accepted by
42184 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
42186 A @samp{<compatible>} element is used to specify that the target
42187 is able to run binaries in some other than the main target architecture
42188 given by the @samp{<architecture>} element. For example, on the
42189 Cell Broadband Engine, the main architecture is @code{powerpc:common}
42190 or @code{powerpc:common64}, but the system is able to run binaries
42191 in the @code{spu} architecture as well. The way to describe this
42192 capability with @samp{<compatible>} is as follows:
42195 <architecture>powerpc:common</architecture>
42196 <compatible>spu</compatible>
42199 @subsection Features
42202 Each @samp{<feature>} describes some logical portion of the target
42203 system. Features are currently used to describe available CPU
42204 registers and the types of their contents. A @samp{<feature>} element
42208 <feature name="@var{name}">
42209 @r{[}@var{type}@dots{}@r{]}
42215 Each feature's name should be unique within the description. The name
42216 of a feature does not matter unless @value{GDBN} has some special
42217 knowledge of the contents of that feature; if it does, the feature
42218 should have its standard name. @xref{Standard Target Features}.
42222 Any register's value is a collection of bits which @value{GDBN} must
42223 interpret. The default interpretation is a two's complement integer,
42224 but other types can be requested by name in the register description.
42225 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
42226 Target Types}), and the description can define additional composite types.
42228 Each type element must have an @samp{id} attribute, which gives
42229 a unique (within the containing @samp{<feature>}) name to the type.
42230 Types must be defined before they are used.
42233 Some targets offer vector registers, which can be treated as arrays
42234 of scalar elements. These types are written as @samp{<vector>} elements,
42235 specifying the array element type, @var{type}, and the number of elements,
42239 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
42243 If a register's value is usefully viewed in multiple ways, define it
42244 with a union type containing the useful representations. The
42245 @samp{<union>} element contains one or more @samp{<field>} elements,
42246 each of which has a @var{name} and a @var{type}:
42249 <union id="@var{id}">
42250 <field name="@var{name}" type="@var{type}"/>
42256 If a register's value is composed from several separate values, define
42257 it with a structure type. There are two forms of the @samp{<struct>}
42258 element; a @samp{<struct>} element must either contain only bitfields
42259 or contain no bitfields. If the structure contains only bitfields,
42260 its total size in bytes must be specified, each bitfield must have an
42261 explicit start and end, and bitfields are automatically assigned an
42262 integer type. The field's @var{start} should be less than or
42263 equal to its @var{end}, and zero represents the least significant bit.
42266 <struct id="@var{id}" size="@var{size}">
42267 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42272 If the structure contains no bitfields, then each field has an
42273 explicit type, and no implicit padding is added.
42276 <struct id="@var{id}">
42277 <field name="@var{name}" type="@var{type}"/>
42283 If a register's value is a series of single-bit flags, define it with
42284 a flags type. The @samp{<flags>} element has an explicit @var{size}
42285 and contains one or more @samp{<field>} elements. Each field has a
42286 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
42290 <flags id="@var{id}" size="@var{size}">
42291 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
42296 @subsection Registers
42299 Each register is represented as an element with this form:
42302 <reg name="@var{name}"
42303 bitsize="@var{size}"
42304 @r{[}regnum="@var{num}"@r{]}
42305 @r{[}save-restore="@var{save-restore}"@r{]}
42306 @r{[}type="@var{type}"@r{]}
42307 @r{[}group="@var{group}"@r{]}/>
42311 The components are as follows:
42316 The register's name; it must be unique within the target description.
42319 The register's size, in bits.
42322 The register's number. If omitted, a register's number is one greater
42323 than that of the previous register (either in the current feature or in
42324 a preceding feature); the first register in the target description
42325 defaults to zero. This register number is used to read or write
42326 the register; e.g.@: it is used in the remote @code{p} and @code{P}
42327 packets, and registers appear in the @code{g} and @code{G} packets
42328 in order of increasing register number.
42331 Whether the register should be preserved across inferior function
42332 calls; this must be either @code{yes} or @code{no}. The default is
42333 @code{yes}, which is appropriate for most registers except for
42334 some system control registers; this is not related to the target's
42338 The type of the register. @var{type} may be a predefined type, a type
42339 defined in the current feature, or one of the special types @code{int}
42340 and @code{float}. @code{int} is an integer type of the correct size
42341 for @var{bitsize}, and @code{float} is a floating point type (in the
42342 architecture's normal floating point format) of the correct size for
42343 @var{bitsize}. The default is @code{int}.
42346 The register group to which this register belongs. @var{group} must
42347 be either @code{general}, @code{float}, or @code{vector}. If no
42348 @var{group} is specified, @value{GDBN} will not display the register
42349 in @code{info registers}.
42353 @node Predefined Target Types
42354 @section Predefined Target Types
42355 @cindex target descriptions, predefined types
42357 Type definitions in the self-description can build up composite types
42358 from basic building blocks, but can not define fundamental types. Instead,
42359 standard identifiers are provided by @value{GDBN} for the fundamental
42360 types. The currently supported types are:
42369 Signed integer types holding the specified number of bits.
42376 Unsigned integer types holding the specified number of bits.
42380 Pointers to unspecified code and data. The program counter and
42381 any dedicated return address register may be marked as code
42382 pointers; printing a code pointer converts it into a symbolic
42383 address. The stack pointer and any dedicated address registers
42384 may be marked as data pointers.
42387 Single precision IEEE floating point.
42390 Double precision IEEE floating point.
42393 The 12-byte extended precision format used by ARM FPA registers.
42396 The 10-byte extended precision format used by x87 registers.
42399 32bit @sc{eflags} register used by x86.
42402 32bit @sc{mxcsr} register used by x86.
42406 @node Standard Target Features
42407 @section Standard Target Features
42408 @cindex target descriptions, standard features
42410 A target description must contain either no registers or all the
42411 target's registers. If the description contains no registers, then
42412 @value{GDBN} will assume a default register layout, selected based on
42413 the architecture. If the description contains any registers, the
42414 default layout will not be used; the standard registers must be
42415 described in the target description, in such a way that @value{GDBN}
42416 can recognize them.
42418 This is accomplished by giving specific names to feature elements
42419 which contain standard registers. @value{GDBN} will look for features
42420 with those names and verify that they contain the expected registers;
42421 if any known feature is missing required registers, or if any required
42422 feature is missing, @value{GDBN} will reject the target
42423 description. You can add additional registers to any of the
42424 standard features --- @value{GDBN} will display them just as if
42425 they were added to an unrecognized feature.
42427 This section lists the known features and their expected contents.
42428 Sample XML documents for these features are included in the
42429 @value{GDBN} source tree, in the directory @file{gdb/features}.
42431 Names recognized by @value{GDBN} should include the name of the
42432 company or organization which selected the name, and the overall
42433 architecture to which the feature applies; so e.g.@: the feature
42434 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
42436 The names of registers are not case sensitive for the purpose
42437 of recognizing standard features, but @value{GDBN} will only display
42438 registers using the capitalization used in the description.
42441 * AArch64 Features::
42446 * Nios II Features::
42447 * PowerPC Features::
42452 @node AArch64 Features
42453 @subsection AArch64 Features
42454 @cindex target descriptions, AArch64 features
42456 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
42457 targets. It should contain registers @samp{x0} through @samp{x30},
42458 @samp{sp}, @samp{pc}, and @samp{cpsr}.
42460 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
42461 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
42465 @subsection ARM Features
42466 @cindex target descriptions, ARM features
42468 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
42470 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
42471 @samp{lr}, @samp{pc}, and @samp{cpsr}.
42473 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
42474 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
42475 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
42478 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
42479 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
42481 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
42482 it should contain at least registers @samp{wR0} through @samp{wR15} and
42483 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
42484 @samp{wCSSF}, and @samp{wCASF} registers are optional.
42486 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
42487 should contain at least registers @samp{d0} through @samp{d15}. If
42488 they are present, @samp{d16} through @samp{d31} should also be included.
42489 @value{GDBN} will synthesize the single-precision registers from
42490 halves of the double-precision registers.
42492 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
42493 need to contain registers; it instructs @value{GDBN} to display the
42494 VFP double-precision registers as vectors and to synthesize the
42495 quad-precision registers from pairs of double-precision registers.
42496 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
42497 be present and include 32 double-precision registers.
42499 @node i386 Features
42500 @subsection i386 Features
42501 @cindex target descriptions, i386 features
42503 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
42504 targets. It should describe the following registers:
42508 @samp{eax} through @samp{edi} plus @samp{eip} for i386
42510 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
42512 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
42513 @samp{fs}, @samp{gs}
42515 @samp{st0} through @samp{st7}
42517 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
42518 @samp{foseg}, @samp{fooff} and @samp{fop}
42521 The register sets may be different, depending on the target.
42523 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
42524 describe registers:
42528 @samp{xmm0} through @samp{xmm7} for i386
42530 @samp{xmm0} through @samp{xmm15} for amd64
42535 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
42536 @samp{org.gnu.gdb.i386.sse} feature. It should
42537 describe the upper 128 bits of @sc{ymm} registers:
42541 @samp{ymm0h} through @samp{ymm7h} for i386
42543 @samp{ymm0h} through @samp{ymm15h} for amd64
42546 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
42547 describe a single register, @samp{orig_eax}.
42549 @node MIPS Features
42550 @subsection @acronym{MIPS} Features
42551 @cindex target descriptions, @acronym{MIPS} features
42553 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
42554 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
42555 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
42558 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
42559 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
42560 registers. They may be 32-bit or 64-bit depending on the target.
42562 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
42563 it may be optional in a future version of @value{GDBN}. It should
42564 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
42565 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
42567 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
42568 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
42569 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
42570 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
42572 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
42573 contain a single register, @samp{restart}, which is used by the
42574 Linux kernel to control restartable syscalls.
42576 @node M68K Features
42577 @subsection M68K Features
42578 @cindex target descriptions, M68K features
42581 @item @samp{org.gnu.gdb.m68k.core}
42582 @itemx @samp{org.gnu.gdb.coldfire.core}
42583 @itemx @samp{org.gnu.gdb.fido.core}
42584 One of those features must be always present.
42585 The feature that is present determines which flavor of m68k is
42586 used. The feature that is present should contain registers
42587 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
42588 @samp{sp}, @samp{ps} and @samp{pc}.
42590 @item @samp{org.gnu.gdb.coldfire.fp}
42591 This feature is optional. If present, it should contain registers
42592 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
42596 @node Nios II Features
42597 @subsection Nios II Features
42598 @cindex target descriptions, Nios II features
42600 The @samp{org.gnu.gdb.nios2.cpu} feature is required for Nios II
42601 targets. It should contain the 32 core registers (@samp{zero},
42602 @samp{at}, @samp{r2} through @samp{r23}, @samp{et} through @samp{ra}),
42603 @samp{pc}, and the 16 control registers (@samp{status} through
42606 @node PowerPC Features
42607 @subsection PowerPC Features
42608 @cindex target descriptions, PowerPC features
42610 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
42611 targets. It should contain registers @samp{r0} through @samp{r31},
42612 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
42613 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
42615 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
42616 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
42618 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
42619 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
42622 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
42623 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
42624 will combine these registers with the floating point registers
42625 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
42626 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
42627 through @samp{vs63}, the set of vector registers for POWER7.
42629 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
42630 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
42631 @samp{spefscr}. SPE targets should provide 32-bit registers in
42632 @samp{org.gnu.gdb.power.core} and provide the upper halves in
42633 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
42634 these to present registers @samp{ev0} through @samp{ev31} to the
42637 @node TIC6x Features
42638 @subsection TMS320C6x Features
42639 @cindex target descriptions, TIC6x features
42640 @cindex target descriptions, TMS320C6x features
42641 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
42642 targets. It should contain registers @samp{A0} through @samp{A15},
42643 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
42645 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
42646 contain registers @samp{A16} through @samp{A31} and @samp{B16}
42647 through @samp{B31}.
42649 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
42650 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
42652 @node Operating System Information
42653 @appendix Operating System Information
42654 @cindex operating system information
42660 Users of @value{GDBN} often wish to obtain information about the state of
42661 the operating system running on the target---for example the list of
42662 processes, or the list of open files. This section describes the
42663 mechanism that makes it possible. This mechanism is similar to the
42664 target features mechanism (@pxref{Target Descriptions}), but focuses
42665 on a different aspect of target.
42667 Operating system information is retrived from the target via the
42668 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
42669 read}). The object name in the request should be @samp{osdata}, and
42670 the @var{annex} identifies the data to be fetched.
42673 @appendixsection Process list
42674 @cindex operating system information, process list
42676 When requesting the process list, the @var{annex} field in the
42677 @samp{qXfer} request should be @samp{processes}. The returned data is
42678 an XML document. The formal syntax of this document is defined in
42679 @file{gdb/features/osdata.dtd}.
42681 An example document is:
42684 <?xml version="1.0"?>
42685 <!DOCTYPE target SYSTEM "osdata.dtd">
42686 <osdata type="processes">
42688 <column name="pid">1</column>
42689 <column name="user">root</column>
42690 <column name="command">/sbin/init</column>
42691 <column name="cores">1,2,3</column>
42696 Each item should include a column whose name is @samp{pid}. The value
42697 of that column should identify the process on the target. The
42698 @samp{user} and @samp{command} columns are optional, and will be
42699 displayed by @value{GDBN}. The @samp{cores} column, if present,
42700 should contain a comma-separated list of cores that this process
42701 is running on. Target may provide additional columns,
42702 which @value{GDBN} currently ignores.
42704 @node Trace File Format
42705 @appendix Trace File Format
42706 @cindex trace file format
42708 The trace file comes in three parts: a header, a textual description
42709 section, and a trace frame section with binary data.
42711 The header has the form @code{\x7fTRACE0\n}. The first byte is
42712 @code{0x7f} so as to indicate that the file contains binary data,
42713 while the @code{0} is a version number that may have different values
42716 The description section consists of multiple lines of @sc{ascii} text
42717 separated by newline characters (@code{0xa}). The lines may include a
42718 variety of optional descriptive or context-setting information, such
42719 as tracepoint definitions or register set size. @value{GDBN} will
42720 ignore any line that it does not recognize. An empty line marks the end
42723 @c FIXME add some specific types of data
42725 The trace frame section consists of a number of consecutive frames.
42726 Each frame begins with a two-byte tracepoint number, followed by a
42727 four-byte size giving the amount of data in the frame. The data in
42728 the frame consists of a number of blocks, each introduced by a
42729 character indicating its type (at least register, memory, and trace
42730 state variable). The data in this section is raw binary, not a
42731 hexadecimal or other encoding; its endianness matches the target's
42734 @c FIXME bi-arch may require endianness/arch info in description section
42737 @item R @var{bytes}
42738 Register block. The number and ordering of bytes matches that of a
42739 @code{g} packet in the remote protocol. Note that these are the
42740 actual bytes, in target order and @value{GDBN} register order, not a
42741 hexadecimal encoding.
42743 @item M @var{address} @var{length} @var{bytes}...
42744 Memory block. This is a contiguous block of memory, at the 8-byte
42745 address @var{address}, with a 2-byte length @var{length}, followed by
42746 @var{length} bytes.
42748 @item V @var{number} @var{value}
42749 Trace state variable block. This records the 8-byte signed value
42750 @var{value} of trace state variable numbered @var{number}.
42754 Future enhancements of the trace file format may include additional types
42757 @node Index Section Format
42758 @appendix @code{.gdb_index} section format
42759 @cindex .gdb_index section format
42760 @cindex index section format
42762 This section documents the index section that is created by @code{save
42763 gdb-index} (@pxref{Index Files}). The index section is
42764 DWARF-specific; some knowledge of DWARF is assumed in this
42767 The mapped index file format is designed to be directly
42768 @code{mmap}able on any architecture. In most cases, a datum is
42769 represented using a little-endian 32-bit integer value, called an
42770 @code{offset_type}. Big endian machines must byte-swap the values
42771 before using them. Exceptions to this rule are noted. The data is
42772 laid out such that alignment is always respected.
42774 A mapped index consists of several areas, laid out in order.
42778 The file header. This is a sequence of values, of @code{offset_type}
42779 unless otherwise noted:
42783 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
42784 Version 4 uses a different hashing function from versions 5 and 6.
42785 Version 6 includes symbols for inlined functions, whereas versions 4
42786 and 5 do not. Version 7 adds attributes to the CU indices in the
42787 symbol table. Version 8 specifies that symbols from DWARF type units
42788 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
42789 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
42791 @value{GDBN} will only read version 4, 5, or 6 indices
42792 by specifying @code{set use-deprecated-index-sections on}.
42793 GDB has a workaround for potentially broken version 7 indices so it is
42794 currently not flagged as deprecated.
42797 The offset, from the start of the file, of the CU list.
42800 The offset, from the start of the file, of the types CU list. Note
42801 that this area can be empty, in which case this offset will be equal
42802 to the next offset.
42805 The offset, from the start of the file, of the address area.
42808 The offset, from the start of the file, of the symbol table.
42811 The offset, from the start of the file, of the constant pool.
42815 The CU list. This is a sequence of pairs of 64-bit little-endian
42816 values, sorted by the CU offset. The first element in each pair is
42817 the offset of a CU in the @code{.debug_info} section. The second
42818 element in each pair is the length of that CU. References to a CU
42819 elsewhere in the map are done using a CU index, which is just the
42820 0-based index into this table. Note that if there are type CUs, then
42821 conceptually CUs and type CUs form a single list for the purposes of
42825 The types CU list. This is a sequence of triplets of 64-bit
42826 little-endian values. In a triplet, the first value is the CU offset,
42827 the second value is the type offset in the CU, and the third value is
42828 the type signature. The types CU list is not sorted.
42831 The address area. The address area consists of a sequence of address
42832 entries. Each address entry has three elements:
42836 The low address. This is a 64-bit little-endian value.
42839 The high address. This is a 64-bit little-endian value. Like
42840 @code{DW_AT_high_pc}, the value is one byte beyond the end.
42843 The CU index. This is an @code{offset_type} value.
42847 The symbol table. This is an open-addressed hash table. The size of
42848 the hash table is always a power of 2.
42850 Each slot in the hash table consists of a pair of @code{offset_type}
42851 values. The first value is the offset of the symbol's name in the
42852 constant pool. The second value is the offset of the CU vector in the
42855 If both values are 0, then this slot in the hash table is empty. This
42856 is ok because while 0 is a valid constant pool index, it cannot be a
42857 valid index for both a string and a CU vector.
42859 The hash value for a table entry is computed by applying an
42860 iterative hash function to the symbol's name. Starting with an
42861 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
42862 the string is incorporated into the hash using the formula depending on the
42867 The formula is @code{r = r * 67 + c - 113}.
42869 @item Versions 5 to 7
42870 The formula is @code{r = r * 67 + tolower (c) - 113}.
42873 The terminating @samp{\0} is not incorporated into the hash.
42875 The step size used in the hash table is computed via
42876 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
42877 value, and @samp{size} is the size of the hash table. The step size
42878 is used to find the next candidate slot when handling a hash
42881 The names of C@t{++} symbols in the hash table are canonicalized. We
42882 don't currently have a simple description of the canonicalization
42883 algorithm; if you intend to create new index sections, you must read
42887 The constant pool. This is simply a bunch of bytes. It is organized
42888 so that alignment is correct: CU vectors are stored first, followed by
42891 A CU vector in the constant pool is a sequence of @code{offset_type}
42892 values. The first value is the number of CU indices in the vector.
42893 Each subsequent value is the index and symbol attributes of a CU in
42894 the CU list. This element in the hash table is used to indicate which
42895 CUs define the symbol and how the symbol is used.
42896 See below for the format of each CU index+attributes entry.
42898 A string in the constant pool is zero-terminated.
42901 Attributes were added to CU index values in @code{.gdb_index} version 7.
42902 If a symbol has multiple uses within a CU then there is one
42903 CU index+attributes value for each use.
42905 The format of each CU index+attributes entry is as follows
42911 This is the index of the CU in the CU list.
42913 These bits are reserved for future purposes and must be zero.
42915 The kind of the symbol in the CU.
42919 This value is reserved and should not be used.
42920 By reserving zero the full @code{offset_type} value is backwards compatible
42921 with previous versions of the index.
42923 The symbol is a type.
42925 The symbol is a variable or an enum value.
42927 The symbol is a function.
42929 Any other kind of symbol.
42931 These values are reserved.
42935 This bit is zero if the value is global and one if it is static.
42937 The determination of whether a symbol is global or static is complicated.
42938 The authorative reference is the file @file{dwarf2read.c} in
42939 @value{GDBN} sources.
42943 This pseudo-code describes the computation of a symbol's kind and
42944 global/static attributes in the index.
42947 is_external = get_attribute (die, DW_AT_external);
42948 language = get_attribute (cu_die, DW_AT_language);
42951 case DW_TAG_typedef:
42952 case DW_TAG_base_type:
42953 case DW_TAG_subrange_type:
42957 case DW_TAG_enumerator:
42959 is_static = (language != CPLUS && language != JAVA);
42961 case DW_TAG_subprogram:
42963 is_static = ! (is_external || language == ADA);
42965 case DW_TAG_constant:
42967 is_static = ! is_external;
42969 case DW_TAG_variable:
42971 is_static = ! is_external;
42973 case DW_TAG_namespace:
42977 case DW_TAG_class_type:
42978 case DW_TAG_interface_type:
42979 case DW_TAG_structure_type:
42980 case DW_TAG_union_type:
42981 case DW_TAG_enumeration_type:
42983 is_static = (language != CPLUS && language != JAVA);
42991 @appendix Manual pages
42995 * gdb man:: The GNU Debugger man page
42996 * gdbserver man:: Remote Server for the GNU Debugger man page
42997 * gcore man:: Generate a core file of a running program
42998 * gdbinit man:: gdbinit scripts
43004 @c man title gdb The GNU Debugger
43006 @c man begin SYNOPSIS gdb
43007 gdb [@option{-help}] [@option{-nh}] [@option{-nx}] [@option{-q}]
43008 [@option{-batch}] [@option{-cd=}@var{dir}] [@option{-f}]
43009 [@option{-b}@w{ }@var{bps}]
43010 [@option{-tty=}@var{dev}] [@option{-s} @var{symfile}]
43011 [@option{-e}@w{ }@var{prog}] [@option{-se}@w{ }@var{prog}]
43012 [@option{-c}@w{ }@var{core}] [@option{-p}@w{ }@var{procID}]
43013 [@option{-x}@w{ }@var{cmds}] [@option{-d}@w{ }@var{dir}]
43014 [@var{prog}|@var{prog} @var{procID}|@var{prog} @var{core}]
43017 @c man begin DESCRIPTION gdb
43018 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
43019 going on ``inside'' another program while it executes -- or what another
43020 program was doing at the moment it crashed.
43022 @value{GDBN} can do four main kinds of things (plus other things in support of
43023 these) to help you catch bugs in the act:
43027 Start your program, specifying anything that might affect its behavior.
43030 Make your program stop on specified conditions.
43033 Examine what has happened, when your program has stopped.
43036 Change things in your program, so you can experiment with correcting the
43037 effects of one bug and go on to learn about another.
43040 You can use @value{GDBN} to debug programs written in C, C@t{++}, Fortran and
43043 @value{GDBN} is invoked with the shell command @code{gdb}. Once started, it reads
43044 commands from the terminal until you tell it to exit with the @value{GDBN}
43045 command @code{quit}. You can get online help from @value{GDBN} itself
43046 by using the command @code{help}.
43048 You can run @code{gdb} with no arguments or options; but the most
43049 usual way to start @value{GDBN} is with one argument or two, specifying an
43050 executable program as the argument:
43056 You can also start with both an executable program and a core file specified:
43062 You can, instead, specify a process ID as a second argument, if you want
43063 to debug a running process:
43071 would attach @value{GDBN} to process @code{1234} (unless you also have a file
43072 named @file{1234}; @value{GDBN} does check for a core file first).
43073 With option @option{-p} you can omit the @var{program} filename.
43075 Here are some of the most frequently needed @value{GDBN} commands:
43077 @c pod2man highlights the right hand side of the @item lines.
43079 @item break [@var{file}:]@var{functiop}
43080 Set a breakpoint at @var{function} (in @var{file}).
43082 @item run [@var{arglist}]
43083 Start your program (with @var{arglist}, if specified).
43086 Backtrace: display the program stack.
43088 @item print @var{expr}
43089 Display the value of an expression.
43092 Continue running your program (after stopping, e.g. at a breakpoint).
43095 Execute next program line (after stopping); step @emph{over} any
43096 function calls in the line.
43098 @item edit [@var{file}:]@var{function}
43099 look at the program line where it is presently stopped.
43101 @item list [@var{file}:]@var{function}
43102 type the text of the program in the vicinity of where it is presently stopped.
43105 Execute next program line (after stopping); step @emph{into} any
43106 function calls in the line.
43108 @item help [@var{name}]
43109 Show information about @value{GDBN} command @var{name}, or general information
43110 about using @value{GDBN}.
43113 Exit from @value{GDBN}.
43117 For full details on @value{GDBN},
43118 see @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43119 by Richard M. Stallman and Roland H. Pesch. The same text is available online
43120 as the @code{gdb} entry in the @code{info} program.
43124 @c man begin OPTIONS gdb
43125 Any arguments other than options specify an executable
43126 file and core file (or process ID); that is, the first argument
43127 encountered with no
43128 associated option flag is equivalent to a @option{-se} option, and the second,
43129 if any, is equivalent to a @option{-c} option if it's the name of a file.
43131 both long and short forms; both are shown here. The long forms are also
43132 recognized if you truncate them, so long as enough of the option is
43133 present to be unambiguous. (If you prefer, you can flag option
43134 arguments with @option{+} rather than @option{-}, though we illustrate the
43135 more usual convention.)
43137 All the options and command line arguments you give are processed
43138 in sequential order. The order makes a difference when the @option{-x}
43144 List all options, with brief explanations.
43146 @item -symbols=@var{file}
43147 @itemx -s @var{file}
43148 Read symbol table from file @var{file}.
43151 Enable writing into executable and core files.
43153 @item -exec=@var{file}
43154 @itemx -e @var{file}
43155 Use file @var{file} as the executable file to execute when
43156 appropriate, and for examining pure data in conjunction with a core
43159 @item -se=@var{file}
43160 Read symbol table from file @var{file} and use it as the executable
43163 @item -core=@var{file}
43164 @itemx -c @var{file}
43165 Use file @var{file} as a core dump to examine.
43167 @item -command=@var{file}
43168 @itemx -x @var{file}
43169 Execute @value{GDBN} commands from file @var{file}.
43171 @item -ex @var{command}
43172 Execute given @value{GDBN} @var{command}.
43174 @item -directory=@var{directory}
43175 @itemx -d @var{directory}
43176 Add @var{directory} to the path to search for source files.
43179 Do not execute commands from @file{~/.gdbinit}.
43183 Do not execute commands from any @file{.gdbinit} initialization files.
43187 ``Quiet''. Do not print the introductory and copyright messages. These
43188 messages are also suppressed in batch mode.
43191 Run in batch mode. Exit with status @code{0} after processing all the command
43192 files specified with @option{-x} (and @file{.gdbinit}, if not inhibited).
43193 Exit with nonzero status if an error occurs in executing the @value{GDBN}
43194 commands in the command files.
43196 Batch mode may be useful for running @value{GDBN} as a filter, for example to
43197 download and run a program on another computer; in order to make this
43198 more useful, the message
43201 Program exited normally.
43205 (which is ordinarily issued whenever a program running under @value{GDBN} control
43206 terminates) is not issued when running in batch mode.
43208 @item -cd=@var{directory}
43209 Run @value{GDBN} using @var{directory} as its working directory,
43210 instead of the current directory.
43214 Emacs sets this option when it runs @value{GDBN} as a subprocess. It tells
43215 @value{GDBN} to output the full file name and line number in a standard,
43216 recognizable fashion each time a stack frame is displayed (which
43217 includes each time the program stops). This recognizable format looks
43218 like two @samp{\032} characters, followed by the file name, line number
43219 and character position separated by colons, and a newline. The
43220 Emacs-to-@value{GDBN} interface program uses the two @samp{\032}
43221 characters as a signal to display the source code for the frame.
43224 Set the line speed (baud rate or bits per second) of any serial
43225 interface used by @value{GDBN} for remote debugging.
43227 @item -tty=@var{device}
43228 Run using @var{device} for your program's standard input and output.
43232 @c man begin SEEALSO gdb
43234 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43235 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43236 documentation are properly installed at your site, the command
43243 should give you access to the complete manual.
43245 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43246 Richard M. Stallman and Roland H. Pesch, July 1991.
43250 @node gdbserver man
43251 @heading gdbserver man
43253 @c man title gdbserver Remote Server for the GNU Debugger
43255 @c man begin SYNOPSIS gdbserver
43256 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43258 gdbserver --attach @var{comm} @var{pid}
43260 gdbserver --multi @var{comm}
43264 @c man begin DESCRIPTION gdbserver
43265 @command{gdbserver} is a program that allows you to run @value{GDBN} on a different machine
43266 than the one which is running the program being debugged.
43269 @subheading Usage (server (target) side)
43272 Usage (server (target) side):
43275 First, you need to have a copy of the program you want to debug put onto
43276 the target system. The program can be stripped to save space if needed, as
43277 @command{gdbserver} doesn't care about symbols. All symbol handling is taken care of by
43278 the @value{GDBN} running on the host system.
43280 To use the server, you log on to the target system, and run the @command{gdbserver}
43281 program. You must tell it (a) how to communicate with @value{GDBN}, (b) the name of
43282 your program, and (c) its arguments. The general syntax is:
43285 target> gdbserver @var{comm} @var{program} [@var{args} ...]
43288 For example, using a serial port, you might say:
43292 @c @file would wrap it as F</dev/com1>.
43293 target> gdbserver /dev/com1 emacs foo.txt
43296 target> gdbserver @file{/dev/com1} emacs foo.txt
43300 This tells @command{gdbserver} to debug emacs with an argument of foo.txt, and
43301 to communicate with @value{GDBN} via @file{/dev/com1}. @command{gdbserver} now
43302 waits patiently for the host @value{GDBN} to communicate with it.
43304 To use a TCP connection, you could say:
43307 target> gdbserver host:2345 emacs foo.txt
43310 This says pretty much the same thing as the last example, except that we are
43311 going to communicate with the @code{host} @value{GDBN} via TCP. The @code{host:2345} argument means
43312 that we are expecting to see a TCP connection from @code{host} to local TCP port
43313 2345. (Currently, the @code{host} part is ignored.) You can choose any number you
43314 want for the port number as long as it does not conflict with any existing TCP
43315 ports on the target system. This same port number must be used in the host
43316 @value{GDBN}s @code{target remote} command, which will be described shortly. Note that if
43317 you chose a port number that conflicts with another service, @command{gdbserver} will
43318 print an error message and exit.
43320 @command{gdbserver} can also attach to running programs.
43321 This is accomplished via the @option{--attach} argument. The syntax is:
43324 target> gdbserver --attach @var{comm} @var{pid}
43327 @var{pid} is the process ID of a currently running process. It isn't
43328 necessary to point @command{gdbserver} at a binary for the running process.
43330 To start @code{gdbserver} without supplying an initial command to run
43331 or process ID to attach, use the @option{--multi} command line option.
43332 In such case you should connect using @kbd{target extended-remote} to start
43333 the program you want to debug.
43336 target> gdbserver --multi @var{comm}
43340 @subheading Usage (host side)
43346 You need an unstripped copy of the target program on your host system, since
43347 @value{GDBN} needs to examine it's symbol tables and such. Start up @value{GDBN} as you normally
43348 would, with the target program as the first argument. (You may need to use the
43349 @option{--baud} option if the serial line is running at anything except 9600 baud.)
43350 That is @code{gdb TARGET-PROG}, or @code{gdb --baud BAUD TARGET-PROG}. After that, the only
43351 new command you need to know about is @code{target remote}
43352 (or @code{target extended-remote}). Its argument is either
43353 a device name (usually a serial device, like @file{/dev/ttyb}), or a @code{HOST:PORT}
43354 descriptor. For example:
43358 @c @file would wrap it as F</dev/ttyb>.
43359 (gdb) target remote /dev/ttyb
43362 (gdb) target remote @file{/dev/ttyb}
43367 communicates with the server via serial line @file{/dev/ttyb}, and:
43370 (gdb) target remote the-target:2345
43374 communicates via a TCP connection to port 2345 on host `the-target', where
43375 you previously started up @command{gdbserver} with the same port number. Note that for
43376 TCP connections, you must start up @command{gdbserver} prior to using the `target remote'
43377 command, otherwise you may get an error that looks something like
43378 `Connection refused'.
43380 @command{gdbserver} can also debug multiple inferiors at once,
43383 the @value{GDBN} manual in node @code{Inferiors and Programs}
43384 -- shell command @code{info -f gdb -n 'Inferiors and Programs'}.
43387 @ref{Inferiors and Programs}.
43389 In such case use the @code{extended-remote} @value{GDBN} command variant:
43392 (gdb) target extended-remote the-target:2345
43395 The @command{gdbserver} option @option{--multi} may or may not be used in such
43399 @c man begin OPTIONS gdbserver
43400 There are three different modes for invoking @command{gdbserver}:
43405 Debug a specific program specified by its program name:
43408 gdbserver @var{comm} @var{prog} [@var{args}@dots{}]
43411 The @var{comm} parameter specifies how should the server communicate
43412 with @value{GDBN}; it is either a device name (to use a serial line),
43413 a TCP port number (@code{:1234}), or @code{-} or @code{stdio} to use
43414 stdin/stdout of @code{gdbserver}. Specify the name of the program to
43415 debug in @var{prog}. Any remaining arguments will be passed to the
43416 program verbatim. When the program exits, @value{GDBN} will close the
43417 connection, and @code{gdbserver} will exit.
43420 Debug a specific program by specifying the process ID of a running
43424 gdbserver --attach @var{comm} @var{pid}
43427 The @var{comm} parameter is as described above. Supply the process ID
43428 of a running program in @var{pid}; @value{GDBN} will do everything
43429 else. Like with the previous mode, when the process @var{pid} exits,
43430 @value{GDBN} will close the connection, and @code{gdbserver} will exit.
43433 Multi-process mode -- debug more than one program/process:
43436 gdbserver --multi @var{comm}
43439 In this mode, @value{GDBN} can instruct @command{gdbserver} which
43440 command(s) to run. Unlike the other 2 modes, @value{GDBN} will not
43441 close the connection when a process being debugged exits, so you can
43442 debug several processes in the same session.
43445 In each of the modes you may specify these options:
43450 List all options, with brief explanations.
43453 This option causes @command{gdbserver} to print its version number and exit.
43456 @command{gdbserver} will attach to a running program. The syntax is:
43459 target> gdbserver --attach @var{comm} @var{pid}
43462 @var{pid} is the process ID of a currently running process. It isn't
43463 necessary to point @command{gdbserver} at a binary for the running process.
43466 To start @code{gdbserver} without supplying an initial command to run
43467 or process ID to attach, use this command line option.
43468 Then you can connect using @kbd{target extended-remote} and start
43469 the program you want to debug. The syntax is:
43472 target> gdbserver --multi @var{comm}
43476 Instruct @code{gdbserver} to display extra status information about the debugging
43478 This option is intended for @code{gdbserver} development and for bug reports to
43481 @item --remote-debug
43482 Instruct @code{gdbserver} to display remote protocol debug output.
43483 This option is intended for @code{gdbserver} development and for bug reports to
43487 Specify a wrapper to launch programs
43488 for debugging. The option should be followed by the name of the
43489 wrapper, then any command-line arguments to pass to the wrapper, then
43490 @kbd{--} indicating the end of the wrapper arguments.
43493 By default, @command{gdbserver} keeps the listening TCP port open, so that
43494 additional connections are possible. However, if you start @code{gdbserver}
43495 with the @option{--once} option, it will stop listening for any further
43496 connection attempts after connecting to the first @value{GDBN} session.
43498 @c --disable-packet is not documented for users.
43500 @c --disable-randomization and --no-disable-randomization are superseded by
43501 @c QDisableRandomization.
43506 @c man begin SEEALSO gdbserver
43508 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43509 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43510 documentation are properly installed at your site, the command
43516 should give you access to the complete manual.
43518 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43519 Richard M. Stallman and Roland H. Pesch, July 1991.
43526 @c man title gcore Generate a core file of a running program
43529 @c man begin SYNOPSIS gcore
43530 gcore [-o @var{filename}] @var{pid}
43534 @c man begin DESCRIPTION gcore
43535 Generate a core dump of a running program with process ID @var{pid}.
43536 Produced file is equivalent to a kernel produced core file as if the process
43537 crashed (and if @kbd{ulimit -c} were used to set up an appropriate core dump
43538 limit). Unlike after a crash, after @command{gcore} the program remains
43539 running without any change.
43542 @c man begin OPTIONS gcore
43544 @item -o @var{filename}
43545 The optional argument
43546 @var{filename} specifies the file name where to put the core dump.
43547 If not specified, the file name defaults to @file{core.@var{pid}},
43548 where @var{pid} is the running program process ID.
43552 @c man begin SEEALSO gcore
43554 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43555 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43556 documentation are properly installed at your site, the command
43563 should give you access to the complete manual.
43565 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43566 Richard M. Stallman and Roland H. Pesch, July 1991.
43573 @c man title gdbinit GDB initialization scripts
43576 @c man begin SYNOPSIS gdbinit
43577 @ifset SYSTEM_GDBINIT
43578 @value{SYSTEM_GDBINIT}
43587 @c man begin DESCRIPTION gdbinit
43588 These files contain @value{GDBN} commands to automatically execute during
43589 @value{GDBN} startup. The lines of contents are canned sequences of commands,
43592 the @value{GDBN} manual in node @code{Sequences}
43593 -- shell command @code{info -f gdb -n Sequences}.
43599 Please read more in
43601 the @value{GDBN} manual in node @code{Startup}
43602 -- shell command @code{info -f gdb -n Startup}.
43609 @ifset SYSTEM_GDBINIT
43610 @item @value{SYSTEM_GDBINIT}
43612 @ifclear SYSTEM_GDBINIT
43613 @item (not enabled with @code{--with-system-gdbinit} during compilation)
43615 System-wide initialization file. It is executed unless user specified
43616 @value{GDBN} option @code{-nx} or @code{-n}.
43619 the @value{GDBN} manual in node @code{System-wide configuration}
43620 -- shell command @code{info -f gdb -n 'System-wide configuration'}.
43623 @ref{System-wide configuration}.
43627 User initialization file. It is executed unless user specified
43628 @value{GDBN} options @code{-nx}, @code{-n} or @code{-nh}.
43631 Initialization file for current directory. It may need to be enabled with
43632 @value{GDBN} security command @code{set auto-load local-gdbinit}.
43635 the @value{GDBN} manual in node @code{Init File in the Current Directory}
43636 -- shell command @code{info -f gdb -n 'Init File in the Current Directory'}.
43639 @ref{Init File in the Current Directory}.
43644 @c man begin SEEALSO gdbinit
43646 gdb(1), @code{info -f gdb -n Startup}
43648 The full documentation for @value{GDBN} is maintained as a Texinfo manual.
43649 If the @code{info} and @code{gdb} programs and @value{GDBN}'s Texinfo
43650 documentation are properly installed at your site, the command
43656 should give you access to the complete manual.
43658 @cite{Using GDB: A Guide to the GNU Source-Level Debugger},
43659 Richard M. Stallman and Roland H. Pesch, July 1991.
43665 @node GNU Free Documentation License
43666 @appendix GNU Free Documentation License
43669 @node Concept Index
43670 @unnumbered Concept Index
43674 @node Command and Variable Index
43675 @unnumbered Command, Variable, and Function Index
43680 % I think something like @@colophon should be in texinfo. In the
43682 \long\def\colophon{\hbox to0pt{}\vfill
43683 \centerline{The body of this manual is set in}
43684 \centerline{\fontname\tenrm,}
43685 \centerline{with headings in {\bf\fontname\tenbf}}
43686 \centerline{and examples in {\tt\fontname\tentt}.}
43687 \centerline{{\it\fontname\tenit\/},}
43688 \centerline{{\bf\fontname\tenbf}, and}
43689 \centerline{{\sl\fontname\tensl\/}}
43690 \centerline{are used for emphasis.}\vfill}
43692 % Blame: doc@@cygnus.com, 1991.