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.
11 @settitle Debugging with @value{GDBN}
12 @setchapternewpage odd
21 @c To avoid file-name clashes between index.html and Index.html, when
22 @c the manual is produced on a Posix host and then moved to a
23 @c case-insensitive filesystem (e.g., MS-Windows), we separate the
24 @c indices into two: Concept Index and all the rest.
28 @c readline appendices use @vindex, @findex and @ftable,
29 @c annotate.texi and gdbmi use @findex.
32 @c !!set GDB manual's edition---not the same as GDB version!
33 @c This is updated by GNU Press.
36 @c !!set GDB edit command default editor
39 @c THIS MANUAL REQUIRES TEXINFO 4.0 OR LATER.
41 @c This is a dir.info fragment to support semi-automated addition of
42 @c manuals to an info tree.
43 @dircategory Software development
45 * Gdb: (gdb). The GNU debugger.
49 Copyright @copyright{} 1988-2013 Free Software Foundation, Inc.
51 Permission is granted to copy, distribute and/or modify this document
52 under the terms of the GNU Free Documentation License, Version 1.3 or
53 any later version published by the Free Software Foundation; with the
54 Invariant Sections being ``Free Software'' and ``Free Software Needs
55 Free Documentation'', with the Front-Cover Texts being ``A GNU Manual,''
56 and with the Back-Cover Texts as in (a) below.
58 (a) The FSF's Back-Cover Text is: ``You are free to copy and modify
59 this GNU Manual. Buying copies from GNU Press supports the FSF in
60 developing GNU and promoting software freedom.''
64 This file documents the @sc{gnu} debugger @value{GDBN}.
66 This is the @value{EDITION} Edition, of @cite{Debugging with
67 @value{GDBN}: the @sc{gnu} Source-Level Debugger} for @value{GDBN}
68 @ifset VERSION_PACKAGE
69 @value{VERSION_PACKAGE}
71 Version @value{GDBVN}.
77 @title Debugging with @value{GDBN}
78 @subtitle The @sc{gnu} Source-Level Debugger
80 @subtitle @value{EDITION} Edition, for @value{GDBN} version @value{GDBVN}
81 @ifset VERSION_PACKAGE
83 @subtitle @value{VERSION_PACKAGE}
85 @author Richard Stallman, Roland Pesch, Stan Shebs, et al.
89 \hfill (Send bugs and comments on @value{GDBN} to @value{BUGURL}.)\par
90 \hfill {\it Debugging with @value{GDBN}}\par
91 \hfill \TeX{}info \texinfoversion\par
95 @vskip 0pt plus 1filll
96 Published by the Free Software Foundation @*
97 51 Franklin Street, Fifth Floor,
98 Boston, MA 02110-1301, USA@*
99 ISBN 978-0-9831592-3-0 @*
106 @node Top, Summary, (dir), (dir)
108 @top Debugging with @value{GDBN}
110 This file describes @value{GDBN}, the @sc{gnu} symbolic debugger.
112 This is the @value{EDITION} Edition, for @value{GDBN}
113 @ifset VERSION_PACKAGE
114 @value{VERSION_PACKAGE}
116 Version @value{GDBVN}.
118 Copyright (C) 1988-2013 Free Software Foundation, Inc.
120 This edition of the GDB manual is dedicated to the memory of Fred
121 Fish. Fred was a long-standing contributor to GDB and to Free
122 software in general. We will miss him.
125 * Summary:: Summary of @value{GDBN}
126 * Sample Session:: A sample @value{GDBN} session
128 * Invocation:: Getting in and out of @value{GDBN}
129 * Commands:: @value{GDBN} commands
130 * Running:: Running programs under @value{GDBN}
131 * Stopping:: Stopping and continuing
132 * Reverse Execution:: Running programs backward
133 * Process Record and Replay:: Recording inferior's execution and replaying it
134 * Stack:: Examining the stack
135 * Source:: Examining source files
136 * Data:: Examining data
137 * Optimized Code:: Debugging optimized code
138 * Macros:: Preprocessor Macros
139 * Tracepoints:: Debugging remote targets non-intrusively
140 * Overlays:: Debugging programs that use overlays
142 * Languages:: Using @value{GDBN} with different languages
144 * Symbols:: Examining the symbol table
145 * Altering:: Altering execution
146 * GDB Files:: @value{GDBN} files
147 * Targets:: Specifying a debugging target
148 * Remote Debugging:: Debugging remote programs
149 * Configurations:: Configuration-specific information
150 * Controlling GDB:: Controlling @value{GDBN}
151 * Extending GDB:: Extending @value{GDBN}
152 * Interpreters:: Command Interpreters
153 * TUI:: @value{GDBN} Text User Interface
154 * Emacs:: Using @value{GDBN} under @sc{gnu} Emacs
155 * GDB/MI:: @value{GDBN}'s Machine Interface.
156 * Annotations:: @value{GDBN}'s annotation interface.
157 * JIT Interface:: Using the JIT debugging interface.
158 * In-Process Agent:: In-Process Agent
160 * GDB Bugs:: Reporting bugs in @value{GDBN}
162 @ifset SYSTEM_READLINE
163 * Command Line Editing: (rluserman). Command Line Editing
164 * Using History Interactively: (history). Using History Interactively
166 @ifclear SYSTEM_READLINE
167 * Command Line Editing:: Command Line Editing
168 * Using History Interactively:: Using History Interactively
170 * In Memoriam:: In Memoriam
171 * Formatting Documentation:: How to format and print @value{GDBN} documentation
172 * Installing GDB:: Installing GDB
173 * Maintenance Commands:: Maintenance Commands
174 * Remote Protocol:: GDB Remote Serial Protocol
175 * Agent Expressions:: The GDB Agent Expression Mechanism
176 * Target Descriptions:: How targets can describe themselves to
178 * Operating System Information:: Getting additional information from
180 * Trace File Format:: GDB trace file format
181 * Index Section Format:: .gdb_index section format
182 * Copying:: GNU General Public License says
183 how you can copy and share GDB
184 * GNU Free Documentation License:: The license for this documentation
185 * Concept Index:: Index of @value{GDBN} concepts
186 * Command and Variable Index:: Index of @value{GDBN} commands, variables,
187 functions, and Python data types
195 @unnumbered Summary of @value{GDBN}
197 The purpose of a debugger such as @value{GDBN} is to allow you to see what is
198 going on ``inside'' another program while it executes---or what another
199 program was doing at the moment it crashed.
201 @value{GDBN} can do four main kinds of things (plus other things in support of
202 these) to help you catch bugs in the act:
206 Start your program, specifying anything that might affect its behavior.
209 Make your program stop on specified conditions.
212 Examine what has happened, when your program has stopped.
215 Change things in your program, so you can experiment with correcting the
216 effects of one bug and go on to learn about another.
219 You can use @value{GDBN} to debug programs written in C and C@t{++}.
220 For more information, see @ref{Supported Languages,,Supported Languages}.
221 For more information, see @ref{C,,C and C++}.
223 Support for D is partial. For information on D, see
227 Support for Modula-2 is partial. For information on Modula-2, see
228 @ref{Modula-2,,Modula-2}.
230 Support for OpenCL C is partial. For information on OpenCL C, see
231 @ref{OpenCL C,,OpenCL C}.
234 Debugging Pascal programs which use sets, subranges, file variables, or
235 nested functions does not currently work. @value{GDBN} does not support
236 entering expressions, printing values, or similar features using Pascal
240 @value{GDBN} can be used to debug programs written in Fortran, although
241 it may be necessary to refer to some variables with a trailing
244 @value{GDBN} can be used to debug programs written in Objective-C,
245 using either the Apple/NeXT or the GNU Objective-C runtime.
248 * Free Software:: Freely redistributable software
249 * Free Documentation:: Free Software Needs Free Documentation
250 * Contributors:: Contributors to GDB
254 @unnumberedsec Free Software
256 @value{GDBN} is @dfn{free software}, protected by the @sc{gnu}
257 General Public License
258 (GPL). The GPL gives you the freedom to copy or adapt a licensed
259 program---but every person getting a copy also gets with it the
260 freedom to modify that copy (which means that they must get access to
261 the source code), and the freedom to distribute further copies.
262 Typical software companies use copyrights to limit your freedoms; the
263 Free Software Foundation uses the GPL to preserve these freedoms.
265 Fundamentally, the General Public License is a license which says that
266 you have these freedoms and that you cannot take these freedoms away
269 @node Free Documentation
270 @unnumberedsec Free Software Needs Free Documentation
272 The biggest deficiency in the free software community today is not in
273 the software---it is the lack of good free documentation that we can
274 include with the free software. Many of our most important
275 programs do not come with free reference manuals and free introductory
276 texts. Documentation is an essential part of any software package;
277 when an important free software package does not come with a free
278 manual and a free tutorial, that is a major gap. We have many such
281 Consider Perl, for instance. The tutorial manuals that people
282 normally use are non-free. How did this come about? Because the
283 authors of those manuals published them with restrictive terms---no
284 copying, no modification, source files not available---which exclude
285 them from the free software world.
287 That wasn't the first time this sort of thing happened, and it was far
288 from the last. Many times we have heard a GNU user eagerly describe a
289 manual that he is writing, his intended contribution to the community,
290 only to learn that he had ruined everything by signing a publication
291 contract to make it non-free.
293 Free documentation, like free software, is a matter of freedom, not
294 price. The problem with the non-free manual is not that publishers
295 charge a price for printed copies---that in itself is fine. (The Free
296 Software Foundation sells printed copies of manuals, too.) The
297 problem is the restrictions on the use of the manual. Free manuals
298 are available in source code form, and give you permission to copy and
299 modify. Non-free manuals do not allow this.
301 The criteria of freedom for a free manual are roughly the same as for
302 free software. Redistribution (including the normal kinds of
303 commercial redistribution) must be permitted, so that the manual can
304 accompany every copy of the program, both on-line and on paper.
306 Permission for modification of the technical content is crucial too.
307 When people modify the software, adding or changing features, if they
308 are conscientious they will change the manual too---so they can
309 provide accurate and clear documentation for the modified program. A
310 manual that leaves you no choice but to write a new manual to document
311 a changed version of the program is not really available to our
314 Some kinds of limits on the way modification is handled are
315 acceptable. For example, requirements to preserve the original
316 author's copyright notice, the distribution terms, or the list of
317 authors, are ok. It is also no problem to require modified versions
318 to include notice that they were modified. Even entire sections that
319 may not be deleted or changed are acceptable, as long as they deal
320 with nontechnical topics (like this one). These kinds of restrictions
321 are acceptable because they don't obstruct the community's normal use
324 However, it must be possible to modify all the @emph{technical}
325 content of the manual, and then distribute the result in all the usual
326 media, through all the usual channels. Otherwise, the restrictions
327 obstruct the use of the manual, it is not free, and we need another
328 manual to replace it.
330 Please spread the word about this issue. Our community continues to
331 lose manuals to proprietary publishing. If we spread the word that
332 free software needs free reference manuals and free tutorials, perhaps
333 the next person who wants to contribute by writing documentation will
334 realize, before it is too late, that only free manuals contribute to
335 the free software community.
337 If you are writing documentation, please insist on publishing it under
338 the GNU Free Documentation License or another free documentation
339 license. Remember that this decision requires your approval---you
340 don't have to let the publisher decide. Some commercial publishers
341 will use a free license if you insist, but they will not propose the
342 option; it is up to you to raise the issue and say firmly that this is
343 what you want. If the publisher you are dealing with refuses, please
344 try other publishers. If you're not sure whether a proposed license
345 is free, write to @email{licensing@@gnu.org}.
347 You can encourage commercial publishers to sell more free, copylefted
348 manuals and tutorials by buying them, and particularly by buying
349 copies from the publishers that paid for their writing or for major
350 improvements. Meanwhile, try to avoid buying non-free documentation
351 at all. Check the distribution terms of a manual before you buy it,
352 and insist that whoever seeks your business must respect your freedom.
353 Check the history of the book, and try to reward the publishers that
354 have paid or pay the authors to work on it.
356 The Free Software Foundation maintains a list of free documentation
357 published by other publishers, at
358 @url{http://www.fsf.org/doc/other-free-books.html}.
361 @unnumberedsec Contributors to @value{GDBN}
363 Richard Stallman was the original author of @value{GDBN}, and of many
364 other @sc{gnu} programs. Many others have contributed to its
365 development. This section attempts to credit major contributors. One
366 of the virtues of free software is that everyone is free to contribute
367 to it; with regret, we cannot actually acknowledge everyone here. The
368 file @file{ChangeLog} in the @value{GDBN} distribution approximates a
369 blow-by-blow account.
371 Changes much prior to version 2.0 are lost in the mists of time.
374 @emph{Plea:} Additions to this section are particularly welcome. If you
375 or your friends (or enemies, to be evenhanded) have been unfairly
376 omitted from this list, we would like to add your names!
379 So that they may not regard their many labors as thankless, we
380 particularly thank those who shepherded @value{GDBN} through major
382 Andrew Cagney (releases 6.3, 6.2, 6.1, 6.0, 5.3, 5.2, 5.1 and 5.0);
383 Jim Blandy (release 4.18);
384 Jason Molenda (release 4.17);
385 Stan Shebs (release 4.14);
386 Fred Fish (releases 4.16, 4.15, 4.13, 4.12, 4.11, 4.10, and 4.9);
387 Stu Grossman and John Gilmore (releases 4.8, 4.7, 4.6, 4.5, and 4.4);
388 John Gilmore (releases 4.3, 4.2, 4.1, 4.0, and 3.9);
389 Jim Kingdon (releases 3.5, 3.4, and 3.3);
390 and Randy Smith (releases 3.2, 3.1, and 3.0).
392 Richard Stallman, assisted at various times by Peter TerMaat, Chris
393 Hanson, and Richard Mlynarik, handled releases through 2.8.
395 Michael Tiemann is the author of most of the @sc{gnu} C@t{++} support
396 in @value{GDBN}, with significant additional contributions from Per
397 Bothner and Daniel Berlin. James Clark wrote the @sc{gnu} C@t{++}
398 demangler. Early work on C@t{++} was by Peter TerMaat (who also did
399 much general update work leading to release 3.0).
401 @value{GDBN} uses the BFD subroutine library to examine multiple
402 object-file formats; BFD was a joint project of David V.
403 Henkel-Wallace, Rich Pixley, Steve Chamberlain, and John Gilmore.
405 David Johnson wrote the original COFF support; Pace Willison did
406 the original support for encapsulated COFF.
408 Brent Benson of Harris Computer Systems contributed DWARF 2 support.
410 Adam de Boor and Bradley Davis contributed the ISI Optimum V support.
411 Per Bothner, Noboyuki Hikichi, and Alessandro Forin contributed MIPS
413 Jean-Daniel Fekete contributed Sun 386i support.
414 Chris Hanson improved the HP9000 support.
415 Noboyuki Hikichi and Tomoyuki Hasei contributed Sony/News OS 3 support.
416 David Johnson contributed Encore Umax support.
417 Jyrki Kuoppala contributed Altos 3068 support.
418 Jeff Law contributed HP PA and SOM support.
419 Keith Packard contributed NS32K support.
420 Doug Rabson contributed Acorn Risc Machine support.
421 Bob Rusk contributed Harris Nighthawk CX-UX support.
422 Chris Smith contributed Convex support (and Fortran debugging).
423 Jonathan Stone contributed Pyramid support.
424 Michael Tiemann contributed SPARC support.
425 Tim Tucker contributed support for the Gould NP1 and Gould Powernode.
426 Pace Willison contributed Intel 386 support.
427 Jay Vosburgh contributed Symmetry support.
428 Marko Mlinar contributed OpenRISC 1000 support.
430 Andreas Schwab contributed M68K @sc{gnu}/Linux support.
432 Rich Schaefer and Peter Schauer helped with support of SunOS shared
435 Jay Fenlason and Roland McGrath ensured that @value{GDBN} and GAS agree
436 about several machine instruction sets.
438 Patrick Duval, Ted Goldstein, Vikram Koka and Glenn Engel helped develop
439 remote debugging. Intel Corporation, Wind River Systems, AMD, and ARM
440 contributed remote debugging modules for the i960, VxWorks, A29K UDI,
441 and RDI targets, respectively.
443 Brian Fox is the author of the readline libraries providing
444 command-line editing and command history.
446 Andrew Beers of SUNY Buffalo wrote the language-switching code, the
447 Modula-2 support, and contributed the Languages chapter of this manual.
449 Fred Fish wrote most of the support for Unix System Vr4.
450 He also enhanced the command-completion support to cover C@t{++} overloaded
453 Hitachi America (now Renesas America), Ltd. sponsored the support for
454 H8/300, H8/500, and Super-H processors.
456 NEC sponsored the support for the v850, Vr4xxx, and Vr5xxx processors.
458 Mitsubishi (now Renesas) sponsored the support for D10V, D30V, and M32R/D
461 Toshiba sponsored the support for the TX39 Mips processor.
463 Matsushita sponsored the support for the MN10200 and MN10300 processors.
465 Fujitsu sponsored the support for SPARClite and FR30 processors.
467 Kung Hsu, Jeff Law, and Rick Sladkey added support for hardware
470 Michael Snyder added support for tracepoints.
472 Stu Grossman wrote gdbserver.
474 Jim Kingdon, Peter Schauer, Ian Taylor, and Stu Grossman made
475 nearly innumerable bug fixes and cleanups throughout @value{GDBN}.
477 The following people at the Hewlett-Packard Company contributed
478 support for the PA-RISC 2.0 architecture, HP-UX 10.20, 10.30, and 11.0
479 (narrow mode), HP's implementation of kernel threads, HP's aC@t{++}
480 compiler, and the Text User Interface (nee Terminal User Interface):
481 Ben Krepp, Richard Title, John Bishop, Susan Macchia, Kathy Mann,
482 Satish Pai, India Paul, Steve Rehrauer, and Elena Zannoni. Kim Haase
483 provided HP-specific information in this manual.
485 DJ Delorie ported @value{GDBN} to MS-DOS, for the DJGPP project.
486 Robert Hoehne made significant contributions to the DJGPP port.
488 Cygnus Solutions has sponsored @value{GDBN} maintenance and much of its
489 development since 1991. Cygnus engineers who have worked on @value{GDBN}
490 fulltime include Mark Alexander, Jim Blandy, Per Bothner, Kevin
491 Buettner, Edith Epstein, Chris Faylor, Fred Fish, Martin Hunt, Jim
492 Ingham, John Gilmore, Stu Grossman, Kung Hsu, Jim Kingdon, John Metzler,
493 Fernando Nasser, Geoffrey Noer, Dawn Perchik, Rich Pixley, Zdenek
494 Radouch, Keith Seitz, Stan Shebs, David Taylor, and Elena Zannoni. In
495 addition, Dave Brolley, Ian Carmichael, Steve Chamberlain, Nick Clifton,
496 JT Conklin, Stan Cox, DJ Delorie, Ulrich Drepper, Frank Eigler, Doug
497 Evans, Sean Fagan, David Henkel-Wallace, Richard Henderson, Jeff
498 Holcomb, Jeff Law, Jim Lemke, Tom Lord, Bob Manson, Michael Meissner,
499 Jason Merrill, Catherine Moore, Drew Moseley, Ken Raeburn, Gavin
500 Romig-Koch, Rob Savoye, Jamie Smith, Mike Stump, Ian Taylor, Angela
501 Thomas, Michael Tiemann, Tom Tromey, Ron Unrau, Jim Wilson, and David
502 Zuhn have made contributions both large and small.
504 Andrew Cagney, Fernando Nasser, and Elena Zannoni, while working for
505 Cygnus Solutions, implemented the original @sc{gdb/mi} interface.
507 Jim Blandy added support for preprocessor macros, while working for Red
510 Andrew Cagney designed @value{GDBN}'s architecture vector. Many
511 people including Andrew Cagney, Stephane Carrez, Randolph Chung, Nick
512 Duffek, Richard Henderson, Mark Kettenis, Grace Sainsbury, Kei
513 Sakamoto, Yoshinori Sato, Michael Snyder, Andreas Schwab, Jason
514 Thorpe, Corinna Vinschen, Ulrich Weigand, and Elena Zannoni, helped
515 with the migration of old architectures to this new framework.
517 Andrew Cagney completely re-designed and re-implemented @value{GDBN}'s
518 unwinder framework, this consisting of a fresh new design featuring
519 frame IDs, independent frame sniffers, and the sentinel frame. Mark
520 Kettenis implemented the @sc{dwarf 2} unwinder, Jeff Johnston the
521 libunwind unwinder, and Andrew Cagney the dummy, sentinel, tramp, and
522 trad unwinders. The architecture-specific changes, each involving a
523 complete rewrite of the architecture's frame code, were carried out by
524 Jim Blandy, Joel Brobecker, Kevin Buettner, Andrew Cagney, Stephane
525 Carrez, Randolph Chung, Orjan Friberg, Richard Henderson, Daniel
526 Jacobowitz, Jeff Johnston, Mark Kettenis, Theodore A. Roth, Kei
527 Sakamoto, Yoshinori Sato, Michael Snyder, Corinna Vinschen, and Ulrich
530 Christian Zankel, Ross Morley, Bob Wilson, and Maxim Grigoriev from
531 Tensilica, Inc.@: contributed support for Xtensa processors. Others
532 who have worked on the Xtensa port of @value{GDBN} in the past include
533 Steve Tjiang, John Newlin, and Scott Foehner.
535 Michael Eager and staff of Xilinx, Inc., contributed support for the
536 Xilinx MicroBlaze architecture.
539 @chapter A Sample @value{GDBN} Session
541 You can use this manual at your leisure to read all about @value{GDBN}.
542 However, a handful of commands are enough to get started using the
543 debugger. This chapter illustrates those commands.
546 In this sample session, we emphasize user input like this: @b{input},
547 to make it easier to pick out from the surrounding output.
550 @c FIXME: this example may not be appropriate for some configs, where
551 @c FIXME...primary interest is in remote use.
553 One of the preliminary versions of @sc{gnu} @code{m4} (a generic macro
554 processor) exhibits the following bug: sometimes, when we change its
555 quote strings from the default, the commands used to capture one macro
556 definition within another stop working. In the following short @code{m4}
557 session, we define a macro @code{foo} which expands to @code{0000}; we
558 then use the @code{m4} built-in @code{defn} to define @code{bar} as the
559 same thing. However, when we change the open quote string to
560 @code{<QUOTE>} and the close quote string to @code{<UNQUOTE>}, the same
561 procedure fails to define a new synonym @code{baz}:
570 @b{define(bar,defn(`foo'))}
574 @b{changequote(<QUOTE>,<UNQUOTE>)}
576 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
579 m4: End of input: 0: fatal error: EOF in string
583 Let us use @value{GDBN} to try to see what is going on.
586 $ @b{@value{GDBP} m4}
587 @c FIXME: this falsifies the exact text played out, to permit smallbook
588 @c FIXME... format to come out better.
589 @value{GDBN} is free software and you are welcome to distribute copies
590 of it under certain conditions; type "show copying" to see
592 There is absolutely no warranty for @value{GDBN}; type "show warranty"
595 @value{GDBN} @value{GDBVN}, Copyright 1999 Free Software Foundation, Inc...
600 @value{GDBN} reads only enough symbol data to know where to find the
601 rest when needed; as a result, the first prompt comes up very quickly.
602 We now tell @value{GDBN} to use a narrower display width than usual, so
603 that examples fit in this manual.
606 (@value{GDBP}) @b{set width 70}
610 We need to see how the @code{m4} built-in @code{changequote} works.
611 Having looked at the source, we know the relevant subroutine is
612 @code{m4_changequote}, so we set a breakpoint there with the @value{GDBN}
613 @code{break} command.
616 (@value{GDBP}) @b{break m4_changequote}
617 Breakpoint 1 at 0x62f4: file builtin.c, line 879.
621 Using the @code{run} command, we start @code{m4} running under @value{GDBN}
622 control; as long as control does not reach the @code{m4_changequote}
623 subroutine, the program runs as usual:
626 (@value{GDBP}) @b{run}
627 Starting program: /work/Editorial/gdb/gnu/m4/m4
635 To trigger the breakpoint, we call @code{changequote}. @value{GDBN}
636 suspends execution of @code{m4}, displaying information about the
637 context where it stops.
640 @b{changequote(<QUOTE>,<UNQUOTE>)}
642 Breakpoint 1, m4_changequote (argc=3, argv=0x33c70)
644 879 if (bad_argc(TOKEN_DATA_TEXT(argv[0]),argc,1,3))
648 Now we use the command @code{n} (@code{next}) to advance execution to
649 the next line of the current function.
653 882 set_quotes((argc >= 2) ? TOKEN_DATA_TEXT(argv[1])\
658 @code{set_quotes} looks like a promising subroutine. We can go into it
659 by using the command @code{s} (@code{step}) instead of @code{next}.
660 @code{step} goes to the next line to be executed in @emph{any}
661 subroutine, so it steps into @code{set_quotes}.
665 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
667 530 if (lquote != def_lquote)
671 The display that shows the subroutine where @code{m4} is now
672 suspended (and its arguments) is called a stack frame display. It
673 shows a summary of the stack. We can use the @code{backtrace}
674 command (which can also be spelled @code{bt}), to see where we are
675 in the stack as a whole: the @code{backtrace} command displays a
676 stack frame for each active subroutine.
679 (@value{GDBP}) @b{bt}
680 #0 set_quotes (lq=0x34c78 "<QUOTE>", rq=0x34c88 "<UNQUOTE>")
682 #1 0x6344 in m4_changequote (argc=3, argv=0x33c70)
684 #2 0x8174 in expand_macro (sym=0x33320) at macro.c:242
685 #3 0x7a88 in expand_token (obs=0x0, t=209696, td=0xf7fffa30)
687 #4 0x79dc in expand_input () at macro.c:40
688 #5 0x2930 in main (argc=0, argv=0xf7fffb20) at m4.c:195
692 We step through a few more lines to see what happens. The first two
693 times, we can use @samp{s}; the next two times we use @code{n} to avoid
694 falling into the @code{xstrdup} subroutine.
698 0x3b5c 532 if (rquote != def_rquote)
700 0x3b80 535 lquote = (lq == nil || *lq == '\0') ? \
701 def_lquote : xstrdup(lq);
703 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
706 538 len_lquote = strlen(rquote);
710 The last line displayed looks a little odd; we can examine the variables
711 @code{lquote} and @code{rquote} to see if they are in fact the new left
712 and right quotes we specified. We use the command @code{p}
713 (@code{print}) to see their values.
716 (@value{GDBP}) @b{p lquote}
717 $1 = 0x35d40 "<QUOTE>"
718 (@value{GDBP}) @b{p rquote}
719 $2 = 0x35d50 "<UNQUOTE>"
723 @code{lquote} and @code{rquote} are indeed the new left and right quotes.
724 To look at some context, we can display ten lines of source
725 surrounding the current line with the @code{l} (@code{list}) command.
731 535 lquote = (lq == nil || *lq == '\0') ? def_lquote\
733 536 rquote = (rq == nil || *rq == '\0') ? def_rquote\
736 538 len_lquote = strlen(rquote);
737 539 len_rquote = strlen(lquote);
744 Let us step past the two lines that set @code{len_lquote} and
745 @code{len_rquote}, and then examine the values of those variables.
749 539 len_rquote = strlen(lquote);
752 (@value{GDBP}) @b{p len_lquote}
754 (@value{GDBP}) @b{p len_rquote}
759 That certainly looks wrong, assuming @code{len_lquote} and
760 @code{len_rquote} are meant to be the lengths of @code{lquote} and
761 @code{rquote} respectively. We can set them to better values using
762 the @code{p} command, since it can print the value of
763 any expression---and that expression can include subroutine calls and
767 (@value{GDBP}) @b{p len_lquote=strlen(lquote)}
769 (@value{GDBP}) @b{p len_rquote=strlen(rquote)}
774 Is that enough to fix the problem of using the new quotes with the
775 @code{m4} built-in @code{defn}? We can allow @code{m4} to continue
776 executing with the @code{c} (@code{continue}) command, and then try the
777 example that caused trouble initially:
783 @b{define(baz,defn(<QUOTE>foo<UNQUOTE>))}
790 Success! The new quotes now work just as well as the default ones. The
791 problem seems to have been just the two typos defining the wrong
792 lengths. We allow @code{m4} exit by giving it an EOF as input:
796 Program exited normally.
800 The message @samp{Program exited normally.} is from @value{GDBN}; it
801 indicates @code{m4} has finished executing. We can end our @value{GDBN}
802 session with the @value{GDBN} @code{quit} command.
805 (@value{GDBP}) @b{quit}
809 @chapter Getting In and Out of @value{GDBN}
811 This chapter discusses how to start @value{GDBN}, and how to get out of it.
815 type @samp{@value{GDBP}} to start @value{GDBN}.
817 type @kbd{quit} or @kbd{Ctrl-d} to exit.
821 * Invoking GDB:: How to start @value{GDBN}
822 * Quitting GDB:: How to quit @value{GDBN}
823 * Shell Commands:: How to use shell commands inside @value{GDBN}
824 * Logging Output:: How to log @value{GDBN}'s output to a file
828 @section Invoking @value{GDBN}
830 Invoke @value{GDBN} by running the program @code{@value{GDBP}}. Once started,
831 @value{GDBN} reads commands from the terminal until you tell it to exit.
833 You can also run @code{@value{GDBP}} with a variety of arguments and options,
834 to specify more of your debugging environment at the outset.
836 The command-line options described here are designed
837 to cover a variety of situations; in some environments, some of these
838 options may effectively be unavailable.
840 The most usual way to start @value{GDBN} is with one argument,
841 specifying an executable program:
844 @value{GDBP} @var{program}
848 You can also start with both an executable program and a core file
852 @value{GDBP} @var{program} @var{core}
855 You can, instead, specify a process ID as a second argument, if you want
856 to debug a running process:
859 @value{GDBP} @var{program} 1234
863 would attach @value{GDBN} to process @code{1234} (unless you also have a file
864 named @file{1234}; @value{GDBN} does check for a core file first).
866 Taking advantage of the second command-line argument requires a fairly
867 complete operating system; when you use @value{GDBN} as a remote
868 debugger attached to a bare board, there may not be any notion of
869 ``process'', and there is often no way to get a core dump. @value{GDBN}
870 will warn you if it is unable to attach or to read core dumps.
872 You can optionally have @code{@value{GDBP}} pass any arguments after the
873 executable file to the inferior using @code{--args}. This option stops
876 @value{GDBP} --args gcc -O2 -c foo.c
878 This will cause @code{@value{GDBP}} to debug @code{gcc}, and to set
879 @code{gcc}'s command-line arguments (@pxref{Arguments}) to @samp{-O2 -c foo.c}.
881 You can run @code{@value{GDBP}} without printing the front material, which describes
882 @value{GDBN}'s non-warranty, by specifying @code{-silent}:
889 You can further control how @value{GDBN} starts up by using command-line
890 options. @value{GDBN} itself can remind you of the options available.
900 to display all available options and briefly describe their use
901 (@samp{@value{GDBP} -h} is a shorter equivalent).
903 All options and command line arguments you give are processed
904 in sequential order. The order makes a difference when the
905 @samp{-x} option is used.
909 * File Options:: Choosing files
910 * Mode Options:: Choosing modes
911 * Startup:: What @value{GDBN} does during startup
915 @subsection Choosing Files
917 When @value{GDBN} starts, it reads any arguments other than options as
918 specifying an executable file and core file (or process ID). This is
919 the same as if the arguments were specified by the @samp{-se} and
920 @samp{-c} (or @samp{-p}) options respectively. (@value{GDBN} reads the
921 first argument that does not have an associated option flag as
922 equivalent to the @samp{-se} option followed by that argument; and the
923 second argument that does not have an associated option flag, if any, as
924 equivalent to the @samp{-c}/@samp{-p} option followed by that argument.)
925 If the second argument begins with a decimal digit, @value{GDBN} will
926 first attempt to attach to it as a process, and if that fails, attempt
927 to open it as a corefile. If you have a corefile whose name begins with
928 a digit, you can prevent @value{GDBN} from treating it as a pid by
929 prefixing it with @file{./}, e.g.@: @file{./12345}.
931 If @value{GDBN} has not been configured to included core file support,
932 such as for most embedded targets, then it will complain about a second
933 argument and ignore it.
935 Many options have both long and short forms; both are shown in the
936 following list. @value{GDBN} also recognizes the long forms if you truncate
937 them, so long as enough of the option is present to be unambiguous.
938 (If you prefer, you can flag option arguments with @samp{--} rather
939 than @samp{-}, though we illustrate the more usual convention.)
941 @c NOTE: the @cindex entries here use double dashes ON PURPOSE. This
942 @c way, both those who look for -foo and --foo in the index, will find
946 @item -symbols @var{file}
948 @cindex @code{--symbols}
950 Read symbol table from file @var{file}.
952 @item -exec @var{file}
954 @cindex @code{--exec}
956 Use file @var{file} as the executable file to execute when appropriate,
957 and for examining pure data in conjunction with a core dump.
961 Read symbol table from file @var{file} and use it as the executable
964 @item -core @var{file}
966 @cindex @code{--core}
968 Use file @var{file} as a core dump to examine.
970 @item -pid @var{number}
971 @itemx -p @var{number}
974 Connect to process ID @var{number}, as with the @code{attach} command.
976 @item -command @var{file}
978 @cindex @code{--command}
980 Execute commands from file @var{file}. The contents of this file is
981 evaluated exactly as the @code{source} command would.
982 @xref{Command Files,, Command files}.
984 @item -eval-command @var{command}
985 @itemx -ex @var{command}
986 @cindex @code{--eval-command}
988 Execute a single @value{GDBN} command.
990 This option may be used multiple times to call multiple commands. It may
991 also be interleaved with @samp{-command} as required.
994 @value{GDBP} -ex 'target sim' -ex 'load' \
995 -x setbreakpoints -ex 'run' a.out
998 @item -init-command @var{file}
999 @itemx -ix @var{file}
1000 @cindex @code{--init-command}
1002 Execute commands from file @var{file} before loading the inferior (but
1003 after loading gdbinit files).
1006 @item -init-eval-command @var{command}
1007 @itemx -iex @var{command}
1008 @cindex @code{--init-eval-command}
1010 Execute a single @value{GDBN} command before loading the inferior (but
1011 after loading gdbinit files).
1014 @item -directory @var{directory}
1015 @itemx -d @var{directory}
1016 @cindex @code{--directory}
1018 Add @var{directory} to the path to search for source and script files.
1022 @cindex @code{--readnow}
1024 Read each symbol file's entire symbol table immediately, rather than
1025 the default, which is to read it incrementally as it is needed.
1026 This makes startup slower, but makes future operations faster.
1031 @subsection Choosing Modes
1033 You can run @value{GDBN} in various alternative modes---for example, in
1034 batch mode or quiet mode.
1042 Do not execute commands found in any initialization file.
1043 There are three init files, loaded in the following order:
1046 @item @file{system.gdbinit}
1047 This is the system-wide init file.
1048 Its location is specified with the @code{--with-system-gdbinit}
1049 configure option (@pxref{System-wide configuration}).
1050 It is loaded first when @value{GDBN} starts, before command line options
1051 have been processed.
1052 @item @file{~/.gdbinit}
1053 This is the init file in your home directory.
1054 It is loaded next, after @file{system.gdbinit}, and before
1055 command options have been processed.
1056 @item @file{./.gdbinit}
1057 This is the init file in the current directory.
1058 It is loaded last, after command line options other than @code{-x} and
1059 @code{-ex} have been processed. Command line options @code{-x} and
1060 @code{-ex} are processed last, after @file{./.gdbinit} has been loaded.
1063 For further documentation on startup processing, @xref{Startup}.
1064 For documentation on how to write command files,
1065 @xref{Command Files,,Command Files}.
1070 Do not execute commands found in @file{~/.gdbinit}, the init file
1071 in your home directory.
1077 @cindex @code{--quiet}
1078 @cindex @code{--silent}
1080 ``Quiet''. Do not print the introductory and copyright messages. These
1081 messages are also suppressed in batch mode.
1084 @cindex @code{--batch}
1085 Run in batch mode. Exit with status @code{0} after processing all the
1086 command files specified with @samp{-x} (and all commands from
1087 initialization files, if not inhibited with @samp{-n}). Exit with
1088 nonzero status if an error occurs in executing the @value{GDBN} commands
1089 in the command files. Batch mode also disables pagination, sets unlimited
1090 terminal width and height @pxref{Screen Size}, and acts as if @kbd{set confirm
1091 off} were in effect (@pxref{Messages/Warnings}).
1093 Batch mode may be useful for running @value{GDBN} as a filter, for
1094 example to download and run a program on another computer; in order to
1095 make this more useful, the message
1098 Program exited normally.
1102 (which is ordinarily issued whenever a program running under
1103 @value{GDBN} control terminates) is not issued when running in batch
1107 @cindex @code{--batch-silent}
1108 Run in batch mode exactly like @samp{-batch}, but totally silently. All
1109 @value{GDBN} output to @code{stdout} is prevented (@code{stderr} is
1110 unaffected). This is much quieter than @samp{-silent} and would be useless
1111 for an interactive session.
1113 This is particularly useful when using targets that give @samp{Loading section}
1114 messages, for example.
1116 Note that targets that give their output via @value{GDBN}, as opposed to
1117 writing directly to @code{stdout}, will also be made silent.
1119 @item -return-child-result
1120 @cindex @code{--return-child-result}
1121 The return code from @value{GDBN} will be the return code from the child
1122 process (the process being debugged), with the following exceptions:
1126 @value{GDBN} exits abnormally. E.g., due to an incorrect argument or an
1127 internal error. In this case the exit code is the same as it would have been
1128 without @samp{-return-child-result}.
1130 The user quits with an explicit value. E.g., @samp{quit 1}.
1132 The child process never runs, or is not allowed to terminate, in which case
1133 the exit code will be -1.
1136 This option is useful in conjunction with @samp{-batch} or @samp{-batch-silent},
1137 when @value{GDBN} is being used as a remote program loader or simulator
1142 @cindex @code{--nowindows}
1144 ``No windows''. If @value{GDBN} comes with a graphical user interface
1145 (GUI) built in, then this option tells @value{GDBN} to only use the command-line
1146 interface. If no GUI is available, this option has no effect.
1150 @cindex @code{--windows}
1152 If @value{GDBN} includes a GUI, then this option requires it to be
1155 @item -cd @var{directory}
1157 Run @value{GDBN} using @var{directory} as its working directory,
1158 instead of the current directory.
1160 @item -data-directory @var{directory}
1161 @cindex @code{--data-directory}
1162 Run @value{GDBN} using @var{directory} as its data directory.
1163 The data directory is where @value{GDBN} searches for its
1164 auxiliary files. @xref{Data Files}.
1168 @cindex @code{--fullname}
1170 @sc{gnu} Emacs sets this option when it runs @value{GDBN} as a
1171 subprocess. It tells @value{GDBN} to output the full file name and line
1172 number in a standard, recognizable fashion each time a stack frame is
1173 displayed (which includes each time your program stops). This
1174 recognizable format looks like two @samp{\032} characters, followed by
1175 the file name, line number and character position separated by colons,
1176 and a newline. The Emacs-to-@value{GDBN} interface program uses the two
1177 @samp{\032} characters as a signal to display the source code for the
1180 @item -annotate @var{level}
1181 @cindex @code{--annotate}
1182 This option sets the @dfn{annotation level} inside @value{GDBN}. Its
1183 effect is identical to using @samp{set annotate @var{level}}
1184 (@pxref{Annotations}). The annotation @var{level} controls how much
1185 information @value{GDBN} prints together with its prompt, values of
1186 expressions, source lines, and other types of output. Level 0 is the
1187 normal, level 1 is for use when @value{GDBN} is run as a subprocess of
1188 @sc{gnu} Emacs, level 3 is the maximum annotation suitable for programs
1189 that control @value{GDBN}, and level 2 has been deprecated.
1191 The annotation mechanism has largely been superseded by @sc{gdb/mi}
1195 @cindex @code{--args}
1196 Change interpretation of command line so that arguments following the
1197 executable file are passed as command line arguments to the inferior.
1198 This option stops option processing.
1200 @item -baud @var{bps}
1202 @cindex @code{--baud}
1204 Set the line speed (baud rate or bits per second) of any serial
1205 interface used by @value{GDBN} for remote debugging.
1207 @item -l @var{timeout}
1209 Set the timeout (in seconds) of any communication used by @value{GDBN}
1210 for remote debugging.
1212 @item -tty @var{device}
1213 @itemx -t @var{device}
1214 @cindex @code{--tty}
1216 Run using @var{device} for your program's standard input and output.
1217 @c FIXME: kingdon thinks there is more to -tty. Investigate.
1219 @c resolve the situation of these eventually
1221 @cindex @code{--tui}
1222 Activate the @dfn{Text User Interface} when starting. The Text User
1223 Interface manages several text windows on the terminal, showing
1224 source, assembly, registers and @value{GDBN} command outputs
1225 (@pxref{TUI, ,@value{GDBN} Text User Interface}). Do not use this
1226 option if you run @value{GDBN} from Emacs (@pxref{Emacs, ,
1227 Using @value{GDBN} under @sc{gnu} Emacs}).
1230 @c @cindex @code{--xdb}
1231 @c Run in XDB compatibility mode, allowing the use of certain XDB commands.
1232 @c For information, see the file @file{xdb_trans.html}, which is usually
1233 @c installed in the directory @code{/opt/langtools/wdb/doc} on HP-UX
1236 @item -interpreter @var{interp}
1237 @cindex @code{--interpreter}
1238 Use the interpreter @var{interp} for interface with the controlling
1239 program or device. This option is meant to be set by programs which
1240 communicate with @value{GDBN} using it as a back end.
1241 @xref{Interpreters, , Command Interpreters}.
1243 @samp{--interpreter=mi} (or @samp{--interpreter=mi2}) causes
1244 @value{GDBN} to use the @dfn{@sc{gdb/mi} interface} (@pxref{GDB/MI, ,
1245 The @sc{gdb/mi} Interface}) included since @value{GDBN} version 6.0. The
1246 previous @sc{gdb/mi} interface, included in @value{GDBN} version 5.3 and
1247 selected with @samp{--interpreter=mi1}, is deprecated. Earlier
1248 @sc{gdb/mi} interfaces are no longer supported.
1251 @cindex @code{--write}
1252 Open the executable and core files for both reading and writing. This
1253 is equivalent to the @samp{set write on} command inside @value{GDBN}
1257 @cindex @code{--statistics}
1258 This option causes @value{GDBN} to print statistics about time and
1259 memory usage after it completes each command and returns to the prompt.
1262 @cindex @code{--version}
1263 This option causes @value{GDBN} to print its version number and
1264 no-warranty blurb, and exit.
1269 @subsection What @value{GDBN} Does During Startup
1270 @cindex @value{GDBN} startup
1272 Here's the description of what @value{GDBN} does during session startup:
1276 Sets up the command interpreter as specified by the command line
1277 (@pxref{Mode Options, interpreter}).
1281 Reads the system-wide @dfn{init file} (if @option{--with-system-gdbinit} was
1282 used when building @value{GDBN}; @pxref{System-wide configuration,
1283 ,System-wide configuration and settings}) and executes all the commands in
1286 @anchor{Home Directory Init File}
1288 Reads the init file (if any) in your home directory@footnote{On
1289 DOS/Windows systems, the home directory is the one pointed to by the
1290 @code{HOME} environment variable.} and executes all the commands in
1293 @anchor{Option -init-eval-command}
1295 Executes commands and command files specified by the @samp{-iex} and
1296 @samp{-ix} options in their specified order. Usually you should use the
1297 @samp{-ex} and @samp{-x} options instead, but this way you can apply
1298 settings before @value{GDBN} init files get executed and before inferior
1302 Processes command line options and operands.
1304 @anchor{Init File in the Current Directory during Startup}
1306 Reads and executes the commands from init file (if any) in the current
1307 working directory as long as @samp{set auto-load local-gdbinit} is set to
1308 @samp{on} (@pxref{Init File in the Current Directory}).
1309 This is only done if the current directory is
1310 different from your home directory. Thus, you can have more than one
1311 init file, one generic in your home directory, and another, specific
1312 to the program you are debugging, in the directory where you invoke
1316 If the command line specified a program to debug, or a process to
1317 attach to, or a core file, @value{GDBN} loads any auto-loaded
1318 scripts provided for the program or for its loaded shared libraries.
1319 @xref{Auto-loading}.
1321 If you wish to disable the auto-loading during startup,
1322 you must do something like the following:
1325 $ gdb -iex "set auto-load python-scripts off" myprogram
1328 Option @samp{-ex} does not work because the auto-loading is then turned
1332 Executes commands and command files specified by the @samp{-ex} and
1333 @samp{-x} options in their specified order. @xref{Command Files}, for
1334 more details about @value{GDBN} command files.
1337 Reads the command history recorded in the @dfn{history file}.
1338 @xref{Command History}, for more details about the command history and the
1339 files where @value{GDBN} records it.
1342 Init files use the same syntax as @dfn{command files} (@pxref{Command
1343 Files}) and are processed by @value{GDBN} in the same way. The init
1344 file in your home directory can set options (such as @samp{set
1345 complaints}) that affect subsequent processing of command line options
1346 and operands. Init files are not executed if you use the @samp{-nx}
1347 option (@pxref{Mode Options, ,Choosing Modes}).
1349 To display the list of init files loaded by gdb at startup, you
1350 can use @kbd{gdb --help}.
1352 @cindex init file name
1353 @cindex @file{.gdbinit}
1354 @cindex @file{gdb.ini}
1355 The @value{GDBN} init files are normally called @file{.gdbinit}.
1356 The DJGPP port of @value{GDBN} uses the name @file{gdb.ini}, due to
1357 the limitations of file names imposed by DOS filesystems. The Windows
1358 port of @value{GDBN} uses the standard name, but if it finds a
1359 @file{gdb.ini} file in your home directory, it warns you about that
1360 and suggests to rename the file to the standard name.
1364 @section Quitting @value{GDBN}
1365 @cindex exiting @value{GDBN}
1366 @cindex leaving @value{GDBN}
1369 @kindex quit @r{[}@var{expression}@r{]}
1370 @kindex q @r{(@code{quit})}
1371 @item quit @r{[}@var{expression}@r{]}
1373 To exit @value{GDBN}, use the @code{quit} command (abbreviated
1374 @code{q}), or type an end-of-file character (usually @kbd{Ctrl-d}). If you
1375 do not supply @var{expression}, @value{GDBN} will terminate normally;
1376 otherwise it will terminate using the result of @var{expression} as the
1381 An interrupt (often @kbd{Ctrl-c}) does not exit from @value{GDBN}, but rather
1382 terminates the action of any @value{GDBN} command that is in progress and
1383 returns to @value{GDBN} command level. It is safe to type the interrupt
1384 character at any time because @value{GDBN} does not allow it to take effect
1385 until a time when it is safe.
1387 If you have been using @value{GDBN} to control an attached process or
1388 device, you can release it with the @code{detach} command
1389 (@pxref{Attach, ,Debugging an Already-running Process}).
1391 @node Shell Commands
1392 @section Shell Commands
1394 If you need to execute occasional shell commands during your
1395 debugging session, there is no need to leave or suspend @value{GDBN}; you can
1396 just use the @code{shell} command.
1401 @cindex shell escape
1402 @item shell @var{command-string}
1403 @itemx !@var{command-string}
1404 Invoke a standard shell to execute @var{command-string}.
1405 Note that no space is needed between @code{!} and @var{command-string}.
1406 If it exists, the environment variable @code{SHELL} determines which
1407 shell to run. Otherwise @value{GDBN} uses the default shell
1408 (@file{/bin/sh} on Unix systems, @file{COMMAND.COM} on MS-DOS, etc.).
1411 The utility @code{make} is often needed in development environments.
1412 You do not have to use the @code{shell} command for this purpose in
1417 @cindex calling make
1418 @item make @var{make-args}
1419 Execute the @code{make} program with the specified
1420 arguments. This is equivalent to @samp{shell make @var{make-args}}.
1423 @node Logging Output
1424 @section Logging Output
1425 @cindex logging @value{GDBN} output
1426 @cindex save @value{GDBN} output to a file
1428 You may want to save the output of @value{GDBN} commands to a file.
1429 There are several commands to control @value{GDBN}'s logging.
1433 @item set logging on
1435 @item set logging off
1437 @cindex logging file name
1438 @item set logging file @var{file}
1439 Change the name of the current logfile. The default logfile is @file{gdb.txt}.
1440 @item set logging overwrite [on|off]
1441 By default, @value{GDBN} will append to the logfile. Set @code{overwrite} if
1442 you want @code{set logging on} to overwrite the logfile instead.
1443 @item set logging redirect [on|off]
1444 By default, @value{GDBN} output will go to both the terminal and the logfile.
1445 Set @code{redirect} if you want output to go only to the log file.
1446 @kindex show logging
1448 Show the current values of the logging settings.
1452 @chapter @value{GDBN} Commands
1454 You can abbreviate a @value{GDBN} command to the first few letters of the command
1455 name, if that abbreviation is unambiguous; and you can repeat certain
1456 @value{GDBN} commands by typing just @key{RET}. You can also use the @key{TAB}
1457 key to get @value{GDBN} to fill out the rest of a word in a command (or to
1458 show you the alternatives available, if there is more than one possibility).
1461 * Command Syntax:: How to give commands to @value{GDBN}
1462 * Completion:: Command completion
1463 * Help:: How to ask @value{GDBN} for help
1466 @node Command Syntax
1467 @section Command Syntax
1469 A @value{GDBN} command is a single line of input. There is no limit on
1470 how long it can be. It starts with a command name, which is followed by
1471 arguments whose meaning depends on the command name. For example, the
1472 command @code{step} accepts an argument which is the number of times to
1473 step, as in @samp{step 5}. You can also use the @code{step} command
1474 with no arguments. Some commands do not allow any arguments.
1476 @cindex abbreviation
1477 @value{GDBN} command names may always be truncated if that abbreviation is
1478 unambiguous. Other possible command abbreviations are listed in the
1479 documentation for individual commands. In some cases, even ambiguous
1480 abbreviations are allowed; for example, @code{s} is specially defined as
1481 equivalent to @code{step} even though there are other commands whose
1482 names start with @code{s}. You can test abbreviations by using them as
1483 arguments to the @code{help} command.
1485 @cindex repeating commands
1486 @kindex RET @r{(repeat last command)}
1487 A blank line as input to @value{GDBN} (typing just @key{RET}) means to
1488 repeat the previous command. Certain commands (for example, @code{run})
1489 will not repeat this way; these are commands whose unintentional
1490 repetition might cause trouble and which you are unlikely to want to
1491 repeat. User-defined commands can disable this feature; see
1492 @ref{Define, dont-repeat}.
1494 The @code{list} and @code{x} commands, when you repeat them with
1495 @key{RET}, construct new arguments rather than repeating
1496 exactly as typed. This permits easy scanning of source or memory.
1498 @value{GDBN} can also use @key{RET} in another way: to partition lengthy
1499 output, in a way similar to the common utility @code{more}
1500 (@pxref{Screen Size,,Screen Size}). Since it is easy to press one
1501 @key{RET} too many in this situation, @value{GDBN} disables command
1502 repetition after any command that generates this sort of display.
1504 @kindex # @r{(a comment)}
1506 Any text from a @kbd{#} to the end of the line is a comment; it does
1507 nothing. This is useful mainly in command files (@pxref{Command
1508 Files,,Command Files}).
1510 @cindex repeating command sequences
1511 @kindex Ctrl-o @r{(operate-and-get-next)}
1512 The @kbd{Ctrl-o} binding is useful for repeating a complex sequence of
1513 commands. This command accepts the current line, like @key{RET}, and
1514 then fetches the next line relative to the current line from the history
1518 @section Command Completion
1521 @cindex word completion
1522 @value{GDBN} can fill in the rest of a word in a command for you, if there is
1523 only one possibility; it can also show you what the valid possibilities
1524 are for the next word in a command, at any time. This works for @value{GDBN}
1525 commands, @value{GDBN} subcommands, and the names of symbols in your program.
1527 Press the @key{TAB} key whenever you want @value{GDBN} to fill out the rest
1528 of a word. If there is only one possibility, @value{GDBN} fills in the
1529 word, and waits for you to finish the command (or press @key{RET} to
1530 enter it). For example, if you type
1532 @c FIXME "@key" does not distinguish its argument sufficiently to permit
1533 @c complete accuracy in these examples; space introduced for clarity.
1534 @c If texinfo enhancements make it unnecessary, it would be nice to
1535 @c replace " @key" by "@key" in the following...
1537 (@value{GDBP}) info bre @key{TAB}
1541 @value{GDBN} fills in the rest of the word @samp{breakpoints}, since that is
1542 the only @code{info} subcommand beginning with @samp{bre}:
1545 (@value{GDBP}) info breakpoints
1549 You can either press @key{RET} at this point, to run the @code{info
1550 breakpoints} command, or backspace and enter something else, if
1551 @samp{breakpoints} does not look like the command you expected. (If you
1552 were sure you wanted @code{info breakpoints} in the first place, you
1553 might as well just type @key{RET} immediately after @samp{info bre},
1554 to exploit command abbreviations rather than command completion).
1556 If there is more than one possibility for the next word when you press
1557 @key{TAB}, @value{GDBN} sounds a bell. You can either supply more
1558 characters and try again, or just press @key{TAB} a second time;
1559 @value{GDBN} displays all the possible completions for that word. For
1560 example, you might want to set a breakpoint on a subroutine whose name
1561 begins with @samp{make_}, but when you type @kbd{b make_@key{TAB}} @value{GDBN}
1562 just sounds the bell. Typing @key{TAB} again displays all the
1563 function names in your program that begin with those characters, for
1567 (@value{GDBP}) b make_ @key{TAB}
1568 @exdent @value{GDBN} sounds bell; press @key{TAB} again, to see:
1569 make_a_section_from_file make_environ
1570 make_abs_section make_function_type
1571 make_blockvector make_pointer_type
1572 make_cleanup make_reference_type
1573 make_command make_symbol_completion_list
1574 (@value{GDBP}) b make_
1578 After displaying the available possibilities, @value{GDBN} copies your
1579 partial input (@samp{b make_} in the example) so you can finish the
1582 If you just want to see the list of alternatives in the first place, you
1583 can press @kbd{M-?} rather than pressing @key{TAB} twice. @kbd{M-?}
1584 means @kbd{@key{META} ?}. You can type this either by holding down a
1585 key designated as the @key{META} shift on your keyboard (if there is
1586 one) while typing @kbd{?}, or as @key{ESC} followed by @kbd{?}.
1588 @cindex quotes in commands
1589 @cindex completion of quoted strings
1590 Sometimes the string you need, while logically a ``word'', may contain
1591 parentheses or other characters that @value{GDBN} normally excludes from
1592 its notion of a word. To permit word completion to work in this
1593 situation, you may enclose words in @code{'} (single quote marks) in
1594 @value{GDBN} commands.
1596 The most likely situation where you might need this is in typing the
1597 name of a C@t{++} function. This is because C@t{++} allows function
1598 overloading (multiple definitions of the same function, distinguished
1599 by argument type). For example, when you want to set a breakpoint you
1600 may need to distinguish whether you mean the version of @code{name}
1601 that takes an @code{int} parameter, @code{name(int)}, or the version
1602 that takes a @code{float} parameter, @code{name(float)}. To use the
1603 word-completion facilities in this situation, type a single quote
1604 @code{'} at the beginning of the function name. This alerts
1605 @value{GDBN} that it may need to consider more information than usual
1606 when you press @key{TAB} or @kbd{M-?} to request word completion:
1609 (@value{GDBP}) b 'bubble( @kbd{M-?}
1610 bubble(double,double) bubble(int,int)
1611 (@value{GDBP}) b 'bubble(
1614 In some cases, @value{GDBN} can tell that completing a name requires using
1615 quotes. When this happens, @value{GDBN} inserts the quote for you (while
1616 completing as much as it can) if you do not type the quote in the first
1620 (@value{GDBP}) b bub @key{TAB}
1621 @exdent @value{GDBN} alters your input line to the following, and rings a bell:
1622 (@value{GDBP}) b 'bubble(
1626 In general, @value{GDBN} can tell that a quote is needed (and inserts it) if
1627 you have not yet started typing the argument list when you ask for
1628 completion on an overloaded symbol.
1630 For more information about overloaded functions, see @ref{C Plus Plus
1631 Expressions, ,C@t{++} Expressions}. You can use the command @code{set
1632 overload-resolution off} to disable overload resolution;
1633 see @ref{Debugging C Plus Plus, ,@value{GDBN} Features for C@t{++}}.
1635 @cindex completion of structure field names
1636 @cindex structure field name completion
1637 @cindex completion of union field names
1638 @cindex union field name completion
1639 When completing in an expression which looks up a field in a
1640 structure, @value{GDBN} also tries@footnote{The completer can be
1641 confused by certain kinds of invalid expressions. Also, it only
1642 examines the static type of the expression, not the dynamic type.} to
1643 limit completions to the field names available in the type of the
1647 (@value{GDBP}) p gdb_stdout.@kbd{M-?}
1648 magic to_fputs to_rewind
1649 to_data to_isatty to_write
1650 to_delete to_put to_write_async_safe
1655 This is because the @code{gdb_stdout} is a variable of the type
1656 @code{struct ui_file} that is defined in @value{GDBN} sources as
1663 ui_file_flush_ftype *to_flush;
1664 ui_file_write_ftype *to_write;
1665 ui_file_write_async_safe_ftype *to_write_async_safe;
1666 ui_file_fputs_ftype *to_fputs;
1667 ui_file_read_ftype *to_read;
1668 ui_file_delete_ftype *to_delete;
1669 ui_file_isatty_ftype *to_isatty;
1670 ui_file_rewind_ftype *to_rewind;
1671 ui_file_put_ftype *to_put;
1678 @section Getting Help
1679 @cindex online documentation
1682 You can always ask @value{GDBN} itself for information on its commands,
1683 using the command @code{help}.
1686 @kindex h @r{(@code{help})}
1689 You can use @code{help} (abbreviated @code{h}) with no arguments to
1690 display a short list of named classes of commands:
1694 List of classes of commands:
1696 aliases -- Aliases of other commands
1697 breakpoints -- Making program stop at certain points
1698 data -- Examining data
1699 files -- Specifying and examining files
1700 internals -- Maintenance commands
1701 obscure -- Obscure features
1702 running -- Running the program
1703 stack -- Examining the stack
1704 status -- Status inquiries
1705 support -- Support facilities
1706 tracepoints -- Tracing of program execution without
1707 stopping the program
1708 user-defined -- User-defined commands
1710 Type "help" followed by a class name for a list of
1711 commands in that class.
1712 Type "help" followed by command name for full
1714 Command name abbreviations are allowed if unambiguous.
1717 @c the above line break eliminates huge line overfull...
1719 @item help @var{class}
1720 Using one of the general help classes as an argument, you can get a
1721 list of the individual commands in that class. For example, here is the
1722 help display for the class @code{status}:
1725 (@value{GDBP}) help status
1730 @c Line break in "show" line falsifies real output, but needed
1731 @c to fit in smallbook page size.
1732 info -- Generic command for showing things
1733 about the program being debugged
1734 show -- Generic command for showing things
1737 Type "help" followed by command name for full
1739 Command name abbreviations are allowed if unambiguous.
1743 @item help @var{command}
1744 With a command name as @code{help} argument, @value{GDBN} displays a
1745 short paragraph on how to use that command.
1748 @item apropos @var{args}
1749 The @code{apropos} command searches through all of the @value{GDBN}
1750 commands, and their documentation, for the regular expression specified in
1751 @var{args}. It prints out all matches found. For example:
1762 alias -- Define a new command that is an alias of an existing command
1763 aliases -- Aliases of other commands
1764 d -- Delete some breakpoints or auto-display expressions
1765 del -- Delete some breakpoints or auto-display expressions
1766 delete -- Delete some breakpoints or auto-display expressions
1771 @item complete @var{args}
1772 The @code{complete @var{args}} command lists all the possible completions
1773 for the beginning of a command. Use @var{args} to specify the beginning of the
1774 command you want completed. For example:
1780 @noindent results in:
1791 @noindent This is intended for use by @sc{gnu} Emacs.
1794 In addition to @code{help}, you can use the @value{GDBN} commands @code{info}
1795 and @code{show} to inquire about the state of your program, or the state
1796 of @value{GDBN} itself. Each command supports many topics of inquiry; this
1797 manual introduces each of them in the appropriate context. The listings
1798 under @code{info} and under @code{show} in the Command, Variable, and
1799 Function Index point to all the sub-commands. @xref{Command and Variable
1805 @kindex i @r{(@code{info})}
1807 This command (abbreviated @code{i}) is for describing the state of your
1808 program. For example, you can show the arguments passed to a function
1809 with @code{info args}, list the registers currently in use with @code{info
1810 registers}, or list the breakpoints you have set with @code{info breakpoints}.
1811 You can get a complete list of the @code{info} sub-commands with
1812 @w{@code{help info}}.
1816 You can assign the result of an expression to an environment variable with
1817 @code{set}. For example, you can set the @value{GDBN} prompt to a $-sign with
1818 @code{set prompt $}.
1822 In contrast to @code{info}, @code{show} is for describing the state of
1823 @value{GDBN} itself.
1824 You can change most of the things you can @code{show}, by using the
1825 related command @code{set}; for example, you can control what number
1826 system is used for displays with @code{set radix}, or simply inquire
1827 which is currently in use with @code{show radix}.
1830 To display all the settable parameters and their current
1831 values, you can use @code{show} with no arguments; you may also use
1832 @code{info set}. Both commands produce the same display.
1833 @c FIXME: "info set" violates the rule that "info" is for state of
1834 @c FIXME...program. Ck w/ GNU: "info set" to be called something else,
1835 @c FIXME...or change desc of rule---eg "state of prog and debugging session"?
1839 Here are three miscellaneous @code{show} subcommands, all of which are
1840 exceptional in lacking corresponding @code{set} commands:
1843 @kindex show version
1844 @cindex @value{GDBN} version number
1846 Show what version of @value{GDBN} is running. You should include this
1847 information in @value{GDBN} bug-reports. If multiple versions of
1848 @value{GDBN} are in use at your site, you may need to determine which
1849 version of @value{GDBN} you are running; as @value{GDBN} evolves, new
1850 commands are introduced, and old ones may wither away. Also, many
1851 system vendors ship variant versions of @value{GDBN}, and there are
1852 variant versions of @value{GDBN} in @sc{gnu}/Linux distributions as well.
1853 The version number is the same as the one announced when you start
1856 @kindex show copying
1857 @kindex info copying
1858 @cindex display @value{GDBN} copyright
1861 Display information about permission for copying @value{GDBN}.
1863 @kindex show warranty
1864 @kindex info warranty
1866 @itemx info warranty
1867 Display the @sc{gnu} ``NO WARRANTY'' statement, or a warranty,
1868 if your version of @value{GDBN} comes with one.
1873 @chapter Running Programs Under @value{GDBN}
1875 When you run a program under @value{GDBN}, you must first generate
1876 debugging information when you compile it.
1878 You may start @value{GDBN} with its arguments, if any, in an environment
1879 of your choice. If you are doing native debugging, you may redirect
1880 your program's input and output, debug an already running process, or
1881 kill a child process.
1884 * Compilation:: Compiling for debugging
1885 * Starting:: Starting your program
1886 * Arguments:: Your program's arguments
1887 * Environment:: Your program's environment
1889 * Working Directory:: Your program's working directory
1890 * Input/Output:: Your program's input and output
1891 * Attach:: Debugging an already-running process
1892 * Kill Process:: Killing the child process
1894 * Inferiors and Programs:: Debugging multiple inferiors and programs
1895 * Threads:: Debugging programs with multiple threads
1896 * Forks:: Debugging forks
1897 * Checkpoint/Restart:: Setting a @emph{bookmark} to return to later
1901 @section Compiling for Debugging
1903 In order to debug a program effectively, you need to generate
1904 debugging information when you compile it. This debugging information
1905 is stored in the object file; it describes the data type of each
1906 variable or function and the correspondence between source line numbers
1907 and addresses in the executable code.
1909 To request debugging information, specify the @samp{-g} option when you run
1912 Programs that are to be shipped to your customers are compiled with
1913 optimizations, using the @samp{-O} compiler option. However, some
1914 compilers are unable to handle the @samp{-g} and @samp{-O} options
1915 together. Using those compilers, you cannot generate optimized
1916 executables containing debugging information.
1918 @value{NGCC}, the @sc{gnu} C/C@t{++} compiler, supports @samp{-g} with or
1919 without @samp{-O}, making it possible to debug optimized code. We
1920 recommend that you @emph{always} use @samp{-g} whenever you compile a
1921 program. You may think your program is correct, but there is no sense
1922 in pushing your luck. For more information, see @ref{Optimized Code}.
1924 Older versions of the @sc{gnu} C compiler permitted a variant option
1925 @w{@samp{-gg}} for debugging information. @value{GDBN} no longer supports this
1926 format; if your @sc{gnu} C compiler has this option, do not use it.
1928 @value{GDBN} knows about preprocessor macros and can show you their
1929 expansion (@pxref{Macros}). Most compilers do not include information
1930 about preprocessor macros in the debugging information if you specify
1931 the @option{-g} flag alone. Version 3.1 and later of @value{NGCC},
1932 the @sc{gnu} C compiler, provides macro information if you are using
1933 the DWARF debugging format, and specify the option @option{-g3}.
1935 @xref{Debugging Options,,Options for Debugging Your Program or GCC,
1936 gcc.info, Using the @sc{gnu} Compiler Collection (GCC)}, for more
1937 information on @value{NGCC} options affecting debug information.
1939 You will have the best debugging experience if you use the latest
1940 version of the DWARF debugging format that your compiler supports.
1941 DWARF is currently the most expressive and best supported debugging
1942 format in @value{GDBN}.
1946 @section Starting your Program
1952 @kindex r @r{(@code{run})}
1955 Use the @code{run} command to start your program under @value{GDBN}.
1956 You must first specify the program name (except on VxWorks) with an
1957 argument to @value{GDBN} (@pxref{Invocation, ,Getting In and Out of
1958 @value{GDBN}}), or by using the @code{file} or @code{exec-file} command
1959 (@pxref{Files, ,Commands to Specify Files}).
1963 If you are running your program in an execution environment that
1964 supports processes, @code{run} creates an inferior process and makes
1965 that process run your program. In some environments without processes,
1966 @code{run} jumps to the start of your program. Other targets,
1967 like @samp{remote}, are always running. If you get an error
1968 message like this one:
1971 The "remote" target does not support "run".
1972 Try "help target" or "continue".
1976 then use @code{continue} to run your program. You may need @code{load}
1977 first (@pxref{load}).
1979 The execution of a program is affected by certain information it
1980 receives from its superior. @value{GDBN} provides ways to specify this
1981 information, which you must do @emph{before} starting your program. (You
1982 can change it after starting your program, but such changes only affect
1983 your program the next time you start it.) This information may be
1984 divided into four categories:
1987 @item The @emph{arguments.}
1988 Specify the arguments to give your program as the arguments of the
1989 @code{run} command. If a shell is available on your target, the shell
1990 is used to pass the arguments, so that you may use normal conventions
1991 (such as wildcard expansion or variable substitution) in describing
1993 In Unix systems, you can control which shell is used with the
1994 @code{SHELL} environment variable.
1995 @xref{Arguments, ,Your Program's Arguments}.
1997 @item The @emph{environment.}
1998 Your program normally inherits its environment from @value{GDBN}, but you can
1999 use the @value{GDBN} commands @code{set environment} and @code{unset
2000 environment} to change parts of the environment that affect
2001 your program. @xref{Environment, ,Your Program's Environment}.
2003 @item The @emph{working directory.}
2004 Your program inherits its working directory from @value{GDBN}. You can set
2005 the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
2006 @xref{Working Directory, ,Your Program's Working Directory}.
2008 @item The @emph{standard input and output.}
2009 Your program normally uses the same device for standard input and
2010 standard output as @value{GDBN} is using. You can redirect input and output
2011 in the @code{run} command line, or you can use the @code{tty} command to
2012 set a different device for your program.
2013 @xref{Input/Output, ,Your Program's Input and Output}.
2016 @emph{Warning:} While input and output redirection work, you cannot use
2017 pipes to pass the output of the program you are debugging to another
2018 program; if you attempt this, @value{GDBN} is likely to wind up debugging the
2022 When you issue the @code{run} command, your program begins to execute
2023 immediately. @xref{Stopping, ,Stopping and Continuing}, for discussion
2024 of how to arrange for your program to stop. Once your program has
2025 stopped, you may call functions in your program, using the @code{print}
2026 or @code{call} commands. @xref{Data, ,Examining Data}.
2028 If the modification time of your symbol file has changed since the last
2029 time @value{GDBN} read its symbols, @value{GDBN} discards its symbol
2030 table, and reads it again. When it does this, @value{GDBN} tries to retain
2031 your current breakpoints.
2036 @cindex run to main procedure
2037 The name of the main procedure can vary from language to language.
2038 With C or C@t{++}, the main procedure name is always @code{main}, but
2039 other languages such as Ada do not require a specific name for their
2040 main procedure. The debugger provides a convenient way to start the
2041 execution of the program and to stop at the beginning of the main
2042 procedure, depending on the language used.
2044 The @samp{start} command does the equivalent of setting a temporary
2045 breakpoint at the beginning of the main procedure and then invoking
2046 the @samp{run} command.
2048 @cindex elaboration phase
2049 Some programs contain an @dfn{elaboration} phase where some startup code is
2050 executed before the main procedure is called. This depends on the
2051 languages used to write your program. In C@t{++}, for instance,
2052 constructors for static and global objects are executed before
2053 @code{main} is called. It is therefore possible that the debugger stops
2054 before reaching the main procedure. However, the temporary breakpoint
2055 will remain to halt execution.
2057 Specify the arguments to give to your program as arguments to the
2058 @samp{start} command. These arguments will be given verbatim to the
2059 underlying @samp{run} command. Note that the same arguments will be
2060 reused if no argument is provided during subsequent calls to
2061 @samp{start} or @samp{run}.
2063 It is sometimes necessary to debug the program during elaboration. In
2064 these cases, using the @code{start} command would stop the execution of
2065 your program too late, as the program would have already completed the
2066 elaboration phase. Under these circumstances, insert breakpoints in your
2067 elaboration code before running your program.
2069 @kindex set exec-wrapper
2070 @item set exec-wrapper @var{wrapper}
2071 @itemx show exec-wrapper
2072 @itemx unset exec-wrapper
2073 When @samp{exec-wrapper} is set, the specified wrapper is used to
2074 launch programs for debugging. @value{GDBN} starts your program
2075 with a shell command of the form @kbd{exec @var{wrapper}
2076 @var{program}}. Quoting is added to @var{program} and its
2077 arguments, but not to @var{wrapper}, so you should add quotes if
2078 appropriate for your shell. The wrapper runs until it executes
2079 your program, and then @value{GDBN} takes control.
2081 You can use any program that eventually calls @code{execve} with
2082 its arguments as a wrapper. Several standard Unix utilities do
2083 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
2084 with @code{exec "$@@"} will also work.
2086 For example, you can use @code{env} to pass an environment variable to
2087 the debugged program, without setting the variable in your shell's
2091 (@value{GDBP}) set exec-wrapper env 'LD_PRELOAD=libtest.so'
2095 This command is available when debugging locally on most targets, excluding
2096 @sc{djgpp}, Cygwin, MS Windows, and QNX Neutrino.
2098 @kindex set disable-randomization
2099 @item set disable-randomization
2100 @itemx set disable-randomization on
2101 This option (enabled by default in @value{GDBN}) will turn off the native
2102 randomization of the virtual address space of the started program. This option
2103 is useful for multiple debugging sessions to make the execution better
2104 reproducible and memory addresses reusable across debugging sessions.
2106 This feature is implemented only on certain targets, including @sc{gnu}/Linux.
2107 On @sc{gnu}/Linux you can get the same behavior using
2110 (@value{GDBP}) set exec-wrapper setarch `uname -m` -R
2113 @item set disable-randomization off
2114 Leave the behavior of the started executable unchanged. Some bugs rear their
2115 ugly heads only when the program is loaded at certain addresses. If your bug
2116 disappears when you run the program under @value{GDBN}, that might be because
2117 @value{GDBN} by default disables the address randomization on platforms, such
2118 as @sc{gnu}/Linux, which do that for stand-alone programs. Use @kbd{set
2119 disable-randomization off} to try to reproduce such elusive bugs.
2121 On targets where it is available, virtual address space randomization
2122 protects the programs against certain kinds of security attacks. In these
2123 cases the attacker needs to know the exact location of a concrete executable
2124 code. Randomizing its location makes it impossible to inject jumps misusing
2125 a code at its expected addresses.
2127 Prelinking shared libraries provides a startup performance advantage but it
2128 makes addresses in these libraries predictable for privileged processes by
2129 having just unprivileged access at the target system. Reading the shared
2130 library binary gives enough information for assembling the malicious code
2131 misusing it. Still even a prelinked shared library can get loaded at a new
2132 random address just requiring the regular relocation process during the
2133 startup. Shared libraries not already prelinked are always loaded at
2134 a randomly chosen address.
2136 Position independent executables (PIE) contain position independent code
2137 similar to the shared libraries and therefore such executables get loaded at
2138 a randomly chosen address upon startup. PIE executables always load even
2139 already prelinked shared libraries at a random address. You can build such
2140 executable using @command{gcc -fPIE -pie}.
2142 Heap (malloc storage), stack and custom mmap areas are always placed randomly
2143 (as long as the randomization is enabled).
2145 @item show disable-randomization
2146 Show the current setting of the explicit disable of the native randomization of
2147 the virtual address space of the started program.
2152 @section Your Program's Arguments
2154 @cindex arguments (to your program)
2155 The arguments to your program can be specified by the arguments of the
2157 They are passed to a shell, which expands wildcard characters and
2158 performs redirection of I/O, and thence to your program. Your
2159 @code{SHELL} environment variable (if it exists) specifies what shell
2160 @value{GDBN} uses. If you do not define @code{SHELL}, @value{GDBN} uses
2161 the default shell (@file{/bin/sh} on Unix).
2163 On non-Unix systems, the program is usually invoked directly by
2164 @value{GDBN}, which emulates I/O redirection via the appropriate system
2165 calls, and the wildcard characters are expanded by the startup code of
2166 the program, not by the shell.
2168 @code{run} with no arguments uses the same arguments used by the previous
2169 @code{run}, or those set by the @code{set args} command.
2174 Specify the arguments to be used the next time your program is run. If
2175 @code{set args} has no arguments, @code{run} executes your program
2176 with no arguments. Once you have run your program with arguments,
2177 using @code{set args} before the next @code{run} is the only way to run
2178 it again without arguments.
2182 Show the arguments to give your program when it is started.
2186 @section Your Program's Environment
2188 @cindex environment (of your program)
2189 The @dfn{environment} consists of a set of environment variables and
2190 their values. Environment variables conventionally record such things as
2191 your user name, your home directory, your terminal type, and your search
2192 path for programs to run. Usually you set up environment variables with
2193 the shell and they are inherited by all the other programs you run. When
2194 debugging, it can be useful to try running your program with a modified
2195 environment without having to start @value{GDBN} over again.
2199 @item path @var{directory}
2200 Add @var{directory} to the front of the @code{PATH} environment variable
2201 (the search path for executables) that will be passed to your program.
2202 The value of @code{PATH} used by @value{GDBN} does not change.
2203 You may specify several directory names, separated by whitespace or by a
2204 system-dependent separator character (@samp{:} on Unix, @samp{;} on
2205 MS-DOS and MS-Windows). If @var{directory} is already in the path, it
2206 is moved to the front, so it is searched sooner.
2208 You can use the string @samp{$cwd} to refer to whatever is the current
2209 working directory at the time @value{GDBN} searches the path. If you
2210 use @samp{.} instead, it refers to the directory where you executed the
2211 @code{path} command. @value{GDBN} replaces @samp{.} in the
2212 @var{directory} argument (with the current path) before adding
2213 @var{directory} to the search path.
2214 @c 'path' is explicitly nonrepeatable, but RMS points out it is silly to
2215 @c document that, since repeating it would be a no-op.
2219 Display the list of search paths for executables (the @code{PATH}
2220 environment variable).
2222 @kindex show environment
2223 @item show environment @r{[}@var{varname}@r{]}
2224 Print the value of environment variable @var{varname} to be given to
2225 your program when it starts. If you do not supply @var{varname},
2226 print the names and values of all environment variables to be given to
2227 your program. You can abbreviate @code{environment} as @code{env}.
2229 @kindex set environment
2230 @item set environment @var{varname} @r{[}=@var{value}@r{]}
2231 Set environment variable @var{varname} to @var{value}. The value
2232 changes for your program only, not for @value{GDBN} itself. @var{value} may
2233 be any string; the values of environment variables are just strings, and
2234 any interpretation is supplied by your program itself. The @var{value}
2235 parameter is optional; if it is eliminated, the variable is set to a
2237 @c "any string" here does not include leading, trailing
2238 @c blanks. Gnu asks: does anyone care?
2240 For example, this command:
2247 tells the debugged program, when subsequently run, that its user is named
2248 @samp{foo}. (The spaces around @samp{=} are used for clarity here; they
2249 are not actually required.)
2251 @kindex unset environment
2252 @item unset environment @var{varname}
2253 Remove variable @var{varname} from the environment to be passed to your
2254 program. This is different from @samp{set env @var{varname} =};
2255 @code{unset environment} removes the variable from the environment,
2256 rather than assigning it an empty value.
2259 @emph{Warning:} On Unix systems, @value{GDBN} runs your program using
2261 by your @code{SHELL} environment variable if it exists (or
2262 @code{/bin/sh} if not). If your @code{SHELL} variable names a shell
2263 that runs an initialization file---such as @file{.cshrc} for C-shell, or
2264 @file{.bashrc} for BASH---any variables you set in that file affect
2265 your program. You may wish to move setting of environment variables to
2266 files that are only run when you sign on, such as @file{.login} or
2269 @node Working Directory
2270 @section Your Program's Working Directory
2272 @cindex working directory (of your program)
2273 Each time you start your program with @code{run}, it inherits its
2274 working directory from the current working directory of @value{GDBN}.
2275 The @value{GDBN} working directory is initially whatever it inherited
2276 from its parent process (typically the shell), but you can specify a new
2277 working directory in @value{GDBN} with the @code{cd} command.
2279 The @value{GDBN} working directory also serves as a default for the commands
2280 that specify files for @value{GDBN} to operate on. @xref{Files, ,Commands to
2285 @cindex change working directory
2286 @item cd @r{[}@var{directory}@r{]}
2287 Set the @value{GDBN} working directory to @var{directory}. If not
2288 given, @var{directory} uses @file{'~'}.
2292 Print the @value{GDBN} working directory.
2295 It is generally impossible to find the current working directory of
2296 the process being debugged (since a program can change its directory
2297 during its run). If you work on a system where @value{GDBN} is
2298 configured with the @file{/proc} support, you can use the @code{info
2299 proc} command (@pxref{SVR4 Process Information}) to find out the
2300 current working directory of the debuggee.
2303 @section Your Program's Input and Output
2308 By default, the program you run under @value{GDBN} does input and output to
2309 the same terminal that @value{GDBN} uses. @value{GDBN} switches the terminal
2310 to its own terminal modes to interact with you, but it records the terminal
2311 modes your program was using and switches back to them when you continue
2312 running your program.
2315 @kindex info terminal
2317 Displays information recorded by @value{GDBN} about the terminal modes your
2321 You can redirect your program's input and/or output using shell
2322 redirection with the @code{run} command. For example,
2329 starts your program, diverting its output to the file @file{outfile}.
2332 @cindex controlling terminal
2333 Another way to specify where your program should do input and output is
2334 with the @code{tty} command. This command accepts a file name as
2335 argument, and causes this file to be the default for future @code{run}
2336 commands. It also resets the controlling terminal for the child
2337 process, for future @code{run} commands. For example,
2344 directs that processes started with subsequent @code{run} commands
2345 default to do input and output on the terminal @file{/dev/ttyb} and have
2346 that as their controlling terminal.
2348 An explicit redirection in @code{run} overrides the @code{tty} command's
2349 effect on the input/output device, but not its effect on the controlling
2352 When you use the @code{tty} command or redirect input in the @code{run}
2353 command, only the input @emph{for your program} is affected. The input
2354 for @value{GDBN} still comes from your terminal. @code{tty} is an alias
2355 for @code{set inferior-tty}.
2357 @cindex inferior tty
2358 @cindex set inferior controlling terminal
2359 You can use the @code{show inferior-tty} command to tell @value{GDBN} to
2360 display the name of the terminal that will be used for future runs of your
2364 @item set inferior-tty /dev/ttyb
2365 @kindex set inferior-tty
2366 Set the tty for the program being debugged to /dev/ttyb.
2368 @item show inferior-tty
2369 @kindex show inferior-tty
2370 Show the current tty for the program being debugged.
2374 @section Debugging an Already-running Process
2379 @item attach @var{process-id}
2380 This command attaches to a running process---one that was started
2381 outside @value{GDBN}. (@code{info files} shows your active
2382 targets.) The command takes as argument a process ID. The usual way to
2383 find out the @var{process-id} of a Unix process is with the @code{ps} utility,
2384 or with the @samp{jobs -l} shell command.
2386 @code{attach} does not repeat if you press @key{RET} a second time after
2387 executing the command.
2390 To use @code{attach}, your program must be running in an environment
2391 which supports processes; for example, @code{attach} does not work for
2392 programs on bare-board targets that lack an operating system. You must
2393 also have permission to send the process a signal.
2395 When you use @code{attach}, the debugger finds the program running in
2396 the process first by looking in the current working directory, then (if
2397 the program is not found) by using the source file search path
2398 (@pxref{Source Path, ,Specifying Source Directories}). You can also use
2399 the @code{file} command to load the program. @xref{Files, ,Commands to
2402 The first thing @value{GDBN} does after arranging to debug the specified
2403 process is to stop it. You can examine and modify an attached process
2404 with all the @value{GDBN} commands that are ordinarily available when
2405 you start processes with @code{run}. You can insert breakpoints; you
2406 can step and continue; you can modify storage. If you would rather the
2407 process continue running, you may use the @code{continue} command after
2408 attaching @value{GDBN} to the process.
2413 When you have finished debugging the attached process, you can use the
2414 @code{detach} command to release it from @value{GDBN} control. Detaching
2415 the process continues its execution. After the @code{detach} command,
2416 that process and @value{GDBN} become completely independent once more, and you
2417 are ready to @code{attach} another process or start one with @code{run}.
2418 @code{detach} does not repeat if you press @key{RET} again after
2419 executing the command.
2422 If you exit @value{GDBN} while you have an attached process, you detach
2423 that process. If you use the @code{run} command, you kill that process.
2424 By default, @value{GDBN} asks for confirmation if you try to do either of these
2425 things; you can control whether or not you need to confirm by using the
2426 @code{set confirm} command (@pxref{Messages/Warnings, ,Optional Warnings and
2430 @section Killing the Child Process
2435 Kill the child process in which your program is running under @value{GDBN}.
2438 This command is useful if you wish to debug a core dump instead of a
2439 running process. @value{GDBN} ignores any core dump file while your program
2442 On some operating systems, a program cannot be executed outside @value{GDBN}
2443 while you have breakpoints set on it inside @value{GDBN}. You can use the
2444 @code{kill} command in this situation to permit running your program
2445 outside the debugger.
2447 The @code{kill} command is also useful if you wish to recompile and
2448 relink your program, since on many systems it is impossible to modify an
2449 executable file while it is running in a process. In this case, when you
2450 next type @code{run}, @value{GDBN} notices that the file has changed, and
2451 reads the symbol table again (while trying to preserve your current
2452 breakpoint settings).
2454 @node Inferiors and Programs
2455 @section Debugging Multiple Inferiors and Programs
2457 @value{GDBN} lets you run and debug multiple programs in a single
2458 session. In addition, @value{GDBN} on some systems may let you run
2459 several programs simultaneously (otherwise you have to exit from one
2460 before starting another). In the most general case, you can have
2461 multiple threads of execution in each of multiple processes, launched
2462 from multiple executables.
2465 @value{GDBN} represents the state of each program execution with an
2466 object called an @dfn{inferior}. An inferior typically corresponds to
2467 a process, but is more general and applies also to targets that do not
2468 have processes. Inferiors may be created before a process runs, and
2469 may be retained after a process exits. Inferiors have unique
2470 identifiers that are different from process ids. Usually each
2471 inferior will also have its own distinct address space, although some
2472 embedded targets may have several inferiors running in different parts
2473 of a single address space. Each inferior may in turn have multiple
2474 threads running in it.
2476 To find out what inferiors exist at any moment, use @w{@code{info
2480 @kindex info inferiors
2481 @item info inferiors
2482 Print a list of all inferiors currently being managed by @value{GDBN}.
2484 @value{GDBN} displays for each inferior (in this order):
2488 the inferior number assigned by @value{GDBN}
2491 the target system's inferior identifier
2494 the name of the executable the inferior is running.
2499 An asterisk @samp{*} preceding the @value{GDBN} inferior number
2500 indicates the current inferior.
2504 @c end table here to get a little more width for example
2507 (@value{GDBP}) info inferiors
2508 Num Description Executable
2509 2 process 2307 hello
2510 * 1 process 3401 goodbye
2513 To switch focus between inferiors, use the @code{inferior} command:
2516 @kindex inferior @var{infno}
2517 @item inferior @var{infno}
2518 Make inferior number @var{infno} the current inferior. The argument
2519 @var{infno} is the inferior number assigned by @value{GDBN}, as shown
2520 in the first field of the @samp{info inferiors} display.
2524 You can get multiple executables into a debugging session via the
2525 @code{add-inferior} and @w{@code{clone-inferior}} commands. On some
2526 systems @value{GDBN} can add inferiors to the debug session
2527 automatically by following calls to @code{fork} and @code{exec}. To
2528 remove inferiors from the debugging session use the
2529 @w{@code{remove-inferiors}} command.
2532 @kindex add-inferior
2533 @item add-inferior [ -copies @var{n} ] [ -exec @var{executable} ]
2534 Adds @var{n} inferiors to be run using @var{executable} as the
2535 executable. @var{n} defaults to 1. If no executable is specified,
2536 the inferiors begins empty, with no program. You can still assign or
2537 change the program assigned to the inferior at any time by using the
2538 @code{file} command with the executable name as its argument.
2540 @kindex clone-inferior
2541 @item clone-inferior [ -copies @var{n} ] [ @var{infno} ]
2542 Adds @var{n} inferiors ready to execute the same program as inferior
2543 @var{infno}. @var{n} defaults to 1. @var{infno} defaults to the
2544 number of the current inferior. This is a convenient command when you
2545 want to run another instance of the inferior you are debugging.
2548 (@value{GDBP}) info inferiors
2549 Num Description Executable
2550 * 1 process 29964 helloworld
2551 (@value{GDBP}) clone-inferior
2554 (@value{GDBP}) info inferiors
2555 Num Description Executable
2557 * 1 process 29964 helloworld
2560 You can now simply switch focus to inferior 2 and run it.
2562 @kindex remove-inferiors
2563 @item remove-inferiors @var{infno}@dots{}
2564 Removes the inferior or inferiors @var{infno}@dots{}. It is not
2565 possible to remove an inferior that is running with this command. For
2566 those, use the @code{kill} or @code{detach} command first.
2570 To quit debugging one of the running inferiors that is not the current
2571 inferior, you can either detach from it by using the @w{@code{detach
2572 inferior}} command (allowing it to run independently), or kill it
2573 using the @w{@code{kill inferiors}} command:
2576 @kindex detach inferiors @var{infno}@dots{}
2577 @item detach inferior @var{infno}@dots{}
2578 Detach from the inferior or inferiors identified by @value{GDBN}
2579 inferior number(s) @var{infno}@dots{}. Note that the inferior's entry
2580 still stays on the list of inferiors shown by @code{info inferiors},
2581 but its Description will show @samp{<null>}.
2583 @kindex kill inferiors @var{infno}@dots{}
2584 @item kill inferiors @var{infno}@dots{}
2585 Kill the inferior or inferiors identified by @value{GDBN} inferior
2586 number(s) @var{infno}@dots{}. Note that the inferior's entry still
2587 stays on the list of inferiors shown by @code{info inferiors}, but its
2588 Description will show @samp{<null>}.
2591 After the successful completion of a command such as @code{detach},
2592 @code{detach inferiors}, @code{kill} or @code{kill inferiors}, or after
2593 a normal process exit, the inferior is still valid and listed with
2594 @code{info inferiors}, ready to be restarted.
2597 To be notified when inferiors are started or exit under @value{GDBN}'s
2598 control use @w{@code{set print inferior-events}}:
2601 @kindex set print inferior-events
2602 @cindex print messages on inferior start and exit
2603 @item set print inferior-events
2604 @itemx set print inferior-events on
2605 @itemx set print inferior-events off
2606 The @code{set print inferior-events} command allows you to enable or
2607 disable printing of messages when @value{GDBN} notices that new
2608 inferiors have started or that inferiors have exited or have been
2609 detached. By default, these messages will not be printed.
2611 @kindex show print inferior-events
2612 @item show print inferior-events
2613 Show whether messages will be printed when @value{GDBN} detects that
2614 inferiors have started, exited or have been detached.
2617 Many commands will work the same with multiple programs as with a
2618 single program: e.g., @code{print myglobal} will simply display the
2619 value of @code{myglobal} in the current inferior.
2622 Occasionaly, when debugging @value{GDBN} itself, it may be useful to
2623 get more info about the relationship of inferiors, programs, address
2624 spaces in a debug session. You can do that with the @w{@code{maint
2625 info program-spaces}} command.
2628 @kindex maint info program-spaces
2629 @item maint info program-spaces
2630 Print a list of all program spaces currently being managed by
2633 @value{GDBN} displays for each program space (in this order):
2637 the program space number assigned by @value{GDBN}
2640 the name of the executable loaded into the program space, with e.g.,
2641 the @code{file} command.
2646 An asterisk @samp{*} preceding the @value{GDBN} program space number
2647 indicates the current program space.
2649 In addition, below each program space line, @value{GDBN} prints extra
2650 information that isn't suitable to display in tabular form. For
2651 example, the list of inferiors bound to the program space.
2654 (@value{GDBP}) maint info program-spaces
2657 Bound inferiors: ID 1 (process 21561)
2661 Here we can see that no inferior is running the program @code{hello},
2662 while @code{process 21561} is running the program @code{goodbye}. On
2663 some targets, it is possible that multiple inferiors are bound to the
2664 same program space. The most common example is that of debugging both
2665 the parent and child processes of a @code{vfork} call. For example,
2668 (@value{GDBP}) maint info program-spaces
2671 Bound inferiors: ID 2 (process 18050), ID 1 (process 18045)
2674 Here, both inferior 2 and inferior 1 are running in the same program
2675 space as a result of inferior 1 having executed a @code{vfork} call.
2679 @section Debugging Programs with Multiple Threads
2681 @cindex threads of execution
2682 @cindex multiple threads
2683 @cindex switching threads
2684 In some operating systems, such as HP-UX and Solaris, a single program
2685 may have more than one @dfn{thread} of execution. The precise semantics
2686 of threads differ from one operating system to another, but in general
2687 the threads of a single program are akin to multiple processes---except
2688 that they share one address space (that is, they can all examine and
2689 modify the same variables). On the other hand, each thread has its own
2690 registers and execution stack, and perhaps private memory.
2692 @value{GDBN} provides these facilities for debugging multi-thread
2696 @item automatic notification of new threads
2697 @item @samp{thread @var{threadno}}, a command to switch among threads
2698 @item @samp{info threads}, a command to inquire about existing threads
2699 @item @samp{thread apply [@var{threadno}] [@var{all}] @var{args}},
2700 a command to apply a command to a list of threads
2701 @item thread-specific breakpoints
2702 @item @samp{set print thread-events}, which controls printing of
2703 messages on thread start and exit.
2704 @item @samp{set libthread-db-search-path @var{path}}, which lets
2705 the user specify which @code{libthread_db} to use if the default choice
2706 isn't compatible with the program.
2710 @emph{Warning:} These facilities are not yet available on every
2711 @value{GDBN} configuration where the operating system supports threads.
2712 If your @value{GDBN} does not support threads, these commands have no
2713 effect. For example, a system without thread support shows no output
2714 from @samp{info threads}, and always rejects the @code{thread} command,
2718 (@value{GDBP}) info threads
2719 (@value{GDBP}) thread 1
2720 Thread ID 1 not known. Use the "info threads" command to
2721 see the IDs of currently known threads.
2723 @c FIXME to implementors: how hard would it be to say "sorry, this GDB
2724 @c doesn't support threads"?
2727 @cindex focus of debugging
2728 @cindex current thread
2729 The @value{GDBN} thread debugging facility allows you to observe all
2730 threads while your program runs---but whenever @value{GDBN} takes
2731 control, one thread in particular is always the focus of debugging.
2732 This thread is called the @dfn{current thread}. Debugging commands show
2733 program information from the perspective of the current thread.
2735 @cindex @code{New} @var{systag} message
2736 @cindex thread identifier (system)
2737 @c FIXME-implementors!! It would be more helpful if the [New...] message
2738 @c included GDB's numeric thread handle, so you could just go to that
2739 @c thread without first checking `info threads'.
2740 Whenever @value{GDBN} detects a new thread in your program, it displays
2741 the target system's identification for the thread with a message in the
2742 form @samp{[New @var{systag}]}. @var{systag} is a thread identifier
2743 whose form varies depending on the particular system. For example, on
2744 @sc{gnu}/Linux, you might see
2747 [New Thread 0x41e02940 (LWP 25582)]
2751 when @value{GDBN} notices a new thread. In contrast, on an SGI system,
2752 the @var{systag} is simply something like @samp{process 368}, with no
2755 @c FIXME!! (1) Does the [New...] message appear even for the very first
2756 @c thread of a program, or does it only appear for the
2757 @c second---i.e.@: when it becomes obvious we have a multithread
2759 @c (2) *Is* there necessarily a first thread always? Or do some
2760 @c multithread systems permit starting a program with multiple
2761 @c threads ab initio?
2763 @cindex thread number
2764 @cindex thread identifier (GDB)
2765 For debugging purposes, @value{GDBN} associates its own thread
2766 number---always a single integer---with each thread in your program.
2769 @kindex info threads
2770 @item info threads @r{[}@var{id}@dots{}@r{]}
2771 Display a summary of all threads currently in your program. Optional
2772 argument @var{id}@dots{} is one or more thread ids separated by spaces, and
2773 means to print information only about the specified thread or threads.
2774 @value{GDBN} displays for each thread (in this order):
2778 the thread number assigned by @value{GDBN}
2781 the target system's thread identifier (@var{systag})
2784 the thread's name, if one is known. A thread can either be named by
2785 the user (see @code{thread name}, below), or, in some cases, by the
2789 the current stack frame summary for that thread
2793 An asterisk @samp{*} to the left of the @value{GDBN} thread number
2794 indicates the current thread.
2798 @c end table here to get a little more width for example
2801 (@value{GDBP}) info threads
2803 3 process 35 thread 27 0x34e5 in sigpause ()
2804 2 process 35 thread 23 0x34e5 in sigpause ()
2805 * 1 process 35 thread 13 main (argc=1, argv=0x7ffffff8)
2809 On Solaris, you can display more information about user threads with a
2810 Solaris-specific command:
2813 @item maint info sol-threads
2814 @kindex maint info sol-threads
2815 @cindex thread info (Solaris)
2816 Display info on Solaris user threads.
2820 @kindex thread @var{threadno}
2821 @item thread @var{threadno}
2822 Make thread number @var{threadno} the current thread. The command
2823 argument @var{threadno} is the internal @value{GDBN} thread number, as
2824 shown in the first field of the @samp{info threads} display.
2825 @value{GDBN} responds by displaying the system identifier of the thread
2826 you selected, and its current stack frame summary:
2829 (@value{GDBP}) thread 2
2830 [Switching to thread 2 (Thread 0xb7fdab70 (LWP 12747))]
2831 #0 some_function (ignore=0x0) at example.c:8
2832 8 printf ("hello\n");
2836 As with the @samp{[New @dots{}]} message, the form of the text after
2837 @samp{Switching to} depends on your system's conventions for identifying
2840 @vindex $_thread@r{, convenience variable}
2841 The debugger convenience variable @samp{$_thread} contains the number
2842 of the current thread. You may find this useful in writing breakpoint
2843 conditional expressions, command scripts, and so forth. See
2844 @xref{Convenience Vars,, Convenience Variables}, for general
2845 information on convenience variables.
2847 @kindex thread apply
2848 @cindex apply command to several threads
2849 @item thread apply [@var{threadno} | all] @var{command}
2850 The @code{thread apply} command allows you to apply the named
2851 @var{command} to one or more threads. Specify the numbers of the
2852 threads that you want affected with the command argument
2853 @var{threadno}. It can be a single thread number, one of the numbers
2854 shown in the first field of the @samp{info threads} display; or it
2855 could be a range of thread numbers, as in @code{2-4}. To apply a
2856 command to all threads, type @kbd{thread apply all @var{command}}.
2859 @cindex name a thread
2860 @item thread name [@var{name}]
2861 This command assigns a name to the current thread. If no argument is
2862 given, any existing user-specified name is removed. The thread name
2863 appears in the @samp{info threads} display.
2865 On some systems, such as @sc{gnu}/Linux, @value{GDBN} is able to
2866 determine the name of the thread as given by the OS. On these
2867 systems, a name specified with @samp{thread name} will override the
2868 system-give name, and removing the user-specified name will cause
2869 @value{GDBN} to once again display the system-specified name.
2872 @cindex search for a thread
2873 @item thread find [@var{regexp}]
2874 Search for and display thread ids whose name or @var{systag}
2875 matches the supplied regular expression.
2877 As well as being the complement to the @samp{thread name} command,
2878 this command also allows you to identify a thread by its target
2879 @var{systag}. For instance, on @sc{gnu}/Linux, the target @var{systag}
2883 (@value{GDBN}) thread find 26688
2884 Thread 4 has target id 'Thread 0x41e02940 (LWP 26688)'
2885 (@value{GDBN}) info thread 4
2887 4 Thread 0x41e02940 (LWP 26688) 0x00000031ca6cd372 in select ()
2890 @kindex set print thread-events
2891 @cindex print messages on thread start and exit
2892 @item set print thread-events
2893 @itemx set print thread-events on
2894 @itemx set print thread-events off
2895 The @code{set print thread-events} command allows you to enable or
2896 disable printing of messages when @value{GDBN} notices that new threads have
2897 started or that threads have exited. By default, these messages will
2898 be printed if detection of these events is supported by the target.
2899 Note that these messages cannot be disabled on all targets.
2901 @kindex show print thread-events
2902 @item show print thread-events
2903 Show whether messages will be printed when @value{GDBN} detects that threads
2904 have started and exited.
2907 @xref{Thread Stops,,Stopping and Starting Multi-thread Programs}, for
2908 more information about how @value{GDBN} behaves when you stop and start
2909 programs with multiple threads.
2911 @xref{Set Watchpoints,,Setting Watchpoints}, for information about
2912 watchpoints in programs with multiple threads.
2914 @anchor{set libthread-db-search-path}
2916 @kindex set libthread-db-search-path
2917 @cindex search path for @code{libthread_db}
2918 @item set libthread-db-search-path @r{[}@var{path}@r{]}
2919 If this variable is set, @var{path} is a colon-separated list of
2920 directories @value{GDBN} will use to search for @code{libthread_db}.
2921 If you omit @var{path}, @samp{libthread-db-search-path} will be reset to
2922 its default value (@code{$sdir:$pdir} on @sc{gnu}/Linux and Solaris systems).
2923 Internally, the default value comes from the @code{LIBTHREAD_DB_SEARCH_PATH}
2926 On @sc{gnu}/Linux and Solaris systems, @value{GDBN} uses a ``helper''
2927 @code{libthread_db} library to obtain information about threads in the
2928 inferior process. @value{GDBN} will use @samp{libthread-db-search-path}
2929 to find @code{libthread_db}. @value{GDBN} also consults first if inferior
2930 specific thread debugging library loading is enabled
2931 by @samp{set auto-load libthread-db} (@pxref{libthread_db.so.1 file}).
2933 A special entry @samp{$sdir} for @samp{libthread-db-search-path}
2934 refers to the default system directories that are
2935 normally searched for loading shared libraries. The @samp{$sdir} entry
2936 is the only kind not needing to be enabled by @samp{set auto-load libthread-db}
2937 (@pxref{libthread_db.so.1 file}).
2939 A special entry @samp{$pdir} for @samp{libthread-db-search-path}
2940 refers to the directory from which @code{libpthread}
2941 was loaded in the inferior process.
2943 For any @code{libthread_db} library @value{GDBN} finds in above directories,
2944 @value{GDBN} attempts to initialize it with the current inferior process.
2945 If this initialization fails (which could happen because of a version
2946 mismatch between @code{libthread_db} and @code{libpthread}), @value{GDBN}
2947 will unload @code{libthread_db}, and continue with the next directory.
2948 If none of @code{libthread_db} libraries initialize successfully,
2949 @value{GDBN} will issue a warning and thread debugging will be disabled.
2951 Setting @code{libthread-db-search-path} is currently implemented
2952 only on some platforms.
2954 @kindex show libthread-db-search-path
2955 @item show libthread-db-search-path
2956 Display current libthread_db search path.
2958 @kindex set debug libthread-db
2959 @kindex show debug libthread-db
2960 @cindex debugging @code{libthread_db}
2961 @item set debug libthread-db
2962 @itemx show debug libthread-db
2963 Turns on or off display of @code{libthread_db}-related events.
2964 Use @code{1} to enable, @code{0} to disable.
2968 @section Debugging Forks
2970 @cindex fork, debugging programs which call
2971 @cindex multiple processes
2972 @cindex processes, multiple
2973 On most systems, @value{GDBN} has no special support for debugging
2974 programs which create additional processes using the @code{fork}
2975 function. When a program forks, @value{GDBN} will continue to debug the
2976 parent process and the child process will run unimpeded. If you have
2977 set a breakpoint in any code which the child then executes, the child
2978 will get a @code{SIGTRAP} signal which (unless it catches the signal)
2979 will cause it to terminate.
2981 However, if you want to debug the child process there is a workaround
2982 which isn't too painful. Put a call to @code{sleep} in the code which
2983 the child process executes after the fork. It may be useful to sleep
2984 only if a certain environment variable is set, or a certain file exists,
2985 so that the delay need not occur when you don't want to run @value{GDBN}
2986 on the child. While the child is sleeping, use the @code{ps} program to
2987 get its process ID. Then tell @value{GDBN} (a new invocation of
2988 @value{GDBN} if you are also debugging the parent process) to attach to
2989 the child process (@pxref{Attach}). From that point on you can debug
2990 the child process just like any other process which you attached to.
2992 On some systems, @value{GDBN} provides support for debugging programs that
2993 create additional processes using the @code{fork} or @code{vfork} functions.
2994 Currently, the only platforms with this feature are HP-UX (11.x and later
2995 only?) and @sc{gnu}/Linux (kernel version 2.5.60 and later).
2997 By default, when a program forks, @value{GDBN} will continue to debug
2998 the parent process and the child process will run unimpeded.
3000 If you want to follow the child process instead of the parent process,
3001 use the command @w{@code{set follow-fork-mode}}.
3004 @kindex set follow-fork-mode
3005 @item set follow-fork-mode @var{mode}
3006 Set the debugger response to a program call of @code{fork} or
3007 @code{vfork}. A call to @code{fork} or @code{vfork} creates a new
3008 process. The @var{mode} argument can be:
3012 The original process is debugged after a fork. The child process runs
3013 unimpeded. This is the default.
3016 The new process is debugged after a fork. The parent process runs
3021 @kindex show follow-fork-mode
3022 @item show follow-fork-mode
3023 Display the current debugger response to a @code{fork} or @code{vfork} call.
3026 @cindex debugging multiple processes
3027 On Linux, if you want to debug both the parent and child processes, use the
3028 command @w{@code{set detach-on-fork}}.
3031 @kindex set detach-on-fork
3032 @item set detach-on-fork @var{mode}
3033 Tells gdb whether to detach one of the processes after a fork, or
3034 retain debugger control over them both.
3038 The child process (or parent process, depending on the value of
3039 @code{follow-fork-mode}) will be detached and allowed to run
3040 independently. This is the default.
3043 Both processes will be held under the control of @value{GDBN}.
3044 One process (child or parent, depending on the value of
3045 @code{follow-fork-mode}) is debugged as usual, while the other
3050 @kindex show detach-on-fork
3051 @item show detach-on-fork
3052 Show whether detach-on-fork mode is on/off.
3055 If you choose to set @samp{detach-on-fork} mode off, then @value{GDBN}
3056 will retain control of all forked processes (including nested forks).
3057 You can list the forked processes under the control of @value{GDBN} by
3058 using the @w{@code{info inferiors}} command, and switch from one fork
3059 to another by using the @code{inferior} command (@pxref{Inferiors and
3060 Programs, ,Debugging Multiple Inferiors and Programs}).
3062 To quit debugging one of the forked processes, you can either detach
3063 from it by using the @w{@code{detach inferiors}} command (allowing it
3064 to run independently), or kill it using the @w{@code{kill inferiors}}
3065 command. @xref{Inferiors and Programs, ,Debugging Multiple Inferiors
3068 If you ask to debug a child process and a @code{vfork} is followed by an
3069 @code{exec}, @value{GDBN} executes the new target up to the first
3070 breakpoint in the new target. If you have a breakpoint set on
3071 @code{main} in your original program, the breakpoint will also be set on
3072 the child process's @code{main}.
3074 On some systems, when a child process is spawned by @code{vfork}, you
3075 cannot debug the child or parent until an @code{exec} call completes.
3077 If you issue a @code{run} command to @value{GDBN} after an @code{exec}
3078 call executes, the new target restarts. To restart the parent
3079 process, use the @code{file} command with the parent executable name
3080 as its argument. By default, after an @code{exec} call executes,
3081 @value{GDBN} discards the symbols of the previous executable image.
3082 You can change this behaviour with the @w{@code{set follow-exec-mode}}
3086 @kindex set follow-exec-mode
3087 @item set follow-exec-mode @var{mode}
3089 Set debugger response to a program call of @code{exec}. An
3090 @code{exec} call replaces the program image of a process.
3092 @code{follow-exec-mode} can be:
3096 @value{GDBN} creates a new inferior and rebinds the process to this
3097 new inferior. The program the process was running before the
3098 @code{exec} call can be restarted afterwards by restarting the
3104 (@value{GDBP}) info inferiors
3106 Id Description Executable
3109 process 12020 is executing new program: prog2
3110 Program exited normally.
3111 (@value{GDBP}) info inferiors
3112 Id Description Executable
3118 @value{GDBN} keeps the process bound to the same inferior. The new
3119 executable image replaces the previous executable loaded in the
3120 inferior. Restarting the inferior after the @code{exec} call, with
3121 e.g., the @code{run} command, restarts the executable the process was
3122 running after the @code{exec} call. This is the default mode.
3127 (@value{GDBP}) info inferiors
3128 Id Description Executable
3131 process 12020 is executing new program: prog2
3132 Program exited normally.
3133 (@value{GDBP}) info inferiors
3134 Id Description Executable
3141 You can use the @code{catch} command to make @value{GDBN} stop whenever
3142 a @code{fork}, @code{vfork}, or @code{exec} call is made. @xref{Set
3143 Catchpoints, ,Setting Catchpoints}.
3145 @node Checkpoint/Restart
3146 @section Setting a @emph{Bookmark} to Return to Later
3151 @cindex snapshot of a process
3152 @cindex rewind program state
3154 On certain operating systems@footnote{Currently, only
3155 @sc{gnu}/Linux.}, @value{GDBN} is able to save a @dfn{snapshot} of a
3156 program's state, called a @dfn{checkpoint}, and come back to it
3159 Returning to a checkpoint effectively undoes everything that has
3160 happened in the program since the @code{checkpoint} was saved. This
3161 includes changes in memory, registers, and even (within some limits)
3162 system state. Effectively, it is like going back in time to the
3163 moment when the checkpoint was saved.
3165 Thus, if you're stepping thru a program and you think you're
3166 getting close to the point where things go wrong, you can save
3167 a checkpoint. Then, if you accidentally go too far and miss
3168 the critical statement, instead of having to restart your program
3169 from the beginning, you can just go back to the checkpoint and
3170 start again from there.
3172 This can be especially useful if it takes a lot of time or
3173 steps to reach the point where you think the bug occurs.
3175 To use the @code{checkpoint}/@code{restart} method of debugging:
3180 Save a snapshot of the debugged program's current execution state.
3181 The @code{checkpoint} command takes no arguments, but each checkpoint
3182 is assigned a small integer id, similar to a breakpoint id.
3184 @kindex info checkpoints
3185 @item info checkpoints
3186 List the checkpoints that have been saved in the current debugging
3187 session. For each checkpoint, the following information will be
3194 @item Source line, or label
3197 @kindex restart @var{checkpoint-id}
3198 @item restart @var{checkpoint-id}
3199 Restore the program state that was saved as checkpoint number
3200 @var{checkpoint-id}. All program variables, registers, stack frames
3201 etc.@: will be returned to the values that they had when the checkpoint
3202 was saved. In essence, gdb will ``wind back the clock'' to the point
3203 in time when the checkpoint was saved.
3205 Note that breakpoints, @value{GDBN} variables, command history etc.
3206 are not affected by restoring a checkpoint. In general, a checkpoint
3207 only restores things that reside in the program being debugged, not in
3210 @kindex delete checkpoint @var{checkpoint-id}
3211 @item delete checkpoint @var{checkpoint-id}
3212 Delete the previously-saved checkpoint identified by @var{checkpoint-id}.
3216 Returning to a previously saved checkpoint will restore the user state
3217 of the program being debugged, plus a significant subset of the system
3218 (OS) state, including file pointers. It won't ``un-write'' data from
3219 a file, but it will rewind the file pointer to the previous location,
3220 so that the previously written data can be overwritten. For files
3221 opened in read mode, the pointer will also be restored so that the
3222 previously read data can be read again.
3224 Of course, characters that have been sent to a printer (or other
3225 external device) cannot be ``snatched back'', and characters received
3226 from eg.@: a serial device can be removed from internal program buffers,
3227 but they cannot be ``pushed back'' into the serial pipeline, ready to
3228 be received again. Similarly, the actual contents of files that have
3229 been changed cannot be restored (at this time).
3231 However, within those constraints, you actually can ``rewind'' your
3232 program to a previously saved point in time, and begin debugging it
3233 again --- and you can change the course of events so as to debug a
3234 different execution path this time.
3236 @cindex checkpoints and process id
3237 Finally, there is one bit of internal program state that will be
3238 different when you return to a checkpoint --- the program's process
3239 id. Each checkpoint will have a unique process id (or @var{pid}),
3240 and each will be different from the program's original @var{pid}.
3241 If your program has saved a local copy of its process id, this could
3242 potentially pose a problem.
3244 @subsection A Non-obvious Benefit of Using Checkpoints
3246 On some systems such as @sc{gnu}/Linux, address space randomization
3247 is performed on new processes for security reasons. This makes it
3248 difficult or impossible to set a breakpoint, or watchpoint, on an
3249 absolute address if you have to restart the program, since the
3250 absolute location of a symbol will change from one execution to the
3253 A checkpoint, however, is an @emph{identical} copy of a process.
3254 Therefore if you create a checkpoint at (eg.@:) the start of main,
3255 and simply return to that checkpoint instead of restarting the
3256 process, you can avoid the effects of address randomization and
3257 your symbols will all stay in the same place.
3260 @chapter Stopping and Continuing
3262 The principal purposes of using a debugger are so that you can stop your
3263 program before it terminates; or so that, if your program runs into
3264 trouble, you can investigate and find out why.
3266 Inside @value{GDBN}, your program may stop for any of several reasons,
3267 such as a signal, a breakpoint, or reaching a new line after a
3268 @value{GDBN} command such as @code{step}. You may then examine and
3269 change variables, set new breakpoints or remove old ones, and then
3270 continue execution. Usually, the messages shown by @value{GDBN} provide
3271 ample explanation of the status of your program---but you can also
3272 explicitly request this information at any time.
3275 @kindex info program
3277 Display information about the status of your program: whether it is
3278 running or not, what process it is, and why it stopped.
3282 * Breakpoints:: Breakpoints, watchpoints, and catchpoints
3283 * Continuing and Stepping:: Resuming execution
3284 * Skipping Over Functions and Files::
3285 Skipping over functions and files
3287 * Thread Stops:: Stopping and starting multi-thread programs
3291 @section Breakpoints, Watchpoints, and Catchpoints
3294 A @dfn{breakpoint} makes your program stop whenever a certain point in
3295 the program is reached. For each breakpoint, you can add conditions to
3296 control in finer detail whether your program stops. You can set
3297 breakpoints with the @code{break} command and its variants (@pxref{Set
3298 Breaks, ,Setting Breakpoints}), to specify the place where your program
3299 should stop by line number, function name or exact address in the
3302 On some systems, you can set breakpoints in shared libraries before
3303 the executable is run. There is a minor limitation on HP-UX systems:
3304 you must wait until the executable is run in order to set breakpoints
3305 in shared library routines that are not called directly by the program
3306 (for example, routines that are arguments in a @code{pthread_create}
3310 @cindex data breakpoints
3311 @cindex memory tracing
3312 @cindex breakpoint on memory address
3313 @cindex breakpoint on variable modification
3314 A @dfn{watchpoint} is a special breakpoint that stops your program
3315 when the value of an expression changes. The expression may be a value
3316 of a variable, or it could involve values of one or more variables
3317 combined by operators, such as @samp{a + b}. This is sometimes called
3318 @dfn{data breakpoints}. You must use a different command to set
3319 watchpoints (@pxref{Set Watchpoints, ,Setting Watchpoints}), but aside
3320 from that, you can manage a watchpoint like any other breakpoint: you
3321 enable, disable, and delete both breakpoints and watchpoints using the
3324 You can arrange to have values from your program displayed automatically
3325 whenever @value{GDBN} stops at a breakpoint. @xref{Auto Display,,
3329 @cindex breakpoint on events
3330 A @dfn{catchpoint} is another special breakpoint that stops your program
3331 when a certain kind of event occurs, such as the throwing of a C@t{++}
3332 exception or the loading of a library. As with watchpoints, you use a
3333 different command to set a catchpoint (@pxref{Set Catchpoints, ,Setting
3334 Catchpoints}), but aside from that, you can manage a catchpoint like any
3335 other breakpoint. (To stop when your program receives a signal, use the
3336 @code{handle} command; see @ref{Signals, ,Signals}.)
3338 @cindex breakpoint numbers
3339 @cindex numbers for breakpoints
3340 @value{GDBN} assigns a number to each breakpoint, watchpoint, or
3341 catchpoint when you create it; these numbers are successive integers
3342 starting with one. In many of the commands for controlling various
3343 features of breakpoints you use the breakpoint number to say which
3344 breakpoint you want to change. Each breakpoint may be @dfn{enabled} or
3345 @dfn{disabled}; if disabled, it has no effect on your program until you
3348 @cindex breakpoint ranges
3349 @cindex ranges of breakpoints
3350 Some @value{GDBN} commands accept a range of breakpoints on which to
3351 operate. A breakpoint range is either a single breakpoint number, like
3352 @samp{5}, or two such numbers, in increasing order, separated by a
3353 hyphen, like @samp{5-7}. When a breakpoint range is given to a command,
3354 all breakpoints in that range are operated on.
3357 * Set Breaks:: Setting breakpoints
3358 * Set Watchpoints:: Setting watchpoints
3359 * Set Catchpoints:: Setting catchpoints
3360 * Delete Breaks:: Deleting breakpoints
3361 * Disabling:: Disabling breakpoints
3362 * Conditions:: Break conditions
3363 * Break Commands:: Breakpoint command lists
3364 * Dynamic Printf:: Dynamic printf
3365 * Save Breakpoints:: How to save breakpoints in a file
3366 * Static Probe Points:: Listing static probe points
3367 * Error in Breakpoints:: ``Cannot insert breakpoints''
3368 * Breakpoint-related Warnings:: ``Breakpoint address adjusted...''
3372 @subsection Setting Breakpoints
3374 @c FIXME LMB what does GDB do if no code on line of breakpt?
3375 @c consider in particular declaration with/without initialization.
3377 @c FIXME 2 is there stuff on this already? break at fun start, already init?
3380 @kindex b @r{(@code{break})}
3381 @vindex $bpnum@r{, convenience variable}
3382 @cindex latest breakpoint
3383 Breakpoints are set with the @code{break} command (abbreviated
3384 @code{b}). The debugger convenience variable @samp{$bpnum} records the
3385 number of the breakpoint you've set most recently; see @ref{Convenience
3386 Vars,, Convenience Variables}, for a discussion of what you can do with
3387 convenience variables.
3390 @item break @var{location}
3391 Set a breakpoint at the given @var{location}, which can specify a
3392 function name, a line number, or an address of an instruction.
3393 (@xref{Specify Location}, for a list of all the possible ways to
3394 specify a @var{location}.) The breakpoint will stop your program just
3395 before it executes any of the code in the specified @var{location}.
3397 When using source languages that permit overloading of symbols, such as
3398 C@t{++}, a function name may refer to more than one possible place to break.
3399 @xref{Ambiguous Expressions,,Ambiguous Expressions}, for a discussion of
3402 It is also possible to insert a breakpoint that will stop the program
3403 only if a specific thread (@pxref{Thread-Specific Breakpoints})
3404 or a specific task (@pxref{Ada Tasks}) hits that breakpoint.
3407 When called without any arguments, @code{break} sets a breakpoint at
3408 the next instruction to be executed in the selected stack frame
3409 (@pxref{Stack, ,Examining the Stack}). In any selected frame but the
3410 innermost, this makes your program stop as soon as control
3411 returns to that frame. This is similar to the effect of a
3412 @code{finish} command in the frame inside the selected frame---except
3413 that @code{finish} does not leave an active breakpoint. If you use
3414 @code{break} without an argument in the innermost frame, @value{GDBN} stops
3415 the next time it reaches the current location; this may be useful
3418 @value{GDBN} normally ignores breakpoints when it resumes execution, until at
3419 least one instruction has been executed. If it did not do this, you
3420 would be unable to proceed past a breakpoint without first disabling the
3421 breakpoint. This rule applies whether or not the breakpoint already
3422 existed when your program stopped.
3424 @item break @dots{} if @var{cond}
3425 Set a breakpoint with condition @var{cond}; evaluate the expression
3426 @var{cond} each time the breakpoint is reached, and stop only if the
3427 value is nonzero---that is, if @var{cond} evaluates as true.
3428 @samp{@dots{}} stands for one of the possible arguments described
3429 above (or no argument) specifying where to break. @xref{Conditions,
3430 ,Break Conditions}, for more information on breakpoint conditions.
3433 @item tbreak @var{args}
3434 Set a breakpoint enabled only for one stop. @var{args} are the
3435 same as for the @code{break} command, and the breakpoint is set in the same
3436 way, but the breakpoint is automatically deleted after the first time your
3437 program stops there. @xref{Disabling, ,Disabling Breakpoints}.
3440 @cindex hardware breakpoints
3441 @item hbreak @var{args}
3442 Set a hardware-assisted breakpoint. @var{args} are the same as for the
3443 @code{break} command and the breakpoint is set in the same way, but the
3444 breakpoint requires hardware support and some target hardware may not
3445 have this support. The main purpose of this is EPROM/ROM code
3446 debugging, so you can set a breakpoint at an instruction without
3447 changing the instruction. This can be used with the new trap-generation
3448 provided by SPARClite DSU and most x86-based targets. These targets
3449 will generate traps when a program accesses some data or instruction
3450 address that is assigned to the debug registers. However the hardware
3451 breakpoint registers can take a limited number of breakpoints. For
3452 example, on the DSU, only two data breakpoints can be set at a time, and
3453 @value{GDBN} will reject this command if more than two are used. Delete
3454 or disable unused hardware breakpoints before setting new ones
3455 (@pxref{Disabling, ,Disabling Breakpoints}).
3456 @xref{Conditions, ,Break Conditions}.
3457 For remote targets, you can restrict the number of hardware
3458 breakpoints @value{GDBN} will use, see @ref{set remote
3459 hardware-breakpoint-limit}.
3462 @item thbreak @var{args}
3463 Set a hardware-assisted breakpoint enabled only for one stop. @var{args}
3464 are the same as for the @code{hbreak} command and the breakpoint is set in
3465 the same way. However, like the @code{tbreak} command,
3466 the breakpoint is automatically deleted after the
3467 first time your program stops there. Also, like the @code{hbreak}
3468 command, the breakpoint requires hardware support and some target hardware
3469 may not have this support. @xref{Disabling, ,Disabling Breakpoints}.
3470 See also @ref{Conditions, ,Break Conditions}.
3473 @cindex regular expression
3474 @cindex breakpoints at functions matching a regexp
3475 @cindex set breakpoints in many functions
3476 @item rbreak @var{regex}
3477 Set breakpoints on all functions matching the regular expression
3478 @var{regex}. This command sets an unconditional breakpoint on all
3479 matches, printing a list of all breakpoints it set. Once these
3480 breakpoints are set, they are treated just like the breakpoints set with
3481 the @code{break} command. You can delete them, disable them, or make
3482 them conditional the same way as any other breakpoint.
3484 The syntax of the regular expression is the standard one used with tools
3485 like @file{grep}. Note that this is different from the syntax used by
3486 shells, so for instance @code{foo*} matches all functions that include
3487 an @code{fo} followed by zero or more @code{o}s. There is an implicit
3488 @code{.*} leading and trailing the regular expression you supply, so to
3489 match only functions that begin with @code{foo}, use @code{^foo}.
3491 @cindex non-member C@t{++} functions, set breakpoint in
3492 When debugging C@t{++} programs, @code{rbreak} is useful for setting
3493 breakpoints on overloaded functions that are not members of any special
3496 @cindex set breakpoints on all functions
3497 The @code{rbreak} command can be used to set breakpoints in
3498 @strong{all} the functions in a program, like this:
3501 (@value{GDBP}) rbreak .
3504 @item rbreak @var{file}:@var{regex}
3505 If @code{rbreak} is called with a filename qualification, it limits
3506 the search for functions matching the given regular expression to the
3507 specified @var{file}. This can be used, for example, to set breakpoints on
3508 every function in a given file:
3511 (@value{GDBP}) rbreak file.c:.
3514 The colon separating the filename qualifier from the regex may
3515 optionally be surrounded by spaces.
3517 @kindex info breakpoints
3518 @cindex @code{$_} and @code{info breakpoints}
3519 @item info breakpoints @r{[}@var{n}@dots{}@r{]}
3520 @itemx info break @r{[}@var{n}@dots{}@r{]}
3521 Print a table of all breakpoints, watchpoints, and catchpoints set and
3522 not deleted. Optional argument @var{n} means print information only
3523 about the specified breakpoint(s) (or watchpoint(s) or catchpoint(s)).
3524 For each breakpoint, following columns are printed:
3527 @item Breakpoint Numbers
3529 Breakpoint, watchpoint, or catchpoint.
3531 Whether the breakpoint is marked to be disabled or deleted when hit.
3532 @item Enabled or Disabled
3533 Enabled breakpoints are marked with @samp{y}. @samp{n} marks breakpoints
3534 that are not enabled.
3536 Where the breakpoint is in your program, as a memory address. For a
3537 pending breakpoint whose address is not yet known, this field will
3538 contain @samp{<PENDING>}. Such breakpoint won't fire until a shared
3539 library that has the symbol or line referred by breakpoint is loaded.
3540 See below for details. A breakpoint with several locations will
3541 have @samp{<MULTIPLE>} in this field---see below for details.
3543 Where the breakpoint is in the source for your program, as a file and
3544 line number. For a pending breakpoint, the original string passed to
3545 the breakpoint command will be listed as it cannot be resolved until
3546 the appropriate shared library is loaded in the future.
3550 If a breakpoint is conditional, there are two evaluation modes: ``host'' and
3551 ``target''. If mode is ``host'', breakpoint condition evaluation is done by
3552 @value{GDBN} on the host's side. If it is ``target'', then the condition
3553 is evaluated by the target. The @code{info break} command shows
3554 the condition on the line following the affected breakpoint, together with
3555 its condition evaluation mode in between parentheses.
3557 Breakpoint commands, if any, are listed after that. A pending breakpoint is
3558 allowed to have a condition specified for it. The condition is not parsed for
3559 validity until a shared library is loaded that allows the pending
3560 breakpoint to resolve to a valid location.
3563 @code{info break} with a breakpoint
3564 number @var{n} as argument lists only that breakpoint. The
3565 convenience variable @code{$_} and the default examining-address for
3566 the @code{x} command are set to the address of the last breakpoint
3567 listed (@pxref{Memory, ,Examining Memory}).
3570 @code{info break} displays a count of the number of times the breakpoint
3571 has been hit. This is especially useful in conjunction with the
3572 @code{ignore} command. You can ignore a large number of breakpoint
3573 hits, look at the breakpoint info to see how many times the breakpoint
3574 was hit, and then run again, ignoring one less than that number. This
3575 will get you quickly to the last hit of that breakpoint.
3578 For a breakpoints with an enable count (xref) greater than 1,
3579 @code{info break} also displays that count.
3583 @value{GDBN} allows you to set any number of breakpoints at the same place in
3584 your program. There is nothing silly or meaningless about this. When
3585 the breakpoints are conditional, this is even useful
3586 (@pxref{Conditions, ,Break Conditions}).
3588 @cindex multiple locations, breakpoints
3589 @cindex breakpoints, multiple locations
3590 It is possible that a breakpoint corresponds to several locations
3591 in your program. Examples of this situation are:
3595 Multiple functions in the program may have the same name.
3598 For a C@t{++} constructor, the @value{NGCC} compiler generates several
3599 instances of the function body, used in different cases.
3602 For a C@t{++} template function, a given line in the function can
3603 correspond to any number of instantiations.
3606 For an inlined function, a given source line can correspond to
3607 several places where that function is inlined.
3610 In all those cases, @value{GDBN} will insert a breakpoint at all
3611 the relevant locations.
3613 A breakpoint with multiple locations is displayed in the breakpoint
3614 table using several rows---one header row, followed by one row for
3615 each breakpoint location. The header row has @samp{<MULTIPLE>} in the
3616 address column. The rows for individual locations contain the actual
3617 addresses for locations, and show the functions to which those
3618 locations belong. The number column for a location is of the form
3619 @var{breakpoint-number}.@var{location-number}.
3624 Num Type Disp Enb Address What
3625 1 breakpoint keep y <MULTIPLE>
3627 breakpoint already hit 1 time
3628 1.1 y 0x080486a2 in void foo<int>() at t.cc:8
3629 1.2 y 0x080486ca in void foo<double>() at t.cc:8
3632 Each location can be individually enabled or disabled by passing
3633 @var{breakpoint-number}.@var{location-number} as argument to the
3634 @code{enable} and @code{disable} commands. Note that you cannot
3635 delete the individual locations from the list, you can only delete the
3636 entire list of locations that belong to their parent breakpoint (with
3637 the @kbd{delete @var{num}} command, where @var{num} is the number of
3638 the parent breakpoint, 1 in the above example). Disabling or enabling
3639 the parent breakpoint (@pxref{Disabling}) affects all of the locations
3640 that belong to that breakpoint.
3642 @cindex pending breakpoints
3643 It's quite common to have a breakpoint inside a shared library.
3644 Shared libraries can be loaded and unloaded explicitly,
3645 and possibly repeatedly, as the program is executed. To support
3646 this use case, @value{GDBN} updates breakpoint locations whenever
3647 any shared library is loaded or unloaded. Typically, you would
3648 set a breakpoint in a shared library at the beginning of your
3649 debugging session, when the library is not loaded, and when the
3650 symbols from the library are not available. When you try to set
3651 breakpoint, @value{GDBN} will ask you if you want to set
3652 a so called @dfn{pending breakpoint}---breakpoint whose address
3653 is not yet resolved.
3655 After the program is run, whenever a new shared library is loaded,
3656 @value{GDBN} reevaluates all the breakpoints. When a newly loaded
3657 shared library contains the symbol or line referred to by some
3658 pending breakpoint, that breakpoint is resolved and becomes an
3659 ordinary breakpoint. When a library is unloaded, all breakpoints
3660 that refer to its symbols or source lines become pending again.
3662 This logic works for breakpoints with multiple locations, too. For
3663 example, if you have a breakpoint in a C@t{++} template function, and
3664 a newly loaded shared library has an instantiation of that template,
3665 a new location is added to the list of locations for the breakpoint.
3667 Except for having unresolved address, pending breakpoints do not
3668 differ from regular breakpoints. You can set conditions or commands,
3669 enable and disable them and perform other breakpoint operations.
3671 @value{GDBN} provides some additional commands for controlling what
3672 happens when the @samp{break} command cannot resolve breakpoint
3673 address specification to an address:
3675 @kindex set breakpoint pending
3676 @kindex show breakpoint pending
3678 @item set breakpoint pending auto
3679 This is the default behavior. When @value{GDBN} cannot find the breakpoint
3680 location, it queries you whether a pending breakpoint should be created.
3682 @item set breakpoint pending on
3683 This indicates that an unrecognized breakpoint location should automatically
3684 result in a pending breakpoint being created.
3686 @item set breakpoint pending off
3687 This indicates that pending breakpoints are not to be created. Any
3688 unrecognized breakpoint location results in an error. This setting does
3689 not affect any pending breakpoints previously created.
3691 @item show breakpoint pending
3692 Show the current behavior setting for creating pending breakpoints.
3695 The settings above only affect the @code{break} command and its
3696 variants. Once breakpoint is set, it will be automatically updated
3697 as shared libraries are loaded and unloaded.
3699 @cindex automatic hardware breakpoints
3700 For some targets, @value{GDBN} can automatically decide if hardware or
3701 software breakpoints should be used, depending on whether the
3702 breakpoint address is read-only or read-write. This applies to
3703 breakpoints set with the @code{break} command as well as to internal
3704 breakpoints set by commands like @code{next} and @code{finish}. For
3705 breakpoints set with @code{hbreak}, @value{GDBN} will always use hardware
3708 You can control this automatic behaviour with the following commands::
3710 @kindex set breakpoint auto-hw
3711 @kindex show breakpoint auto-hw
3713 @item set breakpoint auto-hw on
3714 This is the default behavior. When @value{GDBN} sets a breakpoint, it
3715 will try to use the target memory map to decide if software or hardware
3716 breakpoint must be used.
3718 @item set breakpoint auto-hw off
3719 This indicates @value{GDBN} should not automatically select breakpoint
3720 type. If the target provides a memory map, @value{GDBN} will warn when
3721 trying to set software breakpoint at a read-only address.
3724 @value{GDBN} normally implements breakpoints by replacing the program code
3725 at the breakpoint address with a special instruction, which, when
3726 executed, given control to the debugger. By default, the program
3727 code is so modified only when the program is resumed. As soon as
3728 the program stops, @value{GDBN} restores the original instructions. This
3729 behaviour guards against leaving breakpoints inserted in the
3730 target should gdb abrubptly disconnect. However, with slow remote
3731 targets, inserting and removing breakpoint can reduce the performance.
3732 This behavior can be controlled with the following commands::
3734 @kindex set breakpoint always-inserted
3735 @kindex show breakpoint always-inserted
3737 @item set breakpoint always-inserted off
3738 All breakpoints, including newly added by the user, are inserted in
3739 the target only when the target is resumed. All breakpoints are
3740 removed from the target when it stops.
3742 @item set breakpoint always-inserted on
3743 Causes all breakpoints to be inserted in the target at all times. If
3744 the user adds a new breakpoint, or changes an existing breakpoint, the
3745 breakpoints in the target are updated immediately. A breakpoint is
3746 removed from the target only when breakpoint itself is removed.
3748 @cindex non-stop mode, and @code{breakpoint always-inserted}
3749 @item set breakpoint always-inserted auto
3750 This is the default mode. If @value{GDBN} is controlling the inferior
3751 in non-stop mode (@pxref{Non-Stop Mode}), gdb behaves as if
3752 @code{breakpoint always-inserted} mode is on. If @value{GDBN} is
3753 controlling the inferior in all-stop mode, @value{GDBN} behaves as if
3754 @code{breakpoint always-inserted} mode is off.
3757 @value{GDBN} handles conditional breakpoints by evaluating these conditions
3758 when a breakpoint breaks. If the condition is true, then the process being
3759 debugged stops, otherwise the process is resumed.
3761 If the target supports evaluating conditions on its end, @value{GDBN} may
3762 download the breakpoint, together with its conditions, to it.
3764 This feature can be controlled via the following commands:
3766 @kindex set breakpoint condition-evaluation
3767 @kindex show breakpoint condition-evaluation
3769 @item set breakpoint condition-evaluation host
3770 This option commands @value{GDBN} to evaluate the breakpoint
3771 conditions on the host's side. Unconditional breakpoints are sent to
3772 the target which in turn receives the triggers and reports them back to GDB
3773 for condition evaluation. This is the standard evaluation mode.
3775 @item set breakpoint condition-evaluation target
3776 This option commands @value{GDBN} to download breakpoint conditions
3777 to the target at the moment of their insertion. The target
3778 is responsible for evaluating the conditional expression and reporting
3779 breakpoint stop events back to @value{GDBN} whenever the condition
3780 is true. Due to limitations of target-side evaluation, some conditions
3781 cannot be evaluated there, e.g., conditions that depend on local data
3782 that is only known to the host. Examples include
3783 conditional expressions involving convenience variables, complex types
3784 that cannot be handled by the agent expression parser and expressions
3785 that are too long to be sent over to the target, specially when the
3786 target is a remote system. In these cases, the conditions will be
3787 evaluated by @value{GDBN}.
3789 @item set breakpoint condition-evaluation auto
3790 This is the default mode. If the target supports evaluating breakpoint
3791 conditions on its end, @value{GDBN} will download breakpoint conditions to
3792 the target (limitations mentioned previously apply). If the target does
3793 not support breakpoint condition evaluation, then @value{GDBN} will fallback
3794 to evaluating all these conditions on the host's side.
3798 @cindex negative breakpoint numbers
3799 @cindex internal @value{GDBN} breakpoints
3800 @value{GDBN} itself sometimes sets breakpoints in your program for
3801 special purposes, such as proper handling of @code{longjmp} (in C
3802 programs). These internal breakpoints are assigned negative numbers,
3803 starting with @code{-1}; @samp{info breakpoints} does not display them.
3804 You can see these breakpoints with the @value{GDBN} maintenance command
3805 @samp{maint info breakpoints} (@pxref{maint info breakpoints}).
3808 @node Set Watchpoints
3809 @subsection Setting Watchpoints
3811 @cindex setting watchpoints
3812 You can use a watchpoint to stop execution whenever the value of an
3813 expression changes, without having to predict a particular place where
3814 this may happen. (This is sometimes called a @dfn{data breakpoint}.)
3815 The expression may be as simple as the value of a single variable, or
3816 as complex as many variables combined by operators. Examples include:
3820 A reference to the value of a single variable.
3823 An address cast to an appropriate data type. For example,
3824 @samp{*(int *)0x12345678} will watch a 4-byte region at the specified
3825 address (assuming an @code{int} occupies 4 bytes).
3828 An arbitrarily complex expression, such as @samp{a*b + c/d}. The
3829 expression can use any operators valid in the program's native
3830 language (@pxref{Languages}).
3833 You can set a watchpoint on an expression even if the expression can
3834 not be evaluated yet. For instance, you can set a watchpoint on
3835 @samp{*global_ptr} before @samp{global_ptr} is initialized.
3836 @value{GDBN} will stop when your program sets @samp{global_ptr} and
3837 the expression produces a valid value. If the expression becomes
3838 valid in some other way than changing a variable (e.g.@: if the memory
3839 pointed to by @samp{*global_ptr} becomes readable as the result of a
3840 @code{malloc} call), @value{GDBN} may not stop until the next time
3841 the expression changes.
3843 @cindex software watchpoints
3844 @cindex hardware watchpoints
3845 Depending on your system, watchpoints may be implemented in software or
3846 hardware. @value{GDBN} does software watchpointing by single-stepping your
3847 program and testing the variable's value each time, which is hundreds of
3848 times slower than normal execution. (But this may still be worth it, to
3849 catch errors where you have no clue what part of your program is the
3852 On some systems, such as HP-UX, PowerPC, @sc{gnu}/Linux and most other
3853 x86-based targets, @value{GDBN} includes support for hardware
3854 watchpoints, which do not slow down the running of your program.
3858 @item watch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3859 Set a watchpoint for an expression. @value{GDBN} will break when the
3860 expression @var{expr} is written into by the program and its value
3861 changes. The simplest (and the most popular) use of this command is
3862 to watch the value of a single variable:
3865 (@value{GDBP}) watch foo
3868 If the command includes a @code{@r{[}thread @var{threadnum}@r{]}}
3869 argument, @value{GDBN} breaks only when the thread identified by
3870 @var{threadnum} changes the value of @var{expr}. If any other threads
3871 change the value of @var{expr}, @value{GDBN} will not break. Note
3872 that watchpoints restricted to a single thread in this way only work
3873 with Hardware Watchpoints.
3875 Ordinarily a watchpoint respects the scope of variables in @var{expr}
3876 (see below). The @code{-location} argument tells @value{GDBN} to
3877 instead watch the memory referred to by @var{expr}. In this case,
3878 @value{GDBN} will evaluate @var{expr}, take the address of the result,
3879 and watch the memory at that address. The type of the result is used
3880 to determine the size of the watched memory. If the expression's
3881 result does not have an address, then @value{GDBN} will print an
3884 The @code{@r{[}mask @var{maskvalue}@r{]}} argument allows creation
3885 of masked watchpoints, if the current architecture supports this
3886 feature (e.g., PowerPC Embedded architecture, see @ref{PowerPC
3887 Embedded}.) A @dfn{masked watchpoint} specifies a mask in addition
3888 to an address to watch. The mask specifies that some bits of an address
3889 (the bits which are reset in the mask) should be ignored when matching
3890 the address accessed by the inferior against the watchpoint address.
3891 Thus, a masked watchpoint watches many addresses simultaneously---those
3892 addresses whose unmasked bits are identical to the unmasked bits in the
3893 watchpoint address. The @code{mask} argument implies @code{-location}.
3897 (@value{GDBP}) watch foo mask 0xffff00ff
3898 (@value{GDBP}) watch *0xdeadbeef mask 0xffffff00
3902 @item rwatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3903 Set a watchpoint that will break when the value of @var{expr} is read
3907 @item awatch @r{[}-l@r{|}-location@r{]} @var{expr} @r{[}thread @var{threadnum}@r{]} @r{[}mask @var{maskvalue}@r{]}
3908 Set a watchpoint that will break when @var{expr} is either read from
3909 or written into by the program.
3911 @kindex info watchpoints @r{[}@var{n}@dots{}@r{]}
3912 @item info watchpoints @r{[}@var{n}@dots{}@r{]}
3913 This command prints a list of watchpoints, using the same format as
3914 @code{info break} (@pxref{Set Breaks}).
3917 If you watch for a change in a numerically entered address you need to
3918 dereference it, as the address itself is just a constant number which will
3919 never change. @value{GDBN} refuses to create a watchpoint that watches
3920 a never-changing value:
3923 (@value{GDBP}) watch 0x600850
3924 Cannot watch constant value 0x600850.
3925 (@value{GDBP}) watch *(int *) 0x600850
3926 Watchpoint 1: *(int *) 6293584
3929 @value{GDBN} sets a @dfn{hardware watchpoint} if possible. Hardware
3930 watchpoints execute very quickly, and the debugger reports a change in
3931 value at the exact instruction where the change occurs. If @value{GDBN}
3932 cannot set a hardware watchpoint, it sets a software watchpoint, which
3933 executes more slowly and reports the change in value at the next
3934 @emph{statement}, not the instruction, after the change occurs.
3936 @cindex use only software watchpoints
3937 You can force @value{GDBN} to use only software watchpoints with the
3938 @kbd{set can-use-hw-watchpoints 0} command. With this variable set to
3939 zero, @value{GDBN} will never try to use hardware watchpoints, even if
3940 the underlying system supports them. (Note that hardware-assisted
3941 watchpoints that were set @emph{before} setting
3942 @code{can-use-hw-watchpoints} to zero will still use the hardware
3943 mechanism of watching expression values.)
3946 @item set can-use-hw-watchpoints
3947 @kindex set can-use-hw-watchpoints
3948 Set whether or not to use hardware watchpoints.
3950 @item show can-use-hw-watchpoints
3951 @kindex show can-use-hw-watchpoints
3952 Show the current mode of using hardware watchpoints.
3955 For remote targets, you can restrict the number of hardware
3956 watchpoints @value{GDBN} will use, see @ref{set remote
3957 hardware-breakpoint-limit}.
3959 When you issue the @code{watch} command, @value{GDBN} reports
3962 Hardware watchpoint @var{num}: @var{expr}
3966 if it was able to set a hardware watchpoint.
3968 Currently, the @code{awatch} and @code{rwatch} commands can only set
3969 hardware watchpoints, because accesses to data that don't change the
3970 value of the watched expression cannot be detected without examining
3971 every instruction as it is being executed, and @value{GDBN} does not do
3972 that currently. If @value{GDBN} finds that it is unable to set a
3973 hardware breakpoint with the @code{awatch} or @code{rwatch} command, it
3974 will print a message like this:
3977 Expression cannot be implemented with read/access watchpoint.
3980 Sometimes, @value{GDBN} cannot set a hardware watchpoint because the
3981 data type of the watched expression is wider than what a hardware
3982 watchpoint on the target machine can handle. For example, some systems
3983 can only watch regions that are up to 4 bytes wide; on such systems you
3984 cannot set hardware watchpoints for an expression that yields a
3985 double-precision floating-point number (which is typically 8 bytes
3986 wide). As a work-around, it might be possible to break the large region
3987 into a series of smaller ones and watch them with separate watchpoints.
3989 If you set too many hardware watchpoints, @value{GDBN} might be unable
3990 to insert all of them when you resume the execution of your program.
3991 Since the precise number of active watchpoints is unknown until such
3992 time as the program is about to be resumed, @value{GDBN} might not be
3993 able to warn you about this when you set the watchpoints, and the
3994 warning will be printed only when the program is resumed:
3997 Hardware watchpoint @var{num}: Could not insert watchpoint
4001 If this happens, delete or disable some of the watchpoints.
4003 Watching complex expressions that reference many variables can also
4004 exhaust the resources available for hardware-assisted watchpoints.
4005 That's because @value{GDBN} needs to watch every variable in the
4006 expression with separately allocated resources.
4008 If you call a function interactively using @code{print} or @code{call},
4009 any watchpoints you have set will be inactive until @value{GDBN} reaches another
4010 kind of breakpoint or the call completes.
4012 @value{GDBN} automatically deletes watchpoints that watch local
4013 (automatic) variables, or expressions that involve such variables, when
4014 they go out of scope, that is, when the execution leaves the block in
4015 which these variables were defined. In particular, when the program
4016 being debugged terminates, @emph{all} local variables go out of scope,
4017 and so only watchpoints that watch global variables remain set. If you
4018 rerun the program, you will need to set all such watchpoints again. One
4019 way of doing that would be to set a code breakpoint at the entry to the
4020 @code{main} function and when it breaks, set all the watchpoints.
4022 @cindex watchpoints and threads
4023 @cindex threads and watchpoints
4024 In multi-threaded programs, watchpoints will detect changes to the
4025 watched expression from every thread.
4028 @emph{Warning:} In multi-threaded programs, software watchpoints
4029 have only limited usefulness. If @value{GDBN} creates a software
4030 watchpoint, it can only watch the value of an expression @emph{in a
4031 single thread}. If you are confident that the expression can only
4032 change due to the current thread's activity (and if you are also
4033 confident that no other thread can become current), then you can use
4034 software watchpoints as usual. However, @value{GDBN} may not notice
4035 when a non-current thread's activity changes the expression. (Hardware
4036 watchpoints, in contrast, watch an expression in all threads.)
4039 @xref{set remote hardware-watchpoint-limit}.
4041 @node Set Catchpoints
4042 @subsection Setting Catchpoints
4043 @cindex catchpoints, setting
4044 @cindex exception handlers
4045 @cindex event handling
4047 You can use @dfn{catchpoints} to cause the debugger to stop for certain
4048 kinds of program events, such as C@t{++} exceptions or the loading of a
4049 shared library. Use the @code{catch} command to set a catchpoint.
4053 @item catch @var{event}
4054 Stop when @var{event} occurs. @var{event} can be any of the following:
4057 @cindex stop on C@t{++} exceptions
4058 The throwing of a C@t{++} exception.
4061 The catching of a C@t{++} exception.
4064 @cindex Ada exception catching
4065 @cindex catch Ada exceptions
4066 An Ada exception being raised. If an exception name is specified
4067 at the end of the command (eg @code{catch exception Program_Error}),
4068 the debugger will stop only when this specific exception is raised.
4069 Otherwise, the debugger stops execution when any Ada exception is raised.
4071 When inserting an exception catchpoint on a user-defined exception whose
4072 name is identical to one of the exceptions defined by the language, the
4073 fully qualified name must be used as the exception name. Otherwise,
4074 @value{GDBN} will assume that it should stop on the pre-defined exception
4075 rather than the user-defined one. For instance, assuming an exception
4076 called @code{Constraint_Error} is defined in package @code{Pck}, then
4077 the command to use to catch such exceptions is @kbd{catch exception
4078 Pck.Constraint_Error}.
4080 @item exception unhandled
4081 An exception that was raised but is not handled by the program.
4084 A failed Ada assertion.
4087 @cindex break on fork/exec
4088 A call to @code{exec}. This is currently only available for HP-UX
4092 @itemx syscall @r{[}@var{name} @r{|} @var{number}@r{]} @dots{}
4093 @cindex break on a system call.
4094 A call to or return from a system call, a.k.a.@: @dfn{syscall}. A
4095 syscall is a mechanism for application programs to request a service
4096 from the operating system (OS) or one of the OS system services.
4097 @value{GDBN} can catch some or all of the syscalls issued by the
4098 debuggee, and show the related information for each syscall. If no
4099 argument is specified, calls to and returns from all system calls
4102 @var{name} can be any system call name that is valid for the
4103 underlying OS. Just what syscalls are valid depends on the OS. On
4104 GNU and Unix systems, you can find the full list of valid syscall
4105 names on @file{/usr/include/asm/unistd.h}.
4107 @c For MS-Windows, the syscall names and the corresponding numbers
4108 @c can be found, e.g., on this URL:
4109 @c http://www.metasploit.com/users/opcode/syscalls.html
4110 @c but we don't support Windows syscalls yet.
4112 Normally, @value{GDBN} knows in advance which syscalls are valid for
4113 each OS, so you can use the @value{GDBN} command-line completion
4114 facilities (@pxref{Completion,, command completion}) to list the
4117 You may also specify the system call numerically. A syscall's
4118 number is the value passed to the OS's syscall dispatcher to
4119 identify the requested service. When you specify the syscall by its
4120 name, @value{GDBN} uses its database of syscalls to convert the name
4121 into the corresponding numeric code, but using the number directly
4122 may be useful if @value{GDBN}'s database does not have the complete
4123 list of syscalls on your system (e.g., because @value{GDBN} lags
4124 behind the OS upgrades).
4126 The example below illustrates how this command works if you don't provide
4130 (@value{GDBP}) catch syscall
4131 Catchpoint 1 (syscall)
4133 Starting program: /tmp/catch-syscall
4135 Catchpoint 1 (call to syscall 'close'), \
4136 0xffffe424 in __kernel_vsyscall ()
4140 Catchpoint 1 (returned from syscall 'close'), \
4141 0xffffe424 in __kernel_vsyscall ()
4145 Here is an example of catching a system call by name:
4148 (@value{GDBP}) catch syscall chroot
4149 Catchpoint 1 (syscall 'chroot' [61])
4151 Starting program: /tmp/catch-syscall
4153 Catchpoint 1 (call to syscall 'chroot'), \
4154 0xffffe424 in __kernel_vsyscall ()
4158 Catchpoint 1 (returned from syscall 'chroot'), \
4159 0xffffe424 in __kernel_vsyscall ()
4163 An example of specifying a system call numerically. In the case
4164 below, the syscall number has a corresponding entry in the XML
4165 file, so @value{GDBN} finds its name and prints it:
4168 (@value{GDBP}) catch syscall 252
4169 Catchpoint 1 (syscall(s) 'exit_group')
4171 Starting program: /tmp/catch-syscall
4173 Catchpoint 1 (call to syscall 'exit_group'), \
4174 0xffffe424 in __kernel_vsyscall ()
4178 Program exited normally.
4182 However, there can be situations when there is no corresponding name
4183 in XML file for that syscall number. In this case, @value{GDBN} prints
4184 a warning message saying that it was not able to find the syscall name,
4185 but the catchpoint will be set anyway. See the example below:
4188 (@value{GDBP}) catch syscall 764
4189 warning: The number '764' does not represent a known syscall.
4190 Catchpoint 2 (syscall 764)
4194 If you configure @value{GDBN} using the @samp{--without-expat} option,
4195 it will not be able to display syscall names. Also, if your
4196 architecture does not have an XML file describing its system calls,
4197 you will not be able to see the syscall names. It is important to
4198 notice that these two features are used for accessing the syscall
4199 name database. In either case, you will see a warning like this:
4202 (@value{GDBP}) catch syscall
4203 warning: Could not open "syscalls/i386-linux.xml"
4204 warning: Could not load the syscall XML file 'syscalls/i386-linux.xml'.
4205 GDB will not be able to display syscall names.
4206 Catchpoint 1 (syscall)
4210 Of course, the file name will change depending on your architecture and system.
4212 Still using the example above, you can also try to catch a syscall by its
4213 number. In this case, you would see something like:
4216 (@value{GDBP}) catch syscall 252
4217 Catchpoint 1 (syscall(s) 252)
4220 Again, in this case @value{GDBN} would not be able to display syscall's names.
4223 A call to @code{fork}. This is currently only available for HP-UX
4227 A call to @code{vfork}. This is currently only available for HP-UX
4230 @item load @r{[}regexp@r{]}
4231 @itemx unload @r{[}regexp@r{]}
4232 The loading or unloading of a shared library. If @var{regexp} is
4233 given, then the catchpoint will stop only if the regular expression
4234 matches one of the affected libraries.
4236 @item signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
4237 The delivery of a signal.
4239 With no arguments, this catchpoint will catch any signal that is not
4240 used internally by @value{GDBN}, specifically, all signals except
4241 @samp{SIGTRAP} and @samp{SIGINT}.
4243 With the argument @samp{all}, all signals, including those used by
4244 @value{GDBN}, will be caught. This argument cannot be used with other
4247 Otherwise, the arguments are a list of signal names as given to
4248 @code{handle} (@pxref{Signals}). Only signals specified in this list
4251 One reason that @code{catch signal} can be more useful than
4252 @code{handle} is that you can attach commands and conditions to the
4255 When a signal is caught by a catchpoint, the signal's @code{stop} and
4256 @code{print} settings, as specified by @code{handle}, are ignored.
4257 However, whether the signal is still delivered to the inferior depends
4258 on the @code{pass} setting; this can be changed in the catchpoint's
4263 @item tcatch @var{event}
4264 Set a catchpoint that is enabled only for one stop. The catchpoint is
4265 automatically deleted after the first time the event is caught.
4269 Use the @code{info break} command to list the current catchpoints.
4271 There are currently some limitations to C@t{++} exception handling
4272 (@code{catch throw} and @code{catch catch}) in @value{GDBN}:
4276 If you call a function interactively, @value{GDBN} normally returns
4277 control to you when the function has finished executing. If the call
4278 raises an exception, however, the call may bypass the mechanism that
4279 returns control to you and cause your program either to abort or to
4280 simply continue running until it hits a breakpoint, catches a signal
4281 that @value{GDBN} is listening for, or exits. This is the case even if
4282 you set a catchpoint for the exception; catchpoints on exceptions are
4283 disabled within interactive calls.
4286 You cannot raise an exception interactively.
4289 You cannot install an exception handler interactively.
4292 @cindex raise exceptions
4293 Sometimes @code{catch} is not the best way to debug exception handling:
4294 if you need to know exactly where an exception is raised, it is better to
4295 stop @emph{before} the exception handler is called, since that way you
4296 can see the stack before any unwinding takes place. If you set a
4297 breakpoint in an exception handler instead, it may not be easy to find
4298 out where the exception was raised.
4300 To stop just before an exception handler is called, you need some
4301 knowledge of the implementation. In the case of @sc{gnu} C@t{++}, exceptions are
4302 raised by calling a library function named @code{__raise_exception}
4303 which has the following ANSI C interface:
4306 /* @var{addr} is where the exception identifier is stored.
4307 @var{id} is the exception identifier. */
4308 void __raise_exception (void **addr, void *id);
4312 To make the debugger catch all exceptions before any stack
4313 unwinding takes place, set a breakpoint on @code{__raise_exception}
4314 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Exceptions}).
4316 With a conditional breakpoint (@pxref{Conditions, ,Break Conditions})
4317 that depends on the value of @var{id}, you can stop your program when
4318 a specific exception is raised. You can use multiple conditional
4319 breakpoints to stop your program when any of a number of exceptions are
4324 @subsection Deleting Breakpoints
4326 @cindex clearing breakpoints, watchpoints, catchpoints
4327 @cindex deleting breakpoints, watchpoints, catchpoints
4328 It is often necessary to eliminate a breakpoint, watchpoint, or
4329 catchpoint once it has done its job and you no longer want your program
4330 to stop there. This is called @dfn{deleting} the breakpoint. A
4331 breakpoint that has been deleted no longer exists; it is forgotten.
4333 With the @code{clear} command you can delete breakpoints according to
4334 where they are in your program. With the @code{delete} command you can
4335 delete individual breakpoints, watchpoints, or catchpoints by specifying
4336 their breakpoint numbers.
4338 It is not necessary to delete a breakpoint to proceed past it. @value{GDBN}
4339 automatically ignores breakpoints on the first instruction to be executed
4340 when you continue execution without changing the execution address.
4345 Delete any breakpoints at the next instruction to be executed in the
4346 selected stack frame (@pxref{Selection, ,Selecting a Frame}). When
4347 the innermost frame is selected, this is a good way to delete a
4348 breakpoint where your program just stopped.
4350 @item clear @var{location}
4351 Delete any breakpoints set at the specified @var{location}.
4352 @xref{Specify Location}, for the various forms of @var{location}; the
4353 most useful ones are listed below:
4356 @item clear @var{function}
4357 @itemx clear @var{filename}:@var{function}
4358 Delete any breakpoints set at entry to the named @var{function}.
4360 @item clear @var{linenum}
4361 @itemx clear @var{filename}:@var{linenum}
4362 Delete any breakpoints set at or within the code of the specified
4363 @var{linenum} of the specified @var{filename}.
4366 @cindex delete breakpoints
4368 @kindex d @r{(@code{delete})}
4369 @item delete @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4370 Delete the breakpoints, watchpoints, or catchpoints of the breakpoint
4371 ranges specified as arguments. If no argument is specified, delete all
4372 breakpoints (@value{GDBN} asks confirmation, unless you have @code{set
4373 confirm off}). You can abbreviate this command as @code{d}.
4377 @subsection Disabling Breakpoints
4379 @cindex enable/disable a breakpoint
4380 Rather than deleting a breakpoint, watchpoint, or catchpoint, you might
4381 prefer to @dfn{disable} it. This makes the breakpoint inoperative as if
4382 it had been deleted, but remembers the information on the breakpoint so
4383 that you can @dfn{enable} it again later.
4385 You disable and enable breakpoints, watchpoints, and catchpoints with
4386 the @code{enable} and @code{disable} commands, optionally specifying
4387 one or more breakpoint numbers as arguments. Use @code{info break} to
4388 print a list of all breakpoints, watchpoints, and catchpoints if you
4389 do not know which numbers to use.
4391 Disabling and enabling a breakpoint that has multiple locations
4392 affects all of its locations.
4394 A breakpoint, watchpoint, or catchpoint can have any of several
4395 different states of enablement:
4399 Enabled. The breakpoint stops your program. A breakpoint set
4400 with the @code{break} command starts out in this state.
4402 Disabled. The breakpoint has no effect on your program.
4404 Enabled once. The breakpoint stops your program, but then becomes
4407 Enabled for a count. The breakpoint stops your program for the next
4408 N times, then becomes disabled.
4410 Enabled for deletion. The breakpoint stops your program, but
4411 immediately after it does so it is deleted permanently. A breakpoint
4412 set with the @code{tbreak} command starts out in this state.
4415 You can use the following commands to enable or disable breakpoints,
4416 watchpoints, and catchpoints:
4420 @kindex dis @r{(@code{disable})}
4421 @item disable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4422 Disable the specified breakpoints---or all breakpoints, if none are
4423 listed. A disabled breakpoint has no effect but is not forgotten. All
4424 options such as ignore-counts, conditions and commands are remembered in
4425 case the breakpoint is enabled again later. You may abbreviate
4426 @code{disable} as @code{dis}.
4429 @item enable @r{[}breakpoints@r{]} @r{[}@var{range}@dots{}@r{]}
4430 Enable the specified breakpoints (or all defined breakpoints). They
4431 become effective once again in stopping your program.
4433 @item enable @r{[}breakpoints@r{]} once @var{range}@dots{}
4434 Enable the specified breakpoints temporarily. @value{GDBN} disables any
4435 of these breakpoints immediately after stopping your program.
4437 @item enable @r{[}breakpoints@r{]} count @var{count} @var{range}@dots{}
4438 Enable the specified breakpoints temporarily. @value{GDBN} records
4439 @var{count} with each of the specified breakpoints, and decrements a
4440 breakpoint's count when it is hit. When any count reaches 0,
4441 @value{GDBN} disables that breakpoint. If a breakpoint has an ignore
4442 count (@pxref{Conditions, ,Break Conditions}), that will be
4443 decremented to 0 before @var{count} is affected.
4445 @item enable @r{[}breakpoints@r{]} delete @var{range}@dots{}
4446 Enable the specified breakpoints to work once, then die. @value{GDBN}
4447 deletes any of these breakpoints as soon as your program stops there.
4448 Breakpoints set by the @code{tbreak} command start out in this state.
4451 @c FIXME: I think the following ``Except for [...] @code{tbreak}'' is
4452 @c confusing: tbreak is also initially enabled.
4453 Except for a breakpoint set with @code{tbreak} (@pxref{Set Breaks,
4454 ,Setting Breakpoints}), breakpoints that you set are initially enabled;
4455 subsequently, they become disabled or enabled only when you use one of
4456 the commands above. (The command @code{until} can set and delete a
4457 breakpoint of its own, but it does not change the state of your other
4458 breakpoints; see @ref{Continuing and Stepping, ,Continuing and
4462 @subsection Break Conditions
4463 @cindex conditional breakpoints
4464 @cindex breakpoint conditions
4466 @c FIXME what is scope of break condition expr? Context where wanted?
4467 @c in particular for a watchpoint?
4468 The simplest sort of breakpoint breaks every time your program reaches a
4469 specified place. You can also specify a @dfn{condition} for a
4470 breakpoint. A condition is just a Boolean expression in your
4471 programming language (@pxref{Expressions, ,Expressions}). A breakpoint with
4472 a condition evaluates the expression each time your program reaches it,
4473 and your program stops only if the condition is @emph{true}.
4475 This is the converse of using assertions for program validation; in that
4476 situation, you want to stop when the assertion is violated---that is,
4477 when the condition is false. In C, if you want to test an assertion expressed
4478 by the condition @var{assert}, you should set the condition
4479 @samp{! @var{assert}} on the appropriate breakpoint.
4481 Conditions are also accepted for watchpoints; you may not need them,
4482 since a watchpoint is inspecting the value of an expression anyhow---but
4483 it might be simpler, say, to just set a watchpoint on a variable name,
4484 and specify a condition that tests whether the new value is an interesting
4487 Break conditions can have side effects, and may even call functions in
4488 your program. This can be useful, for example, to activate functions
4489 that log program progress, or to use your own print functions to
4490 format special data structures. The effects are completely predictable
4491 unless there is another enabled breakpoint at the same address. (In
4492 that case, @value{GDBN} might see the other breakpoint first and stop your
4493 program without checking the condition of this one.) Note that
4494 breakpoint commands are usually more convenient and flexible than break
4496 purpose of performing side effects when a breakpoint is reached
4497 (@pxref{Break Commands, ,Breakpoint Command Lists}).
4499 Breakpoint conditions can also be evaluated on the target's side if
4500 the target supports it. Instead of evaluating the conditions locally,
4501 @value{GDBN} encodes the expression into an agent expression
4502 (@pxref{Agent Expressions}) suitable for execution on the target,
4503 independently of @value{GDBN}. Global variables become raw memory
4504 locations, locals become stack accesses, and so forth.
4506 In this case, @value{GDBN} will only be notified of a breakpoint trigger
4507 when its condition evaluates to true. This mechanism may provide faster
4508 response times depending on the performance characteristics of the target
4509 since it does not need to keep @value{GDBN} informed about
4510 every breakpoint trigger, even those with false conditions.
4512 Break conditions can be specified when a breakpoint is set, by using
4513 @samp{if} in the arguments to the @code{break} command. @xref{Set
4514 Breaks, ,Setting Breakpoints}. They can also be changed at any time
4515 with the @code{condition} command.
4517 You can also use the @code{if} keyword with the @code{watch} command.
4518 The @code{catch} command does not recognize the @code{if} keyword;
4519 @code{condition} is the only way to impose a further condition on a
4524 @item condition @var{bnum} @var{expression}
4525 Specify @var{expression} as the break condition for breakpoint,
4526 watchpoint, or catchpoint number @var{bnum}. After you set a condition,
4527 breakpoint @var{bnum} stops your program only if the value of
4528 @var{expression} is true (nonzero, in C). When you use
4529 @code{condition}, @value{GDBN} checks @var{expression} immediately for
4530 syntactic correctness, and to determine whether symbols in it have
4531 referents in the context of your breakpoint. If @var{expression} uses
4532 symbols not referenced in the context of the breakpoint, @value{GDBN}
4533 prints an error message:
4536 No symbol "foo" in current context.
4541 not actually evaluate @var{expression} at the time the @code{condition}
4542 command (or a command that sets a breakpoint with a condition, like
4543 @code{break if @dots{}}) is given, however. @xref{Expressions, ,Expressions}.
4545 @item condition @var{bnum}
4546 Remove the condition from breakpoint number @var{bnum}. It becomes
4547 an ordinary unconditional breakpoint.
4550 @cindex ignore count (of breakpoint)
4551 A special case of a breakpoint condition is to stop only when the
4552 breakpoint has been reached a certain number of times. This is so
4553 useful that there is a special way to do it, using the @dfn{ignore
4554 count} of the breakpoint. Every breakpoint has an ignore count, which
4555 is an integer. Most of the time, the ignore count is zero, and
4556 therefore has no effect. But if your program reaches a breakpoint whose
4557 ignore count is positive, then instead of stopping, it just decrements
4558 the ignore count by one and continues. As a result, if the ignore count
4559 value is @var{n}, the breakpoint does not stop the next @var{n} times
4560 your program reaches it.
4564 @item ignore @var{bnum} @var{count}
4565 Set the ignore count of breakpoint number @var{bnum} to @var{count}.
4566 The next @var{count} times the breakpoint is reached, your program's
4567 execution does not stop; other than to decrement the ignore count, @value{GDBN}
4570 To make the breakpoint stop the next time it is reached, specify
4573 When you use @code{continue} to resume execution of your program from a
4574 breakpoint, you can specify an ignore count directly as an argument to
4575 @code{continue}, rather than using @code{ignore}. @xref{Continuing and
4576 Stepping,,Continuing and Stepping}.
4578 If a breakpoint has a positive ignore count and a condition, the
4579 condition is not checked. Once the ignore count reaches zero,
4580 @value{GDBN} resumes checking the condition.
4582 You could achieve the effect of the ignore count with a condition such
4583 as @w{@samp{$foo-- <= 0}} using a debugger convenience variable that
4584 is decremented each time. @xref{Convenience Vars, ,Convenience
4588 Ignore counts apply to breakpoints, watchpoints, and catchpoints.
4591 @node Break Commands
4592 @subsection Breakpoint Command Lists
4594 @cindex breakpoint commands
4595 You can give any breakpoint (or watchpoint or catchpoint) a series of
4596 commands to execute when your program stops due to that breakpoint. For
4597 example, you might want to print the values of certain expressions, or
4598 enable other breakpoints.
4602 @kindex end@r{ (breakpoint commands)}
4603 @item commands @r{[}@var{range}@dots{}@r{]}
4604 @itemx @dots{} @var{command-list} @dots{}
4606 Specify a list of commands for the given breakpoints. The commands
4607 themselves appear on the following lines. Type a line containing just
4608 @code{end} to terminate the commands.
4610 To remove all commands from a breakpoint, type @code{commands} and
4611 follow it immediately with @code{end}; that is, give no commands.
4613 With no argument, @code{commands} refers to the last breakpoint,
4614 watchpoint, or catchpoint set (not to the breakpoint most recently
4615 encountered). If the most recent breakpoints were set with a single
4616 command, then the @code{commands} will apply to all the breakpoints
4617 set by that command. This applies to breakpoints set by
4618 @code{rbreak}, and also applies when a single @code{break} command
4619 creates multiple breakpoints (@pxref{Ambiguous Expressions,,Ambiguous
4623 Pressing @key{RET} as a means of repeating the last @value{GDBN} command is
4624 disabled within a @var{command-list}.
4626 You can use breakpoint commands to start your program up again. Simply
4627 use the @code{continue} command, or @code{step}, or any other command
4628 that resumes execution.
4630 Any other commands in the command list, after a command that resumes
4631 execution, are ignored. This is because any time you resume execution
4632 (even with a simple @code{next} or @code{step}), you may encounter
4633 another breakpoint---which could have its own command list, leading to
4634 ambiguities about which list to execute.
4637 If the first command you specify in a command list is @code{silent}, the
4638 usual message about stopping at a breakpoint is not printed. This may
4639 be desirable for breakpoints that are to print a specific message and
4640 then continue. If none of the remaining commands print anything, you
4641 see no sign that the breakpoint was reached. @code{silent} is
4642 meaningful only at the beginning of a breakpoint command list.
4644 The commands @code{echo}, @code{output}, and @code{printf} allow you to
4645 print precisely controlled output, and are often useful in silent
4646 breakpoints. @xref{Output, ,Commands for Controlled Output}.
4648 For example, here is how you could use breakpoint commands to print the
4649 value of @code{x} at entry to @code{foo} whenever @code{x} is positive.
4655 printf "x is %d\n",x
4660 One application for breakpoint commands is to compensate for one bug so
4661 you can test for another. Put a breakpoint just after the erroneous line
4662 of code, give it a condition to detect the case in which something
4663 erroneous has been done, and give it commands to assign correct values
4664 to any variables that need them. End with the @code{continue} command
4665 so that your program does not stop, and start with the @code{silent}
4666 command so that no output is produced. Here is an example:
4677 @node Dynamic Printf
4678 @subsection Dynamic Printf
4680 @cindex dynamic printf
4682 The dynamic printf command @code{dprintf} combines a breakpoint with
4683 formatted printing of your program's data to give you the effect of
4684 inserting @code{printf} calls into your program on-the-fly, without
4685 having to recompile it.
4687 In its most basic form, the output goes to the GDB console. However,
4688 you can set the variable @code{dprintf-style} for alternate handling.
4689 For instance, you can ask to format the output by calling your
4690 program's @code{printf} function. This has the advantage that the
4691 characters go to the program's output device, so they can recorded in
4692 redirects to files and so forth.
4694 If you are doing remote debugging with a stub or agent, you can also
4695 ask to have the printf handled by the remote agent. In addition to
4696 ensuring that the output goes to the remote program's device along
4697 with any other output the program might produce, you can also ask that
4698 the dprintf remain active even after disconnecting from the remote
4699 target. Using the stub/agent is also more efficient, as it can do
4700 everything without needing to communicate with @value{GDBN}.
4704 @item dprintf @var{location},@var{template},@var{expression}[,@var{expression}@dots{}]
4705 Whenever execution reaches @var{location}, print the values of one or
4706 more @var{expressions} under the control of the string @var{template}.
4707 To print several values, separate them with commas.
4709 @item set dprintf-style @var{style}
4710 Set the dprintf output to be handled in one of several different
4711 styles enumerated below. A change of style affects all existing
4712 dynamic printfs immediately. (If you need individual control over the
4713 print commands, simply define normal breakpoints with
4714 explicitly-supplied command lists.)
4717 @kindex dprintf-style gdb
4718 Handle the output using the @value{GDBN} @code{printf} command.
4721 @kindex dprintf-style call
4722 Handle the output by calling a function in your program (normally
4726 @kindex dprintf-style agent
4727 Have the remote debugging agent (such as @code{gdbserver}) handle
4728 the output itself. This style is only available for agents that
4729 support running commands on the target.
4731 @item set dprintf-function @var{function}
4732 Set the function to call if the dprintf style is @code{call}. By
4733 default its value is @code{printf}. You may set it to any expression.
4734 that @value{GDBN} can evaluate to a function, as per the @code{call}
4737 @item set dprintf-channel @var{channel}
4738 Set a ``channel'' for dprintf. If set to a non-empty value,
4739 @value{GDBN} will evaluate it as an expression and pass the result as
4740 a first argument to the @code{dprintf-function}, in the manner of
4741 @code{fprintf} and similar functions. Otherwise, the dprintf format
4742 string will be the first argument, in the manner of @code{printf}.
4744 As an example, if you wanted @code{dprintf} output to go to a logfile
4745 that is a standard I/O stream assigned to the variable @code{mylog},
4746 you could do the following:
4749 (gdb) set dprintf-style call
4750 (gdb) set dprintf-function fprintf
4751 (gdb) set dprintf-channel mylog
4752 (gdb) dprintf 25,"at line 25, glob=%d\n",glob
4753 Dprintf 1 at 0x123456: file main.c, line 25.
4755 1 dprintf keep y 0x00123456 in main at main.c:25
4756 call (void) fprintf (mylog,"at line 25, glob=%d\n",glob)
4761 Note that the @code{info break} displays the dynamic printf commands
4762 as normal breakpoint commands; you can thus easily see the effect of
4763 the variable settings.
4765 @item set disconnected-dprintf on
4766 @itemx set disconnected-dprintf off
4767 @kindex set disconnected-dprintf
4768 Choose whether @code{dprintf} commands should continue to run if
4769 @value{GDBN} has disconnected from the target. This only applies
4770 if the @code{dprintf-style} is @code{agent}.
4772 @item show disconnected-dprintf off
4773 @kindex show disconnected-dprintf
4774 Show the current choice for disconnected @code{dprintf}.
4778 @value{GDBN} does not check the validity of function and channel,
4779 relying on you to supply values that are meaningful for the contexts
4780 in which they are being used. For instance, the function and channel
4781 may be the values of local variables, but if that is the case, then
4782 all enabled dynamic prints must be at locations within the scope of
4783 those locals. If evaluation fails, @value{GDBN} will report an error.
4785 @node Save Breakpoints
4786 @subsection How to save breakpoints to a file
4788 To save breakpoint definitions to a file use the @w{@code{save
4789 breakpoints}} command.
4792 @kindex save breakpoints
4793 @cindex save breakpoints to a file for future sessions
4794 @item save breakpoints [@var{filename}]
4795 This command saves all current breakpoint definitions together with
4796 their commands and ignore counts, into a file @file{@var{filename}}
4797 suitable for use in a later debugging session. This includes all
4798 types of breakpoints (breakpoints, watchpoints, catchpoints,
4799 tracepoints). To read the saved breakpoint definitions, use the
4800 @code{source} command (@pxref{Command Files}). Note that watchpoints
4801 with expressions involving local variables may fail to be recreated
4802 because it may not be possible to access the context where the
4803 watchpoint is valid anymore. Because the saved breakpoint definitions
4804 are simply a sequence of @value{GDBN} commands that recreate the
4805 breakpoints, you can edit the file in your favorite editing program,
4806 and remove the breakpoint definitions you're not interested in, or
4807 that can no longer be recreated.
4810 @node Static Probe Points
4811 @subsection Static Probe Points
4813 @cindex static probe point, SystemTap
4814 @value{GDBN} supports @dfn{SDT} probes in the code. @acronym{SDT} stands
4815 for Statically Defined Tracing, and the probes are designed to have a tiny
4816 runtime code and data footprint, and no dynamic relocations. They are
4817 usable from assembly, C and C@t{++} languages. See
4818 @uref{http://sourceware.org/systemtap/wiki/UserSpaceProbeImplementation}
4819 for a good reference on how the @acronym{SDT} probes are implemented.
4821 Currently, @code{SystemTap} (@uref{http://sourceware.org/systemtap/})
4822 @acronym{SDT} probes are supported on ELF-compatible systems. See
4823 @uref{http://sourceware.org/systemtap/wiki/AddingUserSpaceProbingToApps}
4824 for more information on how to add @code{SystemTap} @acronym{SDT} probes
4825 in your applications.
4827 @cindex semaphores on static probe points
4828 Some probes have an associated semaphore variable; for instance, this
4829 happens automatically if you defined your probe using a DTrace-style
4830 @file{.d} file. If your probe has a semaphore, @value{GDBN} will
4831 automatically enable it when you specify a breakpoint using the
4832 @samp{-probe-stap} notation. But, if you put a breakpoint at a probe's
4833 location by some other method (e.g., @code{break file:line}), then
4834 @value{GDBN} will not automatically set the semaphore.
4836 You can examine the available static static probes using @code{info
4837 probes}, with optional arguments:
4841 @item info probes stap @r{[}@var{provider} @r{[}@var{name} @r{[}@var{objfile}@r{]}@r{]}@r{]}
4842 If given, @var{provider} is a regular expression used to match against provider
4843 names when selecting which probes to list. If omitted, probes by all
4844 probes from all providers are listed.
4846 If given, @var{name} is a regular expression to match against probe names
4847 when selecting which probes to list. If omitted, probe names are not
4848 considered when deciding whether to display them.
4850 If given, @var{objfile} is a regular expression used to select which
4851 object files (executable or shared libraries) to examine. If not
4852 given, all object files are considered.
4854 @item info probes all
4855 List the available static probes, from all types.
4858 @vindex $_probe_arg@r{, convenience variable}
4859 A probe may specify up to twelve arguments. These are available at the
4860 point at which the probe is defined---that is, when the current PC is
4861 at the probe's location. The arguments are available using the
4862 convenience variables (@pxref{Convenience Vars})
4863 @code{$_probe_arg0}@dots{}@code{$_probe_arg11}. Each probe argument is
4864 an integer of the appropriate size; types are not preserved. The
4865 convenience variable @code{$_probe_argc} holds the number of arguments
4866 at the current probe point.
4868 These variables are always available, but attempts to access them at
4869 any location other than a probe point will cause @value{GDBN} to give
4873 @c @ifclear BARETARGET
4874 @node Error in Breakpoints
4875 @subsection ``Cannot insert breakpoints''
4877 If you request too many active hardware-assisted breakpoints and
4878 watchpoints, you will see this error message:
4880 @c FIXME: the precise wording of this message may change; the relevant
4881 @c source change is not committed yet (Sep 3, 1999).
4883 Stopped; cannot insert breakpoints.
4884 You may have requested too many hardware breakpoints and watchpoints.
4888 This message is printed when you attempt to resume the program, since
4889 only then @value{GDBN} knows exactly how many hardware breakpoints and
4890 watchpoints it needs to insert.
4892 When this message is printed, you need to disable or remove some of the
4893 hardware-assisted breakpoints and watchpoints, and then continue.
4895 @node Breakpoint-related Warnings
4896 @subsection ``Breakpoint address adjusted...''
4897 @cindex breakpoint address adjusted
4899 Some processor architectures place constraints on the addresses at
4900 which breakpoints may be placed. For architectures thus constrained,
4901 @value{GDBN} will attempt to adjust the breakpoint's address to comply
4902 with the constraints dictated by the architecture.
4904 One example of such an architecture is the Fujitsu FR-V. The FR-V is
4905 a VLIW architecture in which a number of RISC-like instructions may be
4906 bundled together for parallel execution. The FR-V architecture
4907 constrains the location of a breakpoint instruction within such a
4908 bundle to the instruction with the lowest address. @value{GDBN}
4909 honors this constraint by adjusting a breakpoint's address to the
4910 first in the bundle.
4912 It is not uncommon for optimized code to have bundles which contain
4913 instructions from different source statements, thus it may happen that
4914 a breakpoint's address will be adjusted from one source statement to
4915 another. Since this adjustment may significantly alter @value{GDBN}'s
4916 breakpoint related behavior from what the user expects, a warning is
4917 printed when the breakpoint is first set and also when the breakpoint
4920 A warning like the one below is printed when setting a breakpoint
4921 that's been subject to address adjustment:
4924 warning: Breakpoint address adjusted from 0x00010414 to 0x00010410.
4927 Such warnings are printed both for user settable and @value{GDBN}'s
4928 internal breakpoints. If you see one of these warnings, you should
4929 verify that a breakpoint set at the adjusted address will have the
4930 desired affect. If not, the breakpoint in question may be removed and
4931 other breakpoints may be set which will have the desired behavior.
4932 E.g., it may be sufficient to place the breakpoint at a later
4933 instruction. A conditional breakpoint may also be useful in some
4934 cases to prevent the breakpoint from triggering too often.
4936 @value{GDBN} will also issue a warning when stopping at one of these
4937 adjusted breakpoints:
4940 warning: Breakpoint 1 address previously adjusted from 0x00010414
4944 When this warning is encountered, it may be too late to take remedial
4945 action except in cases where the breakpoint is hit earlier or more
4946 frequently than expected.
4948 @node Continuing and Stepping
4949 @section Continuing and Stepping
4953 @cindex resuming execution
4954 @dfn{Continuing} means resuming program execution until your program
4955 completes normally. In contrast, @dfn{stepping} means executing just
4956 one more ``step'' of your program, where ``step'' may mean either one
4957 line of source code, or one machine instruction (depending on what
4958 particular command you use). Either when continuing or when stepping,
4959 your program may stop even sooner, due to a breakpoint or a signal. (If
4960 it stops due to a signal, you may want to use @code{handle}, or use
4961 @samp{signal 0} to resume execution. @xref{Signals, ,Signals}.)
4965 @kindex c @r{(@code{continue})}
4966 @kindex fg @r{(resume foreground execution)}
4967 @item continue @r{[}@var{ignore-count}@r{]}
4968 @itemx c @r{[}@var{ignore-count}@r{]}
4969 @itemx fg @r{[}@var{ignore-count}@r{]}
4970 Resume program execution, at the address where your program last stopped;
4971 any breakpoints set at that address are bypassed. The optional argument
4972 @var{ignore-count} allows you to specify a further number of times to
4973 ignore a breakpoint at this location; its effect is like that of
4974 @code{ignore} (@pxref{Conditions, ,Break Conditions}).
4976 The argument @var{ignore-count} is meaningful only when your program
4977 stopped due to a breakpoint. At other times, the argument to
4978 @code{continue} is ignored.
4980 The synonyms @code{c} and @code{fg} (for @dfn{foreground}, as the
4981 debugged program is deemed to be the foreground program) are provided
4982 purely for convenience, and have exactly the same behavior as
4986 To resume execution at a different place, you can use @code{return}
4987 (@pxref{Returning, ,Returning from a Function}) to go back to the
4988 calling function; or @code{jump} (@pxref{Jumping, ,Continuing at a
4989 Different Address}) to go to an arbitrary location in your program.
4991 A typical technique for using stepping is to set a breakpoint
4992 (@pxref{Breakpoints, ,Breakpoints; Watchpoints; and Catchpoints}) at the
4993 beginning of the function or the section of your program where a problem
4994 is believed to lie, run your program until it stops at that breakpoint,
4995 and then step through the suspect area, examining the variables that are
4996 interesting, until you see the problem happen.
5000 @kindex s @r{(@code{step})}
5002 Continue running your program until control reaches a different source
5003 line, then stop it and return control to @value{GDBN}. This command is
5004 abbreviated @code{s}.
5007 @c "without debugging information" is imprecise; actually "without line
5008 @c numbers in the debugging information". (gcc -g1 has debugging info but
5009 @c not line numbers). But it seems complex to try to make that
5010 @c distinction here.
5011 @emph{Warning:} If you use the @code{step} command while control is
5012 within a function that was compiled without debugging information,
5013 execution proceeds until control reaches a function that does have
5014 debugging information. Likewise, it will not step into a function which
5015 is compiled without debugging information. To step through functions
5016 without debugging information, use the @code{stepi} command, described
5020 The @code{step} command only stops at the first instruction of a source
5021 line. This prevents the multiple stops that could otherwise occur in
5022 @code{switch} statements, @code{for} loops, etc. @code{step} continues
5023 to stop if a function that has debugging information is called within
5024 the line. In other words, @code{step} @emph{steps inside} any functions
5025 called within the line.
5027 Also, the @code{step} command only enters a function if there is line
5028 number information for the function. Otherwise it acts like the
5029 @code{next} command. This avoids problems when using @code{cc -gl}
5030 on @acronym{MIPS} machines. Previously, @code{step} entered subroutines if there
5031 was any debugging information about the routine.
5033 @item step @var{count}
5034 Continue running as in @code{step}, but do so @var{count} times. If a
5035 breakpoint is reached, or a signal not related to stepping occurs before
5036 @var{count} steps, stepping stops right away.
5039 @kindex n @r{(@code{next})}
5040 @item next @r{[}@var{count}@r{]}
5041 Continue to the next source line in the current (innermost) stack frame.
5042 This is similar to @code{step}, but function calls that appear within
5043 the line of code are executed without stopping. Execution stops when
5044 control reaches a different line of code at the original stack level
5045 that was executing when you gave the @code{next} command. This command
5046 is abbreviated @code{n}.
5048 An argument @var{count} is a repeat count, as for @code{step}.
5051 @c FIX ME!! Do we delete this, or is there a way it fits in with
5052 @c the following paragraph? --- Vctoria
5054 @c @code{next} within a function that lacks debugging information acts like
5055 @c @code{step}, but any function calls appearing within the code of the
5056 @c function are executed without stopping.
5058 The @code{next} command only stops at the first instruction of a
5059 source line. This prevents multiple stops that could otherwise occur in
5060 @code{switch} statements, @code{for} loops, etc.
5062 @kindex set step-mode
5064 @cindex functions without line info, and stepping
5065 @cindex stepping into functions with no line info
5066 @itemx set step-mode on
5067 The @code{set step-mode on} command causes the @code{step} command to
5068 stop at the first instruction of a function which contains no debug line
5069 information rather than stepping over it.
5071 This is useful in cases where you may be interested in inspecting the
5072 machine instructions of a function which has no symbolic info and do not
5073 want @value{GDBN} to automatically skip over this function.
5075 @item set step-mode off
5076 Causes the @code{step} command to step over any functions which contains no
5077 debug information. This is the default.
5079 @item show step-mode
5080 Show whether @value{GDBN} will stop in or step over functions without
5081 source line debug information.
5084 @kindex fin @r{(@code{finish})}
5086 Continue running until just after function in the selected stack frame
5087 returns. Print the returned value (if any). This command can be
5088 abbreviated as @code{fin}.
5090 Contrast this with the @code{return} command (@pxref{Returning,
5091 ,Returning from a Function}).
5094 @kindex u @r{(@code{until})}
5095 @cindex run until specified location
5098 Continue running until a source line past the current line, in the
5099 current stack frame, is reached. This command is used to avoid single
5100 stepping through a loop more than once. It is like the @code{next}
5101 command, except that when @code{until} encounters a jump, it
5102 automatically continues execution until the program counter is greater
5103 than the address of the jump.
5105 This means that when you reach the end of a loop after single stepping
5106 though it, @code{until} makes your program continue execution until it
5107 exits the loop. In contrast, a @code{next} command at the end of a loop
5108 simply steps back to the beginning of the loop, which forces you to step
5109 through the next iteration.
5111 @code{until} always stops your program if it attempts to exit the current
5114 @code{until} may produce somewhat counterintuitive results if the order
5115 of machine code does not match the order of the source lines. For
5116 example, in the following excerpt from a debugging session, the @code{f}
5117 (@code{frame}) command shows that execution is stopped at line
5118 @code{206}; yet when we use @code{until}, we get to line @code{195}:
5122 #0 main (argc=4, argv=0xf7fffae8) at m4.c:206
5124 (@value{GDBP}) until
5125 195 for ( ; argc > 0; NEXTARG) @{
5128 This happened because, for execution efficiency, the compiler had
5129 generated code for the loop closure test at the end, rather than the
5130 start, of the loop---even though the test in a C @code{for}-loop is
5131 written before the body of the loop. The @code{until} command appeared
5132 to step back to the beginning of the loop when it advanced to this
5133 expression; however, it has not really gone to an earlier
5134 statement---not in terms of the actual machine code.
5136 @code{until} with no argument works by means of single
5137 instruction stepping, and hence is slower than @code{until} with an
5140 @item until @var{location}
5141 @itemx u @var{location}
5142 Continue running your program until either the specified location is
5143 reached, or the current stack frame returns. @var{location} is any of
5144 the forms described in @ref{Specify Location}.
5145 This form of the command uses temporary breakpoints, and
5146 hence is quicker than @code{until} without an argument. The specified
5147 location is actually reached only if it is in the current frame. This
5148 implies that @code{until} can be used to skip over recursive function
5149 invocations. For instance in the code below, if the current location is
5150 line @code{96}, issuing @code{until 99} will execute the program up to
5151 line @code{99} in the same invocation of factorial, i.e., after the inner
5152 invocations have returned.
5155 94 int factorial (int value)
5157 96 if (value > 1) @{
5158 97 value *= factorial (value - 1);
5165 @kindex advance @var{location}
5166 @item advance @var{location}
5167 Continue running the program up to the given @var{location}. An argument is
5168 required, which should be of one of the forms described in
5169 @ref{Specify Location}.
5170 Execution will also stop upon exit from the current stack
5171 frame. This command is similar to @code{until}, but @code{advance} will
5172 not skip over recursive function calls, and the target location doesn't
5173 have to be in the same frame as the current one.
5177 @kindex si @r{(@code{stepi})}
5179 @itemx stepi @var{arg}
5181 Execute one machine instruction, then stop and return to the debugger.
5183 It is often useful to do @samp{display/i $pc} when stepping by machine
5184 instructions. This makes @value{GDBN} automatically display the next
5185 instruction to be executed, each time your program stops. @xref{Auto
5186 Display,, Automatic Display}.
5188 An argument is a repeat count, as in @code{step}.
5192 @kindex ni @r{(@code{nexti})}
5194 @itemx nexti @var{arg}
5196 Execute one machine instruction, but if it is a function call,
5197 proceed until the function returns.
5199 An argument is a repeat count, as in @code{next}.
5202 @node Skipping Over Functions and Files
5203 @section Skipping Over Functions and Files
5204 @cindex skipping over functions and files
5206 The program you are debugging may contain some functions which are
5207 uninteresting to debug. The @code{skip} comand lets you tell @value{GDBN} to
5208 skip a function or all functions in a file when stepping.
5210 For example, consider the following C function:
5221 Suppose you wish to step into the functions @code{foo} and @code{bar}, but you
5222 are not interested in stepping through @code{boring}. If you run @code{step}
5223 at line 103, you'll enter @code{boring()}, but if you run @code{next}, you'll
5224 step over both @code{foo} and @code{boring}!
5226 One solution is to @code{step} into @code{boring} and use the @code{finish}
5227 command to immediately exit it. But this can become tedious if @code{boring}
5228 is called from many places.
5230 A more flexible solution is to execute @kbd{skip boring}. This instructs
5231 @value{GDBN} never to step into @code{boring}. Now when you execute
5232 @code{step} at line 103, you'll step over @code{boring} and directly into
5235 You can also instruct @value{GDBN} to skip all functions in a file, with, for
5236 example, @code{skip file boring.c}.
5239 @kindex skip function
5240 @item skip @r{[}@var{linespec}@r{]}
5241 @itemx skip function @r{[}@var{linespec}@r{]}
5242 After running this command, the function named by @var{linespec} or the
5243 function containing the line named by @var{linespec} will be skipped over when
5244 stepping. @xref{Specify Location}.
5246 If you do not specify @var{linespec}, the function you're currently debugging
5249 (If you have a function called @code{file} that you want to skip, use
5250 @kbd{skip function file}.)
5253 @item skip file @r{[}@var{filename}@r{]}
5254 After running this command, any function whose source lives in @var{filename}
5255 will be skipped over when stepping.
5257 If you do not specify @var{filename}, functions whose source lives in the file
5258 you're currently debugging will be skipped.
5261 Skips can be listed, deleted, disabled, and enabled, much like breakpoints.
5262 These are the commands for managing your list of skips:
5266 @item info skip @r{[}@var{range}@r{]}
5267 Print details about the specified skip(s). If @var{range} is not specified,
5268 print a table with details about all functions and files marked for skipping.
5269 @code{info skip} prints the following information about each skip:
5273 A number identifying this skip.
5275 The type of this skip, either @samp{function} or @samp{file}.
5276 @item Enabled or Disabled
5277 Enabled skips are marked with @samp{y}. Disabled skips are marked with @samp{n}.
5279 For function skips, this column indicates the address in memory of the function
5280 being skipped. If you've set a function skip on a function which has not yet
5281 been loaded, this field will contain @samp{<PENDING>}. Once a shared library
5282 which has the function is loaded, @code{info skip} will show the function's
5285 For file skips, this field contains the filename being skipped. For functions
5286 skips, this field contains the function name and its line number in the file
5287 where it is defined.
5291 @item skip delete @r{[}@var{range}@r{]}
5292 Delete the specified skip(s). If @var{range} is not specified, delete all
5296 @item skip enable @r{[}@var{range}@r{]}
5297 Enable the specified skip(s). If @var{range} is not specified, enable all
5300 @kindex skip disable
5301 @item skip disable @r{[}@var{range}@r{]}
5302 Disable the specified skip(s). If @var{range} is not specified, disable all
5311 A signal is an asynchronous event that can happen in a program. The
5312 operating system defines the possible kinds of signals, and gives each
5313 kind a name and a number. For example, in Unix @code{SIGINT} is the
5314 signal a program gets when you type an interrupt character (often @kbd{Ctrl-c});
5315 @code{SIGSEGV} is the signal a program gets from referencing a place in
5316 memory far away from all the areas in use; @code{SIGALRM} occurs when
5317 the alarm clock timer goes off (which happens only if your program has
5318 requested an alarm).
5320 @cindex fatal signals
5321 Some signals, including @code{SIGALRM}, are a normal part of the
5322 functioning of your program. Others, such as @code{SIGSEGV}, indicate
5323 errors; these signals are @dfn{fatal} (they kill your program immediately) if the
5324 program has not specified in advance some other way to handle the signal.
5325 @code{SIGINT} does not indicate an error in your program, but it is normally
5326 fatal so it can carry out the purpose of the interrupt: to kill the program.
5328 @value{GDBN} has the ability to detect any occurrence of a signal in your
5329 program. You can tell @value{GDBN} in advance what to do for each kind of
5332 @cindex handling signals
5333 Normally, @value{GDBN} is set up to let the non-erroneous signals like
5334 @code{SIGALRM} be silently passed to your program
5335 (so as not to interfere with their role in the program's functioning)
5336 but to stop your program immediately whenever an error signal happens.
5337 You can change these settings with the @code{handle} command.
5340 @kindex info signals
5344 Print a table of all the kinds of signals and how @value{GDBN} has been told to
5345 handle each one. You can use this to see the signal numbers of all
5346 the defined types of signals.
5348 @item info signals @var{sig}
5349 Similar, but print information only about the specified signal number.
5351 @code{info handle} is an alias for @code{info signals}.
5353 @item catch signal @r{[}@var{signal}@dots{} @r{|} @samp{all}@r{]}
5354 Set a catchpoint for the indicated signals. @xref{Set Catchpoints},
5355 for details about this command.
5358 @item handle @var{signal} @r{[}@var{keywords}@dots{}@r{]}
5359 Change the way @value{GDBN} handles signal @var{signal}. @var{signal}
5360 can be the number of a signal or its name (with or without the
5361 @samp{SIG} at the beginning); a list of signal numbers of the form
5362 @samp{@var{low}-@var{high}}; or the word @samp{all}, meaning all the
5363 known signals. Optional arguments @var{keywords}, described below,
5364 say what change to make.
5368 The keywords allowed by the @code{handle} command can be abbreviated.
5369 Their full names are:
5373 @value{GDBN} should not stop your program when this signal happens. It may
5374 still print a message telling you that the signal has come in.
5377 @value{GDBN} should stop your program when this signal happens. This implies
5378 the @code{print} keyword as well.
5381 @value{GDBN} should print a message when this signal happens.
5384 @value{GDBN} should not mention the occurrence of the signal at all. This
5385 implies the @code{nostop} keyword as well.
5389 @value{GDBN} should allow your program to see this signal; your program
5390 can handle the signal, or else it may terminate if the signal is fatal
5391 and not handled. @code{pass} and @code{noignore} are synonyms.
5395 @value{GDBN} should not allow your program to see this signal.
5396 @code{nopass} and @code{ignore} are synonyms.
5400 When a signal stops your program, the signal is not visible to the
5402 continue. Your program sees the signal then, if @code{pass} is in
5403 effect for the signal in question @emph{at that time}. In other words,
5404 after @value{GDBN} reports a signal, you can use the @code{handle}
5405 command with @code{pass} or @code{nopass} to control whether your
5406 program sees that signal when you continue.
5408 The default is set to @code{nostop}, @code{noprint}, @code{pass} for
5409 non-erroneous signals such as @code{SIGALRM}, @code{SIGWINCH} and
5410 @code{SIGCHLD}, and to @code{stop}, @code{print}, @code{pass} for the
5413 You can also use the @code{signal} command to prevent your program from
5414 seeing a signal, or cause it to see a signal it normally would not see,
5415 or to give it any signal at any time. For example, if your program stopped
5416 due to some sort of memory reference error, you might store correct
5417 values into the erroneous variables and continue, hoping to see more
5418 execution; but your program would probably terminate immediately as
5419 a result of the fatal signal once it saw the signal. To prevent this,
5420 you can continue with @samp{signal 0}. @xref{Signaling, ,Giving your
5423 @cindex extra signal information
5424 @anchor{extra signal information}
5426 On some targets, @value{GDBN} can inspect extra signal information
5427 associated with the intercepted signal, before it is actually
5428 delivered to the program being debugged. This information is exported
5429 by the convenience variable @code{$_siginfo}, and consists of data
5430 that is passed by the kernel to the signal handler at the time of the
5431 receipt of a signal. The data type of the information itself is
5432 target dependent. You can see the data type using the @code{ptype
5433 $_siginfo} command. On Unix systems, it typically corresponds to the
5434 standard @code{siginfo_t} type, as defined in the @file{signal.h}
5437 Here's an example, on a @sc{gnu}/Linux system, printing the stray
5438 referenced address that raised a segmentation fault.
5442 (@value{GDBP}) continue
5443 Program received signal SIGSEGV, Segmentation fault.
5444 0x0000000000400766 in main ()
5446 (@value{GDBP}) ptype $_siginfo
5453 struct @{...@} _kill;
5454 struct @{...@} _timer;
5456 struct @{...@} _sigchld;
5457 struct @{...@} _sigfault;
5458 struct @{...@} _sigpoll;
5461 (@value{GDBP}) ptype $_siginfo._sifields._sigfault
5465 (@value{GDBP}) p $_siginfo._sifields._sigfault.si_addr
5466 $1 = (void *) 0x7ffff7ff7000
5470 Depending on target support, @code{$_siginfo} may also be writable.
5473 @section Stopping and Starting Multi-thread Programs
5475 @cindex stopped threads
5476 @cindex threads, stopped
5478 @cindex continuing threads
5479 @cindex threads, continuing
5481 @value{GDBN} supports debugging programs with multiple threads
5482 (@pxref{Threads,, Debugging Programs with Multiple Threads}). There
5483 are two modes of controlling execution of your program within the
5484 debugger. In the default mode, referred to as @dfn{all-stop mode},
5485 when any thread in your program stops (for example, at a breakpoint
5486 or while being stepped), all other threads in the program are also stopped by
5487 @value{GDBN}. On some targets, @value{GDBN} also supports
5488 @dfn{non-stop mode}, in which other threads can continue to run freely while
5489 you examine the stopped thread in the debugger.
5492 * All-Stop Mode:: All threads stop when GDB takes control
5493 * Non-Stop Mode:: Other threads continue to execute
5494 * Background Execution:: Running your program asynchronously
5495 * Thread-Specific Breakpoints:: Controlling breakpoints
5496 * Interrupted System Calls:: GDB may interfere with system calls
5497 * Observer Mode:: GDB does not alter program behavior
5501 @subsection All-Stop Mode
5503 @cindex all-stop mode
5505 In all-stop mode, whenever your program stops under @value{GDBN} for any reason,
5506 @emph{all} threads of execution stop, not just the current thread. This
5507 allows you to examine the overall state of the program, including
5508 switching between threads, without worrying that things may change
5511 Conversely, whenever you restart the program, @emph{all} threads start
5512 executing. @emph{This is true even when single-stepping} with commands
5513 like @code{step} or @code{next}.
5515 In particular, @value{GDBN} cannot single-step all threads in lockstep.
5516 Since thread scheduling is up to your debugging target's operating
5517 system (not controlled by @value{GDBN}), other threads may
5518 execute more than one statement while the current thread completes a
5519 single step. Moreover, in general other threads stop in the middle of a
5520 statement, rather than at a clean statement boundary, when the program
5523 You might even find your program stopped in another thread after
5524 continuing or even single-stepping. This happens whenever some other
5525 thread runs into a breakpoint, a signal, or an exception before the
5526 first thread completes whatever you requested.
5528 @cindex automatic thread selection
5529 @cindex switching threads automatically
5530 @cindex threads, automatic switching
5531 Whenever @value{GDBN} stops your program, due to a breakpoint or a
5532 signal, it automatically selects the thread where that breakpoint or
5533 signal happened. @value{GDBN} alerts you to the context switch with a
5534 message such as @samp{[Switching to Thread @var{n}]} to identify the
5537 On some OSes, you can modify @value{GDBN}'s default behavior by
5538 locking the OS scheduler to allow only a single thread to run.
5541 @item set scheduler-locking @var{mode}
5542 @cindex scheduler locking mode
5543 @cindex lock scheduler
5544 Set the scheduler locking mode. If it is @code{off}, then there is no
5545 locking and any thread may run at any time. If @code{on}, then only the
5546 current thread may run when the inferior is resumed. The @code{step}
5547 mode optimizes for single-stepping; it prevents other threads
5548 from preempting the current thread while you are stepping, so that
5549 the focus of debugging does not change unexpectedly.
5550 Other threads only rarely (or never) get a chance to run
5551 when you step. They are more likely to run when you @samp{next} over a
5552 function call, and they are completely free to run when you use commands
5553 like @samp{continue}, @samp{until}, or @samp{finish}. However, unless another
5554 thread hits a breakpoint during its timeslice, @value{GDBN} does not change
5555 the current thread away from the thread that you are debugging.
5557 @item show scheduler-locking
5558 Display the current scheduler locking mode.
5561 @cindex resume threads of multiple processes simultaneously
5562 By default, when you issue one of the execution commands such as
5563 @code{continue}, @code{next} or @code{step}, @value{GDBN} allows only
5564 threads of the current inferior to run. For example, if @value{GDBN}
5565 is attached to two inferiors, each with two threads, the
5566 @code{continue} command resumes only the two threads of the current
5567 inferior. This is useful, for example, when you debug a program that
5568 forks and you want to hold the parent stopped (so that, for instance,
5569 it doesn't run to exit), while you debug the child. In other
5570 situations, you may not be interested in inspecting the current state
5571 of any of the processes @value{GDBN} is attached to, and you may want
5572 to resume them all until some breakpoint is hit. In the latter case,
5573 you can instruct @value{GDBN} to allow all threads of all the
5574 inferiors to run with the @w{@code{set schedule-multiple}} command.
5577 @kindex set schedule-multiple
5578 @item set schedule-multiple
5579 Set the mode for allowing threads of multiple processes to be resumed
5580 when an execution command is issued. When @code{on}, all threads of
5581 all processes are allowed to run. When @code{off}, only the threads
5582 of the current process are resumed. The default is @code{off}. The
5583 @code{scheduler-locking} mode takes precedence when set to @code{on},
5584 or while you are stepping and set to @code{step}.
5586 @item show schedule-multiple
5587 Display the current mode for resuming the execution of threads of
5592 @subsection Non-Stop Mode
5594 @cindex non-stop mode
5596 @c This section is really only a place-holder, and needs to be expanded
5597 @c with more details.
5599 For some multi-threaded targets, @value{GDBN} supports an optional
5600 mode of operation in which you can examine stopped program threads in
5601 the debugger while other threads continue to execute freely. This
5602 minimizes intrusion when debugging live systems, such as programs
5603 where some threads have real-time constraints or must continue to
5604 respond to external events. This is referred to as @dfn{non-stop} mode.
5606 In non-stop mode, when a thread stops to report a debugging event,
5607 @emph{only} that thread is stopped; @value{GDBN} does not stop other
5608 threads as well, in contrast to the all-stop mode behavior. Additionally,
5609 execution commands such as @code{continue} and @code{step} apply by default
5610 only to the current thread in non-stop mode, rather than all threads as
5611 in all-stop mode. This allows you to control threads explicitly in
5612 ways that are not possible in all-stop mode --- for example, stepping
5613 one thread while allowing others to run freely, stepping
5614 one thread while holding all others stopped, or stepping several threads
5615 independently and simultaneously.
5617 To enter non-stop mode, use this sequence of commands before you run
5618 or attach to your program:
5621 # Enable the async interface.
5624 # If using the CLI, pagination breaks non-stop.
5627 # Finally, turn it on!
5631 You can use these commands to manipulate the non-stop mode setting:
5634 @kindex set non-stop
5635 @item set non-stop on
5636 Enable selection of non-stop mode.
5637 @item set non-stop off
5638 Disable selection of non-stop mode.
5639 @kindex show non-stop
5641 Show the current non-stop enablement setting.
5644 Note these commands only reflect whether non-stop mode is enabled,
5645 not whether the currently-executing program is being run in non-stop mode.
5646 In particular, the @code{set non-stop} preference is only consulted when
5647 @value{GDBN} starts or connects to the target program, and it is generally
5648 not possible to switch modes once debugging has started. Furthermore,
5649 since not all targets support non-stop mode, even when you have enabled
5650 non-stop mode, @value{GDBN} may still fall back to all-stop operation by
5653 In non-stop mode, all execution commands apply only to the current thread
5654 by default. That is, @code{continue} only continues one thread.
5655 To continue all threads, issue @code{continue -a} or @code{c -a}.
5657 You can use @value{GDBN}'s background execution commands
5658 (@pxref{Background Execution}) to run some threads in the background
5659 while you continue to examine or step others from @value{GDBN}.
5660 The MI execution commands (@pxref{GDB/MI Program Execution}) are
5661 always executed asynchronously in non-stop mode.
5663 Suspending execution is done with the @code{interrupt} command when
5664 running in the background, or @kbd{Ctrl-c} during foreground execution.
5665 In all-stop mode, this stops the whole process;
5666 but in non-stop mode the interrupt applies only to the current thread.
5667 To stop the whole program, use @code{interrupt -a}.
5669 Other execution commands do not currently support the @code{-a} option.
5671 In non-stop mode, when a thread stops, @value{GDBN} doesn't automatically make
5672 that thread current, as it does in all-stop mode. This is because the
5673 thread stop notifications are asynchronous with respect to @value{GDBN}'s
5674 command interpreter, and it would be confusing if @value{GDBN} unexpectedly
5675 changed to a different thread just as you entered a command to operate on the
5676 previously current thread.
5678 @node Background Execution
5679 @subsection Background Execution
5681 @cindex foreground execution
5682 @cindex background execution
5683 @cindex asynchronous execution
5684 @cindex execution, foreground, background and asynchronous
5686 @value{GDBN}'s execution commands have two variants: the normal
5687 foreground (synchronous) behavior, and a background
5688 (asynchronous) behavior. In foreground execution, @value{GDBN} waits for
5689 the program to report that some thread has stopped before prompting for
5690 another command. In background execution, @value{GDBN} immediately gives
5691 a command prompt so that you can issue other commands while your program runs.
5693 You need to explicitly enable asynchronous mode before you can use
5694 background execution commands. You can use these commands to
5695 manipulate the asynchronous mode setting:
5698 @kindex set target-async
5699 @item set target-async on
5700 Enable asynchronous mode.
5701 @item set target-async off
5702 Disable asynchronous mode.
5703 @kindex show target-async
5704 @item show target-async
5705 Show the current target-async setting.
5708 If the target doesn't support async mode, @value{GDBN} issues an error
5709 message if you attempt to use the background execution commands.
5711 To specify background execution, add a @code{&} to the command. For example,
5712 the background form of the @code{continue} command is @code{continue&}, or
5713 just @code{c&}. The execution commands that accept background execution
5719 @xref{Starting, , Starting your Program}.
5723 @xref{Attach, , Debugging an Already-running Process}.
5727 @xref{Continuing and Stepping, step}.
5731 @xref{Continuing and Stepping, stepi}.
5735 @xref{Continuing and Stepping, next}.
5739 @xref{Continuing and Stepping, nexti}.
5743 @xref{Continuing and Stepping, continue}.
5747 @xref{Continuing and Stepping, finish}.
5751 @xref{Continuing and Stepping, until}.
5755 Background execution is especially useful in conjunction with non-stop
5756 mode for debugging programs with multiple threads; see @ref{Non-Stop Mode}.
5757 However, you can also use these commands in the normal all-stop mode with
5758 the restriction that you cannot issue another execution command until the
5759 previous one finishes. Examples of commands that are valid in all-stop
5760 mode while the program is running include @code{help} and @code{info break}.
5762 You can interrupt your program while it is running in the background by
5763 using the @code{interrupt} command.
5770 Suspend execution of the running program. In all-stop mode,
5771 @code{interrupt} stops the whole process, but in non-stop mode, it stops
5772 only the current thread. To stop the whole program in non-stop mode,
5773 use @code{interrupt -a}.
5776 @node Thread-Specific Breakpoints
5777 @subsection Thread-Specific Breakpoints
5779 When your program has multiple threads (@pxref{Threads,, Debugging
5780 Programs with Multiple Threads}), you can choose whether to set
5781 breakpoints on all threads, or on a particular thread.
5784 @cindex breakpoints and threads
5785 @cindex thread breakpoints
5786 @kindex break @dots{} thread @var{threadno}
5787 @item break @var{linespec} thread @var{threadno}
5788 @itemx break @var{linespec} thread @var{threadno} if @dots{}
5789 @var{linespec} specifies source lines; there are several ways of
5790 writing them (@pxref{Specify Location}), but the effect is always to
5791 specify some source line.
5793 Use the qualifier @samp{thread @var{threadno}} with a breakpoint command
5794 to specify that you only want @value{GDBN} to stop the program when a
5795 particular thread reaches this breakpoint. @var{threadno} is one of the
5796 numeric thread identifiers assigned by @value{GDBN}, shown in the first
5797 column of the @samp{info threads} display.
5799 If you do not specify @samp{thread @var{threadno}} when you set a
5800 breakpoint, the breakpoint applies to @emph{all} threads of your
5803 You can use the @code{thread} qualifier on conditional breakpoints as
5804 well; in this case, place @samp{thread @var{threadno}} before or
5805 after the breakpoint condition, like this:
5808 (@value{GDBP}) break frik.c:13 thread 28 if bartab > lim
5813 @node Interrupted System Calls
5814 @subsection Interrupted System Calls
5816 @cindex thread breakpoints and system calls
5817 @cindex system calls and thread breakpoints
5818 @cindex premature return from system calls
5819 There is an unfortunate side effect when using @value{GDBN} to debug
5820 multi-threaded programs. If one thread stops for a
5821 breakpoint, or for some other reason, and another thread is blocked in a
5822 system call, then the system call may return prematurely. This is a
5823 consequence of the interaction between multiple threads and the signals
5824 that @value{GDBN} uses to implement breakpoints and other events that
5827 To handle this problem, your program should check the return value of
5828 each system call and react appropriately. This is good programming
5831 For example, do not write code like this:
5837 The call to @code{sleep} will return early if a different thread stops
5838 at a breakpoint or for some other reason.
5840 Instead, write this:
5845 unslept = sleep (unslept);
5848 A system call is allowed to return early, so the system is still
5849 conforming to its specification. But @value{GDBN} does cause your
5850 multi-threaded program to behave differently than it would without
5853 Also, @value{GDBN} uses internal breakpoints in the thread library to
5854 monitor certain events such as thread creation and thread destruction.
5855 When such an event happens, a system call in another thread may return
5856 prematurely, even though your program does not appear to stop.
5859 @subsection Observer Mode
5861 If you want to build on non-stop mode and observe program behavior
5862 without any chance of disruption by @value{GDBN}, you can set
5863 variables to disable all of the debugger's attempts to modify state,
5864 whether by writing memory, inserting breakpoints, etc. These operate
5865 at a low level, intercepting operations from all commands.
5867 When all of these are set to @code{off}, then @value{GDBN} is said to
5868 be @dfn{observer mode}. As a convenience, the variable
5869 @code{observer} can be set to disable these, plus enable non-stop
5872 Note that @value{GDBN} will not prevent you from making nonsensical
5873 combinations of these settings. For instance, if you have enabled
5874 @code{may-insert-breakpoints} but disabled @code{may-write-memory},
5875 then breakpoints that work by writing trap instructions into the code
5876 stream will still not be able to be placed.
5881 @item set observer on
5882 @itemx set observer off
5883 When set to @code{on}, this disables all the permission variables
5884 below (except for @code{insert-fast-tracepoints}), plus enables
5885 non-stop debugging. Setting this to @code{off} switches back to
5886 normal debugging, though remaining in non-stop mode.
5889 Show whether observer mode is on or off.
5891 @kindex may-write-registers
5892 @item set may-write-registers on
5893 @itemx set may-write-registers off
5894 This controls whether @value{GDBN} will attempt to alter the values of
5895 registers, such as with assignment expressions in @code{print}, or the
5896 @code{jump} command. It defaults to @code{on}.
5898 @item show may-write-registers
5899 Show the current permission to write registers.
5901 @kindex may-write-memory
5902 @item set may-write-memory on
5903 @itemx set may-write-memory off
5904 This controls whether @value{GDBN} will attempt to alter the contents
5905 of memory, such as with assignment expressions in @code{print}. It
5906 defaults to @code{on}.
5908 @item show may-write-memory
5909 Show the current permission to write memory.
5911 @kindex may-insert-breakpoints
5912 @item set may-insert-breakpoints on
5913 @itemx set may-insert-breakpoints off
5914 This controls whether @value{GDBN} will attempt to insert breakpoints.
5915 This affects all breakpoints, including internal breakpoints defined
5916 by @value{GDBN}. It defaults to @code{on}.
5918 @item show may-insert-breakpoints
5919 Show the current permission to insert breakpoints.
5921 @kindex may-insert-tracepoints
5922 @item set may-insert-tracepoints on
5923 @itemx set may-insert-tracepoints off
5924 This controls whether @value{GDBN} will attempt to insert (regular)
5925 tracepoints at the beginning of a tracing experiment. It affects only
5926 non-fast tracepoints, fast tracepoints being under the control of
5927 @code{may-insert-fast-tracepoints}. It defaults to @code{on}.
5929 @item show may-insert-tracepoints
5930 Show the current permission to insert tracepoints.
5932 @kindex may-insert-fast-tracepoints
5933 @item set may-insert-fast-tracepoints on
5934 @itemx set may-insert-fast-tracepoints off
5935 This controls whether @value{GDBN} will attempt to insert fast
5936 tracepoints at the beginning of a tracing experiment. It affects only
5937 fast tracepoints, regular (non-fast) tracepoints being under the
5938 control of @code{may-insert-tracepoints}. It defaults to @code{on}.
5940 @item show may-insert-fast-tracepoints
5941 Show the current permission to insert fast tracepoints.
5943 @kindex may-interrupt
5944 @item set may-interrupt on
5945 @itemx set may-interrupt off
5946 This controls whether @value{GDBN} will attempt to interrupt or stop
5947 program execution. When this variable is @code{off}, the
5948 @code{interrupt} command will have no effect, nor will
5949 @kbd{Ctrl-c}. It defaults to @code{on}.
5951 @item show may-interrupt
5952 Show the current permission to interrupt or stop the program.
5956 @node Reverse Execution
5957 @chapter Running programs backward
5958 @cindex reverse execution
5959 @cindex running programs backward
5961 When you are debugging a program, it is not unusual to realize that
5962 you have gone too far, and some event of interest has already happened.
5963 If the target environment supports it, @value{GDBN} can allow you to
5964 ``rewind'' the program by running it backward.
5966 A target environment that supports reverse execution should be able
5967 to ``undo'' the changes in machine state that have taken place as the
5968 program was executing normally. Variables, registers etc.@: should
5969 revert to their previous values. Obviously this requires a great
5970 deal of sophistication on the part of the target environment; not
5971 all target environments can support reverse execution.
5973 When a program is executed in reverse, the instructions that
5974 have most recently been executed are ``un-executed'', in reverse
5975 order. The program counter runs backward, following the previous
5976 thread of execution in reverse. As each instruction is ``un-executed'',
5977 the values of memory and/or registers that were changed by that
5978 instruction are reverted to their previous states. After executing
5979 a piece of source code in reverse, all side effects of that code
5980 should be ``undone'', and all variables should be returned to their
5981 prior values@footnote{
5982 Note that some side effects are easier to undo than others. For instance,
5983 memory and registers are relatively easy, but device I/O is hard. Some
5984 targets may be able undo things like device I/O, and some may not.
5986 The contract between @value{GDBN} and the reverse executing target
5987 requires only that the target do something reasonable when
5988 @value{GDBN} tells it to execute backwards, and then report the
5989 results back to @value{GDBN}. Whatever the target reports back to
5990 @value{GDBN}, @value{GDBN} will report back to the user. @value{GDBN}
5991 assumes that the memory and registers that the target reports are in a
5992 consistant state, but @value{GDBN} accepts whatever it is given.
5995 If you are debugging in a target environment that supports
5996 reverse execution, @value{GDBN} provides the following commands.
5999 @kindex reverse-continue
6000 @kindex rc @r{(@code{reverse-continue})}
6001 @item reverse-continue @r{[}@var{ignore-count}@r{]}
6002 @itemx rc @r{[}@var{ignore-count}@r{]}
6003 Beginning at the point where your program last stopped, start executing
6004 in reverse. Reverse execution will stop for breakpoints and synchronous
6005 exceptions (signals), just like normal execution. Behavior of
6006 asynchronous signals depends on the target environment.
6008 @kindex reverse-step
6009 @kindex rs @r{(@code{step})}
6010 @item reverse-step @r{[}@var{count}@r{]}
6011 Run the program backward until control reaches the start of a
6012 different source line; then stop it, and return control to @value{GDBN}.
6014 Like the @code{step} command, @code{reverse-step} will only stop
6015 at the beginning of a source line. It ``un-executes'' the previously
6016 executed source line. If the previous source line included calls to
6017 debuggable functions, @code{reverse-step} will step (backward) into
6018 the called function, stopping at the beginning of the @emph{last}
6019 statement in the called function (typically a return statement).
6021 Also, as with the @code{step} command, if non-debuggable functions are
6022 called, @code{reverse-step} will run thru them backward without stopping.
6024 @kindex reverse-stepi
6025 @kindex rsi @r{(@code{reverse-stepi})}
6026 @item reverse-stepi @r{[}@var{count}@r{]}
6027 Reverse-execute one machine instruction. Note that the instruction
6028 to be reverse-executed is @emph{not} the one pointed to by the program
6029 counter, but the instruction executed prior to that one. For instance,
6030 if the last instruction was a jump, @code{reverse-stepi} will take you
6031 back from the destination of the jump to the jump instruction itself.
6033 @kindex reverse-next
6034 @kindex rn @r{(@code{reverse-next})}
6035 @item reverse-next @r{[}@var{count}@r{]}
6036 Run backward to the beginning of the previous line executed in
6037 the current (innermost) stack frame. If the line contains function
6038 calls, they will be ``un-executed'' without stopping. Starting from
6039 the first line of a function, @code{reverse-next} will take you back
6040 to the caller of that function, @emph{before} the function was called,
6041 just as the normal @code{next} command would take you from the last
6042 line of a function back to its return to its caller
6043 @footnote{Unless the code is too heavily optimized.}.
6045 @kindex reverse-nexti
6046 @kindex rni @r{(@code{reverse-nexti})}
6047 @item reverse-nexti @r{[}@var{count}@r{]}
6048 Like @code{nexti}, @code{reverse-nexti} executes a single instruction
6049 in reverse, except that called functions are ``un-executed'' atomically.
6050 That is, if the previously executed instruction was a return from
6051 another function, @code{reverse-nexti} will continue to execute
6052 in reverse until the call to that function (from the current stack
6055 @kindex reverse-finish
6056 @item reverse-finish
6057 Just as the @code{finish} command takes you to the point where the
6058 current function returns, @code{reverse-finish} takes you to the point
6059 where it was called. Instead of ending up at the end of the current
6060 function invocation, you end up at the beginning.
6062 @kindex set exec-direction
6063 @item set exec-direction
6064 Set the direction of target execution.
6065 @item set exec-direction reverse
6066 @cindex execute forward or backward in time
6067 @value{GDBN} will perform all execution commands in reverse, until the
6068 exec-direction mode is changed to ``forward''. Affected commands include
6069 @code{step, stepi, next, nexti, continue, and finish}. The @code{return}
6070 command cannot be used in reverse mode.
6071 @item set exec-direction forward
6072 @value{GDBN} will perform all execution commands in the normal fashion.
6073 This is the default.
6077 @node Process Record and Replay
6078 @chapter Recording Inferior's Execution and Replaying It
6079 @cindex process record and replay
6080 @cindex recording inferior's execution and replaying it
6082 On some platforms, @value{GDBN} provides a special @dfn{process record
6083 and replay} target that can record a log of the process execution, and
6084 replay it later with both forward and reverse execution commands.
6087 When this target is in use, if the execution log includes the record
6088 for the next instruction, @value{GDBN} will debug in @dfn{replay
6089 mode}. In the replay mode, the inferior does not really execute code
6090 instructions. Instead, all the events that normally happen during
6091 code execution are taken from the execution log. While code is not
6092 really executed in replay mode, the values of registers (including the
6093 program counter register) and the memory of the inferior are still
6094 changed as they normally would. Their contents are taken from the
6098 If the record for the next instruction is not in the execution log,
6099 @value{GDBN} will debug in @dfn{record mode}. In this mode, the
6100 inferior executes normally, and @value{GDBN} records the execution log
6103 The process record and replay target supports reverse execution
6104 (@pxref{Reverse Execution}), even if the platform on which the
6105 inferior runs does not. However, the reverse execution is limited in
6106 this case by the range of the instructions recorded in the execution
6107 log. In other words, reverse execution on platforms that don't
6108 support it directly can only be done in the replay mode.
6110 When debugging in the reverse direction, @value{GDBN} will work in
6111 replay mode as long as the execution log includes the record for the
6112 previous instruction; otherwise, it will work in record mode, if the
6113 platform supports reverse execution, or stop if not.
6115 For architecture environments that support process record and replay,
6116 @value{GDBN} provides the following commands:
6119 @kindex target record
6123 This command starts the process record and replay target. The process
6124 record and replay target can only debug a process that is already
6125 running. Therefore, you need first to start the process with the
6126 @kbd{run} or @kbd{start} commands, and then start the recording with
6127 the @kbd{target record} command.
6129 Both @code{record} and @code{rec} are aliases of @code{target record}.
6131 @cindex displaced stepping, and process record and replay
6132 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6133 will be automatically disabled when process record and replay target
6134 is started. That's because the process record and replay target
6135 doesn't support displaced stepping.
6137 @cindex non-stop mode, and process record and replay
6138 @cindex asynchronous execution, and process record and replay
6139 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6140 the asynchronous execution mode (@pxref{Background Execution}), the
6141 process record and replay target cannot be started because it doesn't
6142 support these two modes.
6147 Stop the process record and replay target. When process record and
6148 replay target stops, the entire execution log will be deleted and the
6149 inferior will either be terminated, or will remain in its final state.
6151 When you stop the process record and replay target in record mode (at
6152 the end of the execution log), the inferior will be stopped at the
6153 next instruction that would have been recorded. In other words, if
6154 you record for a while and then stop recording, the inferior process
6155 will be left in the same state as if the recording never happened.
6157 On the other hand, if the process record and replay target is stopped
6158 while in replay mode (that is, not at the end of the execution log,
6159 but at some earlier point), the inferior process will become ``live''
6160 at that earlier state, and it will then be possible to continue the
6161 usual ``live'' debugging of the process from that state.
6163 When the inferior process exits, or @value{GDBN} detaches from it,
6164 process record and replay target will automatically stop itself.
6167 @item record save @var{filename}
6168 Save the execution log to a file @file{@var{filename}}.
6169 Default filename is @file{gdb_record.@var{process_id}}, where
6170 @var{process_id} is the process ID of the inferior.
6172 @kindex record restore
6173 @item record restore @var{filename}
6174 Restore the execution log from a file @file{@var{filename}}.
6175 File must have been created with @code{record save}.
6177 @kindex set record insn-number-max
6178 @item set record insn-number-max @var{limit}
6179 Set the limit of instructions to be recorded. Default value is 200000.
6181 If @var{limit} is a positive number, then @value{GDBN} will start
6182 deleting instructions from the log once the number of the record
6183 instructions becomes greater than @var{limit}. For every new recorded
6184 instruction, @value{GDBN} will delete the earliest recorded
6185 instruction to keep the number of recorded instructions at the limit.
6186 (Since deleting recorded instructions loses information, @value{GDBN}
6187 lets you control what happens when the limit is reached, by means of
6188 the @code{stop-at-limit} option, described below.)
6190 If @var{limit} is zero, @value{GDBN} will never delete recorded
6191 instructions from the execution log. The number of recorded
6192 instructions is unlimited in this case.
6194 @kindex show record insn-number-max
6195 @item show record insn-number-max
6196 Show the limit of instructions to be recorded.
6198 @kindex set record stop-at-limit
6199 @item set record stop-at-limit
6200 Control the behavior when the number of recorded instructions reaches
6201 the limit. If ON (the default), @value{GDBN} will stop when the limit
6202 is reached for the first time and ask you whether you want to stop the
6203 inferior or continue running it and recording the execution log. If
6204 you decide to continue recording, each new recorded instruction will
6205 cause the oldest one to be deleted.
6207 If this option is OFF, @value{GDBN} will automatically delete the
6208 oldest record to make room for each new one, without asking.
6210 @kindex show record stop-at-limit
6211 @item show record stop-at-limit
6212 Show the current setting of @code{stop-at-limit}.
6214 @kindex set record memory-query
6215 @item set record memory-query
6216 Control the behavior when @value{GDBN} is unable to record memory
6217 changes caused by an instruction. If ON, @value{GDBN} will query
6218 whether to stop the inferior in that case.
6220 If this option is OFF (the default), @value{GDBN} will automatically
6221 ignore the effect of such instructions on memory. Later, when
6222 @value{GDBN} replays this execution log, it will mark the log of this
6223 instruction as not accessible, and it will not affect the replay
6226 @kindex show record memory-query
6227 @item show record memory-query
6228 Show the current setting of @code{memory-query}.
6232 Show various statistics about the state of process record and its
6233 in-memory execution log buffer, including:
6237 Whether in record mode or replay mode.
6239 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6241 Highest recorded instruction number.
6243 Current instruction about to be replayed (if in replay mode).
6245 Number of instructions contained in the execution log.
6247 Maximum number of instructions that may be contained in the execution log.
6250 @kindex record delete
6253 When record target runs in replay mode (``in the past''), delete the
6254 subsequent execution log and begin to record a new execution log starting
6255 from the current address. This means you will abandon the previously
6256 recorded ``future'' and begin recording a new ``future''.
6261 @chapter Examining the Stack
6263 When your program has stopped, the first thing you need to know is where it
6264 stopped and how it got there.
6267 Each time your program performs a function call, information about the call
6269 That information includes the location of the call in your program,
6270 the arguments of the call,
6271 and the local variables of the function being called.
6272 The information is saved in a block of data called a @dfn{stack frame}.
6273 The stack frames are allocated in a region of memory called the @dfn{call
6276 When your program stops, the @value{GDBN} commands for examining the
6277 stack allow you to see all of this information.
6279 @cindex selected frame
6280 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6281 @value{GDBN} commands refer implicitly to the selected frame. In
6282 particular, whenever you ask @value{GDBN} for the value of a variable in
6283 your program, the value is found in the selected frame. There are
6284 special @value{GDBN} commands to select whichever frame you are
6285 interested in. @xref{Selection, ,Selecting a Frame}.
6287 When your program stops, @value{GDBN} automatically selects the
6288 currently executing frame and describes it briefly, similar to the
6289 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6292 * Frames:: Stack frames
6293 * Backtrace:: Backtraces
6294 * Selection:: Selecting a frame
6295 * Frame Info:: Information on a frame
6300 @section Stack Frames
6302 @cindex frame, definition
6304 The call stack is divided up into contiguous pieces called @dfn{stack
6305 frames}, or @dfn{frames} for short; each frame is the data associated
6306 with one call to one function. The frame contains the arguments given
6307 to the function, the function's local variables, and the address at
6308 which the function is executing.
6310 @cindex initial frame
6311 @cindex outermost frame
6312 @cindex innermost frame
6313 When your program is started, the stack has only one frame, that of the
6314 function @code{main}. This is called the @dfn{initial} frame or the
6315 @dfn{outermost} frame. Each time a function is called, a new frame is
6316 made. Each time a function returns, the frame for that function invocation
6317 is eliminated. If a function is recursive, there can be many frames for
6318 the same function. The frame for the function in which execution is
6319 actually occurring is called the @dfn{innermost} frame. This is the most
6320 recently created of all the stack frames that still exist.
6322 @cindex frame pointer
6323 Inside your program, stack frames are identified by their addresses. A
6324 stack frame consists of many bytes, each of which has its own address; each
6325 kind of computer has a convention for choosing one byte whose
6326 address serves as the address of the frame. Usually this address is kept
6327 in a register called the @dfn{frame pointer register}
6328 (@pxref{Registers, $fp}) while execution is going on in that frame.
6330 @cindex frame number
6331 @value{GDBN} assigns numbers to all existing stack frames, starting with
6332 zero for the innermost frame, one for the frame that called it,
6333 and so on upward. These numbers do not really exist in your program;
6334 they are assigned by @value{GDBN} to give you a way of designating stack
6335 frames in @value{GDBN} commands.
6337 @c The -fomit-frame-pointer below perennially causes hbox overflow
6338 @c underflow problems.
6339 @cindex frameless execution
6340 Some compilers provide a way to compile functions so that they operate
6341 without stack frames. (For example, the @value{NGCC} option
6343 @samp{-fomit-frame-pointer}
6345 generates functions without a frame.)
6346 This is occasionally done with heavily used library functions to save
6347 the frame setup time. @value{GDBN} has limited facilities for dealing
6348 with these function invocations. If the innermost function invocation
6349 has no stack frame, @value{GDBN} nevertheless regards it as though
6350 it had a separate frame, which is numbered zero as usual, allowing
6351 correct tracing of the function call chain. However, @value{GDBN} has
6352 no provision for frameless functions elsewhere in the stack.
6355 @kindex frame@r{, command}
6356 @cindex current stack frame
6357 @item frame @var{args}
6358 The @code{frame} command allows you to move from one stack frame to another,
6359 and to print the stack frame you select. @var{args} may be either the
6360 address of the frame or the stack frame number. Without an argument,
6361 @code{frame} prints the current stack frame.
6363 @kindex select-frame
6364 @cindex selecting frame silently
6366 The @code{select-frame} command allows you to move from one stack frame
6367 to another without printing the frame. This is the silent version of
6375 @cindex call stack traces
6376 A backtrace is a summary of how your program got where it is. It shows one
6377 line per frame, for many frames, starting with the currently executing
6378 frame (frame zero), followed by its caller (frame one), and on up the
6383 @kindex bt @r{(@code{backtrace})}
6386 Print a backtrace of the entire stack: one line per frame for all
6387 frames in the stack.
6389 You can stop the backtrace at any time by typing the system interrupt
6390 character, normally @kbd{Ctrl-c}.
6392 @item backtrace @var{n}
6394 Similar, but print only the innermost @var{n} frames.
6396 @item backtrace -@var{n}
6398 Similar, but print only the outermost @var{n} frames.
6400 @item backtrace full
6402 @itemx bt full @var{n}
6403 @itemx bt full -@var{n}
6404 Print the values of the local variables also. @var{n} specifies the
6405 number of frames to print, as described above.
6410 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6411 are additional aliases for @code{backtrace}.
6413 @cindex multiple threads, backtrace
6414 In a multi-threaded program, @value{GDBN} by default shows the
6415 backtrace only for the current thread. To display the backtrace for
6416 several or all of the threads, use the command @code{thread apply}
6417 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6418 apply all backtrace}, @value{GDBN} will display the backtrace for all
6419 the threads; this is handy when you debug a core dump of a
6420 multi-threaded program.
6422 Each line in the backtrace shows the frame number and the function name.
6423 The program counter value is also shown---unless you use @code{set
6424 print address off}. The backtrace also shows the source file name and
6425 line number, as well as the arguments to the function. The program
6426 counter value is omitted if it is at the beginning of the code for that
6429 Here is an example of a backtrace. It was made with the command
6430 @samp{bt 3}, so it shows the innermost three frames.
6434 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6436 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6437 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6439 (More stack frames follow...)
6444 The display for frame zero does not begin with a program counter
6445 value, indicating that your program has stopped at the beginning of the
6446 code for line @code{993} of @code{builtin.c}.
6449 The value of parameter @code{data} in frame 1 has been replaced by
6450 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6451 only if it is a scalar (integer, pointer, enumeration, etc). See command
6452 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6453 on how to configure the way function parameter values are printed.
6455 @cindex optimized out, in backtrace
6456 @cindex function call arguments, optimized out
6457 If your program was compiled with optimizations, some compilers will
6458 optimize away arguments passed to functions if those arguments are
6459 never used after the call. Such optimizations generate code that
6460 passes arguments through registers, but doesn't store those arguments
6461 in the stack frame. @value{GDBN} has no way of displaying such
6462 arguments in stack frames other than the innermost one. Here's what
6463 such a backtrace might look like:
6467 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6469 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6470 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6472 (More stack frames follow...)
6477 The values of arguments that were not saved in their stack frames are
6478 shown as @samp{<optimized out>}.
6480 If you need to display the values of such optimized-out arguments,
6481 either deduce that from other variables whose values depend on the one
6482 you are interested in, or recompile without optimizations.
6484 @cindex backtrace beyond @code{main} function
6485 @cindex program entry point
6486 @cindex startup code, and backtrace
6487 Most programs have a standard user entry point---a place where system
6488 libraries and startup code transition into user code. For C this is
6489 @code{main}@footnote{
6490 Note that embedded programs (the so-called ``free-standing''
6491 environment) are not required to have a @code{main} function as the
6492 entry point. They could even have multiple entry points.}.
6493 When @value{GDBN} finds the entry function in a backtrace
6494 it will terminate the backtrace, to avoid tracing into highly
6495 system-specific (and generally uninteresting) code.
6497 If you need to examine the startup code, or limit the number of levels
6498 in a backtrace, you can change this behavior:
6501 @item set backtrace past-main
6502 @itemx set backtrace past-main on
6503 @kindex set backtrace
6504 Backtraces will continue past the user entry point.
6506 @item set backtrace past-main off
6507 Backtraces will stop when they encounter the user entry point. This is the
6510 @item show backtrace past-main
6511 @kindex show backtrace
6512 Display the current user entry point backtrace policy.
6514 @item set backtrace past-entry
6515 @itemx set backtrace past-entry on
6516 Backtraces will continue past the internal entry point of an application.
6517 This entry point is encoded by the linker when the application is built,
6518 and is likely before the user entry point @code{main} (or equivalent) is called.
6520 @item set backtrace past-entry off
6521 Backtraces will stop when they encounter the internal entry point of an
6522 application. This is the default.
6524 @item show backtrace past-entry
6525 Display the current internal entry point backtrace policy.
6527 @item set backtrace limit @var{n}
6528 @itemx set backtrace limit 0
6529 @cindex backtrace limit
6530 Limit the backtrace to @var{n} levels. A value of zero means
6533 @item show backtrace limit
6534 Display the current limit on backtrace levels.
6537 You can control how file names are displayed.
6540 @item set filename-display
6541 @itemx set filename-display relative
6542 @cindex filename-display
6543 Display file names relative to the compilation directory. This is the default.
6545 @item set filename-display basename
6546 Display only basename of a filename.
6548 @item set filename-display absolute
6549 Display an absolute filename.
6551 @item show filename-display
6552 Show the current way to display filenames.
6556 @section Selecting a Frame
6558 Most commands for examining the stack and other data in your program work on
6559 whichever stack frame is selected at the moment. Here are the commands for
6560 selecting a stack frame; all of them finish by printing a brief description
6561 of the stack frame just selected.
6564 @kindex frame@r{, selecting}
6565 @kindex f @r{(@code{frame})}
6568 Select frame number @var{n}. Recall that frame zero is the innermost
6569 (currently executing) frame, frame one is the frame that called the
6570 innermost one, and so on. The highest-numbered frame is the one for
6573 @item frame @var{addr}
6575 Select the frame at address @var{addr}. This is useful mainly if the
6576 chaining of stack frames has been damaged by a bug, making it
6577 impossible for @value{GDBN} to assign numbers properly to all frames. In
6578 addition, this can be useful when your program has multiple stacks and
6579 switches between them.
6581 On the SPARC architecture, @code{frame} needs two addresses to
6582 select an arbitrary frame: a frame pointer and a stack pointer.
6584 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6585 pointer and a program counter.
6587 On the 29k architecture, it needs three addresses: a register stack
6588 pointer, a program counter, and a memory stack pointer.
6592 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6593 advances toward the outermost frame, to higher frame numbers, to frames
6594 that have existed longer. @var{n} defaults to one.
6597 @kindex do @r{(@code{down})}
6599 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6600 advances toward the innermost frame, to lower frame numbers, to frames
6601 that were created more recently. @var{n} defaults to one. You may
6602 abbreviate @code{down} as @code{do}.
6605 All of these commands end by printing two lines of output describing the
6606 frame. The first line shows the frame number, the function name, the
6607 arguments, and the source file and line number of execution in that
6608 frame. The second line shows the text of that source line.
6616 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6618 10 read_input_file (argv[i]);
6622 After such a printout, the @code{list} command with no arguments
6623 prints ten lines centered on the point of execution in the frame.
6624 You can also edit the program at the point of execution with your favorite
6625 editing program by typing @code{edit}.
6626 @xref{List, ,Printing Source Lines},
6630 @kindex down-silently
6632 @item up-silently @var{n}
6633 @itemx down-silently @var{n}
6634 These two commands are variants of @code{up} and @code{down},
6635 respectively; they differ in that they do their work silently, without
6636 causing display of the new frame. They are intended primarily for use
6637 in @value{GDBN} command scripts, where the output might be unnecessary and
6642 @section Information About a Frame
6644 There are several other commands to print information about the selected
6650 When used without any argument, this command does not change which
6651 frame is selected, but prints a brief description of the currently
6652 selected stack frame. It can be abbreviated @code{f}. With an
6653 argument, this command is used to select a stack frame.
6654 @xref{Selection, ,Selecting a Frame}.
6657 @kindex info f @r{(@code{info frame})}
6660 This command prints a verbose description of the selected stack frame,
6665 the address of the frame
6667 the address of the next frame down (called by this frame)
6669 the address of the next frame up (caller of this frame)
6671 the language in which the source code corresponding to this frame is written
6673 the address of the frame's arguments
6675 the address of the frame's local variables
6677 the program counter saved in it (the address of execution in the caller frame)
6679 which registers were saved in the frame
6682 @noindent The verbose description is useful when
6683 something has gone wrong that has made the stack format fail to fit
6684 the usual conventions.
6686 @item info frame @var{addr}
6687 @itemx info f @var{addr}
6688 Print a verbose description of the frame at address @var{addr}, without
6689 selecting that frame. The selected frame remains unchanged by this
6690 command. This requires the same kind of address (more than one for some
6691 architectures) that you specify in the @code{frame} command.
6692 @xref{Selection, ,Selecting a Frame}.
6696 Print the arguments of the selected frame, each on a separate line.
6700 Print the local variables of the selected frame, each on a separate
6701 line. These are all variables (declared either static or automatic)
6702 accessible at the point of execution of the selected frame.
6708 @chapter Examining Source Files
6710 @value{GDBN} can print parts of your program's source, since the debugging
6711 information recorded in the program tells @value{GDBN} what source files were
6712 used to build it. When your program stops, @value{GDBN} spontaneously prints
6713 the line where it stopped. Likewise, when you select a stack frame
6714 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6715 execution in that frame has stopped. You can print other portions of
6716 source files by explicit command.
6718 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6719 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6720 @value{GDBN} under @sc{gnu} Emacs}.
6723 * List:: Printing source lines
6724 * Specify Location:: How to specify code locations
6725 * Edit:: Editing source files
6726 * Search:: Searching source files
6727 * Source Path:: Specifying source directories
6728 * Machine Code:: Source and machine code
6732 @section Printing Source Lines
6735 @kindex l @r{(@code{list})}
6736 To print lines from a source file, use the @code{list} command
6737 (abbreviated @code{l}). By default, ten lines are printed.
6738 There are several ways to specify what part of the file you want to
6739 print; see @ref{Specify Location}, for the full list.
6741 Here are the forms of the @code{list} command most commonly used:
6744 @item list @var{linenum}
6745 Print lines centered around line number @var{linenum} in the
6746 current source file.
6748 @item list @var{function}
6749 Print lines centered around the beginning of function
6753 Print more lines. If the last lines printed were printed with a
6754 @code{list} command, this prints lines following the last lines
6755 printed; however, if the last line printed was a solitary line printed
6756 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6757 Stack}), this prints lines centered around that line.
6760 Print lines just before the lines last printed.
6763 @cindex @code{list}, how many lines to display
6764 By default, @value{GDBN} prints ten source lines with any of these forms of
6765 the @code{list} command. You can change this using @code{set listsize}:
6768 @kindex set listsize
6769 @item set listsize @var{count}
6770 Make the @code{list} command display @var{count} source lines (unless
6771 the @code{list} argument explicitly specifies some other number).
6772 Setting @var{count} to -1 means there's no limit and 0 means suppress
6773 display of source lines.
6775 @kindex show listsize
6777 Display the number of lines that @code{list} prints.
6780 Repeating a @code{list} command with @key{RET} discards the argument,
6781 so it is equivalent to typing just @code{list}. This is more useful
6782 than listing the same lines again. An exception is made for an
6783 argument of @samp{-}; that argument is preserved in repetition so that
6784 each repetition moves up in the source file.
6786 In general, the @code{list} command expects you to supply zero, one or two
6787 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6788 of writing them (@pxref{Specify Location}), but the effect is always
6789 to specify some source line.
6791 Here is a complete description of the possible arguments for @code{list}:
6794 @item list @var{linespec}
6795 Print lines centered around the line specified by @var{linespec}.
6797 @item list @var{first},@var{last}
6798 Print lines from @var{first} to @var{last}. Both arguments are
6799 linespecs. When a @code{list} command has two linespecs, and the
6800 source file of the second linespec is omitted, this refers to
6801 the same source file as the first linespec.
6803 @item list ,@var{last}
6804 Print lines ending with @var{last}.
6806 @item list @var{first},
6807 Print lines starting with @var{first}.
6810 Print lines just after the lines last printed.
6813 Print lines just before the lines last printed.
6816 As described in the preceding table.
6819 @node Specify Location
6820 @section Specifying a Location
6821 @cindex specifying location
6824 Several @value{GDBN} commands accept arguments that specify a location
6825 of your program's code. Since @value{GDBN} is a source-level
6826 debugger, a location usually specifies some line in the source code;
6827 for that reason, locations are also known as @dfn{linespecs}.
6829 Here are all the different ways of specifying a code location that
6830 @value{GDBN} understands:
6834 Specifies the line number @var{linenum} of the current source file.
6837 @itemx +@var{offset}
6838 Specifies the line @var{offset} lines before or after the @dfn{current
6839 line}. For the @code{list} command, the current line is the last one
6840 printed; for the breakpoint commands, this is the line at which
6841 execution stopped in the currently selected @dfn{stack frame}
6842 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6843 used as the second of the two linespecs in a @code{list} command,
6844 this specifies the line @var{offset} lines up or down from the first
6847 @item @var{filename}:@var{linenum}
6848 Specifies the line @var{linenum} in the source file @var{filename}.
6849 If @var{filename} is a relative file name, then it will match any
6850 source file name with the same trailing components. For example, if
6851 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6852 name of @file{/build/trunk/gcc/expr.c}, but not
6853 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
6855 @item @var{function}
6856 Specifies the line that begins the body of the function @var{function}.
6857 For example, in C, this is the line with the open brace.
6859 @item @var{function}:@var{label}
6860 Specifies the line where @var{label} appears in @var{function}.
6862 @item @var{filename}:@var{function}
6863 Specifies the line that begins the body of the function @var{function}
6864 in the file @var{filename}. You only need the file name with a
6865 function name to avoid ambiguity when there are identically named
6866 functions in different source files.
6869 Specifies the line at which the label named @var{label} appears.
6870 @value{GDBN} searches for the label in the function corresponding to
6871 the currently selected stack frame. If there is no current selected
6872 stack frame (for instance, if the inferior is not running), then
6873 @value{GDBN} will not search for a label.
6875 @item *@var{address}
6876 Specifies the program address @var{address}. For line-oriented
6877 commands, such as @code{list} and @code{edit}, this specifies a source
6878 line that contains @var{address}. For @code{break} and other
6879 breakpoint oriented commands, this can be used to set breakpoints in
6880 parts of your program which do not have debugging information or
6883 Here @var{address} may be any expression valid in the current working
6884 language (@pxref{Languages, working language}) that specifies a code
6885 address. In addition, as a convenience, @value{GDBN} extends the
6886 semantics of expressions used in locations to cover the situations
6887 that frequently happen during debugging. Here are the various forms
6891 @item @var{expression}
6892 Any expression valid in the current working language.
6894 @item @var{funcaddr}
6895 An address of a function or procedure derived from its name. In C,
6896 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
6897 simply the function's name @var{function} (and actually a special case
6898 of a valid expression). In Pascal and Modula-2, this is
6899 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
6900 (although the Pascal form also works).
6902 This form specifies the address of the function's first instruction,
6903 before the stack frame and arguments have been set up.
6905 @item '@var{filename}'::@var{funcaddr}
6906 Like @var{funcaddr} above, but also specifies the name of the source
6907 file explicitly. This is useful if the name of the function does not
6908 specify the function unambiguously, e.g., if there are several
6909 functions with identical names in different source files.
6912 @cindex breakpoint at static probe point
6913 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
6914 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
6915 applications to embed static probes. @xref{Static Probe Points}, for more
6916 information on finding and using static probes. This form of linespec
6917 specifies the location of such a static probe.
6919 If @var{objfile} is given, only probes coming from that shared library
6920 or executable matching @var{objfile} as a regular expression are considered.
6921 If @var{provider} is given, then only probes from that provider are considered.
6922 If several probes match the spec, @value{GDBN} will insert a breakpoint at
6923 each one of those probes.
6929 @section Editing Source Files
6930 @cindex editing source files
6933 @kindex e @r{(@code{edit})}
6934 To edit the lines in a source file, use the @code{edit} command.
6935 The editing program of your choice
6936 is invoked with the current line set to
6937 the active line in the program.
6938 Alternatively, there are several ways to specify what part of the file you
6939 want to print if you want to see other parts of the program:
6942 @item edit @var{location}
6943 Edit the source file specified by @code{location}. Editing starts at
6944 that @var{location}, e.g., at the specified source line of the
6945 specified file. @xref{Specify Location}, for all the possible forms
6946 of the @var{location} argument; here are the forms of the @code{edit}
6947 command most commonly used:
6950 @item edit @var{number}
6951 Edit the current source file with @var{number} as the active line number.
6953 @item edit @var{function}
6954 Edit the file containing @var{function} at the beginning of its definition.
6959 @subsection Choosing your Editor
6960 You can customize @value{GDBN} to use any editor you want
6962 The only restriction is that your editor (say @code{ex}), recognizes the
6963 following command-line syntax:
6965 ex +@var{number} file
6967 The optional numeric value +@var{number} specifies the number of the line in
6968 the file where to start editing.}.
6969 By default, it is @file{@value{EDITOR}}, but you can change this
6970 by setting the environment variable @code{EDITOR} before using
6971 @value{GDBN}. For example, to configure @value{GDBN} to use the
6972 @code{vi} editor, you could use these commands with the @code{sh} shell:
6978 or in the @code{csh} shell,
6980 setenv EDITOR /usr/bin/vi
6985 @section Searching Source Files
6986 @cindex searching source files
6988 There are two commands for searching through the current source file for a
6993 @kindex forward-search
6994 @kindex fo @r{(@code{forward-search})}
6995 @item forward-search @var{regexp}
6996 @itemx search @var{regexp}
6997 The command @samp{forward-search @var{regexp}} checks each line,
6998 starting with the one following the last line listed, for a match for
6999 @var{regexp}. It lists the line that is found. You can use the
7000 synonym @samp{search @var{regexp}} or abbreviate the command name as
7003 @kindex reverse-search
7004 @item reverse-search @var{regexp}
7005 The command @samp{reverse-search @var{regexp}} checks each line, starting
7006 with the one before the last line listed and going backward, for a match
7007 for @var{regexp}. It lists the line that is found. You can abbreviate
7008 this command as @code{rev}.
7012 @section Specifying Source Directories
7015 @cindex directories for source files
7016 Executable programs sometimes do not record the directories of the source
7017 files from which they were compiled, just the names. Even when they do,
7018 the directories could be moved between the compilation and your debugging
7019 session. @value{GDBN} has a list of directories to search for source files;
7020 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7021 it tries all the directories in the list, in the order they are present
7022 in the list, until it finds a file with the desired name.
7024 For example, suppose an executable references the file
7025 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7026 @file{/mnt/cross}. The file is first looked up literally; if this
7027 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7028 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7029 message is printed. @value{GDBN} does not look up the parts of the
7030 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7031 Likewise, the subdirectories of the source path are not searched: if
7032 the source path is @file{/mnt/cross}, and the binary refers to
7033 @file{foo.c}, @value{GDBN} would not find it under
7034 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7036 Plain file names, relative file names with leading directories, file
7037 names containing dots, etc.@: are all treated as described above; for
7038 instance, if the source path is @file{/mnt/cross}, and the source file
7039 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7040 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7041 that---@file{/mnt/cross/foo.c}.
7043 Note that the executable search path is @emph{not} used to locate the
7046 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7047 any information it has cached about where source files are found and where
7048 each line is in the file.
7052 When you start @value{GDBN}, its source path includes only @samp{cdir}
7053 and @samp{cwd}, in that order.
7054 To add other directories, use the @code{directory} command.
7056 The search path is used to find both program source files and @value{GDBN}
7057 script files (read using the @samp{-command} option and @samp{source} command).
7059 In addition to the source path, @value{GDBN} provides a set of commands
7060 that manage a list of source path substitution rules. A @dfn{substitution
7061 rule} specifies how to rewrite source directories stored in the program's
7062 debug information in case the sources were moved to a different
7063 directory between compilation and debugging. A rule is made of
7064 two strings, the first specifying what needs to be rewritten in
7065 the path, and the second specifying how it should be rewritten.
7066 In @ref{set substitute-path}, we name these two parts @var{from} and
7067 @var{to} respectively. @value{GDBN} does a simple string replacement
7068 of @var{from} with @var{to} at the start of the directory part of the
7069 source file name, and uses that result instead of the original file
7070 name to look up the sources.
7072 Using the previous example, suppose the @file{foo-1.0} tree has been
7073 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7074 @value{GDBN} to replace @file{/usr/src} in all source path names with
7075 @file{/mnt/cross}. The first lookup will then be
7076 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7077 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7078 substitution rule, use the @code{set substitute-path} command
7079 (@pxref{set substitute-path}).
7081 To avoid unexpected substitution results, a rule is applied only if the
7082 @var{from} part of the directory name ends at a directory separator.
7083 For instance, a rule substituting @file{/usr/source} into
7084 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7085 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7086 is applied only at the beginning of the directory name, this rule will
7087 not be applied to @file{/root/usr/source/baz.c} either.
7089 In many cases, you can achieve the same result using the @code{directory}
7090 command. However, @code{set substitute-path} can be more efficient in
7091 the case where the sources are organized in a complex tree with multiple
7092 subdirectories. With the @code{directory} command, you need to add each
7093 subdirectory of your project. If you moved the entire tree while
7094 preserving its internal organization, then @code{set substitute-path}
7095 allows you to direct the debugger to all the sources with one single
7098 @code{set substitute-path} is also more than just a shortcut command.
7099 The source path is only used if the file at the original location no
7100 longer exists. On the other hand, @code{set substitute-path} modifies
7101 the debugger behavior to look at the rewritten location instead. So, if
7102 for any reason a source file that is not relevant to your executable is
7103 located at the original location, a substitution rule is the only
7104 method available to point @value{GDBN} at the new location.
7106 @cindex @samp{--with-relocated-sources}
7107 @cindex default source path substitution
7108 You can configure a default source path substitution rule by
7109 configuring @value{GDBN} with the
7110 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7111 should be the name of a directory under @value{GDBN}'s configured
7112 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7113 directory names in debug information under @var{dir} will be adjusted
7114 automatically if the installed @value{GDBN} is moved to a new
7115 location. This is useful if @value{GDBN}, libraries or executables
7116 with debug information and corresponding source code are being moved
7120 @item directory @var{dirname} @dots{}
7121 @item dir @var{dirname} @dots{}
7122 Add directory @var{dirname} to the front of the source path. Several
7123 directory names may be given to this command, separated by @samp{:}
7124 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7125 part of absolute file names) or
7126 whitespace. You may specify a directory that is already in the source
7127 path; this moves it forward, so @value{GDBN} searches it sooner.
7131 @vindex $cdir@r{, convenience variable}
7132 @vindex $cwd@r{, convenience variable}
7133 @cindex compilation directory
7134 @cindex current directory
7135 @cindex working directory
7136 @cindex directory, current
7137 @cindex directory, compilation
7138 You can use the string @samp{$cdir} to refer to the compilation
7139 directory (if one is recorded), and @samp{$cwd} to refer to the current
7140 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7141 tracks the current working directory as it changes during your @value{GDBN}
7142 session, while the latter is immediately expanded to the current
7143 directory at the time you add an entry to the source path.
7146 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7148 @c RET-repeat for @code{directory} is explicitly disabled, but since
7149 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7151 @item set directories @var{path-list}
7152 @kindex set directories
7153 Set the source path to @var{path-list}.
7154 @samp{$cdir:$cwd} are added if missing.
7156 @item show directories
7157 @kindex show directories
7158 Print the source path: show which directories it contains.
7160 @anchor{set substitute-path}
7161 @item set substitute-path @var{from} @var{to}
7162 @kindex set substitute-path
7163 Define a source path substitution rule, and add it at the end of the
7164 current list of existing substitution rules. If a rule with the same
7165 @var{from} was already defined, then the old rule is also deleted.
7167 For example, if the file @file{/foo/bar/baz.c} was moved to
7168 @file{/mnt/cross/baz.c}, then the command
7171 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7175 will tell @value{GDBN} to replace @samp{/usr/src} with
7176 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7177 @file{baz.c} even though it was moved.
7179 In the case when more than one substitution rule have been defined,
7180 the rules are evaluated one by one in the order where they have been
7181 defined. The first one matching, if any, is selected to perform
7184 For instance, if we had entered the following commands:
7187 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7188 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7192 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7193 @file{/mnt/include/defs.h} by using the first rule. However, it would
7194 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7195 @file{/mnt/src/lib/foo.c}.
7198 @item unset substitute-path [path]
7199 @kindex unset substitute-path
7200 If a path is specified, search the current list of substitution rules
7201 for a rule that would rewrite that path. Delete that rule if found.
7202 A warning is emitted by the debugger if no rule could be found.
7204 If no path is specified, then all substitution rules are deleted.
7206 @item show substitute-path [path]
7207 @kindex show substitute-path
7208 If a path is specified, then print the source path substitution rule
7209 which would rewrite that path, if any.
7211 If no path is specified, then print all existing source path substitution
7216 If your source path is cluttered with directories that are no longer of
7217 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7218 versions of source. You can correct the situation as follows:
7222 Use @code{directory} with no argument to reset the source path to its default value.
7225 Use @code{directory} with suitable arguments to reinstall the
7226 directories you want in the source path. You can add all the
7227 directories in one command.
7231 @section Source and Machine Code
7232 @cindex source line and its code address
7234 You can use the command @code{info line} to map source lines to program
7235 addresses (and vice versa), and the command @code{disassemble} to display
7236 a range of addresses as machine instructions. You can use the command
7237 @code{set disassemble-next-line} to set whether to disassemble next
7238 source line when execution stops. When run under @sc{gnu} Emacs
7239 mode, the @code{info line} command causes the arrow to point to the
7240 line specified. Also, @code{info line} prints addresses in symbolic form as
7245 @item info line @var{linespec}
7246 Print the starting and ending addresses of the compiled code for
7247 source line @var{linespec}. You can specify source lines in any of
7248 the ways documented in @ref{Specify Location}.
7251 For example, we can use @code{info line} to discover the location of
7252 the object code for the first line of function
7253 @code{m4_changequote}:
7255 @c FIXME: I think this example should also show the addresses in
7256 @c symbolic form, as they usually would be displayed.
7258 (@value{GDBP}) info line m4_changequote
7259 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7263 @cindex code address and its source line
7264 We can also inquire (using @code{*@var{addr}} as the form for
7265 @var{linespec}) what source line covers a particular address:
7267 (@value{GDBP}) info line *0x63ff
7268 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7271 @cindex @code{$_} and @code{info line}
7272 @cindex @code{x} command, default address
7273 @kindex x@r{(examine), and} info line
7274 After @code{info line}, the default address for the @code{x} command
7275 is changed to the starting address of the line, so that @samp{x/i} is
7276 sufficient to begin examining the machine code (@pxref{Memory,
7277 ,Examining Memory}). Also, this address is saved as the value of the
7278 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7283 @cindex assembly instructions
7284 @cindex instructions, assembly
7285 @cindex machine instructions
7286 @cindex listing machine instructions
7288 @itemx disassemble /m
7289 @itemx disassemble /r
7290 This specialized command dumps a range of memory as machine
7291 instructions. It can also print mixed source+disassembly by specifying
7292 the @code{/m} modifier and print the raw instructions in hex as well as
7293 in symbolic form by specifying the @code{/r}.
7294 The default memory range is the function surrounding the
7295 program counter of the selected frame. A single argument to this
7296 command is a program counter value; @value{GDBN} dumps the function
7297 surrounding this value. When two arguments are given, they should
7298 be separated by a comma, possibly surrounded by whitespace. The
7299 arguments specify a range of addresses to dump, in one of two forms:
7302 @item @var{start},@var{end}
7303 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7304 @item @var{start},+@var{length}
7305 the addresses from @var{start} (inclusive) to
7306 @code{@var{start}+@var{length}} (exclusive).
7310 When 2 arguments are specified, the name of the function is also
7311 printed (since there could be several functions in the given range).
7313 The argument(s) can be any expression yielding a numeric value, such as
7314 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7316 If the range of memory being disassembled contains current program counter,
7317 the instruction at that location is shown with a @code{=>} marker.
7320 The following example shows the disassembly of a range of addresses of
7321 HP PA-RISC 2.0 code:
7324 (@value{GDBP}) disas 0x32c4, 0x32e4
7325 Dump of assembler code from 0x32c4 to 0x32e4:
7326 0x32c4 <main+204>: addil 0,dp
7327 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7328 0x32cc <main+212>: ldil 0x3000,r31
7329 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7330 0x32d4 <main+220>: ldo 0(r31),rp
7331 0x32d8 <main+224>: addil -0x800,dp
7332 0x32dc <main+228>: ldo 0x588(r1),r26
7333 0x32e0 <main+232>: ldil 0x3000,r31
7334 End of assembler dump.
7337 Here is an example showing mixed source+assembly for Intel x86, when the
7338 program is stopped just after function prologue:
7341 (@value{GDBP}) disas /m main
7342 Dump of assembler code for function main:
7344 0x08048330 <+0>: push %ebp
7345 0x08048331 <+1>: mov %esp,%ebp
7346 0x08048333 <+3>: sub $0x8,%esp
7347 0x08048336 <+6>: and $0xfffffff0,%esp
7348 0x08048339 <+9>: sub $0x10,%esp
7350 6 printf ("Hello.\n");
7351 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7352 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7356 0x08048348 <+24>: mov $0x0,%eax
7357 0x0804834d <+29>: leave
7358 0x0804834e <+30>: ret
7360 End of assembler dump.
7363 Here is another example showing raw instructions in hex for AMD x86-64,
7366 (gdb) disas /r 0x400281,+10
7367 Dump of assembler code from 0x400281 to 0x40028b:
7368 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7369 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7370 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7371 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7372 End of assembler dump.
7375 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7376 So, for example, if you want to disassemble function @code{bar}
7377 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7378 and not @samp{disassemble foo.c:bar}.
7380 Some architectures have more than one commonly-used set of instruction
7381 mnemonics or other syntax.
7383 For programs that were dynamically linked and use shared libraries,
7384 instructions that call functions or branch to locations in the shared
7385 libraries might show a seemingly bogus location---it's actually a
7386 location of the relocation table. On some architectures, @value{GDBN}
7387 might be able to resolve these to actual function names.
7390 @kindex set disassembly-flavor
7391 @cindex Intel disassembly flavor
7392 @cindex AT&T disassembly flavor
7393 @item set disassembly-flavor @var{instruction-set}
7394 Select the instruction set to use when disassembling the
7395 program via the @code{disassemble} or @code{x/i} commands.
7397 Currently this command is only defined for the Intel x86 family. You
7398 can set @var{instruction-set} to either @code{intel} or @code{att}.
7399 The default is @code{att}, the AT&T flavor used by default by Unix
7400 assemblers for x86-based targets.
7402 @kindex show disassembly-flavor
7403 @item show disassembly-flavor
7404 Show the current setting of the disassembly flavor.
7408 @kindex set disassemble-next-line
7409 @kindex show disassemble-next-line
7410 @item set disassemble-next-line
7411 @itemx show disassemble-next-line
7412 Control whether or not @value{GDBN} will disassemble the next source
7413 line or instruction when execution stops. If ON, @value{GDBN} will
7414 display disassembly of the next source line when execution of the
7415 program being debugged stops. This is @emph{in addition} to
7416 displaying the source line itself, which @value{GDBN} always does if
7417 possible. If the next source line cannot be displayed for some reason
7418 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7419 info in the debug info), @value{GDBN} will display disassembly of the
7420 next @emph{instruction} instead of showing the next source line. If
7421 AUTO, @value{GDBN} will display disassembly of next instruction only
7422 if the source line cannot be displayed. This setting causes
7423 @value{GDBN} to display some feedback when you step through a function
7424 with no line info or whose source file is unavailable. The default is
7425 OFF, which means never display the disassembly of the next line or
7431 @chapter Examining Data
7433 @cindex printing data
7434 @cindex examining data
7437 The usual way to examine data in your program is with the @code{print}
7438 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7439 evaluates and prints the value of an expression of the language your
7440 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7441 Different Languages}). It may also print the expression using a
7442 Python-based pretty-printer (@pxref{Pretty Printing}).
7445 @item print @var{expr}
7446 @itemx print /@var{f} @var{expr}
7447 @var{expr} is an expression (in the source language). By default the
7448 value of @var{expr} is printed in a format appropriate to its data type;
7449 you can choose a different format by specifying @samp{/@var{f}}, where
7450 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7454 @itemx print /@var{f}
7455 @cindex reprint the last value
7456 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7457 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7458 conveniently inspect the same value in an alternative format.
7461 A more low-level way of examining data is with the @code{x} command.
7462 It examines data in memory at a specified address and prints it in a
7463 specified format. @xref{Memory, ,Examining Memory}.
7465 If you are interested in information about types, or about how the
7466 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7467 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7470 @cindex exploring hierarchical data structures
7472 Another way of examining values of expressions and type information is
7473 through the Python extension command @code{explore} (available only if
7474 the @value{GDBN} build is configured with @code{--with-python}). It
7475 offers an interactive way to start at the highest level (or, the most
7476 abstract level) of the data type of an expression (or, the data type
7477 itself) and explore all the way down to leaf scalar values/fields
7478 embedded in the higher level data types.
7481 @item explore @var{arg}
7482 @var{arg} is either an expression (in the source language), or a type
7483 visible in the current context of the program being debugged.
7486 The working of the @code{explore} command can be illustrated with an
7487 example. If a data type @code{struct ComplexStruct} is defined in your
7497 struct ComplexStruct
7499 struct SimpleStruct *ss_p;
7505 followed by variable declarations as
7508 struct SimpleStruct ss = @{ 10, 1.11 @};
7509 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7513 then, the value of the variable @code{cs} can be explored using the
7514 @code{explore} command as follows.
7518 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7519 the following fields:
7521 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7522 arr = <Enter 1 to explore this field of type `int [10]'>
7524 Enter the field number of choice:
7528 Since the fields of @code{cs} are not scalar values, you are being
7529 prompted to chose the field you want to explore. Let's say you choose
7530 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7531 pointer, you will be asked if it is pointing to a single value. From
7532 the declaration of @code{cs} above, it is indeed pointing to a single
7533 value, hence you enter @code{y}. If you enter @code{n}, then you will
7534 be asked if it were pointing to an array of values, in which case this
7535 field will be explored as if it were an array.
7538 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7539 Continue exploring it as a pointer to a single value [y/n]: y
7540 The value of `*(cs.ss_p)' is a struct/class of type `struct
7541 SimpleStruct' with the following fields:
7543 i = 10 .. (Value of type `int')
7544 d = 1.1100000000000001 .. (Value of type `double')
7546 Press enter to return to parent value:
7550 If the field @code{arr} of @code{cs} was chosen for exploration by
7551 entering @code{1} earlier, then since it is as array, you will be
7552 prompted to enter the index of the element in the array that you want
7556 `cs.arr' is an array of `int'.
7557 Enter the index of the element you want to explore in `cs.arr': 5
7559 `(cs.arr)[5]' is a scalar value of type `int'.
7563 Press enter to return to parent value:
7566 In general, at any stage of exploration, you can go deeper towards the
7567 leaf values by responding to the prompts appropriately, or hit the
7568 return key to return to the enclosing data structure (the @i{higher}
7569 level data structure).
7571 Similar to exploring values, you can use the @code{explore} command to
7572 explore types. Instead of specifying a value (which is typically a
7573 variable name or an expression valid in the current context of the
7574 program being debugged), you specify a type name. If you consider the
7575 same example as above, your can explore the type
7576 @code{struct ComplexStruct} by passing the argument
7577 @code{struct ComplexStruct} to the @code{explore} command.
7580 (gdb) explore struct ComplexStruct
7584 By responding to the prompts appropriately in the subsequent interactive
7585 session, you can explore the type @code{struct ComplexStruct} in a
7586 manner similar to how the value @code{cs} was explored in the above
7589 The @code{explore} command also has two sub-commands,
7590 @code{explore value} and @code{explore type}. The former sub-command is
7591 a way to explicitly specify that value exploration of the argument is
7592 being invoked, while the latter is a way to explicitly specify that type
7593 exploration of the argument is being invoked.
7596 @item explore value @var{expr}
7597 @cindex explore value
7598 This sub-command of @code{explore} explores the value of the
7599 expression @var{expr} (if @var{expr} is an expression valid in the
7600 current context of the program being debugged). The behavior of this
7601 command is identical to that of the behavior of the @code{explore}
7602 command being passed the argument @var{expr}.
7604 @item explore type @var{arg}
7605 @cindex explore type
7606 This sub-command of @code{explore} explores the type of @var{arg} (if
7607 @var{arg} is a type visible in the current context of program being
7608 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7609 is an expression valid in the current context of the program being
7610 debugged). If @var{arg} is a type, then the behavior of this command is
7611 identical to that of the @code{explore} command being passed the
7612 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7613 this command will be identical to that of the @code{explore} command
7614 being passed the type of @var{arg} as the argument.
7618 * Expressions:: Expressions
7619 * Ambiguous Expressions:: Ambiguous Expressions
7620 * Variables:: Program variables
7621 * Arrays:: Artificial arrays
7622 * Output Formats:: Output formats
7623 * Memory:: Examining memory
7624 * Auto Display:: Automatic display
7625 * Print Settings:: Print settings
7626 * Pretty Printing:: Python pretty printing
7627 * Value History:: Value history
7628 * Convenience Vars:: Convenience variables
7629 * Convenience Funs:: Convenience functions
7630 * Registers:: Registers
7631 * Floating Point Hardware:: Floating point hardware
7632 * Vector Unit:: Vector Unit
7633 * OS Information:: Auxiliary data provided by operating system
7634 * Memory Region Attributes:: Memory region attributes
7635 * Dump/Restore Files:: Copy between memory and a file
7636 * Core File Generation:: Cause a program dump its core
7637 * Character Sets:: Debugging programs that use a different
7638 character set than GDB does
7639 * Caching Remote Data:: Data caching for remote targets
7640 * Searching Memory:: Searching memory for a sequence of bytes
7644 @section Expressions
7647 @code{print} and many other @value{GDBN} commands accept an expression and
7648 compute its value. Any kind of constant, variable or operator defined
7649 by the programming language you are using is valid in an expression in
7650 @value{GDBN}. This includes conditional expressions, function calls,
7651 casts, and string constants. It also includes preprocessor macros, if
7652 you compiled your program to include this information; see
7655 @cindex arrays in expressions
7656 @value{GDBN} supports array constants in expressions input by
7657 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7658 you can use the command @code{print @{1, 2, 3@}} to create an array
7659 of three integers. If you pass an array to a function or assign it
7660 to a program variable, @value{GDBN} copies the array to memory that
7661 is @code{malloc}ed in the target program.
7663 Because C is so widespread, most of the expressions shown in examples in
7664 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7665 Languages}, for information on how to use expressions in other
7668 In this section, we discuss operators that you can use in @value{GDBN}
7669 expressions regardless of your programming language.
7671 @cindex casts, in expressions
7672 Casts are supported in all languages, not just in C, because it is so
7673 useful to cast a number into a pointer in order to examine a structure
7674 at that address in memory.
7675 @c FIXME: casts supported---Mod2 true?
7677 @value{GDBN} supports these operators, in addition to those common
7678 to programming languages:
7682 @samp{@@} is a binary operator for treating parts of memory as arrays.
7683 @xref{Arrays, ,Artificial Arrays}, for more information.
7686 @samp{::} allows you to specify a variable in terms of the file or
7687 function where it is defined. @xref{Variables, ,Program Variables}.
7689 @cindex @{@var{type}@}
7690 @cindex type casting memory
7691 @cindex memory, viewing as typed object
7692 @cindex casts, to view memory
7693 @item @{@var{type}@} @var{addr}
7694 Refers to an object of type @var{type} stored at address @var{addr} in
7695 memory. @var{addr} may be any expression whose value is an integer or
7696 pointer (but parentheses are required around binary operators, just as in
7697 a cast). This construct is allowed regardless of what kind of data is
7698 normally supposed to reside at @var{addr}.
7701 @node Ambiguous Expressions
7702 @section Ambiguous Expressions
7703 @cindex ambiguous expressions
7705 Expressions can sometimes contain some ambiguous elements. For instance,
7706 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7707 a single function name to be defined several times, for application in
7708 different contexts. This is called @dfn{overloading}. Another example
7709 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7710 templates and is typically instantiated several times, resulting in
7711 the same function name being defined in different contexts.
7713 In some cases and depending on the language, it is possible to adjust
7714 the expression to remove the ambiguity. For instance in C@t{++}, you
7715 can specify the signature of the function you want to break on, as in
7716 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7717 qualified name of your function often makes the expression unambiguous
7720 When an ambiguity that needs to be resolved is detected, the debugger
7721 has the capability to display a menu of numbered choices for each
7722 possibility, and then waits for the selection with the prompt @samp{>}.
7723 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7724 aborts the current command. If the command in which the expression was
7725 used allows more than one choice to be selected, the next option in the
7726 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7729 For example, the following session excerpt shows an attempt to set a
7730 breakpoint at the overloaded symbol @code{String::after}.
7731 We choose three particular definitions of that function name:
7733 @c FIXME! This is likely to change to show arg type lists, at least
7736 (@value{GDBP}) b String::after
7739 [2] file:String.cc; line number:867
7740 [3] file:String.cc; line number:860
7741 [4] file:String.cc; line number:875
7742 [5] file:String.cc; line number:853
7743 [6] file:String.cc; line number:846
7744 [7] file:String.cc; line number:735
7746 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7747 Breakpoint 2 at 0xb344: file String.cc, line 875.
7748 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7749 Multiple breakpoints were set.
7750 Use the "delete" command to delete unwanted
7757 @kindex set multiple-symbols
7758 @item set multiple-symbols @var{mode}
7759 @cindex multiple-symbols menu
7761 This option allows you to adjust the debugger behavior when an expression
7764 By default, @var{mode} is set to @code{all}. If the command with which
7765 the expression is used allows more than one choice, then @value{GDBN}
7766 automatically selects all possible choices. For instance, inserting
7767 a breakpoint on a function using an ambiguous name results in a breakpoint
7768 inserted on each possible match. However, if a unique choice must be made,
7769 then @value{GDBN} uses the menu to help you disambiguate the expression.
7770 For instance, printing the address of an overloaded function will result
7771 in the use of the menu.
7773 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7774 when an ambiguity is detected.
7776 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7777 an error due to the ambiguity and the command is aborted.
7779 @kindex show multiple-symbols
7780 @item show multiple-symbols
7781 Show the current value of the @code{multiple-symbols} setting.
7785 @section Program Variables
7787 The most common kind of expression to use is the name of a variable
7790 Variables in expressions are understood in the selected stack frame
7791 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7795 global (or file-static)
7802 visible according to the scope rules of the
7803 programming language from the point of execution in that frame
7806 @noindent This means that in the function
7821 you can examine and use the variable @code{a} whenever your program is
7822 executing within the function @code{foo}, but you can only use or
7823 examine the variable @code{b} while your program is executing inside
7824 the block where @code{b} is declared.
7826 @cindex variable name conflict
7827 There is an exception: you can refer to a variable or function whose
7828 scope is a single source file even if the current execution point is not
7829 in this file. But it is possible to have more than one such variable or
7830 function with the same name (in different source files). If that
7831 happens, referring to that name has unpredictable effects. If you wish,
7832 you can specify a static variable in a particular function or file by
7833 using the colon-colon (@code{::}) notation:
7835 @cindex colon-colon, context for variables/functions
7837 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7838 @cindex @code{::}, context for variables/functions
7841 @var{file}::@var{variable}
7842 @var{function}::@var{variable}
7846 Here @var{file} or @var{function} is the name of the context for the
7847 static @var{variable}. In the case of file names, you can use quotes to
7848 make sure @value{GDBN} parses the file name as a single word---for example,
7849 to print a global value of @code{x} defined in @file{f2.c}:
7852 (@value{GDBP}) p 'f2.c'::x
7855 The @code{::} notation is normally used for referring to
7856 static variables, since you typically disambiguate uses of local variables
7857 in functions by selecting the appropriate frame and using the
7858 simple name of the variable. However, you may also use this notation
7859 to refer to local variables in frames enclosing the selected frame:
7868 process (a); /* Stop here */
7879 For example, if there is a breakpoint at the commented line,
7880 here is what you might see
7881 when the program stops after executing the call @code{bar(0)}:
7886 (@value{GDBP}) p bar::a
7889 #2 0x080483d0 in foo (a=5) at foobar.c:12
7892 (@value{GDBP}) p bar::a
7896 @cindex C@t{++} scope resolution
7897 These uses of @samp{::} are very rarely in conflict with the very similar
7898 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
7899 scope resolution operator in @value{GDBN} expressions.
7900 @c FIXME: Um, so what happens in one of those rare cases where it's in
7903 @cindex wrong values
7904 @cindex variable values, wrong
7905 @cindex function entry/exit, wrong values of variables
7906 @cindex optimized code, wrong values of variables
7908 @emph{Warning:} Occasionally, a local variable may appear to have the
7909 wrong value at certain points in a function---just after entry to a new
7910 scope, and just before exit.
7912 You may see this problem when you are stepping by machine instructions.
7913 This is because, on most machines, it takes more than one instruction to
7914 set up a stack frame (including local variable definitions); if you are
7915 stepping by machine instructions, variables may appear to have the wrong
7916 values until the stack frame is completely built. On exit, it usually
7917 also takes more than one machine instruction to destroy a stack frame;
7918 after you begin stepping through that group of instructions, local
7919 variable definitions may be gone.
7921 This may also happen when the compiler does significant optimizations.
7922 To be sure of always seeing accurate values, turn off all optimization
7925 @cindex ``No symbol "foo" in current context''
7926 Another possible effect of compiler optimizations is to optimize
7927 unused variables out of existence, or assign variables to registers (as
7928 opposed to memory addresses). Depending on the support for such cases
7929 offered by the debug info format used by the compiler, @value{GDBN}
7930 might not be able to display values for such local variables. If that
7931 happens, @value{GDBN} will print a message like this:
7934 No symbol "foo" in current context.
7937 To solve such problems, either recompile without optimizations, or use a
7938 different debug info format, if the compiler supports several such
7939 formats. @xref{Compilation}, for more information on choosing compiler
7940 options. @xref{C, ,C and C@t{++}}, for more information about debug
7941 info formats that are best suited to C@t{++} programs.
7943 If you ask to print an object whose contents are unknown to
7944 @value{GDBN}, e.g., because its data type is not completely specified
7945 by the debug information, @value{GDBN} will say @samp{<incomplete
7946 type>}. @xref{Symbols, incomplete type}, for more about this.
7948 If you append @kbd{@@entry} string to a function parameter name you get its
7949 value at the time the function got called. If the value is not available an
7950 error message is printed. Entry values are available only with some compilers.
7951 Entry values are normally also printed at the function parameter list according
7952 to @ref{set print entry-values}.
7955 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
7961 (gdb) print i@@entry
7965 Strings are identified as arrays of @code{char} values without specified
7966 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
7967 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
7968 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
7969 defines literal string type @code{"char"} as @code{char} without a sign.
7974 signed char var1[] = "A";
7977 You get during debugging
7982 $2 = @{65 'A', 0 '\0'@}
7986 @section Artificial Arrays
7988 @cindex artificial array
7990 @kindex @@@r{, referencing memory as an array}
7991 It is often useful to print out several successive objects of the
7992 same type in memory; a section of an array, or an array of
7993 dynamically determined size for which only a pointer exists in the
7996 You can do this by referring to a contiguous span of memory as an
7997 @dfn{artificial array}, using the binary operator @samp{@@}. The left
7998 operand of @samp{@@} should be the first element of the desired array
7999 and be an individual object. The right operand should be the desired length
8000 of the array. The result is an array value whose elements are all of
8001 the type of the left argument. The first element is actually the left
8002 argument; the second element comes from bytes of memory immediately
8003 following those that hold the first element, and so on. Here is an
8004 example. If a program says
8007 int *array = (int *) malloc (len * sizeof (int));
8011 you can print the contents of @code{array} with
8017 The left operand of @samp{@@} must reside in memory. Array values made
8018 with @samp{@@} in this way behave just like other arrays in terms of
8019 subscripting, and are coerced to pointers when used in expressions.
8020 Artificial arrays most often appear in expressions via the value history
8021 (@pxref{Value History, ,Value History}), after printing one out.
8023 Another way to create an artificial array is to use a cast.
8024 This re-interprets a value as if it were an array.
8025 The value need not be in memory:
8027 (@value{GDBP}) p/x (short[2])0x12345678
8028 $1 = @{0x1234, 0x5678@}
8031 As a convenience, if you leave the array length out (as in
8032 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8033 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8035 (@value{GDBP}) p/x (short[])0x12345678
8036 $2 = @{0x1234, 0x5678@}
8039 Sometimes the artificial array mechanism is not quite enough; in
8040 moderately complex data structures, the elements of interest may not
8041 actually be adjacent---for example, if you are interested in the values
8042 of pointers in an array. One useful work-around in this situation is
8043 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8044 Variables}) as a counter in an expression that prints the first
8045 interesting value, and then repeat that expression via @key{RET}. For
8046 instance, suppose you have an array @code{dtab} of pointers to
8047 structures, and you are interested in the values of a field @code{fv}
8048 in each structure. Here is an example of what you might type:
8058 @node Output Formats
8059 @section Output Formats
8061 @cindex formatted output
8062 @cindex output formats
8063 By default, @value{GDBN} prints a value according to its data type. Sometimes
8064 this is not what you want. For example, you might want to print a number
8065 in hex, or a pointer in decimal. Or you might want to view data in memory
8066 at a certain address as a character string or as an instruction. To do
8067 these things, specify an @dfn{output format} when you print a value.
8069 The simplest use of output formats is to say how to print a value
8070 already computed. This is done by starting the arguments of the
8071 @code{print} command with a slash and a format letter. The format
8072 letters supported are:
8076 Regard the bits of the value as an integer, and print the integer in
8080 Print as integer in signed decimal.
8083 Print as integer in unsigned decimal.
8086 Print as integer in octal.
8089 Print as integer in binary. The letter @samp{t} stands for ``two''.
8090 @footnote{@samp{b} cannot be used because these format letters are also
8091 used with the @code{x} command, where @samp{b} stands for ``byte'';
8092 see @ref{Memory,,Examining Memory}.}
8095 @cindex unknown address, locating
8096 @cindex locate address
8097 Print as an address, both absolute in hexadecimal and as an offset from
8098 the nearest preceding symbol. You can use this format used to discover
8099 where (in what function) an unknown address is located:
8102 (@value{GDBP}) p/a 0x54320
8103 $3 = 0x54320 <_initialize_vx+396>
8107 The command @code{info symbol 0x54320} yields similar results.
8108 @xref{Symbols, info symbol}.
8111 Regard as an integer and print it as a character constant. This
8112 prints both the numerical value and its character representation. The
8113 character representation is replaced with the octal escape @samp{\nnn}
8114 for characters outside the 7-bit @sc{ascii} range.
8116 Without this format, @value{GDBN} displays @code{char},
8117 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8118 constants. Single-byte members of vectors are displayed as integer
8122 Regard the bits of the value as a floating point number and print
8123 using typical floating point syntax.
8126 @cindex printing strings
8127 @cindex printing byte arrays
8128 Regard as a string, if possible. With this format, pointers to single-byte
8129 data are displayed as null-terminated strings and arrays of single-byte data
8130 are displayed as fixed-length strings. Other values are displayed in their
8133 Without this format, @value{GDBN} displays pointers to and arrays of
8134 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8135 strings. Single-byte members of a vector are displayed as an integer
8139 @cindex raw printing
8140 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8141 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8142 Printing}). This typically results in a higher-level display of the
8143 value's contents. The @samp{r} format bypasses any Python
8144 pretty-printer which might exist.
8147 For example, to print the program counter in hex (@pxref{Registers}), type
8154 Note that no space is required before the slash; this is because command
8155 names in @value{GDBN} cannot contain a slash.
8157 To reprint the last value in the value history with a different format,
8158 you can use the @code{print} command with just a format and no
8159 expression. For example, @samp{p/x} reprints the last value in hex.
8162 @section Examining Memory
8164 You can use the command @code{x} (for ``examine'') to examine memory in
8165 any of several formats, independently of your program's data types.
8167 @cindex examining memory
8169 @kindex x @r{(examine memory)}
8170 @item x/@var{nfu} @var{addr}
8173 Use the @code{x} command to examine memory.
8176 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8177 much memory to display and how to format it; @var{addr} is an
8178 expression giving the address where you want to start displaying memory.
8179 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8180 Several commands set convenient defaults for @var{addr}.
8183 @item @var{n}, the repeat count
8184 The repeat count is a decimal integer; the default is 1. It specifies
8185 how much memory (counting by units @var{u}) to display.
8186 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8189 @item @var{f}, the display format
8190 The display format is one of the formats used by @code{print}
8191 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8192 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8193 The default is @samp{x} (hexadecimal) initially. The default changes
8194 each time you use either @code{x} or @code{print}.
8196 @item @var{u}, the unit size
8197 The unit size is any of
8203 Halfwords (two bytes).
8205 Words (four bytes). This is the initial default.
8207 Giant words (eight bytes).
8210 Each time you specify a unit size with @code{x}, that size becomes the
8211 default unit the next time you use @code{x}. For the @samp{i} format,
8212 the unit size is ignored and is normally not written. For the @samp{s} format,
8213 the unit size defaults to @samp{b}, unless it is explicitly given.
8214 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8215 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8216 Note that the results depend on the programming language of the
8217 current compilation unit. If the language is C, the @samp{s}
8218 modifier will use the UTF-16 encoding while @samp{w} will use
8219 UTF-32. The encoding is set by the programming language and cannot
8222 @item @var{addr}, starting display address
8223 @var{addr} is the address where you want @value{GDBN} to begin displaying
8224 memory. The expression need not have a pointer value (though it may);
8225 it is always interpreted as an integer address of a byte of memory.
8226 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8227 @var{addr} is usually just after the last address examined---but several
8228 other commands also set the default address: @code{info breakpoints} (to
8229 the address of the last breakpoint listed), @code{info line} (to the
8230 starting address of a line), and @code{print} (if you use it to display
8231 a value from memory).
8234 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8235 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8236 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8237 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8238 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8240 Since the letters indicating unit sizes are all distinct from the
8241 letters specifying output formats, you do not have to remember whether
8242 unit size or format comes first; either order works. The output
8243 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8244 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8246 Even though the unit size @var{u} is ignored for the formats @samp{s}
8247 and @samp{i}, you might still want to use a count @var{n}; for example,
8248 @samp{3i} specifies that you want to see three machine instructions,
8249 including any operands. For convenience, especially when used with
8250 the @code{display} command, the @samp{i} format also prints branch delay
8251 slot instructions, if any, beyond the count specified, which immediately
8252 follow the last instruction that is within the count. The command
8253 @code{disassemble} gives an alternative way of inspecting machine
8254 instructions; see @ref{Machine Code,,Source and Machine Code}.
8256 All the defaults for the arguments to @code{x} are designed to make it
8257 easy to continue scanning memory with minimal specifications each time
8258 you use @code{x}. For example, after you have inspected three machine
8259 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8260 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8261 the repeat count @var{n} is used again; the other arguments default as
8262 for successive uses of @code{x}.
8264 When examining machine instructions, the instruction at current program
8265 counter is shown with a @code{=>} marker. For example:
8268 (@value{GDBP}) x/5i $pc-6
8269 0x804837f <main+11>: mov %esp,%ebp
8270 0x8048381 <main+13>: push %ecx
8271 0x8048382 <main+14>: sub $0x4,%esp
8272 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8273 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8276 @cindex @code{$_}, @code{$__}, and value history
8277 The addresses and contents printed by the @code{x} command are not saved
8278 in the value history because there is often too much of them and they
8279 would get in the way. Instead, @value{GDBN} makes these values available for
8280 subsequent use in expressions as values of the convenience variables
8281 @code{$_} and @code{$__}. After an @code{x} command, the last address
8282 examined is available for use in expressions in the convenience variable
8283 @code{$_}. The contents of that address, as examined, are available in
8284 the convenience variable @code{$__}.
8286 If the @code{x} command has a repeat count, the address and contents saved
8287 are from the last memory unit printed; this is not the same as the last
8288 address printed if several units were printed on the last line of output.
8290 @cindex remote memory comparison
8291 @cindex verify remote memory image
8292 When you are debugging a program running on a remote target machine
8293 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8294 remote machine's memory against the executable file you downloaded to
8295 the target. The @code{compare-sections} command is provided for such
8299 @kindex compare-sections
8300 @item compare-sections @r{[}@var{section-name}@r{]}
8301 Compare the data of a loadable section @var{section-name} in the
8302 executable file of the program being debugged with the same section in
8303 the remote machine's memory, and report any mismatches. With no
8304 arguments, compares all loadable sections. This command's
8305 availability depends on the target's support for the @code{"qCRC"}
8310 @section Automatic Display
8311 @cindex automatic display
8312 @cindex display of expressions
8314 If you find that you want to print the value of an expression frequently
8315 (to see how it changes), you might want to add it to the @dfn{automatic
8316 display list} so that @value{GDBN} prints its value each time your program stops.
8317 Each expression added to the list is given a number to identify it;
8318 to remove an expression from the list, you specify that number.
8319 The automatic display looks like this:
8323 3: bar[5] = (struct hack *) 0x3804
8327 This display shows item numbers, expressions and their current values. As with
8328 displays you request manually using @code{x} or @code{print}, you can
8329 specify the output format you prefer; in fact, @code{display} decides
8330 whether to use @code{print} or @code{x} depending your format
8331 specification---it uses @code{x} if you specify either the @samp{i}
8332 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8336 @item display @var{expr}
8337 Add the expression @var{expr} to the list of expressions to display
8338 each time your program stops. @xref{Expressions, ,Expressions}.
8340 @code{display} does not repeat if you press @key{RET} again after using it.
8342 @item display/@var{fmt} @var{expr}
8343 For @var{fmt} specifying only a display format and not a size or
8344 count, add the expression @var{expr} to the auto-display list but
8345 arrange to display it each time in the specified format @var{fmt}.
8346 @xref{Output Formats,,Output Formats}.
8348 @item display/@var{fmt} @var{addr}
8349 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8350 number of units, add the expression @var{addr} as a memory address to
8351 be examined each time your program stops. Examining means in effect
8352 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8355 For example, @samp{display/i $pc} can be helpful, to see the machine
8356 instruction about to be executed each time execution stops (@samp{$pc}
8357 is a common name for the program counter; @pxref{Registers, ,Registers}).
8360 @kindex delete display
8362 @item undisplay @var{dnums}@dots{}
8363 @itemx delete display @var{dnums}@dots{}
8364 Remove items from the list of expressions to display. Specify the
8365 numbers of the displays that you want affected with the command
8366 argument @var{dnums}. It can be a single display number, one of the
8367 numbers shown in the first field of the @samp{info display} display;
8368 or it could be a range of display numbers, as in @code{2-4}.
8370 @code{undisplay} does not repeat if you press @key{RET} after using it.
8371 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8373 @kindex disable display
8374 @item disable display @var{dnums}@dots{}
8375 Disable the display of item numbers @var{dnums}. A disabled display
8376 item is not printed automatically, but is not forgotten. It may be
8377 enabled again later. Specify the numbers of the displays that you
8378 want affected with the command argument @var{dnums}. It can be a
8379 single display number, one of the numbers shown in the first field of
8380 the @samp{info display} display; or it could be a range of display
8381 numbers, as in @code{2-4}.
8383 @kindex enable display
8384 @item enable display @var{dnums}@dots{}
8385 Enable display of item numbers @var{dnums}. It becomes effective once
8386 again in auto display of its expression, until you specify otherwise.
8387 Specify the numbers of the displays that you want affected with the
8388 command argument @var{dnums}. It can be a single display number, one
8389 of the numbers shown in the first field of the @samp{info display}
8390 display; or it could be a range of display numbers, as in @code{2-4}.
8393 Display the current values of the expressions on the list, just as is
8394 done when your program stops.
8396 @kindex info display
8398 Print the list of expressions previously set up to display
8399 automatically, each one with its item number, but without showing the
8400 values. This includes disabled expressions, which are marked as such.
8401 It also includes expressions which would not be displayed right now
8402 because they refer to automatic variables not currently available.
8405 @cindex display disabled out of scope
8406 If a display expression refers to local variables, then it does not make
8407 sense outside the lexical context for which it was set up. Such an
8408 expression is disabled when execution enters a context where one of its
8409 variables is not defined. For example, if you give the command
8410 @code{display last_char} while inside a function with an argument
8411 @code{last_char}, @value{GDBN} displays this argument while your program
8412 continues to stop inside that function. When it stops elsewhere---where
8413 there is no variable @code{last_char}---the display is disabled
8414 automatically. The next time your program stops where @code{last_char}
8415 is meaningful, you can enable the display expression once again.
8417 @node Print Settings
8418 @section Print Settings
8420 @cindex format options
8421 @cindex print settings
8422 @value{GDBN} provides the following ways to control how arrays, structures,
8423 and symbols are printed.
8426 These settings are useful for debugging programs in any language:
8430 @item set print address
8431 @itemx set print address on
8432 @cindex print/don't print memory addresses
8433 @value{GDBN} prints memory addresses showing the location of stack
8434 traces, structure values, pointer values, breakpoints, and so forth,
8435 even when it also displays the contents of those addresses. The default
8436 is @code{on}. For example, this is what a stack frame display looks like with
8437 @code{set print address on}:
8442 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8444 530 if (lquote != def_lquote)
8448 @item set print address off
8449 Do not print addresses when displaying their contents. For example,
8450 this is the same stack frame displayed with @code{set print address off}:
8454 (@value{GDBP}) set print addr off
8456 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8457 530 if (lquote != def_lquote)
8461 You can use @samp{set print address off} to eliminate all machine
8462 dependent displays from the @value{GDBN} interface. For example, with
8463 @code{print address off}, you should get the same text for backtraces on
8464 all machines---whether or not they involve pointer arguments.
8467 @item show print address
8468 Show whether or not addresses are to be printed.
8471 When @value{GDBN} prints a symbolic address, it normally prints the
8472 closest earlier symbol plus an offset. If that symbol does not uniquely
8473 identify the address (for example, it is a name whose scope is a single
8474 source file), you may need to clarify. One way to do this is with
8475 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8476 you can set @value{GDBN} to print the source file and line number when
8477 it prints a symbolic address:
8480 @item set print symbol-filename on
8481 @cindex source file and line of a symbol
8482 @cindex symbol, source file and line
8483 Tell @value{GDBN} to print the source file name and line number of a
8484 symbol in the symbolic form of an address.
8486 @item set print symbol-filename off
8487 Do not print source file name and line number of a symbol. This is the
8490 @item show print symbol-filename
8491 Show whether or not @value{GDBN} will print the source file name and
8492 line number of a symbol in the symbolic form of an address.
8495 Another situation where it is helpful to show symbol filenames and line
8496 numbers is when disassembling code; @value{GDBN} shows you the line
8497 number and source file that corresponds to each instruction.
8499 Also, you may wish to see the symbolic form only if the address being
8500 printed is reasonably close to the closest earlier symbol:
8503 @item set print max-symbolic-offset @var{max-offset}
8504 @cindex maximum value for offset of closest symbol
8505 Tell @value{GDBN} to only display the symbolic form of an address if the
8506 offset between the closest earlier symbol and the address is less than
8507 @var{max-offset}. The default is 0, which tells @value{GDBN}
8508 to always print the symbolic form of an address if any symbol precedes it.
8510 @item show print max-symbolic-offset
8511 Ask how large the maximum offset is that @value{GDBN} prints in a
8515 @cindex wild pointer, interpreting
8516 @cindex pointer, finding referent
8517 If you have a pointer and you are not sure where it points, try
8518 @samp{set print symbol-filename on}. Then you can determine the name
8519 and source file location of the variable where it points, using
8520 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8521 For example, here @value{GDBN} shows that a variable @code{ptt} points
8522 at another variable @code{t}, defined in @file{hi2.c}:
8525 (@value{GDBP}) set print symbol-filename on
8526 (@value{GDBP}) p/a ptt
8527 $4 = 0xe008 <t in hi2.c>
8531 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8532 does not show the symbol name and filename of the referent, even with
8533 the appropriate @code{set print} options turned on.
8536 You can also enable @samp{/a}-like formatting all the time using
8537 @samp{set print symbol on}:
8540 @item set print symbol on
8541 Tell @value{GDBN} to print the symbol corresponding to an address, if
8544 @item set print symbol off
8545 Tell @value{GDBN} not to print the symbol corresponding to an
8546 address. In this mode, @value{GDBN} will still print the symbol
8547 corresponding to pointers to functions. This is the default.
8549 @item show print symbol
8550 Show whether @value{GDBN} will display the symbol corresponding to an
8554 Other settings control how different kinds of objects are printed:
8557 @item set print array
8558 @itemx set print array on
8559 @cindex pretty print arrays
8560 Pretty print arrays. This format is more convenient to read,
8561 but uses more space. The default is off.
8563 @item set print array off
8564 Return to compressed format for arrays.
8566 @item show print array
8567 Show whether compressed or pretty format is selected for displaying
8570 @cindex print array indexes
8571 @item set print array-indexes
8572 @itemx set print array-indexes on
8573 Print the index of each element when displaying arrays. May be more
8574 convenient to locate a given element in the array or quickly find the
8575 index of a given element in that printed array. The default is off.
8577 @item set print array-indexes off
8578 Stop printing element indexes when displaying arrays.
8580 @item show print array-indexes
8581 Show whether the index of each element is printed when displaying
8584 @item set print elements @var{number-of-elements}
8585 @cindex number of array elements to print
8586 @cindex limit on number of printed array elements
8587 Set a limit on how many elements of an array @value{GDBN} will print.
8588 If @value{GDBN} is printing a large array, it stops printing after it has
8589 printed the number of elements set by the @code{set print elements} command.
8590 This limit also applies to the display of strings.
8591 When @value{GDBN} starts, this limit is set to 200.
8592 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8594 @item show print elements
8595 Display the number of elements of a large array that @value{GDBN} will print.
8596 If the number is 0, then the printing is unlimited.
8598 @item set print frame-arguments @var{value}
8599 @kindex set print frame-arguments
8600 @cindex printing frame argument values
8601 @cindex print all frame argument values
8602 @cindex print frame argument values for scalars only
8603 @cindex do not print frame argument values
8604 This command allows to control how the values of arguments are printed
8605 when the debugger prints a frame (@pxref{Frames}). The possible
8610 The values of all arguments are printed.
8613 Print the value of an argument only if it is a scalar. The value of more
8614 complex arguments such as arrays, structures, unions, etc, is replaced
8615 by @code{@dots{}}. This is the default. Here is an example where
8616 only scalar arguments are shown:
8619 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8624 None of the argument values are printed. Instead, the value of each argument
8625 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8628 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8633 By default, only scalar arguments are printed. This command can be used
8634 to configure the debugger to print the value of all arguments, regardless
8635 of their type. However, it is often advantageous to not print the value
8636 of more complex parameters. For instance, it reduces the amount of
8637 information printed in each frame, making the backtrace more readable.
8638 Also, it improves performance when displaying Ada frames, because
8639 the computation of large arguments can sometimes be CPU-intensive,
8640 especially in large applications. Setting @code{print frame-arguments}
8641 to @code{scalars} (the default) or @code{none} avoids this computation,
8642 thus speeding up the display of each Ada frame.
8644 @item show print frame-arguments
8645 Show how the value of arguments should be displayed when printing a frame.
8647 @anchor{set print entry-values}
8648 @item set print entry-values @var{value}
8649 @kindex set print entry-values
8650 Set printing of frame argument values at function entry. In some cases
8651 @value{GDBN} can determine the value of function argument which was passed by
8652 the function caller, even if the value was modified inside the called function
8653 and therefore is different. With optimized code, the current value could be
8654 unavailable, but the entry value may still be known.
8656 The default value is @code{default} (see below for its description). Older
8657 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8658 this feature will behave in the @code{default} setting the same way as with the
8661 This functionality is currently supported only by DWARF 2 debugging format and
8662 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8663 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8666 The @var{value} parameter can be one of the following:
8670 Print only actual parameter values, never print values from function entry
8674 #0 different (val=6)
8675 #0 lost (val=<optimized out>)
8677 #0 invalid (val=<optimized out>)
8681 Print only parameter values from function entry point. The actual parameter
8682 values are never printed.
8684 #0 equal (val@@entry=5)
8685 #0 different (val@@entry=5)
8686 #0 lost (val@@entry=5)
8687 #0 born (val@@entry=<optimized out>)
8688 #0 invalid (val@@entry=<optimized out>)
8692 Print only parameter values from function entry point. If value from function
8693 entry point is not known while the actual value is known, print the actual
8694 value for such parameter.
8696 #0 equal (val@@entry=5)
8697 #0 different (val@@entry=5)
8698 #0 lost (val@@entry=5)
8700 #0 invalid (val@@entry=<optimized out>)
8704 Print actual parameter values. If actual parameter value is not known while
8705 value from function entry point is known, print the entry point value for such
8709 #0 different (val=6)
8710 #0 lost (val@@entry=5)
8712 #0 invalid (val=<optimized out>)
8716 Always print both the actual parameter value and its value from function entry
8717 point, even if values of one or both are not available due to compiler
8720 #0 equal (val=5, val@@entry=5)
8721 #0 different (val=6, val@@entry=5)
8722 #0 lost (val=<optimized out>, val@@entry=5)
8723 #0 born (val=10, val@@entry=<optimized out>)
8724 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8728 Print the actual parameter value if it is known and also its value from
8729 function entry point if it is known. If neither is known, print for the actual
8730 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8731 values are known and identical, print the shortened
8732 @code{param=param@@entry=VALUE} notation.
8734 #0 equal (val=val@@entry=5)
8735 #0 different (val=6, val@@entry=5)
8736 #0 lost (val@@entry=5)
8738 #0 invalid (val=<optimized out>)
8742 Always print the actual parameter value. Print also its value from function
8743 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8744 if both values are known and identical, print the shortened
8745 @code{param=param@@entry=VALUE} notation.
8747 #0 equal (val=val@@entry=5)
8748 #0 different (val=6, val@@entry=5)
8749 #0 lost (val=<optimized out>, val@@entry=5)
8751 #0 invalid (val=<optimized out>)
8755 For analysis messages on possible failures of frame argument values at function
8756 entry resolution see @ref{set debug entry-values}.
8758 @item show print entry-values
8759 Show the method being used for printing of frame argument values at function
8762 @item set print repeats
8763 @cindex repeated array elements
8764 Set the threshold for suppressing display of repeated array
8765 elements. When the number of consecutive identical elements of an
8766 array exceeds the threshold, @value{GDBN} prints the string
8767 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8768 identical repetitions, instead of displaying the identical elements
8769 themselves. Setting the threshold to zero will cause all elements to
8770 be individually printed. The default threshold is 10.
8772 @item show print repeats
8773 Display the current threshold for printing repeated identical
8776 @item set print null-stop
8777 @cindex @sc{null} elements in arrays
8778 Cause @value{GDBN} to stop printing the characters of an array when the first
8779 @sc{null} is encountered. This is useful when large arrays actually
8780 contain only short strings.
8783 @item show print null-stop
8784 Show whether @value{GDBN} stops printing an array on the first
8785 @sc{null} character.
8787 @item set print pretty on
8788 @cindex print structures in indented form
8789 @cindex indentation in structure display
8790 Cause @value{GDBN} to print structures in an indented format with one member
8791 per line, like this:
8806 @item set print pretty off
8807 Cause @value{GDBN} to print structures in a compact format, like this:
8811 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8812 meat = 0x54 "Pork"@}
8817 This is the default format.
8819 @item show print pretty
8820 Show which format @value{GDBN} is using to print structures.
8822 @item set print sevenbit-strings on
8823 @cindex eight-bit characters in strings
8824 @cindex octal escapes in strings
8825 Print using only seven-bit characters; if this option is set,
8826 @value{GDBN} displays any eight-bit characters (in strings or
8827 character values) using the notation @code{\}@var{nnn}. This setting is
8828 best if you are working in English (@sc{ascii}) and you use the
8829 high-order bit of characters as a marker or ``meta'' bit.
8831 @item set print sevenbit-strings off
8832 Print full eight-bit characters. This allows the use of more
8833 international character sets, and is the default.
8835 @item show print sevenbit-strings
8836 Show whether or not @value{GDBN} is printing only seven-bit characters.
8838 @item set print union on
8839 @cindex unions in structures, printing
8840 Tell @value{GDBN} to print unions which are contained in structures
8841 and other unions. This is the default setting.
8843 @item set print union off
8844 Tell @value{GDBN} not to print unions which are contained in
8845 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8848 @item show print union
8849 Ask @value{GDBN} whether or not it will print unions which are contained in
8850 structures and other unions.
8852 For example, given the declarations
8855 typedef enum @{Tree, Bug@} Species;
8856 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
8857 typedef enum @{Caterpillar, Cocoon, Butterfly@}
8868 struct thing foo = @{Tree, @{Acorn@}@};
8872 with @code{set print union on} in effect @samp{p foo} would print
8875 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
8879 and with @code{set print union off} in effect it would print
8882 $1 = @{it = Tree, form = @{...@}@}
8886 @code{set print union} affects programs written in C-like languages
8892 These settings are of interest when debugging C@t{++} programs:
8895 @cindex demangling C@t{++} names
8896 @item set print demangle
8897 @itemx set print demangle on
8898 Print C@t{++} names in their source form rather than in the encoded
8899 (``mangled'') form passed to the assembler and linker for type-safe
8900 linkage. The default is on.
8902 @item show print demangle
8903 Show whether C@t{++} names are printed in mangled or demangled form.
8905 @item set print asm-demangle
8906 @itemx set print asm-demangle on
8907 Print C@t{++} names in their source form rather than their mangled form, even
8908 in assembler code printouts such as instruction disassemblies.
8911 @item show print asm-demangle
8912 Show whether C@t{++} names in assembly listings are printed in mangled
8915 @cindex C@t{++} symbol decoding style
8916 @cindex symbol decoding style, C@t{++}
8917 @kindex set demangle-style
8918 @item set demangle-style @var{style}
8919 Choose among several encoding schemes used by different compilers to
8920 represent C@t{++} names. The choices for @var{style} are currently:
8924 Allow @value{GDBN} to choose a decoding style by inspecting your program.
8925 This is the default.
8928 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
8931 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
8934 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
8937 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
8938 @strong{Warning:} this setting alone is not sufficient to allow
8939 debugging @code{cfront}-generated executables. @value{GDBN} would
8940 require further enhancement to permit that.
8943 If you omit @var{style}, you will see a list of possible formats.
8945 @item show demangle-style
8946 Display the encoding style currently in use for decoding C@t{++} symbols.
8948 @item set print object
8949 @itemx set print object on
8950 @cindex derived type of an object, printing
8951 @cindex display derived types
8952 When displaying a pointer to an object, identify the @emph{actual}
8953 (derived) type of the object rather than the @emph{declared} type, using
8954 the virtual function table. Note that the virtual function table is
8955 required---this feature can only work for objects that have run-time
8956 type identification; a single virtual method in the object's declared
8957 type is sufficient. Note that this setting is also taken into account when
8958 working with variable objects via MI (@pxref{GDB/MI}).
8960 @item set print object off
8961 Display only the declared type of objects, without reference to the
8962 virtual function table. This is the default setting.
8964 @item show print object
8965 Show whether actual, or declared, object types are displayed.
8967 @item set print static-members
8968 @itemx set print static-members on
8969 @cindex static members of C@t{++} objects
8970 Print static members when displaying a C@t{++} object. The default is on.
8972 @item set print static-members off
8973 Do not print static members when displaying a C@t{++} object.
8975 @item show print static-members
8976 Show whether C@t{++} static members are printed or not.
8978 @item set print pascal_static-members
8979 @itemx set print pascal_static-members on
8980 @cindex static members of Pascal objects
8981 @cindex Pascal objects, static members display
8982 Print static members when displaying a Pascal object. The default is on.
8984 @item set print pascal_static-members off
8985 Do not print static members when displaying a Pascal object.
8987 @item show print pascal_static-members
8988 Show whether Pascal static members are printed or not.
8990 @c These don't work with HP ANSI C++ yet.
8991 @item set print vtbl
8992 @itemx set print vtbl on
8993 @cindex pretty print C@t{++} virtual function tables
8994 @cindex virtual functions (C@t{++}) display
8995 @cindex VTBL display
8996 Pretty print C@t{++} virtual function tables. The default is off.
8997 (The @code{vtbl} commands do not work on programs compiled with the HP
8998 ANSI C@t{++} compiler (@code{aCC}).)
9000 @item set print vtbl off
9001 Do not pretty print C@t{++} virtual function tables.
9003 @item show print vtbl
9004 Show whether C@t{++} virtual function tables are pretty printed, or not.
9007 @node Pretty Printing
9008 @section Pretty Printing
9010 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9011 Python code. It greatly simplifies the display of complex objects. This
9012 mechanism works for both MI and the CLI.
9015 * Pretty-Printer Introduction:: Introduction to pretty-printers
9016 * Pretty-Printer Example:: An example pretty-printer
9017 * Pretty-Printer Commands:: Pretty-printer commands
9020 @node Pretty-Printer Introduction
9021 @subsection Pretty-Printer Introduction
9023 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9024 registered for the value. If there is then @value{GDBN} invokes the
9025 pretty-printer to print the value. Otherwise the value is printed normally.
9027 Pretty-printers are normally named. This makes them easy to manage.
9028 The @samp{info pretty-printer} command will list all the installed
9029 pretty-printers with their names.
9030 If a pretty-printer can handle multiple data types, then its
9031 @dfn{subprinters} are the printers for the individual data types.
9032 Each such subprinter has its own name.
9033 The format of the name is @var{printer-name};@var{subprinter-name}.
9035 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9036 Typically they are automatically loaded and registered when the corresponding
9037 debug information is loaded, thus making them available without having to
9038 do anything special.
9040 There are three places where a pretty-printer can be registered.
9044 Pretty-printers registered globally are available when debugging
9048 Pretty-printers registered with a program space are available only
9049 when debugging that program.
9050 @xref{Progspaces In Python}, for more details on program spaces in Python.
9053 Pretty-printers registered with an objfile are loaded and unloaded
9054 with the corresponding objfile (e.g., shared library).
9055 @xref{Objfiles In Python}, for more details on objfiles in Python.
9058 @xref{Selecting Pretty-Printers}, for further information on how
9059 pretty-printers are selected,
9061 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9064 @node Pretty-Printer Example
9065 @subsection Pretty-Printer Example
9067 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9070 (@value{GDBP}) print s
9072 static npos = 4294967295,
9074 <std::allocator<char>> = @{
9075 <__gnu_cxx::new_allocator<char>> = @{
9076 <No data fields>@}, <No data fields>
9078 members of std::basic_string<char, std::char_traits<char>,
9079 std::allocator<char> >::_Alloc_hider:
9080 _M_p = 0x804a014 "abcd"
9085 With a pretty-printer for @code{std::string} only the contents are printed:
9088 (@value{GDBP}) print s
9092 @node Pretty-Printer Commands
9093 @subsection Pretty-Printer Commands
9094 @cindex pretty-printer commands
9097 @kindex info pretty-printer
9098 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9099 Print the list of installed pretty-printers.
9100 This includes disabled pretty-printers, which are marked as such.
9102 @var{object-regexp} is a regular expression matching the objects
9103 whose pretty-printers to list.
9104 Objects can be @code{global}, the program space's file
9105 (@pxref{Progspaces In Python}),
9106 and the object files within that program space (@pxref{Objfiles In Python}).
9107 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9108 looks up a printer from these three objects.
9110 @var{name-regexp} is a regular expression matching the name of the printers
9113 @kindex disable pretty-printer
9114 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9115 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9116 A disabled pretty-printer is not forgotten, it may be enabled again later.
9118 @kindex enable pretty-printer
9119 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9120 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9125 Suppose we have three pretty-printers installed: one from library1.so
9126 named @code{foo} that prints objects of type @code{foo}, and
9127 another from library2.so named @code{bar} that prints two types of objects,
9128 @code{bar1} and @code{bar2}.
9131 (gdb) info pretty-printer
9138 (gdb) info pretty-printer library2
9143 (gdb) disable pretty-printer library1
9145 2 of 3 printers enabled
9146 (gdb) info pretty-printer
9153 (gdb) disable pretty-printer library2 bar:bar1
9155 1 of 3 printers enabled
9156 (gdb) info pretty-printer library2
9163 (gdb) disable pretty-printer library2 bar
9165 0 of 3 printers enabled
9166 (gdb) info pretty-printer library2
9175 Note that for @code{bar} the entire printer can be disabled,
9176 as can each individual subprinter.
9179 @section Value History
9181 @cindex value history
9182 @cindex history of values printed by @value{GDBN}
9183 Values printed by the @code{print} command are saved in the @value{GDBN}
9184 @dfn{value history}. This allows you to refer to them in other expressions.
9185 Values are kept until the symbol table is re-read or discarded
9186 (for example with the @code{file} or @code{symbol-file} commands).
9187 When the symbol table changes, the value history is discarded,
9188 since the values may contain pointers back to the types defined in the
9193 @cindex history number
9194 The values printed are given @dfn{history numbers} by which you can
9195 refer to them. These are successive integers starting with one.
9196 @code{print} shows you the history number assigned to a value by
9197 printing @samp{$@var{num} = } before the value; here @var{num} is the
9200 To refer to any previous value, use @samp{$} followed by the value's
9201 history number. The way @code{print} labels its output is designed to
9202 remind you of this. Just @code{$} refers to the most recent value in
9203 the history, and @code{$$} refers to the value before that.
9204 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9205 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9206 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9208 For example, suppose you have just printed a pointer to a structure and
9209 want to see the contents of the structure. It suffices to type
9215 If you have a chain of structures where the component @code{next} points
9216 to the next one, you can print the contents of the next one with this:
9223 You can print successive links in the chain by repeating this
9224 command---which you can do by just typing @key{RET}.
9226 Note that the history records values, not expressions. If the value of
9227 @code{x} is 4 and you type these commands:
9235 then the value recorded in the value history by the @code{print} command
9236 remains 4 even though the value of @code{x} has changed.
9241 Print the last ten values in the value history, with their item numbers.
9242 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9243 values} does not change the history.
9245 @item show values @var{n}
9246 Print ten history values centered on history item number @var{n}.
9249 Print ten history values just after the values last printed. If no more
9250 values are available, @code{show values +} produces no display.
9253 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9254 same effect as @samp{show values +}.
9256 @node Convenience Vars
9257 @section Convenience Variables
9259 @cindex convenience variables
9260 @cindex user-defined variables
9261 @value{GDBN} provides @dfn{convenience variables} that you can use within
9262 @value{GDBN} to hold on to a value and refer to it later. These variables
9263 exist entirely within @value{GDBN}; they are not part of your program, and
9264 setting a convenience variable has no direct effect on further execution
9265 of your program. That is why you can use them freely.
9267 Convenience variables are prefixed with @samp{$}. Any name preceded by
9268 @samp{$} can be used for a convenience variable, unless it is one of
9269 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9270 (Value history references, in contrast, are @emph{numbers} preceded
9271 by @samp{$}. @xref{Value History, ,Value History}.)
9273 You can save a value in a convenience variable with an assignment
9274 expression, just as you would set a variable in your program.
9278 set $foo = *object_ptr
9282 would save in @code{$foo} the value contained in the object pointed to by
9285 Using a convenience variable for the first time creates it, but its
9286 value is @code{void} until you assign a new value. You can alter the
9287 value with another assignment at any time.
9289 Convenience variables have no fixed types. You can assign a convenience
9290 variable any type of value, including structures and arrays, even if
9291 that variable already has a value of a different type. The convenience
9292 variable, when used as an expression, has the type of its current value.
9295 @kindex show convenience
9296 @cindex show all user variables and functions
9297 @item show convenience
9298 Print a list of convenience variables used so far, and their values,
9299 as well as a list of the convenience functions.
9300 Abbreviated @code{show conv}.
9302 @kindex init-if-undefined
9303 @cindex convenience variables, initializing
9304 @item init-if-undefined $@var{variable} = @var{expression}
9305 Set a convenience variable if it has not already been set. This is useful
9306 for user-defined commands that keep some state. It is similar, in concept,
9307 to using local static variables with initializers in C (except that
9308 convenience variables are global). It can also be used to allow users to
9309 override default values used in a command script.
9311 If the variable is already defined then the expression is not evaluated so
9312 any side-effects do not occur.
9315 One of the ways to use a convenience variable is as a counter to be
9316 incremented or a pointer to be advanced. For example, to print
9317 a field from successive elements of an array of structures:
9321 print bar[$i++]->contents
9325 Repeat that command by typing @key{RET}.
9327 Some convenience variables are created automatically by @value{GDBN} and given
9328 values likely to be useful.
9331 @vindex $_@r{, convenience variable}
9333 The variable @code{$_} is automatically set by the @code{x} command to
9334 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9335 commands which provide a default address for @code{x} to examine also
9336 set @code{$_} to that address; these commands include @code{info line}
9337 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9338 except when set by the @code{x} command, in which case it is a pointer
9339 to the type of @code{$__}.
9341 @vindex $__@r{, convenience variable}
9343 The variable @code{$__} is automatically set by the @code{x} command
9344 to the value found in the last address examined. Its type is chosen
9345 to match the format in which the data was printed.
9348 @vindex $_exitcode@r{, convenience variable}
9349 The variable @code{$_exitcode} is automatically set to the exit code when
9350 the program being debugged terminates.
9353 @itemx $_probe_arg0@dots{}$_probe_arg11
9354 Arguments to a static probe. @xref{Static Probe Points}.
9357 @vindex $_sdata@r{, inspect, convenience variable}
9358 The variable @code{$_sdata} contains extra collected static tracepoint
9359 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9360 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9361 if extra static tracepoint data has not been collected.
9364 @vindex $_siginfo@r{, convenience variable}
9365 The variable @code{$_siginfo} contains extra signal information
9366 (@pxref{extra signal information}). Note that @code{$_siginfo}
9367 could be empty, if the application has not yet received any signals.
9368 For example, it will be empty before you execute the @code{run} command.
9371 @vindex $_tlb@r{, convenience variable}
9372 The variable @code{$_tlb} is automatically set when debugging
9373 applications running on MS-Windows in native mode or connected to
9374 gdbserver that supports the @code{qGetTIBAddr} request.
9375 @xref{General Query Packets}.
9376 This variable contains the address of the thread information block.
9380 On HP-UX systems, if you refer to a function or variable name that
9381 begins with a dollar sign, @value{GDBN} searches for a user or system
9382 name first, before it searches for a convenience variable.
9384 @node Convenience Funs
9385 @section Convenience Functions
9387 @cindex convenience functions
9388 @value{GDBN} also supplies some @dfn{convenience functions}. These
9389 have a syntax similar to convenience variables. A convenience
9390 function can be used in an expression just like an ordinary function;
9391 however, a convenience function is implemented internally to
9394 These functions require @value{GDBN} to be configured with
9395 @code{Python} support.
9399 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9400 @findex $_memeq@r{, convenience function}
9401 Returns one if the @var{length} bytes at the addresses given by
9402 @var{buf1} and @var{buf2} are equal.
9403 Otherwise it returns zero.
9405 @item $_regex(@var{str}, @var{regex})
9406 @findex $_regex@r{, convenience function}
9407 Returns one if the string @var{str} matches the regular expression
9408 @var{regex}. Otherwise it returns zero.
9409 The syntax of the regular expression is that specified by @code{Python}'s
9410 regular expression support.
9412 @item $_streq(@var{str1}, @var{str2})
9413 @findex $_streq@r{, convenience function}
9414 Returns one if the strings @var{str1} and @var{str2} are equal.
9415 Otherwise it returns zero.
9417 @item $_strlen(@var{str})
9418 @findex $_strlen@r{, convenience function}
9419 Returns the length of string @var{str}.
9423 @value{GDBN} provides the ability to list and get help on
9424 convenience functions.
9428 @kindex help function
9429 @cindex show all convenience functions
9430 Print a list of all convenience functions.
9437 You can refer to machine register contents, in expressions, as variables
9438 with names starting with @samp{$}. The names of registers are different
9439 for each machine; use @code{info registers} to see the names used on
9443 @kindex info registers
9444 @item info registers
9445 Print the names and values of all registers except floating-point
9446 and vector registers (in the selected stack frame).
9448 @kindex info all-registers
9449 @cindex floating point registers
9450 @item info all-registers
9451 Print the names and values of all registers, including floating-point
9452 and vector registers (in the selected stack frame).
9454 @item info registers @var{regname} @dots{}
9455 Print the @dfn{relativized} value of each specified register @var{regname}.
9456 As discussed in detail below, register values are normally relative to
9457 the selected stack frame. @var{regname} may be any register name valid on
9458 the machine you are using, with or without the initial @samp{$}.
9461 @cindex stack pointer register
9462 @cindex program counter register
9463 @cindex process status register
9464 @cindex frame pointer register
9465 @cindex standard registers
9466 @value{GDBN} has four ``standard'' register names that are available (in
9467 expressions) on most machines---whenever they do not conflict with an
9468 architecture's canonical mnemonics for registers. The register names
9469 @code{$pc} and @code{$sp} are used for the program counter register and
9470 the stack pointer. @code{$fp} is used for a register that contains a
9471 pointer to the current stack frame, and @code{$ps} is used for a
9472 register that contains the processor status. For example,
9473 you could print the program counter in hex with
9480 or print the instruction to be executed next with
9487 or add four to the stack pointer@footnote{This is a way of removing
9488 one word from the stack, on machines where stacks grow downward in
9489 memory (most machines, nowadays). This assumes that the innermost
9490 stack frame is selected; setting @code{$sp} is not allowed when other
9491 stack frames are selected. To pop entire frames off the stack,
9492 regardless of machine architecture, use @code{return};
9493 see @ref{Returning, ,Returning from a Function}.} with
9499 Whenever possible, these four standard register names are available on
9500 your machine even though the machine has different canonical mnemonics,
9501 so long as there is no conflict. The @code{info registers} command
9502 shows the canonical names. For example, on the SPARC, @code{info
9503 registers} displays the processor status register as @code{$psr} but you
9504 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9505 is an alias for the @sc{eflags} register.
9507 @value{GDBN} always considers the contents of an ordinary register as an
9508 integer when the register is examined in this way. Some machines have
9509 special registers which can hold nothing but floating point; these
9510 registers are considered to have floating point values. There is no way
9511 to refer to the contents of an ordinary register as floating point value
9512 (although you can @emph{print} it as a floating point value with
9513 @samp{print/f $@var{regname}}).
9515 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9516 means that the data format in which the register contents are saved by
9517 the operating system is not the same one that your program normally
9518 sees. For example, the registers of the 68881 floating point
9519 coprocessor are always saved in ``extended'' (raw) format, but all C
9520 programs expect to work with ``double'' (virtual) format. In such
9521 cases, @value{GDBN} normally works with the virtual format only (the format
9522 that makes sense for your program), but the @code{info registers} command
9523 prints the data in both formats.
9525 @cindex SSE registers (x86)
9526 @cindex MMX registers (x86)
9527 Some machines have special registers whose contents can be interpreted
9528 in several different ways. For example, modern x86-based machines
9529 have SSE and MMX registers that can hold several values packed
9530 together in several different formats. @value{GDBN} refers to such
9531 registers in @code{struct} notation:
9534 (@value{GDBP}) print $xmm1
9536 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9537 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9538 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9539 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9540 v4_int32 = @{0, 20657912, 11, 13@},
9541 v2_int64 = @{88725056443645952, 55834574859@},
9542 uint128 = 0x0000000d0000000b013b36f800000000
9547 To set values of such registers, you need to tell @value{GDBN} which
9548 view of the register you wish to change, as if you were assigning
9549 value to a @code{struct} member:
9552 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9555 Normally, register values are relative to the selected stack frame
9556 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9557 value that the register would contain if all stack frames farther in
9558 were exited and their saved registers restored. In order to see the
9559 true contents of hardware registers, you must select the innermost
9560 frame (with @samp{frame 0}).
9562 However, @value{GDBN} must deduce where registers are saved, from the machine
9563 code generated by your compiler. If some registers are not saved, or if
9564 @value{GDBN} is unable to locate the saved registers, the selected stack
9565 frame makes no difference.
9567 @node Floating Point Hardware
9568 @section Floating Point Hardware
9569 @cindex floating point
9571 Depending on the configuration, @value{GDBN} may be able to give
9572 you more information about the status of the floating point hardware.
9577 Display hardware-dependent information about the floating
9578 point unit. The exact contents and layout vary depending on the
9579 floating point chip. Currently, @samp{info float} is supported on
9580 the ARM and x86 machines.
9584 @section Vector Unit
9587 Depending on the configuration, @value{GDBN} may be able to give you
9588 more information about the status of the vector unit.
9593 Display information about the vector unit. The exact contents and
9594 layout vary depending on the hardware.
9597 @node OS Information
9598 @section Operating System Auxiliary Information
9599 @cindex OS information
9601 @value{GDBN} provides interfaces to useful OS facilities that can help
9602 you debug your program.
9604 @cindex auxiliary vector
9605 @cindex vector, auxiliary
9606 Some operating systems supply an @dfn{auxiliary vector} to programs at
9607 startup. This is akin to the arguments and environment that you
9608 specify for a program, but contains a system-dependent variety of
9609 binary values that tell system libraries important details about the
9610 hardware, operating system, and process. Each value's purpose is
9611 identified by an integer tag; the meanings are well-known but system-specific.
9612 Depending on the configuration and operating system facilities,
9613 @value{GDBN} may be able to show you this information. For remote
9614 targets, this functionality may further depend on the remote stub's
9615 support of the @samp{qXfer:auxv:read} packet, see
9616 @ref{qXfer auxiliary vector read}.
9621 Display the auxiliary vector of the inferior, which can be either a
9622 live process or a core dump file. @value{GDBN} prints each tag value
9623 numerically, and also shows names and text descriptions for recognized
9624 tags. Some values in the vector are numbers, some bit masks, and some
9625 pointers to strings or other data. @value{GDBN} displays each value in the
9626 most appropriate form for a recognized tag, and in hexadecimal for
9627 an unrecognized tag.
9630 On some targets, @value{GDBN} can access operating system-specific
9631 information and show it to you. The types of information available
9632 will differ depending on the type of operating system running on the
9633 target. The mechanism used to fetch the data is described in
9634 @ref{Operating System Information}. For remote targets, this
9635 functionality depends on the remote stub's support of the
9636 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9640 @item info os @var{infotype}
9642 Display OS information of the requested type.
9644 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9646 @anchor{linux info os infotypes}
9648 @kindex info os processes
9650 Display the list of processes on the target. For each process,
9651 @value{GDBN} prints the process identifier, the name of the user, the
9652 command corresponding to the process, and the list of processor cores
9653 that the process is currently running on. (To understand what these
9654 properties mean, for this and the following info types, please consult
9655 the general @sc{gnu}/Linux documentation.)
9657 @kindex info os procgroups
9659 Display the list of process groups on the target. For each process,
9660 @value{GDBN} prints the identifier of the process group that it belongs
9661 to, the command corresponding to the process group leader, the process
9662 identifier, and the command line of the process. The list is sorted
9663 first by the process group identifier, then by the process identifier,
9664 so that processes belonging to the same process group are grouped together
9665 and the process group leader is listed first.
9667 @kindex info os threads
9669 Display the list of threads running on the target. For each thread,
9670 @value{GDBN} prints the identifier of the process that the thread
9671 belongs to, the command of the process, the thread identifier, and the
9672 processor core that it is currently running on. The main thread of a
9673 process is not listed.
9675 @kindex info os files
9677 Display the list of open file descriptors on the target. For each
9678 file descriptor, @value{GDBN} prints the identifier of the process
9679 owning the descriptor, the command of the owning process, the value
9680 of the descriptor, and the target of the descriptor.
9682 @kindex info os sockets
9684 Display the list of Internet-domain sockets on the target. For each
9685 socket, @value{GDBN} prints the address and port of the local and
9686 remote endpoints, the current state of the connection, the creator of
9687 the socket, the IP address family of the socket, and the type of the
9692 Display the list of all System V shared-memory regions on the target.
9693 For each shared-memory region, @value{GDBN} prints the region key,
9694 the shared-memory identifier, the access permissions, the size of the
9695 region, the process that created the region, the process that last
9696 attached to or detached from the region, the current number of live
9697 attaches to the region, and the times at which the region was last
9698 attached to, detach from, and changed.
9700 @kindex info os semaphores
9702 Display the list of all System V semaphore sets on the target. For each
9703 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9704 set identifier, the access permissions, the number of semaphores in the
9705 set, the user and group of the owner and creator of the semaphore set,
9706 and the times at which the semaphore set was operated upon and changed.
9710 Display the list of all System V message queues on the target. For each
9711 message queue, @value{GDBN} prints the message queue key, the message
9712 queue identifier, the access permissions, the current number of bytes
9713 on the queue, the current number of messages on the queue, the processes
9714 that last sent and received a message on the queue, the user and group
9715 of the owner and creator of the message queue, the times at which a
9716 message was last sent and received on the queue, and the time at which
9717 the message queue was last changed.
9719 @kindex info os modules
9721 Display the list of all loaded kernel modules on the target. For each
9722 module, @value{GDBN} prints the module name, the size of the module in
9723 bytes, the number of times the module is used, the dependencies of the
9724 module, the status of the module, and the address of the loaded module
9729 If @var{infotype} is omitted, then list the possible values for
9730 @var{infotype} and the kind of OS information available for each
9731 @var{infotype}. If the target does not return a list of possible
9732 types, this command will report an error.
9735 @node Memory Region Attributes
9736 @section Memory Region Attributes
9737 @cindex memory region attributes
9739 @dfn{Memory region attributes} allow you to describe special handling
9740 required by regions of your target's memory. @value{GDBN} uses
9741 attributes to determine whether to allow certain types of memory
9742 accesses; whether to use specific width accesses; and whether to cache
9743 target memory. By default the description of memory regions is
9744 fetched from the target (if the current target supports this), but the
9745 user can override the fetched regions.
9747 Defined memory regions can be individually enabled and disabled. When a
9748 memory region is disabled, @value{GDBN} uses the default attributes when
9749 accessing memory in that region. Similarly, if no memory regions have
9750 been defined, @value{GDBN} uses the default attributes when accessing
9753 When a memory region is defined, it is given a number to identify it;
9754 to enable, disable, or remove a memory region, you specify that number.
9758 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9759 Define a memory region bounded by @var{lower} and @var{upper} with
9760 attributes @var{attributes}@dots{}, and add it to the list of regions
9761 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9762 case: it is treated as the target's maximum memory address.
9763 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9766 Discard any user changes to the memory regions and use target-supplied
9767 regions, if available, or no regions if the target does not support.
9770 @item delete mem @var{nums}@dots{}
9771 Remove memory regions @var{nums}@dots{} from the list of regions
9772 monitored by @value{GDBN}.
9775 @item disable mem @var{nums}@dots{}
9776 Disable monitoring of memory regions @var{nums}@dots{}.
9777 A disabled memory region is not forgotten.
9778 It may be enabled again later.
9781 @item enable mem @var{nums}@dots{}
9782 Enable monitoring of memory regions @var{nums}@dots{}.
9786 Print a table of all defined memory regions, with the following columns
9790 @item Memory Region Number
9791 @item Enabled or Disabled.
9792 Enabled memory regions are marked with @samp{y}.
9793 Disabled memory regions are marked with @samp{n}.
9796 The address defining the inclusive lower bound of the memory region.
9799 The address defining the exclusive upper bound of the memory region.
9802 The list of attributes set for this memory region.
9807 @subsection Attributes
9809 @subsubsection Memory Access Mode
9810 The access mode attributes set whether @value{GDBN} may make read or
9811 write accesses to a memory region.
9813 While these attributes prevent @value{GDBN} from performing invalid
9814 memory accesses, they do nothing to prevent the target system, I/O DMA,
9815 etc.@: from accessing memory.
9819 Memory is read only.
9821 Memory is write only.
9823 Memory is read/write. This is the default.
9826 @subsubsection Memory Access Size
9827 The access size attribute tells @value{GDBN} to use specific sized
9828 accesses in the memory region. Often memory mapped device registers
9829 require specific sized accesses. If no access size attribute is
9830 specified, @value{GDBN} may use accesses of any size.
9834 Use 8 bit memory accesses.
9836 Use 16 bit memory accesses.
9838 Use 32 bit memory accesses.
9840 Use 64 bit memory accesses.
9843 @c @subsubsection Hardware/Software Breakpoints
9844 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9845 @c will use hardware or software breakpoints for the internal breakpoints
9846 @c used by the step, next, finish, until, etc. commands.
9850 @c Always use hardware breakpoints
9851 @c @item swbreak (default)
9854 @subsubsection Data Cache
9855 The data cache attributes set whether @value{GDBN} will cache target
9856 memory. While this generally improves performance by reducing debug
9857 protocol overhead, it can lead to incorrect results because @value{GDBN}
9858 does not know about volatile variables or memory mapped device
9863 Enable @value{GDBN} to cache target memory.
9865 Disable @value{GDBN} from caching target memory. This is the default.
9868 @subsection Memory Access Checking
9869 @value{GDBN} can be instructed to refuse accesses to memory that is
9870 not explicitly described. This can be useful if accessing such
9871 regions has undesired effects for a specific target, or to provide
9872 better error checking. The following commands control this behaviour.
9875 @kindex set mem inaccessible-by-default
9876 @item set mem inaccessible-by-default [on|off]
9877 If @code{on} is specified, make @value{GDBN} treat memory not
9878 explicitly described by the memory ranges as non-existent and refuse accesses
9879 to such memory. The checks are only performed if there's at least one
9880 memory range defined. If @code{off} is specified, make @value{GDBN}
9881 treat the memory not explicitly described by the memory ranges as RAM.
9882 The default value is @code{on}.
9883 @kindex show mem inaccessible-by-default
9884 @item show mem inaccessible-by-default
9885 Show the current handling of accesses to unknown memory.
9889 @c @subsubsection Memory Write Verification
9890 @c The memory write verification attributes set whether @value{GDBN}
9891 @c will re-reads data after each write to verify the write was successful.
9895 @c @item noverify (default)
9898 @node Dump/Restore Files
9899 @section Copy Between Memory and a File
9900 @cindex dump/restore files
9901 @cindex append data to a file
9902 @cindex dump data to a file
9903 @cindex restore data from a file
9905 You can use the commands @code{dump}, @code{append}, and
9906 @code{restore} to copy data between target memory and a file. The
9907 @code{dump} and @code{append} commands write data to a file, and the
9908 @code{restore} command reads data from a file back into the inferior's
9909 memory. Files may be in binary, Motorola S-record, Intel hex, or
9910 Tektronix Hex format; however, @value{GDBN} can only append to binary
9916 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9917 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
9918 Dump the contents of memory from @var{start_addr} to @var{end_addr},
9919 or the value of @var{expr}, to @var{filename} in the given format.
9921 The @var{format} parameter may be any one of:
9928 Motorola S-record format.
9930 Tektronix Hex format.
9933 @value{GDBN} uses the same definitions of these formats as the
9934 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
9935 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
9939 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
9940 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
9941 Append the contents of memory from @var{start_addr} to @var{end_addr},
9942 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
9943 (@value{GDBN} can only append data to files in raw binary form.)
9946 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
9947 Restore the contents of file @var{filename} into memory. The
9948 @code{restore} command can automatically recognize any known @sc{bfd}
9949 file format, except for raw binary. To restore a raw binary file you
9950 must specify the optional keyword @code{binary} after the filename.
9952 If @var{bias} is non-zero, its value will be added to the addresses
9953 contained in the file. Binary files always start at address zero, so
9954 they will be restored at address @var{bias}. Other bfd files have
9955 a built-in location; they will be restored at offset @var{bias}
9958 If @var{start} and/or @var{end} are non-zero, then only data between
9959 file offset @var{start} and file offset @var{end} will be restored.
9960 These offsets are relative to the addresses in the file, before
9961 the @var{bias} argument is applied.
9965 @node Core File Generation
9966 @section How to Produce a Core File from Your Program
9967 @cindex dump core from inferior
9969 A @dfn{core file} or @dfn{core dump} is a file that records the memory
9970 image of a running process and its process status (register values
9971 etc.). Its primary use is post-mortem debugging of a program that
9972 crashed while it ran outside a debugger. A program that crashes
9973 automatically produces a core file, unless this feature is disabled by
9974 the user. @xref{Files}, for information on invoking @value{GDBN} in
9975 the post-mortem debugging mode.
9977 Occasionally, you may wish to produce a core file of the program you
9978 are debugging in order to preserve a snapshot of its state.
9979 @value{GDBN} has a special command for that.
9983 @kindex generate-core-file
9984 @item generate-core-file [@var{file}]
9985 @itemx gcore [@var{file}]
9986 Produce a core dump of the inferior process. The optional argument
9987 @var{file} specifies the file name where to put the core dump. If not
9988 specified, the file name defaults to @file{core.@var{pid}}, where
9989 @var{pid} is the inferior process ID.
9991 Note that this command is implemented only for some systems (as of
9992 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
9995 @node Character Sets
9996 @section Character Sets
9997 @cindex character sets
9999 @cindex translating between character sets
10000 @cindex host character set
10001 @cindex target character set
10003 If the program you are debugging uses a different character set to
10004 represent characters and strings than the one @value{GDBN} uses itself,
10005 @value{GDBN} can automatically translate between the character sets for
10006 you. The character set @value{GDBN} uses we call the @dfn{host
10007 character set}; the one the inferior program uses we call the
10008 @dfn{target character set}.
10010 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10011 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10012 remote protocol (@pxref{Remote Debugging}) to debug a program
10013 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10014 then the host character set is Latin-1, and the target character set is
10015 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10016 target-charset EBCDIC-US}, then @value{GDBN} translates between
10017 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10018 character and string literals in expressions.
10020 @value{GDBN} has no way to automatically recognize which character set
10021 the inferior program uses; you must tell it, using the @code{set
10022 target-charset} command, described below.
10024 Here are the commands for controlling @value{GDBN}'s character set
10028 @item set target-charset @var{charset}
10029 @kindex set target-charset
10030 Set the current target character set to @var{charset}. To display the
10031 list of supported target character sets, type
10032 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10034 @item set host-charset @var{charset}
10035 @kindex set host-charset
10036 Set the current host character set to @var{charset}.
10038 By default, @value{GDBN} uses a host character set appropriate to the
10039 system it is running on; you can override that default using the
10040 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10041 automatically determine the appropriate host character set. In this
10042 case, @value{GDBN} uses @samp{UTF-8}.
10044 @value{GDBN} can only use certain character sets as its host character
10045 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10046 @value{GDBN} will list the host character sets it supports.
10048 @item set charset @var{charset}
10049 @kindex set charset
10050 Set the current host and target character sets to @var{charset}. As
10051 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10052 @value{GDBN} will list the names of the character sets that can be used
10053 for both host and target.
10056 @kindex show charset
10057 Show the names of the current host and target character sets.
10059 @item show host-charset
10060 @kindex show host-charset
10061 Show the name of the current host character set.
10063 @item show target-charset
10064 @kindex show target-charset
10065 Show the name of the current target character set.
10067 @item set target-wide-charset @var{charset}
10068 @kindex set target-wide-charset
10069 Set the current target's wide character set to @var{charset}. This is
10070 the character set used by the target's @code{wchar_t} type. To
10071 display the list of supported wide character sets, type
10072 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10074 @item show target-wide-charset
10075 @kindex show target-wide-charset
10076 Show the name of the current target's wide character set.
10079 Here is an example of @value{GDBN}'s character set support in action.
10080 Assume that the following source code has been placed in the file
10081 @file{charset-test.c}:
10087 = @{72, 101, 108, 108, 111, 44, 32, 119,
10088 111, 114, 108, 100, 33, 10, 0@};
10089 char ibm1047_hello[]
10090 = @{200, 133, 147, 147, 150, 107, 64, 166,
10091 150, 153, 147, 132, 90, 37, 0@};
10095 printf ("Hello, world!\n");
10099 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10100 containing the string @samp{Hello, world!} followed by a newline,
10101 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10103 We compile the program, and invoke the debugger on it:
10106 $ gcc -g charset-test.c -o charset-test
10107 $ gdb -nw charset-test
10108 GNU gdb 2001-12-19-cvs
10109 Copyright 2001 Free Software Foundation, Inc.
10114 We can use the @code{show charset} command to see what character sets
10115 @value{GDBN} is currently using to interpret and display characters and
10119 (@value{GDBP}) show charset
10120 The current host and target character set is `ISO-8859-1'.
10124 For the sake of printing this manual, let's use @sc{ascii} as our
10125 initial character set:
10127 (@value{GDBP}) set charset ASCII
10128 (@value{GDBP}) show charset
10129 The current host and target character set is `ASCII'.
10133 Let's assume that @sc{ascii} is indeed the correct character set for our
10134 host system --- in other words, let's assume that if @value{GDBN} prints
10135 characters using the @sc{ascii} character set, our terminal will display
10136 them properly. Since our current target character set is also
10137 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10140 (@value{GDBP}) print ascii_hello
10141 $1 = 0x401698 "Hello, world!\n"
10142 (@value{GDBP}) print ascii_hello[0]
10147 @value{GDBN} uses the target character set for character and string
10148 literals you use in expressions:
10151 (@value{GDBP}) print '+'
10156 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10159 @value{GDBN} relies on the user to tell it which character set the
10160 target program uses. If we print @code{ibm1047_hello} while our target
10161 character set is still @sc{ascii}, we get jibberish:
10164 (@value{GDBP}) print ibm1047_hello
10165 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10166 (@value{GDBP}) print ibm1047_hello[0]
10171 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10172 @value{GDBN} tells us the character sets it supports:
10175 (@value{GDBP}) set target-charset
10176 ASCII EBCDIC-US IBM1047 ISO-8859-1
10177 (@value{GDBP}) set target-charset
10180 We can select @sc{ibm1047} as our target character set, and examine the
10181 program's strings again. Now the @sc{ascii} string is wrong, but
10182 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10183 target character set, @sc{ibm1047}, to the host character set,
10184 @sc{ascii}, and they display correctly:
10187 (@value{GDBP}) set target-charset IBM1047
10188 (@value{GDBP}) show charset
10189 The current host character set is `ASCII'.
10190 The current target character set is `IBM1047'.
10191 (@value{GDBP}) print ascii_hello
10192 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10193 (@value{GDBP}) print ascii_hello[0]
10195 (@value{GDBP}) print ibm1047_hello
10196 $8 = 0x4016a8 "Hello, world!\n"
10197 (@value{GDBP}) print ibm1047_hello[0]
10202 As above, @value{GDBN} uses the target character set for character and
10203 string literals you use in expressions:
10206 (@value{GDBP}) print '+'
10211 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10214 @node Caching Remote Data
10215 @section Caching Data of Remote Targets
10216 @cindex caching data of remote targets
10218 @value{GDBN} caches data exchanged between the debugger and a
10219 remote target (@pxref{Remote Debugging}). Such caching generally improves
10220 performance, because it reduces the overhead of the remote protocol by
10221 bundling memory reads and writes into large chunks. Unfortunately, simply
10222 caching everything would lead to incorrect results, since @value{GDBN}
10223 does not necessarily know anything about volatile values, memory-mapped I/O
10224 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10225 memory can be changed @emph{while} a gdb command is executing.
10226 Therefore, by default, @value{GDBN} only caches data
10227 known to be on the stack@footnote{In non-stop mode, it is moderately
10228 rare for a running thread to modify the stack of a stopped thread
10229 in a way that would interfere with a backtrace, and caching of
10230 stack reads provides a significant speed up of remote backtraces.}.
10231 Other regions of memory can be explicitly marked as
10232 cacheable; see @pxref{Memory Region Attributes}.
10235 @kindex set remotecache
10236 @item set remotecache on
10237 @itemx set remotecache off
10238 This option no longer does anything; it exists for compatibility
10241 @kindex show remotecache
10242 @item show remotecache
10243 Show the current state of the obsolete remotecache flag.
10245 @kindex set stack-cache
10246 @item set stack-cache on
10247 @itemx set stack-cache off
10248 Enable or disable caching of stack accesses. When @code{ON}, use
10249 caching. By default, this option is @code{ON}.
10251 @kindex show stack-cache
10252 @item show stack-cache
10253 Show the current state of data caching for memory accesses.
10255 @kindex info dcache
10256 @item info dcache @r{[}line@r{]}
10257 Print the information about the data cache performance. The
10258 information displayed includes the dcache width and depth, and for
10259 each cache line, its number, address, and how many times it was
10260 referenced. This command is useful for debugging the data cache
10263 If a line number is specified, the contents of that line will be
10266 @item set dcache size @var{size}
10267 @cindex dcache size
10268 @kindex set dcache size
10269 Set maximum number of entries in dcache (dcache depth above).
10271 @item set dcache line-size @var{line-size}
10272 @cindex dcache line-size
10273 @kindex set dcache line-size
10274 Set number of bytes each dcache entry caches (dcache width above).
10275 Must be a power of 2.
10277 @item show dcache size
10278 @kindex show dcache size
10279 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10281 @item show dcache line-size
10282 @kindex show dcache line-size
10283 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10287 @node Searching Memory
10288 @section Search Memory
10289 @cindex searching memory
10291 Memory can be searched for a particular sequence of bytes with the
10292 @code{find} command.
10296 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10297 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10298 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10299 etc. The search begins at address @var{start_addr} and continues for either
10300 @var{len} bytes or through to @var{end_addr} inclusive.
10303 @var{s} and @var{n} are optional parameters.
10304 They may be specified in either order, apart or together.
10307 @item @var{s}, search query size
10308 The size of each search query value.
10314 halfwords (two bytes)
10318 giant words (eight bytes)
10321 All values are interpreted in the current language.
10322 This means, for example, that if the current source language is C/C@t{++}
10323 then searching for the string ``hello'' includes the trailing '\0'.
10325 If the value size is not specified, it is taken from the
10326 value's type in the current language.
10327 This is useful when one wants to specify the search
10328 pattern as a mixture of types.
10329 Note that this means, for example, that in the case of C-like languages
10330 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10331 which is typically four bytes.
10333 @item @var{n}, maximum number of finds
10334 The maximum number of matches to print. The default is to print all finds.
10337 You can use strings as search values. Quote them with double-quotes
10339 The string value is copied into the search pattern byte by byte,
10340 regardless of the endianness of the target and the size specification.
10342 The address of each match found is printed as well as a count of the
10343 number of matches found.
10345 The address of the last value found is stored in convenience variable
10347 A count of the number of matches is stored in @samp{$numfound}.
10349 For example, if stopped at the @code{printf} in this function:
10355 static char hello[] = "hello-hello";
10356 static struct @{ char c; short s; int i; @}
10357 __attribute__ ((packed)) mixed
10358 = @{ 'c', 0x1234, 0x87654321 @};
10359 printf ("%s\n", hello);
10364 you get during debugging:
10367 (gdb) find &hello[0], +sizeof(hello), "hello"
10368 0x804956d <hello.1620+6>
10370 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10371 0x8049567 <hello.1620>
10372 0x804956d <hello.1620+6>
10374 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10375 0x8049567 <hello.1620>
10377 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10378 0x8049560 <mixed.1625>
10380 (gdb) print $numfound
10383 $2 = (void *) 0x8049560
10386 @node Optimized Code
10387 @chapter Debugging Optimized Code
10388 @cindex optimized code, debugging
10389 @cindex debugging optimized code
10391 Almost all compilers support optimization. With optimization
10392 disabled, the compiler generates assembly code that corresponds
10393 directly to your source code, in a simplistic way. As the compiler
10394 applies more powerful optimizations, the generated assembly code
10395 diverges from your original source code. With help from debugging
10396 information generated by the compiler, @value{GDBN} can map from
10397 the running program back to constructs from your original source.
10399 @value{GDBN} is more accurate with optimization disabled. If you
10400 can recompile without optimization, it is easier to follow the
10401 progress of your program during debugging. But, there are many cases
10402 where you may need to debug an optimized version.
10404 When you debug a program compiled with @samp{-g -O}, remember that the
10405 optimizer has rearranged your code; the debugger shows you what is
10406 really there. Do not be too surprised when the execution path does not
10407 exactly match your source file! An extreme example: if you define a
10408 variable, but never use it, @value{GDBN} never sees that
10409 variable---because the compiler optimizes it out of existence.
10411 Some things do not work as well with @samp{-g -O} as with just
10412 @samp{-g}, particularly on machines with instruction scheduling. If in
10413 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10414 please report it to us as a bug (including a test case!).
10415 @xref{Variables}, for more information about debugging optimized code.
10418 * Inline Functions:: How @value{GDBN} presents inlining
10419 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10422 @node Inline Functions
10423 @section Inline Functions
10424 @cindex inline functions, debugging
10426 @dfn{Inlining} is an optimization that inserts a copy of the function
10427 body directly at each call site, instead of jumping to a shared
10428 routine. @value{GDBN} displays inlined functions just like
10429 non-inlined functions. They appear in backtraces. You can view their
10430 arguments and local variables, step into them with @code{step}, skip
10431 them with @code{next}, and escape from them with @code{finish}.
10432 You can check whether a function was inlined by using the
10433 @code{info frame} command.
10435 For @value{GDBN} to support inlined functions, the compiler must
10436 record information about inlining in the debug information ---
10437 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10438 other compilers do also. @value{GDBN} only supports inlined functions
10439 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10440 do not emit two required attributes (@samp{DW_AT_call_file} and
10441 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10442 function calls with earlier versions of @value{NGCC}. It instead
10443 displays the arguments and local variables of inlined functions as
10444 local variables in the caller.
10446 The body of an inlined function is directly included at its call site;
10447 unlike a non-inlined function, there are no instructions devoted to
10448 the call. @value{GDBN} still pretends that the call site and the
10449 start of the inlined function are different instructions. Stepping to
10450 the call site shows the call site, and then stepping again shows
10451 the first line of the inlined function, even though no additional
10452 instructions are executed.
10454 This makes source-level debugging much clearer; you can see both the
10455 context of the call and then the effect of the call. Only stepping by
10456 a single instruction using @code{stepi} or @code{nexti} does not do
10457 this; single instruction steps always show the inlined body.
10459 There are some ways that @value{GDBN} does not pretend that inlined
10460 function calls are the same as normal calls:
10464 Setting breakpoints at the call site of an inlined function may not
10465 work, because the call site does not contain any code. @value{GDBN}
10466 may incorrectly move the breakpoint to the next line of the enclosing
10467 function, after the call. This limitation will be removed in a future
10468 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10469 or inside the inlined function instead.
10472 @value{GDBN} cannot locate the return value of inlined calls after
10473 using the @code{finish} command. This is a limitation of compiler-generated
10474 debugging information; after @code{finish}, you can step to the next line
10475 and print a variable where your program stored the return value.
10479 @node Tail Call Frames
10480 @section Tail Call Frames
10481 @cindex tail call frames, debugging
10483 Function @code{B} can call function @code{C} in its very last statement. In
10484 unoptimized compilation the call of @code{C} is immediately followed by return
10485 instruction at the end of @code{B} code. Optimizing compiler may replace the
10486 call and return in function @code{B} into one jump to function @code{C}
10487 instead. Such use of a jump instruction is called @dfn{tail call}.
10489 During execution of function @code{C}, there will be no indication in the
10490 function call stack frames that it was tail-called from @code{B}. If function
10491 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10492 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10493 some cases @value{GDBN} can determine that @code{C} was tail-called from
10494 @code{B}, and it will then create fictitious call frame for that, with the
10495 return address set up as if @code{B} called @code{C} normally.
10497 This functionality is currently supported only by DWARF 2 debugging format and
10498 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10499 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10502 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10503 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10507 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10509 Stack level 1, frame at 0x7fffffffda30:
10510 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10511 tail call frame, caller of frame at 0x7fffffffda30
10512 source language c++.
10513 Arglist at unknown address.
10514 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10517 The detection of all the possible code path executions can find them ambiguous.
10518 There is no execution history stored (possible @ref{Reverse Execution} is never
10519 used for this purpose) and the last known caller could have reached the known
10520 callee by multiple different jump sequences. In such case @value{GDBN} still
10521 tries to show at least all the unambiguous top tail callers and all the
10522 unambiguous bottom tail calees, if any.
10525 @anchor{set debug entry-values}
10526 @item set debug entry-values
10527 @kindex set debug entry-values
10528 When set to on, enables printing of analysis messages for both frame argument
10529 values at function entry and tail calls. It will show all the possible valid
10530 tail calls code paths it has considered. It will also print the intersection
10531 of them with the final unambiguous (possibly partial or even empty) code path
10534 @item show debug entry-values
10535 @kindex show debug entry-values
10536 Show the current state of analysis messages printing for both frame argument
10537 values at function entry and tail calls.
10540 The analysis messages for tail calls can for example show why the virtual tail
10541 call frame for function @code{c} has not been recognized (due to the indirect
10542 reference by variable @code{x}):
10545 static void __attribute__((noinline, noclone)) c (void);
10546 void (*x) (void) = c;
10547 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10548 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10549 int main (void) @{ x (); return 0; @}
10551 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10552 DW_TAG_GNU_call_site 0x40039a in main
10554 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10557 #1 0x000000000040039a in main () at t.c:5
10560 Another possibility is an ambiguous virtual tail call frames resolution:
10564 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10565 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10566 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10567 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10568 static void __attribute__((noinline, noclone)) b (void)
10569 @{ if (i) c (); else e (); @}
10570 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10571 int main (void) @{ a (); return 0; @}
10573 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10574 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10575 tailcall: reduced: 0x4004d2(a) |
10578 #1 0x00000000004004d2 in a () at t.c:8
10579 #2 0x0000000000400395 in main () at t.c:9
10582 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10583 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10585 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10586 @ifset HAVE_MAKEINFO_CLICK
10587 @set ARROW @click{}
10588 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10589 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10591 @ifclear HAVE_MAKEINFO_CLICK
10593 @set CALLSEQ1B @value{CALLSEQ1A}
10594 @set CALLSEQ2B @value{CALLSEQ2A}
10597 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10598 The code can have possible execution paths @value{CALLSEQ1B} or
10599 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10601 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10602 has found. It then finds another possible calling sequcen - that one is
10603 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10604 printed as the @code{reduced:} calling sequence. That one could have many
10605 futher @code{compare:} and @code{reduced:} statements as long as there remain
10606 any non-ambiguous sequence entries.
10608 For the frame of function @code{b} in both cases there are different possible
10609 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10610 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10611 therefore this one is displayed to the user while the ambiguous frames are
10614 There can be also reasons why printing of frame argument values at function
10619 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10620 static void __attribute__((noinline, noclone)) a (int i);
10621 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10622 static void __attribute__((noinline, noclone)) a (int i)
10623 @{ if (i) b (i - 1); else c (0); @}
10624 int main (void) @{ a (5); return 0; @}
10627 #0 c (i=i@@entry=0) at t.c:2
10628 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10629 function "a" at 0x400420 can call itself via tail calls
10630 i=<optimized out>) at t.c:6
10631 #2 0x000000000040036e in main () at t.c:7
10634 @value{GDBN} cannot find out from the inferior state if and how many times did
10635 function @code{a} call itself (via function @code{b}) as these calls would be
10636 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10637 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10638 prints @code{<optimized out>} instead.
10641 @chapter C Preprocessor Macros
10643 Some languages, such as C and C@t{++}, provide a way to define and invoke
10644 ``preprocessor macros'' which expand into strings of tokens.
10645 @value{GDBN} can evaluate expressions containing macro invocations, show
10646 the result of macro expansion, and show a macro's definition, including
10647 where it was defined.
10649 You may need to compile your program specially to provide @value{GDBN}
10650 with information about preprocessor macros. Most compilers do not
10651 include macros in their debugging information, even when you compile
10652 with the @option{-g} flag. @xref{Compilation}.
10654 A program may define a macro at one point, remove that definition later,
10655 and then provide a different definition after that. Thus, at different
10656 points in the program, a macro may have different definitions, or have
10657 no definition at all. If there is a current stack frame, @value{GDBN}
10658 uses the macros in scope at that frame's source code line. Otherwise,
10659 @value{GDBN} uses the macros in scope at the current listing location;
10662 Whenever @value{GDBN} evaluates an expression, it always expands any
10663 macro invocations present in the expression. @value{GDBN} also provides
10664 the following commands for working with macros explicitly.
10668 @kindex macro expand
10669 @cindex macro expansion, showing the results of preprocessor
10670 @cindex preprocessor macro expansion, showing the results of
10671 @cindex expanding preprocessor macros
10672 @item macro expand @var{expression}
10673 @itemx macro exp @var{expression}
10674 Show the results of expanding all preprocessor macro invocations in
10675 @var{expression}. Since @value{GDBN} simply expands macros, but does
10676 not parse the result, @var{expression} need not be a valid expression;
10677 it can be any string of tokens.
10680 @item macro expand-once @var{expression}
10681 @itemx macro exp1 @var{expression}
10682 @cindex expand macro once
10683 @i{(This command is not yet implemented.)} Show the results of
10684 expanding those preprocessor macro invocations that appear explicitly in
10685 @var{expression}. Macro invocations appearing in that expansion are
10686 left unchanged. This command allows you to see the effect of a
10687 particular macro more clearly, without being confused by further
10688 expansions. Since @value{GDBN} simply expands macros, but does not
10689 parse the result, @var{expression} need not be a valid expression; it
10690 can be any string of tokens.
10693 @cindex macro definition, showing
10694 @cindex definition of a macro, showing
10695 @cindex macros, from debug info
10696 @item info macro [-a|-all] [--] @var{macro}
10697 Show the current definition or all definitions of the named @var{macro},
10698 and describe the source location or compiler command-line where that
10699 definition was established. The optional double dash is to signify the end of
10700 argument processing and the beginning of @var{macro} for non C-like macros where
10701 the macro may begin with a hyphen.
10703 @kindex info macros
10704 @item info macros @var{linespec}
10705 Show all macro definitions that are in effect at the location specified
10706 by @var{linespec}, and describe the source location or compiler
10707 command-line where those definitions were established.
10709 @kindex macro define
10710 @cindex user-defined macros
10711 @cindex defining macros interactively
10712 @cindex macros, user-defined
10713 @item macro define @var{macro} @var{replacement-list}
10714 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10715 Introduce a definition for a preprocessor macro named @var{macro},
10716 invocations of which are replaced by the tokens given in
10717 @var{replacement-list}. The first form of this command defines an
10718 ``object-like'' macro, which takes no arguments; the second form
10719 defines a ``function-like'' macro, which takes the arguments given in
10722 A definition introduced by this command is in scope in every
10723 expression evaluated in @value{GDBN}, until it is removed with the
10724 @code{macro undef} command, described below. The definition overrides
10725 all definitions for @var{macro} present in the program being debugged,
10726 as well as any previous user-supplied definition.
10728 @kindex macro undef
10729 @item macro undef @var{macro}
10730 Remove any user-supplied definition for the macro named @var{macro}.
10731 This command only affects definitions provided with the @code{macro
10732 define} command, described above; it cannot remove definitions present
10733 in the program being debugged.
10737 List all the macros defined using the @code{macro define} command.
10740 @cindex macros, example of debugging with
10741 Here is a transcript showing the above commands in action. First, we
10742 show our source files:
10747 #include "sample.h"
10750 #define ADD(x) (M + x)
10755 printf ("Hello, world!\n");
10757 printf ("We're so creative.\n");
10759 printf ("Goodbye, world!\n");
10766 Now, we compile the program using the @sc{gnu} C compiler,
10767 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10768 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10769 and @option{-gdwarf-4}; we recommend always choosing the most recent
10770 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10771 includes information about preprocessor macros in the debugging
10775 $ gcc -gdwarf-2 -g3 sample.c -o sample
10779 Now, we start @value{GDBN} on our sample program:
10783 GNU gdb 2002-05-06-cvs
10784 Copyright 2002 Free Software Foundation, Inc.
10785 GDB is free software, @dots{}
10789 We can expand macros and examine their definitions, even when the
10790 program is not running. @value{GDBN} uses the current listing position
10791 to decide which macro definitions are in scope:
10794 (@value{GDBP}) list main
10797 5 #define ADD(x) (M + x)
10802 10 printf ("Hello, world!\n");
10804 12 printf ("We're so creative.\n");
10805 (@value{GDBP}) info macro ADD
10806 Defined at /home/jimb/gdb/macros/play/sample.c:5
10807 #define ADD(x) (M + x)
10808 (@value{GDBP}) info macro Q
10809 Defined at /home/jimb/gdb/macros/play/sample.h:1
10810 included at /home/jimb/gdb/macros/play/sample.c:2
10812 (@value{GDBP}) macro expand ADD(1)
10813 expands to: (42 + 1)
10814 (@value{GDBP}) macro expand-once ADD(1)
10815 expands to: once (M + 1)
10819 In the example above, note that @code{macro expand-once} expands only
10820 the macro invocation explicit in the original text --- the invocation of
10821 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10822 which was introduced by @code{ADD}.
10824 Once the program is running, @value{GDBN} uses the macro definitions in
10825 force at the source line of the current stack frame:
10828 (@value{GDBP}) break main
10829 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10831 Starting program: /home/jimb/gdb/macros/play/sample
10833 Breakpoint 1, main () at sample.c:10
10834 10 printf ("Hello, world!\n");
10838 At line 10, the definition of the macro @code{N} at line 9 is in force:
10841 (@value{GDBP}) info macro N
10842 Defined at /home/jimb/gdb/macros/play/sample.c:9
10844 (@value{GDBP}) macro expand N Q M
10845 expands to: 28 < 42
10846 (@value{GDBP}) print N Q M
10851 As we step over directives that remove @code{N}'s definition, and then
10852 give it a new definition, @value{GDBN} finds the definition (or lack
10853 thereof) in force at each point:
10856 (@value{GDBP}) next
10858 12 printf ("We're so creative.\n");
10859 (@value{GDBP}) info macro N
10860 The symbol `N' has no definition as a C/C++ preprocessor macro
10861 at /home/jimb/gdb/macros/play/sample.c:12
10862 (@value{GDBP}) next
10864 14 printf ("Goodbye, world!\n");
10865 (@value{GDBP}) info macro N
10866 Defined at /home/jimb/gdb/macros/play/sample.c:13
10868 (@value{GDBP}) macro expand N Q M
10869 expands to: 1729 < 42
10870 (@value{GDBP}) print N Q M
10875 In addition to source files, macros can be defined on the compilation command
10876 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
10877 such a way, @value{GDBN} displays the location of their definition as line zero
10878 of the source file submitted to the compiler.
10881 (@value{GDBP}) info macro __STDC__
10882 Defined at /home/jimb/gdb/macros/play/sample.c:0
10889 @chapter Tracepoints
10890 @c This chapter is based on the documentation written by Michael
10891 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
10893 @cindex tracepoints
10894 In some applications, it is not feasible for the debugger to interrupt
10895 the program's execution long enough for the developer to learn
10896 anything helpful about its behavior. If the program's correctness
10897 depends on its real-time behavior, delays introduced by a debugger
10898 might cause the program to change its behavior drastically, or perhaps
10899 fail, even when the code itself is correct. It is useful to be able
10900 to observe the program's behavior without interrupting it.
10902 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
10903 specify locations in the program, called @dfn{tracepoints}, and
10904 arbitrary expressions to evaluate when those tracepoints are reached.
10905 Later, using the @code{tfind} command, you can examine the values
10906 those expressions had when the program hit the tracepoints. The
10907 expressions may also denote objects in memory---structures or arrays,
10908 for example---whose values @value{GDBN} should record; while visiting
10909 a particular tracepoint, you may inspect those objects as if they were
10910 in memory at that moment. However, because @value{GDBN} records these
10911 values without interacting with you, it can do so quickly and
10912 unobtrusively, hopefully not disturbing the program's behavior.
10914 The tracepoint facility is currently available only for remote
10915 targets. @xref{Targets}. In addition, your remote target must know
10916 how to collect trace data. This functionality is implemented in the
10917 remote stub; however, none of the stubs distributed with @value{GDBN}
10918 support tracepoints as of this writing. The format of the remote
10919 packets used to implement tracepoints are described in @ref{Tracepoint
10922 It is also possible to get trace data from a file, in a manner reminiscent
10923 of corefiles; you specify the filename, and use @code{tfind} to search
10924 through the file. @xref{Trace Files}, for more details.
10926 This chapter describes the tracepoint commands and features.
10929 * Set Tracepoints::
10930 * Analyze Collected Data::
10931 * Tracepoint Variables::
10935 @node Set Tracepoints
10936 @section Commands to Set Tracepoints
10938 Before running such a @dfn{trace experiment}, an arbitrary number of
10939 tracepoints can be set. A tracepoint is actually a special type of
10940 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
10941 standard breakpoint commands. For instance, as with breakpoints,
10942 tracepoint numbers are successive integers starting from one, and many
10943 of the commands associated with tracepoints take the tracepoint number
10944 as their argument, to identify which tracepoint to work on.
10946 For each tracepoint, you can specify, in advance, some arbitrary set
10947 of data that you want the target to collect in the trace buffer when
10948 it hits that tracepoint. The collected data can include registers,
10949 local variables, or global data. Later, you can use @value{GDBN}
10950 commands to examine the values these data had at the time the
10951 tracepoint was hit.
10953 Tracepoints do not support every breakpoint feature. Ignore counts on
10954 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
10955 commands when they are hit. Tracepoints may not be thread-specific
10958 @cindex fast tracepoints
10959 Some targets may support @dfn{fast tracepoints}, which are inserted in
10960 a different way (such as with a jump instead of a trap), that is
10961 faster but possibly restricted in where they may be installed.
10963 @cindex static tracepoints
10964 @cindex markers, static tracepoints
10965 @cindex probing markers, static tracepoints
10966 Regular and fast tracepoints are dynamic tracing facilities, meaning
10967 that they can be used to insert tracepoints at (almost) any location
10968 in the target. Some targets may also support controlling @dfn{static
10969 tracepoints} from @value{GDBN}. With static tracing, a set of
10970 instrumentation points, also known as @dfn{markers}, are embedded in
10971 the target program, and can be activated or deactivated by name or
10972 address. These are usually placed at locations which facilitate
10973 investigating what the target is actually doing. @value{GDBN}'s
10974 support for static tracing includes being able to list instrumentation
10975 points, and attach them with @value{GDBN} defined high level
10976 tracepoints that expose the whole range of convenience of
10977 @value{GDBN}'s tracepoints support. Namely, support for collecting
10978 registers values and values of global or local (to the instrumentation
10979 point) variables; tracepoint conditions and trace state variables.
10980 The act of installing a @value{GDBN} static tracepoint on an
10981 instrumentation point, or marker, is referred to as @dfn{probing} a
10982 static tracepoint marker.
10984 @code{gdbserver} supports tracepoints on some target systems.
10985 @xref{Server,,Tracepoints support in @code{gdbserver}}.
10987 This section describes commands to set tracepoints and associated
10988 conditions and actions.
10991 * Create and Delete Tracepoints::
10992 * Enable and Disable Tracepoints::
10993 * Tracepoint Passcounts::
10994 * Tracepoint Conditions::
10995 * Trace State Variables::
10996 * Tracepoint Actions::
10997 * Listing Tracepoints::
10998 * Listing Static Tracepoint Markers::
10999 * Starting and Stopping Trace Experiments::
11000 * Tracepoint Restrictions::
11003 @node Create and Delete Tracepoints
11004 @subsection Create and Delete Tracepoints
11007 @cindex set tracepoint
11009 @item trace @var{location}
11010 The @code{trace} command is very similar to the @code{break} command.
11011 Its argument @var{location} can be a source line, a function name, or
11012 an address in the target program. @xref{Specify Location}. The
11013 @code{trace} command defines a tracepoint, which is a point in the
11014 target program where the debugger will briefly stop, collect some
11015 data, and then allow the program to continue. Setting a tracepoint or
11016 changing its actions takes effect immediately if the remote stub
11017 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11019 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11020 these changes don't take effect until the next @code{tstart}
11021 command, and once a trace experiment is running, further changes will
11022 not have any effect until the next trace experiment starts. In addition,
11023 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11024 address is not yet resolved. (This is similar to pending breakpoints.)
11025 Pending tracepoints are not downloaded to the target and not installed
11026 until they are resolved. The resolution of pending tracepoints requires
11027 @value{GDBN} support---when debugging with the remote target, and
11028 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11029 tracing}), pending tracepoints can not be resolved (and downloaded to
11030 the remote stub) while @value{GDBN} is disconnected.
11032 Here are some examples of using the @code{trace} command:
11035 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11037 (@value{GDBP}) @b{trace +2} // 2 lines forward
11039 (@value{GDBP}) @b{trace my_function} // first source line of function
11041 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11043 (@value{GDBP}) @b{trace *0x2117c4} // an address
11047 You can abbreviate @code{trace} as @code{tr}.
11049 @item trace @var{location} if @var{cond}
11050 Set a tracepoint with condition @var{cond}; evaluate the expression
11051 @var{cond} each time the tracepoint is reached, and collect data only
11052 if the value is nonzero---that is, if @var{cond} evaluates as true.
11053 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11054 information on tracepoint conditions.
11056 @item ftrace @var{location} [ if @var{cond} ]
11057 @cindex set fast tracepoint
11058 @cindex fast tracepoints, setting
11060 The @code{ftrace} command sets a fast tracepoint. For targets that
11061 support them, fast tracepoints will use a more efficient but possibly
11062 less general technique to trigger data collection, such as a jump
11063 instruction instead of a trap, or some sort of hardware support. It
11064 may not be possible to create a fast tracepoint at the desired
11065 location, in which case the command will exit with an explanatory
11068 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11071 On 32-bit x86-architecture systems, fast tracepoints normally need to
11072 be placed at an instruction that is 5 bytes or longer, but can be
11073 placed at 4-byte instructions if the low 64K of memory of the target
11074 program is available to install trampolines. Some Unix-type systems,
11075 such as @sc{gnu}/Linux, exclude low addresses from the program's
11076 address space; but for instance with the Linux kernel it is possible
11077 to let @value{GDBN} use this area by doing a @command{sysctl} command
11078 to set the @code{mmap_min_addr} kernel parameter, as in
11081 sudo sysctl -w vm.mmap_min_addr=32768
11085 which sets the low address to 32K, which leaves plenty of room for
11086 trampolines. The minimum address should be set to a page boundary.
11088 @item strace @var{location} [ if @var{cond} ]
11089 @cindex set static tracepoint
11090 @cindex static tracepoints, setting
11091 @cindex probe static tracepoint marker
11093 The @code{strace} command sets a static tracepoint. For targets that
11094 support it, setting a static tracepoint probes a static
11095 instrumentation point, or marker, found at @var{location}. It may not
11096 be possible to set a static tracepoint at the desired location, in
11097 which case the command will exit with an explanatory message.
11099 @value{GDBN} handles arguments to @code{strace} exactly as for
11100 @code{trace}, with the addition that the user can also specify
11101 @code{-m @var{marker}} as @var{location}. This probes the marker
11102 identified by the @var{marker} string identifier. This identifier
11103 depends on the static tracepoint backend library your program is
11104 using. You can find all the marker identifiers in the @samp{ID} field
11105 of the @code{info static-tracepoint-markers} command output.
11106 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11107 Markers}. For example, in the following small program using the UST
11113 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11118 the marker id is composed of joining the first two arguments to the
11119 @code{trace_mark} call with a slash, which translates to:
11122 (@value{GDBP}) info static-tracepoint-markers
11123 Cnt Enb ID Address What
11124 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11130 so you may probe the marker above with:
11133 (@value{GDBP}) strace -m ust/bar33
11136 Static tracepoints accept an extra collect action --- @code{collect
11137 $_sdata}. This collects arbitrary user data passed in the probe point
11138 call to the tracing library. In the UST example above, you'll see
11139 that the third argument to @code{trace_mark} is a printf-like format
11140 string. The user data is then the result of running that formating
11141 string against the following arguments. Note that @code{info
11142 static-tracepoint-markers} command output lists that format string in
11143 the @samp{Data:} field.
11145 You can inspect this data when analyzing the trace buffer, by printing
11146 the $_sdata variable like any other variable available to
11147 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11150 @cindex last tracepoint number
11151 @cindex recent tracepoint number
11152 @cindex tracepoint number
11153 The convenience variable @code{$tpnum} records the tracepoint number
11154 of the most recently set tracepoint.
11156 @kindex delete tracepoint
11157 @cindex tracepoint deletion
11158 @item delete tracepoint @r{[}@var{num}@r{]}
11159 Permanently delete one or more tracepoints. With no argument, the
11160 default is to delete all tracepoints. Note that the regular
11161 @code{delete} command can remove tracepoints also.
11166 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11168 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11172 You can abbreviate this command as @code{del tr}.
11175 @node Enable and Disable Tracepoints
11176 @subsection Enable and Disable Tracepoints
11178 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11181 @kindex disable tracepoint
11182 @item disable tracepoint @r{[}@var{num}@r{]}
11183 Disable tracepoint @var{num}, or all tracepoints if no argument
11184 @var{num} is given. A disabled tracepoint will have no effect during
11185 a trace experiment, but it is not forgotten. You can re-enable
11186 a disabled tracepoint using the @code{enable tracepoint} command.
11187 If the command is issued during a trace experiment and the debug target
11188 has support for disabling tracepoints during a trace experiment, then the
11189 change will be effective immediately. Otherwise, it will be applied to the
11190 next trace experiment.
11192 @kindex enable tracepoint
11193 @item enable tracepoint @r{[}@var{num}@r{]}
11194 Enable tracepoint @var{num}, or all tracepoints. If this command is
11195 issued during a trace experiment and the debug target supports enabling
11196 tracepoints during a trace experiment, then the enabled tracepoints will
11197 become effective immediately. Otherwise, they will become effective the
11198 next time a trace experiment is run.
11201 @node Tracepoint Passcounts
11202 @subsection Tracepoint Passcounts
11206 @cindex tracepoint pass count
11207 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11208 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11209 automatically stop a trace experiment. If a tracepoint's passcount is
11210 @var{n}, then the trace experiment will be automatically stopped on
11211 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11212 @var{num} is not specified, the @code{passcount} command sets the
11213 passcount of the most recently defined tracepoint. If no passcount is
11214 given, the trace experiment will run until stopped explicitly by the
11220 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11221 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11223 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11224 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11225 (@value{GDBP}) @b{trace foo}
11226 (@value{GDBP}) @b{pass 3}
11227 (@value{GDBP}) @b{trace bar}
11228 (@value{GDBP}) @b{pass 2}
11229 (@value{GDBP}) @b{trace baz}
11230 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11231 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11232 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11233 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11237 @node Tracepoint Conditions
11238 @subsection Tracepoint Conditions
11239 @cindex conditional tracepoints
11240 @cindex tracepoint conditions
11242 The simplest sort of tracepoint collects data every time your program
11243 reaches a specified place. You can also specify a @dfn{condition} for
11244 a tracepoint. A condition is just a Boolean expression in your
11245 programming language (@pxref{Expressions, ,Expressions}). A
11246 tracepoint with a condition evaluates the expression each time your
11247 program reaches it, and data collection happens only if the condition
11250 Tracepoint conditions can be specified when a tracepoint is set, by
11251 using @samp{if} in the arguments to the @code{trace} command.
11252 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11253 also be set or changed at any time with the @code{condition} command,
11254 just as with breakpoints.
11256 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11257 the conditional expression itself. Instead, @value{GDBN} encodes the
11258 expression into an agent expression (@pxref{Agent Expressions})
11259 suitable for execution on the target, independently of @value{GDBN}.
11260 Global variables become raw memory locations, locals become stack
11261 accesses, and so forth.
11263 For instance, suppose you have a function that is usually called
11264 frequently, but should not be called after an error has occurred. You
11265 could use the following tracepoint command to collect data about calls
11266 of that function that happen while the error code is propagating
11267 through the program; an unconditional tracepoint could end up
11268 collecting thousands of useless trace frames that you would have to
11272 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11275 @node Trace State Variables
11276 @subsection Trace State Variables
11277 @cindex trace state variables
11279 A @dfn{trace state variable} is a special type of variable that is
11280 created and managed by target-side code. The syntax is the same as
11281 that for GDB's convenience variables (a string prefixed with ``$''),
11282 but they are stored on the target. They must be created explicitly,
11283 using a @code{tvariable} command. They are always 64-bit signed
11286 Trace state variables are remembered by @value{GDBN}, and downloaded
11287 to the target along with tracepoint information when the trace
11288 experiment starts. There are no intrinsic limits on the number of
11289 trace state variables, beyond memory limitations of the target.
11291 @cindex convenience variables, and trace state variables
11292 Although trace state variables are managed by the target, you can use
11293 them in print commands and expressions as if they were convenience
11294 variables; @value{GDBN} will get the current value from the target
11295 while the trace experiment is running. Trace state variables share
11296 the same namespace as other ``$'' variables, which means that you
11297 cannot have trace state variables with names like @code{$23} or
11298 @code{$pc}, nor can you have a trace state variable and a convenience
11299 variable with the same name.
11303 @item tvariable $@var{name} [ = @var{expression} ]
11305 The @code{tvariable} command creates a new trace state variable named
11306 @code{$@var{name}}, and optionally gives it an initial value of
11307 @var{expression}. @var{expression} is evaluated when this command is
11308 entered; the result will be converted to an integer if possible,
11309 otherwise @value{GDBN} will report an error. A subsequent
11310 @code{tvariable} command specifying the same name does not create a
11311 variable, but instead assigns the supplied initial value to the
11312 existing variable of that name, overwriting any previous initial
11313 value. The default initial value is 0.
11315 @item info tvariables
11316 @kindex info tvariables
11317 List all the trace state variables along with their initial values.
11318 Their current values may also be displayed, if the trace experiment is
11321 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11322 @kindex delete tvariable
11323 Delete the given trace state variables, or all of them if no arguments
11328 @node Tracepoint Actions
11329 @subsection Tracepoint Action Lists
11333 @cindex tracepoint actions
11334 @item actions @r{[}@var{num}@r{]}
11335 This command will prompt for a list of actions to be taken when the
11336 tracepoint is hit. If the tracepoint number @var{num} is not
11337 specified, this command sets the actions for the one that was most
11338 recently defined (so that you can define a tracepoint and then say
11339 @code{actions} without bothering about its number). You specify the
11340 actions themselves on the following lines, one action at a time, and
11341 terminate the actions list with a line containing just @code{end}. So
11342 far, the only defined actions are @code{collect}, @code{teval}, and
11343 @code{while-stepping}.
11345 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11346 Commands, ,Breakpoint Command Lists}), except that only the defined
11347 actions are allowed; any other @value{GDBN} command is rejected.
11349 @cindex remove actions from a tracepoint
11350 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11351 and follow it immediately with @samp{end}.
11354 (@value{GDBP}) @b{collect @var{data}} // collect some data
11356 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11358 (@value{GDBP}) @b{end} // signals the end of actions.
11361 In the following example, the action list begins with @code{collect}
11362 commands indicating the things to be collected when the tracepoint is
11363 hit. Then, in order to single-step and collect additional data
11364 following the tracepoint, a @code{while-stepping} command is used,
11365 followed by the list of things to be collected after each step in a
11366 sequence of single steps. The @code{while-stepping} command is
11367 terminated by its own separate @code{end} command. Lastly, the action
11368 list is terminated by an @code{end} command.
11371 (@value{GDBP}) @b{trace foo}
11372 (@value{GDBP}) @b{actions}
11373 Enter actions for tracepoint 1, one per line:
11376 > while-stepping 12
11377 > collect $pc, arr[i]
11382 @kindex collect @r{(tracepoints)}
11383 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11384 Collect values of the given expressions when the tracepoint is hit.
11385 This command accepts a comma-separated list of any valid expressions.
11386 In addition to global, static, or local variables, the following
11387 special arguments are supported:
11391 Collect all registers.
11394 Collect all function arguments.
11397 Collect all local variables.
11400 Collect the return address. This is helpful if you want to see more
11404 Collects the number of arguments from the static probe at which the
11405 tracepoint is located.
11406 @xref{Static Probe Points}.
11408 @item $_probe_arg@var{n}
11409 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11410 from the static probe at which the tracepoint is located.
11411 @xref{Static Probe Points}.
11414 @vindex $_sdata@r{, collect}
11415 Collect static tracepoint marker specific data. Only available for
11416 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11417 Lists}. On the UST static tracepoints library backend, an
11418 instrumentation point resembles a @code{printf} function call. The
11419 tracing library is able to collect user specified data formatted to a
11420 character string using the format provided by the programmer that
11421 instrumented the program. Other backends have similar mechanisms.
11422 Here's an example of a UST marker call:
11425 const char master_name[] = "$your_name";
11426 trace_mark(channel1, marker1, "hello %s", master_name)
11429 In this case, collecting @code{$_sdata} collects the string
11430 @samp{hello $yourname}. When analyzing the trace buffer, you can
11431 inspect @samp{$_sdata} like any other variable available to
11435 You can give several consecutive @code{collect} commands, each one
11436 with a single argument, or one @code{collect} command with several
11437 arguments separated by commas; the effect is the same.
11439 The optional @var{mods} changes the usual handling of the arguments.
11440 @code{s} requests that pointers to chars be handled as strings, in
11441 particular collecting the contents of the memory being pointed at, up
11442 to the first zero. The upper bound is by default the value of the
11443 @code{print elements} variable; if @code{s} is followed by a decimal
11444 number, that is the upper bound instead. So for instance
11445 @samp{collect/s25 mystr} collects as many as 25 characters at
11448 The command @code{info scope} (@pxref{Symbols, info scope}) is
11449 particularly useful for figuring out what data to collect.
11451 @kindex teval @r{(tracepoints)}
11452 @item teval @var{expr1}, @var{expr2}, @dots{}
11453 Evaluate the given expressions when the tracepoint is hit. This
11454 command accepts a comma-separated list of expressions. The results
11455 are discarded, so this is mainly useful for assigning values to trace
11456 state variables (@pxref{Trace State Variables}) without adding those
11457 values to the trace buffer, as would be the case if the @code{collect}
11460 @kindex while-stepping @r{(tracepoints)}
11461 @item while-stepping @var{n}
11462 Perform @var{n} single-step instruction traces after the tracepoint,
11463 collecting new data after each step. The @code{while-stepping}
11464 command is followed by the list of what to collect while stepping
11465 (followed by its own @code{end} command):
11468 > while-stepping 12
11469 > collect $regs, myglobal
11475 Note that @code{$pc} is not automatically collected by
11476 @code{while-stepping}; you need to explicitly collect that register if
11477 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11480 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11481 @kindex set default-collect
11482 @cindex default collection action
11483 This variable is a list of expressions to collect at each tracepoint
11484 hit. It is effectively an additional @code{collect} action prepended
11485 to every tracepoint action list. The expressions are parsed
11486 individually for each tracepoint, so for instance a variable named
11487 @code{xyz} may be interpreted as a global for one tracepoint, and a
11488 local for another, as appropriate to the tracepoint's location.
11490 @item show default-collect
11491 @kindex show default-collect
11492 Show the list of expressions that are collected by default at each
11497 @node Listing Tracepoints
11498 @subsection Listing Tracepoints
11501 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11502 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11503 @cindex information about tracepoints
11504 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11505 Display information about the tracepoint @var{num}. If you don't
11506 specify a tracepoint number, displays information about all the
11507 tracepoints defined so far. The format is similar to that used for
11508 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11509 command, simply restricting itself to tracepoints.
11511 A tracepoint's listing may include additional information specific to
11516 its passcount as given by the @code{passcount @var{n}} command
11519 the state about installed on target of each location
11523 (@value{GDBP}) @b{info trace}
11524 Num Type Disp Enb Address What
11525 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11527 collect globfoo, $regs
11532 2 tracepoint keep y <MULTIPLE>
11534 2.1 y 0x0804859c in func4 at change-loc.h:35
11535 installed on target
11536 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11537 installed on target
11538 2.3 y <PENDING> set_tracepoint
11539 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11540 not installed on target
11545 This command can be abbreviated @code{info tp}.
11548 @node Listing Static Tracepoint Markers
11549 @subsection Listing Static Tracepoint Markers
11552 @kindex info static-tracepoint-markers
11553 @cindex information about static tracepoint markers
11554 @item info static-tracepoint-markers
11555 Display information about all static tracepoint markers defined in the
11558 For each marker, the following columns are printed:
11562 An incrementing counter, output to help readability. This is not a
11565 The marker ID, as reported by the target.
11566 @item Enabled or Disabled
11567 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11568 that are not enabled.
11570 Where the marker is in your program, as a memory address.
11572 Where the marker is in the source for your program, as a file and line
11573 number. If the debug information included in the program does not
11574 allow @value{GDBN} to locate the source of the marker, this column
11575 will be left blank.
11579 In addition, the following information may be printed for each marker:
11583 User data passed to the tracing library by the marker call. In the
11584 UST backend, this is the format string passed as argument to the
11586 @item Static tracepoints probing the marker
11587 The list of static tracepoints attached to the marker.
11591 (@value{GDBP}) info static-tracepoint-markers
11592 Cnt ID Enb Address What
11593 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11594 Data: number1 %d number2 %d
11595 Probed by static tracepoints: #2
11596 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11602 @node Starting and Stopping Trace Experiments
11603 @subsection Starting and Stopping Trace Experiments
11606 @kindex tstart [ @var{notes} ]
11607 @cindex start a new trace experiment
11608 @cindex collected data discarded
11610 This command starts the trace experiment, and begins collecting data.
11611 It has the side effect of discarding all the data collected in the
11612 trace buffer during the previous trace experiment. If any arguments
11613 are supplied, they are taken as a note and stored with the trace
11614 experiment's state. The notes may be arbitrary text, and are
11615 especially useful with disconnected tracing in a multi-user context;
11616 the notes can explain what the trace is doing, supply user contact
11617 information, and so forth.
11619 @kindex tstop [ @var{notes} ]
11620 @cindex stop a running trace experiment
11622 This command stops the trace experiment. If any arguments are
11623 supplied, they are recorded with the experiment as a note. This is
11624 useful if you are stopping a trace started by someone else, for
11625 instance if the trace is interfering with the system's behavior and
11626 needs to be stopped quickly.
11628 @strong{Note}: a trace experiment and data collection may stop
11629 automatically if any tracepoint's passcount is reached
11630 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11633 @cindex status of trace data collection
11634 @cindex trace experiment, status of
11636 This command displays the status of the current trace data
11640 Here is an example of the commands we described so far:
11643 (@value{GDBP}) @b{trace gdb_c_test}
11644 (@value{GDBP}) @b{actions}
11645 Enter actions for tracepoint #1, one per line.
11646 > collect $regs,$locals,$args
11647 > while-stepping 11
11651 (@value{GDBP}) @b{tstart}
11652 [time passes @dots{}]
11653 (@value{GDBP}) @b{tstop}
11656 @anchor{disconnected tracing}
11657 @cindex disconnected tracing
11658 You can choose to continue running the trace experiment even if
11659 @value{GDBN} disconnects from the target, voluntarily or
11660 involuntarily. For commands such as @code{detach}, the debugger will
11661 ask what you want to do with the trace. But for unexpected
11662 terminations (@value{GDBN} crash, network outage), it would be
11663 unfortunate to lose hard-won trace data, so the variable
11664 @code{disconnected-tracing} lets you decide whether the trace should
11665 continue running without @value{GDBN}.
11668 @item set disconnected-tracing on
11669 @itemx set disconnected-tracing off
11670 @kindex set disconnected-tracing
11671 Choose whether a tracing run should continue to run if @value{GDBN}
11672 has disconnected from the target. Note that @code{detach} or
11673 @code{quit} will ask you directly what to do about a running trace no
11674 matter what this variable's setting, so the variable is mainly useful
11675 for handling unexpected situations, such as loss of the network.
11677 @item show disconnected-tracing
11678 @kindex show disconnected-tracing
11679 Show the current choice for disconnected tracing.
11683 When you reconnect to the target, the trace experiment may or may not
11684 still be running; it might have filled the trace buffer in the
11685 meantime, or stopped for one of the other reasons. If it is running,
11686 it will continue after reconnection.
11688 Upon reconnection, the target will upload information about the
11689 tracepoints in effect. @value{GDBN} will then compare that
11690 information to the set of tracepoints currently defined, and attempt
11691 to match them up, allowing for the possibility that the numbers may
11692 have changed due to creation and deletion in the meantime. If one of
11693 the target's tracepoints does not match any in @value{GDBN}, the
11694 debugger will create a new tracepoint, so that you have a number with
11695 which to specify that tracepoint. This matching-up process is
11696 necessarily heuristic, and it may result in useless tracepoints being
11697 created; you may simply delete them if they are of no use.
11699 @cindex circular trace buffer
11700 If your target agent supports a @dfn{circular trace buffer}, then you
11701 can run a trace experiment indefinitely without filling the trace
11702 buffer; when space runs out, the agent deletes already-collected trace
11703 frames, oldest first, until there is enough room to continue
11704 collecting. This is especially useful if your tracepoints are being
11705 hit too often, and your trace gets terminated prematurely because the
11706 buffer is full. To ask for a circular trace buffer, simply set
11707 @samp{circular-trace-buffer} to on. You can set this at any time,
11708 including during tracing; if the agent can do it, it will change
11709 buffer handling on the fly, otherwise it will not take effect until
11713 @item set circular-trace-buffer on
11714 @itemx set circular-trace-buffer off
11715 @kindex set circular-trace-buffer
11716 Choose whether a tracing run should use a linear or circular buffer
11717 for trace data. A linear buffer will not lose any trace data, but may
11718 fill up prematurely, while a circular buffer will discard old trace
11719 data, but it will have always room for the latest tracepoint hits.
11721 @item show circular-trace-buffer
11722 @kindex show circular-trace-buffer
11723 Show the current choice for the trace buffer. Note that this may not
11724 match the agent's current buffer handling, nor is it guaranteed to
11725 match the setting that might have been in effect during a past run,
11726 for instance if you are looking at frames from a trace file.
11731 @item set trace-user @var{text}
11732 @kindex set trace-user
11734 @item show trace-user
11735 @kindex show trace-user
11737 @item set trace-notes @var{text}
11738 @kindex set trace-notes
11739 Set the trace run's notes.
11741 @item show trace-notes
11742 @kindex show trace-notes
11743 Show the trace run's notes.
11745 @item set trace-stop-notes @var{text}
11746 @kindex set trace-stop-notes
11747 Set the trace run's stop notes. The handling of the note is as for
11748 @code{tstop} arguments; the set command is convenient way to fix a
11749 stop note that is mistaken or incomplete.
11751 @item show trace-stop-notes
11752 @kindex show trace-stop-notes
11753 Show the trace run's stop notes.
11757 @node Tracepoint Restrictions
11758 @subsection Tracepoint Restrictions
11760 @cindex tracepoint restrictions
11761 There are a number of restrictions on the use of tracepoints. As
11762 described above, tracepoint data gathering occurs on the target
11763 without interaction from @value{GDBN}. Thus the full capabilities of
11764 the debugger are not available during data gathering, and then at data
11765 examination time, you will be limited by only having what was
11766 collected. The following items describe some common problems, but it
11767 is not exhaustive, and you may run into additional difficulties not
11773 Tracepoint expressions are intended to gather objects (lvalues). Thus
11774 the full flexibility of GDB's expression evaluator is not available.
11775 You cannot call functions, cast objects to aggregate types, access
11776 convenience variables or modify values (except by assignment to trace
11777 state variables). Some language features may implicitly call
11778 functions (for instance Objective-C fields with accessors), and therefore
11779 cannot be collected either.
11782 Collection of local variables, either individually or in bulk with
11783 @code{$locals} or @code{$args}, during @code{while-stepping} may
11784 behave erratically. The stepping action may enter a new scope (for
11785 instance by stepping into a function), or the location of the variable
11786 may change (for instance it is loaded into a register). The
11787 tracepoint data recorded uses the location information for the
11788 variables that is correct for the tracepoint location. When the
11789 tracepoint is created, it is not possible, in general, to determine
11790 where the steps of a @code{while-stepping} sequence will advance the
11791 program---particularly if a conditional branch is stepped.
11794 Collection of an incompletely-initialized or partially-destroyed object
11795 may result in something that @value{GDBN} cannot display, or displays
11796 in a misleading way.
11799 When @value{GDBN} displays a pointer to character it automatically
11800 dereferences the pointer to also display characters of the string
11801 being pointed to. However, collecting the pointer during tracing does
11802 not automatically collect the string. You need to explicitly
11803 dereference the pointer and provide size information if you want to
11804 collect not only the pointer, but the memory pointed to. For example,
11805 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11809 It is not possible to collect a complete stack backtrace at a
11810 tracepoint. Instead, you may collect the registers and a few hundred
11811 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11812 (adjust to use the name of the actual stack pointer register on your
11813 target architecture, and the amount of stack you wish to capture).
11814 Then the @code{backtrace} command will show a partial backtrace when
11815 using a trace frame. The number of stack frames that can be examined
11816 depends on the sizes of the frames in the collected stack. Note that
11817 if you ask for a block so large that it goes past the bottom of the
11818 stack, the target agent may report an error trying to read from an
11822 If you do not collect registers at a tracepoint, @value{GDBN} can
11823 infer that the value of @code{$pc} must be the same as the address of
11824 the tracepoint and use that when you are looking at a trace frame
11825 for that tracepoint. However, this cannot work if the tracepoint has
11826 multiple locations (for instance if it was set in a function that was
11827 inlined), or if it has a @code{while-stepping} loop. In those cases
11828 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11833 @node Analyze Collected Data
11834 @section Using the Collected Data
11836 After the tracepoint experiment ends, you use @value{GDBN} commands
11837 for examining the trace data. The basic idea is that each tracepoint
11838 collects a trace @dfn{snapshot} every time it is hit and another
11839 snapshot every time it single-steps. All these snapshots are
11840 consecutively numbered from zero and go into a buffer, and you can
11841 examine them later. The way you examine them is to @dfn{focus} on a
11842 specific trace snapshot. When the remote stub is focused on a trace
11843 snapshot, it will respond to all @value{GDBN} requests for memory and
11844 registers by reading from the buffer which belongs to that snapshot,
11845 rather than from @emph{real} memory or registers of the program being
11846 debugged. This means that @strong{all} @value{GDBN} commands
11847 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
11848 behave as if we were currently debugging the program state as it was
11849 when the tracepoint occurred. Any requests for data that are not in
11850 the buffer will fail.
11853 * tfind:: How to select a trace snapshot
11854 * tdump:: How to display all data for a snapshot
11855 * save tracepoints:: How to save tracepoints for a future run
11859 @subsection @code{tfind @var{n}}
11862 @cindex select trace snapshot
11863 @cindex find trace snapshot
11864 The basic command for selecting a trace snapshot from the buffer is
11865 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
11866 counting from zero. If no argument @var{n} is given, the next
11867 snapshot is selected.
11869 Here are the various forms of using the @code{tfind} command.
11873 Find the first snapshot in the buffer. This is a synonym for
11874 @code{tfind 0} (since 0 is the number of the first snapshot).
11877 Stop debugging trace snapshots, resume @emph{live} debugging.
11880 Same as @samp{tfind none}.
11883 No argument means find the next trace snapshot.
11886 Find the previous trace snapshot before the current one. This permits
11887 retracing earlier steps.
11889 @item tfind tracepoint @var{num}
11890 Find the next snapshot associated with tracepoint @var{num}. Search
11891 proceeds forward from the last examined trace snapshot. If no
11892 argument @var{num} is given, it means find the next snapshot collected
11893 for the same tracepoint as the current snapshot.
11895 @item tfind pc @var{addr}
11896 Find the next snapshot associated with the value @var{addr} of the
11897 program counter. Search proceeds forward from the last examined trace
11898 snapshot. If no argument @var{addr} is given, it means find the next
11899 snapshot with the same value of PC as the current snapshot.
11901 @item tfind outside @var{addr1}, @var{addr2}
11902 Find the next snapshot whose PC is outside the given range of
11903 addresses (exclusive).
11905 @item tfind range @var{addr1}, @var{addr2}
11906 Find the next snapshot whose PC is between @var{addr1} and
11907 @var{addr2} (inclusive).
11909 @item tfind line @r{[}@var{file}:@r{]}@var{n}
11910 Find the next snapshot associated with the source line @var{n}. If
11911 the optional argument @var{file} is given, refer to line @var{n} in
11912 that source file. Search proceeds forward from the last examined
11913 trace snapshot. If no argument @var{n} is given, it means find the
11914 next line other than the one currently being examined; thus saying
11915 @code{tfind line} repeatedly can appear to have the same effect as
11916 stepping from line to line in a @emph{live} debugging session.
11919 The default arguments for the @code{tfind} commands are specifically
11920 designed to make it easy to scan through the trace buffer. For
11921 instance, @code{tfind} with no argument selects the next trace
11922 snapshot, and @code{tfind -} with no argument selects the previous
11923 trace snapshot. So, by giving one @code{tfind} command, and then
11924 simply hitting @key{RET} repeatedly you can examine all the trace
11925 snapshots in order. Or, by saying @code{tfind -} and then hitting
11926 @key{RET} repeatedly you can examine the snapshots in reverse order.
11927 The @code{tfind line} command with no argument selects the snapshot
11928 for the next source line executed. The @code{tfind pc} command with
11929 no argument selects the next snapshot with the same program counter
11930 (PC) as the current frame. The @code{tfind tracepoint} command with
11931 no argument selects the next trace snapshot collected by the same
11932 tracepoint as the current one.
11934 In addition to letting you scan through the trace buffer manually,
11935 these commands make it easy to construct @value{GDBN} scripts that
11936 scan through the trace buffer and print out whatever collected data
11937 you are interested in. Thus, if we want to examine the PC, FP, and SP
11938 registers from each trace frame in the buffer, we can say this:
11941 (@value{GDBP}) @b{tfind start}
11942 (@value{GDBP}) @b{while ($trace_frame != -1)}
11943 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
11944 $trace_frame, $pc, $sp, $fp
11948 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
11949 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
11950 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
11951 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
11952 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
11953 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
11954 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
11955 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
11956 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
11957 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
11958 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
11961 Or, if we want to examine the variable @code{X} at each source line in
11965 (@value{GDBP}) @b{tfind start}
11966 (@value{GDBP}) @b{while ($trace_frame != -1)}
11967 > printf "Frame %d, X == %d\n", $trace_frame, X
11977 @subsection @code{tdump}
11979 @cindex dump all data collected at tracepoint
11980 @cindex tracepoint data, display
11982 This command takes no arguments. It prints all the data collected at
11983 the current trace snapshot.
11986 (@value{GDBP}) @b{trace 444}
11987 (@value{GDBP}) @b{actions}
11988 Enter actions for tracepoint #2, one per line:
11989 > collect $regs, $locals, $args, gdb_long_test
11992 (@value{GDBP}) @b{tstart}
11994 (@value{GDBP}) @b{tfind line 444}
11995 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
11997 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
11999 (@value{GDBP}) @b{tdump}
12000 Data collected at tracepoint 2, trace frame 1:
12001 d0 0xc4aa0085 -995491707
12005 d4 0x71aea3d 119204413
12008 d7 0x380035 3670069
12009 a0 0x19e24a 1696330
12010 a1 0x3000668 50333288
12012 a3 0x322000 3284992
12013 a4 0x3000698 50333336
12014 a5 0x1ad3cc 1758156
12015 fp 0x30bf3c 0x30bf3c
12016 sp 0x30bf34 0x30bf34
12018 pc 0x20b2c8 0x20b2c8
12022 p = 0x20e5b4 "gdb-test"
12029 gdb_long_test = 17 '\021'
12034 @code{tdump} works by scanning the tracepoint's current collection
12035 actions and printing the value of each expression listed. So
12036 @code{tdump} can fail, if after a run, you change the tracepoint's
12037 actions to mention variables that were not collected during the run.
12039 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12040 uses the collected value of @code{$pc} to distinguish between trace
12041 frames that were collected at the tracepoint hit, and frames that were
12042 collected while stepping. This allows it to correctly choose whether
12043 to display the basic list of collections, or the collections from the
12044 body of the while-stepping loop. However, if @code{$pc} was not collected,
12045 then @code{tdump} will always attempt to dump using the basic collection
12046 list, and may fail if a while-stepping frame does not include all the
12047 same data that is collected at the tracepoint hit.
12048 @c This is getting pretty arcane, example would be good.
12050 @node save tracepoints
12051 @subsection @code{save tracepoints @var{filename}}
12052 @kindex save tracepoints
12053 @kindex save-tracepoints
12054 @cindex save tracepoints for future sessions
12056 This command saves all current tracepoint definitions together with
12057 their actions and passcounts, into a file @file{@var{filename}}
12058 suitable for use in a later debugging session. To read the saved
12059 tracepoint definitions, use the @code{source} command (@pxref{Command
12060 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12061 alias for @w{@code{save tracepoints}}
12063 @node Tracepoint Variables
12064 @section Convenience Variables for Tracepoints
12065 @cindex tracepoint variables
12066 @cindex convenience variables for tracepoints
12069 @vindex $trace_frame
12070 @item (int) $trace_frame
12071 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12072 snapshot is selected.
12074 @vindex $tracepoint
12075 @item (int) $tracepoint
12076 The tracepoint for the current trace snapshot.
12078 @vindex $trace_line
12079 @item (int) $trace_line
12080 The line number for the current trace snapshot.
12082 @vindex $trace_file
12083 @item (char []) $trace_file
12084 The source file for the current trace snapshot.
12086 @vindex $trace_func
12087 @item (char []) $trace_func
12088 The name of the function containing @code{$tracepoint}.
12091 Note: @code{$trace_file} is not suitable for use in @code{printf},
12092 use @code{output} instead.
12094 Here's a simple example of using these convenience variables for
12095 stepping through all the trace snapshots and printing some of their
12096 data. Note that these are not the same as trace state variables,
12097 which are managed by the target.
12100 (@value{GDBP}) @b{tfind start}
12102 (@value{GDBP}) @b{while $trace_frame != -1}
12103 > output $trace_file
12104 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12110 @section Using Trace Files
12111 @cindex trace files
12113 In some situations, the target running a trace experiment may no
12114 longer be available; perhaps it crashed, or the hardware was needed
12115 for a different activity. To handle these cases, you can arrange to
12116 dump the trace data into a file, and later use that file as a source
12117 of trace data, via the @code{target tfile} command.
12122 @item tsave [ -r ] @var{filename}
12123 Save the trace data to @var{filename}. By default, this command
12124 assumes that @var{filename} refers to the host filesystem, so if
12125 necessary @value{GDBN} will copy raw trace data up from the target and
12126 then save it. If the target supports it, you can also supply the
12127 optional argument @code{-r} (``remote'') to direct the target to save
12128 the data directly into @var{filename} in its own filesystem, which may be
12129 more efficient if the trace buffer is very large. (Note, however, that
12130 @code{target tfile} can only read from files accessible to the host.)
12132 @kindex target tfile
12134 @item target tfile @var{filename}
12135 Use the file named @var{filename} as a source of trace data. Commands
12136 that examine data work as they do with a live target, but it is not
12137 possible to run any new trace experiments. @code{tstatus} will report
12138 the state of the trace run at the moment the data was saved, as well
12139 as the current trace frame you are examining. @var{filename} must be
12140 on a filesystem accessible to the host.
12145 @chapter Debugging Programs That Use Overlays
12148 If your program is too large to fit completely in your target system's
12149 memory, you can sometimes use @dfn{overlays} to work around this
12150 problem. @value{GDBN} provides some support for debugging programs that
12154 * How Overlays Work:: A general explanation of overlays.
12155 * Overlay Commands:: Managing overlays in @value{GDBN}.
12156 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12157 mapped by asking the inferior.
12158 * Overlay Sample Program:: A sample program using overlays.
12161 @node How Overlays Work
12162 @section How Overlays Work
12163 @cindex mapped overlays
12164 @cindex unmapped overlays
12165 @cindex load address, overlay's
12166 @cindex mapped address
12167 @cindex overlay area
12169 Suppose you have a computer whose instruction address space is only 64
12170 kilobytes long, but which has much more memory which can be accessed by
12171 other means: special instructions, segment registers, or memory
12172 management hardware, for example. Suppose further that you want to
12173 adapt a program which is larger than 64 kilobytes to run on this system.
12175 One solution is to identify modules of your program which are relatively
12176 independent, and need not call each other directly; call these modules
12177 @dfn{overlays}. Separate the overlays from the main program, and place
12178 their machine code in the larger memory. Place your main program in
12179 instruction memory, but leave at least enough space there to hold the
12180 largest overlay as well.
12182 Now, to call a function located in an overlay, you must first copy that
12183 overlay's machine code from the large memory into the space set aside
12184 for it in the instruction memory, and then jump to its entry point
12187 @c NB: In the below the mapped area's size is greater or equal to the
12188 @c size of all overlays. This is intentional to remind the developer
12189 @c that overlays don't necessarily need to be the same size.
12193 Data Instruction Larger
12194 Address Space Address Space Address Space
12195 +-----------+ +-----------+ +-----------+
12197 +-----------+ +-----------+ +-----------+<-- overlay 1
12198 | program | | main | .----| overlay 1 | load address
12199 | variables | | program | | +-----------+
12200 | and heap | | | | | |
12201 +-----------+ | | | +-----------+<-- overlay 2
12202 | | +-----------+ | | | load address
12203 +-----------+ | | | .-| overlay 2 |
12205 mapped --->+-----------+ | | +-----------+
12206 address | | | | | |
12207 | overlay | <-' | | |
12208 | area | <---' +-----------+<-- overlay 3
12209 | | <---. | | load address
12210 +-----------+ `--| overlay 3 |
12217 @anchor{A code overlay}A code overlay
12221 The diagram (@pxref{A code overlay}) shows a system with separate data
12222 and instruction address spaces. To map an overlay, the program copies
12223 its code from the larger address space to the instruction address space.
12224 Since the overlays shown here all use the same mapped address, only one
12225 may be mapped at a time. For a system with a single address space for
12226 data and instructions, the diagram would be similar, except that the
12227 program variables and heap would share an address space with the main
12228 program and the overlay area.
12230 An overlay loaded into instruction memory and ready for use is called a
12231 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12232 instruction memory. An overlay not present (or only partially present)
12233 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12234 is its address in the larger memory. The mapped address is also called
12235 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12236 called the @dfn{load memory address}, or @dfn{LMA}.
12238 Unfortunately, overlays are not a completely transparent way to adapt a
12239 program to limited instruction memory. They introduce a new set of
12240 global constraints you must keep in mind as you design your program:
12245 Before calling or returning to a function in an overlay, your program
12246 must make sure that overlay is actually mapped. Otherwise, the call or
12247 return will transfer control to the right address, but in the wrong
12248 overlay, and your program will probably crash.
12251 If the process of mapping an overlay is expensive on your system, you
12252 will need to choose your overlays carefully to minimize their effect on
12253 your program's performance.
12256 The executable file you load onto your system must contain each
12257 overlay's instructions, appearing at the overlay's load address, not its
12258 mapped address. However, each overlay's instructions must be relocated
12259 and its symbols defined as if the overlay were at its mapped address.
12260 You can use GNU linker scripts to specify different load and relocation
12261 addresses for pieces of your program; see @ref{Overlay Description,,,
12262 ld.info, Using ld: the GNU linker}.
12265 The procedure for loading executable files onto your system must be able
12266 to load their contents into the larger address space as well as the
12267 instruction and data spaces.
12271 The overlay system described above is rather simple, and could be
12272 improved in many ways:
12277 If your system has suitable bank switch registers or memory management
12278 hardware, you could use those facilities to make an overlay's load area
12279 contents simply appear at their mapped address in instruction space.
12280 This would probably be faster than copying the overlay to its mapped
12281 area in the usual way.
12284 If your overlays are small enough, you could set aside more than one
12285 overlay area, and have more than one overlay mapped at a time.
12288 You can use overlays to manage data, as well as instructions. In
12289 general, data overlays are even less transparent to your design than
12290 code overlays: whereas code overlays only require care when you call or
12291 return to functions, data overlays require care every time you access
12292 the data. Also, if you change the contents of a data overlay, you
12293 must copy its contents back out to its load address before you can copy a
12294 different data overlay into the same mapped area.
12299 @node Overlay Commands
12300 @section Overlay Commands
12302 To use @value{GDBN}'s overlay support, each overlay in your program must
12303 correspond to a separate section of the executable file. The section's
12304 virtual memory address and load memory address must be the overlay's
12305 mapped and load addresses. Identifying overlays with sections allows
12306 @value{GDBN} to determine the appropriate address of a function or
12307 variable, depending on whether the overlay is mapped or not.
12309 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12310 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12315 Disable @value{GDBN}'s overlay support. When overlay support is
12316 disabled, @value{GDBN} assumes that all functions and variables are
12317 always present at their mapped addresses. By default, @value{GDBN}'s
12318 overlay support is disabled.
12320 @item overlay manual
12321 @cindex manual overlay debugging
12322 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12323 relies on you to tell it which overlays are mapped, and which are not,
12324 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12325 commands described below.
12327 @item overlay map-overlay @var{overlay}
12328 @itemx overlay map @var{overlay}
12329 @cindex map an overlay
12330 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12331 be the name of the object file section containing the overlay. When an
12332 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12333 functions and variables at their mapped addresses. @value{GDBN} assumes
12334 that any other overlays whose mapped ranges overlap that of
12335 @var{overlay} are now unmapped.
12337 @item overlay unmap-overlay @var{overlay}
12338 @itemx overlay unmap @var{overlay}
12339 @cindex unmap an overlay
12340 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12341 must be the name of the object file section containing the overlay.
12342 When an overlay is unmapped, @value{GDBN} assumes it can find the
12343 overlay's functions and variables at their load addresses.
12346 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12347 consults a data structure the overlay manager maintains in the inferior
12348 to see which overlays are mapped. For details, see @ref{Automatic
12349 Overlay Debugging}.
12351 @item overlay load-target
12352 @itemx overlay load
12353 @cindex reloading the overlay table
12354 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12355 re-reads the table @value{GDBN} automatically each time the inferior
12356 stops, so this command should only be necessary if you have changed the
12357 overlay mapping yourself using @value{GDBN}. This command is only
12358 useful when using automatic overlay debugging.
12360 @item overlay list-overlays
12361 @itemx overlay list
12362 @cindex listing mapped overlays
12363 Display a list of the overlays currently mapped, along with their mapped
12364 addresses, load addresses, and sizes.
12368 Normally, when @value{GDBN} prints a code address, it includes the name
12369 of the function the address falls in:
12372 (@value{GDBP}) print main
12373 $3 = @{int ()@} 0x11a0 <main>
12376 When overlay debugging is enabled, @value{GDBN} recognizes code in
12377 unmapped overlays, and prints the names of unmapped functions with
12378 asterisks around them. For example, if @code{foo} is a function in an
12379 unmapped overlay, @value{GDBN} prints it this way:
12382 (@value{GDBP}) overlay list
12383 No sections are mapped.
12384 (@value{GDBP}) print foo
12385 $5 = @{int (int)@} 0x100000 <*foo*>
12388 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12392 (@value{GDBP}) overlay list
12393 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12394 mapped at 0x1016 - 0x104a
12395 (@value{GDBP}) print foo
12396 $6 = @{int (int)@} 0x1016 <foo>
12399 When overlay debugging is enabled, @value{GDBN} can find the correct
12400 address for functions and variables in an overlay, whether or not the
12401 overlay is mapped. This allows most @value{GDBN} commands, like
12402 @code{break} and @code{disassemble}, to work normally, even on unmapped
12403 code. However, @value{GDBN}'s breakpoint support has some limitations:
12407 @cindex breakpoints in overlays
12408 @cindex overlays, setting breakpoints in
12409 You can set breakpoints in functions in unmapped overlays, as long as
12410 @value{GDBN} can write to the overlay at its load address.
12412 @value{GDBN} can not set hardware or simulator-based breakpoints in
12413 unmapped overlays. However, if you set a breakpoint at the end of your
12414 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12415 you are using manual overlay management), @value{GDBN} will re-set its
12416 breakpoints properly.
12420 @node Automatic Overlay Debugging
12421 @section Automatic Overlay Debugging
12422 @cindex automatic overlay debugging
12424 @value{GDBN} can automatically track which overlays are mapped and which
12425 are not, given some simple co-operation from the overlay manager in the
12426 inferior. If you enable automatic overlay debugging with the
12427 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12428 looks in the inferior's memory for certain variables describing the
12429 current state of the overlays.
12431 Here are the variables your overlay manager must define to support
12432 @value{GDBN}'s automatic overlay debugging:
12436 @item @code{_ovly_table}:
12437 This variable must be an array of the following structures:
12442 /* The overlay's mapped address. */
12445 /* The size of the overlay, in bytes. */
12446 unsigned long size;
12448 /* The overlay's load address. */
12451 /* Non-zero if the overlay is currently mapped;
12453 unsigned long mapped;
12457 @item @code{_novlys}:
12458 This variable must be a four-byte signed integer, holding the total
12459 number of elements in @code{_ovly_table}.
12463 To decide whether a particular overlay is mapped or not, @value{GDBN}
12464 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12465 @code{lma} members equal the VMA and LMA of the overlay's section in the
12466 executable file. When @value{GDBN} finds a matching entry, it consults
12467 the entry's @code{mapped} member to determine whether the overlay is
12470 In addition, your overlay manager may define a function called
12471 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12472 will silently set a breakpoint there. If the overlay manager then
12473 calls this function whenever it has changed the overlay table, this
12474 will enable @value{GDBN} to accurately keep track of which overlays
12475 are in program memory, and update any breakpoints that may be set
12476 in overlays. This will allow breakpoints to work even if the
12477 overlays are kept in ROM or other non-writable memory while they
12478 are not being executed.
12480 @node Overlay Sample Program
12481 @section Overlay Sample Program
12482 @cindex overlay example program
12484 When linking a program which uses overlays, you must place the overlays
12485 at their load addresses, while relocating them to run at their mapped
12486 addresses. To do this, you must write a linker script (@pxref{Overlay
12487 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12488 since linker scripts are specific to a particular host system, target
12489 architecture, and target memory layout, this manual cannot provide
12490 portable sample code demonstrating @value{GDBN}'s overlay support.
12492 However, the @value{GDBN} source distribution does contain an overlaid
12493 program, with linker scripts for a few systems, as part of its test
12494 suite. The program consists of the following files from
12495 @file{gdb/testsuite/gdb.base}:
12499 The main program file.
12501 A simple overlay manager, used by @file{overlays.c}.
12506 Overlay modules, loaded and used by @file{overlays.c}.
12509 Linker scripts for linking the test program on the @code{d10v-elf}
12510 and @code{m32r-elf} targets.
12513 You can build the test program using the @code{d10v-elf} GCC
12514 cross-compiler like this:
12517 $ d10v-elf-gcc -g -c overlays.c
12518 $ d10v-elf-gcc -g -c ovlymgr.c
12519 $ d10v-elf-gcc -g -c foo.c
12520 $ d10v-elf-gcc -g -c bar.c
12521 $ d10v-elf-gcc -g -c baz.c
12522 $ d10v-elf-gcc -g -c grbx.c
12523 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12524 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12527 The build process is identical for any other architecture, except that
12528 you must substitute the appropriate compiler and linker script for the
12529 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12533 @chapter Using @value{GDBN} with Different Languages
12536 Although programming languages generally have common aspects, they are
12537 rarely expressed in the same manner. For instance, in ANSI C,
12538 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12539 Modula-2, it is accomplished by @code{p^}. Values can also be
12540 represented (and displayed) differently. Hex numbers in C appear as
12541 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12543 @cindex working language
12544 Language-specific information is built into @value{GDBN} for some languages,
12545 allowing you to express operations like the above in your program's
12546 native language, and allowing @value{GDBN} to output values in a manner
12547 consistent with the syntax of your program's native language. The
12548 language you use to build expressions is called the @dfn{working
12552 * Setting:: Switching between source languages
12553 * Show:: Displaying the language
12554 * Checks:: Type and range checks
12555 * Supported Languages:: Supported languages
12556 * Unsupported Languages:: Unsupported languages
12560 @section Switching Between Source Languages
12562 There are two ways to control the working language---either have @value{GDBN}
12563 set it automatically, or select it manually yourself. You can use the
12564 @code{set language} command for either purpose. On startup, @value{GDBN}
12565 defaults to setting the language automatically. The working language is
12566 used to determine how expressions you type are interpreted, how values
12569 In addition to the working language, every source file that
12570 @value{GDBN} knows about has its own working language. For some object
12571 file formats, the compiler might indicate which language a particular
12572 source file is in. However, most of the time @value{GDBN} infers the
12573 language from the name of the file. The language of a source file
12574 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12575 show each frame appropriately for its own language. There is no way to
12576 set the language of a source file from within @value{GDBN}, but you can
12577 set the language associated with a filename extension. @xref{Show, ,
12578 Displaying the Language}.
12580 This is most commonly a problem when you use a program, such
12581 as @code{cfront} or @code{f2c}, that generates C but is written in
12582 another language. In that case, make the
12583 program use @code{#line} directives in its C output; that way
12584 @value{GDBN} will know the correct language of the source code of the original
12585 program, and will display that source code, not the generated C code.
12588 * Filenames:: Filename extensions and languages.
12589 * Manually:: Setting the working language manually
12590 * Automatically:: Having @value{GDBN} infer the source language
12594 @subsection List of Filename Extensions and Languages
12596 If a source file name ends in one of the following extensions, then
12597 @value{GDBN} infers that its language is the one indicated.
12615 C@t{++} source file
12621 Objective-C source file
12625 Fortran source file
12628 Modula-2 source file
12632 Assembler source file. This actually behaves almost like C, but
12633 @value{GDBN} does not skip over function prologues when stepping.
12636 In addition, you may set the language associated with a filename
12637 extension. @xref{Show, , Displaying the Language}.
12640 @subsection Setting the Working Language
12642 If you allow @value{GDBN} to set the language automatically,
12643 expressions are interpreted the same way in your debugging session and
12646 @kindex set language
12647 If you wish, you may set the language manually. To do this, issue the
12648 command @samp{set language @var{lang}}, where @var{lang} is the name of
12649 a language, such as
12650 @code{c} or @code{modula-2}.
12651 For a list of the supported languages, type @samp{set language}.
12653 Setting the language manually prevents @value{GDBN} from updating the working
12654 language automatically. This can lead to confusion if you try
12655 to debug a program when the working language is not the same as the
12656 source language, when an expression is acceptable to both
12657 languages---but means different things. For instance, if the current
12658 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12666 might not have the effect you intended. In C, this means to add
12667 @code{b} and @code{c} and place the result in @code{a}. The result
12668 printed would be the value of @code{a}. In Modula-2, this means to compare
12669 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12671 @node Automatically
12672 @subsection Having @value{GDBN} Infer the Source Language
12674 To have @value{GDBN} set the working language automatically, use
12675 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12676 then infers the working language. That is, when your program stops in a
12677 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12678 working language to the language recorded for the function in that
12679 frame. If the language for a frame is unknown (that is, if the function
12680 or block corresponding to the frame was defined in a source file that
12681 does not have a recognized extension), the current working language is
12682 not changed, and @value{GDBN} issues a warning.
12684 This may not seem necessary for most programs, which are written
12685 entirely in one source language. However, program modules and libraries
12686 written in one source language can be used by a main program written in
12687 a different source language. Using @samp{set language auto} in this
12688 case frees you from having to set the working language manually.
12691 @section Displaying the Language
12693 The following commands help you find out which language is the
12694 working language, and also what language source files were written in.
12697 @item show language
12698 @kindex show language
12699 Display the current working language. This is the
12700 language you can use with commands such as @code{print} to
12701 build and compute expressions that may involve variables in your program.
12704 @kindex info frame@r{, show the source language}
12705 Display the source language for this frame. This language becomes the
12706 working language if you use an identifier from this frame.
12707 @xref{Frame Info, ,Information about a Frame}, to identify the other
12708 information listed here.
12711 @kindex info source@r{, show the source language}
12712 Display the source language of this source file.
12713 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12714 information listed here.
12717 In unusual circumstances, you may have source files with extensions
12718 not in the standard list. You can then set the extension associated
12719 with a language explicitly:
12722 @item set extension-language @var{ext} @var{language}
12723 @kindex set extension-language
12724 Tell @value{GDBN} that source files with extension @var{ext} are to be
12725 assumed as written in the source language @var{language}.
12727 @item info extensions
12728 @kindex info extensions
12729 List all the filename extensions and the associated languages.
12733 @section Type and Range Checking
12735 Some languages are designed to guard you against making seemingly common
12736 errors through a series of compile- and run-time checks. These include
12737 checking the type of arguments to functions and operators and making
12738 sure mathematical overflows are caught at run time. Checks such as
12739 these help to ensure a program's correctness once it has been compiled
12740 by eliminating type mismatches and providing active checks for range
12741 errors when your program is running.
12743 By default @value{GDBN} checks for these errors according to the
12744 rules of the current source language. Although @value{GDBN} does not check
12745 the statements in your program, it can check expressions entered directly
12746 into @value{GDBN} for evaluation via the @code{print} command, for example.
12749 * Type Checking:: An overview of type checking
12750 * Range Checking:: An overview of range checking
12753 @cindex type checking
12754 @cindex checks, type
12755 @node Type Checking
12756 @subsection An Overview of Type Checking
12758 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12759 arguments to operators and functions have to be of the correct type,
12760 otherwise an error occurs. These checks prevent type mismatch
12761 errors from ever causing any run-time problems. For example,
12764 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12766 (@value{GDBP}) print obj.my_method (0)
12769 (@value{GDBP}) print obj.my_method (0x1234)
12770 Cannot resolve method klass::my_method to any overloaded instance
12773 The second example fails because in C@t{++} the integer constant
12774 @samp{0x1234} is not type-compatible with the pointer parameter type.
12776 For the expressions you use in @value{GDBN} commands, you can tell
12777 @value{GDBN} to not enforce strict type checking or
12778 to treat any mismatches as errors and abandon the expression;
12779 When type checking is disabled, @value{GDBN} successfully evaluates
12780 expressions like the second example above.
12782 Even if type checking is off, there may be other reasons
12783 related to type that prevent @value{GDBN} from evaluating an expression.
12784 For instance, @value{GDBN} does not know how to add an @code{int} and
12785 a @code{struct foo}. These particular type errors have nothing to do
12786 with the language in use and usually arise from expressions which make
12787 little sense to evaluate anyway.
12789 @value{GDBN} provides some additional commands for controlling type checking:
12791 @kindex set check type
12792 @kindex show check type
12794 @item set check type on
12795 @itemx set check type off
12796 Set strict type checking on or off. If any type mismatches occur in
12797 evaluating an expression while type checking is on, @value{GDBN} prints a
12798 message and aborts evaluation of the expression.
12800 @item show check type
12801 Show the current setting of type checking and whether @value{GDBN}
12802 is enforcing strict type checking rules.
12805 @cindex range checking
12806 @cindex checks, range
12807 @node Range Checking
12808 @subsection An Overview of Range Checking
12810 In some languages (such as Modula-2), it is an error to exceed the
12811 bounds of a type; this is enforced with run-time checks. Such range
12812 checking is meant to ensure program correctness by making sure
12813 computations do not overflow, or indices on an array element access do
12814 not exceed the bounds of the array.
12816 For expressions you use in @value{GDBN} commands, you can tell
12817 @value{GDBN} to treat range errors in one of three ways: ignore them,
12818 always treat them as errors and abandon the expression, or issue
12819 warnings but evaluate the expression anyway.
12821 A range error can result from numerical overflow, from exceeding an
12822 array index bound, or when you type a constant that is not a member
12823 of any type. Some languages, however, do not treat overflows as an
12824 error. In many implementations of C, mathematical overflow causes the
12825 result to ``wrap around'' to lower values---for example, if @var{m} is
12826 the largest integer value, and @var{s} is the smallest, then
12829 @var{m} + 1 @result{} @var{s}
12832 This, too, is specific to individual languages, and in some cases
12833 specific to individual compilers or machines. @xref{Supported Languages, ,
12834 Supported Languages}, for further details on specific languages.
12836 @value{GDBN} provides some additional commands for controlling the range checker:
12838 @kindex set check range
12839 @kindex show check range
12841 @item set check range auto
12842 Set range checking on or off based on the current working language.
12843 @xref{Supported Languages, ,Supported Languages}, for the default settings for
12846 @item set check range on
12847 @itemx set check range off
12848 Set range checking on or off, overriding the default setting for the
12849 current working language. A warning is issued if the setting does not
12850 match the language default. If a range error occurs and range checking is on,
12851 then a message is printed and evaluation of the expression is aborted.
12853 @item set check range warn
12854 Output messages when the @value{GDBN} range checker detects a range error,
12855 but attempt to evaluate the expression anyway. Evaluating the
12856 expression may still be impossible for other reasons, such as accessing
12857 memory that the process does not own (a typical example from many Unix
12861 Show the current setting of the range checker, and whether or not it is
12862 being set automatically by @value{GDBN}.
12865 @node Supported Languages
12866 @section Supported Languages
12868 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
12869 OpenCL C, Pascal, assembly, Modula-2, and Ada.
12870 @c This is false ...
12871 Some @value{GDBN} features may be used in expressions regardless of the
12872 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
12873 and the @samp{@{type@}addr} construct (@pxref{Expressions,
12874 ,Expressions}) can be used with the constructs of any supported
12877 The following sections detail to what degree each source language is
12878 supported by @value{GDBN}. These sections are not meant to be language
12879 tutorials or references, but serve only as a reference guide to what the
12880 @value{GDBN} expression parser accepts, and what input and output
12881 formats should look like for different languages. There are many good
12882 books written on each of these languages; please look to these for a
12883 language reference or tutorial.
12886 * C:: C and C@t{++}
12889 * Objective-C:: Objective-C
12890 * OpenCL C:: OpenCL C
12891 * Fortran:: Fortran
12893 * Modula-2:: Modula-2
12898 @subsection C and C@t{++}
12900 @cindex C and C@t{++}
12901 @cindex expressions in C or C@t{++}
12903 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
12904 to both languages. Whenever this is the case, we discuss those languages
12908 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
12909 @cindex @sc{gnu} C@t{++}
12910 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
12911 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
12912 effectively, you must compile your C@t{++} programs with a supported
12913 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
12914 compiler (@code{aCC}).
12917 * C Operators:: C and C@t{++} operators
12918 * C Constants:: C and C@t{++} constants
12919 * C Plus Plus Expressions:: C@t{++} expressions
12920 * C Defaults:: Default settings for C and C@t{++}
12921 * C Checks:: C and C@t{++} type and range checks
12922 * Debugging C:: @value{GDBN} and C
12923 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
12924 * Decimal Floating Point:: Numbers in Decimal Floating Point format
12928 @subsubsection C and C@t{++} Operators
12930 @cindex C and C@t{++} operators
12932 Operators must be defined on values of specific types. For instance,
12933 @code{+} is defined on numbers, but not on structures. Operators are
12934 often defined on groups of types.
12936 For the purposes of C and C@t{++}, the following definitions hold:
12941 @emph{Integral types} include @code{int} with any of its storage-class
12942 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
12945 @emph{Floating-point types} include @code{float}, @code{double}, and
12946 @code{long double} (if supported by the target platform).
12949 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
12952 @emph{Scalar types} include all of the above.
12957 The following operators are supported. They are listed here
12958 in order of increasing precedence:
12962 The comma or sequencing operator. Expressions in a comma-separated list
12963 are evaluated from left to right, with the result of the entire
12964 expression being the last expression evaluated.
12967 Assignment. The value of an assignment expression is the value
12968 assigned. Defined on scalar types.
12971 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
12972 and translated to @w{@code{@var{a} = @var{a op b}}}.
12973 @w{@code{@var{op}=}} and @code{=} have the same precedence.
12974 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
12975 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
12978 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
12979 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
12983 Logical @sc{or}. Defined on integral types.
12986 Logical @sc{and}. Defined on integral types.
12989 Bitwise @sc{or}. Defined on integral types.
12992 Bitwise exclusive-@sc{or}. Defined on integral types.
12995 Bitwise @sc{and}. Defined on integral types.
12998 Equality and inequality. Defined on scalar types. The value of these
12999 expressions is 0 for false and non-zero for true.
13001 @item <@r{, }>@r{, }<=@r{, }>=
13002 Less than, greater than, less than or equal, greater than or equal.
13003 Defined on scalar types. The value of these expressions is 0 for false
13004 and non-zero for true.
13007 left shift, and right shift. Defined on integral types.
13010 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13013 Addition and subtraction. Defined on integral types, floating-point types and
13016 @item *@r{, }/@r{, }%
13017 Multiplication, division, and modulus. Multiplication and division are
13018 defined on integral and floating-point types. Modulus is defined on
13022 Increment and decrement. When appearing before a variable, the
13023 operation is performed before the variable is used in an expression;
13024 when appearing after it, the variable's value is used before the
13025 operation takes place.
13028 Pointer dereferencing. Defined on pointer types. Same precedence as
13032 Address operator. Defined on variables. Same precedence as @code{++}.
13034 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13035 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13036 to examine the address
13037 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13041 Negative. Defined on integral and floating-point types. Same
13042 precedence as @code{++}.
13045 Logical negation. Defined on integral types. Same precedence as
13049 Bitwise complement operator. Defined on integral types. Same precedence as
13054 Structure member, and pointer-to-structure member. For convenience,
13055 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13056 pointer based on the stored type information.
13057 Defined on @code{struct} and @code{union} data.
13060 Dereferences of pointers to members.
13063 Array indexing. @code{@var{a}[@var{i}]} is defined as
13064 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13067 Function parameter list. Same precedence as @code{->}.
13070 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13071 and @code{class} types.
13074 Doubled colons also represent the @value{GDBN} scope operator
13075 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13079 If an operator is redefined in the user code, @value{GDBN} usually
13080 attempts to invoke the redefined version instead of using the operator's
13081 predefined meaning.
13084 @subsubsection C and C@t{++} Constants
13086 @cindex C and C@t{++} constants
13088 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13093 Integer constants are a sequence of digits. Octal constants are
13094 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13095 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13096 @samp{l}, specifying that the constant should be treated as a
13100 Floating point constants are a sequence of digits, followed by a decimal
13101 point, followed by a sequence of digits, and optionally followed by an
13102 exponent. An exponent is of the form:
13103 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13104 sequence of digits. The @samp{+} is optional for positive exponents.
13105 A floating-point constant may also end with a letter @samp{f} or
13106 @samp{F}, specifying that the constant should be treated as being of
13107 the @code{float} (as opposed to the default @code{double}) type; or with
13108 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13112 Enumerated constants consist of enumerated identifiers, or their
13113 integral equivalents.
13116 Character constants are a single character surrounded by single quotes
13117 (@code{'}), or a number---the ordinal value of the corresponding character
13118 (usually its @sc{ascii} value). Within quotes, the single character may
13119 be represented by a letter or by @dfn{escape sequences}, which are of
13120 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13121 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13122 @samp{@var{x}} is a predefined special character---for example,
13123 @samp{\n} for newline.
13125 Wide character constants can be written by prefixing a character
13126 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13127 form of @samp{x}. The target wide character set is used when
13128 computing the value of this constant (@pxref{Character Sets}).
13131 String constants are a sequence of character constants surrounded by
13132 double quotes (@code{"}). Any valid character constant (as described
13133 above) may appear. Double quotes within the string must be preceded by
13134 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13137 Wide string constants can be written by prefixing a string constant
13138 with @samp{L}, as in C. The target wide character set is used when
13139 computing the value of this constant (@pxref{Character Sets}).
13142 Pointer constants are an integral value. You can also write pointers
13143 to constants using the C operator @samp{&}.
13146 Array constants are comma-separated lists surrounded by braces @samp{@{}
13147 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13148 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13149 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13152 @node C Plus Plus Expressions
13153 @subsubsection C@t{++} Expressions
13155 @cindex expressions in C@t{++}
13156 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13158 @cindex debugging C@t{++} programs
13159 @cindex C@t{++} compilers
13160 @cindex debug formats and C@t{++}
13161 @cindex @value{NGCC} and C@t{++}
13163 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13164 the proper compiler and the proper debug format. Currently,
13165 @value{GDBN} works best when debugging C@t{++} code that is compiled
13166 with the most recent version of @value{NGCC} possible. The DWARF
13167 debugging format is preferred; @value{NGCC} defaults to this on most
13168 popular platforms. Other compilers and/or debug formats are likely to
13169 work badly or not at all when using @value{GDBN} to debug C@t{++}
13170 code. @xref{Compilation}.
13175 @cindex member functions
13177 Member function calls are allowed; you can use expressions like
13180 count = aml->GetOriginal(x, y)
13183 @vindex this@r{, inside C@t{++} member functions}
13184 @cindex namespace in C@t{++}
13186 While a member function is active (in the selected stack frame), your
13187 expressions have the same namespace available as the member function;
13188 that is, @value{GDBN} allows implicit references to the class instance
13189 pointer @code{this} following the same rules as C@t{++}. @code{using}
13190 declarations in the current scope are also respected by @value{GDBN}.
13192 @cindex call overloaded functions
13193 @cindex overloaded functions, calling
13194 @cindex type conversions in C@t{++}
13196 You can call overloaded functions; @value{GDBN} resolves the function
13197 call to the right definition, with some restrictions. @value{GDBN} does not
13198 perform overload resolution involving user-defined type conversions,
13199 calls to constructors, or instantiations of templates that do not exist
13200 in the program. It also cannot handle ellipsis argument lists or
13203 It does perform integral conversions and promotions, floating-point
13204 promotions, arithmetic conversions, pointer conversions, conversions of
13205 class objects to base classes, and standard conversions such as those of
13206 functions or arrays to pointers; it requires an exact match on the
13207 number of function arguments.
13209 Overload resolution is always performed, unless you have specified
13210 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13211 ,@value{GDBN} Features for C@t{++}}.
13213 You must specify @code{set overload-resolution off} in order to use an
13214 explicit function signature to call an overloaded function, as in
13216 p 'foo(char,int)'('x', 13)
13219 The @value{GDBN} command-completion facility can simplify this;
13220 see @ref{Completion, ,Command Completion}.
13222 @cindex reference declarations
13224 @value{GDBN} understands variables declared as C@t{++} references; you can use
13225 them in expressions just as you do in C@t{++} source---they are automatically
13228 In the parameter list shown when @value{GDBN} displays a frame, the values of
13229 reference variables are not displayed (unlike other variables); this
13230 avoids clutter, since references are often used for large structures.
13231 The @emph{address} of a reference variable is always shown, unless
13232 you have specified @samp{set print address off}.
13235 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13236 expressions can use it just as expressions in your program do. Since
13237 one scope may be defined in another, you can use @code{::} repeatedly if
13238 necessary, for example in an expression like
13239 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13240 resolving name scope by reference to source files, in both C and C@t{++}
13241 debugging (@pxref{Variables, ,Program Variables}).
13244 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13249 @subsubsection C and C@t{++} Defaults
13251 @cindex C and C@t{++} defaults
13253 If you allow @value{GDBN} to set range checking automatically, it
13254 defaults to @code{off} whenever the working language changes to
13255 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13256 selects the working language.
13258 If you allow @value{GDBN} to set the language automatically, it
13259 recognizes source files whose names end with @file{.c}, @file{.C}, or
13260 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13261 these files, it sets the working language to C or C@t{++}.
13262 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13263 for further details.
13266 @subsubsection C and C@t{++} Type and Range Checks
13268 @cindex C and C@t{++} checks
13270 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13271 checking is used. However, if you turn type checking off, @value{GDBN}
13272 will allow certain non-standard conversions, such as promoting integer
13273 constants to pointers.
13275 Range checking, if turned on, is done on mathematical operations. Array
13276 indices are not checked, since they are often used to index a pointer
13277 that is not itself an array.
13280 @subsubsection @value{GDBN} and C
13282 The @code{set print union} and @code{show print union} commands apply to
13283 the @code{union} type. When set to @samp{on}, any @code{union} that is
13284 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13285 appears as @samp{@{...@}}.
13287 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13288 with pointers and a memory allocation function. @xref{Expressions,
13291 @node Debugging C Plus Plus
13292 @subsubsection @value{GDBN} Features for C@t{++}
13294 @cindex commands for C@t{++}
13296 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13297 designed specifically for use with C@t{++}. Here is a summary:
13300 @cindex break in overloaded functions
13301 @item @r{breakpoint menus}
13302 When you want a breakpoint in a function whose name is overloaded,
13303 @value{GDBN} has the capability to display a menu of possible breakpoint
13304 locations to help you specify which function definition you want.
13305 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13307 @cindex overloading in C@t{++}
13308 @item rbreak @var{regex}
13309 Setting breakpoints using regular expressions is helpful for setting
13310 breakpoints on overloaded functions that are not members of any special
13312 @xref{Set Breaks, ,Setting Breakpoints}.
13314 @cindex C@t{++} exception handling
13317 Debug C@t{++} exception handling using these commands. @xref{Set
13318 Catchpoints, , Setting Catchpoints}.
13320 @cindex inheritance
13321 @item ptype @var{typename}
13322 Print inheritance relationships as well as other information for type
13324 @xref{Symbols, ,Examining the Symbol Table}.
13326 @item info vtbl @var{expression}.
13327 The @code{info vtbl} command can be used to display the virtual
13328 method tables of the object computed by @var{expression}. This shows
13329 one entry per virtual table; there may be multiple virtual tables when
13330 multiple inheritance is in use.
13332 @cindex C@t{++} symbol display
13333 @item set print demangle
13334 @itemx show print demangle
13335 @itemx set print asm-demangle
13336 @itemx show print asm-demangle
13337 Control whether C@t{++} symbols display in their source form, both when
13338 displaying code as C@t{++} source and when displaying disassemblies.
13339 @xref{Print Settings, ,Print Settings}.
13341 @item set print object
13342 @itemx show print object
13343 Choose whether to print derived (actual) or declared types of objects.
13344 @xref{Print Settings, ,Print Settings}.
13346 @item set print vtbl
13347 @itemx show print vtbl
13348 Control the format for printing virtual function tables.
13349 @xref{Print Settings, ,Print Settings}.
13350 (The @code{vtbl} commands do not work on programs compiled with the HP
13351 ANSI C@t{++} compiler (@code{aCC}).)
13353 @kindex set overload-resolution
13354 @cindex overloaded functions, overload resolution
13355 @item set overload-resolution on
13356 Enable overload resolution for C@t{++} expression evaluation. The default
13357 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13358 and searches for a function whose signature matches the argument types,
13359 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13360 Expressions, ,C@t{++} Expressions}, for details).
13361 If it cannot find a match, it emits a message.
13363 @item set overload-resolution off
13364 Disable overload resolution for C@t{++} expression evaluation. For
13365 overloaded functions that are not class member functions, @value{GDBN}
13366 chooses the first function of the specified name that it finds in the
13367 symbol table, whether or not its arguments are of the correct type. For
13368 overloaded functions that are class member functions, @value{GDBN}
13369 searches for a function whose signature @emph{exactly} matches the
13372 @kindex show overload-resolution
13373 @item show overload-resolution
13374 Show the current setting of overload resolution.
13376 @item @r{Overloaded symbol names}
13377 You can specify a particular definition of an overloaded symbol, using
13378 the same notation that is used to declare such symbols in C@t{++}: type
13379 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13380 also use the @value{GDBN} command-line word completion facilities to list the
13381 available choices, or to finish the type list for you.
13382 @xref{Completion,, Command Completion}, for details on how to do this.
13385 @node Decimal Floating Point
13386 @subsubsection Decimal Floating Point format
13387 @cindex decimal floating point format
13389 @value{GDBN} can examine, set and perform computations with numbers in
13390 decimal floating point format, which in the C language correspond to the
13391 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13392 specified by the extension to support decimal floating-point arithmetic.
13394 There are two encodings in use, depending on the architecture: BID (Binary
13395 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13396 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13399 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13400 to manipulate decimal floating point numbers, it is not possible to convert
13401 (using a cast, for example) integers wider than 32-bit to decimal float.
13403 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13404 point computations, error checking in decimal float operations ignores
13405 underflow, overflow and divide by zero exceptions.
13407 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13408 to inspect @code{_Decimal128} values stored in floating point registers.
13409 See @ref{PowerPC,,PowerPC} for more details.
13415 @value{GDBN} can be used to debug programs written in D and compiled with
13416 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13417 specific feature --- dynamic arrays.
13422 @cindex Go (programming language)
13423 @value{GDBN} can be used to debug programs written in Go and compiled with
13424 @file{gccgo} or @file{6g} compilers.
13426 Here is a summary of the Go-specific features and restrictions:
13429 @cindex current Go package
13430 @item The current Go package
13431 The name of the current package does not need to be specified when
13432 specifying global variables and functions.
13434 For example, given the program:
13438 var myglob = "Shall we?"
13444 When stopped inside @code{main} either of these work:
13448 (gdb) p main.myglob
13451 @cindex builtin Go types
13452 @item Builtin Go types
13453 The @code{string} type is recognized by @value{GDBN} and is printed
13456 @cindex builtin Go functions
13457 @item Builtin Go functions
13458 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13459 function and handles it internally.
13461 @cindex restrictions on Go expressions
13462 @item Restrictions on Go expressions
13463 All Go operators are supported except @code{&^}.
13464 The Go @code{_} ``blank identifier'' is not supported.
13465 Automatic dereferencing of pointers is not supported.
13469 @subsection Objective-C
13471 @cindex Objective-C
13472 This section provides information about some commands and command
13473 options that are useful for debugging Objective-C code. See also
13474 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13475 few more commands specific to Objective-C support.
13478 * Method Names in Commands::
13479 * The Print Command with Objective-C::
13482 @node Method Names in Commands
13483 @subsubsection Method Names in Commands
13485 The following commands have been extended to accept Objective-C method
13486 names as line specifications:
13488 @kindex clear@r{, and Objective-C}
13489 @kindex break@r{, and Objective-C}
13490 @kindex info line@r{, and Objective-C}
13491 @kindex jump@r{, and Objective-C}
13492 @kindex list@r{, and Objective-C}
13496 @item @code{info line}
13501 A fully qualified Objective-C method name is specified as
13504 -[@var{Class} @var{methodName}]
13507 where the minus sign is used to indicate an instance method and a
13508 plus sign (not shown) is used to indicate a class method. The class
13509 name @var{Class} and method name @var{methodName} are enclosed in
13510 brackets, similar to the way messages are specified in Objective-C
13511 source code. For example, to set a breakpoint at the @code{create}
13512 instance method of class @code{Fruit} in the program currently being
13516 break -[Fruit create]
13519 To list ten program lines around the @code{initialize} class method,
13523 list +[NSText initialize]
13526 In the current version of @value{GDBN}, the plus or minus sign is
13527 required. In future versions of @value{GDBN}, the plus or minus
13528 sign will be optional, but you can use it to narrow the search. It
13529 is also possible to specify just a method name:
13535 You must specify the complete method name, including any colons. If
13536 your program's source files contain more than one @code{create} method,
13537 you'll be presented with a numbered list of classes that implement that
13538 method. Indicate your choice by number, or type @samp{0} to exit if
13541 As another example, to clear a breakpoint established at the
13542 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13545 clear -[NSWindow makeKeyAndOrderFront:]
13548 @node The Print Command with Objective-C
13549 @subsubsection The Print Command With Objective-C
13550 @cindex Objective-C, print objects
13551 @kindex print-object
13552 @kindex po @r{(@code{print-object})}
13554 The print command has also been extended to accept methods. For example:
13557 print -[@var{object} hash]
13560 @cindex print an Objective-C object description
13561 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13563 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13564 and print the result. Also, an additional command has been added,
13565 @code{print-object} or @code{po} for short, which is meant to print
13566 the description of an object. However, this command may only work
13567 with certain Objective-C libraries that have a particular hook
13568 function, @code{_NSPrintForDebugger}, defined.
13571 @subsection OpenCL C
13574 This section provides information about @value{GDBN}s OpenCL C support.
13577 * OpenCL C Datatypes::
13578 * OpenCL C Expressions::
13579 * OpenCL C Operators::
13582 @node OpenCL C Datatypes
13583 @subsubsection OpenCL C Datatypes
13585 @cindex OpenCL C Datatypes
13586 @value{GDBN} supports the builtin scalar and vector datatypes specified
13587 by OpenCL 1.1. In addition the half- and double-precision floating point
13588 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13589 extensions are also known to @value{GDBN}.
13591 @node OpenCL C Expressions
13592 @subsubsection OpenCL C Expressions
13594 @cindex OpenCL C Expressions
13595 @value{GDBN} supports accesses to vector components including the access as
13596 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13597 supported by @value{GDBN} can be used as well.
13599 @node OpenCL C Operators
13600 @subsubsection OpenCL C Operators
13602 @cindex OpenCL C Operators
13603 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13607 @subsection Fortran
13608 @cindex Fortran-specific support in @value{GDBN}
13610 @value{GDBN} can be used to debug programs written in Fortran, but it
13611 currently supports only the features of Fortran 77 language.
13613 @cindex trailing underscore, in Fortran symbols
13614 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13615 among them) append an underscore to the names of variables and
13616 functions. When you debug programs compiled by those compilers, you
13617 will need to refer to variables and functions with a trailing
13621 * Fortran Operators:: Fortran operators and expressions
13622 * Fortran Defaults:: Default settings for Fortran
13623 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13626 @node Fortran Operators
13627 @subsubsection Fortran Operators and Expressions
13629 @cindex Fortran operators and expressions
13631 Operators must be defined on values of specific types. For instance,
13632 @code{+} is defined on numbers, but not on characters or other non-
13633 arithmetic types. Operators are often defined on groups of types.
13637 The exponentiation operator. It raises the first operand to the power
13641 The range operator. Normally used in the form of array(low:high) to
13642 represent a section of array.
13645 The access component operator. Normally used to access elements in derived
13646 types. Also suitable for unions. As unions aren't part of regular Fortran,
13647 this can only happen when accessing a register that uses a gdbarch-defined
13651 @node Fortran Defaults
13652 @subsubsection Fortran Defaults
13654 @cindex Fortran Defaults
13656 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13657 default uses case-insensitive matches for Fortran symbols. You can
13658 change that with the @samp{set case-insensitive} command, see
13659 @ref{Symbols}, for the details.
13661 @node Special Fortran Commands
13662 @subsubsection Special Fortran Commands
13664 @cindex Special Fortran commands
13666 @value{GDBN} has some commands to support Fortran-specific features,
13667 such as displaying common blocks.
13670 @cindex @code{COMMON} blocks, Fortran
13671 @kindex info common
13672 @item info common @r{[}@var{common-name}@r{]}
13673 This command prints the values contained in the Fortran @code{COMMON}
13674 block whose name is @var{common-name}. With no argument, the names of
13675 all @code{COMMON} blocks visible at the current program location are
13682 @cindex Pascal support in @value{GDBN}, limitations
13683 Debugging Pascal programs which use sets, subranges, file variables, or
13684 nested functions does not currently work. @value{GDBN} does not support
13685 entering expressions, printing values, or similar features using Pascal
13688 The Pascal-specific command @code{set print pascal_static-members}
13689 controls whether static members of Pascal objects are displayed.
13690 @xref{Print Settings, pascal_static-members}.
13693 @subsection Modula-2
13695 @cindex Modula-2, @value{GDBN} support
13697 The extensions made to @value{GDBN} to support Modula-2 only support
13698 output from the @sc{gnu} Modula-2 compiler (which is currently being
13699 developed). Other Modula-2 compilers are not currently supported, and
13700 attempting to debug executables produced by them is most likely
13701 to give an error as @value{GDBN} reads in the executable's symbol
13704 @cindex expressions in Modula-2
13706 * M2 Operators:: Built-in operators
13707 * Built-In Func/Proc:: Built-in functions and procedures
13708 * M2 Constants:: Modula-2 constants
13709 * M2 Types:: Modula-2 types
13710 * M2 Defaults:: Default settings for Modula-2
13711 * Deviations:: Deviations from standard Modula-2
13712 * M2 Checks:: Modula-2 type and range checks
13713 * M2 Scope:: The scope operators @code{::} and @code{.}
13714 * GDB/M2:: @value{GDBN} and Modula-2
13718 @subsubsection Operators
13719 @cindex Modula-2 operators
13721 Operators must be defined on values of specific types. For instance,
13722 @code{+} is defined on numbers, but not on structures. Operators are
13723 often defined on groups of types. For the purposes of Modula-2, the
13724 following definitions hold:
13729 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13733 @emph{Character types} consist of @code{CHAR} and its subranges.
13736 @emph{Floating-point types} consist of @code{REAL}.
13739 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13743 @emph{Scalar types} consist of all of the above.
13746 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13749 @emph{Boolean types} consist of @code{BOOLEAN}.
13753 The following operators are supported, and appear in order of
13754 increasing precedence:
13758 Function argument or array index separator.
13761 Assignment. The value of @var{var} @code{:=} @var{value} is
13765 Less than, greater than on integral, floating-point, or enumerated
13769 Less than or equal to, greater than or equal to
13770 on integral, floating-point and enumerated types, or set inclusion on
13771 set types. Same precedence as @code{<}.
13773 @item =@r{, }<>@r{, }#
13774 Equality and two ways of expressing inequality, valid on scalar types.
13775 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13776 available for inequality, since @code{#} conflicts with the script
13780 Set membership. Defined on set types and the types of their members.
13781 Same precedence as @code{<}.
13784 Boolean disjunction. Defined on boolean types.
13787 Boolean conjunction. Defined on boolean types.
13790 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13793 Addition and subtraction on integral and floating-point types, or union
13794 and difference on set types.
13797 Multiplication on integral and floating-point types, or set intersection
13801 Division on floating-point types, or symmetric set difference on set
13802 types. Same precedence as @code{*}.
13805 Integer division and remainder. Defined on integral types. Same
13806 precedence as @code{*}.
13809 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13812 Pointer dereferencing. Defined on pointer types.
13815 Boolean negation. Defined on boolean types. Same precedence as
13819 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13820 precedence as @code{^}.
13823 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13826 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13830 @value{GDBN} and Modula-2 scope operators.
13834 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
13835 treats the use of the operator @code{IN}, or the use of operators
13836 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
13837 @code{<=}, and @code{>=} on sets as an error.
13841 @node Built-In Func/Proc
13842 @subsubsection Built-in Functions and Procedures
13843 @cindex Modula-2 built-ins
13845 Modula-2 also makes available several built-in procedures and functions.
13846 In describing these, the following metavariables are used:
13851 represents an @code{ARRAY} variable.
13854 represents a @code{CHAR} constant or variable.
13857 represents a variable or constant of integral type.
13860 represents an identifier that belongs to a set. Generally used in the
13861 same function with the metavariable @var{s}. The type of @var{s} should
13862 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
13865 represents a variable or constant of integral or floating-point type.
13868 represents a variable or constant of floating-point type.
13874 represents a variable.
13877 represents a variable or constant of one of many types. See the
13878 explanation of the function for details.
13881 All Modula-2 built-in procedures also return a result, described below.
13885 Returns the absolute value of @var{n}.
13888 If @var{c} is a lower case letter, it returns its upper case
13889 equivalent, otherwise it returns its argument.
13892 Returns the character whose ordinal value is @var{i}.
13895 Decrements the value in the variable @var{v} by one. Returns the new value.
13897 @item DEC(@var{v},@var{i})
13898 Decrements the value in the variable @var{v} by @var{i}. Returns the
13901 @item EXCL(@var{m},@var{s})
13902 Removes the element @var{m} from the set @var{s}. Returns the new
13905 @item FLOAT(@var{i})
13906 Returns the floating point equivalent of the integer @var{i}.
13908 @item HIGH(@var{a})
13909 Returns the index of the last member of @var{a}.
13912 Increments the value in the variable @var{v} by one. Returns the new value.
13914 @item INC(@var{v},@var{i})
13915 Increments the value in the variable @var{v} by @var{i}. Returns the
13918 @item INCL(@var{m},@var{s})
13919 Adds the element @var{m} to the set @var{s} if it is not already
13920 there. Returns the new set.
13923 Returns the maximum value of the type @var{t}.
13926 Returns the minimum value of the type @var{t}.
13929 Returns boolean TRUE if @var{i} is an odd number.
13932 Returns the ordinal value of its argument. For example, the ordinal
13933 value of a character is its @sc{ascii} value (on machines supporting the
13934 @sc{ascii} character set). @var{x} must be of an ordered type, which include
13935 integral, character and enumerated types.
13937 @item SIZE(@var{x})
13938 Returns the size of its argument. @var{x} can be a variable or a type.
13940 @item TRUNC(@var{r})
13941 Returns the integral part of @var{r}.
13943 @item TSIZE(@var{x})
13944 Returns the size of its argument. @var{x} can be a variable or a type.
13946 @item VAL(@var{t},@var{i})
13947 Returns the member of the type @var{t} whose ordinal value is @var{i}.
13951 @emph{Warning:} Sets and their operations are not yet supported, so
13952 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
13956 @cindex Modula-2 constants
13958 @subsubsection Constants
13960 @value{GDBN} allows you to express the constants of Modula-2 in the following
13966 Integer constants are simply a sequence of digits. When used in an
13967 expression, a constant is interpreted to be type-compatible with the
13968 rest of the expression. Hexadecimal integers are specified by a
13969 trailing @samp{H}, and octal integers by a trailing @samp{B}.
13972 Floating point constants appear as a sequence of digits, followed by a
13973 decimal point and another sequence of digits. An optional exponent can
13974 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
13975 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
13976 digits of the floating point constant must be valid decimal (base 10)
13980 Character constants consist of a single character enclosed by a pair of
13981 like quotes, either single (@code{'}) or double (@code{"}). They may
13982 also be expressed by their ordinal value (their @sc{ascii} value, usually)
13983 followed by a @samp{C}.
13986 String constants consist of a sequence of characters enclosed by a
13987 pair of like quotes, either single (@code{'}) or double (@code{"}).
13988 Escape sequences in the style of C are also allowed. @xref{C
13989 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
13993 Enumerated constants consist of an enumerated identifier.
13996 Boolean constants consist of the identifiers @code{TRUE} and
14000 Pointer constants consist of integral values only.
14003 Set constants are not yet supported.
14007 @subsubsection Modula-2 Types
14008 @cindex Modula-2 types
14010 Currently @value{GDBN} can print the following data types in Modula-2
14011 syntax: array types, record types, set types, pointer types, procedure
14012 types, enumerated types, subrange types and base types. You can also
14013 print the contents of variables declared using these type.
14014 This section gives a number of simple source code examples together with
14015 sample @value{GDBN} sessions.
14017 The first example contains the following section of code:
14026 and you can request @value{GDBN} to interrogate the type and value of
14027 @code{r} and @code{s}.
14030 (@value{GDBP}) print s
14032 (@value{GDBP}) ptype s
14034 (@value{GDBP}) print r
14036 (@value{GDBP}) ptype r
14041 Likewise if your source code declares @code{s} as:
14045 s: SET ['A'..'Z'] ;
14049 then you may query the type of @code{s} by:
14052 (@value{GDBP}) ptype s
14053 type = SET ['A'..'Z']
14057 Note that at present you cannot interactively manipulate set
14058 expressions using the debugger.
14060 The following example shows how you might declare an array in Modula-2
14061 and how you can interact with @value{GDBN} to print its type and contents:
14065 s: ARRAY [-10..10] OF CHAR ;
14069 (@value{GDBP}) ptype s
14070 ARRAY [-10..10] OF CHAR
14073 Note that the array handling is not yet complete and although the type
14074 is printed correctly, expression handling still assumes that all
14075 arrays have a lower bound of zero and not @code{-10} as in the example
14078 Here are some more type related Modula-2 examples:
14082 colour = (blue, red, yellow, green) ;
14083 t = [blue..yellow] ;
14091 The @value{GDBN} interaction shows how you can query the data type
14092 and value of a variable.
14095 (@value{GDBP}) print s
14097 (@value{GDBP}) ptype t
14098 type = [blue..yellow]
14102 In this example a Modula-2 array is declared and its contents
14103 displayed. Observe that the contents are written in the same way as
14104 their @code{C} counterparts.
14108 s: ARRAY [1..5] OF CARDINAL ;
14114 (@value{GDBP}) print s
14115 $1 = @{1, 0, 0, 0, 0@}
14116 (@value{GDBP}) ptype s
14117 type = ARRAY [1..5] OF CARDINAL
14120 The Modula-2 language interface to @value{GDBN} also understands
14121 pointer types as shown in this example:
14125 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14132 and you can request that @value{GDBN} describes the type of @code{s}.
14135 (@value{GDBP}) ptype s
14136 type = POINTER TO ARRAY [1..5] OF CARDINAL
14139 @value{GDBN} handles compound types as we can see in this example.
14140 Here we combine array types, record types, pointer types and subrange
14151 myarray = ARRAY myrange OF CARDINAL ;
14152 myrange = [-2..2] ;
14154 s: POINTER TO ARRAY myrange OF foo ;
14158 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14162 (@value{GDBP}) ptype s
14163 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14166 f3 : ARRAY [-2..2] OF CARDINAL;
14171 @subsubsection Modula-2 Defaults
14172 @cindex Modula-2 defaults
14174 If type and range checking are set automatically by @value{GDBN}, they
14175 both default to @code{on} whenever the working language changes to
14176 Modula-2. This happens regardless of whether you or @value{GDBN}
14177 selected the working language.
14179 If you allow @value{GDBN} to set the language automatically, then entering
14180 code compiled from a file whose name ends with @file{.mod} sets the
14181 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14182 Infer the Source Language}, for further details.
14185 @subsubsection Deviations from Standard Modula-2
14186 @cindex Modula-2, deviations from
14188 A few changes have been made to make Modula-2 programs easier to debug.
14189 This is done primarily via loosening its type strictness:
14193 Unlike in standard Modula-2, pointer constants can be formed by
14194 integers. This allows you to modify pointer variables during
14195 debugging. (In standard Modula-2, the actual address contained in a
14196 pointer variable is hidden from you; it can only be modified
14197 through direct assignment to another pointer variable or expression that
14198 returned a pointer.)
14201 C escape sequences can be used in strings and characters to represent
14202 non-printable characters. @value{GDBN} prints out strings with these
14203 escape sequences embedded. Single non-printable characters are
14204 printed using the @samp{CHR(@var{nnn})} format.
14207 The assignment operator (@code{:=}) returns the value of its right-hand
14211 All built-in procedures both modify @emph{and} return their argument.
14215 @subsubsection Modula-2 Type and Range Checks
14216 @cindex Modula-2 checks
14219 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14222 @c FIXME remove warning when type/range checks added
14224 @value{GDBN} considers two Modula-2 variables type equivalent if:
14228 They are of types that have been declared equivalent via a @code{TYPE
14229 @var{t1} = @var{t2}} statement
14232 They have been declared on the same line. (Note: This is true of the
14233 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14236 As long as type checking is enabled, any attempt to combine variables
14237 whose types are not equivalent is an error.
14239 Range checking is done on all mathematical operations, assignment, array
14240 index bounds, and all built-in functions and procedures.
14243 @subsubsection The Scope Operators @code{::} and @code{.}
14245 @cindex @code{.}, Modula-2 scope operator
14246 @cindex colon, doubled as scope operator
14248 @vindex colon-colon@r{, in Modula-2}
14249 @c Info cannot handle :: but TeX can.
14252 @vindex ::@r{, in Modula-2}
14255 There are a few subtle differences between the Modula-2 scope operator
14256 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14261 @var{module} . @var{id}
14262 @var{scope} :: @var{id}
14266 where @var{scope} is the name of a module or a procedure,
14267 @var{module} the name of a module, and @var{id} is any declared
14268 identifier within your program, except another module.
14270 Using the @code{::} operator makes @value{GDBN} search the scope
14271 specified by @var{scope} for the identifier @var{id}. If it is not
14272 found in the specified scope, then @value{GDBN} searches all scopes
14273 enclosing the one specified by @var{scope}.
14275 Using the @code{.} operator makes @value{GDBN} search the current scope for
14276 the identifier specified by @var{id} that was imported from the
14277 definition module specified by @var{module}. With this operator, it is
14278 an error if the identifier @var{id} was not imported from definition
14279 module @var{module}, or if @var{id} is not an identifier in
14283 @subsubsection @value{GDBN} and Modula-2
14285 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14286 Five subcommands of @code{set print} and @code{show print} apply
14287 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14288 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14289 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14290 analogue in Modula-2.
14292 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14293 with any language, is not useful with Modula-2. Its
14294 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14295 created in Modula-2 as they can in C or C@t{++}. However, because an
14296 address can be specified by an integral constant, the construct
14297 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14299 @cindex @code{#} in Modula-2
14300 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14301 interpreted as the beginning of a comment. Use @code{<>} instead.
14307 The extensions made to @value{GDBN} for Ada only support
14308 output from the @sc{gnu} Ada (GNAT) compiler.
14309 Other Ada compilers are not currently supported, and
14310 attempting to debug executables produced by them is most likely
14314 @cindex expressions in Ada
14316 * Ada Mode Intro:: General remarks on the Ada syntax
14317 and semantics supported by Ada mode
14319 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14320 * Additions to Ada:: Extensions of the Ada expression syntax.
14321 * Stopping Before Main Program:: Debugging the program during elaboration.
14322 * Ada Tasks:: Listing and setting breakpoints in tasks.
14323 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14324 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14326 * Ada Glitches:: Known peculiarities of Ada mode.
14329 @node Ada Mode Intro
14330 @subsubsection Introduction
14331 @cindex Ada mode, general
14333 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14334 syntax, with some extensions.
14335 The philosophy behind the design of this subset is
14339 That @value{GDBN} should provide basic literals and access to operations for
14340 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14341 leaving more sophisticated computations to subprograms written into the
14342 program (which therefore may be called from @value{GDBN}).
14345 That type safety and strict adherence to Ada language restrictions
14346 are not particularly important to the @value{GDBN} user.
14349 That brevity is important to the @value{GDBN} user.
14352 Thus, for brevity, the debugger acts as if all names declared in
14353 user-written packages are directly visible, even if they are not visible
14354 according to Ada rules, thus making it unnecessary to fully qualify most
14355 names with their packages, regardless of context. Where this causes
14356 ambiguity, @value{GDBN} asks the user's intent.
14358 The debugger will start in Ada mode if it detects an Ada main program.
14359 As for other languages, it will enter Ada mode when stopped in a program that
14360 was translated from an Ada source file.
14362 While in Ada mode, you may use `@t{--}' for comments. This is useful
14363 mostly for documenting command files. The standard @value{GDBN} comment
14364 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14365 middle (to allow based literals).
14367 The debugger supports limited overloading. Given a subprogram call in which
14368 the function symbol has multiple definitions, it will use the number of
14369 actual parameters and some information about their types to attempt to narrow
14370 the set of definitions. It also makes very limited use of context, preferring
14371 procedures to functions in the context of the @code{call} command, and
14372 functions to procedures elsewhere.
14374 @node Omissions from Ada
14375 @subsubsection Omissions from Ada
14376 @cindex Ada, omissions from
14378 Here are the notable omissions from the subset:
14382 Only a subset of the attributes are supported:
14386 @t{'First}, @t{'Last}, and @t{'Length}
14387 on array objects (not on types and subtypes).
14390 @t{'Min} and @t{'Max}.
14393 @t{'Pos} and @t{'Val}.
14399 @t{'Range} on array objects (not subtypes), but only as the right
14400 operand of the membership (@code{in}) operator.
14403 @t{'Access}, @t{'Unchecked_Access}, and
14404 @t{'Unrestricted_Access} (a GNAT extension).
14412 @code{Characters.Latin_1} are not available and
14413 concatenation is not implemented. Thus, escape characters in strings are
14414 not currently available.
14417 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14418 equality of representations. They will generally work correctly
14419 for strings and arrays whose elements have integer or enumeration types.
14420 They may not work correctly for arrays whose element
14421 types have user-defined equality, for arrays of real values
14422 (in particular, IEEE-conformant floating point, because of negative
14423 zeroes and NaNs), and for arrays whose elements contain unused bits with
14424 indeterminate values.
14427 The other component-by-component array operations (@code{and}, @code{or},
14428 @code{xor}, @code{not}, and relational tests other than equality)
14429 are not implemented.
14432 @cindex array aggregates (Ada)
14433 @cindex record aggregates (Ada)
14434 @cindex aggregates (Ada)
14435 There is limited support for array and record aggregates. They are
14436 permitted only on the right sides of assignments, as in these examples:
14439 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14440 (@value{GDBP}) set An_Array := (1, others => 0)
14441 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14442 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14443 (@value{GDBP}) set A_Record := (1, "Peter", True);
14444 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14448 discriminant's value by assigning an aggregate has an
14449 undefined effect if that discriminant is used within the record.
14450 However, you can first modify discriminants by directly assigning to
14451 them (which normally would not be allowed in Ada), and then performing an
14452 aggregate assignment. For example, given a variable @code{A_Rec}
14453 declared to have a type such as:
14456 type Rec (Len : Small_Integer := 0) is record
14458 Vals : IntArray (1 .. Len);
14462 you can assign a value with a different size of @code{Vals} with two
14466 (@value{GDBP}) set A_Rec.Len := 4
14467 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14470 As this example also illustrates, @value{GDBN} is very loose about the usual
14471 rules concerning aggregates. You may leave out some of the
14472 components of an array or record aggregate (such as the @code{Len}
14473 component in the assignment to @code{A_Rec} above); they will retain their
14474 original values upon assignment. You may freely use dynamic values as
14475 indices in component associations. You may even use overlapping or
14476 redundant component associations, although which component values are
14477 assigned in such cases is not defined.
14480 Calls to dispatching subprograms are not implemented.
14483 The overloading algorithm is much more limited (i.e., less selective)
14484 than that of real Ada. It makes only limited use of the context in
14485 which a subexpression appears to resolve its meaning, and it is much
14486 looser in its rules for allowing type matches. As a result, some
14487 function calls will be ambiguous, and the user will be asked to choose
14488 the proper resolution.
14491 The @code{new} operator is not implemented.
14494 Entry calls are not implemented.
14497 Aside from printing, arithmetic operations on the native VAX floating-point
14498 formats are not supported.
14501 It is not possible to slice a packed array.
14504 The names @code{True} and @code{False}, when not part of a qualified name,
14505 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14507 Should your program
14508 redefine these names in a package or procedure (at best a dubious practice),
14509 you will have to use fully qualified names to access their new definitions.
14512 @node Additions to Ada
14513 @subsubsection Additions to Ada
14514 @cindex Ada, deviations from
14516 As it does for other languages, @value{GDBN} makes certain generic
14517 extensions to Ada (@pxref{Expressions}):
14521 If the expression @var{E} is a variable residing in memory (typically
14522 a local variable or array element) and @var{N} is a positive integer,
14523 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14524 @var{N}-1 adjacent variables following it in memory as an array. In
14525 Ada, this operator is generally not necessary, since its prime use is
14526 in displaying parts of an array, and slicing will usually do this in
14527 Ada. However, there are occasional uses when debugging programs in
14528 which certain debugging information has been optimized away.
14531 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14532 appears in function or file @var{B}.'' When @var{B} is a file name,
14533 you must typically surround it in single quotes.
14536 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14537 @var{type} that appears at address @var{addr}.''
14540 A name starting with @samp{$} is a convenience variable
14541 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14544 In addition, @value{GDBN} provides a few other shortcuts and outright
14545 additions specific to Ada:
14549 The assignment statement is allowed as an expression, returning
14550 its right-hand operand as its value. Thus, you may enter
14553 (@value{GDBP}) set x := y + 3
14554 (@value{GDBP}) print A(tmp := y + 1)
14558 The semicolon is allowed as an ``operator,'' returning as its value
14559 the value of its right-hand operand.
14560 This allows, for example,
14561 complex conditional breaks:
14564 (@value{GDBP}) break f
14565 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14569 Rather than use catenation and symbolic character names to introduce special
14570 characters into strings, one may instead use a special bracket notation,
14571 which is also used to print strings. A sequence of characters of the form
14572 @samp{["@var{XX}"]} within a string or character literal denotes the
14573 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14574 sequence of characters @samp{["""]} also denotes a single quotation mark
14575 in strings. For example,
14577 "One line.["0a"]Next line.["0a"]"
14580 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14584 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14585 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14589 (@value{GDBP}) print 'max(x, y)
14593 When printing arrays, @value{GDBN} uses positional notation when the
14594 array has a lower bound of 1, and uses a modified named notation otherwise.
14595 For example, a one-dimensional array of three integers with a lower bound
14596 of 3 might print as
14603 That is, in contrast to valid Ada, only the first component has a @code{=>}
14607 You may abbreviate attributes in expressions with any unique,
14608 multi-character subsequence of
14609 their names (an exact match gets preference).
14610 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14611 in place of @t{a'length}.
14614 @cindex quoting Ada internal identifiers
14615 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14616 to lower case. The GNAT compiler uses upper-case characters for
14617 some of its internal identifiers, which are normally of no interest to users.
14618 For the rare occasions when you actually have to look at them,
14619 enclose them in angle brackets to avoid the lower-case mapping.
14622 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14626 Printing an object of class-wide type or dereferencing an
14627 access-to-class-wide value will display all the components of the object's
14628 specific type (as indicated by its run-time tag). Likewise, component
14629 selection on such a value will operate on the specific type of the
14634 @node Stopping Before Main Program
14635 @subsubsection Stopping at the Very Beginning
14637 @cindex breakpointing Ada elaboration code
14638 It is sometimes necessary to debug the program during elaboration, and
14639 before reaching the main procedure.
14640 As defined in the Ada Reference
14641 Manual, the elaboration code is invoked from a procedure called
14642 @code{adainit}. To run your program up to the beginning of
14643 elaboration, simply use the following two commands:
14644 @code{tbreak adainit} and @code{run}.
14647 @subsubsection Extensions for Ada Tasks
14648 @cindex Ada, tasking
14650 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14651 @value{GDBN} provides the following task-related commands:
14656 This command shows a list of current Ada tasks, as in the following example:
14663 (@value{GDBP}) info tasks
14664 ID TID P-ID Pri State Name
14665 1 8088000 0 15 Child Activation Wait main_task
14666 2 80a4000 1 15 Accept Statement b
14667 3 809a800 1 15 Child Activation Wait a
14668 * 4 80ae800 3 15 Runnable c
14673 In this listing, the asterisk before the last task indicates it to be the
14674 task currently being inspected.
14678 Represents @value{GDBN}'s internal task number.
14684 The parent's task ID (@value{GDBN}'s internal task number).
14687 The base priority of the task.
14690 Current state of the task.
14694 The task has been created but has not been activated. It cannot be
14698 The task is not blocked for any reason known to Ada. (It may be waiting
14699 for a mutex, though.) It is conceptually "executing" in normal mode.
14702 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14703 that were waiting on terminate alternatives have been awakened and have
14704 terminated themselves.
14706 @item Child Activation Wait
14707 The task is waiting for created tasks to complete activation.
14709 @item Accept Statement
14710 The task is waiting on an accept or selective wait statement.
14712 @item Waiting on entry call
14713 The task is waiting on an entry call.
14715 @item Async Select Wait
14716 The task is waiting to start the abortable part of an asynchronous
14720 The task is waiting on a select statement with only a delay
14723 @item Child Termination Wait
14724 The task is sleeping having completed a master within itself, and is
14725 waiting for the tasks dependent on that master to become terminated or
14726 waiting on a terminate Phase.
14728 @item Wait Child in Term Alt
14729 The task is sleeping waiting for tasks on terminate alternatives to
14730 finish terminating.
14732 @item Accepting RV with @var{taskno}
14733 The task is accepting a rendez-vous with the task @var{taskno}.
14737 Name of the task in the program.
14741 @kindex info task @var{taskno}
14742 @item info task @var{taskno}
14743 This command shows detailled informations on the specified task, as in
14744 the following example:
14749 (@value{GDBP}) info tasks
14750 ID TID P-ID Pri State Name
14751 1 8077880 0 15 Child Activation Wait main_task
14752 * 2 807c468 1 15 Runnable task_1
14753 (@value{GDBP}) info task 2
14754 Ada Task: 0x807c468
14757 Parent: 1 (main_task)
14763 @kindex task@r{ (Ada)}
14764 @cindex current Ada task ID
14765 This command prints the ID of the current task.
14771 (@value{GDBP}) info tasks
14772 ID TID P-ID Pri State Name
14773 1 8077870 0 15 Child Activation Wait main_task
14774 * 2 807c458 1 15 Runnable t
14775 (@value{GDBP}) task
14776 [Current task is 2]
14779 @item task @var{taskno}
14780 @cindex Ada task switching
14781 This command is like the @code{thread @var{threadno}}
14782 command (@pxref{Threads}). It switches the context of debugging
14783 from the current task to the given task.
14789 (@value{GDBP}) info tasks
14790 ID TID P-ID Pri State Name
14791 1 8077870 0 15 Child Activation Wait main_task
14792 * 2 807c458 1 15 Runnable t
14793 (@value{GDBP}) task 1
14794 [Switching to task 1]
14795 #0 0x8067726 in pthread_cond_wait ()
14797 #0 0x8067726 in pthread_cond_wait ()
14798 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14799 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14800 #3 0x806153e in system.tasking.stages.activate_tasks ()
14801 #4 0x804aacc in un () at un.adb:5
14804 @item break @var{linespec} task @var{taskno}
14805 @itemx break @var{linespec} task @var{taskno} if @dots{}
14806 @cindex breakpoints and tasks, in Ada
14807 @cindex task breakpoints, in Ada
14808 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14809 These commands are like the @code{break @dots{} thread @dots{}}
14810 command (@pxref{Thread Stops}).
14811 @var{linespec} specifies source lines, as described
14812 in @ref{Specify Location}.
14814 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14815 to specify that you only want @value{GDBN} to stop the program when a
14816 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14817 numeric task identifiers assigned by @value{GDBN}, shown in the first
14818 column of the @samp{info tasks} display.
14820 If you do not specify @samp{task @var{taskno}} when you set a
14821 breakpoint, the breakpoint applies to @emph{all} tasks of your
14824 You can use the @code{task} qualifier on conditional breakpoints as
14825 well; in this case, place @samp{task @var{taskno}} before the
14826 breakpoint condition (before the @code{if}).
14834 (@value{GDBP}) info tasks
14835 ID TID P-ID Pri State Name
14836 1 140022020 0 15 Child Activation Wait main_task
14837 2 140045060 1 15 Accept/Select Wait t2
14838 3 140044840 1 15 Runnable t1
14839 * 4 140056040 1 15 Runnable t3
14840 (@value{GDBP}) b 15 task 2
14841 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
14842 (@value{GDBP}) cont
14847 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
14849 (@value{GDBP}) info tasks
14850 ID TID P-ID Pri State Name
14851 1 140022020 0 15 Child Activation Wait main_task
14852 * 2 140045060 1 15 Runnable t2
14853 3 140044840 1 15 Runnable t1
14854 4 140056040 1 15 Delay Sleep t3
14858 @node Ada Tasks and Core Files
14859 @subsubsection Tasking Support when Debugging Core Files
14860 @cindex Ada tasking and core file debugging
14862 When inspecting a core file, as opposed to debugging a live program,
14863 tasking support may be limited or even unavailable, depending on
14864 the platform being used.
14865 For instance, on x86-linux, the list of tasks is available, but task
14866 switching is not supported. On Tru64, however, task switching will work
14869 On certain platforms, including Tru64, the debugger needs to perform some
14870 memory writes in order to provide Ada tasking support. When inspecting
14871 a core file, this means that the core file must be opened with read-write
14872 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
14873 Under these circumstances, you should make a backup copy of the core
14874 file before inspecting it with @value{GDBN}.
14876 @node Ravenscar Profile
14877 @subsubsection Tasking Support when using the Ravenscar Profile
14878 @cindex Ravenscar Profile
14880 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
14881 specifically designed for systems with safety-critical real-time
14885 @kindex set ravenscar task-switching on
14886 @cindex task switching with program using Ravenscar Profile
14887 @item set ravenscar task-switching on
14888 Allows task switching when debugging a program that uses the Ravenscar
14889 Profile. This is the default.
14891 @kindex set ravenscar task-switching off
14892 @item set ravenscar task-switching off
14893 Turn off task switching when debugging a program that uses the Ravenscar
14894 Profile. This is mostly intended to disable the code that adds support
14895 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
14896 the Ravenscar runtime is preventing @value{GDBN} from working properly.
14897 To be effective, this command should be run before the program is started.
14899 @kindex show ravenscar task-switching
14900 @item show ravenscar task-switching
14901 Show whether it is possible to switch from task to task in a program
14902 using the Ravenscar Profile.
14907 @subsubsection Known Peculiarities of Ada Mode
14908 @cindex Ada, problems
14910 Besides the omissions listed previously (@pxref{Omissions from Ada}),
14911 we know of several problems with and limitations of Ada mode in
14913 some of which will be fixed with planned future releases of the debugger
14914 and the GNU Ada compiler.
14918 Static constants that the compiler chooses not to materialize as objects in
14919 storage are invisible to the debugger.
14922 Named parameter associations in function argument lists are ignored (the
14923 argument lists are treated as positional).
14926 Many useful library packages are currently invisible to the debugger.
14929 Fixed-point arithmetic, conversions, input, and output is carried out using
14930 floating-point arithmetic, and may give results that only approximate those on
14934 The GNAT compiler never generates the prefix @code{Standard} for any of
14935 the standard symbols defined by the Ada language. @value{GDBN} knows about
14936 this: it will strip the prefix from names when you use it, and will never
14937 look for a name you have so qualified among local symbols, nor match against
14938 symbols in other packages or subprograms. If you have
14939 defined entities anywhere in your program other than parameters and
14940 local variables whose simple names match names in @code{Standard},
14941 GNAT's lack of qualification here can cause confusion. When this happens,
14942 you can usually resolve the confusion
14943 by qualifying the problematic names with package
14944 @code{Standard} explicitly.
14947 Older versions of the compiler sometimes generate erroneous debugging
14948 information, resulting in the debugger incorrectly printing the value
14949 of affected entities. In some cases, the debugger is able to work
14950 around an issue automatically. In other cases, the debugger is able
14951 to work around the issue, but the work-around has to be specifically
14954 @kindex set ada trust-PAD-over-XVS
14955 @kindex show ada trust-PAD-over-XVS
14958 @item set ada trust-PAD-over-XVS on
14959 Configure GDB to strictly follow the GNAT encoding when computing the
14960 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
14961 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
14962 a complete description of the encoding used by the GNAT compiler).
14963 This is the default.
14965 @item set ada trust-PAD-over-XVS off
14966 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
14967 sometimes prints the wrong value for certain entities, changing @code{ada
14968 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
14969 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
14970 @code{off}, but this incurs a slight performance penalty, so it is
14971 recommended to leave this setting to @code{on} unless necessary.
14975 @node Unsupported Languages
14976 @section Unsupported Languages
14978 @cindex unsupported languages
14979 @cindex minimal language
14980 In addition to the other fully-supported programming languages,
14981 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
14982 It does not represent a real programming language, but provides a set
14983 of capabilities close to what the C or assembly languages provide.
14984 This should allow most simple operations to be performed while debugging
14985 an application that uses a language currently not supported by @value{GDBN}.
14987 If the language is set to @code{auto}, @value{GDBN} will automatically
14988 select this language if the current frame corresponds to an unsupported
14992 @chapter Examining the Symbol Table
14994 The commands described in this chapter allow you to inquire about the
14995 symbols (names of variables, functions and types) defined in your
14996 program. This information is inherent in the text of your program and
14997 does not change as your program executes. @value{GDBN} finds it in your
14998 program's symbol table, in the file indicated when you started @value{GDBN}
14999 (@pxref{File Options, ,Choosing Files}), or by one of the
15000 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15002 @cindex symbol names
15003 @cindex names of symbols
15004 @cindex quoting names
15005 Occasionally, you may need to refer to symbols that contain unusual
15006 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15007 most frequent case is in referring to static variables in other
15008 source files (@pxref{Variables,,Program Variables}). File names
15009 are recorded in object files as debugging symbols, but @value{GDBN} would
15010 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15011 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15012 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15019 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15022 @cindex case-insensitive symbol names
15023 @cindex case sensitivity in symbol names
15024 @kindex set case-sensitive
15025 @item set case-sensitive on
15026 @itemx set case-sensitive off
15027 @itemx set case-sensitive auto
15028 Normally, when @value{GDBN} looks up symbols, it matches their names
15029 with case sensitivity determined by the current source language.
15030 Occasionally, you may wish to control that. The command @code{set
15031 case-sensitive} lets you do that by specifying @code{on} for
15032 case-sensitive matches or @code{off} for case-insensitive ones. If
15033 you specify @code{auto}, case sensitivity is reset to the default
15034 suitable for the source language. The default is case-sensitive
15035 matches for all languages except for Fortran, for which the default is
15036 case-insensitive matches.
15038 @kindex show case-sensitive
15039 @item show case-sensitive
15040 This command shows the current setting of case sensitivity for symbols
15043 @kindex set print type methods
15044 @item set print type methods
15045 @itemx set print type methods on
15046 @itemx set print type methods off
15047 Normally, when @value{GDBN} prints a class, it displays any methods
15048 declared in that class. You can control this behavior either by
15049 passing the appropriate flag to @code{ptype}, or using @command{set
15050 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15051 display the methods; this is the default. Specifying @code{off} will
15052 cause @value{GDBN} to omit the methods.
15054 @kindex show print type methods
15055 @item show print type methods
15056 This command shows the current setting of method display when printing
15059 @kindex set print type typedefs
15060 @item set print type typedefs
15061 @itemx set print type typedefs on
15062 @itemx set print type typedefs off
15064 Normally, when @value{GDBN} prints a class, it displays any typedefs
15065 defined in that class. You can control this behavior either by
15066 passing the appropriate flag to @code{ptype}, or using @command{set
15067 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15068 display the typedef definitions; this is the default. Specifying
15069 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15070 Note that this controls whether the typedef definition itself is
15071 printed, not whether typedef names are substituted when printing other
15074 @kindex show print type typedefs
15075 @item show print type typedefs
15076 This command shows the current setting of typedef display when
15079 @kindex info address
15080 @cindex address of a symbol
15081 @item info address @var{symbol}
15082 Describe where the data for @var{symbol} is stored. For a register
15083 variable, this says which register it is kept in. For a non-register
15084 local variable, this prints the stack-frame offset at which the variable
15087 Note the contrast with @samp{print &@var{symbol}}, which does not work
15088 at all for a register variable, and for a stack local variable prints
15089 the exact address of the current instantiation of the variable.
15091 @kindex info symbol
15092 @cindex symbol from address
15093 @cindex closest symbol and offset for an address
15094 @item info symbol @var{addr}
15095 Print the name of a symbol which is stored at the address @var{addr}.
15096 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15097 nearest symbol and an offset from it:
15100 (@value{GDBP}) info symbol 0x54320
15101 _initialize_vx + 396 in section .text
15105 This is the opposite of the @code{info address} command. You can use
15106 it to find out the name of a variable or a function given its address.
15108 For dynamically linked executables, the name of executable or shared
15109 library containing the symbol is also printed:
15112 (@value{GDBP}) info symbol 0x400225
15113 _start + 5 in section .text of /tmp/a.out
15114 (@value{GDBP}) info symbol 0x2aaaac2811cf
15115 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15119 @item whatis[/@var{flags}] [@var{arg}]
15120 Print the data type of @var{arg}, which can be either an expression
15121 or a name of a data type. With no argument, print the data type of
15122 @code{$}, the last value in the value history.
15124 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15125 is not actually evaluated, and any side-effecting operations (such as
15126 assignments or function calls) inside it do not take place.
15128 If @var{arg} is a variable or an expression, @code{whatis} prints its
15129 literal type as it is used in the source code. If the type was
15130 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15131 the data type underlying the @code{typedef}. If the type of the
15132 variable or the expression is a compound data type, such as
15133 @code{struct} or @code{class}, @code{whatis} never prints their
15134 fields or methods. It just prints the @code{struct}/@code{class}
15135 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15136 such a compound data type, use @code{ptype}.
15138 If @var{arg} is a type name that was defined using @code{typedef},
15139 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15140 Unrolling means that @code{whatis} will show the underlying type used
15141 in the @code{typedef} declaration of @var{arg}. However, if that
15142 underlying type is also a @code{typedef}, @code{whatis} will not
15145 For C code, the type names may also have the form @samp{class
15146 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15147 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15149 @var{flags} can be used to modify how the type is displayed.
15150 Available flags are:
15154 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15155 parameters and typedefs defined in a class when printing the class'
15156 members. The @code{/r} flag disables this.
15159 Do not print methods defined in the class.
15162 Print methods defined in the class. This is the default, but the flag
15163 exists in case you change the default with @command{set print type methods}.
15166 Do not print typedefs defined in the class. Note that this controls
15167 whether the typedef definition itself is printed, not whether typedef
15168 names are substituted when printing other types.
15171 Print typedefs defined in the class. This is the default, but the flag
15172 exists in case you change the default with @command{set print type typedefs}.
15176 @item ptype[/@var{flags}] [@var{arg}]
15177 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15178 detailed description of the type, instead of just the name of the type.
15179 @xref{Expressions, ,Expressions}.
15181 Contrary to @code{whatis}, @code{ptype} always unrolls any
15182 @code{typedef}s in its argument declaration, whether the argument is
15183 a variable, expression, or a data type. This means that @code{ptype}
15184 of a variable or an expression will not print literally its type as
15185 present in the source code---use @code{whatis} for that. @code{typedef}s at
15186 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15187 fields, methods and inner @code{class typedef}s of @code{struct}s,
15188 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15190 For example, for this variable declaration:
15193 typedef double real_t;
15194 struct complex @{ real_t real; double imag; @};
15195 typedef struct complex complex_t;
15197 real_t *real_pointer_var;
15201 the two commands give this output:
15205 (@value{GDBP}) whatis var
15207 (@value{GDBP}) ptype var
15208 type = struct complex @{
15212 (@value{GDBP}) whatis complex_t
15213 type = struct complex
15214 (@value{GDBP}) whatis struct complex
15215 type = struct complex
15216 (@value{GDBP}) ptype struct complex
15217 type = struct complex @{
15221 (@value{GDBP}) whatis real_pointer_var
15223 (@value{GDBP}) ptype real_pointer_var
15229 As with @code{whatis}, using @code{ptype} without an argument refers to
15230 the type of @code{$}, the last value in the value history.
15232 @cindex incomplete type
15233 Sometimes, programs use opaque data types or incomplete specifications
15234 of complex data structure. If the debug information included in the
15235 program does not allow @value{GDBN} to display a full declaration of
15236 the data type, it will say @samp{<incomplete type>}. For example,
15237 given these declarations:
15241 struct foo *fooptr;
15245 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15248 (@value{GDBP}) ptype foo
15249 $1 = <incomplete type>
15253 ``Incomplete type'' is C terminology for data types that are not
15254 completely specified.
15257 @item info types @var{regexp}
15259 Print a brief description of all types whose names match the regular
15260 expression @var{regexp} (or all types in your program, if you supply
15261 no argument). Each complete typename is matched as though it were a
15262 complete line; thus, @samp{i type value} gives information on all
15263 types in your program whose names include the string @code{value}, but
15264 @samp{i type ^value$} gives information only on types whose complete
15265 name is @code{value}.
15267 This command differs from @code{ptype} in two ways: first, like
15268 @code{whatis}, it does not print a detailed description; second, it
15269 lists all source files where a type is defined.
15271 @kindex info type-printers
15272 @item info type-printers
15273 Versions of @value{GDBN} that ship with Python scripting enabled may
15274 have ``type printers'' available. When using @command{ptype} or
15275 @command{whatis}, these printers are consulted when the name of a type
15276 is needed. @xref{Type Printing API}, for more information on writing
15279 @code{info type-printers} displays all the available type printers.
15281 @kindex enable type-printer
15282 @kindex disable type-printer
15283 @item enable type-printer @var{name}@dots{}
15284 @item disable type-printer @var{name}@dots{}
15285 These commands can be used to enable or disable type printers.
15288 @cindex local variables
15289 @item info scope @var{location}
15290 List all the variables local to a particular scope. This command
15291 accepts a @var{location} argument---a function name, a source line, or
15292 an address preceded by a @samp{*}, and prints all the variables local
15293 to the scope defined by that location. (@xref{Specify Location}, for
15294 details about supported forms of @var{location}.) For example:
15297 (@value{GDBP}) @b{info scope command_line_handler}
15298 Scope for command_line_handler:
15299 Symbol rl is an argument at stack/frame offset 8, length 4.
15300 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15301 Symbol linelength is in static storage at address 0x150a1c, length 4.
15302 Symbol p is a local variable in register $esi, length 4.
15303 Symbol p1 is a local variable in register $ebx, length 4.
15304 Symbol nline is a local variable in register $edx, length 4.
15305 Symbol repeat is a local variable at frame offset -8, length 4.
15309 This command is especially useful for determining what data to collect
15310 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15313 @kindex info source
15315 Show information about the current source file---that is, the source file for
15316 the function containing the current point of execution:
15319 the name of the source file, and the directory containing it,
15321 the directory it was compiled in,
15323 its length, in lines,
15325 which programming language it is written in,
15327 whether the executable includes debugging information for that file, and
15328 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15330 whether the debugging information includes information about
15331 preprocessor macros.
15335 @kindex info sources
15337 Print the names of all source files in your program for which there is
15338 debugging information, organized into two lists: files whose symbols
15339 have already been read, and files whose symbols will be read when needed.
15341 @kindex info functions
15342 @item info functions
15343 Print the names and data types of all defined functions.
15345 @item info functions @var{regexp}
15346 Print the names and data types of all defined functions
15347 whose names contain a match for regular expression @var{regexp}.
15348 Thus, @samp{info fun step} finds all functions whose names
15349 include @code{step}; @samp{info fun ^step} finds those whose names
15350 start with @code{step}. If a function name contains characters
15351 that conflict with the regular expression language (e.g.@:
15352 @samp{operator*()}), they may be quoted with a backslash.
15354 @kindex info variables
15355 @item info variables
15356 Print the names and data types of all variables that are defined
15357 outside of functions (i.e.@: excluding local variables).
15359 @item info variables @var{regexp}
15360 Print the names and data types of all variables (except for local
15361 variables) whose names contain a match for regular expression
15364 @kindex info classes
15365 @cindex Objective-C, classes and selectors
15367 @itemx info classes @var{regexp}
15368 Display all Objective-C classes in your program, or
15369 (with the @var{regexp} argument) all those matching a particular regular
15372 @kindex info selectors
15373 @item info selectors
15374 @itemx info selectors @var{regexp}
15375 Display all Objective-C selectors in your program, or
15376 (with the @var{regexp} argument) all those matching a particular regular
15380 This was never implemented.
15381 @kindex info methods
15383 @itemx info methods @var{regexp}
15384 The @code{info methods} command permits the user to examine all defined
15385 methods within C@t{++} program, or (with the @var{regexp} argument) a
15386 specific set of methods found in the various C@t{++} classes. Many
15387 C@t{++} classes provide a large number of methods. Thus, the output
15388 from the @code{ptype} command can be overwhelming and hard to use. The
15389 @code{info-methods} command filters the methods, printing only those
15390 which match the regular-expression @var{regexp}.
15393 @cindex opaque data types
15394 @kindex set opaque-type-resolution
15395 @item set opaque-type-resolution on
15396 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15397 declared as a pointer to a @code{struct}, @code{class}, or
15398 @code{union}---for example, @code{struct MyType *}---that is used in one
15399 source file although the full declaration of @code{struct MyType} is in
15400 another source file. The default is on.
15402 A change in the setting of this subcommand will not take effect until
15403 the next time symbols for a file are loaded.
15405 @item set opaque-type-resolution off
15406 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15407 is printed as follows:
15409 @{<no data fields>@}
15412 @kindex show opaque-type-resolution
15413 @item show opaque-type-resolution
15414 Show whether opaque types are resolved or not.
15416 @kindex maint print symbols
15417 @cindex symbol dump
15418 @kindex maint print psymbols
15419 @cindex partial symbol dump
15420 @item maint print symbols @var{filename}
15421 @itemx maint print psymbols @var{filename}
15422 @itemx maint print msymbols @var{filename}
15423 Write a dump of debugging symbol data into the file @var{filename}.
15424 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15425 symbols with debugging data are included. If you use @samp{maint print
15426 symbols}, @value{GDBN} includes all the symbols for which it has already
15427 collected full details: that is, @var{filename} reflects symbols for
15428 only those files whose symbols @value{GDBN} has read. You can use the
15429 command @code{info sources} to find out which files these are. If you
15430 use @samp{maint print psymbols} instead, the dump shows information about
15431 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15432 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15433 @samp{maint print msymbols} dumps just the minimal symbol information
15434 required for each object file from which @value{GDBN} has read some symbols.
15435 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15436 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15438 @kindex maint info symtabs
15439 @kindex maint info psymtabs
15440 @cindex listing @value{GDBN}'s internal symbol tables
15441 @cindex symbol tables, listing @value{GDBN}'s internal
15442 @cindex full symbol tables, listing @value{GDBN}'s internal
15443 @cindex partial symbol tables, listing @value{GDBN}'s internal
15444 @item maint info symtabs @r{[} @var{regexp} @r{]}
15445 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15447 List the @code{struct symtab} or @code{struct partial_symtab}
15448 structures whose names match @var{regexp}. If @var{regexp} is not
15449 given, list them all. The output includes expressions which you can
15450 copy into a @value{GDBN} debugging this one to examine a particular
15451 structure in more detail. For example:
15454 (@value{GDBP}) maint info psymtabs dwarf2read
15455 @{ objfile /home/gnu/build/gdb/gdb
15456 ((struct objfile *) 0x82e69d0)
15457 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15458 ((struct partial_symtab *) 0x8474b10)
15461 text addresses 0x814d3c8 -- 0x8158074
15462 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15463 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15464 dependencies (none)
15467 (@value{GDBP}) maint info symtabs
15471 We see that there is one partial symbol table whose filename contains
15472 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15473 and we see that @value{GDBN} has not read in any symtabs yet at all.
15474 If we set a breakpoint on a function, that will cause @value{GDBN} to
15475 read the symtab for the compilation unit containing that function:
15478 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15479 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15481 (@value{GDBP}) maint info symtabs
15482 @{ objfile /home/gnu/build/gdb/gdb
15483 ((struct objfile *) 0x82e69d0)
15484 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15485 ((struct symtab *) 0x86c1f38)
15488 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15489 linetable ((struct linetable *) 0x8370fa0)
15490 debugformat DWARF 2
15499 @chapter Altering Execution
15501 Once you think you have found an error in your program, you might want to
15502 find out for certain whether correcting the apparent error would lead to
15503 correct results in the rest of the run. You can find the answer by
15504 experiment, using the @value{GDBN} features for altering execution of the
15507 For example, you can store new values into variables or memory
15508 locations, give your program a signal, restart it at a different
15509 address, or even return prematurely from a function.
15512 * Assignment:: Assignment to variables
15513 * Jumping:: Continuing at a different address
15514 * Signaling:: Giving your program a signal
15515 * Returning:: Returning from a function
15516 * Calling:: Calling your program's functions
15517 * Patching:: Patching your program
15521 @section Assignment to Variables
15524 @cindex setting variables
15525 To alter the value of a variable, evaluate an assignment expression.
15526 @xref{Expressions, ,Expressions}. For example,
15533 stores the value 4 into the variable @code{x}, and then prints the
15534 value of the assignment expression (which is 4).
15535 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15536 information on operators in supported languages.
15538 @kindex set variable
15539 @cindex variables, setting
15540 If you are not interested in seeing the value of the assignment, use the
15541 @code{set} command instead of the @code{print} command. @code{set} is
15542 really the same as @code{print} except that the expression's value is
15543 not printed and is not put in the value history (@pxref{Value History,
15544 ,Value History}). The expression is evaluated only for its effects.
15546 If the beginning of the argument string of the @code{set} command
15547 appears identical to a @code{set} subcommand, use the @code{set
15548 variable} command instead of just @code{set}. This command is identical
15549 to @code{set} except for its lack of subcommands. For example, if your
15550 program has a variable @code{width}, you get an error if you try to set
15551 a new value with just @samp{set width=13}, because @value{GDBN} has the
15552 command @code{set width}:
15555 (@value{GDBP}) whatis width
15557 (@value{GDBP}) p width
15559 (@value{GDBP}) set width=47
15560 Invalid syntax in expression.
15564 The invalid expression, of course, is @samp{=47}. In
15565 order to actually set the program's variable @code{width}, use
15568 (@value{GDBP}) set var width=47
15571 Because the @code{set} command has many subcommands that can conflict
15572 with the names of program variables, it is a good idea to use the
15573 @code{set variable} command instead of just @code{set}. For example, if
15574 your program has a variable @code{g}, you run into problems if you try
15575 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15576 the command @code{set gnutarget}, abbreviated @code{set g}:
15580 (@value{GDBP}) whatis g
15584 (@value{GDBP}) set g=4
15588 The program being debugged has been started already.
15589 Start it from the beginning? (y or n) y
15590 Starting program: /home/smith/cc_progs/a.out
15591 "/home/smith/cc_progs/a.out": can't open to read symbols:
15592 Invalid bfd target.
15593 (@value{GDBP}) show g
15594 The current BFD target is "=4".
15599 The program variable @code{g} did not change, and you silently set the
15600 @code{gnutarget} to an invalid value. In order to set the variable
15604 (@value{GDBP}) set var g=4
15607 @value{GDBN} allows more implicit conversions in assignments than C; you can
15608 freely store an integer value into a pointer variable or vice versa,
15609 and you can convert any structure to any other structure that is the
15610 same length or shorter.
15611 @comment FIXME: how do structs align/pad in these conversions?
15612 @comment /doc@cygnus.com 18dec1990
15614 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15615 construct to generate a value of specified type at a specified address
15616 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15617 to memory location @code{0x83040} as an integer (which implies a certain size
15618 and representation in memory), and
15621 set @{int@}0x83040 = 4
15625 stores the value 4 into that memory location.
15628 @section Continuing at a Different Address
15630 Ordinarily, when you continue your program, you do so at the place where
15631 it stopped, with the @code{continue} command. You can instead continue at
15632 an address of your own choosing, with the following commands:
15636 @kindex j @r{(@code{jump})}
15637 @item jump @var{linespec}
15638 @itemx j @var{linespec}
15639 @itemx jump @var{location}
15640 @itemx j @var{location}
15641 Resume execution at line @var{linespec} or at address given by
15642 @var{location}. Execution stops again immediately if there is a
15643 breakpoint there. @xref{Specify Location}, for a description of the
15644 different forms of @var{linespec} and @var{location}. It is common
15645 practice to use the @code{tbreak} command in conjunction with
15646 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15648 The @code{jump} command does not change the current stack frame, or
15649 the stack pointer, or the contents of any memory location or any
15650 register other than the program counter. If line @var{linespec} is in
15651 a different function from the one currently executing, the results may
15652 be bizarre if the two functions expect different patterns of arguments or
15653 of local variables. For this reason, the @code{jump} command requests
15654 confirmation if the specified line is not in the function currently
15655 executing. However, even bizarre results are predictable if you are
15656 well acquainted with the machine-language code of your program.
15659 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15660 On many systems, you can get much the same effect as the @code{jump}
15661 command by storing a new value into the register @code{$pc}. The
15662 difference is that this does not start your program running; it only
15663 changes the address of where it @emph{will} run when you continue. For
15671 makes the next @code{continue} command or stepping command execute at
15672 address @code{0x485}, rather than at the address where your program stopped.
15673 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15675 The most common occasion to use the @code{jump} command is to back
15676 up---perhaps with more breakpoints set---over a portion of a program
15677 that has already executed, in order to examine its execution in more
15682 @section Giving your Program a Signal
15683 @cindex deliver a signal to a program
15687 @item signal @var{signal}
15688 Resume execution where your program stopped, but immediately give it the
15689 signal @var{signal}. @var{signal} can be the name or the number of a
15690 signal. For example, on many systems @code{signal 2} and @code{signal
15691 SIGINT} are both ways of sending an interrupt signal.
15693 Alternatively, if @var{signal} is zero, continue execution without
15694 giving a signal. This is useful when your program stopped on account of
15695 a signal and would ordinarily see the signal when resumed with the
15696 @code{continue} command; @samp{signal 0} causes it to resume without a
15699 @code{signal} does not repeat when you press @key{RET} a second time
15700 after executing the command.
15704 Invoking the @code{signal} command is not the same as invoking the
15705 @code{kill} utility from the shell. Sending a signal with @code{kill}
15706 causes @value{GDBN} to decide what to do with the signal depending on
15707 the signal handling tables (@pxref{Signals}). The @code{signal} command
15708 passes the signal directly to your program.
15712 @section Returning from a Function
15715 @cindex returning from a function
15718 @itemx return @var{expression}
15719 You can cancel execution of a function call with the @code{return}
15720 command. If you give an
15721 @var{expression} argument, its value is used as the function's return
15725 When you use @code{return}, @value{GDBN} discards the selected stack frame
15726 (and all frames within it). You can think of this as making the
15727 discarded frame return prematurely. If you wish to specify a value to
15728 be returned, give that value as the argument to @code{return}.
15730 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15731 Frame}), and any other frames inside of it, leaving its caller as the
15732 innermost remaining frame. That frame becomes selected. The
15733 specified value is stored in the registers used for returning values
15736 The @code{return} command does not resume execution; it leaves the
15737 program stopped in the state that would exist if the function had just
15738 returned. In contrast, the @code{finish} command (@pxref{Continuing
15739 and Stepping, ,Continuing and Stepping}) resumes execution until the
15740 selected stack frame returns naturally.
15742 @value{GDBN} needs to know how the @var{expression} argument should be set for
15743 the inferior. The concrete registers assignment depends on the OS ABI and the
15744 type being returned by the selected stack frame. For example it is common for
15745 OS ABI to return floating point values in FPU registers while integer values in
15746 CPU registers. Still some ABIs return even floating point values in CPU
15747 registers. Larger integer widths (such as @code{long long int}) also have
15748 specific placement rules. @value{GDBN} already knows the OS ABI from its
15749 current target so it needs to find out also the type being returned to make the
15750 assignment into the right register(s).
15752 Normally, the selected stack frame has debug info. @value{GDBN} will always
15753 use the debug info instead of the implicit type of @var{expression} when the
15754 debug info is available. For example, if you type @kbd{return -1}, and the
15755 function in the current stack frame is declared to return a @code{long long
15756 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15757 into a @code{long long int}:
15760 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15762 (@value{GDBP}) return -1
15763 Make func return now? (y or n) y
15764 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15765 43 printf ("result=%lld\n", func ());
15769 However, if the selected stack frame does not have a debug info, e.g., if the
15770 function was compiled without debug info, @value{GDBN} has to find out the type
15771 to return from user. Specifying a different type by mistake may set the value
15772 in different inferior registers than the caller code expects. For example,
15773 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15774 of a @code{long long int} result for a debug info less function (on 32-bit
15775 architectures). Therefore the user is required to specify the return type by
15776 an appropriate cast explicitly:
15779 Breakpoint 2, 0x0040050b in func ()
15780 (@value{GDBP}) return -1
15781 Return value type not available for selected stack frame.
15782 Please use an explicit cast of the value to return.
15783 (@value{GDBP}) return (long long int) -1
15784 Make selected stack frame return now? (y or n) y
15785 #0 0x00400526 in main ()
15790 @section Calling Program Functions
15793 @cindex calling functions
15794 @cindex inferior functions, calling
15795 @item print @var{expr}
15796 Evaluate the expression @var{expr} and display the resulting value.
15797 @var{expr} may include calls to functions in the program being
15801 @item call @var{expr}
15802 Evaluate the expression @var{expr} without displaying @code{void}
15805 You can use this variant of the @code{print} command if you want to
15806 execute a function from your program that does not return anything
15807 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15808 with @code{void} returned values that @value{GDBN} will otherwise
15809 print. If the result is not void, it is printed and saved in the
15813 It is possible for the function you call via the @code{print} or
15814 @code{call} command to generate a signal (e.g., if there's a bug in
15815 the function, or if you passed it incorrect arguments). What happens
15816 in that case is controlled by the @code{set unwindonsignal} command.
15818 Similarly, with a C@t{++} program it is possible for the function you
15819 call via the @code{print} or @code{call} command to generate an
15820 exception that is not handled due to the constraints of the dummy
15821 frame. In this case, any exception that is raised in the frame, but has
15822 an out-of-frame exception handler will not be found. GDB builds a
15823 dummy-frame for the inferior function call, and the unwinder cannot
15824 seek for exception handlers outside of this dummy-frame. What happens
15825 in that case is controlled by the
15826 @code{set unwind-on-terminating-exception} command.
15829 @item set unwindonsignal
15830 @kindex set unwindonsignal
15831 @cindex unwind stack in called functions
15832 @cindex call dummy stack unwinding
15833 Set unwinding of the stack if a signal is received while in a function
15834 that @value{GDBN} called in the program being debugged. If set to on,
15835 @value{GDBN} unwinds the stack it created for the call and restores
15836 the context to what it was before the call. If set to off (the
15837 default), @value{GDBN} stops in the frame where the signal was
15840 @item show unwindonsignal
15841 @kindex show unwindonsignal
15842 Show the current setting of stack unwinding in the functions called by
15845 @item set unwind-on-terminating-exception
15846 @kindex set unwind-on-terminating-exception
15847 @cindex unwind stack in called functions with unhandled exceptions
15848 @cindex call dummy stack unwinding on unhandled exception.
15849 Set unwinding of the stack if a C@t{++} exception is raised, but left
15850 unhandled while in a function that @value{GDBN} called in the program being
15851 debugged. If set to on (the default), @value{GDBN} unwinds the stack
15852 it created for the call and restores the context to what it was before
15853 the call. If set to off, @value{GDBN} the exception is delivered to
15854 the default C@t{++} exception handler and the inferior terminated.
15856 @item show unwind-on-terminating-exception
15857 @kindex show unwind-on-terminating-exception
15858 Show the current setting of stack unwinding in the functions called by
15863 @cindex weak alias functions
15864 Sometimes, a function you wish to call is actually a @dfn{weak alias}
15865 for another function. In such case, @value{GDBN} might not pick up
15866 the type information, including the types of the function arguments,
15867 which causes @value{GDBN} to call the inferior function incorrectly.
15868 As a result, the called function will function erroneously and may
15869 even crash. A solution to that is to use the name of the aliased
15873 @section Patching Programs
15875 @cindex patching binaries
15876 @cindex writing into executables
15877 @cindex writing into corefiles
15879 By default, @value{GDBN} opens the file containing your program's
15880 executable code (or the corefile) read-only. This prevents accidental
15881 alterations to machine code; but it also prevents you from intentionally
15882 patching your program's binary.
15884 If you'd like to be able to patch the binary, you can specify that
15885 explicitly with the @code{set write} command. For example, you might
15886 want to turn on internal debugging flags, or even to make emergency
15892 @itemx set write off
15893 If you specify @samp{set write on}, @value{GDBN} opens executable and
15894 core files for both reading and writing; if you specify @kbd{set write
15895 off} (the default), @value{GDBN} opens them read-only.
15897 If you have already loaded a file, you must load it again (using the
15898 @code{exec-file} or @code{core-file} command) after changing @code{set
15899 write}, for your new setting to take effect.
15903 Display whether executable files and core files are opened for writing
15904 as well as reading.
15908 @chapter @value{GDBN} Files
15910 @value{GDBN} needs to know the file name of the program to be debugged,
15911 both in order to read its symbol table and in order to start your
15912 program. To debug a core dump of a previous run, you must also tell
15913 @value{GDBN} the name of the core dump file.
15916 * Files:: Commands to specify files
15917 * Separate Debug Files:: Debugging information in separate files
15918 * MiniDebugInfo:: Debugging information in a special section
15919 * Index Files:: Index files speed up GDB
15920 * Symbol Errors:: Errors reading symbol files
15921 * Data Files:: GDB data files
15925 @section Commands to Specify Files
15927 @cindex symbol table
15928 @cindex core dump file
15930 You may want to specify executable and core dump file names. The usual
15931 way to do this is at start-up time, using the arguments to
15932 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
15933 Out of @value{GDBN}}).
15935 Occasionally it is necessary to change to a different file during a
15936 @value{GDBN} session. Or you may run @value{GDBN} and forget to
15937 specify a file you want to use. Or you are debugging a remote target
15938 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
15939 Program}). In these situations the @value{GDBN} commands to specify
15940 new files are useful.
15943 @cindex executable file
15945 @item file @var{filename}
15946 Use @var{filename} as the program to be debugged. It is read for its
15947 symbols and for the contents of pure memory. It is also the program
15948 executed when you use the @code{run} command. If you do not specify a
15949 directory and the file is not found in the @value{GDBN} working directory,
15950 @value{GDBN} uses the environment variable @code{PATH} as a list of
15951 directories to search, just as the shell does when looking for a program
15952 to run. You can change the value of this variable, for both @value{GDBN}
15953 and your program, using the @code{path} command.
15955 @cindex unlinked object files
15956 @cindex patching object files
15957 You can load unlinked object @file{.o} files into @value{GDBN} using
15958 the @code{file} command. You will not be able to ``run'' an object
15959 file, but you can disassemble functions and inspect variables. Also,
15960 if the underlying BFD functionality supports it, you could use
15961 @kbd{gdb -write} to patch object files using this technique. Note
15962 that @value{GDBN} can neither interpret nor modify relocations in this
15963 case, so branches and some initialized variables will appear to go to
15964 the wrong place. But this feature is still handy from time to time.
15967 @code{file} with no argument makes @value{GDBN} discard any information it
15968 has on both executable file and the symbol table.
15971 @item exec-file @r{[} @var{filename} @r{]}
15972 Specify that the program to be run (but not the symbol table) is found
15973 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
15974 if necessary to locate your program. Omitting @var{filename} means to
15975 discard information on the executable file.
15977 @kindex symbol-file
15978 @item symbol-file @r{[} @var{filename} @r{]}
15979 Read symbol table information from file @var{filename}. @code{PATH} is
15980 searched when necessary. Use the @code{file} command to get both symbol
15981 table and program to run from the same file.
15983 @code{symbol-file} with no argument clears out @value{GDBN} information on your
15984 program's symbol table.
15986 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
15987 some breakpoints and auto-display expressions. This is because they may
15988 contain pointers to the internal data recording symbols and data types,
15989 which are part of the old symbol table data being discarded inside
15992 @code{symbol-file} does not repeat if you press @key{RET} again after
15995 When @value{GDBN} is configured for a particular environment, it
15996 understands debugging information in whatever format is the standard
15997 generated for that environment; you may use either a @sc{gnu} compiler, or
15998 other compilers that adhere to the local conventions.
15999 Best results are usually obtained from @sc{gnu} compilers; for example,
16000 using @code{@value{NGCC}} you can generate debugging information for
16003 For most kinds of object files, with the exception of old SVR3 systems
16004 using COFF, the @code{symbol-file} command does not normally read the
16005 symbol table in full right away. Instead, it scans the symbol table
16006 quickly to find which source files and which symbols are present. The
16007 details are read later, one source file at a time, as they are needed.
16009 The purpose of this two-stage reading strategy is to make @value{GDBN}
16010 start up faster. For the most part, it is invisible except for
16011 occasional pauses while the symbol table details for a particular source
16012 file are being read. (The @code{set verbose} command can turn these
16013 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16014 Warnings and Messages}.)
16016 We have not implemented the two-stage strategy for COFF yet. When the
16017 symbol table is stored in COFF format, @code{symbol-file} reads the
16018 symbol table data in full right away. Note that ``stabs-in-COFF''
16019 still does the two-stage strategy, since the debug info is actually
16023 @cindex reading symbols immediately
16024 @cindex symbols, reading immediately
16025 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16026 @itemx file @r{[} -readnow @r{]} @var{filename}
16027 You can override the @value{GDBN} two-stage strategy for reading symbol
16028 tables by using the @samp{-readnow} option with any of the commands that
16029 load symbol table information, if you want to be sure @value{GDBN} has the
16030 entire symbol table available.
16032 @c FIXME: for now no mention of directories, since this seems to be in
16033 @c flux. 13mar1992 status is that in theory GDB would look either in
16034 @c current dir or in same dir as myprog; but issues like competing
16035 @c GDB's, or clutter in system dirs, mean that in practice right now
16036 @c only current dir is used. FFish says maybe a special GDB hierarchy
16037 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16041 @item core-file @r{[}@var{filename}@r{]}
16043 Specify the whereabouts of a core dump file to be used as the ``contents
16044 of memory''. Traditionally, core files contain only some parts of the
16045 address space of the process that generated them; @value{GDBN} can access the
16046 executable file itself for other parts.
16048 @code{core-file} with no argument specifies that no core file is
16051 Note that the core file is ignored when your program is actually running
16052 under @value{GDBN}. So, if you have been running your program and you
16053 wish to debug a core file instead, you must kill the subprocess in which
16054 the program is running. To do this, use the @code{kill} command
16055 (@pxref{Kill Process, ,Killing the Child Process}).
16057 @kindex add-symbol-file
16058 @cindex dynamic linking
16059 @item add-symbol-file @var{filename} @var{address}
16060 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16061 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16062 The @code{add-symbol-file} command reads additional symbol table
16063 information from the file @var{filename}. You would use this command
16064 when @var{filename} has been dynamically loaded (by some other means)
16065 into the program that is running. @var{address} should be the memory
16066 address at which the file has been loaded; @value{GDBN} cannot figure
16067 this out for itself. You can additionally specify an arbitrary number
16068 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16069 section name and base address for that section. You can specify any
16070 @var{address} as an expression.
16072 The symbol table of the file @var{filename} is added to the symbol table
16073 originally read with the @code{symbol-file} command. You can use the
16074 @code{add-symbol-file} command any number of times; the new symbol data
16075 thus read keeps adding to the old. To discard all old symbol data
16076 instead, use the @code{symbol-file} command without any arguments.
16078 @cindex relocatable object files, reading symbols from
16079 @cindex object files, relocatable, reading symbols from
16080 @cindex reading symbols from relocatable object files
16081 @cindex symbols, reading from relocatable object files
16082 @cindex @file{.o} files, reading symbols from
16083 Although @var{filename} is typically a shared library file, an
16084 executable file, or some other object file which has been fully
16085 relocated for loading into a process, you can also load symbolic
16086 information from relocatable @file{.o} files, as long as:
16090 the file's symbolic information refers only to linker symbols defined in
16091 that file, not to symbols defined by other object files,
16093 every section the file's symbolic information refers to has actually
16094 been loaded into the inferior, as it appears in the file, and
16096 you can determine the address at which every section was loaded, and
16097 provide these to the @code{add-symbol-file} command.
16101 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16102 relocatable files into an already running program; such systems
16103 typically make the requirements above easy to meet. However, it's
16104 important to recognize that many native systems use complex link
16105 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16106 assembly, for example) that make the requirements difficult to meet. In
16107 general, one cannot assume that using @code{add-symbol-file} to read a
16108 relocatable object file's symbolic information will have the same effect
16109 as linking the relocatable object file into the program in the normal
16112 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16114 @kindex add-symbol-file-from-memory
16115 @cindex @code{syscall DSO}
16116 @cindex load symbols from memory
16117 @item add-symbol-file-from-memory @var{address}
16118 Load symbols from the given @var{address} in a dynamically loaded
16119 object file whose image is mapped directly into the inferior's memory.
16120 For example, the Linux kernel maps a @code{syscall DSO} into each
16121 process's address space; this DSO provides kernel-specific code for
16122 some system calls. The argument can be any expression whose
16123 evaluation yields the address of the file's shared object file header.
16124 For this command to work, you must have used @code{symbol-file} or
16125 @code{exec-file} commands in advance.
16127 @kindex add-shared-symbol-files
16129 @item add-shared-symbol-files @var{library-file}
16130 @itemx assf @var{library-file}
16131 The @code{add-shared-symbol-files} command can currently be used only
16132 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16133 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16134 @value{GDBN} automatically looks for shared libraries, however if
16135 @value{GDBN} does not find yours, you can invoke
16136 @code{add-shared-symbol-files}. It takes one argument: the shared
16137 library's file name. @code{assf} is a shorthand alias for
16138 @code{add-shared-symbol-files}.
16141 @item section @var{section} @var{addr}
16142 The @code{section} command changes the base address of the named
16143 @var{section} of the exec file to @var{addr}. This can be used if the
16144 exec file does not contain section addresses, (such as in the
16145 @code{a.out} format), or when the addresses specified in the file
16146 itself are wrong. Each section must be changed separately. The
16147 @code{info files} command, described below, lists all the sections and
16151 @kindex info target
16154 @code{info files} and @code{info target} are synonymous; both print the
16155 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16156 including the names of the executable and core dump files currently in
16157 use by @value{GDBN}, and the files from which symbols were loaded. The
16158 command @code{help target} lists all possible targets rather than
16161 @kindex maint info sections
16162 @item maint info sections
16163 Another command that can give you extra information about program sections
16164 is @code{maint info sections}. In addition to the section information
16165 displayed by @code{info files}, this command displays the flags and file
16166 offset of each section in the executable and core dump files. In addition,
16167 @code{maint info sections} provides the following command options (which
16168 may be arbitrarily combined):
16172 Display sections for all loaded object files, including shared libraries.
16173 @item @var{sections}
16174 Display info only for named @var{sections}.
16175 @item @var{section-flags}
16176 Display info only for sections for which @var{section-flags} are true.
16177 The section flags that @value{GDBN} currently knows about are:
16180 Section will have space allocated in the process when loaded.
16181 Set for all sections except those containing debug information.
16183 Section will be loaded from the file into the child process memory.
16184 Set for pre-initialized code and data, clear for @code{.bss} sections.
16186 Section needs to be relocated before loading.
16188 Section cannot be modified by the child process.
16190 Section contains executable code only.
16192 Section contains data only (no executable code).
16194 Section will reside in ROM.
16196 Section contains data for constructor/destructor lists.
16198 Section is not empty.
16200 An instruction to the linker to not output the section.
16201 @item COFF_SHARED_LIBRARY
16202 A notification to the linker that the section contains
16203 COFF shared library information.
16205 Section contains common symbols.
16208 @kindex set trust-readonly-sections
16209 @cindex read-only sections
16210 @item set trust-readonly-sections on
16211 Tell @value{GDBN} that readonly sections in your object file
16212 really are read-only (i.e.@: that their contents will not change).
16213 In that case, @value{GDBN} can fetch values from these sections
16214 out of the object file, rather than from the target program.
16215 For some targets (notably embedded ones), this can be a significant
16216 enhancement to debugging performance.
16218 The default is off.
16220 @item set trust-readonly-sections off
16221 Tell @value{GDBN} not to trust readonly sections. This means that
16222 the contents of the section might change while the program is running,
16223 and must therefore be fetched from the target when needed.
16225 @item show trust-readonly-sections
16226 Show the current setting of trusting readonly sections.
16229 All file-specifying commands allow both absolute and relative file names
16230 as arguments. @value{GDBN} always converts the file name to an absolute file
16231 name and remembers it that way.
16233 @cindex shared libraries
16234 @anchor{Shared Libraries}
16235 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16236 and IBM RS/6000 AIX shared libraries.
16238 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16239 shared libraries. @xref{Expat}.
16241 @value{GDBN} automatically loads symbol definitions from shared libraries
16242 when you use the @code{run} command, or when you examine a core file.
16243 (Before you issue the @code{run} command, @value{GDBN} does not understand
16244 references to a function in a shared library, however---unless you are
16245 debugging a core file).
16247 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16248 automatically loads the symbols at the time of the @code{shl_load} call.
16250 @c FIXME: some @value{GDBN} release may permit some refs to undef
16251 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16252 @c FIXME...lib; check this from time to time when updating manual
16254 There are times, however, when you may wish to not automatically load
16255 symbol definitions from shared libraries, such as when they are
16256 particularly large or there are many of them.
16258 To control the automatic loading of shared library symbols, use the
16262 @kindex set auto-solib-add
16263 @item set auto-solib-add @var{mode}
16264 If @var{mode} is @code{on}, symbols from all shared object libraries
16265 will be loaded automatically when the inferior begins execution, you
16266 attach to an independently started inferior, or when the dynamic linker
16267 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16268 is @code{off}, symbols must be loaded manually, using the
16269 @code{sharedlibrary} command. The default value is @code{on}.
16271 @cindex memory used for symbol tables
16272 If your program uses lots of shared libraries with debug info that
16273 takes large amounts of memory, you can decrease the @value{GDBN}
16274 memory footprint by preventing it from automatically loading the
16275 symbols from shared libraries. To that end, type @kbd{set
16276 auto-solib-add off} before running the inferior, then load each
16277 library whose debug symbols you do need with @kbd{sharedlibrary
16278 @var{regexp}}, where @var{regexp} is a regular expression that matches
16279 the libraries whose symbols you want to be loaded.
16281 @kindex show auto-solib-add
16282 @item show auto-solib-add
16283 Display the current autoloading mode.
16286 @cindex load shared library
16287 To explicitly load shared library symbols, use the @code{sharedlibrary}
16291 @kindex info sharedlibrary
16293 @item info share @var{regex}
16294 @itemx info sharedlibrary @var{regex}
16295 Print the names of the shared libraries which are currently loaded
16296 that match @var{regex}. If @var{regex} is omitted then print
16297 all shared libraries that are loaded.
16299 @kindex sharedlibrary
16301 @item sharedlibrary @var{regex}
16302 @itemx share @var{regex}
16303 Load shared object library symbols for files matching a
16304 Unix regular expression.
16305 As with files loaded automatically, it only loads shared libraries
16306 required by your program for a core file or after typing @code{run}. If
16307 @var{regex} is omitted all shared libraries required by your program are
16310 @item nosharedlibrary
16311 @kindex nosharedlibrary
16312 @cindex unload symbols from shared libraries
16313 Unload all shared object library symbols. This discards all symbols
16314 that have been loaded from all shared libraries. Symbols from shared
16315 libraries that were loaded by explicit user requests are not
16319 Sometimes you may wish that @value{GDBN} stops and gives you control
16320 when any of shared library events happen. The best way to do this is
16321 to use @code{catch load} and @code{catch unload} (@pxref{Set
16324 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16325 command for this. This command exists for historical reasons. It is
16326 less useful than setting a catchpoint, because it does not allow for
16327 conditions or commands as a catchpoint does.
16330 @item set stop-on-solib-events
16331 @kindex set stop-on-solib-events
16332 This command controls whether @value{GDBN} should give you control
16333 when the dynamic linker notifies it about some shared library event.
16334 The most common event of interest is loading or unloading of a new
16337 @item show stop-on-solib-events
16338 @kindex show stop-on-solib-events
16339 Show whether @value{GDBN} stops and gives you control when shared
16340 library events happen.
16343 Shared libraries are also supported in many cross or remote debugging
16344 configurations. @value{GDBN} needs to have access to the target's libraries;
16345 this can be accomplished either by providing copies of the libraries
16346 on the host system, or by asking @value{GDBN} to automatically retrieve the
16347 libraries from the target. If copies of the target libraries are
16348 provided, they need to be the same as the target libraries, although the
16349 copies on the target can be stripped as long as the copies on the host are
16352 @cindex where to look for shared libraries
16353 For remote debugging, you need to tell @value{GDBN} where the target
16354 libraries are, so that it can load the correct copies---otherwise, it
16355 may try to load the host's libraries. @value{GDBN} has two variables
16356 to specify the search directories for target libraries.
16359 @cindex prefix for shared library file names
16360 @cindex system root, alternate
16361 @kindex set solib-absolute-prefix
16362 @kindex set sysroot
16363 @item set sysroot @var{path}
16364 Use @var{path} as the system root for the program being debugged. Any
16365 absolute shared library paths will be prefixed with @var{path}; many
16366 runtime loaders store the absolute paths to the shared library in the
16367 target program's memory. If you use @code{set sysroot} to find shared
16368 libraries, they need to be laid out in the same way that they are on
16369 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16372 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16373 retrieve the target libraries from the remote system. This is only
16374 supported when using a remote target that supports the @code{remote get}
16375 command (@pxref{File Transfer,,Sending files to a remote system}).
16376 The part of @var{path} following the initial @file{remote:}
16377 (if present) is used as system root prefix on the remote file system.
16378 @footnote{If you want to specify a local system root using a directory
16379 that happens to be named @file{remote:}, you need to use some equivalent
16380 variant of the name like @file{./remote:}.}
16382 For targets with an MS-DOS based filesystem, such as MS-Windows and
16383 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16384 absolute file name with @var{path}. But first, on Unix hosts,
16385 @value{GDBN} converts all backslash directory separators into forward
16386 slashes, because the backslash is not a directory separator on Unix:
16389 c:\foo\bar.dll @result{} c:/foo/bar.dll
16392 Then, @value{GDBN} attempts prefixing the target file name with
16393 @var{path}, and looks for the resulting file name in the host file
16397 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16400 If that does not find the shared library, @value{GDBN} tries removing
16401 the @samp{:} character from the drive spec, both for convenience, and,
16402 for the case of the host file system not supporting file names with
16406 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16409 This makes it possible to have a system root that mirrors a target
16410 with more than one drive. E.g., you may want to setup your local
16411 copies of the target system shared libraries like so (note @samp{c} vs
16415 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16416 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16417 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16421 and point the system root at @file{/path/to/sysroot}, so that
16422 @value{GDBN} can find the correct copies of both
16423 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16425 If that still does not find the shared library, @value{GDBN} tries
16426 removing the whole drive spec from the target file name:
16429 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16432 This last lookup makes it possible to not care about the drive name,
16433 if you don't want or need to.
16435 The @code{set solib-absolute-prefix} command is an alias for @code{set
16438 @cindex default system root
16439 @cindex @samp{--with-sysroot}
16440 You can set the default system root by using the configure-time
16441 @samp{--with-sysroot} option. If the system root is inside
16442 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16443 @samp{--exec-prefix}), then the default system root will be updated
16444 automatically if the installed @value{GDBN} is moved to a new
16447 @kindex show sysroot
16449 Display the current shared library prefix.
16451 @kindex set solib-search-path
16452 @item set solib-search-path @var{path}
16453 If this variable is set, @var{path} is a colon-separated list of
16454 directories to search for shared libraries. @samp{solib-search-path}
16455 is used after @samp{sysroot} fails to locate the library, or if the
16456 path to the library is relative instead of absolute. If you want to
16457 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16458 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16459 finding your host's libraries. @samp{sysroot} is preferred; setting
16460 it to a nonexistent directory may interfere with automatic loading
16461 of shared library symbols.
16463 @kindex show solib-search-path
16464 @item show solib-search-path
16465 Display the current shared library search path.
16467 @cindex DOS file-name semantics of file names.
16468 @kindex set target-file-system-kind (unix|dos-based|auto)
16469 @kindex show target-file-system-kind
16470 @item set target-file-system-kind @var{kind}
16471 Set assumed file system kind for target reported file names.
16473 Shared library file names as reported by the target system may not
16474 make sense as is on the system @value{GDBN} is running on. For
16475 example, when remote debugging a target that has MS-DOS based file
16476 system semantics, from a Unix host, the target may be reporting to
16477 @value{GDBN} a list of loaded shared libraries with file names such as
16478 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16479 drive letters, so the @samp{c:\} prefix is not normally understood as
16480 indicating an absolute file name, and neither is the backslash
16481 normally considered a directory separator character. In that case,
16482 the native file system would interpret this whole absolute file name
16483 as a relative file name with no directory components. This would make
16484 it impossible to point @value{GDBN} at a copy of the remote target's
16485 shared libraries on the host using @code{set sysroot}, and impractical
16486 with @code{set solib-search-path}. Setting
16487 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16488 to interpret such file names similarly to how the target would, and to
16489 map them to file names valid on @value{GDBN}'s native file system
16490 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16491 to one of the supported file system kinds. In that case, @value{GDBN}
16492 tries to determine the appropriate file system variant based on the
16493 current target's operating system (@pxref{ABI, ,Configuring the
16494 Current ABI}). The supported file system settings are:
16498 Instruct @value{GDBN} to assume the target file system is of Unix
16499 kind. Only file names starting the forward slash (@samp{/}) character
16500 are considered absolute, and the directory separator character is also
16504 Instruct @value{GDBN} to assume the target file system is DOS based.
16505 File names starting with either a forward slash, or a drive letter
16506 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16507 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16508 considered directory separators.
16511 Instruct @value{GDBN} to use the file system kind associated with the
16512 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16513 This is the default.
16517 @cindex file name canonicalization
16518 @cindex base name differences
16519 When processing file names provided by the user, @value{GDBN}
16520 frequently needs to compare them to the file names recorded in the
16521 program's debug info. Normally, @value{GDBN} compares just the
16522 @dfn{base names} of the files as strings, which is reasonably fast
16523 even for very large programs. (The base name of a file is the last
16524 portion of its name, after stripping all the leading directories.)
16525 This shortcut in comparison is based upon the assumption that files
16526 cannot have more than one base name. This is usually true, but
16527 references to files that use symlinks or similar filesystem
16528 facilities violate that assumption. If your program records files
16529 using such facilities, or if you provide file names to @value{GDBN}
16530 using symlinks etc., you can set @code{basenames-may-differ} to
16531 @code{true} to instruct @value{GDBN} to completely canonicalize each
16532 pair of file names it needs to compare. This will make file-name
16533 comparisons accurate, but at a price of a significant slowdown.
16536 @item set basenames-may-differ
16537 @kindex set basenames-may-differ
16538 Set whether a source file may have multiple base names.
16540 @item show basenames-may-differ
16541 @kindex show basenames-may-differ
16542 Show whether a source file may have multiple base names.
16545 @node Separate Debug Files
16546 @section Debugging Information in Separate Files
16547 @cindex separate debugging information files
16548 @cindex debugging information in separate files
16549 @cindex @file{.debug} subdirectories
16550 @cindex debugging information directory, global
16551 @cindex global debugging information directories
16552 @cindex build ID, and separate debugging files
16553 @cindex @file{.build-id} directory
16555 @value{GDBN} allows you to put a program's debugging information in a
16556 file separate from the executable itself, in a way that allows
16557 @value{GDBN} to find and load the debugging information automatically.
16558 Since debugging information can be very large---sometimes larger
16559 than the executable code itself---some systems distribute debugging
16560 information for their executables in separate files, which users can
16561 install only when they need to debug a problem.
16563 @value{GDBN} supports two ways of specifying the separate debug info
16568 The executable contains a @dfn{debug link} that specifies the name of
16569 the separate debug info file. The separate debug file's name is
16570 usually @file{@var{executable}.debug}, where @var{executable} is the
16571 name of the corresponding executable file without leading directories
16572 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16573 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16574 checksum for the debug file, which @value{GDBN} uses to validate that
16575 the executable and the debug file came from the same build.
16578 The executable contains a @dfn{build ID}, a unique bit string that is
16579 also present in the corresponding debug info file. (This is supported
16580 only on some operating systems, notably those which use the ELF format
16581 for binary files and the @sc{gnu} Binutils.) For more details about
16582 this feature, see the description of the @option{--build-id}
16583 command-line option in @ref{Options, , Command Line Options, ld.info,
16584 The GNU Linker}. The debug info file's name is not specified
16585 explicitly by the build ID, but can be computed from the build ID, see
16589 Depending on the way the debug info file is specified, @value{GDBN}
16590 uses two different methods of looking for the debug file:
16594 For the ``debug link'' method, @value{GDBN} looks up the named file in
16595 the directory of the executable file, then in a subdirectory of that
16596 directory named @file{.debug}, and finally under each one of the global debug
16597 directories, in a subdirectory whose name is identical to the leading
16598 directories of the executable's absolute file name.
16601 For the ``build ID'' method, @value{GDBN} looks in the
16602 @file{.build-id} subdirectory of each one of the global debug directories for
16603 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16604 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16605 are the rest of the bit string. (Real build ID strings are 32 or more
16606 hex characters, not 10.)
16609 So, for example, suppose you ask @value{GDBN} to debug
16610 @file{/usr/bin/ls}, which has a debug link that specifies the
16611 file @file{ls.debug}, and a build ID whose value in hex is
16612 @code{abcdef1234}. If the list of the global debug directories includes
16613 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16614 debug information files, in the indicated order:
16618 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16620 @file{/usr/bin/ls.debug}
16622 @file{/usr/bin/.debug/ls.debug}
16624 @file{/usr/lib/debug/usr/bin/ls.debug}.
16627 @anchor{debug-file-directory}
16628 Global debugging info directories default to what is set by @value{GDBN}
16629 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16630 you can also set the global debugging info directories, and view the list
16631 @value{GDBN} is currently using.
16635 @kindex set debug-file-directory
16636 @item set debug-file-directory @var{directories}
16637 Set the directories which @value{GDBN} searches for separate debugging
16638 information files to @var{directory}. Multiple path components can be set
16639 concatenating them by a path separator.
16641 @kindex show debug-file-directory
16642 @item show debug-file-directory
16643 Show the directories @value{GDBN} searches for separate debugging
16648 @cindex @code{.gnu_debuglink} sections
16649 @cindex debug link sections
16650 A debug link is a special section of the executable file named
16651 @code{.gnu_debuglink}. The section must contain:
16655 A filename, with any leading directory components removed, followed by
16658 zero to three bytes of padding, as needed to reach the next four-byte
16659 boundary within the section, and
16661 a four-byte CRC checksum, stored in the same endianness used for the
16662 executable file itself. The checksum is computed on the debugging
16663 information file's full contents by the function given below, passing
16664 zero as the @var{crc} argument.
16667 Any executable file format can carry a debug link, as long as it can
16668 contain a section named @code{.gnu_debuglink} with the contents
16671 @cindex @code{.note.gnu.build-id} sections
16672 @cindex build ID sections
16673 The build ID is a special section in the executable file (and in other
16674 ELF binary files that @value{GDBN} may consider). This section is
16675 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16676 It contains unique identification for the built files---the ID remains
16677 the same across multiple builds of the same build tree. The default
16678 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16679 content for the build ID string. The same section with an identical
16680 value is present in the original built binary with symbols, in its
16681 stripped variant, and in the separate debugging information file.
16683 The debugging information file itself should be an ordinary
16684 executable, containing a full set of linker symbols, sections, and
16685 debugging information. The sections of the debugging information file
16686 should have the same names, addresses, and sizes as the original file,
16687 but they need not contain any data---much like a @code{.bss} section
16688 in an ordinary executable.
16690 The @sc{gnu} binary utilities (Binutils) package includes the
16691 @samp{objcopy} utility that can produce
16692 the separated executable / debugging information file pairs using the
16693 following commands:
16696 @kbd{objcopy --only-keep-debug foo foo.debug}
16701 These commands remove the debugging
16702 information from the executable file @file{foo} and place it in the file
16703 @file{foo.debug}. You can use the first, second or both methods to link the
16708 The debug link method needs the following additional command to also leave
16709 behind a debug link in @file{foo}:
16712 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16715 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16716 a version of the @code{strip} command such that the command @kbd{strip foo -f
16717 foo.debug} has the same functionality as the two @code{objcopy} commands and
16718 the @code{ln -s} command above, together.
16721 Build ID gets embedded into the main executable using @code{ld --build-id} or
16722 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16723 compatibility fixes for debug files separation are present in @sc{gnu} binary
16724 utilities (Binutils) package since version 2.18.
16729 @cindex CRC algorithm definition
16730 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16731 IEEE 802.3 using the polynomial:
16733 @c TexInfo requires naked braces for multi-digit exponents for Tex
16734 @c output, but this causes HTML output to barf. HTML has to be set using
16735 @c raw commands. So we end up having to specify this equation in 2
16740 <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>
16741 + <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
16747 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16748 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16752 The function is computed byte at a time, taking the least
16753 significant bit of each byte first. The initial pattern
16754 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16755 the final result is inverted to ensure trailing zeros also affect the
16758 @emph{Note:} This is the same CRC polynomial as used in handling the
16759 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16760 , @value{GDBN} Remote Serial Protocol}). However in the
16761 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16762 significant bit first, and the result is not inverted, so trailing
16763 zeros have no effect on the CRC value.
16765 To complete the description, we show below the code of the function
16766 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16767 initially supplied @code{crc} argument means that an initial call to
16768 this function passing in zero will start computing the CRC using
16771 @kindex gnu_debuglink_crc32
16774 gnu_debuglink_crc32 (unsigned long crc,
16775 unsigned char *buf, size_t len)
16777 static const unsigned long crc32_table[256] =
16779 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16780 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16781 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16782 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16783 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16784 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16785 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16786 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16787 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16788 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16789 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16790 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16791 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16792 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16793 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16794 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16795 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16796 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16797 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16798 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16799 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16800 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16801 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16802 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16803 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16804 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16805 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16806 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16807 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16808 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16809 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16810 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16811 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16812 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16813 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16814 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16815 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16816 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16817 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16818 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16819 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16820 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16821 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16822 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16823 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16824 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16825 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16826 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16827 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16828 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16829 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16832 unsigned char *end;
16834 crc = ~crc & 0xffffffff;
16835 for (end = buf + len; buf < end; ++buf)
16836 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
16837 return ~crc & 0xffffffff;
16842 This computation does not apply to the ``build ID'' method.
16844 @node MiniDebugInfo
16845 @section Debugging information in a special section
16846 @cindex separate debug sections
16847 @cindex @samp{.gnu_debugdata} section
16849 Some systems ship pre-built executables and libraries that have a
16850 special @samp{.gnu_debugdata} section. This feature is called
16851 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
16852 is used to supply extra symbols for backtraces.
16854 The intent of this section is to provide extra minimal debugging
16855 information for use in simple backtraces. It is not intended to be a
16856 replacement for full separate debugging information (@pxref{Separate
16857 Debug Files}). The example below shows the intended use; however,
16858 @value{GDBN} does not currently put restrictions on what sort of
16859 debugging information might be included in the section.
16861 @value{GDBN} has support for this extension. If the section exists,
16862 then it is used provided that no other source of debugging information
16863 can be found, and that @value{GDBN} was configured with LZMA support.
16865 This section can be easily created using @command{objcopy} and other
16866 standard utilities:
16869 # Extract the dynamic symbols from the main binary, there is no need
16870 # to also have these in the normal symbol table
16871 nm -D @var{binary} --format=posix --defined-only \
16872 | awk '@{ print $1 @}' | sort > dynsyms
16874 # Extract all the text (i.e. function) symbols from the debuginfo .
16875 nm @var{binary} --format=posix --defined-only \
16876 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
16879 # Keep all the function symbols not already in the dynamic symbol
16881 comm -13 dynsyms funcsyms > keep_symbols
16883 # Copy the full debuginfo, keeping only a minimal set of symbols and
16884 # removing some unnecessary sections.
16885 objcopy -S --remove-section .gdb_index --remove-section .comment \
16886 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
16888 # Inject the compressed data into the .gnu_debugdata section of the
16891 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
16895 @section Index Files Speed Up @value{GDBN}
16896 @cindex index files
16897 @cindex @samp{.gdb_index} section
16899 When @value{GDBN} finds a symbol file, it scans the symbols in the
16900 file in order to construct an internal symbol table. This lets most
16901 @value{GDBN} operations work quickly---at the cost of a delay early
16902 on. For large programs, this delay can be quite lengthy, so
16903 @value{GDBN} provides a way to build an index, which speeds up
16906 The index is stored as a section in the symbol file. @value{GDBN} can
16907 write the index to a file, then you can put it into the symbol file
16908 using @command{objcopy}.
16910 To create an index file, use the @code{save gdb-index} command:
16913 @item save gdb-index @var{directory}
16914 @kindex save gdb-index
16915 Create an index file for each symbol file currently known by
16916 @value{GDBN}. Each file is named after its corresponding symbol file,
16917 with @samp{.gdb-index} appended, and is written into the given
16921 Once you have created an index file you can merge it into your symbol
16922 file, here named @file{symfile}, using @command{objcopy}:
16925 $ objcopy --add-section .gdb_index=symfile.gdb-index \
16926 --set-section-flags .gdb_index=readonly symfile symfile
16929 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
16930 sections that have been deprecated. Usually they are deprecated because
16931 they are missing a new feature or have performance issues.
16932 To tell @value{GDBN} to use a deprecated index section anyway
16933 specify @code{set use-deprecated-index-sections on}.
16934 The default is @code{off}.
16935 This can speed up startup, but may result in some functionality being lost.
16936 @xref{Index Section Format}.
16938 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
16939 must be done before gdb reads the file. The following will not work:
16942 $ gdb -ex "set use-deprecated-index-sections on" <program>
16945 Instead you must do, for example,
16948 $ gdb -iex "set use-deprecated-index-sections on" <program>
16951 There are currently some limitation on indices. They only work when
16952 for DWARF debugging information, not stabs. And, they do not
16953 currently work for programs using Ada.
16955 @node Symbol Errors
16956 @section Errors Reading Symbol Files
16958 While reading a symbol file, @value{GDBN} occasionally encounters problems,
16959 such as symbol types it does not recognize, or known bugs in compiler
16960 output. By default, @value{GDBN} does not notify you of such problems, since
16961 they are relatively common and primarily of interest to people
16962 debugging compilers. If you are interested in seeing information
16963 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
16964 only one message about each such type of problem, no matter how many
16965 times the problem occurs; or you can ask @value{GDBN} to print more messages,
16966 to see how many times the problems occur, with the @code{set
16967 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
16970 The messages currently printed, and their meanings, include:
16973 @item inner block not inside outer block in @var{symbol}
16975 The symbol information shows where symbol scopes begin and end
16976 (such as at the start of a function or a block of statements). This
16977 error indicates that an inner scope block is not fully contained
16978 in its outer scope blocks.
16980 @value{GDBN} circumvents the problem by treating the inner block as if it had
16981 the same scope as the outer block. In the error message, @var{symbol}
16982 may be shown as ``@code{(don't know)}'' if the outer block is not a
16985 @item block at @var{address} out of order
16987 The symbol information for symbol scope blocks should occur in
16988 order of increasing addresses. This error indicates that it does not
16991 @value{GDBN} does not circumvent this problem, and has trouble
16992 locating symbols in the source file whose symbols it is reading. (You
16993 can often determine what source file is affected by specifying
16994 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
16997 @item bad block start address patched
16999 The symbol information for a symbol scope block has a start address
17000 smaller than the address of the preceding source line. This is known
17001 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17003 @value{GDBN} circumvents the problem by treating the symbol scope block as
17004 starting on the previous source line.
17006 @item bad string table offset in symbol @var{n}
17009 Symbol number @var{n} contains a pointer into the string table which is
17010 larger than the size of the string table.
17012 @value{GDBN} circumvents the problem by considering the symbol to have the
17013 name @code{foo}, which may cause other problems if many symbols end up
17016 @item unknown symbol type @code{0x@var{nn}}
17018 The symbol information contains new data types that @value{GDBN} does
17019 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17020 uncomprehended information, in hexadecimal.
17022 @value{GDBN} circumvents the error by ignoring this symbol information.
17023 This usually allows you to debug your program, though certain symbols
17024 are not accessible. If you encounter such a problem and feel like
17025 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17026 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17027 and examine @code{*bufp} to see the symbol.
17029 @item stub type has NULL name
17031 @value{GDBN} could not find the full definition for a struct or class.
17033 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17034 The symbol information for a C@t{++} member function is missing some
17035 information that recent versions of the compiler should have output for
17038 @item info mismatch between compiler and debugger
17040 @value{GDBN} could not parse a type specification output by the compiler.
17045 @section GDB Data Files
17047 @cindex prefix for data files
17048 @value{GDBN} will sometimes read an auxiliary data file. These files
17049 are kept in a directory known as the @dfn{data directory}.
17051 You can set the data directory's name, and view the name @value{GDBN}
17052 is currently using.
17055 @kindex set data-directory
17056 @item set data-directory @var{directory}
17057 Set the directory which @value{GDBN} searches for auxiliary data files
17058 to @var{directory}.
17060 @kindex show data-directory
17061 @item show data-directory
17062 Show the directory @value{GDBN} searches for auxiliary data files.
17065 @cindex default data directory
17066 @cindex @samp{--with-gdb-datadir}
17067 You can set the default data directory by using the configure-time
17068 @samp{--with-gdb-datadir} option. If the data directory is inside
17069 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17070 @samp{--exec-prefix}), then the default data directory will be updated
17071 automatically if the installed @value{GDBN} is moved to a new
17074 The data directory may also be specified with the
17075 @code{--data-directory} command line option.
17076 @xref{Mode Options}.
17079 @chapter Specifying a Debugging Target
17081 @cindex debugging target
17082 A @dfn{target} is the execution environment occupied by your program.
17084 Often, @value{GDBN} runs in the same host environment as your program;
17085 in that case, the debugging target is specified as a side effect when
17086 you use the @code{file} or @code{core} commands. When you need more
17087 flexibility---for example, running @value{GDBN} on a physically separate
17088 host, or controlling a standalone system over a serial port or a
17089 realtime system over a TCP/IP connection---you can use the @code{target}
17090 command to specify one of the target types configured for @value{GDBN}
17091 (@pxref{Target Commands, ,Commands for Managing Targets}).
17093 @cindex target architecture
17094 It is possible to build @value{GDBN} for several different @dfn{target
17095 architectures}. When @value{GDBN} is built like that, you can choose
17096 one of the available architectures with the @kbd{set architecture}
17100 @kindex set architecture
17101 @kindex show architecture
17102 @item set architecture @var{arch}
17103 This command sets the current target architecture to @var{arch}. The
17104 value of @var{arch} can be @code{"auto"}, in addition to one of the
17105 supported architectures.
17107 @item show architecture
17108 Show the current target architecture.
17110 @item set processor
17112 @kindex set processor
17113 @kindex show processor
17114 These are alias commands for, respectively, @code{set architecture}
17115 and @code{show architecture}.
17119 * Active Targets:: Active targets
17120 * Target Commands:: Commands for managing targets
17121 * Byte Order:: Choosing target byte order
17124 @node Active Targets
17125 @section Active Targets
17127 @cindex stacking targets
17128 @cindex active targets
17129 @cindex multiple targets
17131 There are multiple classes of targets such as: processes, executable files or
17132 recording sessions. Core files belong to the process class, making core file
17133 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17134 on multiple active targets, one in each class. This allows you to (for
17135 example) start a process and inspect its activity, while still having access to
17136 the executable file after the process finishes. Or if you start process
17137 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17138 presented a virtual layer of the recording target, while the process target
17139 remains stopped at the chronologically last point of the process execution.
17141 Use the @code{core-file} and @code{exec-file} commands to select a new core
17142 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17143 specify as a target a process that is already running, use the @code{attach}
17144 command (@pxref{Attach, ,Debugging an Already-running Process}).
17146 @node Target Commands
17147 @section Commands for Managing Targets
17150 @item target @var{type} @var{parameters}
17151 Connects the @value{GDBN} host environment to a target machine or
17152 process. A target is typically a protocol for talking to debugging
17153 facilities. You use the argument @var{type} to specify the type or
17154 protocol of the target machine.
17156 Further @var{parameters} are interpreted by the target protocol, but
17157 typically include things like device names or host names to connect
17158 with, process numbers, and baud rates.
17160 The @code{target} command does not repeat if you press @key{RET} again
17161 after executing the command.
17163 @kindex help target
17165 Displays the names of all targets available. To display targets
17166 currently selected, use either @code{info target} or @code{info files}
17167 (@pxref{Files, ,Commands to Specify Files}).
17169 @item help target @var{name}
17170 Describe a particular target, including any parameters necessary to
17173 @kindex set gnutarget
17174 @item set gnutarget @var{args}
17175 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17176 knows whether it is reading an @dfn{executable},
17177 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17178 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17179 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17182 @emph{Warning:} To specify a file format with @code{set gnutarget},
17183 you must know the actual BFD name.
17187 @xref{Files, , Commands to Specify Files}.
17189 @kindex show gnutarget
17190 @item show gnutarget
17191 Use the @code{show gnutarget} command to display what file format
17192 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17193 @value{GDBN} will determine the file format for each file automatically,
17194 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17197 @cindex common targets
17198 Here are some common targets (available, or not, depending on the GDB
17203 @item target exec @var{program}
17204 @cindex executable file target
17205 An executable file. @samp{target exec @var{program}} is the same as
17206 @samp{exec-file @var{program}}.
17208 @item target core @var{filename}
17209 @cindex core dump file target
17210 A core dump file. @samp{target core @var{filename}} is the same as
17211 @samp{core-file @var{filename}}.
17213 @item target remote @var{medium}
17214 @cindex remote target
17215 A remote system connected to @value{GDBN} via a serial line or network
17216 connection. This command tells @value{GDBN} to use its own remote
17217 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17219 For example, if you have a board connected to @file{/dev/ttya} on the
17220 machine running @value{GDBN}, you could say:
17223 target remote /dev/ttya
17226 @code{target remote} supports the @code{load} command. This is only
17227 useful if you have some other way of getting the stub to the target
17228 system, and you can put it somewhere in memory where it won't get
17229 clobbered by the download.
17231 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17232 @cindex built-in simulator target
17233 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17241 works; however, you cannot assume that a specific memory map, device
17242 drivers, or even basic I/O is available, although some simulators do
17243 provide these. For info about any processor-specific simulator details,
17244 see the appropriate section in @ref{Embedded Processors, ,Embedded
17249 Some configurations may include these targets as well:
17253 @item target nrom @var{dev}
17254 @cindex NetROM ROM emulator target
17255 NetROM ROM emulator. This target only supports downloading.
17259 Different targets are available on different configurations of @value{GDBN};
17260 your configuration may have more or fewer targets.
17262 Many remote targets require you to download the executable's code once
17263 you've successfully established a connection. You may wish to control
17264 various aspects of this process.
17269 @kindex set hash@r{, for remote monitors}
17270 @cindex hash mark while downloading
17271 This command controls whether a hash mark @samp{#} is displayed while
17272 downloading a file to the remote monitor. If on, a hash mark is
17273 displayed after each S-record is successfully downloaded to the
17277 @kindex show hash@r{, for remote monitors}
17278 Show the current status of displaying the hash mark.
17280 @item set debug monitor
17281 @kindex set debug monitor
17282 @cindex display remote monitor communications
17283 Enable or disable display of communications messages between
17284 @value{GDBN} and the remote monitor.
17286 @item show debug monitor
17287 @kindex show debug monitor
17288 Show the current status of displaying communications between
17289 @value{GDBN} and the remote monitor.
17294 @kindex load @var{filename}
17295 @item load @var{filename}
17297 Depending on what remote debugging facilities are configured into
17298 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17299 is meant to make @var{filename} (an executable) available for debugging
17300 on the remote system---by downloading, or dynamic linking, for example.
17301 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17302 the @code{add-symbol-file} command.
17304 If your @value{GDBN} does not have a @code{load} command, attempting to
17305 execute it gets the error message ``@code{You can't do that when your
17306 target is @dots{}}''
17308 The file is loaded at whatever address is specified in the executable.
17309 For some object file formats, you can specify the load address when you
17310 link the program; for other formats, like a.out, the object file format
17311 specifies a fixed address.
17312 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17314 Depending on the remote side capabilities, @value{GDBN} may be able to
17315 load programs into flash memory.
17317 @code{load} does not repeat if you press @key{RET} again after using it.
17321 @section Choosing Target Byte Order
17323 @cindex choosing target byte order
17324 @cindex target byte order
17326 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17327 offer the ability to run either big-endian or little-endian byte
17328 orders. Usually the executable or symbol will include a bit to
17329 designate the endian-ness, and you will not need to worry about
17330 which to use. However, you may still find it useful to adjust
17331 @value{GDBN}'s idea of processor endian-ness manually.
17335 @item set endian big
17336 Instruct @value{GDBN} to assume the target is big-endian.
17338 @item set endian little
17339 Instruct @value{GDBN} to assume the target is little-endian.
17341 @item set endian auto
17342 Instruct @value{GDBN} to use the byte order associated with the
17346 Display @value{GDBN}'s current idea of the target byte order.
17350 Note that these commands merely adjust interpretation of symbolic
17351 data on the host, and that they have absolutely no effect on the
17355 @node Remote Debugging
17356 @chapter Debugging Remote Programs
17357 @cindex remote debugging
17359 If you are trying to debug a program running on a machine that cannot run
17360 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17361 For example, you might use remote debugging on an operating system kernel,
17362 or on a small system which does not have a general purpose operating system
17363 powerful enough to run a full-featured debugger.
17365 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17366 to make this work with particular debugging targets. In addition,
17367 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17368 but not specific to any particular target system) which you can use if you
17369 write the remote stubs---the code that runs on the remote system to
17370 communicate with @value{GDBN}.
17372 Other remote targets may be available in your
17373 configuration of @value{GDBN}; use @code{help target} to list them.
17376 * Connecting:: Connecting to a remote target
17377 * File Transfer:: Sending files to a remote system
17378 * Server:: Using the gdbserver program
17379 * Remote Configuration:: Remote configuration
17380 * Remote Stub:: Implementing a remote stub
17384 @section Connecting to a Remote Target
17386 On the @value{GDBN} host machine, you will need an unstripped copy of
17387 your program, since @value{GDBN} needs symbol and debugging information.
17388 Start up @value{GDBN} as usual, using the name of the local copy of your
17389 program as the first argument.
17391 @cindex @code{target remote}
17392 @value{GDBN} can communicate with the target over a serial line, or
17393 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17394 each case, @value{GDBN} uses the same protocol for debugging your
17395 program; only the medium carrying the debugging packets varies. The
17396 @code{target remote} command establishes a connection to the target.
17397 Its arguments indicate which medium to use:
17401 @item target remote @var{serial-device}
17402 @cindex serial line, @code{target remote}
17403 Use @var{serial-device} to communicate with the target. For example,
17404 to use a serial line connected to the device named @file{/dev/ttyb}:
17407 target remote /dev/ttyb
17410 If you're using a serial line, you may want to give @value{GDBN} the
17411 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17412 (@pxref{Remote Configuration, set remotebaud}) before the
17413 @code{target} command.
17415 @item target remote @code{@var{host}:@var{port}}
17416 @itemx target remote @code{tcp:@var{host}:@var{port}}
17417 @cindex @acronym{TCP} port, @code{target remote}
17418 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17419 The @var{host} may be either a host name or a numeric @acronym{IP}
17420 address; @var{port} must be a decimal number. The @var{host} could be
17421 the target machine itself, if it is directly connected to the net, or
17422 it might be a terminal server which in turn has a serial line to the
17425 For example, to connect to port 2828 on a terminal server named
17429 target remote manyfarms:2828
17432 If your remote target is actually running on the same machine as your
17433 debugger session (e.g.@: a simulator for your target running on the
17434 same host), you can omit the hostname. For example, to connect to
17435 port 1234 on your local machine:
17438 target remote :1234
17442 Note that the colon is still required here.
17444 @item target remote @code{udp:@var{host}:@var{port}}
17445 @cindex @acronym{UDP} port, @code{target remote}
17446 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17447 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17450 target remote udp:manyfarms:2828
17453 When using a @acronym{UDP} connection for remote debugging, you should
17454 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17455 can silently drop packets on busy or unreliable networks, which will
17456 cause havoc with your debugging session.
17458 @item target remote | @var{command}
17459 @cindex pipe, @code{target remote} to
17460 Run @var{command} in the background and communicate with it using a
17461 pipe. The @var{command} is a shell command, to be parsed and expanded
17462 by the system's command shell, @code{/bin/sh}; it should expect remote
17463 protocol packets on its standard input, and send replies on its
17464 standard output. You could use this to run a stand-alone simulator
17465 that speaks the remote debugging protocol, to make net connections
17466 using programs like @code{ssh}, or for other similar tricks.
17468 If @var{command} closes its standard output (perhaps by exiting),
17469 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17470 program has already exited, this will have no effect.)
17474 Once the connection has been established, you can use all the usual
17475 commands to examine and change data. The remote program is already
17476 running; you can use @kbd{step} and @kbd{continue}, and you do not
17477 need to use @kbd{run}.
17479 @cindex interrupting remote programs
17480 @cindex remote programs, interrupting
17481 Whenever @value{GDBN} is waiting for the remote program, if you type the
17482 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17483 program. This may or may not succeed, depending in part on the hardware
17484 and the serial drivers the remote system uses. If you type the
17485 interrupt character once again, @value{GDBN} displays this prompt:
17488 Interrupted while waiting for the program.
17489 Give up (and stop debugging it)? (y or n)
17492 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17493 (If you decide you want to try again later, you can use @samp{target
17494 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17495 goes back to waiting.
17498 @kindex detach (remote)
17500 When you have finished debugging the remote program, you can use the
17501 @code{detach} command to release it from @value{GDBN} control.
17502 Detaching from the target normally resumes its execution, but the results
17503 will depend on your particular remote stub. After the @code{detach}
17504 command, @value{GDBN} is free to connect to another target.
17508 The @code{disconnect} command behaves like @code{detach}, except that
17509 the target is generally not resumed. It will wait for @value{GDBN}
17510 (this instance or another one) to connect and continue debugging. After
17511 the @code{disconnect} command, @value{GDBN} is again free to connect to
17514 @cindex send command to remote monitor
17515 @cindex extend @value{GDBN} for remote targets
17516 @cindex add new commands for external monitor
17518 @item monitor @var{cmd}
17519 This command allows you to send arbitrary commands directly to the
17520 remote monitor. Since @value{GDBN} doesn't care about the commands it
17521 sends like this, this command is the way to extend @value{GDBN}---you
17522 can add new commands that only the external monitor will understand
17526 @node File Transfer
17527 @section Sending files to a remote system
17528 @cindex remote target, file transfer
17529 @cindex file transfer
17530 @cindex sending files to remote systems
17532 Some remote targets offer the ability to transfer files over the same
17533 connection used to communicate with @value{GDBN}. This is convenient
17534 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17535 running @code{gdbserver} over a network interface. For other targets,
17536 e.g.@: embedded devices with only a single serial port, this may be
17537 the only way to upload or download files.
17539 Not all remote targets support these commands.
17543 @item remote put @var{hostfile} @var{targetfile}
17544 Copy file @var{hostfile} from the host system (the machine running
17545 @value{GDBN}) to @var{targetfile} on the target system.
17548 @item remote get @var{targetfile} @var{hostfile}
17549 Copy file @var{targetfile} from the target system to @var{hostfile}
17550 on the host system.
17552 @kindex remote delete
17553 @item remote delete @var{targetfile}
17554 Delete @var{targetfile} from the target system.
17559 @section Using the @code{gdbserver} Program
17562 @cindex remote connection without stubs
17563 @code{gdbserver} is a control program for Unix-like systems, which
17564 allows you to connect your program with a remote @value{GDBN} via
17565 @code{target remote}---but without linking in the usual debugging stub.
17567 @code{gdbserver} is not a complete replacement for the debugging stubs,
17568 because it requires essentially the same operating-system facilities
17569 that @value{GDBN} itself does. In fact, a system that can run
17570 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17571 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17572 because it is a much smaller program than @value{GDBN} itself. It is
17573 also easier to port than all of @value{GDBN}, so you may be able to get
17574 started more quickly on a new system by using @code{gdbserver}.
17575 Finally, if you develop code for real-time systems, you may find that
17576 the tradeoffs involved in real-time operation make it more convenient to
17577 do as much development work as possible on another system, for example
17578 by cross-compiling. You can use @code{gdbserver} to make a similar
17579 choice for debugging.
17581 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17582 or a TCP connection, using the standard @value{GDBN} remote serial
17586 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17587 Do not run @code{gdbserver} connected to any public network; a
17588 @value{GDBN} connection to @code{gdbserver} provides access to the
17589 target system with the same privileges as the user running
17593 @subsection Running @code{gdbserver}
17594 @cindex arguments, to @code{gdbserver}
17595 @cindex @code{gdbserver}, command-line arguments
17597 Run @code{gdbserver} on the target system. You need a copy of the
17598 program you want to debug, including any libraries it requires.
17599 @code{gdbserver} does not need your program's symbol table, so you can
17600 strip the program if necessary to save space. @value{GDBN} on the host
17601 system does all the symbol handling.
17603 To use the server, you must tell it how to communicate with @value{GDBN};
17604 the name of your program; and the arguments for your program. The usual
17608 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17611 @var{comm} is either a device name (to use a serial line), or a TCP
17612 hostname and portnumber, or @code{-} or @code{stdio} to use
17613 stdin/stdout of @code{gdbserver}.
17614 For example, to debug Emacs with the argument
17615 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17619 target> gdbserver /dev/com1 emacs foo.txt
17622 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17625 To use a TCP connection instead of a serial line:
17628 target> gdbserver host:2345 emacs foo.txt
17631 The only difference from the previous example is the first argument,
17632 specifying that you are communicating with the host @value{GDBN} via
17633 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17634 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17635 (Currently, the @samp{host} part is ignored.) You can choose any number
17636 you want for the port number as long as it does not conflict with any
17637 TCP ports already in use on the target system (for example, @code{23} is
17638 reserved for @code{telnet}).@footnote{If you choose a port number that
17639 conflicts with another service, @code{gdbserver} prints an error message
17640 and exits.} You must use the same port number with the host @value{GDBN}
17641 @code{target remote} command.
17643 The @code{stdio} connection is useful when starting @code{gdbserver}
17647 (gdb) target remote | ssh -T hostname gdbserver - hello
17650 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17651 and we don't want escape-character handling. Ssh does this by default when
17652 a command is provided, the flag is provided to make it explicit.
17653 You could elide it if you want to.
17655 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17656 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17657 display through a pipe connected to gdbserver.
17658 Both @code{stdout} and @code{stderr} use the same pipe.
17660 @subsubsection Attaching to a Running Program
17661 @cindex attach to a program, @code{gdbserver}
17662 @cindex @option{--attach}, @code{gdbserver} option
17664 On some targets, @code{gdbserver} can also attach to running programs.
17665 This is accomplished via the @code{--attach} argument. The syntax is:
17668 target> gdbserver --attach @var{comm} @var{pid}
17671 @var{pid} is the process ID of a currently running process. It isn't necessary
17672 to point @code{gdbserver} at a binary for the running process.
17675 You can debug processes by name instead of process ID if your target has the
17676 @code{pidof} utility:
17679 target> gdbserver --attach @var{comm} `pidof @var{program}`
17682 In case more than one copy of @var{program} is running, or @var{program}
17683 has multiple threads, most versions of @code{pidof} support the
17684 @code{-s} option to only return the first process ID.
17686 @subsubsection Multi-Process Mode for @code{gdbserver}
17687 @cindex @code{gdbserver}, multiple processes
17688 @cindex multiple processes with @code{gdbserver}
17690 When you connect to @code{gdbserver} using @code{target remote},
17691 @code{gdbserver} debugs the specified program only once. When the
17692 program exits, or you detach from it, @value{GDBN} closes the connection
17693 and @code{gdbserver} exits.
17695 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17696 enters multi-process mode. When the debugged program exits, or you
17697 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17698 though no program is running. The @code{run} and @code{attach}
17699 commands instruct @code{gdbserver} to run or attach to a new program.
17700 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17701 remote exec-file}) to select the program to run. Command line
17702 arguments are supported, except for wildcard expansion and I/O
17703 redirection (@pxref{Arguments}).
17705 @cindex @option{--multi}, @code{gdbserver} option
17706 To start @code{gdbserver} without supplying an initial command to run
17707 or process ID to attach, use the @option{--multi} command line option.
17708 Then you can connect using @kbd{target extended-remote} and start
17709 the program you want to debug.
17711 In multi-process mode @code{gdbserver} does not automatically exit unless you
17712 use the option @option{--once}. You can terminate it by using
17713 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17714 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17715 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17716 @option{--multi} option to @code{gdbserver} has no influence on that.
17718 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17720 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17722 @code{gdbserver} normally terminates after all of its debugged processes have
17723 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17724 extended-remote}, @code{gdbserver} stays running even with no processes left.
17725 @value{GDBN} normally terminates the spawned debugged process on its exit,
17726 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17727 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17728 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17729 stays running even in the @kbd{target remote} mode.
17731 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17732 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17733 completeness, at most one @value{GDBN} can be connected at a time.
17735 @cindex @option{--once}, @code{gdbserver} option
17736 By default, @code{gdbserver} keeps the listening TCP port open, so that
17737 additional connections are possible. However, if you start @code{gdbserver}
17738 with the @option{--once} option, it will stop listening for any further
17739 connection attempts after connecting to the first @value{GDBN} session. This
17740 means no further connections to @code{gdbserver} will be possible after the
17741 first one. It also means @code{gdbserver} will terminate after the first
17742 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17743 connections and even in the @kbd{target extended-remote} mode. The
17744 @option{--once} option allows reusing the same port number for connecting to
17745 multiple instances of @code{gdbserver} running on the same host, since each
17746 instance closes its port after the first connection.
17748 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17750 @cindex @option{--debug}, @code{gdbserver} option
17751 The @option{--debug} option tells @code{gdbserver} to display extra
17752 status information about the debugging process.
17753 @cindex @option{--remote-debug}, @code{gdbserver} option
17754 The @option{--remote-debug} option tells @code{gdbserver} to display
17755 remote protocol debug output. These options are intended for
17756 @code{gdbserver} development and for bug reports to the developers.
17758 @cindex @option{--wrapper}, @code{gdbserver} option
17759 The @option{--wrapper} option specifies a wrapper to launch programs
17760 for debugging. The option should be followed by the name of the
17761 wrapper, then any command-line arguments to pass to the wrapper, then
17762 @kbd{--} indicating the end of the wrapper arguments.
17764 @code{gdbserver} runs the specified wrapper program with a combined
17765 command line including the wrapper arguments, then the name of the
17766 program to debug, then any arguments to the program. The wrapper
17767 runs until it executes your program, and then @value{GDBN} gains control.
17769 You can use any program that eventually calls @code{execve} with
17770 its arguments as a wrapper. Several standard Unix utilities do
17771 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17772 with @code{exec "$@@"} will also work.
17774 For example, you can use @code{env} to pass an environment variable to
17775 the debugged program, without setting the variable in @code{gdbserver}'s
17779 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17782 @subsection Connecting to @code{gdbserver}
17784 Run @value{GDBN} on the host system.
17786 First make sure you have the necessary symbol files. Load symbols for
17787 your application using the @code{file} command before you connect. Use
17788 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17789 was compiled with the correct sysroot using @code{--with-sysroot}).
17791 The symbol file and target libraries must exactly match the executable
17792 and libraries on the target, with one exception: the files on the host
17793 system should not be stripped, even if the files on the target system
17794 are. Mismatched or missing files will lead to confusing results
17795 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17796 files may also prevent @code{gdbserver} from debugging multi-threaded
17799 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17800 For TCP connections, you must start up @code{gdbserver} prior to using
17801 the @code{target remote} command. Otherwise you may get an error whose
17802 text depends on the host system, but which usually looks something like
17803 @samp{Connection refused}. Don't use the @code{load}
17804 command in @value{GDBN} when using @code{gdbserver}, since the program is
17805 already on the target.
17807 @subsection Monitor Commands for @code{gdbserver}
17808 @cindex monitor commands, for @code{gdbserver}
17809 @anchor{Monitor Commands for gdbserver}
17811 During a @value{GDBN} session using @code{gdbserver}, you can use the
17812 @code{monitor} command to send special requests to @code{gdbserver}.
17813 Here are the available commands.
17817 List the available monitor commands.
17819 @item monitor set debug 0
17820 @itemx monitor set debug 1
17821 Disable or enable general debugging messages.
17823 @item monitor set remote-debug 0
17824 @itemx monitor set remote-debug 1
17825 Disable or enable specific debugging messages associated with the remote
17826 protocol (@pxref{Remote Protocol}).
17828 @item monitor set libthread-db-search-path [PATH]
17829 @cindex gdbserver, search path for @code{libthread_db}
17830 When this command is issued, @var{path} is a colon-separated list of
17831 directories to search for @code{libthread_db} (@pxref{Threads,,set
17832 libthread-db-search-path}). If you omit @var{path},
17833 @samp{libthread-db-search-path} will be reset to its default value.
17835 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
17836 not supported in @code{gdbserver}.
17839 Tell gdbserver to exit immediately. This command should be followed by
17840 @code{disconnect} to close the debugging session. @code{gdbserver} will
17841 detach from any attached processes and kill any processes it created.
17842 Use @code{monitor exit} to terminate @code{gdbserver} at the end
17843 of a multi-process mode debug session.
17847 @subsection Tracepoints support in @code{gdbserver}
17848 @cindex tracepoints support in @code{gdbserver}
17850 On some targets, @code{gdbserver} supports tracepoints, fast
17851 tracepoints and static tracepoints.
17853 For fast or static tracepoints to work, a special library called the
17854 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
17855 This library is built and distributed as an integral part of
17856 @code{gdbserver}. In addition, support for static tracepoints
17857 requires building the in-process agent library with static tracepoints
17858 support. At present, the UST (LTTng Userspace Tracer,
17859 @url{http://lttng.org/ust}) tracing engine is supported. This support
17860 is automatically available if UST development headers are found in the
17861 standard include path when @code{gdbserver} is built, or if
17862 @code{gdbserver} was explicitly configured using @option{--with-ust}
17863 to point at such headers. You can explicitly disable the support
17864 using @option{--with-ust=no}.
17866 There are several ways to load the in-process agent in your program:
17869 @item Specifying it as dependency at link time
17871 You can link your program dynamically with the in-process agent
17872 library. On most systems, this is accomplished by adding
17873 @code{-linproctrace} to the link command.
17875 @item Using the system's preloading mechanisms
17877 You can force loading the in-process agent at startup time by using
17878 your system's support for preloading shared libraries. Many Unixes
17879 support the concept of preloading user defined libraries. In most
17880 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
17881 in the environment. See also the description of @code{gdbserver}'s
17882 @option{--wrapper} command line option.
17884 @item Using @value{GDBN} to force loading the agent at run time
17886 On some systems, you can force the inferior to load a shared library,
17887 by calling a dynamic loader function in the inferior that takes care
17888 of dynamically looking up and loading a shared library. On most Unix
17889 systems, the function is @code{dlopen}. You'll use the @code{call}
17890 command for that. For example:
17893 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
17896 Note that on most Unix systems, for the @code{dlopen} function to be
17897 available, the program needs to be linked with @code{-ldl}.
17900 On systems that have a userspace dynamic loader, like most Unix
17901 systems, when you connect to @code{gdbserver} using @code{target
17902 remote}, you'll find that the program is stopped at the dynamic
17903 loader's entry point, and no shared library has been loaded in the
17904 program's address space yet, including the in-process agent. In that
17905 case, before being able to use any of the fast or static tracepoints
17906 features, you need to let the loader run and load the shared
17907 libraries. The simplest way to do that is to run the program to the
17908 main procedure. E.g., if debugging a C or C@t{++} program, start
17909 @code{gdbserver} like so:
17912 $ gdbserver :9999 myprogram
17915 Start GDB and connect to @code{gdbserver} like so, and run to main:
17919 (@value{GDBP}) target remote myhost:9999
17920 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
17921 (@value{GDBP}) b main
17922 (@value{GDBP}) continue
17925 The in-process tracing agent library should now be loaded into the
17926 process; you can confirm it with the @code{info sharedlibrary}
17927 command, which will list @file{libinproctrace.so} as loaded in the
17928 process. You are now ready to install fast tracepoints, list static
17929 tracepoint markers, probe static tracepoints markers, and start
17932 @node Remote Configuration
17933 @section Remote Configuration
17936 @kindex show remote
17937 This section documents the configuration options available when
17938 debugging remote programs. For the options related to the File I/O
17939 extensions of the remote protocol, see @ref{system,
17940 system-call-allowed}.
17943 @item set remoteaddresssize @var{bits}
17944 @cindex address size for remote targets
17945 @cindex bits in remote address
17946 Set the maximum size of address in a memory packet to the specified
17947 number of bits. @value{GDBN} will mask off the address bits above
17948 that number, when it passes addresses to the remote target. The
17949 default value is the number of bits in the target's address.
17951 @item show remoteaddresssize
17952 Show the current value of remote address size in bits.
17954 @item set remotebaud @var{n}
17955 @cindex baud rate for remote targets
17956 Set the baud rate for the remote serial I/O to @var{n} baud. The
17957 value is used to set the speed of the serial port used for debugging
17960 @item show remotebaud
17961 Show the current speed of the remote connection.
17963 @item set remotebreak
17964 @cindex interrupt remote programs
17965 @cindex BREAK signal instead of Ctrl-C
17966 @anchor{set remotebreak}
17967 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
17968 when you type @kbd{Ctrl-c} to interrupt the program running
17969 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
17970 character instead. The default is off, since most remote systems
17971 expect to see @samp{Ctrl-C} as the interrupt signal.
17973 @item show remotebreak
17974 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
17975 interrupt the remote program.
17977 @item set remoteflow on
17978 @itemx set remoteflow off
17979 @kindex set remoteflow
17980 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
17981 on the serial port used to communicate to the remote target.
17983 @item show remoteflow
17984 @kindex show remoteflow
17985 Show the current setting of hardware flow control.
17987 @item set remotelogbase @var{base}
17988 Set the base (a.k.a.@: radix) of logging serial protocol
17989 communications to @var{base}. Supported values of @var{base} are:
17990 @code{ascii}, @code{octal}, and @code{hex}. The default is
17993 @item show remotelogbase
17994 Show the current setting of the radix for logging remote serial
17997 @item set remotelogfile @var{file}
17998 @cindex record serial communications on file
17999 Record remote serial communications on the named @var{file}. The
18000 default is not to record at all.
18002 @item show remotelogfile.
18003 Show the current setting of the file name on which to record the
18004 serial communications.
18006 @item set remotetimeout @var{num}
18007 @cindex timeout for serial communications
18008 @cindex remote timeout
18009 Set the timeout limit to wait for the remote target to respond to
18010 @var{num} seconds. The default is 2 seconds.
18012 @item show remotetimeout
18013 Show the current number of seconds to wait for the remote target
18016 @cindex limit hardware breakpoints and watchpoints
18017 @cindex remote target, limit break- and watchpoints
18018 @anchor{set remote hardware-watchpoint-limit}
18019 @anchor{set remote hardware-breakpoint-limit}
18020 @item set remote hardware-watchpoint-limit @var{limit}
18021 @itemx set remote hardware-breakpoint-limit @var{limit}
18022 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18023 watchpoints. A limit of -1, the default, is treated as unlimited.
18025 @cindex limit hardware watchpoints length
18026 @cindex remote target, limit watchpoints length
18027 @anchor{set remote hardware-watchpoint-length-limit}
18028 @item set remote hardware-watchpoint-length-limit @var{limit}
18029 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18030 a remote hardware watchpoint. A limit of -1, the default, is treated
18033 @item show remote hardware-watchpoint-length-limit
18034 Show the current limit (in bytes) of the maximum length of
18035 a remote hardware watchpoint.
18037 @item set remote exec-file @var{filename}
18038 @itemx show remote exec-file
18039 @anchor{set remote exec-file}
18040 @cindex executable file, for remote target
18041 Select the file used for @code{run} with @code{target
18042 extended-remote}. This should be set to a filename valid on the
18043 target system. If it is not set, the target will use a default
18044 filename (e.g.@: the last program run).
18046 @item set remote interrupt-sequence
18047 @cindex interrupt remote programs
18048 @cindex select Ctrl-C, BREAK or BREAK-g
18049 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18050 @samp{BREAK-g} as the
18051 sequence to the remote target in order to interrupt the execution.
18052 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18053 is high level of serial line for some certain time.
18054 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18055 It is @code{BREAK} signal followed by character @code{g}.
18057 @item show interrupt-sequence
18058 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18059 is sent by @value{GDBN} to interrupt the remote program.
18060 @code{BREAK-g} is BREAK signal followed by @code{g} and
18061 also known as Magic SysRq g.
18063 @item set remote interrupt-on-connect
18064 @cindex send interrupt-sequence on start
18065 Specify whether interrupt-sequence is sent to remote target when
18066 @value{GDBN} connects to it. This is mostly needed when you debug
18067 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18068 which is known as Magic SysRq g in order to connect @value{GDBN}.
18070 @item show interrupt-on-connect
18071 Show whether interrupt-sequence is sent
18072 to remote target when @value{GDBN} connects to it.
18076 @item set tcp auto-retry on
18077 @cindex auto-retry, for remote TCP target
18078 Enable auto-retry for remote TCP connections. This is useful if the remote
18079 debugging agent is launched in parallel with @value{GDBN}; there is a race
18080 condition because the agent may not become ready to accept the connection
18081 before @value{GDBN} attempts to connect. When auto-retry is
18082 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18083 to establish the connection using the timeout specified by
18084 @code{set tcp connect-timeout}.
18086 @item set tcp auto-retry off
18087 Do not auto-retry failed TCP connections.
18089 @item show tcp auto-retry
18090 Show the current auto-retry setting.
18092 @item set tcp connect-timeout @var{seconds}
18093 @cindex connection timeout, for remote TCP target
18094 @cindex timeout, for remote target connection
18095 Set the timeout for establishing a TCP connection to the remote target to
18096 @var{seconds}. The timeout affects both polling to retry failed connections
18097 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18098 that are merely slow to complete, and represents an approximate cumulative
18101 @item show tcp connect-timeout
18102 Show the current connection timeout setting.
18105 @cindex remote packets, enabling and disabling
18106 The @value{GDBN} remote protocol autodetects the packets supported by
18107 your debugging stub. If you need to override the autodetection, you
18108 can use these commands to enable or disable individual packets. Each
18109 packet can be set to @samp{on} (the remote target supports this
18110 packet), @samp{off} (the remote target does not support this packet),
18111 or @samp{auto} (detect remote target support for this packet). They
18112 all default to @samp{auto}. For more information about each packet,
18113 see @ref{Remote Protocol}.
18115 During normal use, you should not have to use any of these commands.
18116 If you do, that may be a bug in your remote debugging stub, or a bug
18117 in @value{GDBN}. You may want to report the problem to the
18118 @value{GDBN} developers.
18120 For each packet @var{name}, the command to enable or disable the
18121 packet is @code{set remote @var{name}-packet}. The available settings
18124 @multitable @columnfractions 0.28 0.32 0.25
18127 @tab Related Features
18129 @item @code{fetch-register}
18131 @tab @code{info registers}
18133 @item @code{set-register}
18137 @item @code{binary-download}
18139 @tab @code{load}, @code{set}
18141 @item @code{read-aux-vector}
18142 @tab @code{qXfer:auxv:read}
18143 @tab @code{info auxv}
18145 @item @code{symbol-lookup}
18146 @tab @code{qSymbol}
18147 @tab Detecting multiple threads
18149 @item @code{attach}
18150 @tab @code{vAttach}
18153 @item @code{verbose-resume}
18155 @tab Stepping or resuming multiple threads
18161 @item @code{software-breakpoint}
18165 @item @code{hardware-breakpoint}
18169 @item @code{write-watchpoint}
18173 @item @code{read-watchpoint}
18177 @item @code{access-watchpoint}
18181 @item @code{target-features}
18182 @tab @code{qXfer:features:read}
18183 @tab @code{set architecture}
18185 @item @code{library-info}
18186 @tab @code{qXfer:libraries:read}
18187 @tab @code{info sharedlibrary}
18189 @item @code{memory-map}
18190 @tab @code{qXfer:memory-map:read}
18191 @tab @code{info mem}
18193 @item @code{read-sdata-object}
18194 @tab @code{qXfer:sdata:read}
18195 @tab @code{print $_sdata}
18197 @item @code{read-spu-object}
18198 @tab @code{qXfer:spu:read}
18199 @tab @code{info spu}
18201 @item @code{write-spu-object}
18202 @tab @code{qXfer:spu:write}
18203 @tab @code{info spu}
18205 @item @code{read-siginfo-object}
18206 @tab @code{qXfer:siginfo:read}
18207 @tab @code{print $_siginfo}
18209 @item @code{write-siginfo-object}
18210 @tab @code{qXfer:siginfo:write}
18211 @tab @code{set $_siginfo}
18213 @item @code{threads}
18214 @tab @code{qXfer:threads:read}
18215 @tab @code{info threads}
18217 @item @code{get-thread-local-@*storage-address}
18218 @tab @code{qGetTLSAddr}
18219 @tab Displaying @code{__thread} variables
18221 @item @code{get-thread-information-block-address}
18222 @tab @code{qGetTIBAddr}
18223 @tab Display MS-Windows Thread Information Block.
18225 @item @code{search-memory}
18226 @tab @code{qSearch:memory}
18229 @item @code{supported-packets}
18230 @tab @code{qSupported}
18231 @tab Remote communications parameters
18233 @item @code{pass-signals}
18234 @tab @code{QPassSignals}
18235 @tab @code{handle @var{signal}}
18237 @item @code{program-signals}
18238 @tab @code{QProgramSignals}
18239 @tab @code{handle @var{signal}}
18241 @item @code{hostio-close-packet}
18242 @tab @code{vFile:close}
18243 @tab @code{remote get}, @code{remote put}
18245 @item @code{hostio-open-packet}
18246 @tab @code{vFile:open}
18247 @tab @code{remote get}, @code{remote put}
18249 @item @code{hostio-pread-packet}
18250 @tab @code{vFile:pread}
18251 @tab @code{remote get}, @code{remote put}
18253 @item @code{hostio-pwrite-packet}
18254 @tab @code{vFile:pwrite}
18255 @tab @code{remote get}, @code{remote put}
18257 @item @code{hostio-unlink-packet}
18258 @tab @code{vFile:unlink}
18259 @tab @code{remote delete}
18261 @item @code{hostio-readlink-packet}
18262 @tab @code{vFile:readlink}
18265 @item @code{noack-packet}
18266 @tab @code{QStartNoAckMode}
18267 @tab Packet acknowledgment
18269 @item @code{osdata}
18270 @tab @code{qXfer:osdata:read}
18271 @tab @code{info os}
18273 @item @code{query-attached}
18274 @tab @code{qAttached}
18275 @tab Querying remote process attach state.
18277 @item @code{traceframe-info}
18278 @tab @code{qXfer:traceframe-info:read}
18279 @tab Traceframe info
18281 @item @code{install-in-trace}
18282 @tab @code{InstallInTrace}
18283 @tab Install tracepoint in tracing
18285 @item @code{disable-randomization}
18286 @tab @code{QDisableRandomization}
18287 @tab @code{set disable-randomization}
18289 @item @code{conditional-breakpoints-packet}
18290 @tab @code{Z0 and Z1}
18291 @tab @code{Support for target-side breakpoint condition evaluation}
18295 @section Implementing a Remote Stub
18297 @cindex debugging stub, example
18298 @cindex remote stub, example
18299 @cindex stub example, remote debugging
18300 The stub files provided with @value{GDBN} implement the target side of the
18301 communication protocol, and the @value{GDBN} side is implemented in the
18302 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18303 these subroutines to communicate, and ignore the details. (If you're
18304 implementing your own stub file, you can still ignore the details: start
18305 with one of the existing stub files. @file{sparc-stub.c} is the best
18306 organized, and therefore the easiest to read.)
18308 @cindex remote serial debugging, overview
18309 To debug a program running on another machine (the debugging
18310 @dfn{target} machine), you must first arrange for all the usual
18311 prerequisites for the program to run by itself. For example, for a C
18316 A startup routine to set up the C runtime environment; these usually
18317 have a name like @file{crt0}. The startup routine may be supplied by
18318 your hardware supplier, or you may have to write your own.
18321 A C subroutine library to support your program's
18322 subroutine calls, notably managing input and output.
18325 A way of getting your program to the other machine---for example, a
18326 download program. These are often supplied by the hardware
18327 manufacturer, but you may have to write your own from hardware
18331 The next step is to arrange for your program to use a serial port to
18332 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18333 machine). In general terms, the scheme looks like this:
18337 @value{GDBN} already understands how to use this protocol; when everything
18338 else is set up, you can simply use the @samp{target remote} command
18339 (@pxref{Targets,,Specifying a Debugging Target}).
18341 @item On the target,
18342 you must link with your program a few special-purpose subroutines that
18343 implement the @value{GDBN} remote serial protocol. The file containing these
18344 subroutines is called a @dfn{debugging stub}.
18346 On certain remote targets, you can use an auxiliary program
18347 @code{gdbserver} instead of linking a stub into your program.
18348 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18351 The debugging stub is specific to the architecture of the remote
18352 machine; for example, use @file{sparc-stub.c} to debug programs on
18355 @cindex remote serial stub list
18356 These working remote stubs are distributed with @value{GDBN}:
18361 @cindex @file{i386-stub.c}
18364 For Intel 386 and compatible architectures.
18367 @cindex @file{m68k-stub.c}
18368 @cindex Motorola 680x0
18370 For Motorola 680x0 architectures.
18373 @cindex @file{sh-stub.c}
18376 For Renesas SH architectures.
18379 @cindex @file{sparc-stub.c}
18381 For @sc{sparc} architectures.
18383 @item sparcl-stub.c
18384 @cindex @file{sparcl-stub.c}
18387 For Fujitsu @sc{sparclite} architectures.
18391 The @file{README} file in the @value{GDBN} distribution may list other
18392 recently added stubs.
18395 * Stub Contents:: What the stub can do for you
18396 * Bootstrapping:: What you must do for the stub
18397 * Debug Session:: Putting it all together
18400 @node Stub Contents
18401 @subsection What the Stub Can Do for You
18403 @cindex remote serial stub
18404 The debugging stub for your architecture supplies these three
18408 @item set_debug_traps
18409 @findex set_debug_traps
18410 @cindex remote serial stub, initialization
18411 This routine arranges for @code{handle_exception} to run when your
18412 program stops. You must call this subroutine explicitly in your
18413 program's startup code.
18415 @item handle_exception
18416 @findex handle_exception
18417 @cindex remote serial stub, main routine
18418 This is the central workhorse, but your program never calls it
18419 explicitly---the setup code arranges for @code{handle_exception} to
18420 run when a trap is triggered.
18422 @code{handle_exception} takes control when your program stops during
18423 execution (for example, on a breakpoint), and mediates communications
18424 with @value{GDBN} on the host machine. This is where the communications
18425 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18426 representative on the target machine. It begins by sending summary
18427 information on the state of your program, then continues to execute,
18428 retrieving and transmitting any information @value{GDBN} needs, until you
18429 execute a @value{GDBN} command that makes your program resume; at that point,
18430 @code{handle_exception} returns control to your own code on the target
18434 @cindex @code{breakpoint} subroutine, remote
18435 Use this auxiliary subroutine to make your program contain a
18436 breakpoint. Depending on the particular situation, this may be the only
18437 way for @value{GDBN} to get control. For instance, if your target
18438 machine has some sort of interrupt button, you won't need to call this;
18439 pressing the interrupt button transfers control to
18440 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18441 simply receiving characters on the serial port may also trigger a trap;
18442 again, in that situation, you don't need to call @code{breakpoint} from
18443 your own program---simply running @samp{target remote} from the host
18444 @value{GDBN} session gets control.
18446 Call @code{breakpoint} if none of these is true, or if you simply want
18447 to make certain your program stops at a predetermined point for the
18448 start of your debugging session.
18451 @node Bootstrapping
18452 @subsection What You Must Do for the Stub
18454 @cindex remote stub, support routines
18455 The debugging stubs that come with @value{GDBN} are set up for a particular
18456 chip architecture, but they have no information about the rest of your
18457 debugging target machine.
18459 First of all you need to tell the stub how to communicate with the
18463 @item int getDebugChar()
18464 @findex getDebugChar
18465 Write this subroutine to read a single character from the serial port.
18466 It may be identical to @code{getchar} for your target system; a
18467 different name is used to allow you to distinguish the two if you wish.
18469 @item void putDebugChar(int)
18470 @findex putDebugChar
18471 Write this subroutine to write a single character to the serial port.
18472 It may be identical to @code{putchar} for your target system; a
18473 different name is used to allow you to distinguish the two if you wish.
18476 @cindex control C, and remote debugging
18477 @cindex interrupting remote targets
18478 If you want @value{GDBN} to be able to stop your program while it is
18479 running, you need to use an interrupt-driven serial driver, and arrange
18480 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18481 character). That is the character which @value{GDBN} uses to tell the
18482 remote system to stop.
18484 Getting the debugging target to return the proper status to @value{GDBN}
18485 probably requires changes to the standard stub; one quick and dirty way
18486 is to just execute a breakpoint instruction (the ``dirty'' part is that
18487 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18489 Other routines you need to supply are:
18492 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18493 @findex exceptionHandler
18494 Write this function to install @var{exception_address} in the exception
18495 handling tables. You need to do this because the stub does not have any
18496 way of knowing what the exception handling tables on your target system
18497 are like (for example, the processor's table might be in @sc{rom},
18498 containing entries which point to a table in @sc{ram}).
18499 @var{exception_number} is the exception number which should be changed;
18500 its meaning is architecture-dependent (for example, different numbers
18501 might represent divide by zero, misaligned access, etc). When this
18502 exception occurs, control should be transferred directly to
18503 @var{exception_address}, and the processor state (stack, registers,
18504 and so on) should be just as it is when a processor exception occurs. So if
18505 you want to use a jump instruction to reach @var{exception_address}, it
18506 should be a simple jump, not a jump to subroutine.
18508 For the 386, @var{exception_address} should be installed as an interrupt
18509 gate so that interrupts are masked while the handler runs. The gate
18510 should be at privilege level 0 (the most privileged level). The
18511 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18512 help from @code{exceptionHandler}.
18514 @item void flush_i_cache()
18515 @findex flush_i_cache
18516 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18517 instruction cache, if any, on your target machine. If there is no
18518 instruction cache, this subroutine may be a no-op.
18520 On target machines that have instruction caches, @value{GDBN} requires this
18521 function to make certain that the state of your program is stable.
18525 You must also make sure this library routine is available:
18528 @item void *memset(void *, int, int)
18530 This is the standard library function @code{memset} that sets an area of
18531 memory to a known value. If you have one of the free versions of
18532 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18533 either obtain it from your hardware manufacturer, or write your own.
18536 If you do not use the GNU C compiler, you may need other standard
18537 library subroutines as well; this varies from one stub to another,
18538 but in general the stubs are likely to use any of the common library
18539 subroutines which @code{@value{NGCC}} generates as inline code.
18542 @node Debug Session
18543 @subsection Putting it All Together
18545 @cindex remote serial debugging summary
18546 In summary, when your program is ready to debug, you must follow these
18551 Make sure you have defined the supporting low-level routines
18552 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18554 @code{getDebugChar}, @code{putDebugChar},
18555 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18559 Insert these lines in your program's startup code, before the main
18560 procedure is called:
18567 On some machines, when a breakpoint trap is raised, the hardware
18568 automatically makes the PC point to the instruction after the
18569 breakpoint. If your machine doesn't do that, you may need to adjust
18570 @code{handle_exception} to arrange for it to return to the instruction
18571 after the breakpoint on this first invocation, so that your program
18572 doesn't keep hitting the initial breakpoint instead of making
18576 For the 680x0 stub only, you need to provide a variable called
18577 @code{exceptionHook}. Normally you just use:
18580 void (*exceptionHook)() = 0;
18584 but if before calling @code{set_debug_traps}, you set it to point to a
18585 function in your program, that function is called when
18586 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18587 error). The function indicated by @code{exceptionHook} is called with
18588 one parameter: an @code{int} which is the exception number.
18591 Compile and link together: your program, the @value{GDBN} debugging stub for
18592 your target architecture, and the supporting subroutines.
18595 Make sure you have a serial connection between your target machine and
18596 the @value{GDBN} host, and identify the serial port on the host.
18599 @c The "remote" target now provides a `load' command, so we should
18600 @c document that. FIXME.
18601 Download your program to your target machine (or get it there by
18602 whatever means the manufacturer provides), and start it.
18605 Start @value{GDBN} on the host, and connect to the target
18606 (@pxref{Connecting,,Connecting to a Remote Target}).
18610 @node Configurations
18611 @chapter Configuration-Specific Information
18613 While nearly all @value{GDBN} commands are available for all native and
18614 cross versions of the debugger, there are some exceptions. This chapter
18615 describes things that are only available in certain configurations.
18617 There are three major categories of configurations: native
18618 configurations, where the host and target are the same, embedded
18619 operating system configurations, which are usually the same for several
18620 different processor architectures, and bare embedded processors, which
18621 are quite different from each other.
18626 * Embedded Processors::
18633 This section describes details specific to particular native
18638 * BSD libkvm Interface:: Debugging BSD kernel memory images
18639 * SVR4 Process Information:: SVR4 process information
18640 * DJGPP Native:: Features specific to the DJGPP port
18641 * Cygwin Native:: Features specific to the Cygwin port
18642 * Hurd Native:: Features specific to @sc{gnu} Hurd
18643 * Darwin:: Features specific to Darwin
18649 On HP-UX systems, if you refer to a function or variable name that
18650 begins with a dollar sign, @value{GDBN} searches for a user or system
18651 name first, before it searches for a convenience variable.
18654 @node BSD libkvm Interface
18655 @subsection BSD libkvm Interface
18658 @cindex kernel memory image
18659 @cindex kernel crash dump
18661 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18662 interface that provides a uniform interface for accessing kernel virtual
18663 memory images, including live systems and crash dumps. @value{GDBN}
18664 uses this interface to allow you to debug live kernels and kernel crash
18665 dumps on many native BSD configurations. This is implemented as a
18666 special @code{kvm} debugging target. For debugging a live system, load
18667 the currently running kernel into @value{GDBN} and connect to the
18671 (@value{GDBP}) @b{target kvm}
18674 For debugging crash dumps, provide the file name of the crash dump as an
18678 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18681 Once connected to the @code{kvm} target, the following commands are
18687 Set current context from the @dfn{Process Control Block} (PCB) address.
18690 Set current context from proc address. This command isn't available on
18691 modern FreeBSD systems.
18694 @node SVR4 Process Information
18695 @subsection SVR4 Process Information
18697 @cindex examine process image
18698 @cindex process info via @file{/proc}
18700 Many versions of SVR4 and compatible systems provide a facility called
18701 @samp{/proc} that can be used to examine the image of a running
18702 process using file-system subroutines.
18704 If @value{GDBN} is configured for an operating system with this
18705 facility, the command @code{info proc} is available to report
18706 information about the process running your program, or about any
18707 process running on your system. This includes, as of this writing,
18708 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18709 not HP-UX, for example.
18711 This command may also work on core files that were created on a system
18712 that has the @samp{/proc} facility.
18718 @itemx info proc @var{process-id}
18719 Summarize available information about any running process. If a
18720 process ID is specified by @var{process-id}, display information about
18721 that process; otherwise display information about the program being
18722 debugged. The summary includes the debugged process ID, the command
18723 line used to invoke it, its current working directory, and its
18724 executable file's absolute file name.
18726 On some systems, @var{process-id} can be of the form
18727 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18728 within a process. If the optional @var{pid} part is missing, it means
18729 a thread from the process being debugged (the leading @samp{/} still
18730 needs to be present, or else @value{GDBN} will interpret the number as
18731 a process ID rather than a thread ID).
18733 @item info proc cmdline
18734 @cindex info proc cmdline
18735 Show the original command line of the process. This command is
18736 specific to @sc{gnu}/Linux.
18738 @item info proc cwd
18739 @cindex info proc cwd
18740 Show the current working directory of the process. This command is
18741 specific to @sc{gnu}/Linux.
18743 @item info proc exe
18744 @cindex info proc exe
18745 Show the name of executable of the process. This command is specific
18748 @item info proc mappings
18749 @cindex memory address space mappings
18750 Report the memory address space ranges accessible in the program, with
18751 information on whether the process has read, write, or execute access
18752 rights to each range. On @sc{gnu}/Linux systems, each memory range
18753 includes the object file which is mapped to that range, instead of the
18754 memory access rights to that range.
18756 @item info proc stat
18757 @itemx info proc status
18758 @cindex process detailed status information
18759 These subcommands are specific to @sc{gnu}/Linux systems. They show
18760 the process-related information, including the user ID and group ID;
18761 how many threads are there in the process; its virtual memory usage;
18762 the signals that are pending, blocked, and ignored; its TTY; its
18763 consumption of system and user time; its stack size; its @samp{nice}
18764 value; etc. For more information, see the @samp{proc} man page
18765 (type @kbd{man 5 proc} from your shell prompt).
18767 @item info proc all
18768 Show all the information about the process described under all of the
18769 above @code{info proc} subcommands.
18772 @comment These sub-options of 'info proc' were not included when
18773 @comment procfs.c was re-written. Keep their descriptions around
18774 @comment against the day when someone finds the time to put them back in.
18775 @kindex info proc times
18776 @item info proc times
18777 Starting time, user CPU time, and system CPU time for your program and
18780 @kindex info proc id
18782 Report on the process IDs related to your program: its own process ID,
18783 the ID of its parent, the process group ID, and the session ID.
18786 @item set procfs-trace
18787 @kindex set procfs-trace
18788 @cindex @code{procfs} API calls
18789 This command enables and disables tracing of @code{procfs} API calls.
18791 @item show procfs-trace
18792 @kindex show procfs-trace
18793 Show the current state of @code{procfs} API call tracing.
18795 @item set procfs-file @var{file}
18796 @kindex set procfs-file
18797 Tell @value{GDBN} to write @code{procfs} API trace to the named
18798 @var{file}. @value{GDBN} appends the trace info to the previous
18799 contents of the file. The default is to display the trace on the
18802 @item show procfs-file
18803 @kindex show procfs-file
18804 Show the file to which @code{procfs} API trace is written.
18806 @item proc-trace-entry
18807 @itemx proc-trace-exit
18808 @itemx proc-untrace-entry
18809 @itemx proc-untrace-exit
18810 @kindex proc-trace-entry
18811 @kindex proc-trace-exit
18812 @kindex proc-untrace-entry
18813 @kindex proc-untrace-exit
18814 These commands enable and disable tracing of entries into and exits
18815 from the @code{syscall} interface.
18818 @kindex info pidlist
18819 @cindex process list, QNX Neutrino
18820 For QNX Neutrino only, this command displays the list of all the
18821 processes and all the threads within each process.
18824 @kindex info meminfo
18825 @cindex mapinfo list, QNX Neutrino
18826 For QNX Neutrino only, this command displays the list of all mapinfos.
18830 @subsection Features for Debugging @sc{djgpp} Programs
18831 @cindex @sc{djgpp} debugging
18832 @cindex native @sc{djgpp} debugging
18833 @cindex MS-DOS-specific commands
18836 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
18837 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
18838 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
18839 top of real-mode DOS systems and their emulations.
18841 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
18842 defines a few commands specific to the @sc{djgpp} port. This
18843 subsection describes those commands.
18848 This is a prefix of @sc{djgpp}-specific commands which print
18849 information about the target system and important OS structures.
18852 @cindex MS-DOS system info
18853 @cindex free memory information (MS-DOS)
18854 @item info dos sysinfo
18855 This command displays assorted information about the underlying
18856 platform: the CPU type and features, the OS version and flavor, the
18857 DPMI version, and the available conventional and DPMI memory.
18862 @cindex segment descriptor tables
18863 @cindex descriptor tables display
18865 @itemx info dos ldt
18866 @itemx info dos idt
18867 These 3 commands display entries from, respectively, Global, Local,
18868 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
18869 tables are data structures which store a descriptor for each segment
18870 that is currently in use. The segment's selector is an index into a
18871 descriptor table; the table entry for that index holds the
18872 descriptor's base address and limit, and its attributes and access
18875 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
18876 segment (used for both data and the stack), and a DOS segment (which
18877 allows access to DOS/BIOS data structures and absolute addresses in
18878 conventional memory). However, the DPMI host will usually define
18879 additional segments in order to support the DPMI environment.
18881 @cindex garbled pointers
18882 These commands allow to display entries from the descriptor tables.
18883 Without an argument, all entries from the specified table are
18884 displayed. An argument, which should be an integer expression, means
18885 display a single entry whose index is given by the argument. For
18886 example, here's a convenient way to display information about the
18887 debugged program's data segment:
18890 @exdent @code{(@value{GDBP}) info dos ldt $ds}
18891 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
18895 This comes in handy when you want to see whether a pointer is outside
18896 the data segment's limit (i.e.@: @dfn{garbled}).
18898 @cindex page tables display (MS-DOS)
18900 @itemx info dos pte
18901 These two commands display entries from, respectively, the Page
18902 Directory and the Page Tables. Page Directories and Page Tables are
18903 data structures which control how virtual memory addresses are mapped
18904 into physical addresses. A Page Table includes an entry for every
18905 page of memory that is mapped into the program's address space; there
18906 may be several Page Tables, each one holding up to 4096 entries. A
18907 Page Directory has up to 4096 entries, one each for every Page Table
18908 that is currently in use.
18910 Without an argument, @kbd{info dos pde} displays the entire Page
18911 Directory, and @kbd{info dos pte} displays all the entries in all of
18912 the Page Tables. An argument, an integer expression, given to the
18913 @kbd{info dos pde} command means display only that entry from the Page
18914 Directory table. An argument given to the @kbd{info dos pte} command
18915 means display entries from a single Page Table, the one pointed to by
18916 the specified entry in the Page Directory.
18918 @cindex direct memory access (DMA) on MS-DOS
18919 These commands are useful when your program uses @dfn{DMA} (Direct
18920 Memory Access), which needs physical addresses to program the DMA
18923 These commands are supported only with some DPMI servers.
18925 @cindex physical address from linear address
18926 @item info dos address-pte @var{addr}
18927 This command displays the Page Table entry for a specified linear
18928 address. The argument @var{addr} is a linear address which should
18929 already have the appropriate segment's base address added to it,
18930 because this command accepts addresses which may belong to @emph{any}
18931 segment. For example, here's how to display the Page Table entry for
18932 the page where a variable @code{i} is stored:
18935 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
18936 @exdent @code{Page Table entry for address 0x11a00d30:}
18937 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
18941 This says that @code{i} is stored at offset @code{0xd30} from the page
18942 whose physical base address is @code{0x02698000}, and shows all the
18943 attributes of that page.
18945 Note that you must cast the addresses of variables to a @code{char *},
18946 since otherwise the value of @code{__djgpp_base_address}, the base
18947 address of all variables and functions in a @sc{djgpp} program, will
18948 be added using the rules of C pointer arithmetics: if @code{i} is
18949 declared an @code{int}, @value{GDBN} will add 4 times the value of
18950 @code{__djgpp_base_address} to the address of @code{i}.
18952 Here's another example, it displays the Page Table entry for the
18956 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
18957 @exdent @code{Page Table entry for address 0x29110:}
18958 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
18962 (The @code{+ 3} offset is because the transfer buffer's address is the
18963 3rd member of the @code{_go32_info_block} structure.) The output
18964 clearly shows that this DPMI server maps the addresses in conventional
18965 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
18966 linear (@code{0x29110}) addresses are identical.
18968 This command is supported only with some DPMI servers.
18971 @cindex DOS serial data link, remote debugging
18972 In addition to native debugging, the DJGPP port supports remote
18973 debugging via a serial data link. The following commands are specific
18974 to remote serial debugging in the DJGPP port of @value{GDBN}.
18977 @kindex set com1base
18978 @kindex set com1irq
18979 @kindex set com2base
18980 @kindex set com2irq
18981 @kindex set com3base
18982 @kindex set com3irq
18983 @kindex set com4base
18984 @kindex set com4irq
18985 @item set com1base @var{addr}
18986 This command sets the base I/O port address of the @file{COM1} serial
18989 @item set com1irq @var{irq}
18990 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
18991 for the @file{COM1} serial port.
18993 There are similar commands @samp{set com2base}, @samp{set com3irq},
18994 etc.@: for setting the port address and the @code{IRQ} lines for the
18997 @kindex show com1base
18998 @kindex show com1irq
18999 @kindex show com2base
19000 @kindex show com2irq
19001 @kindex show com3base
19002 @kindex show com3irq
19003 @kindex show com4base
19004 @kindex show com4irq
19005 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19006 display the current settings of the base address and the @code{IRQ}
19007 lines used by the COM ports.
19010 @kindex info serial
19011 @cindex DOS serial port status
19012 This command prints the status of the 4 DOS serial ports. For each
19013 port, it prints whether it's active or not, its I/O base address and
19014 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19015 counts of various errors encountered so far.
19019 @node Cygwin Native
19020 @subsection Features for Debugging MS Windows PE Executables
19021 @cindex MS Windows debugging
19022 @cindex native Cygwin debugging
19023 @cindex Cygwin-specific commands
19025 @value{GDBN} supports native debugging of MS Windows programs, including
19026 DLLs with and without symbolic debugging information.
19028 @cindex Ctrl-BREAK, MS-Windows
19029 @cindex interrupt debuggee on MS-Windows
19030 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19031 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19032 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19033 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19034 sequence, which can be used to interrupt the debuggee even if it
19037 There are various additional Cygwin-specific commands, described in
19038 this section. Working with DLLs that have no debugging symbols is
19039 described in @ref{Non-debug DLL Symbols}.
19044 This is a prefix of MS Windows-specific commands which print
19045 information about the target system and important OS structures.
19047 @item info w32 selector
19048 This command displays information returned by
19049 the Win32 API @code{GetThreadSelectorEntry} function.
19050 It takes an optional argument that is evaluated to
19051 a long value to give the information about this given selector.
19052 Without argument, this command displays information
19053 about the six segment registers.
19055 @item info w32 thread-information-block
19056 This command displays thread specific information stored in the
19057 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19058 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19062 This is a Cygwin-specific alias of @code{info shared}.
19064 @kindex dll-symbols
19066 This command loads symbols from a dll similarly to
19067 add-sym command but without the need to specify a base address.
19069 @kindex set cygwin-exceptions
19070 @cindex debugging the Cygwin DLL
19071 @cindex Cygwin DLL, debugging
19072 @item set cygwin-exceptions @var{mode}
19073 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19074 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19075 @value{GDBN} will delay recognition of exceptions, and may ignore some
19076 exceptions which seem to be caused by internal Cygwin DLL
19077 ``bookkeeping''. This option is meant primarily for debugging the
19078 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19079 @value{GDBN} users with false @code{SIGSEGV} signals.
19081 @kindex show cygwin-exceptions
19082 @item show cygwin-exceptions
19083 Displays whether @value{GDBN} will break on exceptions that happen
19084 inside the Cygwin DLL itself.
19086 @kindex set new-console
19087 @item set new-console @var{mode}
19088 If @var{mode} is @code{on} the debuggee will
19089 be started in a new console on next start.
19090 If @var{mode} is @code{off}, the debuggee will
19091 be started in the same console as the debugger.
19093 @kindex show new-console
19094 @item show new-console
19095 Displays whether a new console is used
19096 when the debuggee is started.
19098 @kindex set new-group
19099 @item set new-group @var{mode}
19100 This boolean value controls whether the debuggee should
19101 start a new group or stay in the same group as the debugger.
19102 This affects the way the Windows OS handles
19105 @kindex show new-group
19106 @item show new-group
19107 Displays current value of new-group boolean.
19109 @kindex set debugevents
19110 @item set debugevents
19111 This boolean value adds debug output concerning kernel events related
19112 to the debuggee seen by the debugger. This includes events that
19113 signal thread and process creation and exit, DLL loading and
19114 unloading, console interrupts, and debugging messages produced by the
19115 Windows @code{OutputDebugString} API call.
19117 @kindex set debugexec
19118 @item set debugexec
19119 This boolean value adds debug output concerning execute events
19120 (such as resume thread) seen by the debugger.
19122 @kindex set debugexceptions
19123 @item set debugexceptions
19124 This boolean value adds debug output concerning exceptions in the
19125 debuggee seen by the debugger.
19127 @kindex set debugmemory
19128 @item set debugmemory
19129 This boolean value adds debug output concerning debuggee memory reads
19130 and writes by the debugger.
19134 This boolean values specifies whether the debuggee is called
19135 via a shell or directly (default value is on).
19139 Displays if the debuggee will be started with a shell.
19144 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19147 @node Non-debug DLL Symbols
19148 @subsubsection Support for DLLs without Debugging Symbols
19149 @cindex DLLs with no debugging symbols
19150 @cindex Minimal symbols and DLLs
19152 Very often on windows, some of the DLLs that your program relies on do
19153 not include symbolic debugging information (for example,
19154 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19155 symbols in a DLL, it relies on the minimal amount of symbolic
19156 information contained in the DLL's export table. This section
19157 describes working with such symbols, known internally to @value{GDBN} as
19158 ``minimal symbols''.
19160 Note that before the debugged program has started execution, no DLLs
19161 will have been loaded. The easiest way around this problem is simply to
19162 start the program --- either by setting a breakpoint or letting the
19163 program run once to completion. It is also possible to force
19164 @value{GDBN} to load a particular DLL before starting the executable ---
19165 see the shared library information in @ref{Files}, or the
19166 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19167 explicitly loading symbols from a DLL with no debugging information will
19168 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19169 which may adversely affect symbol lookup performance.
19171 @subsubsection DLL Name Prefixes
19173 In keeping with the naming conventions used by the Microsoft debugging
19174 tools, DLL export symbols are made available with a prefix based on the
19175 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19176 also entered into the symbol table, so @code{CreateFileA} is often
19177 sufficient. In some cases there will be name clashes within a program
19178 (particularly if the executable itself includes full debugging symbols)
19179 necessitating the use of the fully qualified name when referring to the
19180 contents of the DLL. Use single-quotes around the name to avoid the
19181 exclamation mark (``!'') being interpreted as a language operator.
19183 Note that the internal name of the DLL may be all upper-case, even
19184 though the file name of the DLL is lower-case, or vice-versa. Since
19185 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19186 some confusion. If in doubt, try the @code{info functions} and
19187 @code{info variables} commands or even @code{maint print msymbols}
19188 (@pxref{Symbols}). Here's an example:
19191 (@value{GDBP}) info function CreateFileA
19192 All functions matching regular expression "CreateFileA":
19194 Non-debugging symbols:
19195 0x77e885f4 CreateFileA
19196 0x77e885f4 KERNEL32!CreateFileA
19200 (@value{GDBP}) info function !
19201 All functions matching regular expression "!":
19203 Non-debugging symbols:
19204 0x6100114c cygwin1!__assert
19205 0x61004034 cygwin1!_dll_crt0@@0
19206 0x61004240 cygwin1!dll_crt0(per_process *)
19210 @subsubsection Working with Minimal Symbols
19212 Symbols extracted from a DLL's export table do not contain very much
19213 type information. All that @value{GDBN} can do is guess whether a symbol
19214 refers to a function or variable depending on the linker section that
19215 contains the symbol. Also note that the actual contents of the memory
19216 contained in a DLL are not available unless the program is running. This
19217 means that you cannot examine the contents of a variable or disassemble
19218 a function within a DLL without a running program.
19220 Variables are generally treated as pointers and dereferenced
19221 automatically. For this reason, it is often necessary to prefix a
19222 variable name with the address-of operator (``&'') and provide explicit
19223 type information in the command. Here's an example of the type of
19227 (@value{GDBP}) print 'cygwin1!__argv'
19232 (@value{GDBP}) x 'cygwin1!__argv'
19233 0x10021610: "\230y\""
19236 And two possible solutions:
19239 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19240 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19244 (@value{GDBP}) x/2x &'cygwin1!__argv'
19245 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19246 (@value{GDBP}) x/x 0x10021608
19247 0x10021608: 0x0022fd98
19248 (@value{GDBP}) x/s 0x0022fd98
19249 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19252 Setting a break point within a DLL is possible even before the program
19253 starts execution. However, under these circumstances, @value{GDBN} can't
19254 examine the initial instructions of the function in order to skip the
19255 function's frame set-up code. You can work around this by using ``*&''
19256 to set the breakpoint at a raw memory address:
19259 (@value{GDBP}) break *&'python22!PyOS_Readline'
19260 Breakpoint 1 at 0x1e04eff0
19263 The author of these extensions is not entirely convinced that setting a
19264 break point within a shared DLL like @file{kernel32.dll} is completely
19268 @subsection Commands Specific to @sc{gnu} Hurd Systems
19269 @cindex @sc{gnu} Hurd debugging
19271 This subsection describes @value{GDBN} commands specific to the
19272 @sc{gnu} Hurd native debugging.
19277 @kindex set signals@r{, Hurd command}
19278 @kindex set sigs@r{, Hurd command}
19279 This command toggles the state of inferior signal interception by
19280 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19281 affected by this command. @code{sigs} is a shorthand alias for
19286 @kindex show signals@r{, Hurd command}
19287 @kindex show sigs@r{, Hurd command}
19288 Show the current state of intercepting inferior's signals.
19290 @item set signal-thread
19291 @itemx set sigthread
19292 @kindex set signal-thread
19293 @kindex set sigthread
19294 This command tells @value{GDBN} which thread is the @code{libc} signal
19295 thread. That thread is run when a signal is delivered to a running
19296 process. @code{set sigthread} is the shorthand alias of @code{set
19299 @item show signal-thread
19300 @itemx show sigthread
19301 @kindex show signal-thread
19302 @kindex show sigthread
19303 These two commands show which thread will run when the inferior is
19304 delivered a signal.
19307 @kindex set stopped@r{, Hurd command}
19308 This commands tells @value{GDBN} that the inferior process is stopped,
19309 as with the @code{SIGSTOP} signal. The stopped process can be
19310 continued by delivering a signal to it.
19313 @kindex show stopped@r{, Hurd command}
19314 This command shows whether @value{GDBN} thinks the debuggee is
19317 @item set exceptions
19318 @kindex set exceptions@r{, Hurd command}
19319 Use this command to turn off trapping of exceptions in the inferior.
19320 When exception trapping is off, neither breakpoints nor
19321 single-stepping will work. To restore the default, set exception
19324 @item show exceptions
19325 @kindex show exceptions@r{, Hurd command}
19326 Show the current state of trapping exceptions in the inferior.
19328 @item set task pause
19329 @kindex set task@r{, Hurd commands}
19330 @cindex task attributes (@sc{gnu} Hurd)
19331 @cindex pause current task (@sc{gnu} Hurd)
19332 This command toggles task suspension when @value{GDBN} has control.
19333 Setting it to on takes effect immediately, and the task is suspended
19334 whenever @value{GDBN} gets control. Setting it to off will take
19335 effect the next time the inferior is continued. If this option is set
19336 to off, you can use @code{set thread default pause on} or @code{set
19337 thread pause on} (see below) to pause individual threads.
19339 @item show task pause
19340 @kindex show task@r{, Hurd commands}
19341 Show the current state of task suspension.
19343 @item set task detach-suspend-count
19344 @cindex task suspend count
19345 @cindex detach from task, @sc{gnu} Hurd
19346 This command sets the suspend count the task will be left with when
19347 @value{GDBN} detaches from it.
19349 @item show task detach-suspend-count
19350 Show the suspend count the task will be left with when detaching.
19352 @item set task exception-port
19353 @itemx set task excp
19354 @cindex task exception port, @sc{gnu} Hurd
19355 This command sets the task exception port to which @value{GDBN} will
19356 forward exceptions. The argument should be the value of the @dfn{send
19357 rights} of the task. @code{set task excp} is a shorthand alias.
19359 @item set noninvasive
19360 @cindex noninvasive task options
19361 This command switches @value{GDBN} to a mode that is the least
19362 invasive as far as interfering with the inferior is concerned. This
19363 is the same as using @code{set task pause}, @code{set exceptions}, and
19364 @code{set signals} to values opposite to the defaults.
19366 @item info send-rights
19367 @itemx info receive-rights
19368 @itemx info port-rights
19369 @itemx info port-sets
19370 @itemx info dead-names
19373 @cindex send rights, @sc{gnu} Hurd
19374 @cindex receive rights, @sc{gnu} Hurd
19375 @cindex port rights, @sc{gnu} Hurd
19376 @cindex port sets, @sc{gnu} Hurd
19377 @cindex dead names, @sc{gnu} Hurd
19378 These commands display information about, respectively, send rights,
19379 receive rights, port rights, port sets, and dead names of a task.
19380 There are also shorthand aliases: @code{info ports} for @code{info
19381 port-rights} and @code{info psets} for @code{info port-sets}.
19383 @item set thread pause
19384 @kindex set thread@r{, Hurd command}
19385 @cindex thread properties, @sc{gnu} Hurd
19386 @cindex pause current thread (@sc{gnu} Hurd)
19387 This command toggles current thread suspension when @value{GDBN} has
19388 control. Setting it to on takes effect immediately, and the current
19389 thread is suspended whenever @value{GDBN} gets control. Setting it to
19390 off will take effect the next time the inferior is continued.
19391 Normally, this command has no effect, since when @value{GDBN} has
19392 control, the whole task is suspended. However, if you used @code{set
19393 task pause off} (see above), this command comes in handy to suspend
19394 only the current thread.
19396 @item show thread pause
19397 @kindex show thread@r{, Hurd command}
19398 This command shows the state of current thread suspension.
19400 @item set thread run
19401 This command sets whether the current thread is allowed to run.
19403 @item show thread run
19404 Show whether the current thread is allowed to run.
19406 @item set thread detach-suspend-count
19407 @cindex thread suspend count, @sc{gnu} Hurd
19408 @cindex detach from thread, @sc{gnu} Hurd
19409 This command sets the suspend count @value{GDBN} will leave on a
19410 thread when detaching. This number is relative to the suspend count
19411 found by @value{GDBN} when it notices the thread; use @code{set thread
19412 takeover-suspend-count} to force it to an absolute value.
19414 @item show thread detach-suspend-count
19415 Show the suspend count @value{GDBN} will leave on the thread when
19418 @item set thread exception-port
19419 @itemx set thread excp
19420 Set the thread exception port to which to forward exceptions. This
19421 overrides the port set by @code{set task exception-port} (see above).
19422 @code{set thread excp} is the shorthand alias.
19424 @item set thread takeover-suspend-count
19425 Normally, @value{GDBN}'s thread suspend counts are relative to the
19426 value @value{GDBN} finds when it notices each thread. This command
19427 changes the suspend counts to be absolute instead.
19429 @item set thread default
19430 @itemx show thread default
19431 @cindex thread default settings, @sc{gnu} Hurd
19432 Each of the above @code{set thread} commands has a @code{set thread
19433 default} counterpart (e.g., @code{set thread default pause}, @code{set
19434 thread default exception-port}, etc.). The @code{thread default}
19435 variety of commands sets the default thread properties for all
19436 threads; you can then change the properties of individual threads with
19437 the non-default commands.
19444 @value{GDBN} provides the following commands specific to the Darwin target:
19447 @item set debug darwin @var{num}
19448 @kindex set debug darwin
19449 When set to a non zero value, enables debugging messages specific to
19450 the Darwin support. Higher values produce more verbose output.
19452 @item show debug darwin
19453 @kindex show debug darwin
19454 Show the current state of Darwin messages.
19456 @item set debug mach-o @var{num}
19457 @kindex set debug mach-o
19458 When set to a non zero value, enables debugging messages while
19459 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19460 file format used on Darwin for object and executable files.) Higher
19461 values produce more verbose output. This is a command to diagnose
19462 problems internal to @value{GDBN} and should not be needed in normal
19465 @item show debug mach-o
19466 @kindex show debug mach-o
19467 Show the current state of Mach-O file messages.
19469 @item set mach-exceptions on
19470 @itemx set mach-exceptions off
19471 @kindex set mach-exceptions
19472 On Darwin, faults are first reported as a Mach exception and are then
19473 mapped to a Posix signal. Use this command to turn on trapping of
19474 Mach exceptions in the inferior. This might be sometimes useful to
19475 better understand the cause of a fault. The default is off.
19477 @item show mach-exceptions
19478 @kindex show mach-exceptions
19479 Show the current state of exceptions trapping.
19484 @section Embedded Operating Systems
19486 This section describes configurations involving the debugging of
19487 embedded operating systems that are available for several different
19491 * VxWorks:: Using @value{GDBN} with VxWorks
19494 @value{GDBN} includes the ability to debug programs running on
19495 various real-time operating systems.
19498 @subsection Using @value{GDBN} with VxWorks
19504 @kindex target vxworks
19505 @item target vxworks @var{machinename}
19506 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19507 is the target system's machine name or IP address.
19511 On VxWorks, @code{load} links @var{filename} dynamically on the
19512 current target system as well as adding its symbols in @value{GDBN}.
19514 @value{GDBN} enables developers to spawn and debug tasks running on networked
19515 VxWorks targets from a Unix host. Already-running tasks spawned from
19516 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19517 both the Unix host and on the VxWorks target. The program
19518 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19519 installed with the name @code{vxgdb}, to distinguish it from a
19520 @value{GDBN} for debugging programs on the host itself.)
19523 @item VxWorks-timeout @var{args}
19524 @kindex vxworks-timeout
19525 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19526 This option is set by the user, and @var{args} represents the number of
19527 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19528 your VxWorks target is a slow software simulator or is on the far side
19529 of a thin network line.
19532 The following information on connecting to VxWorks was current when
19533 this manual was produced; newer releases of VxWorks may use revised
19536 @findex INCLUDE_RDB
19537 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19538 to include the remote debugging interface routines in the VxWorks
19539 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19540 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19541 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19542 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19543 information on configuring and remaking VxWorks, see the manufacturer's
19545 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19547 Once you have included @file{rdb.a} in your VxWorks system image and set
19548 your Unix execution search path to find @value{GDBN}, you are ready to
19549 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19550 @code{vxgdb}, depending on your installation).
19552 @value{GDBN} comes up showing the prompt:
19559 * VxWorks Connection:: Connecting to VxWorks
19560 * VxWorks Download:: VxWorks download
19561 * VxWorks Attach:: Running tasks
19564 @node VxWorks Connection
19565 @subsubsection Connecting to VxWorks
19567 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19568 network. To connect to a target whose host name is ``@code{tt}'', type:
19571 (vxgdb) target vxworks tt
19575 @value{GDBN} displays messages like these:
19578 Attaching remote machine across net...
19583 @value{GDBN} then attempts to read the symbol tables of any object modules
19584 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19585 these files by searching the directories listed in the command search
19586 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19587 to find an object file, it displays a message such as:
19590 prog.o: No such file or directory.
19593 When this happens, add the appropriate directory to the search path with
19594 the @value{GDBN} command @code{path}, and execute the @code{target}
19597 @node VxWorks Download
19598 @subsubsection VxWorks Download
19600 @cindex download to VxWorks
19601 If you have connected to the VxWorks target and you want to debug an
19602 object that has not yet been loaded, you can use the @value{GDBN}
19603 @code{load} command to download a file from Unix to VxWorks
19604 incrementally. The object file given as an argument to the @code{load}
19605 command is actually opened twice: first by the VxWorks target in order
19606 to download the code, then by @value{GDBN} in order to read the symbol
19607 table. This can lead to problems if the current working directories on
19608 the two systems differ. If both systems have NFS mounted the same
19609 filesystems, you can avoid these problems by using absolute paths.
19610 Otherwise, it is simplest to set the working directory on both systems
19611 to the directory in which the object file resides, and then to reference
19612 the file by its name, without any path. For instance, a program
19613 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19614 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19615 program, type this on VxWorks:
19618 -> cd "@var{vxpath}/vw/demo/rdb"
19622 Then, in @value{GDBN}, type:
19625 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19626 (vxgdb) load prog.o
19629 @value{GDBN} displays a response similar to this:
19632 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19635 You can also use the @code{load} command to reload an object module
19636 after editing and recompiling the corresponding source file. Note that
19637 this makes @value{GDBN} delete all currently-defined breakpoints,
19638 auto-displays, and convenience variables, and to clear the value
19639 history. (This is necessary in order to preserve the integrity of
19640 debugger's data structures that reference the target system's symbol
19643 @node VxWorks Attach
19644 @subsubsection Running Tasks
19646 @cindex running VxWorks tasks
19647 You can also attach to an existing task using the @code{attach} command as
19651 (vxgdb) attach @var{task}
19655 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19656 or suspended when you attach to it. Running tasks are suspended at
19657 the time of attachment.
19659 @node Embedded Processors
19660 @section Embedded Processors
19662 This section goes into details specific to particular embedded
19665 @cindex send command to simulator
19666 Whenever a specific embedded processor has a simulator, @value{GDBN}
19667 allows to send an arbitrary command to the simulator.
19670 @item sim @var{command}
19671 @kindex sim@r{, a command}
19672 Send an arbitrary @var{command} string to the simulator. Consult the
19673 documentation for the specific simulator in use for information about
19674 acceptable commands.
19680 * M32R/D:: Renesas M32R/D
19681 * M68K:: Motorola M68K
19682 * MicroBlaze:: Xilinx MicroBlaze
19683 * MIPS Embedded:: MIPS Embedded
19684 * OpenRISC 1000:: OpenRisc 1000
19685 * PowerPC Embedded:: PowerPC Embedded
19686 * PA:: HP PA Embedded
19687 * Sparclet:: Tsqware Sparclet
19688 * Sparclite:: Fujitsu Sparclite
19689 * Z8000:: Zilog Z8000
19692 * Super-H:: Renesas Super-H
19701 @item target rdi @var{dev}
19702 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19703 use this target to communicate with both boards running the Angel
19704 monitor, or with the EmbeddedICE JTAG debug device.
19707 @item target rdp @var{dev}
19712 @value{GDBN} provides the following ARM-specific commands:
19715 @item set arm disassembler
19717 This commands selects from a list of disassembly styles. The
19718 @code{"std"} style is the standard style.
19720 @item show arm disassembler
19722 Show the current disassembly style.
19724 @item set arm apcs32
19725 @cindex ARM 32-bit mode
19726 This command toggles ARM operation mode between 32-bit and 26-bit.
19728 @item show arm apcs32
19729 Display the current usage of the ARM 32-bit mode.
19731 @item set arm fpu @var{fputype}
19732 This command sets the ARM floating-point unit (FPU) type. The
19733 argument @var{fputype} can be one of these:
19737 Determine the FPU type by querying the OS ABI.
19739 Software FPU, with mixed-endian doubles on little-endian ARM
19742 GCC-compiled FPA co-processor.
19744 Software FPU with pure-endian doubles.
19750 Show the current type of the FPU.
19753 This command forces @value{GDBN} to use the specified ABI.
19756 Show the currently used ABI.
19758 @item set arm fallback-mode (arm|thumb|auto)
19759 @value{GDBN} uses the symbol table, when available, to determine
19760 whether instructions are ARM or Thumb. This command controls
19761 @value{GDBN}'s default behavior when the symbol table is not
19762 available. The default is @samp{auto}, which causes @value{GDBN} to
19763 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19766 @item show arm fallback-mode
19767 Show the current fallback instruction mode.
19769 @item set arm force-mode (arm|thumb|auto)
19770 This command overrides use of the symbol table to determine whether
19771 instructions are ARM or Thumb. The default is @samp{auto}, which
19772 causes @value{GDBN} to use the symbol table and then the setting
19773 of @samp{set arm fallback-mode}.
19775 @item show arm force-mode
19776 Show the current forced instruction mode.
19778 @item set debug arm
19779 Toggle whether to display ARM-specific debugging messages from the ARM
19780 target support subsystem.
19782 @item show debug arm
19783 Show whether ARM-specific debugging messages are enabled.
19786 The following commands are available when an ARM target is debugged
19787 using the RDI interface:
19790 @item rdilogfile @r{[}@var{file}@r{]}
19792 @cindex ADP (Angel Debugger Protocol) logging
19793 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19794 With an argument, sets the log file to the specified @var{file}. With
19795 no argument, show the current log file name. The default log file is
19798 @item rdilogenable @r{[}@var{arg}@r{]}
19799 @kindex rdilogenable
19800 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19801 enables logging, with an argument 0 or @code{"no"} disables it. With
19802 no arguments displays the current setting. When logging is enabled,
19803 ADP packets exchanged between @value{GDBN} and the RDI target device
19804 are logged to a file.
19806 @item set rdiromatzero
19807 @kindex set rdiromatzero
19808 @cindex ROM at zero address, RDI
19809 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19810 vector catching is disabled, so that zero address can be used. If off
19811 (the default), vector catching is enabled. For this command to take
19812 effect, it needs to be invoked prior to the @code{target rdi} command.
19814 @item show rdiromatzero
19815 @kindex show rdiromatzero
19816 Show the current setting of ROM at zero address.
19818 @item set rdiheartbeat
19819 @kindex set rdiheartbeat
19820 @cindex RDI heartbeat
19821 Enable or disable RDI heartbeat packets. It is not recommended to
19822 turn on this option, since it confuses ARM and EPI JTAG interface, as
19823 well as the Angel monitor.
19825 @item show rdiheartbeat
19826 @kindex show rdiheartbeat
19827 Show the setting of RDI heartbeat packets.
19831 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19832 The @value{GDBN} ARM simulator accepts the following optional arguments.
19835 @item --swi-support=@var{type}
19836 Tell the simulator which SWI interfaces to support.
19837 @var{type} may be a comma separated list of the following values.
19838 The default value is @code{all}.
19851 @subsection Renesas M32R/D and M32R/SDI
19854 @kindex target m32r
19855 @item target m32r @var{dev}
19856 Renesas M32R/D ROM monitor.
19858 @kindex target m32rsdi
19859 @item target m32rsdi @var{dev}
19860 Renesas M32R SDI server, connected via parallel port to the board.
19863 The following @value{GDBN} commands are specific to the M32R monitor:
19866 @item set download-path @var{path}
19867 @kindex set download-path
19868 @cindex find downloadable @sc{srec} files (M32R)
19869 Set the default path for finding downloadable @sc{srec} files.
19871 @item show download-path
19872 @kindex show download-path
19873 Show the default path for downloadable @sc{srec} files.
19875 @item set board-address @var{addr}
19876 @kindex set board-address
19877 @cindex M32-EVA target board address
19878 Set the IP address for the M32R-EVA target board.
19880 @item show board-address
19881 @kindex show board-address
19882 Show the current IP address of the target board.
19884 @item set server-address @var{addr}
19885 @kindex set server-address
19886 @cindex download server address (M32R)
19887 Set the IP address for the download server, which is the @value{GDBN}'s
19890 @item show server-address
19891 @kindex show server-address
19892 Display the IP address of the download server.
19894 @item upload @r{[}@var{file}@r{]}
19895 @kindex upload@r{, M32R}
19896 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
19897 upload capability. If no @var{file} argument is given, the current
19898 executable file is uploaded.
19900 @item tload @r{[}@var{file}@r{]}
19901 @kindex tload@r{, M32R}
19902 Test the @code{upload} command.
19905 The following commands are available for M32R/SDI:
19910 @cindex reset SDI connection, M32R
19911 This command resets the SDI connection.
19915 This command shows the SDI connection status.
19918 @kindex debug_chaos
19919 @cindex M32R/Chaos debugging
19920 Instructs the remote that M32R/Chaos debugging is to be used.
19922 @item use_debug_dma
19923 @kindex use_debug_dma
19924 Instructs the remote to use the DEBUG_DMA method of accessing memory.
19927 @kindex use_mon_code
19928 Instructs the remote to use the MON_CODE method of accessing memory.
19931 @kindex use_ib_break
19932 Instructs the remote to set breakpoints by IB break.
19934 @item use_dbt_break
19935 @kindex use_dbt_break
19936 Instructs the remote to set breakpoints by DBT.
19942 The Motorola m68k configuration includes ColdFire support, and a
19943 target command for the following ROM monitor.
19947 @kindex target dbug
19948 @item target dbug @var{dev}
19949 dBUG ROM monitor for Motorola ColdFire.
19954 @subsection MicroBlaze
19955 @cindex Xilinx MicroBlaze
19956 @cindex XMD, Xilinx Microprocessor Debugger
19958 The MicroBlaze is a soft-core processor supported on various Xilinx
19959 FPGAs, such as Spartan or Virtex series. Boards with these processors
19960 usually have JTAG ports which connect to a host system running the Xilinx
19961 Embedded Development Kit (EDK) or Software Development Kit (SDK).
19962 This host system is used to download the configuration bitstream to
19963 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
19964 communicates with the target board using the JTAG interface and
19965 presents a @code{gdbserver} interface to the board. By default
19966 @code{xmd} uses port @code{1234}. (While it is possible to change
19967 this default port, it requires the use of undocumented @code{xmd}
19968 commands. Contact Xilinx support if you need to do this.)
19970 Use these GDB commands to connect to the MicroBlaze target processor.
19973 @item target remote :1234
19974 Use this command to connect to the target if you are running @value{GDBN}
19975 on the same system as @code{xmd}.
19977 @item target remote @var{xmd-host}:1234
19978 Use this command to connect to the target if it is connected to @code{xmd}
19979 running on a different system named @var{xmd-host}.
19982 Use this command to download a program to the MicroBlaze target.
19984 @item set debug microblaze @var{n}
19985 Enable MicroBlaze-specific debugging messages if non-zero.
19987 @item show debug microblaze @var{n}
19988 Show MicroBlaze-specific debugging level.
19991 @node MIPS Embedded
19992 @subsection @acronym{MIPS} Embedded
19994 @cindex @acronym{MIPS} boards
19995 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
19996 @acronym{MIPS} board attached to a serial line. This is available when
19997 you configure @value{GDBN} with @samp{--target=mips-elf}.
20000 Use these @value{GDBN} commands to specify the connection to your target board:
20003 @item target mips @var{port}
20004 @kindex target mips @var{port}
20005 To run a program on the board, start up @code{@value{GDBP}} with the
20006 name of your program as the argument. To connect to the board, use the
20007 command @samp{target mips @var{port}}, where @var{port} is the name of
20008 the serial port connected to the board. If the program has not already
20009 been downloaded to the board, you may use the @code{load} command to
20010 download it. You can then use all the usual @value{GDBN} commands.
20012 For example, this sequence connects to the target board through a serial
20013 port, and loads and runs a program called @var{prog} through the
20017 host$ @value{GDBP} @var{prog}
20018 @value{GDBN} is free software and @dots{}
20019 (@value{GDBP}) target mips /dev/ttyb
20020 (@value{GDBP}) load @var{prog}
20024 @item target mips @var{hostname}:@var{portnumber}
20025 On some @value{GDBN} host configurations, you can specify a TCP
20026 connection (for instance, to a serial line managed by a terminal
20027 concentrator) instead of a serial port, using the syntax
20028 @samp{@var{hostname}:@var{portnumber}}.
20030 @item target pmon @var{port}
20031 @kindex target pmon @var{port}
20034 @item target ddb @var{port}
20035 @kindex target ddb @var{port}
20036 NEC's DDB variant of PMON for Vr4300.
20038 @item target lsi @var{port}
20039 @kindex target lsi @var{port}
20040 LSI variant of PMON.
20042 @kindex target r3900
20043 @item target r3900 @var{dev}
20044 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20046 @kindex target array
20047 @item target array @var{dev}
20048 Array Tech LSI33K RAID controller board.
20054 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20057 @item set mipsfpu double
20058 @itemx set mipsfpu single
20059 @itemx set mipsfpu none
20060 @itemx set mipsfpu auto
20061 @itemx show mipsfpu
20062 @kindex set mipsfpu
20063 @kindex show mipsfpu
20064 @cindex @acronym{MIPS} remote floating point
20065 @cindex floating point, @acronym{MIPS} remote
20066 If your target board does not support the @acronym{MIPS} floating point
20067 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20068 need this, you may wish to put the command in your @value{GDBN} init
20069 file). This tells @value{GDBN} how to find the return value of
20070 functions which return floating point values. It also allows
20071 @value{GDBN} to avoid saving the floating point registers when calling
20072 functions on the board. If you are using a floating point coprocessor
20073 with only single precision floating point support, as on the @sc{r4650}
20074 processor, use the command @samp{set mipsfpu single}. The default
20075 double precision floating point coprocessor may be selected using
20076 @samp{set mipsfpu double}.
20078 In previous versions the only choices were double precision or no
20079 floating point, so @samp{set mipsfpu on} will select double precision
20080 and @samp{set mipsfpu off} will select no floating point.
20082 As usual, you can inquire about the @code{mipsfpu} variable with
20083 @samp{show mipsfpu}.
20085 @item set timeout @var{seconds}
20086 @itemx set retransmit-timeout @var{seconds}
20087 @itemx show timeout
20088 @itemx show retransmit-timeout
20089 @cindex @code{timeout}, @acronym{MIPS} protocol
20090 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20091 @kindex set timeout
20092 @kindex show timeout
20093 @kindex set retransmit-timeout
20094 @kindex show retransmit-timeout
20095 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20096 remote protocol, with the @code{set timeout @var{seconds}} command. The
20097 default is 5 seconds. Similarly, you can control the timeout used while
20098 waiting for an acknowledgment of a packet with the @code{set
20099 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20100 You can inspect both values with @code{show timeout} and @code{show
20101 retransmit-timeout}. (These commands are @emph{only} available when
20102 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20104 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20105 is waiting for your program to stop. In that case, @value{GDBN} waits
20106 forever because it has no way of knowing how long the program is going
20107 to run before stopping.
20109 @item set syn-garbage-limit @var{num}
20110 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20111 @cindex synchronize with remote @acronym{MIPS} target
20112 Limit the maximum number of characters @value{GDBN} should ignore when
20113 it tries to synchronize with the remote target. The default is 10
20114 characters. Setting the limit to -1 means there's no limit.
20116 @item show syn-garbage-limit
20117 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20118 Show the current limit on the number of characters to ignore when
20119 trying to synchronize with the remote system.
20121 @item set monitor-prompt @var{prompt}
20122 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20123 @cindex remote monitor prompt
20124 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20125 remote monitor. The default depends on the target:
20135 @item show monitor-prompt
20136 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20137 Show the current strings @value{GDBN} expects as the prompt from the
20140 @item set monitor-warnings
20141 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20142 Enable or disable monitor warnings about hardware breakpoints. This
20143 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20144 display warning messages whose codes are returned by the @code{lsi}
20145 PMON monitor for breakpoint commands.
20147 @item show monitor-warnings
20148 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20149 Show the current setting of printing monitor warnings.
20151 @item pmon @var{command}
20152 @kindex pmon@r{, @acronym{MIPS} remote}
20153 @cindex send PMON command
20154 This command allows sending an arbitrary @var{command} string to the
20155 monitor. The monitor must be in debug mode for this to work.
20158 @node OpenRISC 1000
20159 @subsection OpenRISC 1000
20160 @cindex OpenRISC 1000
20162 @cindex or1k boards
20163 See OR1k Architecture document (@uref{www.opencores.org}) for more information
20164 about platform and commands.
20168 @kindex target jtag
20169 @item target jtag jtag://@var{host}:@var{port}
20171 Connects to remote JTAG server.
20172 JTAG remote server can be either an or1ksim or JTAG server,
20173 connected via parallel port to the board.
20175 Example: @code{target jtag jtag://localhost:9999}
20178 @item or1ksim @var{command}
20179 If connected to @code{or1ksim} OpenRISC 1000 Architectural
20180 Simulator, proprietary commands can be executed.
20182 @kindex info or1k spr
20183 @item info or1k spr
20184 Displays spr groups.
20186 @item info or1k spr @var{group}
20187 @itemx info or1k spr @var{groupno}
20188 Displays register names in selected group.
20190 @item info or1k spr @var{group} @var{register}
20191 @itemx info or1k spr @var{register}
20192 @itemx info or1k spr @var{groupno} @var{registerno}
20193 @itemx info or1k spr @var{registerno}
20194 Shows information about specified spr register.
20197 @item spr @var{group} @var{register} @var{value}
20198 @itemx spr @var{register @var{value}}
20199 @itemx spr @var{groupno} @var{registerno @var{value}}
20200 @itemx spr @var{registerno @var{value}}
20201 Writes @var{value} to specified spr register.
20204 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
20205 It is very similar to @value{GDBN} trace, except it does not interfere with normal
20206 program execution and is thus much faster. Hardware breakpoints/watchpoint
20207 triggers can be set using:
20210 Load effective address/data
20212 Store effective address/data
20214 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
20219 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
20220 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
20222 @code{htrace} commands:
20223 @cindex OpenRISC 1000 htrace
20226 @item hwatch @var{conditional}
20227 Set hardware watchpoint on combination of Load/Store Effective Address(es)
20228 or Data. For example:
20230 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20232 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20236 Display information about current HW trace configuration.
20238 @item htrace trigger @var{conditional}
20239 Set starting criteria for HW trace.
20241 @item htrace qualifier @var{conditional}
20242 Set acquisition qualifier for HW trace.
20244 @item htrace stop @var{conditional}
20245 Set HW trace stopping criteria.
20247 @item htrace record [@var{data}]*
20248 Selects the data to be recorded, when qualifier is met and HW trace was
20251 @item htrace enable
20252 @itemx htrace disable
20253 Enables/disables the HW trace.
20255 @item htrace rewind [@var{filename}]
20256 Clears currently recorded trace data.
20258 If filename is specified, new trace file is made and any newly collected data
20259 will be written there.
20261 @item htrace print [@var{start} [@var{len}]]
20262 Prints trace buffer, using current record configuration.
20264 @item htrace mode continuous
20265 Set continuous trace mode.
20267 @item htrace mode suspend
20268 Set suspend trace mode.
20272 @node PowerPC Embedded
20273 @subsection PowerPC Embedded
20275 @cindex DVC register
20276 @value{GDBN} supports using the DVC (Data Value Compare) register to
20277 implement in hardware simple hardware watchpoint conditions of the form:
20280 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20281 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20284 The DVC register will be automatically used when @value{GDBN} detects
20285 such pattern in a condition expression, and the created watchpoint uses one
20286 debug register (either the @code{exact-watchpoints} option is on and the
20287 variable is scalar, or the variable has a length of one byte). This feature
20288 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20291 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20292 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20293 in which case watchpoints using only one debug register are created when
20294 watching variables of scalar types.
20296 You can create an artificial array to watch an arbitrary memory
20297 region using one of the following commands (@pxref{Expressions}):
20300 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20301 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20304 PowerPC embedded processors support masked watchpoints. See the discussion
20305 about the @code{mask} argument in @ref{Set Watchpoints}.
20307 @cindex ranged breakpoint
20308 PowerPC embedded processors support hardware accelerated
20309 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20310 the inferior whenever it executes an instruction at any address within
20311 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20312 use the @code{break-range} command.
20314 @value{GDBN} provides the following PowerPC-specific commands:
20317 @kindex break-range
20318 @item break-range @var{start-location}, @var{end-location}
20319 Set a breakpoint for an address range.
20320 @var{start-location} and @var{end-location} can specify a function name,
20321 a line number, an offset of lines from the current line or from the start
20322 location, or an address of an instruction (see @ref{Specify Location},
20323 for a list of all the possible ways to specify a @var{location}.)
20324 The breakpoint will stop execution of the inferior whenever it
20325 executes an instruction at any address within the specified range,
20326 (including @var{start-location} and @var{end-location}.)
20328 @kindex set powerpc
20329 @item set powerpc soft-float
20330 @itemx show powerpc soft-float
20331 Force @value{GDBN} to use (or not use) a software floating point calling
20332 convention. By default, @value{GDBN} selects the calling convention based
20333 on the selected architecture and the provided executable file.
20335 @item set powerpc vector-abi
20336 @itemx show powerpc vector-abi
20337 Force @value{GDBN} to use the specified calling convention for vector
20338 arguments and return values. The valid options are @samp{auto};
20339 @samp{generic}, to avoid vector registers even if they are present;
20340 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20341 registers. By default, @value{GDBN} selects the calling convention
20342 based on the selected architecture and the provided executable file.
20344 @item set powerpc exact-watchpoints
20345 @itemx show powerpc exact-watchpoints
20346 Allow @value{GDBN} to use only one debug register when watching a variable
20347 of scalar type, thus assuming that the variable is accessed through the
20348 address of its first byte.
20350 @kindex target dink32
20351 @item target dink32 @var{dev}
20352 DINK32 ROM monitor.
20354 @kindex target ppcbug
20355 @item target ppcbug @var{dev}
20356 @kindex target ppcbug1
20357 @item target ppcbug1 @var{dev}
20358 PPCBUG ROM monitor for PowerPC.
20361 @item target sds @var{dev}
20362 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20365 @cindex SDS protocol
20366 The following commands specific to the SDS protocol are supported
20370 @item set sdstimeout @var{nsec}
20371 @kindex set sdstimeout
20372 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20373 default is 2 seconds.
20375 @item show sdstimeout
20376 @kindex show sdstimeout
20377 Show the current value of the SDS timeout.
20379 @item sds @var{command}
20380 @kindex sds@r{, a command}
20381 Send the specified @var{command} string to the SDS monitor.
20386 @subsection HP PA Embedded
20390 @kindex target op50n
20391 @item target op50n @var{dev}
20392 OP50N monitor, running on an OKI HPPA board.
20394 @kindex target w89k
20395 @item target w89k @var{dev}
20396 W89K monitor, running on a Winbond HPPA board.
20401 @subsection Tsqware Sparclet
20405 @value{GDBN} enables developers to debug tasks running on
20406 Sparclet targets from a Unix host.
20407 @value{GDBN} uses code that runs on
20408 both the Unix host and on the Sparclet target. The program
20409 @code{@value{GDBP}} is installed and executed on the Unix host.
20412 @item remotetimeout @var{args}
20413 @kindex remotetimeout
20414 @value{GDBN} supports the option @code{remotetimeout}.
20415 This option is set by the user, and @var{args} represents the number of
20416 seconds @value{GDBN} waits for responses.
20419 @cindex compiling, on Sparclet
20420 When compiling for debugging, include the options @samp{-g} to get debug
20421 information and @samp{-Ttext} to relocate the program to where you wish to
20422 load it on the target. You may also want to add the options @samp{-n} or
20423 @samp{-N} in order to reduce the size of the sections. Example:
20426 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20429 You can use @code{objdump} to verify that the addresses are what you intended:
20432 sparclet-aout-objdump --headers --syms prog
20435 @cindex running, on Sparclet
20437 your Unix execution search path to find @value{GDBN}, you are ready to
20438 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20439 (or @code{sparclet-aout-gdb}, depending on your installation).
20441 @value{GDBN} comes up showing the prompt:
20448 * Sparclet File:: Setting the file to debug
20449 * Sparclet Connection:: Connecting to Sparclet
20450 * Sparclet Download:: Sparclet download
20451 * Sparclet Execution:: Running and debugging
20454 @node Sparclet File
20455 @subsubsection Setting File to Debug
20457 The @value{GDBN} command @code{file} lets you choose with program to debug.
20460 (gdbslet) file prog
20464 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20465 @value{GDBN} locates
20466 the file by searching the directories listed in the command search
20468 If the file was compiled with debug information (option @samp{-g}), source
20469 files will be searched as well.
20470 @value{GDBN} locates
20471 the source files by searching the directories listed in the directory search
20472 path (@pxref{Environment, ,Your Program's Environment}).
20474 to find a file, it displays a message such as:
20477 prog: No such file or directory.
20480 When this happens, add the appropriate directories to the search paths with
20481 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20482 @code{target} command again.
20484 @node Sparclet Connection
20485 @subsubsection Connecting to Sparclet
20487 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20488 To connect to a target on serial port ``@code{ttya}'', type:
20491 (gdbslet) target sparclet /dev/ttya
20492 Remote target sparclet connected to /dev/ttya
20493 main () at ../prog.c:3
20497 @value{GDBN} displays messages like these:
20503 @node Sparclet Download
20504 @subsubsection Sparclet Download
20506 @cindex download to Sparclet
20507 Once connected to the Sparclet target,
20508 you can use the @value{GDBN}
20509 @code{load} command to download the file from the host to the target.
20510 The file name and load offset should be given as arguments to the @code{load}
20512 Since the file format is aout, the program must be loaded to the starting
20513 address. You can use @code{objdump} to find out what this value is. The load
20514 offset is an offset which is added to the VMA (virtual memory address)
20515 of each of the file's sections.
20516 For instance, if the program
20517 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20518 and bss at 0x12010170, in @value{GDBN}, type:
20521 (gdbslet) load prog 0x12010000
20522 Loading section .text, size 0xdb0 vma 0x12010000
20525 If the code is loaded at a different address then what the program was linked
20526 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20527 to tell @value{GDBN} where to map the symbol table.
20529 @node Sparclet Execution
20530 @subsubsection Running and Debugging
20532 @cindex running and debugging Sparclet programs
20533 You can now begin debugging the task using @value{GDBN}'s execution control
20534 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20535 manual for the list of commands.
20539 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20541 Starting program: prog
20542 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20543 3 char *symarg = 0;
20545 4 char *execarg = "hello!";
20550 @subsection Fujitsu Sparclite
20554 @kindex target sparclite
20555 @item target sparclite @var{dev}
20556 Fujitsu sparclite boards, used only for the purpose of loading.
20557 You must use an additional command to debug the program.
20558 For example: target remote @var{dev} using @value{GDBN} standard
20564 @subsection Zilog Z8000
20567 @cindex simulator, Z8000
20568 @cindex Zilog Z8000 simulator
20570 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20573 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20574 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20575 segmented variant). The simulator recognizes which architecture is
20576 appropriate by inspecting the object code.
20579 @item target sim @var{args}
20581 @kindex target sim@r{, with Z8000}
20582 Debug programs on a simulated CPU. If the simulator supports setup
20583 options, specify them via @var{args}.
20587 After specifying this target, you can debug programs for the simulated
20588 CPU in the same style as programs for your host computer; use the
20589 @code{file} command to load a new program image, the @code{run} command
20590 to run your program, and so on.
20592 As well as making available all the usual machine registers
20593 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20594 additional items of information as specially named registers:
20599 Counts clock-ticks in the simulator.
20602 Counts instructions run in the simulator.
20605 Execution time in 60ths of a second.
20609 You can refer to these values in @value{GDBN} expressions with the usual
20610 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20611 conditional breakpoint that suspends only after at least 5000
20612 simulated clock ticks.
20615 @subsection Atmel AVR
20618 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20619 following AVR-specific commands:
20622 @item info io_registers
20623 @kindex info io_registers@r{, AVR}
20624 @cindex I/O registers (Atmel AVR)
20625 This command displays information about the AVR I/O registers. For
20626 each register, @value{GDBN} prints its number and value.
20633 When configured for debugging CRIS, @value{GDBN} provides the
20634 following CRIS-specific commands:
20637 @item set cris-version @var{ver}
20638 @cindex CRIS version
20639 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20640 The CRIS version affects register names and sizes. This command is useful in
20641 case autodetection of the CRIS version fails.
20643 @item show cris-version
20644 Show the current CRIS version.
20646 @item set cris-dwarf2-cfi
20647 @cindex DWARF-2 CFI and CRIS
20648 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20649 Change to @samp{off} when using @code{gcc-cris} whose version is below
20652 @item show cris-dwarf2-cfi
20653 Show the current state of using DWARF-2 CFI.
20655 @item set cris-mode @var{mode}
20657 Set the current CRIS mode to @var{mode}. It should only be changed when
20658 debugging in guru mode, in which case it should be set to
20659 @samp{guru} (the default is @samp{normal}).
20661 @item show cris-mode
20662 Show the current CRIS mode.
20666 @subsection Renesas Super-H
20669 For the Renesas Super-H processor, @value{GDBN} provides these
20673 @item set sh calling-convention @var{convention}
20674 @kindex set sh calling-convention
20675 Set the calling-convention used when calling functions from @value{GDBN}.
20676 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20677 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20678 convention. If the DWARF-2 information of the called function specifies
20679 that the function follows the Renesas calling convention, the function
20680 is called using the Renesas calling convention. If the calling convention
20681 is set to @samp{renesas}, the Renesas calling convention is always used,
20682 regardless of the DWARF-2 information. This can be used to override the
20683 default of @samp{gcc} if debug information is missing, or the compiler
20684 does not emit the DWARF-2 calling convention entry for a function.
20686 @item show sh calling-convention
20687 @kindex show sh calling-convention
20688 Show the current calling convention setting.
20693 @node Architectures
20694 @section Architectures
20696 This section describes characteristics of architectures that affect
20697 all uses of @value{GDBN} with the architecture, both native and cross.
20704 * HPPA:: HP PA architecture
20705 * SPU:: Cell Broadband Engine SPU architecture
20710 @subsection AArch64
20711 @cindex AArch64 support
20713 When @value{GDBN} is debugging the AArch64 architecture, it provides the
20714 following special commands:
20717 @item set debug aarch64
20718 @kindex set debug aarch64
20719 This command determines whether AArch64 architecture-specific debugging
20720 messages are to be displayed.
20722 @item show debug aarch64
20723 Show whether AArch64 debugging messages are displayed.
20728 @subsection x86 Architecture-specific Issues
20731 @item set struct-convention @var{mode}
20732 @kindex set struct-convention
20733 @cindex struct return convention
20734 @cindex struct/union returned in registers
20735 Set the convention used by the inferior to return @code{struct}s and
20736 @code{union}s from functions to @var{mode}. Possible values of
20737 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20738 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20739 are returned on the stack, while @code{"reg"} means that a
20740 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20741 be returned in a register.
20743 @item show struct-convention
20744 @kindex show struct-convention
20745 Show the current setting of the convention to return @code{struct}s
20752 See the following section.
20755 @subsection @acronym{MIPS}
20757 @cindex stack on Alpha
20758 @cindex stack on @acronym{MIPS}
20759 @cindex Alpha stack
20760 @cindex @acronym{MIPS} stack
20761 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20762 sometimes requires @value{GDBN} to search backward in the object code to
20763 find the beginning of a function.
20765 @cindex response time, @acronym{MIPS} debugging
20766 To improve response time (especially for embedded applications, where
20767 @value{GDBN} may be restricted to a slow serial line for this search)
20768 you may want to limit the size of this search, using one of these
20772 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20773 @item set heuristic-fence-post @var{limit}
20774 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20775 search for the beginning of a function. A value of @var{0} (the
20776 default) means there is no limit. However, except for @var{0}, the
20777 larger the limit the more bytes @code{heuristic-fence-post} must search
20778 and therefore the longer it takes to run. You should only need to use
20779 this command when debugging a stripped executable.
20781 @item show heuristic-fence-post
20782 Display the current limit.
20786 These commands are available @emph{only} when @value{GDBN} is configured
20787 for debugging programs on Alpha or @acronym{MIPS} processors.
20789 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20793 @item set mips abi @var{arg}
20794 @kindex set mips abi
20795 @cindex set ABI for @acronym{MIPS}
20796 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20797 values of @var{arg} are:
20801 The default ABI associated with the current binary (this is the
20811 @item show mips abi
20812 @kindex show mips abi
20813 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20815 @item set mips compression @var{arg}
20816 @kindex set mips compression
20817 @cindex code compression, @acronym{MIPS}
20818 Tell @value{GDBN} which @acronym{MIPS} compressed
20819 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20820 inferior. @value{GDBN} uses this for code disassembly and other
20821 internal interpretation purposes. This setting is only referred to
20822 when no executable has been associated with the debugging session or
20823 the executable does not provide information about the encoding it uses.
20824 Otherwise this setting is automatically updated from information
20825 provided by the executable.
20827 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20828 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20829 executables containing @acronym{MIPS16} code frequently are not
20830 identified as such.
20832 This setting is ``sticky''; that is, it retains its value across
20833 debugging sessions until reset either explicitly with this command or
20834 implicitly from an executable.
20836 The compiler and/or assembler typically add symbol table annotations to
20837 identify functions compiled for the @acronym{MIPS16} or
20838 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
20839 are present, @value{GDBN} uses them in preference to the global
20840 compressed @acronym{ISA} encoding setting.
20842 @item show mips compression
20843 @kindex show mips compression
20844 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
20845 @value{GDBN} to debug the inferior.
20848 @itemx show mipsfpu
20849 @xref{MIPS Embedded, set mipsfpu}.
20851 @item set mips mask-address @var{arg}
20852 @kindex set mips mask-address
20853 @cindex @acronym{MIPS} addresses, masking
20854 This command determines whether the most-significant 32 bits of 64-bit
20855 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
20856 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
20857 setting, which lets @value{GDBN} determine the correct value.
20859 @item show mips mask-address
20860 @kindex show mips mask-address
20861 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
20864 @item set remote-mips64-transfers-32bit-regs
20865 @kindex set remote-mips64-transfers-32bit-regs
20866 This command controls compatibility with 64-bit @acronym{MIPS} targets that
20867 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
20868 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
20869 and 64 bits for other registers, set this option to @samp{on}.
20871 @item show remote-mips64-transfers-32bit-regs
20872 @kindex show remote-mips64-transfers-32bit-regs
20873 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
20875 @item set debug mips
20876 @kindex set debug mips
20877 This command turns on and off debugging messages for the @acronym{MIPS}-specific
20878 target code in @value{GDBN}.
20880 @item show debug mips
20881 @kindex show debug mips
20882 Show the current setting of @acronym{MIPS} debugging messages.
20888 @cindex HPPA support
20890 When @value{GDBN} is debugging the HP PA architecture, it provides the
20891 following special commands:
20894 @item set debug hppa
20895 @kindex set debug hppa
20896 This command determines whether HPPA architecture-specific debugging
20897 messages are to be displayed.
20899 @item show debug hppa
20900 Show whether HPPA debugging messages are displayed.
20902 @item maint print unwind @var{address}
20903 @kindex maint print unwind@r{, HPPA}
20904 This command displays the contents of the unwind table entry at the
20905 given @var{address}.
20911 @subsection Cell Broadband Engine SPU architecture
20912 @cindex Cell Broadband Engine
20915 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
20916 it provides the following special commands:
20919 @item info spu event
20921 Display SPU event facility status. Shows current event mask
20922 and pending event status.
20924 @item info spu signal
20925 Display SPU signal notification facility status. Shows pending
20926 signal-control word and signal notification mode of both signal
20927 notification channels.
20929 @item info spu mailbox
20930 Display SPU mailbox facility status. Shows all pending entries,
20931 in order of processing, in each of the SPU Write Outbound,
20932 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
20935 Display MFC DMA status. Shows all pending commands in the MFC
20936 DMA queue. For each entry, opcode, tag, class IDs, effective
20937 and local store addresses and transfer size are shown.
20939 @item info spu proxydma
20940 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
20941 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
20942 and local store addresses and transfer size are shown.
20946 When @value{GDBN} is debugging a combined PowerPC/SPU application
20947 on the Cell Broadband Engine, it provides in addition the following
20951 @item set spu stop-on-load @var{arg}
20953 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
20954 will give control to the user when a new SPE thread enters its @code{main}
20955 function. The default is @code{off}.
20957 @item show spu stop-on-load
20959 Show whether to stop for new SPE threads.
20961 @item set spu auto-flush-cache @var{arg}
20962 Set whether to automatically flush the software-managed cache. When set to
20963 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
20964 cache to be flushed whenever SPE execution stops. This provides a consistent
20965 view of PowerPC memory that is accessed via the cache. If an application
20966 does not use the software-managed cache, this option has no effect.
20968 @item show spu auto-flush-cache
20969 Show whether to automatically flush the software-managed cache.
20974 @subsection PowerPC
20975 @cindex PowerPC architecture
20977 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
20978 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
20979 numbers stored in the floating point registers. These values must be stored
20980 in two consecutive registers, always starting at an even register like
20981 @code{f0} or @code{f2}.
20983 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
20984 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
20985 @code{f2} and @code{f3} for @code{$dl1} and so on.
20987 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
20988 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
20991 @node Controlling GDB
20992 @chapter Controlling @value{GDBN}
20994 You can alter the way @value{GDBN} interacts with you by using the
20995 @code{set} command. For commands controlling how @value{GDBN} displays
20996 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21001 * Editing:: Command editing
21002 * Command History:: Command history
21003 * Screen Size:: Screen size
21004 * Numbers:: Numbers
21005 * ABI:: Configuring the current ABI
21006 * Auto-loading:: Automatically loading associated files
21007 * Messages/Warnings:: Optional warnings and messages
21008 * Debugging Output:: Optional messages about internal happenings
21009 * Other Misc Settings:: Other Miscellaneous Settings
21017 @value{GDBN} indicates its readiness to read a command by printing a string
21018 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21019 can change the prompt string with the @code{set prompt} command. For
21020 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21021 the prompt in one of the @value{GDBN} sessions so that you can always tell
21022 which one you are talking to.
21024 @emph{Note:} @code{set prompt} does not add a space for you after the
21025 prompt you set. This allows you to set a prompt which ends in a space
21026 or a prompt that does not.
21030 @item set prompt @var{newprompt}
21031 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21033 @kindex show prompt
21035 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21038 Versions of @value{GDBN} that ship with Python scripting enabled have
21039 prompt extensions. The commands for interacting with these extensions
21043 @kindex set extended-prompt
21044 @item set extended-prompt @var{prompt}
21045 Set an extended prompt that allows for substitutions.
21046 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21047 substitution. Any escape sequences specified as part of the prompt
21048 string are replaced with the corresponding strings each time the prompt
21054 set extended-prompt Current working directory: \w (gdb)
21057 Note that when an extended-prompt is set, it takes control of the
21058 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21060 @kindex show extended-prompt
21061 @item show extended-prompt
21062 Prints the extended prompt. Any escape sequences specified as part of
21063 the prompt string with @code{set extended-prompt}, are replaced with the
21064 corresponding strings each time the prompt is displayed.
21068 @section Command Editing
21070 @cindex command line editing
21072 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21073 @sc{gnu} library provides consistent behavior for programs which provide a
21074 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21075 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21076 substitution, and a storage and recall of command history across
21077 debugging sessions.
21079 You may control the behavior of command line editing in @value{GDBN} with the
21080 command @code{set}.
21083 @kindex set editing
21086 @itemx set editing on
21087 Enable command line editing (enabled by default).
21089 @item set editing off
21090 Disable command line editing.
21092 @kindex show editing
21094 Show whether command line editing is enabled.
21097 @ifset SYSTEM_READLINE
21098 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21100 @ifclear SYSTEM_READLINE
21101 @xref{Command Line Editing},
21103 for more details about the Readline
21104 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21105 encouraged to read that chapter.
21107 @node Command History
21108 @section Command History
21109 @cindex command history
21111 @value{GDBN} can keep track of the commands you type during your
21112 debugging sessions, so that you can be certain of precisely what
21113 happened. Use these commands to manage the @value{GDBN} command
21116 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21117 package, to provide the history facility.
21118 @ifset SYSTEM_READLINE
21119 @xref{Using History Interactively, , , history, GNU History Library},
21121 @ifclear SYSTEM_READLINE
21122 @xref{Using History Interactively},
21124 for the detailed description of the History library.
21126 To issue a command to @value{GDBN} without affecting certain aspects of
21127 the state which is seen by users, prefix it with @samp{server }
21128 (@pxref{Server Prefix}). This
21129 means that this command will not affect the command history, nor will it
21130 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21131 pressed on a line by itself.
21133 @cindex @code{server}, command prefix
21134 The server prefix does not affect the recording of values into the value
21135 history; to print a value without recording it into the value history,
21136 use the @code{output} command instead of the @code{print} command.
21138 Here is the description of @value{GDBN} commands related to command
21142 @cindex history substitution
21143 @cindex history file
21144 @kindex set history filename
21145 @cindex @env{GDBHISTFILE}, environment variable
21146 @item set history filename @var{fname}
21147 Set the name of the @value{GDBN} command history file to @var{fname}.
21148 This is the file where @value{GDBN} reads an initial command history
21149 list, and where it writes the command history from this session when it
21150 exits. You can access this list through history expansion or through
21151 the history command editing characters listed below. This file defaults
21152 to the value of the environment variable @code{GDBHISTFILE}, or to
21153 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21156 @cindex save command history
21157 @kindex set history save
21158 @item set history save
21159 @itemx set history save on
21160 Record command history in a file, whose name may be specified with the
21161 @code{set history filename} command. By default, this option is disabled.
21163 @item set history save off
21164 Stop recording command history in a file.
21166 @cindex history size
21167 @kindex set history size
21168 @cindex @env{HISTSIZE}, environment variable
21169 @item set history size @var{size}
21170 Set the number of commands which @value{GDBN} keeps in its history list.
21171 This defaults to the value of the environment variable
21172 @code{HISTSIZE}, or to 256 if this variable is not set.
21175 History expansion assigns special meaning to the character @kbd{!}.
21176 @ifset SYSTEM_READLINE
21177 @xref{Event Designators, , , history, GNU History Library},
21179 @ifclear SYSTEM_READLINE
21180 @xref{Event Designators},
21184 @cindex history expansion, turn on/off
21185 Since @kbd{!} is also the logical not operator in C, history expansion
21186 is off by default. If you decide to enable history expansion with the
21187 @code{set history expansion on} command, you may sometimes need to
21188 follow @kbd{!} (when it is used as logical not, in an expression) with
21189 a space or a tab to prevent it from being expanded. The readline
21190 history facilities do not attempt substitution on the strings
21191 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21193 The commands to control history expansion are:
21196 @item set history expansion on
21197 @itemx set history expansion
21198 @kindex set history expansion
21199 Enable history expansion. History expansion is off by default.
21201 @item set history expansion off
21202 Disable history expansion.
21205 @kindex show history
21207 @itemx show history filename
21208 @itemx show history save
21209 @itemx show history size
21210 @itemx show history expansion
21211 These commands display the state of the @value{GDBN} history parameters.
21212 @code{show history} by itself displays all four states.
21217 @kindex show commands
21218 @cindex show last commands
21219 @cindex display command history
21220 @item show commands
21221 Display the last ten commands in the command history.
21223 @item show commands @var{n}
21224 Print ten commands centered on command number @var{n}.
21226 @item show commands +
21227 Print ten commands just after the commands last printed.
21231 @section Screen Size
21232 @cindex size of screen
21233 @cindex pauses in output
21235 Certain commands to @value{GDBN} may produce large amounts of
21236 information output to the screen. To help you read all of it,
21237 @value{GDBN} pauses and asks you for input at the end of each page of
21238 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21239 to discard the remaining output. Also, the screen width setting
21240 determines when to wrap lines of output. Depending on what is being
21241 printed, @value{GDBN} tries to break the line at a readable place,
21242 rather than simply letting it overflow onto the following line.
21244 Normally @value{GDBN} knows the size of the screen from the terminal
21245 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21246 together with the value of the @code{TERM} environment variable and the
21247 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21248 you can override it with the @code{set height} and @code{set
21255 @kindex show height
21256 @item set height @var{lpp}
21258 @itemx set width @var{cpl}
21260 These @code{set} commands specify a screen height of @var{lpp} lines and
21261 a screen width of @var{cpl} characters. The associated @code{show}
21262 commands display the current settings.
21264 If you specify a height of zero lines, @value{GDBN} does not pause during
21265 output no matter how long the output is. This is useful if output is to a
21266 file or to an editor buffer.
21268 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
21269 from wrapping its output.
21271 @item set pagination on
21272 @itemx set pagination off
21273 @kindex set pagination
21274 Turn the output pagination on or off; the default is on. Turning
21275 pagination off is the alternative to @code{set height 0}. Note that
21276 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21277 Options, -batch}) also automatically disables pagination.
21279 @item show pagination
21280 @kindex show pagination
21281 Show the current pagination mode.
21286 @cindex number representation
21287 @cindex entering numbers
21289 You can always enter numbers in octal, decimal, or hexadecimal in
21290 @value{GDBN} by the usual conventions: octal numbers begin with
21291 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21292 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21293 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21294 10; likewise, the default display for numbers---when no particular
21295 format is specified---is base 10. You can change the default base for
21296 both input and output with the commands described below.
21299 @kindex set input-radix
21300 @item set input-radix @var{base}
21301 Set the default base for numeric input. Supported choices
21302 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21303 specified either unambiguously or using the current input radix; for
21307 set input-radix 012
21308 set input-radix 10.
21309 set input-radix 0xa
21313 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21314 leaves the input radix unchanged, no matter what it was, since
21315 @samp{10}, being without any leading or trailing signs of its base, is
21316 interpreted in the current radix. Thus, if the current radix is 16,
21317 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21320 @kindex set output-radix
21321 @item set output-radix @var{base}
21322 Set the default base for numeric display. Supported choices
21323 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21324 specified either unambiguously or using the current input radix.
21326 @kindex show input-radix
21327 @item show input-radix
21328 Display the current default base for numeric input.
21330 @kindex show output-radix
21331 @item show output-radix
21332 Display the current default base for numeric display.
21334 @item set radix @r{[}@var{base}@r{]}
21338 These commands set and show the default base for both input and output
21339 of numbers. @code{set radix} sets the radix of input and output to
21340 the same base; without an argument, it resets the radix back to its
21341 default value of 10.
21346 @section Configuring the Current ABI
21348 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21349 application automatically. However, sometimes you need to override its
21350 conclusions. Use these commands to manage @value{GDBN}'s view of the
21356 @cindex Newlib OS ABI and its influence on the longjmp handling
21358 One @value{GDBN} configuration can debug binaries for multiple operating
21359 system targets, either via remote debugging or native emulation.
21360 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21361 but you can override its conclusion using the @code{set osabi} command.
21362 One example where this is useful is in debugging of binaries which use
21363 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21364 not have the same identifying marks that the standard C library for your
21367 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21368 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21369 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21370 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21374 Show the OS ABI currently in use.
21377 With no argument, show the list of registered available OS ABI's.
21379 @item set osabi @var{abi}
21380 Set the current OS ABI to @var{abi}.
21383 @cindex float promotion
21385 Generally, the way that an argument of type @code{float} is passed to a
21386 function depends on whether the function is prototyped. For a prototyped
21387 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21388 according to the architecture's convention for @code{float}. For unprototyped
21389 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21390 @code{double} and then passed.
21392 Unfortunately, some forms of debug information do not reliably indicate whether
21393 a function is prototyped. If @value{GDBN} calls a function that is not marked
21394 as prototyped, it consults @kbd{set coerce-float-to-double}.
21397 @kindex set coerce-float-to-double
21398 @item set coerce-float-to-double
21399 @itemx set coerce-float-to-double on
21400 Arguments of type @code{float} will be promoted to @code{double} when passed
21401 to an unprototyped function. This is the default setting.
21403 @item set coerce-float-to-double off
21404 Arguments of type @code{float} will be passed directly to unprototyped
21407 @kindex show coerce-float-to-double
21408 @item show coerce-float-to-double
21409 Show the current setting of promoting @code{float} to @code{double}.
21413 @kindex show cp-abi
21414 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21415 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21416 used to build your application. @value{GDBN} only fully supports
21417 programs with a single C@t{++} ABI; if your program contains code using
21418 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21419 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21420 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21421 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21422 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21423 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21428 Show the C@t{++} ABI currently in use.
21431 With no argument, show the list of supported C@t{++} ABI's.
21433 @item set cp-abi @var{abi}
21434 @itemx set cp-abi auto
21435 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21439 @section Automatically loading associated files
21440 @cindex auto-loading
21442 @value{GDBN} sometimes reads files with commands and settings automatically,
21443 without being explicitly told so by the user. We call this feature
21444 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21445 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21446 results or introduce security risks (e.g., if the file comes from untrusted
21449 Note that loading of these associated files (including the local @file{.gdbinit}
21450 file) requires accordingly configured @code{auto-load safe-path}
21451 (@pxref{Auto-loading safe path}).
21453 For these reasons, @value{GDBN} includes commands and options to let you
21454 control when to auto-load files and which files should be auto-loaded.
21457 @anchor{set auto-load off}
21458 @kindex set auto-load off
21459 @item set auto-load off
21460 Globally disable loading of all auto-loaded files.
21461 You may want to use this command with the @samp{-iex} option
21462 (@pxref{Option -init-eval-command}) such as:
21464 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21467 Be aware that system init file (@pxref{System-wide configuration})
21468 and init files from your home directory (@pxref{Home Directory Init File})
21469 still get read (as they come from generally trusted directories).
21470 To prevent @value{GDBN} from auto-loading even those init files, use the
21471 @option{-nx} option (@pxref{Mode Options}), in addition to
21472 @code{set auto-load no}.
21474 @anchor{show auto-load}
21475 @kindex show auto-load
21476 @item show auto-load
21477 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21481 (gdb) show auto-load
21482 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21483 libthread-db: Auto-loading of inferior specific libthread_db is on.
21484 local-gdbinit: Auto-loading of .gdbinit script from current directory
21486 python-scripts: Auto-loading of Python scripts is on.
21487 safe-path: List of directories from which it is safe to auto-load files
21488 is $debugdir:$datadir/auto-load.
21489 scripts-directory: List of directories from which to load auto-loaded scripts
21490 is $debugdir:$datadir/auto-load.
21493 @anchor{info auto-load}
21494 @kindex info auto-load
21495 @item info auto-load
21496 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21500 (gdb) info auto-load
21503 Yes /home/user/gdb/gdb-gdb.gdb
21504 libthread-db: No auto-loaded libthread-db.
21505 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21509 Yes /home/user/gdb/gdb-gdb.py
21513 These are various kinds of files @value{GDBN} can automatically load:
21517 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21519 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21521 @xref{dotdebug_gdb_scripts section},
21522 controlled by @ref{set auto-load python-scripts}.
21524 @xref{Init File in the Current Directory},
21525 controlled by @ref{set auto-load local-gdbinit}.
21527 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21530 These are @value{GDBN} control commands for the auto-loading:
21532 @multitable @columnfractions .5 .5
21533 @item @xref{set auto-load off}.
21534 @tab Disable auto-loading globally.
21535 @item @xref{show auto-load}.
21536 @tab Show setting of all kinds of files.
21537 @item @xref{info auto-load}.
21538 @tab Show state of all kinds of files.
21539 @item @xref{set auto-load gdb-scripts}.
21540 @tab Control for @value{GDBN} command scripts.
21541 @item @xref{show auto-load gdb-scripts}.
21542 @tab Show setting of @value{GDBN} command scripts.
21543 @item @xref{info auto-load gdb-scripts}.
21544 @tab Show state of @value{GDBN} command scripts.
21545 @item @xref{set auto-load python-scripts}.
21546 @tab Control for @value{GDBN} Python scripts.
21547 @item @xref{show auto-load python-scripts}.
21548 @tab Show setting of @value{GDBN} Python scripts.
21549 @item @xref{info auto-load python-scripts}.
21550 @tab Show state of @value{GDBN} Python scripts.
21551 @item @xref{set auto-load scripts-directory}.
21552 @tab Control for @value{GDBN} auto-loaded scripts location.
21553 @item @xref{show auto-load scripts-directory}.
21554 @tab Show @value{GDBN} auto-loaded scripts location.
21555 @item @xref{set auto-load local-gdbinit}.
21556 @tab Control for init file in the current directory.
21557 @item @xref{show auto-load local-gdbinit}.
21558 @tab Show setting of init file in the current directory.
21559 @item @xref{info auto-load local-gdbinit}.
21560 @tab Show state of init file in the current directory.
21561 @item @xref{set auto-load libthread-db}.
21562 @tab Control for thread debugging library.
21563 @item @xref{show auto-load libthread-db}.
21564 @tab Show setting of thread debugging library.
21565 @item @xref{info auto-load libthread-db}.
21566 @tab Show state of thread debugging library.
21567 @item @xref{set auto-load safe-path}.
21568 @tab Control directories trusted for automatic loading.
21569 @item @xref{show auto-load safe-path}.
21570 @tab Show directories trusted for automatic loading.
21571 @item @xref{add-auto-load-safe-path}.
21572 @tab Add directory trusted for automatic loading.
21576 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21577 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21578 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21579 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21580 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21581 @xref{Python Auto-loading}.
21584 @node Init File in the Current Directory
21585 @subsection Automatically loading init file in the current directory
21586 @cindex auto-loading init file in the current directory
21588 By default, @value{GDBN} reads and executes the canned sequences of commands
21589 from init file (if any) in the current working directory,
21590 see @ref{Init File in the Current Directory during Startup}.
21592 Note that loading of this local @file{.gdbinit} file also requires accordingly
21593 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21596 @anchor{set auto-load local-gdbinit}
21597 @kindex set auto-load local-gdbinit
21598 @item set auto-load local-gdbinit [on|off]
21599 Enable or disable the auto-loading of canned sequences of commands
21600 (@pxref{Sequences}) found in init file in the current directory.
21602 @anchor{show auto-load local-gdbinit}
21603 @kindex show auto-load local-gdbinit
21604 @item show auto-load local-gdbinit
21605 Show whether auto-loading of canned sequences of commands from init file in the
21606 current directory is enabled or disabled.
21608 @anchor{info auto-load local-gdbinit}
21609 @kindex info auto-load local-gdbinit
21610 @item info auto-load local-gdbinit
21611 Print whether canned sequences of commands from init file in the
21612 current directory have been auto-loaded.
21615 @node libthread_db.so.1 file
21616 @subsection Automatically loading thread debugging library
21617 @cindex auto-loading libthread_db.so.1
21619 This feature is currently present only on @sc{gnu}/Linux native hosts.
21621 @value{GDBN} reads in some cases thread debugging library from places specific
21622 to the inferior (@pxref{set libthread-db-search-path}).
21624 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21625 without checking this @samp{set auto-load libthread-db} switch as system
21626 libraries have to be trusted in general. In all other cases of
21627 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21628 auto-load libthread-db} is enabled before trying to open such thread debugging
21631 Note that loading of this debugging library also requires accordingly configured
21632 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21635 @anchor{set auto-load libthread-db}
21636 @kindex set auto-load libthread-db
21637 @item set auto-load libthread-db [on|off]
21638 Enable or disable the auto-loading of inferior specific thread debugging library.
21640 @anchor{show auto-load libthread-db}
21641 @kindex show auto-load libthread-db
21642 @item show auto-load libthread-db
21643 Show whether auto-loading of inferior specific thread debugging library is
21644 enabled or disabled.
21646 @anchor{info auto-load libthread-db}
21647 @kindex info auto-load libthread-db
21648 @item info auto-load libthread-db
21649 Print the list of all loaded inferior specific thread debugging libraries and
21650 for each such library print list of inferior @var{pid}s using it.
21653 @node objfile-gdb.gdb file
21654 @subsection The @file{@var{objfile}-gdb.gdb} file
21655 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21657 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21658 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21659 auto-load gdb-scripts} is set to @samp{on}.
21661 Note that loading of this script file also requires accordingly configured
21662 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21664 For more background refer to the similar Python scripts auto-loading
21665 description (@pxref{objfile-gdb.py file}).
21668 @anchor{set auto-load gdb-scripts}
21669 @kindex set auto-load gdb-scripts
21670 @item set auto-load gdb-scripts [on|off]
21671 Enable or disable the auto-loading of canned sequences of commands scripts.
21673 @anchor{show auto-load gdb-scripts}
21674 @kindex show auto-load gdb-scripts
21675 @item show auto-load gdb-scripts
21676 Show whether auto-loading of canned sequences of commands scripts is enabled or
21679 @anchor{info auto-load gdb-scripts}
21680 @kindex info auto-load gdb-scripts
21681 @cindex print list of auto-loaded canned sequences of commands scripts
21682 @item info auto-load gdb-scripts [@var{regexp}]
21683 Print the list of all canned sequences of commands scripts that @value{GDBN}
21687 If @var{regexp} is supplied only canned sequences of commands scripts with
21688 matching names are printed.
21690 @node Auto-loading safe path
21691 @subsection Security restriction for auto-loading
21692 @cindex auto-loading safe-path
21694 As the files of inferior can come from untrusted source (such as submitted by
21695 an application user) @value{GDBN} does not always load any files automatically.
21696 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21697 directories trusted for loading files not explicitly requested by user.
21698 Each directory can also be a shell wildcard pattern.
21700 If the path is not set properly you will see a warning and the file will not
21705 Reading symbols from /home/user/gdb/gdb...done.
21706 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21707 declined by your `auto-load safe-path' set
21708 to "$debugdir:$datadir/auto-load".
21709 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21710 declined by your `auto-load safe-path' set
21711 to "$debugdir:$datadir/auto-load".
21714 The list of trusted directories is controlled by the following commands:
21717 @anchor{set auto-load safe-path}
21718 @kindex set auto-load safe-path
21719 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21720 Set the list of directories (and their subdirectories) trusted for automatic
21721 loading and execution of scripts. You can also enter a specific trusted file.
21722 Each directory can also be a shell wildcard pattern; wildcards do not match
21723 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21724 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21725 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21726 its default value as specified during @value{GDBN} compilation.
21728 The list of directories uses path separator (@samp{:} on GNU and Unix
21729 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21730 to the @env{PATH} environment variable.
21732 @anchor{show auto-load safe-path}
21733 @kindex show auto-load safe-path
21734 @item show auto-load safe-path
21735 Show the list of directories trusted for automatic loading and execution of
21738 @anchor{add-auto-load-safe-path}
21739 @kindex add-auto-load-safe-path
21740 @item add-auto-load-safe-path
21741 Add an entry (or list of entries) the list of directories trusted for automatic
21742 loading and execution of scripts. Multiple entries may be delimited by the
21743 host platform path separator in use.
21746 This variable defaults to what @code{--with-auto-load-dir} has been configured
21747 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21748 substitution applies the same as for @ref{set auto-load scripts-directory}.
21749 The default @code{set auto-load safe-path} value can be also overriden by
21750 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21752 Setting this variable to @file{/} disables this security protection,
21753 corresponding @value{GDBN} configuration option is
21754 @option{--without-auto-load-safe-path}.
21755 This variable is supposed to be set to the system directories writable by the
21756 system superuser only. Users can add their source directories in init files in
21757 their home directories (@pxref{Home Directory Init File}). See also deprecated
21758 init file in the current directory
21759 (@pxref{Init File in the Current Directory during Startup}).
21761 To force @value{GDBN} to load the files it declined to load in the previous
21762 example, you could use one of the following ways:
21765 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21766 Specify this trusted directory (or a file) as additional component of the list.
21767 You have to specify also any existing directories displayed by
21768 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21770 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21771 Specify this directory as in the previous case but just for a single
21772 @value{GDBN} session.
21774 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21775 Disable auto-loading safety for a single @value{GDBN} session.
21776 This assumes all the files you debug during this @value{GDBN} session will come
21777 from trusted sources.
21779 @item @kbd{./configure --without-auto-load-safe-path}
21780 During compilation of @value{GDBN} you may disable any auto-loading safety.
21781 This assumes all the files you will ever debug with this @value{GDBN} come from
21785 On the other hand you can also explicitly forbid automatic files loading which
21786 also suppresses any such warning messages:
21789 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21790 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21792 @item @file{~/.gdbinit}: @samp{set auto-load no}
21793 Disable auto-loading globally for the user
21794 (@pxref{Home Directory Init File}). While it is improbable, you could also
21795 use system init file instead (@pxref{System-wide configuration}).
21798 This setting applies to the file names as entered by user. If no entry matches
21799 @value{GDBN} tries as a last resort to also resolve all the file names into
21800 their canonical form (typically resolving symbolic links) and compare the
21801 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21802 own before starting the comparison so a canonical form of directories is
21803 recommended to be entered.
21805 @node Auto-loading verbose mode
21806 @subsection Displaying files tried for auto-load
21807 @cindex auto-loading verbose mode
21809 For better visibility of all the file locations where you can place scripts to
21810 be auto-loaded with inferior --- or to protect yourself against accidental
21811 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21812 all the files attempted to be loaded. Both existing and non-existing files may
21815 For example the list of directories from which it is safe to auto-load files
21816 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21817 may not be too obvious while setting it up.
21820 (gdb) set debug auto-load on
21821 (gdb) file ~/src/t/true
21822 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21823 for objfile "/tmp/true".
21824 auto-load: Updating directories of "/usr:/opt".
21825 auto-load: Using directory "/usr".
21826 auto-load: Using directory "/opt".
21827 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21828 by your `auto-load safe-path' set to "/usr:/opt".
21832 @anchor{set debug auto-load}
21833 @kindex set debug auto-load
21834 @item set debug auto-load [on|off]
21835 Set whether to print the filenames attempted to be auto-loaded.
21837 @anchor{show debug auto-load}
21838 @kindex show debug auto-load
21839 @item show debug auto-load
21840 Show whether printing of the filenames attempted to be auto-loaded is turned
21844 @node Messages/Warnings
21845 @section Optional Warnings and Messages
21847 @cindex verbose operation
21848 @cindex optional warnings
21849 By default, @value{GDBN} is silent about its inner workings. If you are
21850 running on a slow machine, you may want to use the @code{set verbose}
21851 command. This makes @value{GDBN} tell you when it does a lengthy
21852 internal operation, so you will not think it has crashed.
21854 Currently, the messages controlled by @code{set verbose} are those
21855 which announce that the symbol table for a source file is being read;
21856 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
21859 @kindex set verbose
21860 @item set verbose on
21861 Enables @value{GDBN} output of certain informational messages.
21863 @item set verbose off
21864 Disables @value{GDBN} output of certain informational messages.
21866 @kindex show verbose
21868 Displays whether @code{set verbose} is on or off.
21871 By default, if @value{GDBN} encounters bugs in the symbol table of an
21872 object file, it is silent; but if you are debugging a compiler, you may
21873 find this information useful (@pxref{Symbol Errors, ,Errors Reading
21878 @kindex set complaints
21879 @item set complaints @var{limit}
21880 Permits @value{GDBN} to output @var{limit} complaints about each type of
21881 unusual symbols before becoming silent about the problem. Set
21882 @var{limit} to zero to suppress all complaints; set it to a large number
21883 to prevent complaints from being suppressed.
21885 @kindex show complaints
21886 @item show complaints
21887 Displays how many symbol complaints @value{GDBN} is permitted to produce.
21891 @anchor{confirmation requests}
21892 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
21893 lot of stupid questions to confirm certain commands. For example, if
21894 you try to run a program which is already running:
21898 The program being debugged has been started already.
21899 Start it from the beginning? (y or n)
21902 If you are willing to unflinchingly face the consequences of your own
21903 commands, you can disable this ``feature'':
21907 @kindex set confirm
21909 @cindex confirmation
21910 @cindex stupid questions
21911 @item set confirm off
21912 Disables confirmation requests. Note that running @value{GDBN} with
21913 the @option{--batch} option (@pxref{Mode Options, -batch}) also
21914 automatically disables confirmation requests.
21916 @item set confirm on
21917 Enables confirmation requests (the default).
21919 @kindex show confirm
21921 Displays state of confirmation requests.
21925 @cindex command tracing
21926 If you need to debug user-defined commands or sourced files you may find it
21927 useful to enable @dfn{command tracing}. In this mode each command will be
21928 printed as it is executed, prefixed with one or more @samp{+} symbols, the
21929 quantity denoting the call depth of each command.
21932 @kindex set trace-commands
21933 @cindex command scripts, debugging
21934 @item set trace-commands on
21935 Enable command tracing.
21936 @item set trace-commands off
21937 Disable command tracing.
21938 @item show trace-commands
21939 Display the current state of command tracing.
21942 @node Debugging Output
21943 @section Optional Messages about Internal Happenings
21944 @cindex optional debugging messages
21946 @value{GDBN} has commands that enable optional debugging messages from
21947 various @value{GDBN} subsystems; normally these commands are of
21948 interest to @value{GDBN} maintainers, or when reporting a bug. This
21949 section documents those commands.
21952 @kindex set exec-done-display
21953 @item set exec-done-display
21954 Turns on or off the notification of asynchronous commands'
21955 completion. When on, @value{GDBN} will print a message when an
21956 asynchronous command finishes its execution. The default is off.
21957 @kindex show exec-done-display
21958 @item show exec-done-display
21959 Displays the current setting of asynchronous command completion
21962 @cindex gdbarch debugging info
21963 @cindex architecture debugging info
21964 @item set debug arch
21965 Turns on or off display of gdbarch debugging info. The default is off
21967 @item show debug arch
21968 Displays the current state of displaying gdbarch debugging info.
21969 @item set debug aix-thread
21970 @cindex AIX threads
21971 Display debugging messages about inner workings of the AIX thread
21973 @item show debug aix-thread
21974 Show the current state of AIX thread debugging info display.
21975 @item set debug check-physname
21977 Check the results of the ``physname'' computation. When reading DWARF
21978 debugging information for C@t{++}, @value{GDBN} attempts to compute
21979 each entity's name. @value{GDBN} can do this computation in two
21980 different ways, depending on exactly what information is present.
21981 When enabled, this setting causes @value{GDBN} to compute the names
21982 both ways and display any discrepancies.
21983 @item show debug check-physname
21984 Show the current state of ``physname'' checking.
21985 @item set debug dwarf2-die
21986 @cindex DWARF2 DIEs
21987 Dump DWARF2 DIEs after they are read in.
21988 The value is the number of nesting levels to print.
21989 A value of zero turns off the display.
21990 @item show debug dwarf2-die
21991 Show the current state of DWARF2 DIE debugging.
21992 @item set debug dwarf2-read
21993 @cindex DWARF2 Reading
21994 Turns on or off display of debugging messages related to reading
21995 DWARF debug info. The default is off.
21996 @item show debug dwarf2-read
21997 Show the current state of DWARF2 reader debugging.
21998 @item set debug displaced
21999 @cindex displaced stepping debugging info
22000 Turns on or off display of @value{GDBN} debugging info for the
22001 displaced stepping support. The default is off.
22002 @item show debug displaced
22003 Displays the current state of displaying @value{GDBN} debugging info
22004 related to displaced stepping.
22005 @item set debug event
22006 @cindex event debugging info
22007 Turns on or off display of @value{GDBN} event debugging info. The
22009 @item show debug event
22010 Displays the current state of displaying @value{GDBN} event debugging
22012 @item set debug expression
22013 @cindex expression debugging info
22014 Turns on or off display of debugging info about @value{GDBN}
22015 expression parsing. The default is off.
22016 @item show debug expression
22017 Displays the current state of displaying debugging info about
22018 @value{GDBN} expression parsing.
22019 @item set debug frame
22020 @cindex frame debugging info
22021 Turns on or off display of @value{GDBN} frame debugging info. The
22023 @item show debug frame
22024 Displays the current state of displaying @value{GDBN} frame debugging
22026 @item set debug gnu-nat
22027 @cindex @sc{gnu}/Hurd debug messages
22028 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22029 @item show debug gnu-nat
22030 Show the current state of @sc{gnu}/Hurd debugging messages.
22031 @item set debug infrun
22032 @cindex inferior debugging info
22033 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22034 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22035 for implementing operations such as single-stepping the inferior.
22036 @item show debug infrun
22037 Displays the current state of @value{GDBN} inferior debugging.
22038 @item set debug jit
22039 @cindex just-in-time compilation, debugging messages
22040 Turns on or off debugging messages from JIT debug support.
22041 @item show debug jit
22042 Displays the current state of @value{GDBN} JIT debugging.
22043 @item set debug lin-lwp
22044 @cindex @sc{gnu}/Linux LWP debug messages
22045 @cindex Linux lightweight processes
22046 Turns on or off debugging messages from the Linux LWP debug support.
22047 @item show debug lin-lwp
22048 Show the current state of Linux LWP debugging messages.
22049 @item set debug notification
22050 @cindex remote async notification debugging info
22051 Turns on or off debugging messages about remote async notification.
22052 The default is off.
22053 @item show debug notification
22054 Displays the current state of remote async notification debugging messages.
22055 @item set debug observer
22056 @cindex observer debugging info
22057 Turns on or off display of @value{GDBN} observer debugging. This
22058 includes info such as the notification of observable events.
22059 @item show debug observer
22060 Displays the current state of observer debugging.
22061 @item set debug overload
22062 @cindex C@t{++} overload debugging info
22063 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22064 info. This includes info such as ranking of functions, etc. The default
22066 @item show debug overload
22067 Displays the current state of displaying @value{GDBN} C@t{++} overload
22069 @cindex expression parser, debugging info
22070 @cindex debug expression parser
22071 @item set debug parser
22072 Turns on or off the display of expression parser debugging output.
22073 Internally, this sets the @code{yydebug} variable in the expression
22074 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22075 details. The default is off.
22076 @item show debug parser
22077 Show the current state of expression parser debugging.
22078 @cindex packets, reporting on stdout
22079 @cindex serial connections, debugging
22080 @cindex debug remote protocol
22081 @cindex remote protocol debugging
22082 @cindex display remote packets
22083 @item set debug remote
22084 Turns on or off display of reports on all packets sent back and forth across
22085 the serial line to the remote machine. The info is printed on the
22086 @value{GDBN} standard output stream. The default is off.
22087 @item show debug remote
22088 Displays the state of display of remote packets.
22089 @item set debug serial
22090 Turns on or off display of @value{GDBN} serial debugging info. The
22092 @item show debug serial
22093 Displays the current state of displaying @value{GDBN} serial debugging
22095 @item set debug solib-frv
22096 @cindex FR-V shared-library debugging
22097 Turns on or off debugging messages for FR-V shared-library code.
22098 @item show debug solib-frv
22099 Display the current state of FR-V shared-library code debugging
22101 @item set debug symtab-create
22102 @cindex symbol table creation
22103 Turns on or off display of debugging messages related to symbol table creation.
22104 The default is off.
22105 @item show debug symtab-create
22106 Show the current state of symbol table creation debugging.
22107 @item set debug target
22108 @cindex target debugging info
22109 Turns on or off display of @value{GDBN} target debugging info. This info
22110 includes what is going on at the target level of GDB, as it happens. The
22111 default is 0. Set it to 1 to track events, and to 2 to also track the
22112 value of large memory transfers. Changes to this flag do not take effect
22113 until the next time you connect to a target or use the @code{run} command.
22114 @item show debug target
22115 Displays the current state of displaying @value{GDBN} target debugging
22117 @item set debug timestamp
22118 @cindex timestampping debugging info
22119 Turns on or off display of timestamps with @value{GDBN} debugging info.
22120 When enabled, seconds and microseconds are displayed before each debugging
22122 @item show debug timestamp
22123 Displays the current state of displaying timestamps with @value{GDBN}
22125 @item set debugvarobj
22126 @cindex variable object debugging info
22127 Turns on or off display of @value{GDBN} variable object debugging
22128 info. The default is off.
22129 @item show debugvarobj
22130 Displays the current state of displaying @value{GDBN} variable object
22132 @item set debug xml
22133 @cindex XML parser debugging
22134 Turns on or off debugging messages for built-in XML parsers.
22135 @item show debug xml
22136 Displays the current state of XML debugging messages.
22139 @node Other Misc Settings
22140 @section Other Miscellaneous Settings
22141 @cindex miscellaneous settings
22144 @kindex set interactive-mode
22145 @item set interactive-mode
22146 If @code{on}, forces @value{GDBN} to assume that GDB was started
22147 in a terminal. In practice, this means that @value{GDBN} should wait
22148 for the user to answer queries generated by commands entered at
22149 the command prompt. If @code{off}, forces @value{GDBN} to operate
22150 in the opposite mode, and it uses the default answers to all queries.
22151 If @code{auto} (the default), @value{GDBN} tries to determine whether
22152 its standard input is a terminal, and works in interactive-mode if it
22153 is, non-interactively otherwise.
22155 In the vast majority of cases, the debugger should be able to guess
22156 correctly which mode should be used. But this setting can be useful
22157 in certain specific cases, such as running a MinGW @value{GDBN}
22158 inside a cygwin window.
22160 @kindex show interactive-mode
22161 @item show interactive-mode
22162 Displays whether the debugger is operating in interactive mode or not.
22165 @node Extending GDB
22166 @chapter Extending @value{GDBN}
22167 @cindex extending GDB
22169 @value{GDBN} provides three mechanisms for extension. The first is based
22170 on composition of @value{GDBN} commands, the second is based on the
22171 Python scripting language, and the third is for defining new aliases of
22174 To facilitate the use of the first two extensions, @value{GDBN} is capable
22175 of evaluating the contents of a file. When doing so, @value{GDBN}
22176 can recognize which scripting language is being used by looking at
22177 the filename extension. Files with an unrecognized filename extension
22178 are always treated as a @value{GDBN} Command Files.
22179 @xref{Command Files,, Command files}.
22181 You can control how @value{GDBN} evaluates these files with the following
22185 @kindex set script-extension
22186 @kindex show script-extension
22187 @item set script-extension off
22188 All scripts are always evaluated as @value{GDBN} Command Files.
22190 @item set script-extension soft
22191 The debugger determines the scripting language based on filename
22192 extension. If this scripting language is supported, @value{GDBN}
22193 evaluates the script using that language. Otherwise, it evaluates
22194 the file as a @value{GDBN} Command File.
22196 @item set script-extension strict
22197 The debugger determines the scripting language based on filename
22198 extension, and evaluates the script using that language. If the
22199 language is not supported, then the evaluation fails.
22201 @item show script-extension
22202 Display the current value of the @code{script-extension} option.
22207 * Sequences:: Canned Sequences of Commands
22208 * Python:: Scripting @value{GDBN} using Python
22209 * Aliases:: Creating new spellings of existing commands
22213 @section Canned Sequences of Commands
22215 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22216 Command Lists}), @value{GDBN} provides two ways to store sequences of
22217 commands for execution as a unit: user-defined commands and command
22221 * Define:: How to define your own commands
22222 * Hooks:: Hooks for user-defined commands
22223 * Command Files:: How to write scripts of commands to be stored in a file
22224 * Output:: Commands for controlled output
22228 @subsection User-defined Commands
22230 @cindex user-defined command
22231 @cindex arguments, to user-defined commands
22232 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22233 which you assign a new name as a command. This is done with the
22234 @code{define} command. User commands may accept up to 10 arguments
22235 separated by whitespace. Arguments are accessed within the user command
22236 via @code{$arg0@dots{}$arg9}. A trivial example:
22240 print $arg0 + $arg1 + $arg2
22245 To execute the command use:
22252 This defines the command @code{adder}, which prints the sum of
22253 its three arguments. Note the arguments are text substitutions, so they may
22254 reference variables, use complex expressions, or even perform inferior
22257 @cindex argument count in user-defined commands
22258 @cindex how many arguments (user-defined commands)
22259 In addition, @code{$argc} may be used to find out how many arguments have
22260 been passed. This expands to a number in the range 0@dots{}10.
22265 print $arg0 + $arg1
22268 print $arg0 + $arg1 + $arg2
22276 @item define @var{commandname}
22277 Define a command named @var{commandname}. If there is already a command
22278 by that name, you are asked to confirm that you want to redefine it.
22279 @var{commandname} may be a bare command name consisting of letters,
22280 numbers, dashes, and underscores. It may also start with any predefined
22281 prefix command. For example, @samp{define target my-target} creates
22282 a user-defined @samp{target my-target} command.
22284 The definition of the command is made up of other @value{GDBN} command lines,
22285 which are given following the @code{define} command. The end of these
22286 commands is marked by a line containing @code{end}.
22289 @kindex end@r{ (user-defined commands)}
22290 @item document @var{commandname}
22291 Document the user-defined command @var{commandname}, so that it can be
22292 accessed by @code{help}. The command @var{commandname} must already be
22293 defined. This command reads lines of documentation just as @code{define}
22294 reads the lines of the command definition, ending with @code{end}.
22295 After the @code{document} command is finished, @code{help} on command
22296 @var{commandname} displays the documentation you have written.
22298 You may use the @code{document} command again to change the
22299 documentation of a command. Redefining the command with @code{define}
22300 does not change the documentation.
22302 @kindex dont-repeat
22303 @cindex don't repeat command
22305 Used inside a user-defined command, this tells @value{GDBN} that this
22306 command should not be repeated when the user hits @key{RET}
22307 (@pxref{Command Syntax, repeat last command}).
22309 @kindex help user-defined
22310 @item help user-defined
22311 List all user-defined commands and all python commands defined in class
22312 COMAND_USER. The first line of the documentation or docstring is
22317 @itemx show user @var{commandname}
22318 Display the @value{GDBN} commands used to define @var{commandname} (but
22319 not its documentation). If no @var{commandname} is given, display the
22320 definitions for all user-defined commands.
22321 This does not work for user-defined python commands.
22323 @cindex infinite recursion in user-defined commands
22324 @kindex show max-user-call-depth
22325 @kindex set max-user-call-depth
22326 @item show max-user-call-depth
22327 @itemx set max-user-call-depth
22328 The value of @code{max-user-call-depth} controls how many recursion
22329 levels are allowed in user-defined commands before @value{GDBN} suspects an
22330 infinite recursion and aborts the command.
22331 This does not apply to user-defined python commands.
22334 In addition to the above commands, user-defined commands frequently
22335 use control flow commands, described in @ref{Command Files}.
22337 When user-defined commands are executed, the
22338 commands of the definition are not printed. An error in any command
22339 stops execution of the user-defined command.
22341 If used interactively, commands that would ask for confirmation proceed
22342 without asking when used inside a user-defined command. Many @value{GDBN}
22343 commands that normally print messages to say what they are doing omit the
22344 messages when used in a user-defined command.
22347 @subsection User-defined Command Hooks
22348 @cindex command hooks
22349 @cindex hooks, for commands
22350 @cindex hooks, pre-command
22353 You may define @dfn{hooks}, which are a special kind of user-defined
22354 command. Whenever you run the command @samp{foo}, if the user-defined
22355 command @samp{hook-foo} exists, it is executed (with no arguments)
22356 before that command.
22358 @cindex hooks, post-command
22360 A hook may also be defined which is run after the command you executed.
22361 Whenever you run the command @samp{foo}, if the user-defined command
22362 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22363 that command. Post-execution hooks may exist simultaneously with
22364 pre-execution hooks, for the same command.
22366 It is valid for a hook to call the command which it hooks. If this
22367 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22369 @c It would be nice if hookpost could be passed a parameter indicating
22370 @c if the command it hooks executed properly or not. FIXME!
22372 @kindex stop@r{, a pseudo-command}
22373 In addition, a pseudo-command, @samp{stop} exists. Defining
22374 (@samp{hook-stop}) makes the associated commands execute every time
22375 execution stops in your program: before breakpoint commands are run,
22376 displays are printed, or the stack frame is printed.
22378 For example, to ignore @code{SIGALRM} signals while
22379 single-stepping, but treat them normally during normal execution,
22384 handle SIGALRM nopass
22388 handle SIGALRM pass
22391 define hook-continue
22392 handle SIGALRM pass
22396 As a further example, to hook at the beginning and end of the @code{echo}
22397 command, and to add extra text to the beginning and end of the message,
22405 define hookpost-echo
22409 (@value{GDBP}) echo Hello World
22410 <<<---Hello World--->>>
22415 You can define a hook for any single-word command in @value{GDBN}, but
22416 not for command aliases; you should define a hook for the basic command
22417 name, e.g.@: @code{backtrace} rather than @code{bt}.
22418 @c FIXME! So how does Joe User discover whether a command is an alias
22420 You can hook a multi-word command by adding @code{hook-} or
22421 @code{hookpost-} to the last word of the command, e.g.@:
22422 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22424 If an error occurs during the execution of your hook, execution of
22425 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22426 (before the command that you actually typed had a chance to run).
22428 If you try to define a hook which does not match any known command, you
22429 get a warning from the @code{define} command.
22431 @node Command Files
22432 @subsection Command Files
22434 @cindex command files
22435 @cindex scripting commands
22436 A command file for @value{GDBN} is a text file made of lines that are
22437 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22438 also be included. An empty line in a command file does nothing; it
22439 does not mean to repeat the last command, as it would from the
22442 You can request the execution of a command file with the @code{source}
22443 command. Note that the @code{source} command is also used to evaluate
22444 scripts that are not Command Files. The exact behavior can be configured
22445 using the @code{script-extension} setting.
22446 @xref{Extending GDB,, Extending GDB}.
22450 @cindex execute commands from a file
22451 @item source [-s] [-v] @var{filename}
22452 Execute the command file @var{filename}.
22455 The lines in a command file are generally executed sequentially,
22456 unless the order of execution is changed by one of the
22457 @emph{flow-control commands} described below. The commands are not
22458 printed as they are executed. An error in any command terminates
22459 execution of the command file and control is returned to the console.
22461 @value{GDBN} first searches for @var{filename} in the current directory.
22462 If the file is not found there, and @var{filename} does not specify a
22463 directory, then @value{GDBN} also looks for the file on the source search path
22464 (specified with the @samp{directory} command);
22465 except that @file{$cdir} is not searched because the compilation directory
22466 is not relevant to scripts.
22468 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22469 on the search path even if @var{filename} specifies a directory.
22470 The search is done by appending @var{filename} to each element of the
22471 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22472 and the search path contains @file{/home/user} then @value{GDBN} will
22473 look for the script @file{/home/user/mylib/myscript}.
22474 The search is also done if @var{filename} is an absolute path.
22475 For example, if @var{filename} is @file{/tmp/myscript} and
22476 the search path contains @file{/home/user} then @value{GDBN} will
22477 look for the script @file{/home/user/tmp/myscript}.
22478 For DOS-like systems, if @var{filename} contains a drive specification,
22479 it is stripped before concatenation. For example, if @var{filename} is
22480 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22481 will look for the script @file{c:/tmp/myscript}.
22483 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22484 each command as it is executed. The option must be given before
22485 @var{filename}, and is interpreted as part of the filename anywhere else.
22487 Commands that would ask for confirmation if used interactively proceed
22488 without asking when used in a command file. Many @value{GDBN} commands that
22489 normally print messages to say what they are doing omit the messages
22490 when called from command files.
22492 @value{GDBN} also accepts command input from standard input. In this
22493 mode, normal output goes to standard output and error output goes to
22494 standard error. Errors in a command file supplied on standard input do
22495 not terminate execution of the command file---execution continues with
22499 gdb < cmds > log 2>&1
22502 (The syntax above will vary depending on the shell used.) This example
22503 will execute commands from the file @file{cmds}. All output and errors
22504 would be directed to @file{log}.
22506 Since commands stored on command files tend to be more general than
22507 commands typed interactively, they frequently need to deal with
22508 complicated situations, such as different or unexpected values of
22509 variables and symbols, changes in how the program being debugged is
22510 built, etc. @value{GDBN} provides a set of flow-control commands to
22511 deal with these complexities. Using these commands, you can write
22512 complex scripts that loop over data structures, execute commands
22513 conditionally, etc.
22520 This command allows to include in your script conditionally executed
22521 commands. The @code{if} command takes a single argument, which is an
22522 expression to evaluate. It is followed by a series of commands that
22523 are executed only if the expression is true (its value is nonzero).
22524 There can then optionally be an @code{else} line, followed by a series
22525 of commands that are only executed if the expression was false. The
22526 end of the list is marked by a line containing @code{end}.
22530 This command allows to write loops. Its syntax is similar to
22531 @code{if}: the command takes a single argument, which is an expression
22532 to evaluate, and must be followed by the commands to execute, one per
22533 line, terminated by an @code{end}. These commands are called the
22534 @dfn{body} of the loop. The commands in the body of @code{while} are
22535 executed repeatedly as long as the expression evaluates to true.
22539 This command exits the @code{while} loop in whose body it is included.
22540 Execution of the script continues after that @code{while}s @code{end}
22543 @kindex loop_continue
22544 @item loop_continue
22545 This command skips the execution of the rest of the body of commands
22546 in the @code{while} loop in whose body it is included. Execution
22547 branches to the beginning of the @code{while} loop, where it evaluates
22548 the controlling expression.
22550 @kindex end@r{ (if/else/while commands)}
22552 Terminate the block of commands that are the body of @code{if},
22553 @code{else}, or @code{while} flow-control commands.
22558 @subsection Commands for Controlled Output
22560 During the execution of a command file or a user-defined command, normal
22561 @value{GDBN} output is suppressed; the only output that appears is what is
22562 explicitly printed by the commands in the definition. This section
22563 describes three commands useful for generating exactly the output you
22568 @item echo @var{text}
22569 @c I do not consider backslash-space a standard C escape sequence
22570 @c because it is not in ANSI.
22571 Print @var{text}. Nonprinting characters can be included in
22572 @var{text} using C escape sequences, such as @samp{\n} to print a
22573 newline. @strong{No newline is printed unless you specify one.}
22574 In addition to the standard C escape sequences, a backslash followed
22575 by a space stands for a space. This is useful for displaying a
22576 string with spaces at the beginning or the end, since leading and
22577 trailing spaces are otherwise trimmed from all arguments.
22578 To print @samp{@w{ }and foo =@w{ }}, use the command
22579 @samp{echo \@w{ }and foo = \@w{ }}.
22581 A backslash at the end of @var{text} can be used, as in C, to continue
22582 the command onto subsequent lines. For example,
22585 echo This is some text\n\
22586 which is continued\n\
22587 onto several lines.\n
22590 produces the same output as
22593 echo This is some text\n
22594 echo which is continued\n
22595 echo onto several lines.\n
22599 @item output @var{expression}
22600 Print the value of @var{expression} and nothing but that value: no
22601 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22602 value history either. @xref{Expressions, ,Expressions}, for more information
22605 @item output/@var{fmt} @var{expression}
22606 Print the value of @var{expression} in format @var{fmt}. You can use
22607 the same formats as for @code{print}. @xref{Output Formats,,Output
22608 Formats}, for more information.
22611 @item printf @var{template}, @var{expressions}@dots{}
22612 Print the values of one or more @var{expressions} under the control of
22613 the string @var{template}. To print several values, make
22614 @var{expressions} be a comma-separated list of individual expressions,
22615 which may be either numbers or pointers. Their values are printed as
22616 specified by @var{template}, exactly as a C program would do by
22617 executing the code below:
22620 printf (@var{template}, @var{expressions}@dots{});
22623 As in @code{C} @code{printf}, ordinary characters in @var{template}
22624 are printed verbatim, while @dfn{conversion specification} introduced
22625 by the @samp{%} character cause subsequent @var{expressions} to be
22626 evaluated, their values converted and formatted according to type and
22627 style information encoded in the conversion specifications, and then
22630 For example, you can print two values in hex like this:
22633 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22636 @code{printf} supports all the standard @code{C} conversion
22637 specifications, including the flags and modifiers between the @samp{%}
22638 character and the conversion letter, with the following exceptions:
22642 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22645 The modifier @samp{*} is not supported for specifying precision or
22649 The @samp{'} flag (for separation of digits into groups according to
22650 @code{LC_NUMERIC'}) is not supported.
22653 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22657 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22660 The conversion letters @samp{a} and @samp{A} are not supported.
22664 Note that the @samp{ll} type modifier is supported only if the
22665 underlying @code{C} implementation used to build @value{GDBN} supports
22666 the @code{long long int} type, and the @samp{L} type modifier is
22667 supported only if @code{long double} type is available.
22669 As in @code{C}, @code{printf} supports simple backslash-escape
22670 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22671 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22672 single character. Octal and hexadecimal escape sequences are not
22675 Additionally, @code{printf} supports conversion specifications for DFP
22676 (@dfn{Decimal Floating Point}) types using the following length modifiers
22677 together with a floating point specifier.
22682 @samp{H} for printing @code{Decimal32} types.
22685 @samp{D} for printing @code{Decimal64} types.
22688 @samp{DD} for printing @code{Decimal128} types.
22691 If the underlying @code{C} implementation used to build @value{GDBN} has
22692 support for the three length modifiers for DFP types, other modifiers
22693 such as width and precision will also be available for @value{GDBN} to use.
22695 In case there is no such @code{C} support, no additional modifiers will be
22696 available and the value will be printed in the standard way.
22698 Here's an example of printing DFP types using the above conversion letters:
22700 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22704 @item eval @var{template}, @var{expressions}@dots{}
22705 Convert the values of one or more @var{expressions} under the control of
22706 the string @var{template} to a command line, and call it.
22711 @section Scripting @value{GDBN} using Python
22712 @cindex python scripting
22713 @cindex scripting with python
22715 You can script @value{GDBN} using the @uref{http://www.python.org/,
22716 Python programming language}. This feature is available only if
22717 @value{GDBN} was configured using @option{--with-python}.
22719 @cindex python directory
22720 Python scripts used by @value{GDBN} should be installed in
22721 @file{@var{data-directory}/python}, where @var{data-directory} is
22722 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22723 This directory, known as the @dfn{python directory},
22724 is automatically added to the Python Search Path in order to allow
22725 the Python interpreter to locate all scripts installed at this location.
22727 Additionally, @value{GDBN} commands and convenience functions which
22728 are written in Python and are located in the
22729 @file{@var{data-directory}/python/gdb/command} or
22730 @file{@var{data-directory}/python/gdb/function} directories are
22731 automatically imported when @value{GDBN} starts.
22734 * Python Commands:: Accessing Python from @value{GDBN}.
22735 * Python API:: Accessing @value{GDBN} from Python.
22736 * Python Auto-loading:: Automatically loading Python code.
22737 * Python modules:: Python modules provided by @value{GDBN}.
22740 @node Python Commands
22741 @subsection Python Commands
22742 @cindex python commands
22743 @cindex commands to access python
22745 @value{GDBN} provides two commands for accessing the Python interpreter,
22746 and one related setting:
22749 @kindex python-interactive
22751 @item python-interactive @r{[}@var{command}@r{]}
22752 @itemx pi @r{[}@var{command}@r{]}
22753 Without an argument, the @code{python-interactive} command can be used
22754 to start an interactive Python prompt. To return to @value{GDBN},
22755 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22757 Alternatively, a single-line Python command can be given as an
22758 argument and evaluated. If the command is an expression, the result
22759 will be printed; otherwise, nothing will be printed. For example:
22762 (@value{GDBP}) python-interactive 2 + 3
22768 @item python @r{[}@var{command}@r{]}
22769 @itemx py @r{[}@var{command}@r{]}
22770 The @code{python} command can be used to evaluate Python code.
22772 If given an argument, the @code{python} command will evaluate the
22773 argument as a Python command. For example:
22776 (@value{GDBP}) python print 23
22780 If you do not provide an argument to @code{python}, it will act as a
22781 multi-line command, like @code{define}. In this case, the Python
22782 script is made up of subsequent command lines, given after the
22783 @code{python} command. This command list is terminated using a line
22784 containing @code{end}. For example:
22787 (@value{GDBP}) python
22789 End with a line saying just "end".
22795 @kindex set python print-stack
22796 @item set python print-stack
22797 By default, @value{GDBN} will print only the message component of a
22798 Python exception when an error occurs in a Python script. This can be
22799 controlled using @code{set python print-stack}: if @code{full}, then
22800 full Python stack printing is enabled; if @code{none}, then Python stack
22801 and message printing is disabled; if @code{message}, the default, only
22802 the message component of the error is printed.
22805 It is also possible to execute a Python script from the @value{GDBN}
22809 @item source @file{script-name}
22810 The script name must end with @samp{.py} and @value{GDBN} must be configured
22811 to recognize the script language based on filename extension using
22812 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22814 @item python execfile ("script-name")
22815 This method is based on the @code{execfile} Python built-in function,
22816 and thus is always available.
22820 @subsection Python API
22822 @cindex programming in python
22824 @cindex python stdout
22825 @cindex python pagination
22826 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22827 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22828 A Python program which outputs to one of these streams may have its
22829 output interrupted by the user (@pxref{Screen Size}). In this
22830 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22833 * Basic Python:: Basic Python Functions.
22834 * Exception Handling:: How Python exceptions are translated.
22835 * Values From Inferior:: Python representation of values.
22836 * Types In Python:: Python representation of types.
22837 * Pretty Printing API:: Pretty-printing values.
22838 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
22839 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
22840 * Type Printing API:: Pretty-printing types.
22841 * Inferiors In Python:: Python representation of inferiors (processes)
22842 * Events In Python:: Listening for events from @value{GDBN}.
22843 * Threads In Python:: Accessing inferior threads from Python.
22844 * Commands In Python:: Implementing new commands in Python.
22845 * Parameters In Python:: Adding new @value{GDBN} parameters.
22846 * Functions In Python:: Writing new convenience functions.
22847 * Progspaces In Python:: Program spaces.
22848 * Objfiles In Python:: Object files.
22849 * Frames In Python:: Accessing inferior stack frames from Python.
22850 * Blocks In Python:: Accessing frame blocks from Python.
22851 * Symbols In Python:: Python representation of symbols.
22852 * Symbol Tables In Python:: Python representation of symbol tables.
22853 * Breakpoints In Python:: Manipulating breakpoints using Python.
22854 * Finish Breakpoints in Python:: Setting Breakpoints on function return
22856 * Lazy Strings In Python:: Python representation of lazy strings.
22857 * Architectures In Python:: Python representation of architectures.
22861 @subsubsection Basic Python
22863 @cindex python functions
22864 @cindex python module
22866 @value{GDBN} introduces a new Python module, named @code{gdb}. All
22867 methods and classes added by @value{GDBN} are placed in this module.
22868 @value{GDBN} automatically @code{import}s the @code{gdb} module for
22869 use in all scripts evaluated by the @code{python} command.
22871 @findex gdb.PYTHONDIR
22872 @defvar gdb.PYTHONDIR
22873 A string containing the python directory (@pxref{Python}).
22876 @findex gdb.execute
22877 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
22878 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
22879 If a GDB exception happens while @var{command} runs, it is
22880 translated as described in @ref{Exception Handling,,Exception Handling}.
22882 @var{from_tty} specifies whether @value{GDBN} ought to consider this
22883 command as having originated from the user invoking it interactively.
22884 It must be a boolean value. If omitted, it defaults to @code{False}.
22886 By default, any output produced by @var{command} is sent to
22887 @value{GDBN}'s standard output. If the @var{to_string} parameter is
22888 @code{True}, then output will be collected by @code{gdb.execute} and
22889 returned as a string. The default is @code{False}, in which case the
22890 return value is @code{None}. If @var{to_string} is @code{True}, the
22891 @value{GDBN} virtual terminal will be temporarily set to unlimited width
22892 and height, and its pagination will be disabled; @pxref{Screen Size}.
22895 @findex gdb.breakpoints
22896 @defun gdb.breakpoints ()
22897 Return a sequence holding all of @value{GDBN}'s breakpoints.
22898 @xref{Breakpoints In Python}, for more information.
22901 @findex gdb.parameter
22902 @defun gdb.parameter (parameter)
22903 Return the value of a @value{GDBN} parameter. @var{parameter} is a
22904 string naming the parameter to look up; @var{parameter} may contain
22905 spaces if the parameter has a multi-part name. For example,
22906 @samp{print object} is a valid parameter name.
22908 If the named parameter does not exist, this function throws a
22909 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
22910 parameter's value is converted to a Python value of the appropriate
22911 type, and returned.
22914 @findex gdb.history
22915 @defun gdb.history (number)
22916 Return a value from @value{GDBN}'s value history (@pxref{Value
22917 History}). @var{number} indicates which history element to return.
22918 If @var{number} is negative, then @value{GDBN} will take its absolute value
22919 and count backward from the last element (i.e., the most recent element) to
22920 find the value to return. If @var{number} is zero, then @value{GDBN} will
22921 return the most recent element. If the element specified by @var{number}
22922 doesn't exist in the value history, a @code{gdb.error} exception will be
22925 If no exception is raised, the return value is always an instance of
22926 @code{gdb.Value} (@pxref{Values From Inferior}).
22929 @findex gdb.parse_and_eval
22930 @defun gdb.parse_and_eval (expression)
22931 Parse @var{expression} as an expression in the current language,
22932 evaluate it, and return the result as a @code{gdb.Value}.
22933 @var{expression} must be a string.
22935 This function can be useful when implementing a new command
22936 (@pxref{Commands In Python}), as it provides a way to parse the
22937 command's argument as an expression. It is also useful simply to
22938 compute values, for example, it is the only way to get the value of a
22939 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
22942 @findex gdb.find_pc_line
22943 @defun gdb.find_pc_line (pc)
22944 Return the @code{gdb.Symtab_and_line} object corresponding to the
22945 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
22946 value of @var{pc} is passed as an argument, then the @code{symtab} and
22947 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
22948 will be @code{None} and 0 respectively.
22951 @findex gdb.post_event
22952 @defun gdb.post_event (event)
22953 Put @var{event}, a callable object taking no arguments, into
22954 @value{GDBN}'s internal event queue. This callable will be invoked at
22955 some later point, during @value{GDBN}'s event processing. Events
22956 posted using @code{post_event} will be run in the order in which they
22957 were posted; however, there is no way to know when they will be
22958 processed relative to other events inside @value{GDBN}.
22960 @value{GDBN} is not thread-safe. If your Python program uses multiple
22961 threads, you must be careful to only call @value{GDBN}-specific
22962 functions in the main @value{GDBN} thread. @code{post_event} ensures
22966 (@value{GDBP}) python
22970 > def __init__(self, message):
22971 > self.message = message;
22972 > def __call__(self):
22973 > gdb.write(self.message)
22975 >class MyThread1 (threading.Thread):
22977 > gdb.post_event(Writer("Hello "))
22979 >class MyThread2 (threading.Thread):
22981 > gdb.post_event(Writer("World\n"))
22983 >MyThread1().start()
22984 >MyThread2().start()
22986 (@value{GDBP}) Hello World
22991 @defun gdb.write (string @r{[}, stream{]})
22992 Print a string to @value{GDBN}'s paginated output stream. The
22993 optional @var{stream} determines the stream to print to. The default
22994 stream is @value{GDBN}'s standard output stream. Possible stream
23001 @value{GDBN}'s standard output stream.
23006 @value{GDBN}'s standard error stream.
23011 @value{GDBN}'s log stream (@pxref{Logging Output}).
23014 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23015 call this function and will automatically direct the output to the
23020 @defun gdb.flush ()
23021 Flush the buffer of a @value{GDBN} paginated stream so that the
23022 contents are displayed immediately. @value{GDBN} will flush the
23023 contents of a stream automatically when it encounters a newline in the
23024 buffer. The optional @var{stream} determines the stream to flush. The
23025 default stream is @value{GDBN}'s standard output stream. Possible
23032 @value{GDBN}'s standard output stream.
23037 @value{GDBN}'s standard error stream.
23042 @value{GDBN}'s log stream (@pxref{Logging Output}).
23046 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23047 call this function for the relevant stream.
23050 @findex gdb.target_charset
23051 @defun gdb.target_charset ()
23052 Return the name of the current target character set (@pxref{Character
23053 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23054 that @samp{auto} is never returned.
23057 @findex gdb.target_wide_charset
23058 @defun gdb.target_wide_charset ()
23059 Return the name of the current target wide character set
23060 (@pxref{Character Sets}). This differs from
23061 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23065 @findex gdb.solib_name
23066 @defun gdb.solib_name (address)
23067 Return the name of the shared library holding the given @var{address}
23068 as a string, or @code{None}.
23071 @findex gdb.decode_line
23072 @defun gdb.decode_line @r{[}expression@r{]}
23073 Return locations of the line specified by @var{expression}, or of the
23074 current line if no argument was given. This function returns a Python
23075 tuple containing two elements. The first element contains a string
23076 holding any unparsed section of @var{expression} (or @code{None} if
23077 the expression has been fully parsed). The second element contains
23078 either @code{None} or another tuple that contains all the locations
23079 that match the expression represented as @code{gdb.Symtab_and_line}
23080 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23081 provided, it is decoded the way that @value{GDBN}'s inbuilt
23082 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23085 @defun gdb.prompt_hook (current_prompt)
23086 @anchor{prompt_hook}
23088 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23089 assigned to this operation before a prompt is displayed by
23092 The parameter @code{current_prompt} contains the current @value{GDBN}
23093 prompt. This method must return a Python string, or @code{None}. If
23094 a string is returned, the @value{GDBN} prompt will be set to that
23095 string. If @code{None} is returned, @value{GDBN} will continue to use
23096 the current prompt.
23098 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23099 such as those used by readline for command input, and annotation
23100 related prompts are prohibited from being changed.
23103 @node Exception Handling
23104 @subsubsection Exception Handling
23105 @cindex python exceptions
23106 @cindex exceptions, python
23108 When executing the @code{python} command, Python exceptions
23109 uncaught within the Python code are translated to calls to
23110 @value{GDBN} error-reporting mechanism. If the command that called
23111 @code{python} does not handle the error, @value{GDBN} will
23112 terminate it and print an error message containing the Python
23113 exception name, the associated value, and the Python call stack
23114 backtrace at the point where the exception was raised. Example:
23117 (@value{GDBP}) python print foo
23118 Traceback (most recent call last):
23119 File "<string>", line 1, in <module>
23120 NameError: name 'foo' is not defined
23123 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23124 Python code are converted to Python exceptions. The type of the
23125 Python exception depends on the error.
23129 This is the base class for most exceptions generated by @value{GDBN}.
23130 It is derived from @code{RuntimeError}, for compatibility with earlier
23131 versions of @value{GDBN}.
23133 If an error occurring in @value{GDBN} does not fit into some more
23134 specific category, then the generated exception will have this type.
23136 @item gdb.MemoryError
23137 This is a subclass of @code{gdb.error} which is thrown when an
23138 operation tried to access invalid memory in the inferior.
23140 @item KeyboardInterrupt
23141 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23142 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23145 In all cases, your exception handler will see the @value{GDBN} error
23146 message as its value and the Python call stack backtrace at the Python
23147 statement closest to where the @value{GDBN} error occured as the
23150 @findex gdb.GdbError
23151 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23152 it is useful to be able to throw an exception that doesn't cause a
23153 traceback to be printed. For example, the user may have invoked the
23154 command incorrectly. Use the @code{gdb.GdbError} exception
23155 to handle this case. Example:
23159 >class HelloWorld (gdb.Command):
23160 > """Greet the whole world."""
23161 > def __init__ (self):
23162 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23163 > def invoke (self, args, from_tty):
23164 > argv = gdb.string_to_argv (args)
23165 > if len (argv) != 0:
23166 > raise gdb.GdbError ("hello-world takes no arguments")
23167 > print "Hello, World!"
23170 (gdb) hello-world 42
23171 hello-world takes no arguments
23174 @node Values From Inferior
23175 @subsubsection Values From Inferior
23176 @cindex values from inferior, with Python
23177 @cindex python, working with values from inferior
23179 @cindex @code{gdb.Value}
23180 @value{GDBN} provides values it obtains from the inferior program in
23181 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23182 for its internal bookkeeping of the inferior's values, and for
23183 fetching values when necessary.
23185 Inferior values that are simple scalars can be used directly in
23186 Python expressions that are valid for the value's data type. Here's
23187 an example for an integer or floating-point value @code{some_val}:
23194 As result of this, @code{bar} will also be a @code{gdb.Value} object
23195 whose values are of the same type as those of @code{some_val}.
23197 Inferior values that are structures or instances of some class can
23198 be accessed using the Python @dfn{dictionary syntax}. For example, if
23199 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23200 can access its @code{foo} element with:
23203 bar = some_val['foo']
23206 Again, @code{bar} will also be a @code{gdb.Value} object.
23208 A @code{gdb.Value} that represents a function can be executed via
23209 inferior function call. Any arguments provided to the call must match
23210 the function's prototype, and must be provided in the order specified
23213 For example, @code{some_val} is a @code{gdb.Value} instance
23214 representing a function that takes two integers as arguments. To
23215 execute this function, call it like so:
23218 result = some_val (10,20)
23221 Any values returned from a function call will be stored as a
23224 The following attributes are provided:
23226 @defvar Value.address
23227 If this object is addressable, this read-only attribute holds a
23228 @code{gdb.Value} object representing the address. Otherwise,
23229 this attribute holds @code{None}.
23232 @cindex optimized out value in Python
23233 @defvar Value.is_optimized_out
23234 This read-only boolean attribute is true if the compiler optimized out
23235 this value, thus it is not available for fetching from the inferior.
23239 The type of this @code{gdb.Value}. The value of this attribute is a
23240 @code{gdb.Type} object (@pxref{Types In Python}).
23243 @defvar Value.dynamic_type
23244 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23245 type information (@acronym{RTTI}) to determine the dynamic type of the
23246 value. If this value is of class type, it will return the class in
23247 which the value is embedded, if any. If this value is of pointer or
23248 reference to a class type, it will compute the dynamic type of the
23249 referenced object, and return a pointer or reference to that type,
23250 respectively. In all other cases, it will return the value's static
23253 Note that this feature will only work when debugging a C@t{++} program
23254 that includes @acronym{RTTI} for the object in question. Otherwise,
23255 it will just return the static type of the value as in @kbd{ptype foo}
23256 (@pxref{Symbols, ptype}).
23259 @defvar Value.is_lazy
23260 The value of this read-only boolean attribute is @code{True} if this
23261 @code{gdb.Value} has not yet been fetched from the inferior.
23262 @value{GDBN} does not fetch values until necessary, for efficiency.
23266 myval = gdb.parse_and_eval ('somevar')
23269 The value of @code{somevar} is not fetched at this time. It will be
23270 fetched when the value is needed, or when the @code{fetch_lazy}
23274 The following methods are provided:
23276 @defun Value.__init__ (@var{val})
23277 Many Python values can be converted directly to a @code{gdb.Value} via
23278 this object initializer. Specifically:
23281 @item Python boolean
23282 A Python boolean is converted to the boolean type from the current
23285 @item Python integer
23286 A Python integer is converted to the C @code{long} type for the
23287 current architecture.
23290 A Python long is converted to the C @code{long long} type for the
23291 current architecture.
23294 A Python float is converted to the C @code{double} type for the
23295 current architecture.
23297 @item Python string
23298 A Python string is converted to a target string, using the current
23301 @item @code{gdb.Value}
23302 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23304 @item @code{gdb.LazyString}
23305 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23306 Python}), then the lazy string's @code{value} method is called, and
23307 its result is used.
23311 @defun Value.cast (type)
23312 Return a new instance of @code{gdb.Value} that is the result of
23313 casting this instance to the type described by @var{type}, which must
23314 be a @code{gdb.Type} object. If the cast cannot be performed for some
23315 reason, this method throws an exception.
23318 @defun Value.dereference ()
23319 For pointer data types, this method returns a new @code{gdb.Value} object
23320 whose contents is the object pointed to by the pointer. For example, if
23321 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23328 then you can use the corresponding @code{gdb.Value} to access what
23329 @code{foo} points to like this:
23332 bar = foo.dereference ()
23335 The result @code{bar} will be a @code{gdb.Value} object holding the
23336 value pointed to by @code{foo}.
23338 A similar function @code{Value.referenced_value} exists which also
23339 returns @code{gdb.Value} objects corresonding to the values pointed to
23340 by pointer values (and additionally, values referenced by reference
23341 values). However, the behavior of @code{Value.dereference}
23342 differs from @code{Value.referenced_value} by the fact that the
23343 behavior of @code{Value.dereference} is identical to applying the C
23344 unary operator @code{*} on a given value. For example, consider a
23345 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23349 typedef int *intptr;
23353 intptr &ptrref = ptr;
23356 Though @code{ptrref} is a reference value, one can apply the method
23357 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23358 to it and obtain a @code{gdb.Value} which is identical to that
23359 corresponding to @code{val}. However, if you apply the method
23360 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23361 object identical to that corresponding to @code{ptr}.
23364 py_ptrref = gdb.parse_and_eval ("ptrref")
23365 py_val = py_ptrref.dereference ()
23366 py_ptr = py_ptrref.referenced_value ()
23369 The @code{gdb.Value} object @code{py_val} is identical to that
23370 corresponding to @code{val}, and @code{py_ptr} is identical to that
23371 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23372 be applied whenever the C unary operator @code{*} can be applied
23373 to the corresponding C value. For those cases where applying both
23374 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23375 the results obtained need not be identical (as we have seen in the above
23376 example). The results are however identical when applied on
23377 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23378 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23381 @defun Value.referenced_value ()
23382 For pointer or reference data types, this method returns a new
23383 @code{gdb.Value} object corresponding to the value referenced by the
23384 pointer/reference value. For pointer data types,
23385 @code{Value.dereference} and @code{Value.referenced_value} produce
23386 identical results. The difference between these methods is that
23387 @code{Value.dereference} cannot get the values referenced by reference
23388 values. For example, consider a reference to an @code{int}, declared
23389 in your C@t{++} program as
23397 then applying @code{Value.dereference} to the @code{gdb.Value} object
23398 corresponding to @code{ref} will result in an error, while applying
23399 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23400 identical to that corresponding to @code{val}.
23403 py_ref = gdb.parse_and_eval ("ref")
23404 er_ref = py_ref.dereference () # Results in error
23405 py_val = py_ref.referenced_value () # Returns the referenced value
23408 The @code{gdb.Value} object @code{py_val} is identical to that
23409 corresponding to @code{val}.
23412 @defun Value.dynamic_cast (type)
23413 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23414 operator were used. Consult a C@t{++} reference for details.
23417 @defun Value.reinterpret_cast (type)
23418 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23419 operator were used. Consult a C@t{++} reference for details.
23422 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23423 If this @code{gdb.Value} represents a string, then this method
23424 converts the contents to a Python string. Otherwise, this method will
23425 throw an exception.
23427 Strings are recognized in a language-specific way; whether a given
23428 @code{gdb.Value} represents a string is determined by the current
23431 For C-like languages, a value is a string if it is a pointer to or an
23432 array of characters or ints. The string is assumed to be terminated
23433 by a zero of the appropriate width. However if the optional length
23434 argument is given, the string will be converted to that given length,
23435 ignoring any embedded zeros that the string may contain.
23437 If the optional @var{encoding} argument is given, it must be a string
23438 naming the encoding of the string in the @code{gdb.Value}, such as
23439 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23440 the same encodings as the corresponding argument to Python's
23441 @code{string.decode} method, and the Python codec machinery will be used
23442 to convert the string. If @var{encoding} is not given, or if
23443 @var{encoding} is the empty string, then either the @code{target-charset}
23444 (@pxref{Character Sets}) will be used, or a language-specific encoding
23445 will be used, if the current language is able to supply one.
23447 The optional @var{errors} argument is the same as the corresponding
23448 argument to Python's @code{string.decode} method.
23450 If the optional @var{length} argument is given, the string will be
23451 fetched and converted to the given length.
23454 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23455 If this @code{gdb.Value} represents a string, then this method
23456 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23457 In Python}). Otherwise, this method will throw an exception.
23459 If the optional @var{encoding} argument is given, it must be a string
23460 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23461 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23462 @var{encoding} argument is an encoding that @value{GDBN} does
23463 recognize, @value{GDBN} will raise an error.
23465 When a lazy string is printed, the @value{GDBN} encoding machinery is
23466 used to convert the string during printing. If the optional
23467 @var{encoding} argument is not provided, or is an empty string,
23468 @value{GDBN} will automatically select the encoding most suitable for
23469 the string type. For further information on encoding in @value{GDBN}
23470 please see @ref{Character Sets}.
23472 If the optional @var{length} argument is given, the string will be
23473 fetched and encoded to the length of characters specified. If
23474 the @var{length} argument is not provided, the string will be fetched
23475 and encoded until a null of appropriate width is found.
23478 @defun Value.fetch_lazy ()
23479 If the @code{gdb.Value} object is currently a lazy value
23480 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23481 fetched from the inferior. Any errors that occur in the process
23482 will produce a Python exception.
23484 If the @code{gdb.Value} object is not a lazy value, this method
23487 This method does not return a value.
23491 @node Types In Python
23492 @subsubsection Types In Python
23493 @cindex types in Python
23494 @cindex Python, working with types
23497 @value{GDBN} represents types from the inferior using the class
23500 The following type-related functions are available in the @code{gdb}
23503 @findex gdb.lookup_type
23504 @defun gdb.lookup_type (name @r{[}, block@r{]})
23505 This function looks up a type by name. @var{name} is the name of the
23506 type to look up. It must be a string.
23508 If @var{block} is given, then @var{name} is looked up in that scope.
23509 Otherwise, it is searched for globally.
23511 Ordinarily, this function will return an instance of @code{gdb.Type}.
23512 If the named type cannot be found, it will throw an exception.
23515 If the type is a structure or class type, or an enum type, the fields
23516 of that type can be accessed using the Python @dfn{dictionary syntax}.
23517 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23518 a structure type, you can access its @code{foo} field with:
23521 bar = some_type['foo']
23524 @code{bar} will be a @code{gdb.Field} object; see below under the
23525 description of the @code{Type.fields} method for a description of the
23526 @code{gdb.Field} class.
23528 An instance of @code{Type} has the following attributes:
23531 The type code for this type. The type code will be one of the
23532 @code{TYPE_CODE_} constants defined below.
23535 @defvar Type.sizeof
23536 The size of this type, in target @code{char} units. Usually, a
23537 target's @code{char} type will be an 8-bit byte. However, on some
23538 unusual platforms, this type may have a different size.
23542 The tag name for this type. The tag name is the name after
23543 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23544 languages have this concept. If this type has no tag name, then
23545 @code{None} is returned.
23548 The following methods are provided:
23550 @defun Type.fields ()
23551 For structure and union types, this method returns the fields. Range
23552 types have two fields, the minimum and maximum values. Enum types
23553 have one field per enum constant. Function and method types have one
23554 field per parameter. The base types of C@t{++} classes are also
23555 represented as fields. If the type has no fields, or does not fit
23556 into one of these categories, an empty sequence will be returned.
23558 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23561 This attribute is not available for @code{static} fields (as in
23562 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23563 position of the field. For @code{enum} fields, the value is the
23564 enumeration member's integer representation.
23567 The name of the field, or @code{None} for anonymous fields.
23570 This is @code{True} if the field is artificial, usually meaning that
23571 it was provided by the compiler and not the user. This attribute is
23572 always provided, and is @code{False} if the field is not artificial.
23574 @item is_base_class
23575 This is @code{True} if the field represents a base class of a C@t{++}
23576 structure. This attribute is always provided, and is @code{False}
23577 if the field is not a base class of the type that is the argument of
23578 @code{fields}, or if that type was not a C@t{++} class.
23581 If the field is packed, or is a bitfield, then this will have a
23582 non-zero value, which is the size of the field in bits. Otherwise,
23583 this will be zero; in this case the field's size is given by its type.
23586 The type of the field. This is usually an instance of @code{Type},
23587 but it can be @code{None} in some situations.
23591 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23592 Return a new @code{gdb.Type} object which represents an array of this
23593 type. If one argument is given, it is the inclusive upper bound of
23594 the array; in this case the lower bound is zero. If two arguments are
23595 given, the first argument is the lower bound of the array, and the
23596 second argument is the upper bound of the array. An array's length
23597 must not be negative, but the bounds can be.
23600 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23601 Return a new @code{gdb.Type} object which represents a vector of this
23602 type. If one argument is given, it is the inclusive upper bound of
23603 the vector; in this case the lower bound is zero. If two arguments are
23604 given, the first argument is the lower bound of the vector, and the
23605 second argument is the upper bound of the vector. A vector's length
23606 must not be negative, but the bounds can be.
23608 The difference between an @code{array} and a @code{vector} is that
23609 arrays behave like in C: when used in expressions they decay to a pointer
23610 to the first element whereas vectors are treated as first class values.
23613 @defun Type.const ()
23614 Return a new @code{gdb.Type} object which represents a
23615 @code{const}-qualified variant of this type.
23618 @defun Type.volatile ()
23619 Return a new @code{gdb.Type} object which represents a
23620 @code{volatile}-qualified variant of this type.
23623 @defun Type.unqualified ()
23624 Return a new @code{gdb.Type} object which represents an unqualified
23625 variant of this type. That is, the result is neither @code{const} nor
23629 @defun Type.range ()
23630 Return a Python @code{Tuple} object that contains two elements: the
23631 low bound of the argument type and the high bound of that type. If
23632 the type does not have a range, @value{GDBN} will raise a
23633 @code{gdb.error} exception (@pxref{Exception Handling}).
23636 @defun Type.reference ()
23637 Return a new @code{gdb.Type} object which represents a reference to this
23641 @defun Type.pointer ()
23642 Return a new @code{gdb.Type} object which represents a pointer to this
23646 @defun Type.strip_typedefs ()
23647 Return a new @code{gdb.Type} that represents the real type,
23648 after removing all layers of typedefs.
23651 @defun Type.target ()
23652 Return a new @code{gdb.Type} object which represents the target type
23655 For a pointer type, the target type is the type of the pointed-to
23656 object. For an array type (meaning C-like arrays), the target type is
23657 the type of the elements of the array. For a function or method type,
23658 the target type is the type of the return value. For a complex type,
23659 the target type is the type of the elements. For a typedef, the
23660 target type is the aliased type.
23662 If the type does not have a target, this method will throw an
23666 @defun Type.template_argument (n @r{[}, block@r{]})
23667 If this @code{gdb.Type} is an instantiation of a template, this will
23668 return a new @code{gdb.Type} which represents the type of the
23669 @var{n}th template argument.
23671 If this @code{gdb.Type} is not a template type, this will throw an
23672 exception. Ordinarily, only C@t{++} code will have template types.
23674 If @var{block} is given, then @var{name} is looked up in that scope.
23675 Otherwise, it is searched for globally.
23679 Each type has a code, which indicates what category this type falls
23680 into. The available type categories are represented by constants
23681 defined in the @code{gdb} module:
23684 @findex TYPE_CODE_PTR
23685 @findex gdb.TYPE_CODE_PTR
23686 @item gdb.TYPE_CODE_PTR
23687 The type is a pointer.
23689 @findex TYPE_CODE_ARRAY
23690 @findex gdb.TYPE_CODE_ARRAY
23691 @item gdb.TYPE_CODE_ARRAY
23692 The type is an array.
23694 @findex TYPE_CODE_STRUCT
23695 @findex gdb.TYPE_CODE_STRUCT
23696 @item gdb.TYPE_CODE_STRUCT
23697 The type is a structure.
23699 @findex TYPE_CODE_UNION
23700 @findex gdb.TYPE_CODE_UNION
23701 @item gdb.TYPE_CODE_UNION
23702 The type is a union.
23704 @findex TYPE_CODE_ENUM
23705 @findex gdb.TYPE_CODE_ENUM
23706 @item gdb.TYPE_CODE_ENUM
23707 The type is an enum.
23709 @findex TYPE_CODE_FLAGS
23710 @findex gdb.TYPE_CODE_FLAGS
23711 @item gdb.TYPE_CODE_FLAGS
23712 A bit flags type, used for things such as status registers.
23714 @findex TYPE_CODE_FUNC
23715 @findex gdb.TYPE_CODE_FUNC
23716 @item gdb.TYPE_CODE_FUNC
23717 The type is a function.
23719 @findex TYPE_CODE_INT
23720 @findex gdb.TYPE_CODE_INT
23721 @item gdb.TYPE_CODE_INT
23722 The type is an integer type.
23724 @findex TYPE_CODE_FLT
23725 @findex gdb.TYPE_CODE_FLT
23726 @item gdb.TYPE_CODE_FLT
23727 A floating point type.
23729 @findex TYPE_CODE_VOID
23730 @findex gdb.TYPE_CODE_VOID
23731 @item gdb.TYPE_CODE_VOID
23732 The special type @code{void}.
23734 @findex TYPE_CODE_SET
23735 @findex gdb.TYPE_CODE_SET
23736 @item gdb.TYPE_CODE_SET
23739 @findex TYPE_CODE_RANGE
23740 @findex gdb.TYPE_CODE_RANGE
23741 @item gdb.TYPE_CODE_RANGE
23742 A range type, that is, an integer type with bounds.
23744 @findex TYPE_CODE_STRING
23745 @findex gdb.TYPE_CODE_STRING
23746 @item gdb.TYPE_CODE_STRING
23747 A string type. Note that this is only used for certain languages with
23748 language-defined string types; C strings are not represented this way.
23750 @findex TYPE_CODE_BITSTRING
23751 @findex gdb.TYPE_CODE_BITSTRING
23752 @item gdb.TYPE_CODE_BITSTRING
23753 A string of bits. It is deprecated.
23755 @findex TYPE_CODE_ERROR
23756 @findex gdb.TYPE_CODE_ERROR
23757 @item gdb.TYPE_CODE_ERROR
23758 An unknown or erroneous type.
23760 @findex TYPE_CODE_METHOD
23761 @findex gdb.TYPE_CODE_METHOD
23762 @item gdb.TYPE_CODE_METHOD
23763 A method type, as found in C@t{++} or Java.
23765 @findex TYPE_CODE_METHODPTR
23766 @findex gdb.TYPE_CODE_METHODPTR
23767 @item gdb.TYPE_CODE_METHODPTR
23768 A pointer-to-member-function.
23770 @findex TYPE_CODE_MEMBERPTR
23771 @findex gdb.TYPE_CODE_MEMBERPTR
23772 @item gdb.TYPE_CODE_MEMBERPTR
23773 A pointer-to-member.
23775 @findex TYPE_CODE_REF
23776 @findex gdb.TYPE_CODE_REF
23777 @item gdb.TYPE_CODE_REF
23780 @findex TYPE_CODE_CHAR
23781 @findex gdb.TYPE_CODE_CHAR
23782 @item gdb.TYPE_CODE_CHAR
23785 @findex TYPE_CODE_BOOL
23786 @findex gdb.TYPE_CODE_BOOL
23787 @item gdb.TYPE_CODE_BOOL
23790 @findex TYPE_CODE_COMPLEX
23791 @findex gdb.TYPE_CODE_COMPLEX
23792 @item gdb.TYPE_CODE_COMPLEX
23793 A complex float type.
23795 @findex TYPE_CODE_TYPEDEF
23796 @findex gdb.TYPE_CODE_TYPEDEF
23797 @item gdb.TYPE_CODE_TYPEDEF
23798 A typedef to some other type.
23800 @findex TYPE_CODE_NAMESPACE
23801 @findex gdb.TYPE_CODE_NAMESPACE
23802 @item gdb.TYPE_CODE_NAMESPACE
23803 A C@t{++} namespace.
23805 @findex TYPE_CODE_DECFLOAT
23806 @findex gdb.TYPE_CODE_DECFLOAT
23807 @item gdb.TYPE_CODE_DECFLOAT
23808 A decimal floating point type.
23810 @findex TYPE_CODE_INTERNAL_FUNCTION
23811 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23812 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23813 A function internal to @value{GDBN}. This is the type used to represent
23814 convenience functions.
23817 Further support for types is provided in the @code{gdb.types}
23818 Python module (@pxref{gdb.types}).
23820 @node Pretty Printing API
23821 @subsubsection Pretty Printing API
23823 An example output is provided (@pxref{Pretty Printing}).
23825 A pretty-printer is just an object that holds a value and implements a
23826 specific interface, defined here.
23828 @defun pretty_printer.children (self)
23829 @value{GDBN} will call this method on a pretty-printer to compute the
23830 children of the pretty-printer's value.
23832 This method must return an object conforming to the Python iterator
23833 protocol. Each item returned by the iterator must be a tuple holding
23834 two elements. The first element is the ``name'' of the child; the
23835 second element is the child's value. The value can be any Python
23836 object which is convertible to a @value{GDBN} value.
23838 This method is optional. If it does not exist, @value{GDBN} will act
23839 as though the value has no children.
23842 @defun pretty_printer.display_hint (self)
23843 The CLI may call this method and use its result to change the
23844 formatting of a value. The result will also be supplied to an MI
23845 consumer as a @samp{displayhint} attribute of the variable being
23848 This method is optional. If it does exist, this method must return a
23851 Some display hints are predefined by @value{GDBN}:
23855 Indicate that the object being printed is ``array-like''. The CLI
23856 uses this to respect parameters such as @code{set print elements} and
23857 @code{set print array}.
23860 Indicate that the object being printed is ``map-like'', and that the
23861 children of this value can be assumed to alternate between keys and
23865 Indicate that the object being printed is ``string-like''. If the
23866 printer's @code{to_string} method returns a Python string of some
23867 kind, then @value{GDBN} will call its internal language-specific
23868 string-printing function to format the string. For the CLI this means
23869 adding quotation marks, possibly escaping some characters, respecting
23870 @code{set print elements}, and the like.
23874 @defun pretty_printer.to_string (self)
23875 @value{GDBN} will call this method to display the string
23876 representation of the value passed to the object's constructor.
23878 When printing from the CLI, if the @code{to_string} method exists,
23879 then @value{GDBN} will prepend its result to the values returned by
23880 @code{children}. Exactly how this formatting is done is dependent on
23881 the display hint, and may change as more hints are added. Also,
23882 depending on the print settings (@pxref{Print Settings}), the CLI may
23883 print just the result of @code{to_string} in a stack trace, omitting
23884 the result of @code{children}.
23886 If this method returns a string, it is printed verbatim.
23888 Otherwise, if this method returns an instance of @code{gdb.Value},
23889 then @value{GDBN} prints this value. This may result in a call to
23890 another pretty-printer.
23892 If instead the method returns a Python value which is convertible to a
23893 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
23894 the resulting value. Again, this may result in a call to another
23895 pretty-printer. Python scalars (integers, floats, and booleans) and
23896 strings are convertible to @code{gdb.Value}; other types are not.
23898 Finally, if this method returns @code{None} then no further operations
23899 are peformed in this method and nothing is printed.
23901 If the result is not one of these types, an exception is raised.
23904 @value{GDBN} provides a function which can be used to look up the
23905 default pretty-printer for a @code{gdb.Value}:
23907 @findex gdb.default_visualizer
23908 @defun gdb.default_visualizer (value)
23909 This function takes a @code{gdb.Value} object as an argument. If a
23910 pretty-printer for this value exists, then it is returned. If no such
23911 printer exists, then this returns @code{None}.
23914 @node Selecting Pretty-Printers
23915 @subsubsection Selecting Pretty-Printers
23917 The Python list @code{gdb.pretty_printers} contains an array of
23918 functions or callable objects that have been registered via addition
23919 as a pretty-printer. Printers in this list are called @code{global}
23920 printers, they're available when debugging all inferiors.
23921 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
23922 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
23925 Each function on these lists is passed a single @code{gdb.Value}
23926 argument and should return a pretty-printer object conforming to the
23927 interface definition above (@pxref{Pretty Printing API}). If a function
23928 cannot create a pretty-printer for the value, it should return
23931 @value{GDBN} first checks the @code{pretty_printers} attribute of each
23932 @code{gdb.Objfile} in the current program space and iteratively calls
23933 each enabled lookup routine in the list for that @code{gdb.Objfile}
23934 until it receives a pretty-printer object.
23935 If no pretty-printer is found in the objfile lists, @value{GDBN} then
23936 searches the pretty-printer list of the current program space,
23937 calling each enabled function until an object is returned.
23938 After these lists have been exhausted, it tries the global
23939 @code{gdb.pretty_printers} list, again calling each enabled function until an
23940 object is returned.
23942 The order in which the objfiles are searched is not specified. For a
23943 given list, functions are always invoked from the head of the list,
23944 and iterated over sequentially until the end of the list, or a printer
23945 object is returned.
23947 For various reasons a pretty-printer may not work.
23948 For example, the underlying data structure may have changed and
23949 the pretty-printer is out of date.
23951 The consequences of a broken pretty-printer are severe enough that
23952 @value{GDBN} provides support for enabling and disabling individual
23953 printers. For example, if @code{print frame-arguments} is on,
23954 a backtrace can become highly illegible if any argument is printed
23955 with a broken printer.
23957 Pretty-printers are enabled and disabled by attaching an @code{enabled}
23958 attribute to the registered function or callable object. If this attribute
23959 is present and its value is @code{False}, the printer is disabled, otherwise
23960 the printer is enabled.
23962 @node Writing a Pretty-Printer
23963 @subsubsection Writing a Pretty-Printer
23964 @cindex writing a pretty-printer
23966 A pretty-printer consists of two parts: a lookup function to detect
23967 if the type is supported, and the printer itself.
23969 Here is an example showing how a @code{std::string} printer might be
23970 written. @xref{Pretty Printing API}, for details on the API this class
23974 class StdStringPrinter(object):
23975 "Print a std::string"
23977 def __init__(self, val):
23980 def to_string(self):
23981 return self.val['_M_dataplus']['_M_p']
23983 def display_hint(self):
23987 And here is an example showing how a lookup function for the printer
23988 example above might be written.
23991 def str_lookup_function(val):
23992 lookup_tag = val.type.tag
23993 if lookup_tag == None:
23995 regex = re.compile("^std::basic_string<char,.*>$")
23996 if regex.match(lookup_tag):
23997 return StdStringPrinter(val)
24001 The example lookup function extracts the value's type, and attempts to
24002 match it to a type that it can pretty-print. If it is a type the
24003 printer can pretty-print, it will return a printer object. If not, it
24004 returns @code{None}.
24006 We recommend that you put your core pretty-printers into a Python
24007 package. If your pretty-printers are for use with a library, we
24008 further recommend embedding a version number into the package name.
24009 This practice will enable @value{GDBN} to load multiple versions of
24010 your pretty-printers at the same time, because they will have
24013 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24014 can be evaluated multiple times without changing its meaning. An
24015 ideal auto-load file will consist solely of @code{import}s of your
24016 printer modules, followed by a call to a register pretty-printers with
24017 the current objfile.
24019 Taken as a whole, this approach will scale nicely to multiple
24020 inferiors, each potentially using a different library version.
24021 Embedding a version number in the Python package name will ensure that
24022 @value{GDBN} is able to load both sets of printers simultaneously.
24023 Then, because the search for pretty-printers is done by objfile, and
24024 because your auto-loaded code took care to register your library's
24025 printers with a specific objfile, @value{GDBN} will find the correct
24026 printers for the specific version of the library used by each
24029 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24030 this code might appear in @code{gdb.libstdcxx.v6}:
24033 def register_printers(objfile):
24034 objfile.pretty_printers.append(str_lookup_function)
24038 And then the corresponding contents of the auto-load file would be:
24041 import gdb.libstdcxx.v6
24042 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24045 The previous example illustrates a basic pretty-printer.
24046 There are a few things that can be improved on.
24047 The printer doesn't have a name, making it hard to identify in a
24048 list of installed printers. The lookup function has a name, but
24049 lookup functions can have arbitrary, even identical, names.
24051 Second, the printer only handles one type, whereas a library typically has
24052 several types. One could install a lookup function for each desired type
24053 in the library, but one could also have a single lookup function recognize
24054 several types. The latter is the conventional way this is handled.
24055 If a pretty-printer can handle multiple data types, then its
24056 @dfn{subprinters} are the printers for the individual data types.
24058 The @code{gdb.printing} module provides a formal way of solving these
24059 problems (@pxref{gdb.printing}).
24060 Here is another example that handles multiple types.
24062 These are the types we are going to pretty-print:
24065 struct foo @{ int a, b; @};
24066 struct bar @{ struct foo x, y; @};
24069 Here are the printers:
24073 """Print a foo object."""
24075 def __init__(self, val):
24078 def to_string(self):
24079 return ("a=<" + str(self.val["a"]) +
24080 "> b=<" + str(self.val["b"]) + ">")
24083 """Print a bar object."""
24085 def __init__(self, val):
24088 def to_string(self):
24089 return ("x=<" + str(self.val["x"]) +
24090 "> y=<" + str(self.val["y"]) + ">")
24093 This example doesn't need a lookup function, that is handled by the
24094 @code{gdb.printing} module. Instead a function is provided to build up
24095 the object that handles the lookup.
24098 import gdb.printing
24100 def build_pretty_printer():
24101 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24103 pp.add_printer('foo', '^foo$', fooPrinter)
24104 pp.add_printer('bar', '^bar$', barPrinter)
24108 And here is the autoload support:
24111 import gdb.printing
24113 gdb.printing.register_pretty_printer(
24114 gdb.current_objfile(),
24115 my_library.build_pretty_printer())
24118 Finally, when this printer is loaded into @value{GDBN}, here is the
24119 corresponding output of @samp{info pretty-printer}:
24122 (gdb) info pretty-printer
24129 @node Type Printing API
24130 @subsubsection Type Printing API
24131 @cindex type printing API for Python
24133 @value{GDBN} provides a way for Python code to customize type display.
24134 This is mainly useful for substituting canonical typedef names for
24137 @cindex type printer
24138 A @dfn{type printer} is just a Python object conforming to a certain
24139 protocol. A simple base class implementing the protocol is provided;
24140 see @ref{gdb.types}. A type printer must supply at least:
24142 @defivar type_printer enabled
24143 A boolean which is True if the printer is enabled, and False
24144 otherwise. This is manipulated by the @code{enable type-printer}
24145 and @code{disable type-printer} commands.
24148 @defivar type_printer name
24149 The name of the type printer. This must be a string. This is used by
24150 the @code{enable type-printer} and @code{disable type-printer}
24154 @defmethod type_printer instantiate (self)
24155 This is called by @value{GDBN} at the start of type-printing. It is
24156 only called if the type printer is enabled. This method must return a
24157 new object that supplies a @code{recognize} method, as described below.
24161 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24162 will compute a list of type recognizers. This is done by iterating
24163 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24164 followed by the per-progspace type printers (@pxref{Progspaces In
24165 Python}), and finally the global type printers.
24167 @value{GDBN} will call the @code{instantiate} method of each enabled
24168 type printer. If this method returns @code{None}, then the result is
24169 ignored; otherwise, it is appended to the list of recognizers.
24171 Then, when @value{GDBN} is going to display a type name, it iterates
24172 over the list of recognizers. For each one, it calls the recognition
24173 function, stopping if the function returns a non-@code{None} value.
24174 The recognition function is defined as:
24176 @defmethod type_recognizer recognize (self, type)
24177 If @var{type} is not recognized, return @code{None}. Otherwise,
24178 return a string which is to be printed as the name of @var{type}.
24179 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24183 @value{GDBN} uses this two-pass approach so that type printers can
24184 efficiently cache information without holding on to it too long. For
24185 example, it can be convenient to look up type information in a type
24186 printer and hold it for a recognizer's lifetime; if a single pass were
24187 done then type printers would have to make use of the event system in
24188 order to avoid holding information that could become stale as the
24191 @node Inferiors In Python
24192 @subsubsection Inferiors In Python
24193 @cindex inferiors in Python
24195 @findex gdb.Inferior
24196 Programs which are being run under @value{GDBN} are called inferiors
24197 (@pxref{Inferiors and Programs}). Python scripts can access
24198 information about and manipulate inferiors controlled by @value{GDBN}
24199 via objects of the @code{gdb.Inferior} class.
24201 The following inferior-related functions are available in the @code{gdb}
24204 @defun gdb.inferiors ()
24205 Return a tuple containing all inferior objects.
24208 @defun gdb.selected_inferior ()
24209 Return an object representing the current inferior.
24212 A @code{gdb.Inferior} object has the following attributes:
24214 @defvar Inferior.num
24215 ID of inferior, as assigned by GDB.
24218 @defvar Inferior.pid
24219 Process ID of the inferior, as assigned by the underlying operating
24223 @defvar Inferior.was_attached
24224 Boolean signaling whether the inferior was created using `attach', or
24225 started by @value{GDBN} itself.
24228 A @code{gdb.Inferior} object has the following methods:
24230 @defun Inferior.is_valid ()
24231 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24232 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24233 if the inferior no longer exists within @value{GDBN}. All other
24234 @code{gdb.Inferior} methods will throw an exception if it is invalid
24235 at the time the method is called.
24238 @defun Inferior.threads ()
24239 This method returns a tuple holding all the threads which are valid
24240 when it is called. If there are no valid threads, the method will
24241 return an empty tuple.
24244 @findex Inferior.read_memory
24245 @defun Inferior.read_memory (address, length)
24246 Read @var{length} bytes of memory from the inferior, starting at
24247 @var{address}. Returns a buffer object, which behaves much like an array
24248 or a string. It can be modified and given to the
24249 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24250 value is a @code{memoryview} object.
24253 @findex Inferior.write_memory
24254 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24255 Write the contents of @var{buffer} to the inferior, starting at
24256 @var{address}. The @var{buffer} parameter must be a Python object
24257 which supports the buffer protocol, i.e., a string, an array or the
24258 object returned from @code{Inferior.read_memory}. If given, @var{length}
24259 determines the number of bytes from @var{buffer} to be written.
24262 @findex gdb.search_memory
24263 @defun Inferior.search_memory (address, length, pattern)
24264 Search a region of the inferior memory starting at @var{address} with
24265 the given @var{length} using the search pattern supplied in
24266 @var{pattern}. The @var{pattern} parameter must be a Python object
24267 which supports the buffer protocol, i.e., a string, an array or the
24268 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24269 containing the address where the pattern was found, or @code{None} if
24270 the pattern could not be found.
24273 @node Events In Python
24274 @subsubsection Events In Python
24275 @cindex inferior events in Python
24277 @value{GDBN} provides a general event facility so that Python code can be
24278 notified of various state changes, particularly changes that occur in
24281 An @dfn{event} is just an object that describes some state change. The
24282 type of the object and its attributes will vary depending on the details
24283 of the change. All the existing events are described below.
24285 In order to be notified of an event, you must register an event handler
24286 with an @dfn{event registry}. An event registry is an object in the
24287 @code{gdb.events} module which dispatches particular events. A registry
24288 provides methods to register and unregister event handlers:
24290 @defun EventRegistry.connect (object)
24291 Add the given callable @var{object} to the registry. This object will be
24292 called when an event corresponding to this registry occurs.
24295 @defun EventRegistry.disconnect (object)
24296 Remove the given @var{object} from the registry. Once removed, the object
24297 will no longer receive notifications of events.
24300 Here is an example:
24303 def exit_handler (event):
24304 print "event type: exit"
24305 print "exit code: %d" % (event.exit_code)
24307 gdb.events.exited.connect (exit_handler)
24310 In the above example we connect our handler @code{exit_handler} to the
24311 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24312 called when the inferior exits. The argument @dfn{event} in this example is
24313 of type @code{gdb.ExitedEvent}. As you can see in the example the
24314 @code{ExitedEvent} object has an attribute which indicates the exit code of
24317 The following is a listing of the event registries that are available and
24318 details of the events they emit:
24323 Emits @code{gdb.ThreadEvent}.
24325 Some events can be thread specific when @value{GDBN} is running in non-stop
24326 mode. When represented in Python, these events all extend
24327 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24328 events which are emitted by this or other modules might extend this event.
24329 Examples of these events are @code{gdb.BreakpointEvent} and
24330 @code{gdb.ContinueEvent}.
24332 @defvar ThreadEvent.inferior_thread
24333 In non-stop mode this attribute will be set to the specific thread which was
24334 involved in the emitted event. Otherwise, it will be set to @code{None}.
24337 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24339 This event indicates that the inferior has been continued after a stop. For
24340 inherited attribute refer to @code{gdb.ThreadEvent} above.
24342 @item events.exited
24343 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24344 @code{events.ExitedEvent} has two attributes:
24345 @defvar ExitedEvent.exit_code
24346 An integer representing the exit code, if available, which the inferior
24347 has returned. (The exit code could be unavailable if, for example,
24348 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24349 the attribute does not exist.
24351 @defvar ExitedEvent inferior
24352 A reference to the inferior which triggered the @code{exited} event.
24356 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24358 Indicates that the inferior has stopped. All events emitted by this registry
24359 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24360 will indicate the stopped thread when @value{GDBN} is running in non-stop
24361 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24363 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24365 This event indicates that the inferior or one of its threads has received as
24366 signal. @code{gdb.SignalEvent} has the following attributes:
24368 @defvar SignalEvent.stop_signal
24369 A string representing the signal received by the inferior. A list of possible
24370 signal values can be obtained by running the command @code{info signals} in
24371 the @value{GDBN} command prompt.
24374 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24376 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24377 been hit, and has the following attributes:
24379 @defvar BreakpointEvent.breakpoints
24380 A sequence containing references to all the breakpoints (type
24381 @code{gdb.Breakpoint}) that were hit.
24382 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24384 @defvar BreakpointEvent.breakpoint
24385 A reference to the first breakpoint that was hit.
24386 This function is maintained for backward compatibility and is now deprecated
24387 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24390 @item events.new_objfile
24391 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24392 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24394 @defvar NewObjFileEvent.new_objfile
24395 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24396 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24401 @node Threads In Python
24402 @subsubsection Threads In Python
24403 @cindex threads in python
24405 @findex gdb.InferiorThread
24406 Python scripts can access information about, and manipulate inferior threads
24407 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24409 The following thread-related functions are available in the @code{gdb}
24412 @findex gdb.selected_thread
24413 @defun gdb.selected_thread ()
24414 This function returns the thread object for the selected thread. If there
24415 is no selected thread, this will return @code{None}.
24418 A @code{gdb.InferiorThread} object has the following attributes:
24420 @defvar InferiorThread.name
24421 The name of the thread. If the user specified a name using
24422 @code{thread name}, then this returns that name. Otherwise, if an
24423 OS-supplied name is available, then it is returned. Otherwise, this
24424 returns @code{None}.
24426 This attribute can be assigned to. The new value must be a string
24427 object, which sets the new name, or @code{None}, which removes any
24428 user-specified thread name.
24431 @defvar InferiorThread.num
24432 ID of the thread, as assigned by GDB.
24435 @defvar InferiorThread.ptid
24436 ID of the thread, as assigned by the operating system. This attribute is a
24437 tuple containing three integers. The first is the Process ID (PID); the second
24438 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24439 Either the LWPID or TID may be 0, which indicates that the operating system
24440 does not use that identifier.
24443 A @code{gdb.InferiorThread} object has the following methods:
24445 @defun InferiorThread.is_valid ()
24446 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24447 @code{False} if not. A @code{gdb.InferiorThread} object will become
24448 invalid if the thread exits, or the inferior that the thread belongs
24449 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24450 exception if it is invalid at the time the method is called.
24453 @defun InferiorThread.switch ()
24454 This changes @value{GDBN}'s currently selected thread to the one represented
24458 @defun InferiorThread.is_stopped ()
24459 Return a Boolean indicating whether the thread is stopped.
24462 @defun InferiorThread.is_running ()
24463 Return a Boolean indicating whether the thread is running.
24466 @defun InferiorThread.is_exited ()
24467 Return a Boolean indicating whether the thread is exited.
24470 @node Commands In Python
24471 @subsubsection Commands In Python
24473 @cindex commands in python
24474 @cindex python commands
24475 You can implement new @value{GDBN} CLI commands in Python. A CLI
24476 command is implemented using an instance of the @code{gdb.Command}
24477 class, most commonly using a subclass.
24479 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24480 The object initializer for @code{Command} registers the new command
24481 with @value{GDBN}. This initializer is normally invoked from the
24482 subclass' own @code{__init__} method.
24484 @var{name} is the name of the command. If @var{name} consists of
24485 multiple words, then the initial words are looked for as prefix
24486 commands. In this case, if one of the prefix commands does not exist,
24487 an exception is raised.
24489 There is no support for multi-line commands.
24491 @var{command_class} should be one of the @samp{COMMAND_} constants
24492 defined below. This argument tells @value{GDBN} how to categorize the
24493 new command in the help system.
24495 @var{completer_class} is an optional argument. If given, it should be
24496 one of the @samp{COMPLETE_} constants defined below. This argument
24497 tells @value{GDBN} how to perform completion for this command. If not
24498 given, @value{GDBN} will attempt to complete using the object's
24499 @code{complete} method (see below); if no such method is found, an
24500 error will occur when completion is attempted.
24502 @var{prefix} is an optional argument. If @code{True}, then the new
24503 command is a prefix command; sub-commands of this command may be
24506 The help text for the new command is taken from the Python
24507 documentation string for the command's class, if there is one. If no
24508 documentation string is provided, the default value ``This command is
24509 not documented.'' is used.
24512 @cindex don't repeat Python command
24513 @defun Command.dont_repeat ()
24514 By default, a @value{GDBN} command is repeated when the user enters a
24515 blank line at the command prompt. A command can suppress this
24516 behavior by invoking the @code{dont_repeat} method. This is similar
24517 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24520 @defun Command.invoke (argument, from_tty)
24521 This method is called by @value{GDBN} when this command is invoked.
24523 @var{argument} is a string. It is the argument to the command, after
24524 leading and trailing whitespace has been stripped.
24526 @var{from_tty} is a boolean argument. When true, this means that the
24527 command was entered by the user at the terminal; when false it means
24528 that the command came from elsewhere.
24530 If this method throws an exception, it is turned into a @value{GDBN}
24531 @code{error} call. Otherwise, the return value is ignored.
24533 @findex gdb.string_to_argv
24534 To break @var{argument} up into an argv-like string use
24535 @code{gdb.string_to_argv}. This function behaves identically to
24536 @value{GDBN}'s internal argument lexer @code{buildargv}.
24537 It is recommended to use this for consistency.
24538 Arguments are separated by spaces and may be quoted.
24542 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24543 ['1', '2 "3', '4 "5', "6 '7"]
24548 @cindex completion of Python commands
24549 @defun Command.complete (text, word)
24550 This method is called by @value{GDBN} when the user attempts
24551 completion on this command. All forms of completion are handled by
24552 this method, that is, the @key{TAB} and @key{M-?} key bindings
24553 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24556 The arguments @var{text} and @var{word} are both strings. @var{text}
24557 holds the complete command line up to the cursor's location.
24558 @var{word} holds the last word of the command line; this is computed
24559 using a word-breaking heuristic.
24561 The @code{complete} method can return several values:
24564 If the return value is a sequence, the contents of the sequence are
24565 used as the completions. It is up to @code{complete} to ensure that the
24566 contents actually do complete the word. A zero-length sequence is
24567 allowed, it means that there were no completions available. Only
24568 string elements of the sequence are used; other elements in the
24569 sequence are ignored.
24572 If the return value is one of the @samp{COMPLETE_} constants defined
24573 below, then the corresponding @value{GDBN}-internal completion
24574 function is invoked, and its result is used.
24577 All other results are treated as though there were no available
24582 When a new command is registered, it must be declared as a member of
24583 some general class of commands. This is used to classify top-level
24584 commands in the on-line help system; note that prefix commands are not
24585 listed under their own category but rather that of their top-level
24586 command. The available classifications are represented by constants
24587 defined in the @code{gdb} module:
24590 @findex COMMAND_NONE
24591 @findex gdb.COMMAND_NONE
24592 @item gdb.COMMAND_NONE
24593 The command does not belong to any particular class. A command in
24594 this category will not be displayed in any of the help categories.
24596 @findex COMMAND_RUNNING
24597 @findex gdb.COMMAND_RUNNING
24598 @item gdb.COMMAND_RUNNING
24599 The command is related to running the inferior. For example,
24600 @code{start}, @code{step}, and @code{continue} are in this category.
24601 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24602 commands in this category.
24604 @findex COMMAND_DATA
24605 @findex gdb.COMMAND_DATA
24606 @item gdb.COMMAND_DATA
24607 The command is related to data or variables. For example,
24608 @code{call}, @code{find}, and @code{print} are in this category. Type
24609 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24612 @findex COMMAND_STACK
24613 @findex gdb.COMMAND_STACK
24614 @item gdb.COMMAND_STACK
24615 The command has to do with manipulation of the stack. For example,
24616 @code{backtrace}, @code{frame}, and @code{return} are in this
24617 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24618 list of commands in this category.
24620 @findex COMMAND_FILES
24621 @findex gdb.COMMAND_FILES
24622 @item gdb.COMMAND_FILES
24623 This class is used for file-related commands. For example,
24624 @code{file}, @code{list} and @code{section} are in this category.
24625 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24626 commands in this category.
24628 @findex COMMAND_SUPPORT
24629 @findex gdb.COMMAND_SUPPORT
24630 @item gdb.COMMAND_SUPPORT
24631 This should be used for ``support facilities'', generally meaning
24632 things that are useful to the user when interacting with @value{GDBN},
24633 but not related to the state of the inferior. For example,
24634 @code{help}, @code{make}, and @code{shell} are in this category. Type
24635 @kbd{help support} at the @value{GDBN} prompt to see a list of
24636 commands in this category.
24638 @findex COMMAND_STATUS
24639 @findex gdb.COMMAND_STATUS
24640 @item gdb.COMMAND_STATUS
24641 The command is an @samp{info}-related command, that is, related to the
24642 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24643 and @code{show} are in this category. Type @kbd{help status} at the
24644 @value{GDBN} prompt to see a list of commands in this category.
24646 @findex COMMAND_BREAKPOINTS
24647 @findex gdb.COMMAND_BREAKPOINTS
24648 @item gdb.COMMAND_BREAKPOINTS
24649 The command has to do with breakpoints. For example, @code{break},
24650 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24651 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24654 @findex COMMAND_TRACEPOINTS
24655 @findex gdb.COMMAND_TRACEPOINTS
24656 @item gdb.COMMAND_TRACEPOINTS
24657 The command has to do with tracepoints. For example, @code{trace},
24658 @code{actions}, and @code{tfind} are in this category. Type
24659 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24660 commands in this category.
24662 @findex COMMAND_USER
24663 @findex gdb.COMMAND_USER
24664 @item gdb.COMMAND_USER
24665 The command is a general purpose command for the user, and typically
24666 does not fit in one of the other categories.
24667 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24668 a list of commands in this category, as well as the list of gdb macros
24669 (@pxref{Sequences}).
24671 @findex COMMAND_OBSCURE
24672 @findex gdb.COMMAND_OBSCURE
24673 @item gdb.COMMAND_OBSCURE
24674 The command is only used in unusual circumstances, or is not of
24675 general interest to users. For example, @code{checkpoint},
24676 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24677 obscure} at the @value{GDBN} prompt to see a list of commands in this
24680 @findex COMMAND_MAINTENANCE
24681 @findex gdb.COMMAND_MAINTENANCE
24682 @item gdb.COMMAND_MAINTENANCE
24683 The command is only useful to @value{GDBN} maintainers. The
24684 @code{maintenance} and @code{flushregs} commands are in this category.
24685 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24686 commands in this category.
24689 A new command can use a predefined completion function, either by
24690 specifying it via an argument at initialization, or by returning it
24691 from the @code{complete} method. These predefined completion
24692 constants are all defined in the @code{gdb} module:
24695 @findex COMPLETE_NONE
24696 @findex gdb.COMPLETE_NONE
24697 @item gdb.COMPLETE_NONE
24698 This constant means that no completion should be done.
24700 @findex COMPLETE_FILENAME
24701 @findex gdb.COMPLETE_FILENAME
24702 @item gdb.COMPLETE_FILENAME
24703 This constant means that filename completion should be performed.
24705 @findex COMPLETE_LOCATION
24706 @findex gdb.COMPLETE_LOCATION
24707 @item gdb.COMPLETE_LOCATION
24708 This constant means that location completion should be done.
24709 @xref{Specify Location}.
24711 @findex COMPLETE_COMMAND
24712 @findex gdb.COMPLETE_COMMAND
24713 @item gdb.COMPLETE_COMMAND
24714 This constant means that completion should examine @value{GDBN}
24717 @findex COMPLETE_SYMBOL
24718 @findex gdb.COMPLETE_SYMBOL
24719 @item gdb.COMPLETE_SYMBOL
24720 This constant means that completion should be done using symbol names
24724 The following code snippet shows how a trivial CLI command can be
24725 implemented in Python:
24728 class HelloWorld (gdb.Command):
24729 """Greet the whole world."""
24731 def __init__ (self):
24732 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24734 def invoke (self, arg, from_tty):
24735 print "Hello, World!"
24740 The last line instantiates the class, and is necessary to trigger the
24741 registration of the command with @value{GDBN}. Depending on how the
24742 Python code is read into @value{GDBN}, you may need to import the
24743 @code{gdb} module explicitly.
24745 @node Parameters In Python
24746 @subsubsection Parameters In Python
24748 @cindex parameters in python
24749 @cindex python parameters
24750 @tindex gdb.Parameter
24752 You can implement new @value{GDBN} parameters using Python. A new
24753 parameter is implemented as an instance of the @code{gdb.Parameter}
24756 Parameters are exposed to the user via the @code{set} and
24757 @code{show} commands. @xref{Help}.
24759 There are many parameters that already exist and can be set in
24760 @value{GDBN}. Two examples are: @code{set follow fork} and
24761 @code{set charset}. Setting these parameters influences certain
24762 behavior in @value{GDBN}. Similarly, you can define parameters that
24763 can be used to influence behavior in custom Python scripts and commands.
24765 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24766 The object initializer for @code{Parameter} registers the new
24767 parameter with @value{GDBN}. This initializer is normally invoked
24768 from the subclass' own @code{__init__} method.
24770 @var{name} is the name of the new parameter. If @var{name} consists
24771 of multiple words, then the initial words are looked for as prefix
24772 parameters. An example of this can be illustrated with the
24773 @code{set print} set of parameters. If @var{name} is
24774 @code{print foo}, then @code{print} will be searched as the prefix
24775 parameter. In this case the parameter can subsequently be accessed in
24776 @value{GDBN} as @code{set print foo}.
24778 If @var{name} consists of multiple words, and no prefix parameter group
24779 can be found, an exception is raised.
24781 @var{command-class} should be one of the @samp{COMMAND_} constants
24782 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24783 categorize the new parameter in the help system.
24785 @var{parameter-class} should be one of the @samp{PARAM_} constants
24786 defined below. This argument tells @value{GDBN} the type of the new
24787 parameter; this information is used for input validation and
24790 If @var{parameter-class} is @code{PARAM_ENUM}, then
24791 @var{enum-sequence} must be a sequence of strings. These strings
24792 represent the possible values for the parameter.
24794 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24795 of a fourth argument will cause an exception to be thrown.
24797 The help text for the new parameter is taken from the Python
24798 documentation string for the parameter's class, if there is one. If
24799 there is no documentation string, a default value is used.
24802 @defvar Parameter.set_doc
24803 If this attribute exists, and is a string, then its value is used as
24804 the help text for this parameter's @code{set} command. The value is
24805 examined when @code{Parameter.__init__} is invoked; subsequent changes
24809 @defvar Parameter.show_doc
24810 If this attribute exists, and is a string, then its value is used as
24811 the help text for this parameter's @code{show} command. The value is
24812 examined when @code{Parameter.__init__} is invoked; subsequent changes
24816 @defvar Parameter.value
24817 The @code{value} attribute holds the underlying value of the
24818 parameter. It can be read and assigned to just as any other
24819 attribute. @value{GDBN} does validation when assignments are made.
24822 There are two methods that should be implemented in any
24823 @code{Parameter} class. These are:
24825 @defun Parameter.get_set_string (self)
24826 @value{GDBN} will call this method when a @var{parameter}'s value has
24827 been changed via the @code{set} API (for example, @kbd{set foo off}).
24828 The @code{value} attribute has already been populated with the new
24829 value and may be used in output. This method must return a string.
24832 @defun Parameter.get_show_string (self, svalue)
24833 @value{GDBN} will call this method when a @var{parameter}'s
24834 @code{show} API has been invoked (for example, @kbd{show foo}). The
24835 argument @code{svalue} receives the string representation of the
24836 current value. This method must return a string.
24839 When a new parameter is defined, its type must be specified. The
24840 available types are represented by constants defined in the @code{gdb}
24844 @findex PARAM_BOOLEAN
24845 @findex gdb.PARAM_BOOLEAN
24846 @item gdb.PARAM_BOOLEAN
24847 The value is a plain boolean. The Python boolean values, @code{True}
24848 and @code{False} are the only valid values.
24850 @findex PARAM_AUTO_BOOLEAN
24851 @findex gdb.PARAM_AUTO_BOOLEAN
24852 @item gdb.PARAM_AUTO_BOOLEAN
24853 The value has three possible states: true, false, and @samp{auto}. In
24854 Python, true and false are represented using boolean constants, and
24855 @samp{auto} is represented using @code{None}.
24857 @findex PARAM_UINTEGER
24858 @findex gdb.PARAM_UINTEGER
24859 @item gdb.PARAM_UINTEGER
24860 The value is an unsigned integer. The value of 0 should be
24861 interpreted to mean ``unlimited''.
24863 @findex PARAM_INTEGER
24864 @findex gdb.PARAM_INTEGER
24865 @item gdb.PARAM_INTEGER
24866 The value is a signed integer. The value of 0 should be interpreted
24867 to mean ``unlimited''.
24869 @findex PARAM_STRING
24870 @findex gdb.PARAM_STRING
24871 @item gdb.PARAM_STRING
24872 The value is a string. When the user modifies the string, any escape
24873 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
24874 translated into corresponding characters and encoded into the current
24877 @findex PARAM_STRING_NOESCAPE
24878 @findex gdb.PARAM_STRING_NOESCAPE
24879 @item gdb.PARAM_STRING_NOESCAPE
24880 The value is a string. When the user modifies the string, escapes are
24881 passed through untranslated.
24883 @findex PARAM_OPTIONAL_FILENAME
24884 @findex gdb.PARAM_OPTIONAL_FILENAME
24885 @item gdb.PARAM_OPTIONAL_FILENAME
24886 The value is a either a filename (a string), or @code{None}.
24888 @findex PARAM_FILENAME
24889 @findex gdb.PARAM_FILENAME
24890 @item gdb.PARAM_FILENAME
24891 The value is a filename. This is just like
24892 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
24894 @findex PARAM_ZINTEGER
24895 @findex gdb.PARAM_ZINTEGER
24896 @item gdb.PARAM_ZINTEGER
24897 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
24898 is interpreted as itself.
24901 @findex gdb.PARAM_ENUM
24902 @item gdb.PARAM_ENUM
24903 The value is a string, which must be one of a collection string
24904 constants provided when the parameter is created.
24907 @node Functions In Python
24908 @subsubsection Writing new convenience functions
24910 @cindex writing convenience functions
24911 @cindex convenience functions in python
24912 @cindex python convenience functions
24913 @tindex gdb.Function
24915 You can implement new convenience functions (@pxref{Convenience Vars})
24916 in Python. A convenience function is an instance of a subclass of the
24917 class @code{gdb.Function}.
24919 @defun Function.__init__ (name)
24920 The initializer for @code{Function} registers the new function with
24921 @value{GDBN}. The argument @var{name} is the name of the function,
24922 a string. The function will be visible to the user as a convenience
24923 variable of type @code{internal function}, whose name is the same as
24924 the given @var{name}.
24926 The documentation for the new function is taken from the documentation
24927 string for the new class.
24930 @defun Function.invoke (@var{*args})
24931 When a convenience function is evaluated, its arguments are converted
24932 to instances of @code{gdb.Value}, and then the function's
24933 @code{invoke} method is called. Note that @value{GDBN} does not
24934 predetermine the arity of convenience functions. Instead, all
24935 available arguments are passed to @code{invoke}, following the
24936 standard Python calling convention. In particular, a convenience
24937 function can have default values for parameters without ill effect.
24939 The return value of this method is used as its value in the enclosing
24940 expression. If an ordinary Python value is returned, it is converted
24941 to a @code{gdb.Value} following the usual rules.
24944 The following code snippet shows how a trivial convenience function can
24945 be implemented in Python:
24948 class Greet (gdb.Function):
24949 """Return string to greet someone.
24950 Takes a name as argument."""
24952 def __init__ (self):
24953 super (Greet, self).__init__ ("greet")
24955 def invoke (self, name):
24956 return "Hello, %s!" % name.string ()
24961 The last line instantiates the class, and is necessary to trigger the
24962 registration of the function with @value{GDBN}. Depending on how the
24963 Python code is read into @value{GDBN}, you may need to import the
24964 @code{gdb} module explicitly.
24966 Now you can use the function in an expression:
24969 (gdb) print $greet("Bob")
24973 @node Progspaces In Python
24974 @subsubsection Program Spaces In Python
24976 @cindex progspaces in python
24977 @tindex gdb.Progspace
24979 A program space, or @dfn{progspace}, represents a symbolic view
24980 of an address space.
24981 It consists of all of the objfiles of the program.
24982 @xref{Objfiles In Python}.
24983 @xref{Inferiors and Programs, program spaces}, for more details
24984 about program spaces.
24986 The following progspace-related functions are available in the
24989 @findex gdb.current_progspace
24990 @defun gdb.current_progspace ()
24991 This function returns the program space of the currently selected inferior.
24992 @xref{Inferiors and Programs}.
24995 @findex gdb.progspaces
24996 @defun gdb.progspaces ()
24997 Return a sequence of all the progspaces currently known to @value{GDBN}.
25000 Each progspace is represented by an instance of the @code{gdb.Progspace}
25003 @defvar Progspace.filename
25004 The file name of the progspace as a string.
25007 @defvar Progspace.pretty_printers
25008 The @code{pretty_printers} attribute is a list of functions. It is
25009 used to look up pretty-printers. A @code{Value} is passed to each
25010 function in order; if the function returns @code{None}, then the
25011 search continues. Otherwise, the return value should be an object
25012 which is used to format the value. @xref{Pretty Printing API}, for more
25016 @defvar Progspace.type_printers
25017 The @code{type_printers} attribute is a list of type printer objects.
25018 @xref{Type Printing API}, for more information.
25021 @node Objfiles In Python
25022 @subsubsection Objfiles In Python
25024 @cindex objfiles in python
25025 @tindex gdb.Objfile
25027 @value{GDBN} loads symbols for an inferior from various
25028 symbol-containing files (@pxref{Files}). These include the primary
25029 executable file, any shared libraries used by the inferior, and any
25030 separate debug info files (@pxref{Separate Debug Files}).
25031 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25033 The following objfile-related functions are available in the
25036 @findex gdb.current_objfile
25037 @defun gdb.current_objfile ()
25038 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25039 sets the ``current objfile'' to the corresponding objfile. This
25040 function returns the current objfile. If there is no current objfile,
25041 this function returns @code{None}.
25044 @findex gdb.objfiles
25045 @defun gdb.objfiles ()
25046 Return a sequence of all the objfiles current known to @value{GDBN}.
25047 @xref{Objfiles In Python}.
25050 Each objfile is represented by an instance of the @code{gdb.Objfile}
25053 @defvar Objfile.filename
25054 The file name of the objfile as a string.
25057 @defvar Objfile.pretty_printers
25058 The @code{pretty_printers} attribute is a list of functions. It is
25059 used to look up pretty-printers. A @code{Value} is passed to each
25060 function in order; if the function returns @code{None}, then the
25061 search continues. Otherwise, the return value should be an object
25062 which is used to format the value. @xref{Pretty Printing API}, for more
25066 @defvar Objfile.type_printers
25067 The @code{type_printers} attribute is a list of type printer objects.
25068 @xref{Type Printing API}, for more information.
25071 A @code{gdb.Objfile} object has the following methods:
25073 @defun Objfile.is_valid ()
25074 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25075 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25076 if the object file it refers to is not loaded in @value{GDBN} any
25077 longer. All other @code{gdb.Objfile} methods will throw an exception
25078 if it is invalid at the time the method is called.
25081 @node Frames In Python
25082 @subsubsection Accessing inferior stack frames from Python.
25084 @cindex frames in python
25085 When the debugged program stops, @value{GDBN} is able to analyze its call
25086 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25087 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25088 while its corresponding frame exists in the inferior's stack. If you try
25089 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25090 exception (@pxref{Exception Handling}).
25092 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25096 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25100 The following frame-related functions are available in the @code{gdb} module:
25102 @findex gdb.selected_frame
25103 @defun gdb.selected_frame ()
25104 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25107 @findex gdb.newest_frame
25108 @defun gdb.newest_frame ()
25109 Return the newest frame object for the selected thread.
25112 @defun gdb.frame_stop_reason_string (reason)
25113 Return a string explaining the reason why @value{GDBN} stopped unwinding
25114 frames, as expressed by the given @var{reason} code (an integer, see the
25115 @code{unwind_stop_reason} method further down in this section).
25118 A @code{gdb.Frame} object has the following methods:
25120 @defun Frame.is_valid ()
25121 Returns true if the @code{gdb.Frame} object is valid, false if not.
25122 A frame object can become invalid if the frame it refers to doesn't
25123 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25124 an exception if it is invalid at the time the method is called.
25127 @defun Frame.name ()
25128 Returns the function name of the frame, or @code{None} if it can't be
25132 @defun Frame.architecture ()
25133 Returns the @code{gdb.Architecture} object corresponding to the frame's
25134 architecture. @xref{Architectures In Python}.
25137 @defun Frame.type ()
25138 Returns the type of the frame. The value can be one of:
25140 @item gdb.NORMAL_FRAME
25141 An ordinary stack frame.
25143 @item gdb.DUMMY_FRAME
25144 A fake stack frame that was created by @value{GDBN} when performing an
25145 inferior function call.
25147 @item gdb.INLINE_FRAME
25148 A frame representing an inlined function. The function was inlined
25149 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25151 @item gdb.TAILCALL_FRAME
25152 A frame representing a tail call. @xref{Tail Call Frames}.
25154 @item gdb.SIGTRAMP_FRAME
25155 A signal trampoline frame. This is the frame created by the OS when
25156 it calls into a signal handler.
25158 @item gdb.ARCH_FRAME
25159 A fake stack frame representing a cross-architecture call.
25161 @item gdb.SENTINEL_FRAME
25162 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25167 @defun Frame.unwind_stop_reason ()
25168 Return an integer representing the reason why it's not possible to find
25169 more frames toward the outermost frame. Use
25170 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25171 function to a string. The value can be one of:
25174 @item gdb.FRAME_UNWIND_NO_REASON
25175 No particular reason (older frames should be available).
25177 @item gdb.FRAME_UNWIND_NULL_ID
25178 The previous frame's analyzer returns an invalid result.
25180 @item gdb.FRAME_UNWIND_OUTERMOST
25181 This frame is the outermost.
25183 @item gdb.FRAME_UNWIND_UNAVAILABLE
25184 Cannot unwind further, because that would require knowing the
25185 values of registers or memory that have not been collected.
25187 @item gdb.FRAME_UNWIND_INNER_ID
25188 This frame ID looks like it ought to belong to a NEXT frame,
25189 but we got it for a PREV frame. Normally, this is a sign of
25190 unwinder failure. It could also indicate stack corruption.
25192 @item gdb.FRAME_UNWIND_SAME_ID
25193 This frame has the same ID as the previous one. That means
25194 that unwinding further would almost certainly give us another
25195 frame with exactly the same ID, so break the chain. Normally,
25196 this is a sign of unwinder failure. It could also indicate
25199 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25200 The frame unwinder did not find any saved PC, but we needed
25201 one to unwind further.
25203 @item gdb.FRAME_UNWIND_FIRST_ERROR
25204 Any stop reason greater or equal to this value indicates some kind
25205 of error. This special value facilitates writing code that tests
25206 for errors in unwinding in a way that will work correctly even if
25207 the list of the other values is modified in future @value{GDBN}
25208 versions. Using it, you could write:
25210 reason = gdb.selected_frame().unwind_stop_reason ()
25211 reason_str = gdb.frame_stop_reason_string (reason)
25212 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25213 print "An error occured: %s" % reason_str
25220 Returns the frame's resume address.
25223 @defun Frame.block ()
25224 Return the frame's code block. @xref{Blocks In Python}.
25227 @defun Frame.function ()
25228 Return the symbol for the function corresponding to this frame.
25229 @xref{Symbols In Python}.
25232 @defun Frame.older ()
25233 Return the frame that called this frame.
25236 @defun Frame.newer ()
25237 Return the frame called by this frame.
25240 @defun Frame.find_sal ()
25241 Return the frame's symtab and line object.
25242 @xref{Symbol Tables In Python}.
25245 @defun Frame.read_var (variable @r{[}, block@r{]})
25246 Return the value of @var{variable} in this frame. If the optional
25247 argument @var{block} is provided, search for the variable from that
25248 block; otherwise start at the frame's current block (which is
25249 determined by the frame's current program counter). @var{variable}
25250 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25251 @code{gdb.Block} object.
25254 @defun Frame.select ()
25255 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25259 @node Blocks In Python
25260 @subsubsection Accessing frame blocks from Python.
25262 @cindex blocks in python
25265 Within each frame, @value{GDBN} maintains information on each block
25266 stored in that frame. These blocks are organized hierarchically, and
25267 are represented individually in Python as a @code{gdb.Block}.
25268 Please see @ref{Frames In Python}, for a more in-depth discussion on
25269 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25270 detailed technical information on @value{GDBN}'s book-keeping of the
25273 A @code{gdb.Block} is iterable. The iterator returns the symbols
25274 (@pxref{Symbols In Python}) local to the block. Python programs
25275 should not assume that a specific block object will always contain a
25276 given symbol, since changes in @value{GDBN} features and
25277 infrastructure may cause symbols move across blocks in a symbol
25280 The following block-related functions are available in the @code{gdb}
25283 @findex gdb.block_for_pc
25284 @defun gdb.block_for_pc (pc)
25285 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25286 block cannot be found for the @var{pc} value specified, the function
25287 will return @code{None}.
25290 A @code{gdb.Block} object has the following methods:
25292 @defun Block.is_valid ()
25293 Returns @code{True} if the @code{gdb.Block} object is valid,
25294 @code{False} if not. A block object can become invalid if the block it
25295 refers to doesn't exist anymore in the inferior. All other
25296 @code{gdb.Block} methods will throw an exception if it is invalid at
25297 the time the method is called. The block's validity is also checked
25298 during iteration over symbols of the block.
25301 A @code{gdb.Block} object has the following attributes:
25303 @defvar Block.start
25304 The start address of the block. This attribute is not writable.
25308 The end address of the block. This attribute is not writable.
25311 @defvar Block.function
25312 The name of the block represented as a @code{gdb.Symbol}. If the
25313 block is not named, then this attribute holds @code{None}. This
25314 attribute is not writable.
25317 @defvar Block.superblock
25318 The block containing this block. If this parent block does not exist,
25319 this attribute holds @code{None}. This attribute is not writable.
25322 @defvar Block.global_block
25323 The global block associated with this block. This attribute is not
25327 @defvar Block.static_block
25328 The static block associated with this block. This attribute is not
25332 @defvar Block.is_global
25333 @code{True} if the @code{gdb.Block} object is a global block,
25334 @code{False} if not. This attribute is not
25338 @defvar Block.is_static
25339 @code{True} if the @code{gdb.Block} object is a static block,
25340 @code{False} if not. This attribute is not writable.
25343 @node Symbols In Python
25344 @subsubsection Python representation of Symbols.
25346 @cindex symbols in python
25349 @value{GDBN} represents every variable, function and type as an
25350 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25351 Similarly, Python represents these symbols in @value{GDBN} with the
25352 @code{gdb.Symbol} object.
25354 The following symbol-related functions are available in the @code{gdb}
25357 @findex gdb.lookup_symbol
25358 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25359 This function searches for a symbol by name. The search scope can be
25360 restricted to the parameters defined in the optional domain and block
25363 @var{name} is the name of the symbol. It must be a string. The
25364 optional @var{block} argument restricts the search to symbols visible
25365 in that @var{block}. The @var{block} argument must be a
25366 @code{gdb.Block} object. If omitted, the block for the current frame
25367 is used. The optional @var{domain} argument restricts
25368 the search to the domain type. The @var{domain} argument must be a
25369 domain constant defined in the @code{gdb} module and described later
25372 The result is a tuple of two elements.
25373 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25375 If the symbol is found, the second element is @code{True} if the symbol
25376 is a field of a method's object (e.g., @code{this} in C@t{++}),
25377 otherwise it is @code{False}.
25378 If the symbol is not found, the second element is @code{False}.
25381 @findex gdb.lookup_global_symbol
25382 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25383 This function searches for a global symbol by name.
25384 The search scope can be restricted to by the domain argument.
25386 @var{name} is the name of the symbol. It must be a string.
25387 The optional @var{domain} argument restricts the search to the domain type.
25388 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25389 module and described later in this chapter.
25391 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25395 A @code{gdb.Symbol} object has the following attributes:
25397 @defvar Symbol.type
25398 The type of the symbol or @code{None} if no type is recorded.
25399 This attribute is represented as a @code{gdb.Type} object.
25400 @xref{Types In Python}. This attribute is not writable.
25403 @defvar Symbol.symtab
25404 The symbol table in which the symbol appears. This attribute is
25405 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25406 Python}. This attribute is not writable.
25409 @defvar Symbol.line
25410 The line number in the source code at which the symbol was defined.
25411 This is an integer.
25414 @defvar Symbol.name
25415 The name of the symbol as a string. This attribute is not writable.
25418 @defvar Symbol.linkage_name
25419 The name of the symbol, as used by the linker (i.e., may be mangled).
25420 This attribute is not writable.
25423 @defvar Symbol.print_name
25424 The name of the symbol in a form suitable for output. This is either
25425 @code{name} or @code{linkage_name}, depending on whether the user
25426 asked @value{GDBN} to display demangled or mangled names.
25429 @defvar Symbol.addr_class
25430 The address class of the symbol. This classifies how to find the value
25431 of a symbol. Each address class is a constant defined in the
25432 @code{gdb} module and described later in this chapter.
25435 @defvar Symbol.needs_frame
25436 This is @code{True} if evaluating this symbol's value requires a frame
25437 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25438 local variables will require a frame, but other symbols will not.
25441 @defvar Symbol.is_argument
25442 @code{True} if the symbol is an argument of a function.
25445 @defvar Symbol.is_constant
25446 @code{True} if the symbol is a constant.
25449 @defvar Symbol.is_function
25450 @code{True} if the symbol is a function or a method.
25453 @defvar Symbol.is_variable
25454 @code{True} if the symbol is a variable.
25457 A @code{gdb.Symbol} object has the following methods:
25459 @defun Symbol.is_valid ()
25460 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25461 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25462 the symbol it refers to does not exist in @value{GDBN} any longer.
25463 All other @code{gdb.Symbol} methods will throw an exception if it is
25464 invalid at the time the method is called.
25467 @defun Symbol.value (@r{[}frame@r{]})
25468 Compute the value of the symbol, as a @code{gdb.Value}. For
25469 functions, this computes the address of the function, cast to the
25470 appropriate type. If the symbol requires a frame in order to compute
25471 its value, then @var{frame} must be given. If @var{frame} is not
25472 given, or if @var{frame} is invalid, then this method will throw an
25476 The available domain categories in @code{gdb.Symbol} are represented
25477 as constants in the @code{gdb} module:
25480 @findex SYMBOL_UNDEF_DOMAIN
25481 @findex gdb.SYMBOL_UNDEF_DOMAIN
25482 @item gdb.SYMBOL_UNDEF_DOMAIN
25483 This is used when a domain has not been discovered or none of the
25484 following domains apply. This usually indicates an error either
25485 in the symbol information or in @value{GDBN}'s handling of symbols.
25486 @findex SYMBOL_VAR_DOMAIN
25487 @findex gdb.SYMBOL_VAR_DOMAIN
25488 @item gdb.SYMBOL_VAR_DOMAIN
25489 This domain contains variables, function names, typedef names and enum
25491 @findex SYMBOL_STRUCT_DOMAIN
25492 @findex gdb.SYMBOL_STRUCT_DOMAIN
25493 @item gdb.SYMBOL_STRUCT_DOMAIN
25494 This domain holds struct, union and enum type names.
25495 @findex SYMBOL_LABEL_DOMAIN
25496 @findex gdb.SYMBOL_LABEL_DOMAIN
25497 @item gdb.SYMBOL_LABEL_DOMAIN
25498 This domain contains names of labels (for gotos).
25499 @findex SYMBOL_VARIABLES_DOMAIN
25500 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25501 @item gdb.SYMBOL_VARIABLES_DOMAIN
25502 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25503 contains everything minus functions and types.
25504 @findex SYMBOL_FUNCTIONS_DOMAIN
25505 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25506 @item gdb.SYMBOL_FUNCTION_DOMAIN
25507 This domain contains all functions.
25508 @findex SYMBOL_TYPES_DOMAIN
25509 @findex gdb.SYMBOL_TYPES_DOMAIN
25510 @item gdb.SYMBOL_TYPES_DOMAIN
25511 This domain contains all types.
25514 The available address class categories in @code{gdb.Symbol} are represented
25515 as constants in the @code{gdb} module:
25518 @findex SYMBOL_LOC_UNDEF
25519 @findex gdb.SYMBOL_LOC_UNDEF
25520 @item gdb.SYMBOL_LOC_UNDEF
25521 If this is returned by address class, it indicates an error either in
25522 the symbol information or in @value{GDBN}'s handling of symbols.
25523 @findex SYMBOL_LOC_CONST
25524 @findex gdb.SYMBOL_LOC_CONST
25525 @item gdb.SYMBOL_LOC_CONST
25526 Value is constant int.
25527 @findex SYMBOL_LOC_STATIC
25528 @findex gdb.SYMBOL_LOC_STATIC
25529 @item gdb.SYMBOL_LOC_STATIC
25530 Value is at a fixed address.
25531 @findex SYMBOL_LOC_REGISTER
25532 @findex gdb.SYMBOL_LOC_REGISTER
25533 @item gdb.SYMBOL_LOC_REGISTER
25534 Value is in a register.
25535 @findex SYMBOL_LOC_ARG
25536 @findex gdb.SYMBOL_LOC_ARG
25537 @item gdb.SYMBOL_LOC_ARG
25538 Value is an argument. This value is at the offset stored within the
25539 symbol inside the frame's argument list.
25540 @findex SYMBOL_LOC_REF_ARG
25541 @findex gdb.SYMBOL_LOC_REF_ARG
25542 @item gdb.SYMBOL_LOC_REF_ARG
25543 Value address is stored in the frame's argument list. Just like
25544 @code{LOC_ARG} except that the value's address is stored at the
25545 offset, not the value itself.
25546 @findex SYMBOL_LOC_REGPARM_ADDR
25547 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25548 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25549 Value is a specified register. Just like @code{LOC_REGISTER} except
25550 the register holds the address of the argument instead of the argument
25552 @findex SYMBOL_LOC_LOCAL
25553 @findex gdb.SYMBOL_LOC_LOCAL
25554 @item gdb.SYMBOL_LOC_LOCAL
25555 Value is a local variable.
25556 @findex SYMBOL_LOC_TYPEDEF
25557 @findex gdb.SYMBOL_LOC_TYPEDEF
25558 @item gdb.SYMBOL_LOC_TYPEDEF
25559 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25561 @findex SYMBOL_LOC_BLOCK
25562 @findex gdb.SYMBOL_LOC_BLOCK
25563 @item gdb.SYMBOL_LOC_BLOCK
25565 @findex SYMBOL_LOC_CONST_BYTES
25566 @findex gdb.SYMBOL_LOC_CONST_BYTES
25567 @item gdb.SYMBOL_LOC_CONST_BYTES
25568 Value is a byte-sequence.
25569 @findex SYMBOL_LOC_UNRESOLVED
25570 @findex gdb.SYMBOL_LOC_UNRESOLVED
25571 @item gdb.SYMBOL_LOC_UNRESOLVED
25572 Value is at a fixed address, but the address of the variable has to be
25573 determined from the minimal symbol table whenever the variable is
25575 @findex SYMBOL_LOC_OPTIMIZED_OUT
25576 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25577 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25578 The value does not actually exist in the program.
25579 @findex SYMBOL_LOC_COMPUTED
25580 @findex gdb.SYMBOL_LOC_COMPUTED
25581 @item gdb.SYMBOL_LOC_COMPUTED
25582 The value's address is a computed location.
25585 @node Symbol Tables In Python
25586 @subsubsection Symbol table representation in Python.
25588 @cindex symbol tables in python
25590 @tindex gdb.Symtab_and_line
25592 Access to symbol table data maintained by @value{GDBN} on the inferior
25593 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25594 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25595 from the @code{find_sal} method in @code{gdb.Frame} object.
25596 @xref{Frames In Python}.
25598 For more information on @value{GDBN}'s symbol table management, see
25599 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25601 A @code{gdb.Symtab_and_line} object has the following attributes:
25603 @defvar Symtab_and_line.symtab
25604 The symbol table object (@code{gdb.Symtab}) for this frame.
25605 This attribute is not writable.
25608 @defvar Symtab_and_line.pc
25609 Indicates the start of the address range occupied by code for the
25610 current source line. This attribute is not writable.
25613 @defvar Symtab_and_line.last
25614 Indicates the end of the address range occupied by code for the current
25615 source line. This attribute is not writable.
25618 @defvar Symtab_and_line.line
25619 Indicates the current line number for this object. This
25620 attribute is not writable.
25623 A @code{gdb.Symtab_and_line} object has the following methods:
25625 @defun Symtab_and_line.is_valid ()
25626 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25627 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25628 invalid if the Symbol table and line object it refers to does not
25629 exist in @value{GDBN} any longer. All other
25630 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25631 invalid at the time the method is called.
25634 A @code{gdb.Symtab} object has the following attributes:
25636 @defvar Symtab.filename
25637 The symbol table's source filename. This attribute is not writable.
25640 @defvar Symtab.objfile
25641 The symbol table's backing object file. @xref{Objfiles In Python}.
25642 This attribute is not writable.
25645 A @code{gdb.Symtab} object has the following methods:
25647 @defun Symtab.is_valid ()
25648 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25649 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25650 the symbol table it refers to does not exist in @value{GDBN} any
25651 longer. All other @code{gdb.Symtab} methods will throw an exception
25652 if it is invalid at the time the method is called.
25655 @defun Symtab.fullname ()
25656 Return the symbol table's source absolute file name.
25659 @defun Symtab.global_block ()
25660 Return the global block of the underlying symbol table.
25661 @xref{Blocks In Python}.
25664 @defun Symtab.static_block ()
25665 Return the static block of the underlying symbol table.
25666 @xref{Blocks In Python}.
25669 @node Breakpoints In Python
25670 @subsubsection Manipulating breakpoints using Python
25672 @cindex breakpoints in python
25673 @tindex gdb.Breakpoint
25675 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25678 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25679 Create a new breakpoint. @var{spec} is a string naming the
25680 location of the breakpoint, or an expression that defines a
25681 watchpoint. The contents can be any location recognized by the
25682 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25683 command. The optional @var{type} denotes the breakpoint to create
25684 from the types defined later in this chapter. This argument can be
25685 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25686 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25687 allows the breakpoint to become invisible to the user. The breakpoint
25688 will neither be reported when created, nor will it be listed in the
25689 output from @code{info breakpoints} (but will be listed with the
25690 @code{maint info breakpoints} command). The optional @var{wp_class}
25691 argument defines the class of watchpoint to create, if @var{type} is
25692 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25693 assumed to be a @code{gdb.WP_WRITE} class.
25696 @defun Breakpoint.stop (self)
25697 The @code{gdb.Breakpoint} class can be sub-classed and, in
25698 particular, you may choose to implement the @code{stop} method.
25699 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25700 it will be called when the inferior reaches any location of a
25701 breakpoint which instantiates that sub-class. If the method returns
25702 @code{True}, the inferior will be stopped at the location of the
25703 breakpoint, otherwise the inferior will continue.
25705 If there are multiple breakpoints at the same location with a
25706 @code{stop} method, each one will be called regardless of the
25707 return status of the previous. This ensures that all @code{stop}
25708 methods have a chance to execute at that location. In this scenario
25709 if one of the methods returns @code{True} but the others return
25710 @code{False}, the inferior will still be stopped.
25712 You should not alter the execution state of the inferior (i.e.@:, step,
25713 next, etc.), alter the current frame context (i.e.@:, change the current
25714 active frame), or alter, add or delete any breakpoint. As a general
25715 rule, you should not alter any data within @value{GDBN} or the inferior
25718 Example @code{stop} implementation:
25721 class MyBreakpoint (gdb.Breakpoint):
25723 inf_val = gdb.parse_and_eval("foo")
25730 The available watchpoint types represented by constants are defined in the
25735 @findex gdb.WP_READ
25737 Read only watchpoint.
25740 @findex gdb.WP_WRITE
25742 Write only watchpoint.
25745 @findex gdb.WP_ACCESS
25746 @item gdb.WP_ACCESS
25747 Read/Write watchpoint.
25750 @defun Breakpoint.is_valid ()
25751 Return @code{True} if this @code{Breakpoint} object is valid,
25752 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25753 if the user deletes the breakpoint. In this case, the object still
25754 exists, but the underlying breakpoint does not. In the cases of
25755 watchpoint scope, the watchpoint remains valid even if execution of the
25756 inferior leaves the scope of that watchpoint.
25759 @defun Breakpoint.delete
25760 Permanently deletes the @value{GDBN} breakpoint. This also
25761 invalidates the Python @code{Breakpoint} object. Any further access
25762 to this object's attributes or methods will raise an error.
25765 @defvar Breakpoint.enabled
25766 This attribute is @code{True} if the breakpoint is enabled, and
25767 @code{False} otherwise. This attribute is writable.
25770 @defvar Breakpoint.silent
25771 This attribute is @code{True} if the breakpoint is silent, and
25772 @code{False} otherwise. This attribute is writable.
25774 Note that a breakpoint can also be silent if it has commands and the
25775 first command is @code{silent}. This is not reported by the
25776 @code{silent} attribute.
25779 @defvar Breakpoint.thread
25780 If the breakpoint is thread-specific, this attribute holds the thread
25781 id. If the breakpoint is not thread-specific, this attribute is
25782 @code{None}. This attribute is writable.
25785 @defvar Breakpoint.task
25786 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25787 id. If the breakpoint is not task-specific (or the underlying
25788 language is not Ada), this attribute is @code{None}. This attribute
25792 @defvar Breakpoint.ignore_count
25793 This attribute holds the ignore count for the breakpoint, an integer.
25794 This attribute is writable.
25797 @defvar Breakpoint.number
25798 This attribute holds the breakpoint's number --- the identifier used by
25799 the user to manipulate the breakpoint. This attribute is not writable.
25802 @defvar Breakpoint.type
25803 This attribute holds the breakpoint's type --- the identifier used to
25804 determine the actual breakpoint type or use-case. This attribute is not
25808 @defvar Breakpoint.visible
25809 This attribute tells whether the breakpoint is visible to the user
25810 when set, or when the @samp{info breakpoints} command is run. This
25811 attribute is not writable.
25814 The available types are represented by constants defined in the @code{gdb}
25818 @findex BP_BREAKPOINT
25819 @findex gdb.BP_BREAKPOINT
25820 @item gdb.BP_BREAKPOINT
25821 Normal code breakpoint.
25823 @findex BP_WATCHPOINT
25824 @findex gdb.BP_WATCHPOINT
25825 @item gdb.BP_WATCHPOINT
25826 Watchpoint breakpoint.
25828 @findex BP_HARDWARE_WATCHPOINT
25829 @findex gdb.BP_HARDWARE_WATCHPOINT
25830 @item gdb.BP_HARDWARE_WATCHPOINT
25831 Hardware assisted watchpoint.
25833 @findex BP_READ_WATCHPOINT
25834 @findex gdb.BP_READ_WATCHPOINT
25835 @item gdb.BP_READ_WATCHPOINT
25836 Hardware assisted read watchpoint.
25838 @findex BP_ACCESS_WATCHPOINT
25839 @findex gdb.BP_ACCESS_WATCHPOINT
25840 @item gdb.BP_ACCESS_WATCHPOINT
25841 Hardware assisted access watchpoint.
25844 @defvar Breakpoint.hit_count
25845 This attribute holds the hit count for the breakpoint, an integer.
25846 This attribute is writable, but currently it can only be set to zero.
25849 @defvar Breakpoint.location
25850 This attribute holds the location of the breakpoint, as specified by
25851 the user. It is a string. If the breakpoint does not have a location
25852 (that is, it is a watchpoint) the attribute's value is @code{None}. This
25853 attribute is not writable.
25856 @defvar Breakpoint.expression
25857 This attribute holds a breakpoint expression, as specified by
25858 the user. It is a string. If the breakpoint does not have an
25859 expression (the breakpoint is not a watchpoint) the attribute's value
25860 is @code{None}. This attribute is not writable.
25863 @defvar Breakpoint.condition
25864 This attribute holds the condition of the breakpoint, as specified by
25865 the user. It is a string. If there is no condition, this attribute's
25866 value is @code{None}. This attribute is writable.
25869 @defvar Breakpoint.commands
25870 This attribute holds the commands attached to the breakpoint. If
25871 there are commands, this attribute's value is a string holding all the
25872 commands, separated by newlines. If there are no commands, this
25873 attribute is @code{None}. This attribute is not writable.
25876 @node Finish Breakpoints in Python
25877 @subsubsection Finish Breakpoints
25879 @cindex python finish breakpoints
25880 @tindex gdb.FinishBreakpoint
25882 A finish breakpoint is a temporary breakpoint set at the return address of
25883 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
25884 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
25885 and deleted when the execution will run out of the breakpoint scope (i.e.@:
25886 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
25887 Finish breakpoints are thread specific and must be create with the right
25890 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
25891 Create a finish breakpoint at the return address of the @code{gdb.Frame}
25892 object @var{frame}. If @var{frame} is not provided, this defaults to the
25893 newest frame. The optional @var{internal} argument allows the breakpoint to
25894 become invisible to the user. @xref{Breakpoints In Python}, for further
25895 details about this argument.
25898 @defun FinishBreakpoint.out_of_scope (self)
25899 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
25900 @code{return} command, @dots{}), a function may not properly terminate, and
25901 thus never hit the finish breakpoint. When @value{GDBN} notices such a
25902 situation, the @code{out_of_scope} callback will be triggered.
25904 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
25908 class MyFinishBreakpoint (gdb.FinishBreakpoint)
25910 print "normal finish"
25913 def out_of_scope ():
25914 print "abnormal finish"
25918 @defvar FinishBreakpoint.return_value
25919 When @value{GDBN} is stopped at a finish breakpoint and the frame
25920 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
25921 attribute will contain a @code{gdb.Value} object corresponding to the return
25922 value of the function. The value will be @code{None} if the function return
25923 type is @code{void} or if the return value was not computable. This attribute
25927 @node Lazy Strings In Python
25928 @subsubsection Python representation of lazy strings.
25930 @cindex lazy strings in python
25931 @tindex gdb.LazyString
25933 A @dfn{lazy string} is a string whose contents is not retrieved or
25934 encoded until it is needed.
25936 A @code{gdb.LazyString} is represented in @value{GDBN} as an
25937 @code{address} that points to a region of memory, an @code{encoding}
25938 that will be used to encode that region of memory, and a @code{length}
25939 to delimit the region of memory that represents the string. The
25940 difference between a @code{gdb.LazyString} and a string wrapped within
25941 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
25942 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
25943 retrieved and encoded during printing, while a @code{gdb.Value}
25944 wrapping a string is immediately retrieved and encoded on creation.
25946 A @code{gdb.LazyString} object has the following functions:
25948 @defun LazyString.value ()
25949 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
25950 will point to the string in memory, but will lose all the delayed
25951 retrieval, encoding and handling that @value{GDBN} applies to a
25952 @code{gdb.LazyString}.
25955 @defvar LazyString.address
25956 This attribute holds the address of the string. This attribute is not
25960 @defvar LazyString.length
25961 This attribute holds the length of the string in characters. If the
25962 length is -1, then the string will be fetched and encoded up to the
25963 first null of appropriate width. This attribute is not writable.
25966 @defvar LazyString.encoding
25967 This attribute holds the encoding that will be applied to the string
25968 when the string is printed by @value{GDBN}. If the encoding is not
25969 set, or contains an empty string, then @value{GDBN} will select the
25970 most appropriate encoding when the string is printed. This attribute
25974 @defvar LazyString.type
25975 This attribute holds the type that is represented by the lazy string's
25976 type. For a lazy string this will always be a pointer type. To
25977 resolve this to the lazy string's character type, use the type's
25978 @code{target} method. @xref{Types In Python}. This attribute is not
25982 @node Architectures In Python
25983 @subsubsection Python representation of architectures
25984 @cindex Python architectures
25986 @value{GDBN} uses architecture specific parameters and artifacts in a
25987 number of its various computations. An architecture is represented
25988 by an instance of the @code{gdb.Architecture} class.
25990 A @code{gdb.Architecture} class has the following methods:
25992 @defun Architecture.name ()
25993 Return the name (string value) of the architecture.
25996 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
25997 Return a list of disassembled instructions starting from the memory
25998 address @var{start_pc}. The optional arguments @var{end_pc} and
25999 @var{count} determine the number of instructions in the returned list.
26000 If both the optional arguments @var{end_pc} and @var{count} are
26001 specified, then a list of at most @var{count} disassembled instructions
26002 whose start address falls in the closed memory address interval from
26003 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
26004 specified, but @var{count} is specified, then @var{count} number of
26005 instructions starting from the address @var{start_pc} are returned. If
26006 @var{count} is not specified but @var{end_pc} is specified, then all
26007 instructions whose start address falls in the closed memory address
26008 interval from @var{start_pc} to @var{end_pc} are returned. If neither
26009 @var{end_pc} nor @var{count} are specified, then a single instruction at
26010 @var{start_pc} is returned. For all of these cases, each element of the
26011 returned list is a Python @code{dict} with the following string keys:
26016 The value corresponding to this key is a Python long integer capturing
26017 the memory address of the instruction.
26020 The value corresponding to this key is a string value which represents
26021 the instruction with assembly language mnemonics. The assembly
26022 language flavor used is the same as that specified by the current CLI
26023 variable @code{disassembly-flavor}. @xref{Machine Code}.
26026 The value corresponding to this key is the length (integer value) of the
26027 instruction in bytes.
26032 @node Python Auto-loading
26033 @subsection Python Auto-loading
26034 @cindex Python auto-loading
26036 When a new object file is read (for example, due to the @code{file}
26037 command, or because the inferior has loaded a shared library),
26038 @value{GDBN} will look for Python support scripts in several ways:
26039 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
26040 and @code{.debug_gdb_scripts} section
26041 (@pxref{dotdebug_gdb_scripts section}).
26043 The auto-loading feature is useful for supplying application-specific
26044 debugging commands and scripts.
26046 Auto-loading can be enabled or disabled,
26047 and the list of auto-loaded scripts can be printed.
26050 @anchor{set auto-load python-scripts}
26051 @kindex set auto-load python-scripts
26052 @item set auto-load python-scripts [on|off]
26053 Enable or disable the auto-loading of Python scripts.
26055 @anchor{show auto-load python-scripts}
26056 @kindex show auto-load python-scripts
26057 @item show auto-load python-scripts
26058 Show whether auto-loading of Python scripts is enabled or disabled.
26060 @anchor{info auto-load python-scripts}
26061 @kindex info auto-load python-scripts
26062 @cindex print list of auto-loaded Python scripts
26063 @item info auto-load python-scripts [@var{regexp}]
26064 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26066 Also printed is the list of Python scripts that were mentioned in
26067 the @code{.debug_gdb_scripts} section and were not found
26068 (@pxref{dotdebug_gdb_scripts section}).
26069 This is useful because their names are not printed when @value{GDBN}
26070 tries to load them and fails. There may be many of them, and printing
26071 an error message for each one is problematic.
26073 If @var{regexp} is supplied only Python scripts with matching names are printed.
26078 (gdb) info auto-load python-scripts
26080 Yes py-section-script.py
26081 full name: /tmp/py-section-script.py
26082 No my-foo-pretty-printers.py
26086 When reading an auto-loaded file, @value{GDBN} sets the
26087 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26088 function (@pxref{Objfiles In Python}). This can be useful for
26089 registering objfile-specific pretty-printers.
26092 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26093 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26094 * Which flavor to choose?::
26097 @node objfile-gdb.py file
26098 @subsubsection The @file{@var{objfile}-gdb.py} file
26099 @cindex @file{@var{objfile}-gdb.py}
26101 When a new object file is read, @value{GDBN} looks for
26102 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26103 where @var{objfile} is the object file's real name, formed by ensuring
26104 that the file name is absolute, following all symlinks, and resolving
26105 @code{.} and @code{..} components. If this file exists and is
26106 readable, @value{GDBN} will evaluate it as a Python script.
26108 If this file does not exist, then @value{GDBN} will look for
26109 @var{script-name} file in all of the directories as specified below.
26111 Note that loading of this script file also requires accordingly configured
26112 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26114 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26115 scripts normally according to its @file{.exe} filename. But if no scripts are
26116 found @value{GDBN} also tries script filenames matching the object file without
26117 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26118 is attempted on any platform. This makes the script filenames compatible
26119 between Unix and MS-Windows hosts.
26122 @anchor{set auto-load scripts-directory}
26123 @kindex set auto-load scripts-directory
26124 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26125 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26126 may be delimited by the host platform path separator in use
26127 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26129 Each entry here needs to be covered also by the security setting
26130 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26132 @anchor{with-auto-load-dir}
26133 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26134 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26135 configuration option @option{--with-auto-load-dir}.
26137 Any reference to @file{$debugdir} will get replaced by
26138 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26139 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26140 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26141 @file{$datadir} must be placed as a directory component --- either alone or
26142 delimited by @file{/} or @file{\} directory separators, depending on the host
26145 The list of directories uses path separator (@samp{:} on GNU and Unix
26146 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26147 to the @env{PATH} environment variable.
26149 @anchor{show auto-load scripts-directory}
26150 @kindex show auto-load scripts-directory
26151 @item show auto-load scripts-directory
26152 Show @value{GDBN} auto-loaded scripts location.
26155 @value{GDBN} does not track which files it has already auto-loaded this way.
26156 @value{GDBN} will load the associated script every time the corresponding
26157 @var{objfile} is opened.
26158 So your @file{-gdb.py} file should be careful to avoid errors if it
26159 is evaluated more than once.
26161 @node dotdebug_gdb_scripts section
26162 @subsubsection The @code{.debug_gdb_scripts} section
26163 @cindex @code{.debug_gdb_scripts} section
26165 For systems using file formats like ELF and COFF,
26166 when @value{GDBN} loads a new object file
26167 it will look for a special section named @samp{.debug_gdb_scripts}.
26168 If this section exists, its contents is a list of names of scripts to load.
26170 @value{GDBN} will look for each specified script file first in the
26171 current directory and then along the source search path
26172 (@pxref{Source Path, ,Specifying Source Directories}),
26173 except that @file{$cdir} is not searched, since the compilation
26174 directory is not relevant to scripts.
26176 Entries can be placed in section @code{.debug_gdb_scripts} with,
26177 for example, this GCC macro:
26180 /* Note: The "MS" section flags are to remove duplicates. */
26181 #define DEFINE_GDB_SCRIPT(script_name) \
26183 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26185 .asciz \"" script_name "\"\n\
26191 Then one can reference the macro in a header or source file like this:
26194 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26197 The script name may include directories if desired.
26199 Note that loading of this script file also requires accordingly configured
26200 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26202 If the macro is put in a header, any application or library
26203 using this header will get a reference to the specified script.
26205 @node Which flavor to choose?
26206 @subsubsection Which flavor to choose?
26208 Given the multiple ways of auto-loading Python scripts, it might not always
26209 be clear which one to choose. This section provides some guidance.
26211 Benefits of the @file{-gdb.py} way:
26215 Can be used with file formats that don't support multiple sections.
26218 Ease of finding scripts for public libraries.
26220 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26221 in the source search path.
26222 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26223 isn't a source directory in which to find the script.
26226 Doesn't require source code additions.
26229 Benefits of the @code{.debug_gdb_scripts} way:
26233 Works with static linking.
26235 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26236 trigger their loading. When an application is statically linked the only
26237 objfile available is the executable, and it is cumbersome to attach all the
26238 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26241 Works with classes that are entirely inlined.
26243 Some classes can be entirely inlined, and thus there may not be an associated
26244 shared library to attach a @file{-gdb.py} script to.
26247 Scripts needn't be copied out of the source tree.
26249 In some circumstances, apps can be built out of large collections of internal
26250 libraries, and the build infrastructure necessary to install the
26251 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26252 cumbersome. It may be easier to specify the scripts in the
26253 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26254 top of the source tree to the source search path.
26257 @node Python modules
26258 @subsection Python modules
26259 @cindex python modules
26261 @value{GDBN} comes with several modules to assist writing Python code.
26264 * gdb.printing:: Building and registering pretty-printers.
26265 * gdb.types:: Utilities for working with types.
26266 * gdb.prompt:: Utilities for prompt value substitution.
26270 @subsubsection gdb.printing
26271 @cindex gdb.printing
26273 This module provides a collection of utilities for working with
26277 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26278 This class specifies the API that makes @samp{info pretty-printer},
26279 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26280 Pretty-printers should generally inherit from this class.
26282 @item SubPrettyPrinter (@var{name})
26283 For printers that handle multiple types, this class specifies the
26284 corresponding API for the subprinters.
26286 @item RegexpCollectionPrettyPrinter (@var{name})
26287 Utility class for handling multiple printers, all recognized via
26288 regular expressions.
26289 @xref{Writing a Pretty-Printer}, for an example.
26291 @item FlagEnumerationPrinter (@var{name})
26292 A pretty-printer which handles printing of @code{enum} values. Unlike
26293 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26294 work properly when there is some overlap between the enumeration
26295 constants. @var{name} is the name of the printer and also the name of
26296 the @code{enum} type to look up.
26298 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26299 Register @var{printer} with the pretty-printer list of @var{obj}.
26300 If @var{replace} is @code{True} then any existing copy of the printer
26301 is replaced. Otherwise a @code{RuntimeError} exception is raised
26302 if a printer with the same name already exists.
26306 @subsubsection gdb.types
26309 This module provides a collection of utilities for working with
26310 @code{gdb.Type} objects.
26313 @item get_basic_type (@var{type})
26314 Return @var{type} with const and volatile qualifiers stripped,
26315 and with typedefs and C@t{++} references converted to the underlying type.
26320 typedef const int const_int;
26322 const_int& foo_ref (foo);
26323 int main () @{ return 0; @}
26330 (gdb) python import gdb.types
26331 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26332 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26336 @item has_field (@var{type}, @var{field})
26337 Return @code{True} if @var{type}, assumed to be a type with fields
26338 (e.g., a structure or union), has field @var{field}.
26340 @item make_enum_dict (@var{enum_type})
26341 Return a Python @code{dictionary} type produced from @var{enum_type}.
26343 @item deep_items (@var{type})
26344 Returns a Python iterator similar to the standard
26345 @code{gdb.Type.iteritems} method, except that the iterator returned
26346 by @code{deep_items} will recursively traverse anonymous struct or
26347 union fields. For example:
26361 Then in @value{GDBN}:
26363 (@value{GDBP}) python import gdb.types
26364 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26365 (@value{GDBP}) python print struct_a.keys ()
26367 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26368 @{['a', 'b0', 'b1']@}
26371 @item get_type_recognizers ()
26372 Return a list of the enabled type recognizers for the current context.
26373 This is called by @value{GDBN} during the type-printing process
26374 (@pxref{Type Printing API}).
26376 @item apply_type_recognizers (recognizers, type_obj)
26377 Apply the type recognizers, @var{recognizers}, to the type object
26378 @var{type_obj}. If any recognizer returns a string, return that
26379 string. Otherwise, return @code{None}. This is called by
26380 @value{GDBN} during the type-printing process (@pxref{Type Printing
26383 @item register_type_printer (locus, printer)
26384 This is a convenience function to register a type printer.
26385 @var{printer} is the type printer to register. It must implement the
26386 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26387 which case the printer is registered with that objfile; a
26388 @code{gdb.Progspace}, in which case the printer is registered with
26389 that progspace; or @code{None}, in which case the printer is
26390 registered globally.
26393 This is a base class that implements the type printer protocol. Type
26394 printers are encouraged, but not required, to derive from this class.
26395 It defines a constructor:
26397 @defmethod TypePrinter __init__ (self, name)
26398 Initialize the type printer with the given name. The new printer
26399 starts in the enabled state.
26405 @subsubsection gdb.prompt
26408 This module provides a method for prompt value-substitution.
26411 @item substitute_prompt (@var{string})
26412 Return @var{string} with escape sequences substituted by values. Some
26413 escape sequences take arguments. You can specify arguments inside
26414 ``@{@}'' immediately following the escape sequence.
26416 The escape sequences you can pass to this function are:
26420 Substitute a backslash.
26422 Substitute an ESC character.
26424 Substitute the selected frame; an argument names a frame parameter.
26426 Substitute a newline.
26428 Substitute a parameter's value; the argument names the parameter.
26430 Substitute a carriage return.
26432 Substitute the selected thread; an argument names a thread parameter.
26434 Substitute the version of GDB.
26436 Substitute the current working directory.
26438 Begin a sequence of non-printing characters. These sequences are
26439 typically used with the ESC character, and are not counted in the string
26440 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26441 blue-colored ``(gdb)'' prompt where the length is five.
26443 End a sequence of non-printing characters.
26449 substitute_prompt (``frame: \f,
26450 print arguments: \p@{print frame-arguments@}'')
26453 @exdent will return the string:
26456 "frame: main, print arguments: scalars"
26461 @section Creating new spellings of existing commands
26462 @cindex aliases for commands
26464 It is often useful to define alternate spellings of existing commands.
26465 For example, if a new @value{GDBN} command defined in Python has
26466 a long name to type, it is handy to have an abbreviated version of it
26467 that involves less typing.
26469 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26470 of the @samp{step} command even though it is otherwise an ambiguous
26471 abbreviation of other commands like @samp{set} and @samp{show}.
26473 Aliases are also used to provide shortened or more common versions
26474 of multi-word commands. For example, @value{GDBN} provides the
26475 @samp{tty} alias of the @samp{set inferior-tty} command.
26477 You can define a new alias with the @samp{alias} command.
26482 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26486 @var{ALIAS} specifies the name of the new alias.
26487 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26490 @var{COMMAND} specifies the name of an existing command
26491 that is being aliased.
26493 The @samp{-a} option specifies that the new alias is an abbreviation
26494 of the command. Abbreviations are not shown in command
26495 lists displayed by the @samp{help} command.
26497 The @samp{--} option specifies the end of options,
26498 and is useful when @var{ALIAS} begins with a dash.
26500 Here is a simple example showing how to make an abbreviation
26501 of a command so that there is less to type.
26502 Suppose you were tired of typing @samp{disas}, the current
26503 shortest unambiguous abbreviation of the @samp{disassemble} command
26504 and you wanted an even shorter version named @samp{di}.
26505 The following will accomplish this.
26508 (gdb) alias -a di = disas
26511 Note that aliases are different from user-defined commands.
26512 With a user-defined command, you also need to write documentation
26513 for it with the @samp{document} command.
26514 An alias automatically picks up the documentation of the existing command.
26516 Here is an example where we make @samp{elms} an abbreviation of
26517 @samp{elements} in the @samp{set print elements} command.
26518 This is to show that you can make an abbreviation of any part
26522 (gdb) alias -a set print elms = set print elements
26523 (gdb) alias -a show print elms = show print elements
26524 (gdb) set p elms 20
26526 Limit on string chars or array elements to print is 200.
26529 Note that if you are defining an alias of a @samp{set} command,
26530 and you want to have an alias for the corresponding @samp{show}
26531 command, then you need to define the latter separately.
26533 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26534 @var{ALIAS}, just as they are normally.
26537 (gdb) alias -a set pr elms = set p ele
26540 Finally, here is an example showing the creation of a one word
26541 alias for a more complex command.
26542 This creates alias @samp{spe} of the command @samp{set print elements}.
26545 (gdb) alias spe = set print elements
26550 @chapter Command Interpreters
26551 @cindex command interpreters
26553 @value{GDBN} supports multiple command interpreters, and some command
26554 infrastructure to allow users or user interface writers to switch
26555 between interpreters or run commands in other interpreters.
26557 @value{GDBN} currently supports two command interpreters, the console
26558 interpreter (sometimes called the command-line interpreter or @sc{cli})
26559 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26560 describes both of these interfaces in great detail.
26562 By default, @value{GDBN} will start with the console interpreter.
26563 However, the user may choose to start @value{GDBN} with another
26564 interpreter by specifying the @option{-i} or @option{--interpreter}
26565 startup options. Defined interpreters include:
26569 @cindex console interpreter
26570 The traditional console or command-line interpreter. This is the most often
26571 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26572 @value{GDBN} will use this interpreter.
26575 @cindex mi interpreter
26576 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26577 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26578 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26582 @cindex mi2 interpreter
26583 The current @sc{gdb/mi} interface.
26586 @cindex mi1 interpreter
26587 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26591 @cindex invoke another interpreter
26592 The interpreter being used by @value{GDBN} may not be dynamically
26593 switched at runtime. Although possible, this could lead to a very
26594 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26595 enters the command "interpreter-set console" in a console view,
26596 @value{GDBN} would switch to using the console interpreter, rendering
26597 the IDE inoperable!
26599 @kindex interpreter-exec
26600 Although you may only choose a single interpreter at startup, you may execute
26601 commands in any interpreter from the current interpreter using the appropriate
26602 command. If you are running the console interpreter, simply use the
26603 @code{interpreter-exec} command:
26606 interpreter-exec mi "-data-list-register-names"
26609 @sc{gdb/mi} has a similar command, although it is only available in versions of
26610 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26613 @chapter @value{GDBN} Text User Interface
26615 @cindex Text User Interface
26618 * TUI Overview:: TUI overview
26619 * TUI Keys:: TUI key bindings
26620 * TUI Single Key Mode:: TUI single key mode
26621 * TUI Commands:: TUI-specific commands
26622 * TUI Configuration:: TUI configuration variables
26625 The @value{GDBN} Text User Interface (TUI) is a terminal
26626 interface which uses the @code{curses} library to show the source
26627 file, the assembly output, the program registers and @value{GDBN}
26628 commands in separate text windows. The TUI mode is supported only
26629 on platforms where a suitable version of the @code{curses} library
26632 The TUI mode is enabled by default when you invoke @value{GDBN} as
26633 @samp{@value{GDBP} -tui}.
26634 You can also switch in and out of TUI mode while @value{GDBN} runs by
26635 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26636 @xref{TUI Keys, ,TUI Key Bindings}.
26639 @section TUI Overview
26641 In TUI mode, @value{GDBN} can display several text windows:
26645 This window is the @value{GDBN} command window with the @value{GDBN}
26646 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26647 managed using readline.
26650 The source window shows the source file of the program. The current
26651 line and active breakpoints are displayed in this window.
26654 The assembly window shows the disassembly output of the program.
26657 This window shows the processor registers. Registers are highlighted
26658 when their values change.
26661 The source and assembly windows show the current program position
26662 by highlighting the current line and marking it with a @samp{>} marker.
26663 Breakpoints are indicated with two markers. The first marker
26664 indicates the breakpoint type:
26668 Breakpoint which was hit at least once.
26671 Breakpoint which was never hit.
26674 Hardware breakpoint which was hit at least once.
26677 Hardware breakpoint which was never hit.
26680 The second marker indicates whether the breakpoint is enabled or not:
26684 Breakpoint is enabled.
26687 Breakpoint is disabled.
26690 The source, assembly and register windows are updated when the current
26691 thread changes, when the frame changes, or when the program counter
26694 These windows are not all visible at the same time. The command
26695 window is always visible. The others can be arranged in several
26706 source and assembly,
26709 source and registers, or
26712 assembly and registers.
26715 A status line above the command window shows the following information:
26719 Indicates the current @value{GDBN} target.
26720 (@pxref{Targets, ,Specifying a Debugging Target}).
26723 Gives the current process or thread number.
26724 When no process is being debugged, this field is set to @code{No process}.
26727 Gives the current function name for the selected frame.
26728 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26729 When there is no symbol corresponding to the current program counter,
26730 the string @code{??} is displayed.
26733 Indicates the current line number for the selected frame.
26734 When the current line number is not known, the string @code{??} is displayed.
26737 Indicates the current program counter address.
26741 @section TUI Key Bindings
26742 @cindex TUI key bindings
26744 The TUI installs several key bindings in the readline keymaps
26745 @ifset SYSTEM_READLINE
26746 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26748 @ifclear SYSTEM_READLINE
26749 (@pxref{Command Line Editing}).
26751 The following key bindings are installed for both TUI mode and the
26752 @value{GDBN} standard mode.
26761 Enter or leave the TUI mode. When leaving the TUI mode,
26762 the curses window management stops and @value{GDBN} operates using
26763 its standard mode, writing on the terminal directly. When reentering
26764 the TUI mode, control is given back to the curses windows.
26765 The screen is then refreshed.
26769 Use a TUI layout with only one window. The layout will
26770 either be @samp{source} or @samp{assembly}. When the TUI mode
26771 is not active, it will switch to the TUI mode.
26773 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26777 Use a TUI layout with at least two windows. When the current
26778 layout already has two windows, the next layout with two windows is used.
26779 When a new layout is chosen, one window will always be common to the
26780 previous layout and the new one.
26782 Think of it as the Emacs @kbd{C-x 2} binding.
26786 Change the active window. The TUI associates several key bindings
26787 (like scrolling and arrow keys) with the active window. This command
26788 gives the focus to the next TUI window.
26790 Think of it as the Emacs @kbd{C-x o} binding.
26794 Switch in and out of the TUI SingleKey mode that binds single
26795 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26798 The following key bindings only work in the TUI mode:
26803 Scroll the active window one page up.
26807 Scroll the active window one page down.
26811 Scroll the active window one line up.
26815 Scroll the active window one line down.
26819 Scroll the active window one column left.
26823 Scroll the active window one column right.
26827 Refresh the screen.
26830 Because the arrow keys scroll the active window in the TUI mode, they
26831 are not available for their normal use by readline unless the command
26832 window has the focus. When another window is active, you must use
26833 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
26834 and @kbd{C-f} to control the command window.
26836 @node TUI Single Key Mode
26837 @section TUI Single Key Mode
26838 @cindex TUI single key mode
26840 The TUI also provides a @dfn{SingleKey} mode, which binds several
26841 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
26842 switch into this mode, where the following key bindings are used:
26845 @kindex c @r{(SingleKey TUI key)}
26849 @kindex d @r{(SingleKey TUI key)}
26853 @kindex f @r{(SingleKey TUI key)}
26857 @kindex n @r{(SingleKey TUI key)}
26861 @kindex q @r{(SingleKey TUI key)}
26863 exit the SingleKey mode.
26865 @kindex r @r{(SingleKey TUI key)}
26869 @kindex s @r{(SingleKey TUI key)}
26873 @kindex u @r{(SingleKey TUI key)}
26877 @kindex v @r{(SingleKey TUI key)}
26881 @kindex w @r{(SingleKey TUI key)}
26886 Other keys temporarily switch to the @value{GDBN} command prompt.
26887 The key that was pressed is inserted in the editing buffer so that
26888 it is possible to type most @value{GDBN} commands without interaction
26889 with the TUI SingleKey mode. Once the command is entered the TUI
26890 SingleKey mode is restored. The only way to permanently leave
26891 this mode is by typing @kbd{q} or @kbd{C-x s}.
26895 @section TUI-specific Commands
26896 @cindex TUI commands
26898 The TUI has specific commands to control the text windows.
26899 These commands are always available, even when @value{GDBN} is not in
26900 the TUI mode. When @value{GDBN} is in the standard mode, most
26901 of these commands will automatically switch to the TUI mode.
26903 Note that if @value{GDBN}'s @code{stdout} is not connected to a
26904 terminal, or @value{GDBN} has been started with the machine interface
26905 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
26906 these commands will fail with an error, because it would not be
26907 possible or desirable to enable curses window management.
26912 List and give the size of all displayed windows.
26916 Display the next layout.
26919 Display the previous layout.
26922 Display the source window only.
26925 Display the assembly window only.
26928 Display the source and assembly window.
26931 Display the register window together with the source or assembly window.
26935 Make the next window active for scrolling.
26938 Make the previous window active for scrolling.
26941 Make the source window active for scrolling.
26944 Make the assembly window active for scrolling.
26947 Make the register window active for scrolling.
26950 Make the command window active for scrolling.
26954 Refresh the screen. This is similar to typing @kbd{C-L}.
26956 @item tui reg float
26958 Show the floating point registers in the register window.
26960 @item tui reg general
26961 Show the general registers in the register window.
26964 Show the next register group. The list of register groups as well as
26965 their order is target specific. The predefined register groups are the
26966 following: @code{general}, @code{float}, @code{system}, @code{vector},
26967 @code{all}, @code{save}, @code{restore}.
26969 @item tui reg system
26970 Show the system registers in the register window.
26974 Update the source window and the current execution point.
26976 @item winheight @var{name} +@var{count}
26977 @itemx winheight @var{name} -@var{count}
26979 Change the height of the window @var{name} by @var{count}
26980 lines. Positive counts increase the height, while negative counts
26983 @item tabset @var{nchars}
26985 Set the width of tab stops to be @var{nchars} characters.
26988 @node TUI Configuration
26989 @section TUI Configuration Variables
26990 @cindex TUI configuration variables
26992 Several configuration variables control the appearance of TUI windows.
26995 @item set tui border-kind @var{kind}
26996 @kindex set tui border-kind
26997 Select the border appearance for the source, assembly and register windows.
26998 The possible values are the following:
27001 Use a space character to draw the border.
27004 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27007 Use the Alternate Character Set to draw the border. The border is
27008 drawn using character line graphics if the terminal supports them.
27011 @item set tui border-mode @var{mode}
27012 @kindex set tui border-mode
27013 @itemx set tui active-border-mode @var{mode}
27014 @kindex set tui active-border-mode
27015 Select the display attributes for the borders of the inactive windows
27016 or the active window. The @var{mode} can be one of the following:
27019 Use normal attributes to display the border.
27025 Use reverse video mode.
27028 Use half bright mode.
27030 @item half-standout
27031 Use half bright and standout mode.
27034 Use extra bright or bold mode.
27036 @item bold-standout
27037 Use extra bright or bold and standout mode.
27042 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27045 @cindex @sc{gnu} Emacs
27046 A special interface allows you to use @sc{gnu} Emacs to view (and
27047 edit) the source files for the program you are debugging with
27050 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27051 executable file you want to debug as an argument. This command starts
27052 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27053 created Emacs buffer.
27054 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27056 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27061 All ``terminal'' input and output goes through an Emacs buffer, called
27064 This applies both to @value{GDBN} commands and their output, and to the input
27065 and output done by the program you are debugging.
27067 This is useful because it means that you can copy the text of previous
27068 commands and input them again; you can even use parts of the output
27071 All the facilities of Emacs' Shell mode are available for interacting
27072 with your program. In particular, you can send signals the usual
27073 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27077 @value{GDBN} displays source code through Emacs.
27079 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27080 source file for that frame and puts an arrow (@samp{=>}) at the
27081 left margin of the current line. Emacs uses a separate buffer for
27082 source display, and splits the screen to show both your @value{GDBN} session
27085 Explicit @value{GDBN} @code{list} or search commands still produce output as
27086 usual, but you probably have no reason to use them from Emacs.
27089 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27090 a graphical mode, enabled by default, which provides further buffers
27091 that can control the execution and describe the state of your program.
27092 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27094 If you specify an absolute file name when prompted for the @kbd{M-x
27095 gdb} argument, then Emacs sets your current working directory to where
27096 your program resides. If you only specify the file name, then Emacs
27097 sets your current working directory to the directory associated
27098 with the previous buffer. In this case, @value{GDBN} may find your
27099 program by searching your environment's @code{PATH} variable, but on
27100 some operating systems it might not find the source. So, although the
27101 @value{GDBN} input and output session proceeds normally, the auxiliary
27102 buffer does not display the current source and line of execution.
27104 The initial working directory of @value{GDBN} is printed on the top
27105 line of the GUD buffer and this serves as a default for the commands
27106 that specify files for @value{GDBN} to operate on. @xref{Files,
27107 ,Commands to Specify Files}.
27109 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27110 need to call @value{GDBN} by a different name (for example, if you
27111 keep several configurations around, with different names) you can
27112 customize the Emacs variable @code{gud-gdb-command-name} to run the
27115 In the GUD buffer, you can use these special Emacs commands in
27116 addition to the standard Shell mode commands:
27120 Describe the features of Emacs' GUD Mode.
27123 Execute to another source line, like the @value{GDBN} @code{step} command; also
27124 update the display window to show the current file and location.
27127 Execute to next source line in this function, skipping all function
27128 calls, like the @value{GDBN} @code{next} command. Then update the display window
27129 to show the current file and location.
27132 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27133 display window accordingly.
27136 Execute until exit from the selected stack frame, like the @value{GDBN}
27137 @code{finish} command.
27140 Continue execution of your program, like the @value{GDBN} @code{continue}
27144 Go up the number of frames indicated by the numeric argument
27145 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27146 like the @value{GDBN} @code{up} command.
27149 Go down the number of frames indicated by the numeric argument, like the
27150 @value{GDBN} @code{down} command.
27153 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27154 tells @value{GDBN} to set a breakpoint on the source line point is on.
27156 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27157 separate frame which shows a backtrace when the GUD buffer is current.
27158 Move point to any frame in the stack and type @key{RET} to make it
27159 become the current frame and display the associated source in the
27160 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27161 selected frame become the current one. In graphical mode, the
27162 speedbar displays watch expressions.
27164 If you accidentally delete the source-display buffer, an easy way to get
27165 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27166 request a frame display; when you run under Emacs, this recreates
27167 the source buffer if necessary to show you the context of the current
27170 The source files displayed in Emacs are in ordinary Emacs buffers
27171 which are visiting the source files in the usual way. You can edit
27172 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27173 communicates with Emacs in terms of line numbers. If you add or
27174 delete lines from the text, the line numbers that @value{GDBN} knows cease
27175 to correspond properly with the code.
27177 A more detailed description of Emacs' interaction with @value{GDBN} is
27178 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27182 @chapter The @sc{gdb/mi} Interface
27184 @unnumberedsec Function and Purpose
27186 @cindex @sc{gdb/mi}, its purpose
27187 @sc{gdb/mi} is a line based machine oriented text interface to
27188 @value{GDBN} and is activated by specifying using the
27189 @option{--interpreter} command line option (@pxref{Mode Options}). It
27190 is specifically intended to support the development of systems which
27191 use the debugger as just one small component of a larger system.
27193 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27194 in the form of a reference manual.
27196 Note that @sc{gdb/mi} is still under construction, so some of the
27197 features described below are incomplete and subject to change
27198 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27200 @unnumberedsec Notation and Terminology
27202 @cindex notational conventions, for @sc{gdb/mi}
27203 This chapter uses the following notation:
27207 @code{|} separates two alternatives.
27210 @code{[ @var{something} ]} indicates that @var{something} is optional:
27211 it may or may not be given.
27214 @code{( @var{group} )*} means that @var{group} inside the parentheses
27215 may repeat zero or more times.
27218 @code{( @var{group} )+} means that @var{group} inside the parentheses
27219 may repeat one or more times.
27222 @code{"@var{string}"} means a literal @var{string}.
27226 @heading Dependencies
27230 * GDB/MI General Design::
27231 * GDB/MI Command Syntax::
27232 * GDB/MI Compatibility with CLI::
27233 * GDB/MI Development and Front Ends::
27234 * GDB/MI Output Records::
27235 * GDB/MI Simple Examples::
27236 * GDB/MI Command Description Format::
27237 * GDB/MI Breakpoint Commands::
27238 * GDB/MI Catchpoint Commands::
27239 * GDB/MI Program Context::
27240 * GDB/MI Thread Commands::
27241 * GDB/MI Ada Tasking Commands::
27242 * GDB/MI Program Execution::
27243 * GDB/MI Stack Manipulation::
27244 * GDB/MI Variable Objects::
27245 * GDB/MI Data Manipulation::
27246 * GDB/MI Tracepoint Commands::
27247 * GDB/MI Symbol Query::
27248 * GDB/MI File Commands::
27250 * GDB/MI Kod Commands::
27251 * GDB/MI Memory Overlay Commands::
27252 * GDB/MI Signal Handling Commands::
27254 * GDB/MI Target Manipulation::
27255 * GDB/MI File Transfer Commands::
27256 * GDB/MI Miscellaneous Commands::
27259 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27260 @node GDB/MI General Design
27261 @section @sc{gdb/mi} General Design
27262 @cindex GDB/MI General Design
27264 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27265 parts---commands sent to @value{GDBN}, responses to those commands
27266 and notifications. Each command results in exactly one response,
27267 indicating either successful completion of the command, or an error.
27268 For the commands that do not resume the target, the response contains the
27269 requested information. For the commands that resume the target, the
27270 response only indicates whether the target was successfully resumed.
27271 Notifications is the mechanism for reporting changes in the state of the
27272 target, or in @value{GDBN} state, that cannot conveniently be associated with
27273 a command and reported as part of that command response.
27275 The important examples of notifications are:
27279 Exec notifications. These are used to report changes in
27280 target state---when a target is resumed, or stopped. It would not
27281 be feasible to include this information in response of resuming
27282 commands, because one resume commands can result in multiple events in
27283 different threads. Also, quite some time may pass before any event
27284 happens in the target, while a frontend needs to know whether the resuming
27285 command itself was successfully executed.
27288 Console output, and status notifications. Console output
27289 notifications are used to report output of CLI commands, as well as
27290 diagnostics for other commands. Status notifications are used to
27291 report the progress of a long-running operation. Naturally, including
27292 this information in command response would mean no output is produced
27293 until the command is finished, which is undesirable.
27296 General notifications. Commands may have various side effects on
27297 the @value{GDBN} or target state beyond their official purpose. For example,
27298 a command may change the selected thread. Although such changes can
27299 be included in command response, using notification allows for more
27300 orthogonal frontend design.
27304 There's no guarantee that whenever an MI command reports an error,
27305 @value{GDBN} or the target are in any specific state, and especially,
27306 the state is not reverted to the state before the MI command was
27307 processed. Therefore, whenever an MI command results in an error,
27308 we recommend that the frontend refreshes all the information shown in
27309 the user interface.
27313 * Context management::
27314 * Asynchronous and non-stop modes::
27318 @node Context management
27319 @subsection Context management
27321 In most cases when @value{GDBN} accesses the target, this access is
27322 done in context of a specific thread and frame (@pxref{Frames}).
27323 Often, even when accessing global data, the target requires that a thread
27324 be specified. The CLI interface maintains the selected thread and frame,
27325 and supplies them to target on each command. This is convenient,
27326 because a command line user would not want to specify that information
27327 explicitly on each command, and because user interacts with
27328 @value{GDBN} via a single terminal, so no confusion is possible as
27329 to what thread and frame are the current ones.
27331 In the case of MI, the concept of selected thread and frame is less
27332 useful. First, a frontend can easily remember this information
27333 itself. Second, a graphical frontend can have more than one window,
27334 each one used for debugging a different thread, and the frontend might
27335 want to access additional threads for internal purposes. This
27336 increases the risk that by relying on implicitly selected thread, the
27337 frontend may be operating on a wrong one. Therefore, each MI command
27338 should explicitly specify which thread and frame to operate on. To
27339 make it possible, each MI command accepts the @samp{--thread} and
27340 @samp{--frame} options, the value to each is @value{GDBN} identifier
27341 for thread and frame to operate on.
27343 Usually, each top-level window in a frontend allows the user to select
27344 a thread and a frame, and remembers the user selection for further
27345 operations. However, in some cases @value{GDBN} may suggest that the
27346 current thread be changed. For example, when stopping on a breakpoint
27347 it is reasonable to switch to the thread where breakpoint is hit. For
27348 another example, if the user issues the CLI @samp{thread} command via
27349 the frontend, it is desirable to change the frontend's selected thread to the
27350 one specified by user. @value{GDBN} communicates the suggestion to
27351 change current thread using the @samp{=thread-selected} notification.
27352 No such notification is available for the selected frame at the moment.
27354 Note that historically, MI shares the selected thread with CLI, so
27355 frontends used the @code{-thread-select} to execute commands in the
27356 right context. However, getting this to work right is cumbersome. The
27357 simplest way is for frontend to emit @code{-thread-select} command
27358 before every command. This doubles the number of commands that need
27359 to be sent. The alternative approach is to suppress @code{-thread-select}
27360 if the selected thread in @value{GDBN} is supposed to be identical to the
27361 thread the frontend wants to operate on. However, getting this
27362 optimization right can be tricky. In particular, if the frontend
27363 sends several commands to @value{GDBN}, and one of the commands changes the
27364 selected thread, then the behaviour of subsequent commands will
27365 change. So, a frontend should either wait for response from such
27366 problematic commands, or explicitly add @code{-thread-select} for
27367 all subsequent commands. No frontend is known to do this exactly
27368 right, so it is suggested to just always pass the @samp{--thread} and
27369 @samp{--frame} options.
27371 @node Asynchronous and non-stop modes
27372 @subsection Asynchronous command execution and non-stop mode
27374 On some targets, @value{GDBN} is capable of processing MI commands
27375 even while the target is running. This is called @dfn{asynchronous
27376 command execution} (@pxref{Background Execution}). The frontend may
27377 specify a preferrence for asynchronous execution using the
27378 @code{-gdb-set target-async 1} command, which should be emitted before
27379 either running the executable or attaching to the target. After the
27380 frontend has started the executable or attached to the target, it can
27381 find if asynchronous execution is enabled using the
27382 @code{-list-target-features} command.
27384 Even if @value{GDBN} can accept a command while target is running,
27385 many commands that access the target do not work when the target is
27386 running. Therefore, asynchronous command execution is most useful
27387 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27388 it is possible to examine the state of one thread, while other threads
27391 When a given thread is running, MI commands that try to access the
27392 target in the context of that thread may not work, or may work only on
27393 some targets. In particular, commands that try to operate on thread's
27394 stack will not work, on any target. Commands that read memory, or
27395 modify breakpoints, may work or not work, depending on the target. Note
27396 that even commands that operate on global state, such as @code{print},
27397 @code{set}, and breakpoint commands, still access the target in the
27398 context of a specific thread, so frontend should try to find a
27399 stopped thread and perform the operation on that thread (using the
27400 @samp{--thread} option).
27402 Which commands will work in the context of a running thread is
27403 highly target dependent. However, the two commands
27404 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27405 to find the state of a thread, will always work.
27407 @node Thread groups
27408 @subsection Thread groups
27409 @value{GDBN} may be used to debug several processes at the same time.
27410 On some platfroms, @value{GDBN} may support debugging of several
27411 hardware systems, each one having several cores with several different
27412 processes running on each core. This section describes the MI
27413 mechanism to support such debugging scenarios.
27415 The key observation is that regardless of the structure of the
27416 target, MI can have a global list of threads, because most commands that
27417 accept the @samp{--thread} option do not need to know what process that
27418 thread belongs to. Therefore, it is not necessary to introduce
27419 neither additional @samp{--process} option, nor an notion of the
27420 current process in the MI interface. The only strictly new feature
27421 that is required is the ability to find how the threads are grouped
27424 To allow the user to discover such grouping, and to support arbitrary
27425 hierarchy of machines/cores/processes, MI introduces the concept of a
27426 @dfn{thread group}. Thread group is a collection of threads and other
27427 thread groups. A thread group always has a string identifier, a type,
27428 and may have additional attributes specific to the type. A new
27429 command, @code{-list-thread-groups}, returns the list of top-level
27430 thread groups, which correspond to processes that @value{GDBN} is
27431 debugging at the moment. By passing an identifier of a thread group
27432 to the @code{-list-thread-groups} command, it is possible to obtain
27433 the members of specific thread group.
27435 To allow the user to easily discover processes, and other objects, he
27436 wishes to debug, a concept of @dfn{available thread group} is
27437 introduced. Available thread group is an thread group that
27438 @value{GDBN} is not debugging, but that can be attached to, using the
27439 @code{-target-attach} command. The list of available top-level thread
27440 groups can be obtained using @samp{-list-thread-groups --available}.
27441 In general, the content of a thread group may be only retrieved only
27442 after attaching to that thread group.
27444 Thread groups are related to inferiors (@pxref{Inferiors and
27445 Programs}). Each inferior corresponds to a thread group of a special
27446 type @samp{process}, and some additional operations are permitted on
27447 such thread groups.
27449 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27450 @node GDB/MI Command Syntax
27451 @section @sc{gdb/mi} Command Syntax
27454 * GDB/MI Input Syntax::
27455 * GDB/MI Output Syntax::
27458 @node GDB/MI Input Syntax
27459 @subsection @sc{gdb/mi} Input Syntax
27461 @cindex input syntax for @sc{gdb/mi}
27462 @cindex @sc{gdb/mi}, input syntax
27464 @item @var{command} @expansion{}
27465 @code{@var{cli-command} | @var{mi-command}}
27467 @item @var{cli-command} @expansion{}
27468 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27469 @var{cli-command} is any existing @value{GDBN} CLI command.
27471 @item @var{mi-command} @expansion{}
27472 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27473 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27475 @item @var{token} @expansion{}
27476 "any sequence of digits"
27478 @item @var{option} @expansion{}
27479 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27481 @item @var{parameter} @expansion{}
27482 @code{@var{non-blank-sequence} | @var{c-string}}
27484 @item @var{operation} @expansion{}
27485 @emph{any of the operations described in this chapter}
27487 @item @var{non-blank-sequence} @expansion{}
27488 @emph{anything, provided it doesn't contain special characters such as
27489 "-", @var{nl}, """ and of course " "}
27491 @item @var{c-string} @expansion{}
27492 @code{""" @var{seven-bit-iso-c-string-content} """}
27494 @item @var{nl} @expansion{}
27503 The CLI commands are still handled by the @sc{mi} interpreter; their
27504 output is described below.
27507 The @code{@var{token}}, when present, is passed back when the command
27511 Some @sc{mi} commands accept optional arguments as part of the parameter
27512 list. Each option is identified by a leading @samp{-} (dash) and may be
27513 followed by an optional argument parameter. Options occur first in the
27514 parameter list and can be delimited from normal parameters using
27515 @samp{--} (this is useful when some parameters begin with a dash).
27522 We want easy access to the existing CLI syntax (for debugging).
27525 We want it to be easy to spot a @sc{mi} operation.
27528 @node GDB/MI Output Syntax
27529 @subsection @sc{gdb/mi} Output Syntax
27531 @cindex output syntax of @sc{gdb/mi}
27532 @cindex @sc{gdb/mi}, output syntax
27533 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27534 followed, optionally, by a single result record. This result record
27535 is for the most recent command. The sequence of output records is
27536 terminated by @samp{(gdb)}.
27538 If an input command was prefixed with a @code{@var{token}} then the
27539 corresponding output for that command will also be prefixed by that same
27543 @item @var{output} @expansion{}
27544 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27546 @item @var{result-record} @expansion{}
27547 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27549 @item @var{out-of-band-record} @expansion{}
27550 @code{@var{async-record} | @var{stream-record}}
27552 @item @var{async-record} @expansion{}
27553 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27555 @item @var{exec-async-output} @expansion{}
27556 @code{[ @var{token} ] "*" @var{async-output}}
27558 @item @var{status-async-output} @expansion{}
27559 @code{[ @var{token} ] "+" @var{async-output}}
27561 @item @var{notify-async-output} @expansion{}
27562 @code{[ @var{token} ] "=" @var{async-output}}
27564 @item @var{async-output} @expansion{}
27565 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27567 @item @var{result-class} @expansion{}
27568 @code{"done" | "running" | "connected" | "error" | "exit"}
27570 @item @var{async-class} @expansion{}
27571 @code{"stopped" | @var{others}} (where @var{others} will be added
27572 depending on the needs---this is still in development).
27574 @item @var{result} @expansion{}
27575 @code{ @var{variable} "=" @var{value}}
27577 @item @var{variable} @expansion{}
27578 @code{ @var{string} }
27580 @item @var{value} @expansion{}
27581 @code{ @var{const} | @var{tuple} | @var{list} }
27583 @item @var{const} @expansion{}
27584 @code{@var{c-string}}
27586 @item @var{tuple} @expansion{}
27587 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27589 @item @var{list} @expansion{}
27590 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27591 @var{result} ( "," @var{result} )* "]" }
27593 @item @var{stream-record} @expansion{}
27594 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27596 @item @var{console-stream-output} @expansion{}
27597 @code{"~" @var{c-string}}
27599 @item @var{target-stream-output} @expansion{}
27600 @code{"@@" @var{c-string}}
27602 @item @var{log-stream-output} @expansion{}
27603 @code{"&" @var{c-string}}
27605 @item @var{nl} @expansion{}
27608 @item @var{token} @expansion{}
27609 @emph{any sequence of digits}.
27617 All output sequences end in a single line containing a period.
27620 The @code{@var{token}} is from the corresponding request. Note that
27621 for all async output, while the token is allowed by the grammar and
27622 may be output by future versions of @value{GDBN} for select async
27623 output messages, it is generally omitted. Frontends should treat
27624 all async output as reporting general changes in the state of the
27625 target and there should be no need to associate async output to any
27629 @cindex status output in @sc{gdb/mi}
27630 @var{status-async-output} contains on-going status information about the
27631 progress of a slow operation. It can be discarded. All status output is
27632 prefixed by @samp{+}.
27635 @cindex async output in @sc{gdb/mi}
27636 @var{exec-async-output} contains asynchronous state change on the target
27637 (stopped, started, disappeared). All async output is prefixed by
27641 @cindex notify output in @sc{gdb/mi}
27642 @var{notify-async-output} contains supplementary information that the
27643 client should handle (e.g., a new breakpoint information). All notify
27644 output is prefixed by @samp{=}.
27647 @cindex console output in @sc{gdb/mi}
27648 @var{console-stream-output} is output that should be displayed as is in the
27649 console. It is the textual response to a CLI command. All the console
27650 output is prefixed by @samp{~}.
27653 @cindex target output in @sc{gdb/mi}
27654 @var{target-stream-output} is the output produced by the target program.
27655 All the target output is prefixed by @samp{@@}.
27658 @cindex log output in @sc{gdb/mi}
27659 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27660 instance messages that should be displayed as part of an error log. All
27661 the log output is prefixed by @samp{&}.
27664 @cindex list output in @sc{gdb/mi}
27665 New @sc{gdb/mi} commands should only output @var{lists} containing
27671 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27672 details about the various output records.
27674 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27675 @node GDB/MI Compatibility with CLI
27676 @section @sc{gdb/mi} Compatibility with CLI
27678 @cindex compatibility, @sc{gdb/mi} and CLI
27679 @cindex @sc{gdb/mi}, compatibility with CLI
27681 For the developers convenience CLI commands can be entered directly,
27682 but there may be some unexpected behaviour. For example, commands
27683 that query the user will behave as if the user replied yes, breakpoint
27684 command lists are not executed and some CLI commands, such as
27685 @code{if}, @code{when} and @code{define}, prompt for further input with
27686 @samp{>}, which is not valid MI output.
27688 This feature may be removed at some stage in the future and it is
27689 recommended that front ends use the @code{-interpreter-exec} command
27690 (@pxref{-interpreter-exec}).
27692 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27693 @node GDB/MI Development and Front Ends
27694 @section @sc{gdb/mi} Development and Front Ends
27695 @cindex @sc{gdb/mi} development
27697 The application which takes the MI output and presents the state of the
27698 program being debugged to the user is called a @dfn{front end}.
27700 Although @sc{gdb/mi} is still incomplete, it is currently being used
27701 by a variety of front ends to @value{GDBN}. This makes it difficult
27702 to introduce new functionality without breaking existing usage. This
27703 section tries to minimize the problems by describing how the protocol
27706 Some changes in MI need not break a carefully designed front end, and
27707 for these the MI version will remain unchanged. The following is a
27708 list of changes that may occur within one level, so front ends should
27709 parse MI output in a way that can handle them:
27713 New MI commands may be added.
27716 New fields may be added to the output of any MI command.
27719 The range of values for fields with specified values, e.g.,
27720 @code{in_scope} (@pxref{-var-update}) may be extended.
27722 @c The format of field's content e.g type prefix, may change so parse it
27723 @c at your own risk. Yes, in general?
27725 @c The order of fields may change? Shouldn't really matter but it might
27726 @c resolve inconsistencies.
27729 If the changes are likely to break front ends, the MI version level
27730 will be increased by one. This will allow the front end to parse the
27731 output according to the MI version. Apart from mi0, new versions of
27732 @value{GDBN} will not support old versions of MI and it will be the
27733 responsibility of the front end to work with the new one.
27735 @c Starting with mi3, add a new command -mi-version that prints the MI
27738 The best way to avoid unexpected changes in MI that might break your front
27739 end is to make your project known to @value{GDBN} developers and
27740 follow development on @email{gdb@@sourceware.org} and
27741 @email{gdb-patches@@sourceware.org}.
27742 @cindex mailing lists
27744 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27745 @node GDB/MI Output Records
27746 @section @sc{gdb/mi} Output Records
27749 * GDB/MI Result Records::
27750 * GDB/MI Stream Records::
27751 * GDB/MI Async Records::
27752 * GDB/MI Breakpoint Information::
27753 * GDB/MI Frame Information::
27754 * GDB/MI Thread Information::
27755 * GDB/MI Ada Exception Information::
27758 @node GDB/MI Result Records
27759 @subsection @sc{gdb/mi} Result Records
27761 @cindex result records in @sc{gdb/mi}
27762 @cindex @sc{gdb/mi}, result records
27763 In addition to a number of out-of-band notifications, the response to a
27764 @sc{gdb/mi} command includes one of the following result indications:
27768 @item "^done" [ "," @var{results} ]
27769 The synchronous operation was successful, @code{@var{results}} are the return
27774 This result record is equivalent to @samp{^done}. Historically, it
27775 was output instead of @samp{^done} if the command has resumed the
27776 target. This behaviour is maintained for backward compatibility, but
27777 all frontends should treat @samp{^done} and @samp{^running}
27778 identically and rely on the @samp{*running} output record to determine
27779 which threads are resumed.
27783 @value{GDBN} has connected to a remote target.
27785 @item "^error" "," @var{c-string}
27787 The operation failed. The @code{@var{c-string}} contains the corresponding
27792 @value{GDBN} has terminated.
27796 @node GDB/MI Stream Records
27797 @subsection @sc{gdb/mi} Stream Records
27799 @cindex @sc{gdb/mi}, stream records
27800 @cindex stream records in @sc{gdb/mi}
27801 @value{GDBN} internally maintains a number of output streams: the console, the
27802 target, and the log. The output intended for each of these streams is
27803 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27805 Each stream record begins with a unique @dfn{prefix character} which
27806 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27807 Syntax}). In addition to the prefix, each stream record contains a
27808 @code{@var{string-output}}. This is either raw text (with an implicit new
27809 line) or a quoted C string (which does not contain an implicit newline).
27812 @item "~" @var{string-output}
27813 The console output stream contains text that should be displayed in the
27814 CLI console window. It contains the textual responses to CLI commands.
27816 @item "@@" @var{string-output}
27817 The target output stream contains any textual output from the running
27818 target. This is only present when GDB's event loop is truly
27819 asynchronous, which is currently only the case for remote targets.
27821 @item "&" @var{string-output}
27822 The log stream contains debugging messages being produced by @value{GDBN}'s
27826 @node GDB/MI Async Records
27827 @subsection @sc{gdb/mi} Async Records
27829 @cindex async records in @sc{gdb/mi}
27830 @cindex @sc{gdb/mi}, async records
27831 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27832 additional changes that have occurred. Those changes can either be a
27833 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
27834 target activity (e.g., target stopped).
27836 The following is the list of possible async records:
27840 @item *running,thread-id="@var{thread}"
27841 The target is now running. The @var{thread} field tells which
27842 specific thread is now running, and can be @samp{all} if all threads
27843 are running. The frontend should assume that no interaction with a
27844 running thread is possible after this notification is produced.
27845 The frontend should not assume that this notification is output
27846 only once for any command. @value{GDBN} may emit this notification
27847 several times, either for different threads, because it cannot resume
27848 all threads together, or even for a single thread, if the thread must
27849 be stepped though some code before letting it run freely.
27851 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
27852 The target has stopped. The @var{reason} field can have one of the
27856 @item breakpoint-hit
27857 A breakpoint was reached.
27858 @item watchpoint-trigger
27859 A watchpoint was triggered.
27860 @item read-watchpoint-trigger
27861 A read watchpoint was triggered.
27862 @item access-watchpoint-trigger
27863 An access watchpoint was triggered.
27864 @item function-finished
27865 An -exec-finish or similar CLI command was accomplished.
27866 @item location-reached
27867 An -exec-until or similar CLI command was accomplished.
27868 @item watchpoint-scope
27869 A watchpoint has gone out of scope.
27870 @item end-stepping-range
27871 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
27872 similar CLI command was accomplished.
27873 @item exited-signalled
27874 The inferior exited because of a signal.
27876 The inferior exited.
27877 @item exited-normally
27878 The inferior exited normally.
27879 @item signal-received
27880 A signal was received by the inferior.
27882 The inferior has stopped due to a library being loaded or unloaded.
27883 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
27884 set or when a @code{catch load} or @code{catch unload} catchpoint is
27885 in use (@pxref{Set Catchpoints}).
27887 The inferior has forked. This is reported when @code{catch fork}
27888 (@pxref{Set Catchpoints}) has been used.
27890 The inferior has vforked. This is reported in when @code{catch vfork}
27891 (@pxref{Set Catchpoints}) has been used.
27892 @item syscall-entry
27893 The inferior entered a system call. This is reported when @code{catch
27894 syscall} (@pxref{Set Catchpoints}) has been used.
27895 @item syscall-entry
27896 The inferior returned from a system call. This is reported when
27897 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
27899 The inferior called @code{exec}. This is reported when @code{catch exec}
27900 (@pxref{Set Catchpoints}) has been used.
27903 The @var{id} field identifies the thread that directly caused the stop
27904 -- for example by hitting a breakpoint. Depending on whether all-stop
27905 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
27906 stop all threads, or only the thread that directly triggered the stop.
27907 If all threads are stopped, the @var{stopped} field will have the
27908 value of @code{"all"}. Otherwise, the value of the @var{stopped}
27909 field will be a list of thread identifiers. Presently, this list will
27910 always include a single thread, but frontend should be prepared to see
27911 several threads in the list. The @var{core} field reports the
27912 processor core on which the stop event has happened. This field may be absent
27913 if such information is not available.
27915 @item =thread-group-added,id="@var{id}"
27916 @itemx =thread-group-removed,id="@var{id}"
27917 A thread group was either added or removed. The @var{id} field
27918 contains the @value{GDBN} identifier of the thread group. When a thread
27919 group is added, it generally might not be associated with a running
27920 process. When a thread group is removed, its id becomes invalid and
27921 cannot be used in any way.
27923 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
27924 A thread group became associated with a running program,
27925 either because the program was just started or the thread group
27926 was attached to a program. The @var{id} field contains the
27927 @value{GDBN} identifier of the thread group. The @var{pid} field
27928 contains process identifier, specific to the operating system.
27930 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
27931 A thread group is no longer associated with a running program,
27932 either because the program has exited, or because it was detached
27933 from. The @var{id} field contains the @value{GDBN} identifier of the
27934 thread group. @var{code} is the exit code of the inferior; it exists
27935 only when the inferior exited with some code.
27937 @item =thread-created,id="@var{id}",group-id="@var{gid}"
27938 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
27939 A thread either was created, or has exited. The @var{id} field
27940 contains the @value{GDBN} identifier of the thread. The @var{gid}
27941 field identifies the thread group this thread belongs to.
27943 @item =thread-selected,id="@var{id}"
27944 Informs that the selected thread was changed as result of the last
27945 command. This notification is not emitted as result of @code{-thread-select}
27946 command but is emitted whenever an MI command that is not documented
27947 to change the selected thread actually changes it. In particular,
27948 invoking, directly or indirectly (via user-defined command), the CLI
27949 @code{thread} command, will generate this notification.
27951 We suggest that in response to this notification, front ends
27952 highlight the selected thread and cause subsequent commands to apply to
27955 @item =library-loaded,...
27956 Reports that a new library file was loaded by the program. This
27957 notification has 4 fields---@var{id}, @var{target-name},
27958 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
27959 opaque identifier of the library. For remote debugging case,
27960 @var{target-name} and @var{host-name} fields give the name of the
27961 library file on the target, and on the host respectively. For native
27962 debugging, both those fields have the same value. The
27963 @var{symbols-loaded} field is emitted only for backward compatibility
27964 and should not be relied on to convey any useful information. The
27965 @var{thread-group} field, if present, specifies the id of the thread
27966 group in whose context the library was loaded. If the field is
27967 absent, it means the library was loaded in the context of all present
27970 @item =library-unloaded,...
27971 Reports that a library was unloaded by the program. This notification
27972 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
27973 the same meaning as for the @code{=library-loaded} notification.
27974 The @var{thread-group} field, if present, specifies the id of the
27975 thread group in whose context the library was unloaded. If the field is
27976 absent, it means the library was unloaded in the context of all present
27979 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
27980 @itemx =traceframe-changed,end
27981 Reports that the trace frame was changed and its new number is
27982 @var{tfnum}. The number of the tracepoint associated with this trace
27983 frame is @var{tpnum}.
27985 @item =tsv-created,name=@var{name},initial=@var{initial}
27986 Reports that the new trace state variable @var{name} is created with
27987 initial value @var{initial}.
27989 @item =tsv-deleted,name=@var{name}
27990 @itemx =tsv-deleted
27991 Reports that the trace state variable @var{name} is deleted or all
27992 trace state variables are deleted.
27994 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
27995 Reports that the trace state variable @var{name} is modified with
27996 the initial value @var{initial}. The current value @var{current} of
27997 trace state variable is optional and is reported if the current
27998 value of trace state variable is known.
28000 @item =breakpoint-created,bkpt=@{...@}
28001 @itemx =breakpoint-modified,bkpt=@{...@}
28002 @itemx =breakpoint-deleted,id=@var{number}
28003 Reports that a breakpoint was created, modified, or deleted,
28004 respectively. Only user-visible breakpoints are reported to the MI
28007 The @var{bkpt} argument is of the same form as returned by the various
28008 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28009 @var{number} is the ordinal number of the breakpoint.
28011 Note that if a breakpoint is emitted in the result record of a
28012 command, then it will not also be emitted in an async record.
28014 @item =record-started,thread-group="@var{id}"
28015 @itemx =record-stopped,thread-group="@var{id}"
28016 Execution log recording was either started or stopped on an
28017 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28018 group corresponding to the affected inferior.
28020 @item =cmd-param-changed,param=@var{param},value=@var{value}
28021 Reports that a parameter of the command @code{set @var{param}} is
28022 changed to @var{value}. In the multi-word @code{set} command,
28023 the @var{param} is the whole parameter list to @code{set} command.
28024 For example, In command @code{set check type on}, @var{param}
28025 is @code{check type} and @var{value} is @code{on}.
28027 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28028 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28029 written in an inferior. The @var{id} is the identifier of the
28030 thread group corresponding to the affected inferior. The optional
28031 @code{type="code"} part is reported if the memory written to holds
28035 @node GDB/MI Breakpoint Information
28036 @subsection @sc{gdb/mi} Breakpoint Information
28038 When @value{GDBN} reports information about a breakpoint, a
28039 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28044 The breakpoint number. For a breakpoint that represents one location
28045 of a multi-location breakpoint, this will be a dotted pair, like
28049 The type of the breakpoint. For ordinary breakpoints this will be
28050 @samp{breakpoint}, but many values are possible.
28053 If the type of the breakpoint is @samp{catchpoint}, then this
28054 indicates the exact type of catchpoint.
28057 This is the breakpoint disposition---either @samp{del}, meaning that
28058 the breakpoint will be deleted at the next stop, or @samp{keep},
28059 meaning that the breakpoint will not be deleted.
28062 This indicates whether the breakpoint is enabled, in which case the
28063 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28064 Note that this is not the same as the field @code{enable}.
28067 The address of the breakpoint. This may be a hexidecimal number,
28068 giving the address; or the string @samp{<PENDING>}, for a pending
28069 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28070 multiple locations. This field will not be present if no address can
28071 be determined. For example, a watchpoint does not have an address.
28074 If known, the function in which the breakpoint appears.
28075 If not known, this field is not present.
28078 The name of the source file which contains this function, if known.
28079 If not known, this field is not present.
28082 The full file name of the source file which contains this function, if
28083 known. If not known, this field is not present.
28086 The line number at which this breakpoint appears, if known.
28087 If not known, this field is not present.
28090 If the source file is not known, this field may be provided. If
28091 provided, this holds the address of the breakpoint, possibly followed
28095 If this breakpoint is pending, this field is present and holds the
28096 text used to set the breakpoint, as entered by the user.
28099 Where this breakpoint's condition is evaluated, either @samp{host} or
28103 If this is a thread-specific breakpoint, then this identifies the
28104 thread in which the breakpoint can trigger.
28107 If this breakpoint is restricted to a particular Ada task, then this
28108 field will hold the task identifier.
28111 If the breakpoint is conditional, this is the condition expression.
28114 The ignore count of the breakpoint.
28117 The enable count of the breakpoint.
28119 @item traceframe-usage
28122 @item static-tracepoint-marker-string-id
28123 For a static tracepoint, the name of the static tracepoint marker.
28126 For a masked watchpoint, this is the mask.
28129 A tracepoint's pass count.
28131 @item original-location
28132 The location of the breakpoint as originally specified by the user.
28133 This field is optional.
28136 The number of times the breakpoint has been hit.
28139 This field is only given for tracepoints. This is either @samp{y},
28140 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28144 Some extra data, the exact contents of which are type-dependent.
28148 For example, here is what the output of @code{-break-insert}
28149 (@pxref{GDB/MI Breakpoint Commands}) might be:
28152 -> -break-insert main
28153 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28154 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28155 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28160 @node GDB/MI Frame Information
28161 @subsection @sc{gdb/mi} Frame Information
28163 Response from many MI commands includes an information about stack
28164 frame. This information is a tuple that may have the following
28169 The level of the stack frame. The innermost frame has the level of
28170 zero. This field is always present.
28173 The name of the function corresponding to the frame. This field may
28174 be absent if @value{GDBN} is unable to determine the function name.
28177 The code address for the frame. This field is always present.
28180 The name of the source files that correspond to the frame's code
28181 address. This field may be absent.
28184 The source line corresponding to the frames' code address. This field
28188 The name of the binary file (either executable or shared library) the
28189 corresponds to the frame's code address. This field may be absent.
28193 @node GDB/MI Thread Information
28194 @subsection @sc{gdb/mi} Thread Information
28196 Whenever @value{GDBN} has to report an information about a thread, it
28197 uses a tuple with the following fields:
28201 The numeric id assigned to the thread by @value{GDBN}. This field is
28205 Target-specific string identifying the thread. This field is always present.
28208 Additional information about the thread provided by the target.
28209 It is supposed to be human-readable and not interpreted by the
28210 frontend. This field is optional.
28213 Either @samp{stopped} or @samp{running}, depending on whether the
28214 thread is presently running. This field is always present.
28217 The value of this field is an integer number of the processor core the
28218 thread was last seen on. This field is optional.
28221 @node GDB/MI Ada Exception Information
28222 @subsection @sc{gdb/mi} Ada Exception Information
28224 Whenever a @code{*stopped} record is emitted because the program
28225 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28226 @value{GDBN} provides the name of the exception that was raised via
28227 the @code{exception-name} field.
28229 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28230 @node GDB/MI Simple Examples
28231 @section Simple Examples of @sc{gdb/mi} Interaction
28232 @cindex @sc{gdb/mi}, simple examples
28234 This subsection presents several simple examples of interaction using
28235 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28236 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28237 the output received from @sc{gdb/mi}.
28239 Note the line breaks shown in the examples are here only for
28240 readability, they don't appear in the real output.
28242 @subheading Setting a Breakpoint
28244 Setting a breakpoint generates synchronous output which contains detailed
28245 information of the breakpoint.
28248 -> -break-insert main
28249 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28250 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28251 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28256 @subheading Program Execution
28258 Program execution generates asynchronous records and MI gives the
28259 reason that execution stopped.
28265 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28266 frame=@{addr="0x08048564",func="main",
28267 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28268 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28273 <- *stopped,reason="exited-normally"
28277 @subheading Quitting @value{GDBN}
28279 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28287 Please note that @samp{^exit} is printed immediately, but it might
28288 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28289 performs necessary cleanups, including killing programs being debugged
28290 or disconnecting from debug hardware, so the frontend should wait till
28291 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28292 fails to exit in reasonable time.
28294 @subheading A Bad Command
28296 Here's what happens if you pass a non-existent command:
28300 <- ^error,msg="Undefined MI command: rubbish"
28305 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28306 @node GDB/MI Command Description Format
28307 @section @sc{gdb/mi} Command Description Format
28309 The remaining sections describe blocks of commands. Each block of
28310 commands is laid out in a fashion similar to this section.
28312 @subheading Motivation
28314 The motivation for this collection of commands.
28316 @subheading Introduction
28318 A brief introduction to this collection of commands as a whole.
28320 @subheading Commands
28322 For each command in the block, the following is described:
28324 @subsubheading Synopsis
28327 -command @var{args}@dots{}
28330 @subsubheading Result
28332 @subsubheading @value{GDBN} Command
28334 The corresponding @value{GDBN} CLI command(s), if any.
28336 @subsubheading Example
28338 Example(s) formatted for readability. Some of the described commands have
28339 not been implemented yet and these are labeled N.A.@: (not available).
28342 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28343 @node GDB/MI Breakpoint Commands
28344 @section @sc{gdb/mi} Breakpoint Commands
28346 @cindex breakpoint commands for @sc{gdb/mi}
28347 @cindex @sc{gdb/mi}, breakpoint commands
28348 This section documents @sc{gdb/mi} commands for manipulating
28351 @subheading The @code{-break-after} Command
28352 @findex -break-after
28354 @subsubheading Synopsis
28357 -break-after @var{number} @var{count}
28360 The breakpoint number @var{number} is not in effect until it has been
28361 hit @var{count} times. To see how this is reflected in the output of
28362 the @samp{-break-list} command, see the description of the
28363 @samp{-break-list} command below.
28365 @subsubheading @value{GDBN} Command
28367 The corresponding @value{GDBN} command is @samp{ignore}.
28369 @subsubheading Example
28374 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28375 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28376 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28384 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28385 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28386 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28387 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28388 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28389 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28390 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28391 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28392 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28393 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28398 @subheading The @code{-break-catch} Command
28399 @findex -break-catch
28402 @subheading The @code{-break-commands} Command
28403 @findex -break-commands
28405 @subsubheading Synopsis
28408 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28411 Specifies the CLI commands that should be executed when breakpoint
28412 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28413 are the commands. If no command is specified, any previously-set
28414 commands are cleared. @xref{Break Commands}. Typical use of this
28415 functionality is tracing a program, that is, printing of values of
28416 some variables whenever breakpoint is hit and then continuing.
28418 @subsubheading @value{GDBN} Command
28420 The corresponding @value{GDBN} command is @samp{commands}.
28422 @subsubheading Example
28427 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28428 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28429 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28432 -break-commands 1 "print v" "continue"
28437 @subheading The @code{-break-condition} Command
28438 @findex -break-condition
28440 @subsubheading Synopsis
28443 -break-condition @var{number} @var{expr}
28446 Breakpoint @var{number} will stop the program only if the condition in
28447 @var{expr} is true. The condition becomes part of the
28448 @samp{-break-list} output (see the description of the @samp{-break-list}
28451 @subsubheading @value{GDBN} Command
28453 The corresponding @value{GDBN} command is @samp{condition}.
28455 @subsubheading Example
28459 -break-condition 1 1
28463 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28464 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28465 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28466 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28467 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28468 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28469 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28470 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28471 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28472 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28476 @subheading The @code{-break-delete} Command
28477 @findex -break-delete
28479 @subsubheading Synopsis
28482 -break-delete ( @var{breakpoint} )+
28485 Delete the breakpoint(s) whose number(s) are specified in the argument
28486 list. This is obviously reflected in the breakpoint list.
28488 @subsubheading @value{GDBN} Command
28490 The corresponding @value{GDBN} command is @samp{delete}.
28492 @subsubheading Example
28500 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28501 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28502 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28503 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28504 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28505 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28506 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28511 @subheading The @code{-break-disable} Command
28512 @findex -break-disable
28514 @subsubheading Synopsis
28517 -break-disable ( @var{breakpoint} )+
28520 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28521 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28523 @subsubheading @value{GDBN} Command
28525 The corresponding @value{GDBN} command is @samp{disable}.
28527 @subsubheading Example
28535 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28536 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28537 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28538 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28539 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28540 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28541 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28542 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28543 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28544 line="5",thread-groups=["i1"],times="0"@}]@}
28548 @subheading The @code{-break-enable} Command
28549 @findex -break-enable
28551 @subsubheading Synopsis
28554 -break-enable ( @var{breakpoint} )+
28557 Enable (previously disabled) @var{breakpoint}(s).
28559 @subsubheading @value{GDBN} Command
28561 The corresponding @value{GDBN} command is @samp{enable}.
28563 @subsubheading Example
28571 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28572 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28573 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28574 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28575 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28576 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28577 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28578 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28579 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28580 line="5",thread-groups=["i1"],times="0"@}]@}
28584 @subheading The @code{-break-info} Command
28585 @findex -break-info
28587 @subsubheading Synopsis
28590 -break-info @var{breakpoint}
28594 Get information about a single breakpoint.
28596 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28597 Information}, for details on the format of each breakpoint in the
28600 @subsubheading @value{GDBN} Command
28602 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28604 @subsubheading Example
28607 @subheading The @code{-break-insert} Command
28608 @findex -break-insert
28610 @subsubheading Synopsis
28613 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28614 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28615 [ -p @var{thread-id} ] [ @var{location} ]
28619 If specified, @var{location}, can be one of:
28626 @item filename:linenum
28627 @item filename:function
28631 The possible optional parameters of this command are:
28635 Insert a temporary breakpoint.
28637 Insert a hardware breakpoint.
28639 If @var{location} cannot be parsed (for example if it
28640 refers to unknown files or functions), create a pending
28641 breakpoint. Without this flag, @value{GDBN} will report
28642 an error, and won't create a breakpoint, if @var{location}
28645 Create a disabled breakpoint.
28647 Create a tracepoint. @xref{Tracepoints}. When this parameter
28648 is used together with @samp{-h}, a fast tracepoint is created.
28649 @item -c @var{condition}
28650 Make the breakpoint conditional on @var{condition}.
28651 @item -i @var{ignore-count}
28652 Initialize the @var{ignore-count}.
28653 @item -p @var{thread-id}
28654 Restrict the breakpoint to the specified @var{thread-id}.
28657 @subsubheading Result
28659 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28660 resulting breakpoint.
28662 Note: this format is open to change.
28663 @c An out-of-band breakpoint instead of part of the result?
28665 @subsubheading @value{GDBN} Command
28667 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28668 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28670 @subsubheading Example
28675 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28676 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28679 -break-insert -t foo
28680 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28681 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28685 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28686 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28687 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28688 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28689 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28690 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28691 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28692 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28693 addr="0x0001072c", func="main",file="recursive2.c",
28694 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28696 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28697 addr="0x00010774",func="foo",file="recursive2.c",
28698 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28701 @c -break-insert -r foo.*
28702 @c ~int foo(int, int);
28703 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28704 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28709 @subheading The @code{-break-list} Command
28710 @findex -break-list
28712 @subsubheading Synopsis
28718 Displays the list of inserted breakpoints, showing the following fields:
28722 number of the breakpoint
28724 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28726 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28729 is the breakpoint enabled or no: @samp{y} or @samp{n}
28731 memory location at which the breakpoint is set
28733 logical location of the breakpoint, expressed by function name, file
28735 @item Thread-groups
28736 list of thread groups to which this breakpoint applies
28738 number of times the breakpoint has been hit
28741 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28742 @code{body} field is an empty list.
28744 @subsubheading @value{GDBN} Command
28746 The corresponding @value{GDBN} command is @samp{info break}.
28748 @subsubheading Example
28753 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28754 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28755 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28756 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28757 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28758 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28759 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28760 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28761 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28763 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28764 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28765 line="13",thread-groups=["i1"],times="0"@}]@}
28769 Here's an example of the result when there are no breakpoints:
28774 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28775 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28776 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28777 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28778 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28779 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28780 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28785 @subheading The @code{-break-passcount} Command
28786 @findex -break-passcount
28788 @subsubheading Synopsis
28791 -break-passcount @var{tracepoint-number} @var{passcount}
28794 Set the passcount for tracepoint @var{tracepoint-number} to
28795 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28796 is not a tracepoint, error is emitted. This corresponds to CLI
28797 command @samp{passcount}.
28799 @subheading The @code{-break-watch} Command
28800 @findex -break-watch
28802 @subsubheading Synopsis
28805 -break-watch [ -a | -r ]
28808 Create a watchpoint. With the @samp{-a} option it will create an
28809 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28810 read from or on a write to the memory location. With the @samp{-r}
28811 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28812 trigger only when the memory location is accessed for reading. Without
28813 either of the options, the watchpoint created is a regular watchpoint,
28814 i.e., it will trigger when the memory location is accessed for writing.
28815 @xref{Set Watchpoints, , Setting Watchpoints}.
28817 Note that @samp{-break-list} will report a single list of watchpoints and
28818 breakpoints inserted.
28820 @subsubheading @value{GDBN} Command
28822 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28825 @subsubheading Example
28827 Setting a watchpoint on a variable in the @code{main} function:
28832 ^done,wpt=@{number="2",exp="x"@}
28837 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
28838 value=@{old="-268439212",new="55"@},
28839 frame=@{func="main",args=[],file="recursive2.c",
28840 fullname="/home/foo/bar/recursive2.c",line="5"@}
28844 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
28845 the program execution twice: first for the variable changing value, then
28846 for the watchpoint going out of scope.
28851 ^done,wpt=@{number="5",exp="C"@}
28856 *stopped,reason="watchpoint-trigger",
28857 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
28858 frame=@{func="callee4",args=[],
28859 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28860 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28865 *stopped,reason="watchpoint-scope",wpnum="5",
28866 frame=@{func="callee3",args=[@{name="strarg",
28867 value="0x11940 \"A string argument.\""@}],
28868 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28869 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28873 Listing breakpoints and watchpoints, at different points in the program
28874 execution. Note that once the watchpoint goes out of scope, it is
28880 ^done,wpt=@{number="2",exp="C"@}
28883 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28884 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28885 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28886 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28887 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28888 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28889 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28890 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28891 addr="0x00010734",func="callee4",
28892 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28893 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
28895 bkpt=@{number="2",type="watchpoint",disp="keep",
28896 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
28901 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
28902 value=@{old="-276895068",new="3"@},
28903 frame=@{func="callee4",args=[],
28904 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28905 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
28908 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28909 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28910 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28911 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28912 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28913 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28914 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28915 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28916 addr="0x00010734",func="callee4",
28917 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28918 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
28920 bkpt=@{number="2",type="watchpoint",disp="keep",
28921 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
28925 ^done,reason="watchpoint-scope",wpnum="2",
28926 frame=@{func="callee3",args=[@{name="strarg",
28927 value="0x11940 \"A string argument.\""@}],
28928 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28929 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
28932 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28933 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28934 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28935 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28936 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28937 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28938 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28939 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28940 addr="0x00010734",func="callee4",
28941 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
28942 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
28943 thread-groups=["i1"],times="1"@}]@}
28948 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28949 @node GDB/MI Catchpoint Commands
28950 @section @sc{gdb/mi} Catchpoint Commands
28952 This section documents @sc{gdb/mi} commands for manipulating
28955 @subheading The @code{-catch-load} Command
28956 @findex -catch-load
28958 @subsubheading Synopsis
28961 -catch-load [ -t ] [ -d ] @var{regexp}
28964 Add a catchpoint for library load events. If the @samp{-t} option is used,
28965 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28966 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
28967 in a disabled state. The @samp{regexp} argument is a regular
28968 expression used to match the name of the loaded library.
28971 @subsubheading @value{GDBN} Command
28973 The corresponding @value{GDBN} command is @samp{catch load}.
28975 @subsubheading Example
28978 -catch-load -t foo.so
28979 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
28980 what="load of library matching foo.so",catch-type="load",times="0"@}
28985 @subheading The @code{-catch-unload} Command
28986 @findex -catch-unload
28988 @subsubheading Synopsis
28991 -catch-unload [ -t ] [ -d ] @var{regexp}
28994 Add a catchpoint for library unload events. If the @samp{-t} option is
28995 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
28996 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
28997 created in a disabled state. The @samp{regexp} argument is a regular
28998 expression used to match the name of the unloaded library.
29000 @subsubheading @value{GDBN} Command
29002 The corresponding @value{GDBN} command is @samp{catch unload}.
29004 @subsubheading Example
29007 -catch-unload -d bar.so
29008 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29009 what="load of library matching bar.so",catch-type="unload",times="0"@}
29014 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29015 @node GDB/MI Program Context
29016 @section @sc{gdb/mi} Program Context
29018 @subheading The @code{-exec-arguments} Command
29019 @findex -exec-arguments
29022 @subsubheading Synopsis
29025 -exec-arguments @var{args}
29028 Set the inferior program arguments, to be used in the next
29031 @subsubheading @value{GDBN} Command
29033 The corresponding @value{GDBN} command is @samp{set args}.
29035 @subsubheading Example
29039 -exec-arguments -v word
29046 @subheading The @code{-exec-show-arguments} Command
29047 @findex -exec-show-arguments
29049 @subsubheading Synopsis
29052 -exec-show-arguments
29055 Print the arguments of the program.
29057 @subsubheading @value{GDBN} Command
29059 The corresponding @value{GDBN} command is @samp{show args}.
29061 @subsubheading Example
29066 @subheading The @code{-environment-cd} Command
29067 @findex -environment-cd
29069 @subsubheading Synopsis
29072 -environment-cd @var{pathdir}
29075 Set @value{GDBN}'s working directory.
29077 @subsubheading @value{GDBN} Command
29079 The corresponding @value{GDBN} command is @samp{cd}.
29081 @subsubheading Example
29085 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29091 @subheading The @code{-environment-directory} Command
29092 @findex -environment-directory
29094 @subsubheading Synopsis
29097 -environment-directory [ -r ] [ @var{pathdir} ]+
29100 Add directories @var{pathdir} to beginning of search path for source files.
29101 If the @samp{-r} option is used, the search path is reset to the default
29102 search path. If directories @var{pathdir} are supplied in addition to the
29103 @samp{-r} option, the search path is first reset and then addition
29105 Multiple directories may be specified, separated by blanks. Specifying
29106 multiple directories in a single command
29107 results in the directories added to the beginning of the
29108 search path in the same order they were presented in the command.
29109 If blanks are needed as
29110 part of a directory name, double-quotes should be used around
29111 the name. In the command output, the path will show up separated
29112 by the system directory-separator character. The directory-separator
29113 character must not be used
29114 in any directory name.
29115 If no directories are specified, the current search path is displayed.
29117 @subsubheading @value{GDBN} Command
29119 The corresponding @value{GDBN} command is @samp{dir}.
29121 @subsubheading Example
29125 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29126 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29128 -environment-directory ""
29129 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29131 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29132 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29134 -environment-directory -r
29135 ^done,source-path="$cdir:$cwd"
29140 @subheading The @code{-environment-path} Command
29141 @findex -environment-path
29143 @subsubheading Synopsis
29146 -environment-path [ -r ] [ @var{pathdir} ]+
29149 Add directories @var{pathdir} to beginning of search path for object files.
29150 If the @samp{-r} option is used, the search path is reset to the original
29151 search path that existed at gdb start-up. If directories @var{pathdir} are
29152 supplied in addition to the
29153 @samp{-r} option, the search path is first reset and then addition
29155 Multiple directories may be specified, separated by blanks. Specifying
29156 multiple directories in a single command
29157 results in the directories added to the beginning of the
29158 search path in the same order they were presented in the command.
29159 If blanks are needed as
29160 part of a directory name, double-quotes should be used around
29161 the name. In the command output, the path will show up separated
29162 by the system directory-separator character. The directory-separator
29163 character must not be used
29164 in any directory name.
29165 If no directories are specified, the current path is displayed.
29168 @subsubheading @value{GDBN} Command
29170 The corresponding @value{GDBN} command is @samp{path}.
29172 @subsubheading Example
29177 ^done,path="/usr/bin"
29179 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29180 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29182 -environment-path -r /usr/local/bin
29183 ^done,path="/usr/local/bin:/usr/bin"
29188 @subheading The @code{-environment-pwd} Command
29189 @findex -environment-pwd
29191 @subsubheading Synopsis
29197 Show the current working directory.
29199 @subsubheading @value{GDBN} Command
29201 The corresponding @value{GDBN} command is @samp{pwd}.
29203 @subsubheading Example
29208 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29212 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29213 @node GDB/MI Thread Commands
29214 @section @sc{gdb/mi} Thread Commands
29217 @subheading The @code{-thread-info} Command
29218 @findex -thread-info
29220 @subsubheading Synopsis
29223 -thread-info [ @var{thread-id} ]
29226 Reports information about either a specific thread, if
29227 the @var{thread-id} parameter is present, or about all
29228 threads. When printing information about all threads,
29229 also reports the current thread.
29231 @subsubheading @value{GDBN} Command
29233 The @samp{info thread} command prints the same information
29236 @subsubheading Result
29238 The result is a list of threads. The following attributes are
29239 defined for a given thread:
29243 This field exists only for the current thread. It has the value @samp{*}.
29246 The identifier that @value{GDBN} uses to refer to the thread.
29249 The identifier that the target uses to refer to the thread.
29252 Extra information about the thread, in a target-specific format. This
29256 The name of the thread. If the user specified a name using the
29257 @code{thread name} command, then this name is given. Otherwise, if
29258 @value{GDBN} can extract the thread name from the target, then that
29259 name is given. If @value{GDBN} cannot find the thread name, then this
29263 The stack frame currently executing in the thread.
29266 The thread's state. The @samp{state} field may have the following
29271 The thread is stopped. Frame information is available for stopped
29275 The thread is running. There's no frame information for running
29281 If @value{GDBN} can find the CPU core on which this thread is running,
29282 then this field is the core identifier. This field is optional.
29286 @subsubheading Example
29291 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29292 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29293 args=[]@},state="running"@},
29294 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29295 frame=@{level="0",addr="0x0804891f",func="foo",
29296 args=[@{name="i",value="10"@}],
29297 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29298 state="running"@}],
29299 current-thread-id="1"
29303 @subheading The @code{-thread-list-ids} Command
29304 @findex -thread-list-ids
29306 @subsubheading Synopsis
29312 Produces a list of the currently known @value{GDBN} thread ids. At the
29313 end of the list it also prints the total number of such threads.
29315 This command is retained for historical reasons, the
29316 @code{-thread-info} command should be used instead.
29318 @subsubheading @value{GDBN} Command
29320 Part of @samp{info threads} supplies the same information.
29322 @subsubheading Example
29327 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29328 current-thread-id="1",number-of-threads="3"
29333 @subheading The @code{-thread-select} Command
29334 @findex -thread-select
29336 @subsubheading Synopsis
29339 -thread-select @var{threadnum}
29342 Make @var{threadnum} the current thread. It prints the number of the new
29343 current thread, and the topmost frame for that thread.
29345 This command is deprecated in favor of explicitly using the
29346 @samp{--thread} option to each command.
29348 @subsubheading @value{GDBN} Command
29350 The corresponding @value{GDBN} command is @samp{thread}.
29352 @subsubheading Example
29359 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29360 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29364 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29365 number-of-threads="3"
29368 ^done,new-thread-id="3",
29369 frame=@{level="0",func="vprintf",
29370 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29371 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29375 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29376 @node GDB/MI Ada Tasking Commands
29377 @section @sc{gdb/mi} Ada Tasking Commands
29379 @subheading The @code{-ada-task-info} Command
29380 @findex -ada-task-info
29382 @subsubheading Synopsis
29385 -ada-task-info [ @var{task-id} ]
29388 Reports information about either a specific Ada task, if the
29389 @var{task-id} parameter is present, or about all Ada tasks.
29391 @subsubheading @value{GDBN} Command
29393 The @samp{info tasks} command prints the same information
29394 about all Ada tasks (@pxref{Ada Tasks}).
29396 @subsubheading Result
29398 The result is a table of Ada tasks. The following columns are
29399 defined for each Ada task:
29403 This field exists only for the current thread. It has the value @samp{*}.
29406 The identifier that @value{GDBN} uses to refer to the Ada task.
29409 The identifier that the target uses to refer to the Ada task.
29412 The identifier of the thread corresponding to the Ada task.
29414 This field should always exist, as Ada tasks are always implemented
29415 on top of a thread. But if @value{GDBN} cannot find this corresponding
29416 thread for any reason, the field is omitted.
29419 This field exists only when the task was created by another task.
29420 In this case, it provides the ID of the parent task.
29423 The base priority of the task.
29426 The current state of the task. For a detailed description of the
29427 possible states, see @ref{Ada Tasks}.
29430 The name of the task.
29434 @subsubheading Example
29438 ^done,tasks=@{nr_rows="3",nr_cols="8",
29439 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29440 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29441 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29442 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29443 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29444 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29445 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29446 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29447 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29448 state="Child Termination Wait",name="main_task"@}]@}
29452 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29453 @node GDB/MI Program Execution
29454 @section @sc{gdb/mi} Program Execution
29456 These are the asynchronous commands which generate the out-of-band
29457 record @samp{*stopped}. Currently @value{GDBN} only really executes
29458 asynchronously with remote targets and this interaction is mimicked in
29461 @subheading The @code{-exec-continue} Command
29462 @findex -exec-continue
29464 @subsubheading Synopsis
29467 -exec-continue [--reverse] [--all|--thread-group N]
29470 Resumes the execution of the inferior program, which will continue
29471 to execute until it reaches a debugger stop event. If the
29472 @samp{--reverse} option is specified, execution resumes in reverse until
29473 it reaches a stop event. Stop events may include
29476 breakpoints or watchpoints
29478 signals or exceptions
29480 the end of the process (or its beginning under @samp{--reverse})
29482 the end or beginning of a replay log if one is being used.
29484 In all-stop mode (@pxref{All-Stop
29485 Mode}), may resume only one thread, or all threads, depending on the
29486 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29487 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29488 ignored in all-stop mode. If the @samp{--thread-group} options is
29489 specified, then all threads in that thread group are resumed.
29491 @subsubheading @value{GDBN} Command
29493 The corresponding @value{GDBN} corresponding is @samp{continue}.
29495 @subsubheading Example
29502 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29503 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29509 @subheading The @code{-exec-finish} Command
29510 @findex -exec-finish
29512 @subsubheading Synopsis
29515 -exec-finish [--reverse]
29518 Resumes the execution of the inferior program until the current
29519 function is exited. Displays the results returned by the function.
29520 If the @samp{--reverse} option is specified, resumes the reverse
29521 execution of the inferior program until the point where current
29522 function was called.
29524 @subsubheading @value{GDBN} Command
29526 The corresponding @value{GDBN} command is @samp{finish}.
29528 @subsubheading Example
29530 Function returning @code{void}.
29537 *stopped,reason="function-finished",frame=@{func="main",args=[],
29538 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29542 Function returning other than @code{void}. The name of the internal
29543 @value{GDBN} variable storing the result is printed, together with the
29550 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29551 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29552 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29553 gdb-result-var="$1",return-value="0"
29558 @subheading The @code{-exec-interrupt} Command
29559 @findex -exec-interrupt
29561 @subsubheading Synopsis
29564 -exec-interrupt [--all|--thread-group N]
29567 Interrupts the background execution of the target. Note how the token
29568 associated with the stop message is the one for the execution command
29569 that has been interrupted. The token for the interrupt itself only
29570 appears in the @samp{^done} output. If the user is trying to
29571 interrupt a non-running program, an error message will be printed.
29573 Note that when asynchronous execution is enabled, this command is
29574 asynchronous just like other execution commands. That is, first the
29575 @samp{^done} response will be printed, and the target stop will be
29576 reported after that using the @samp{*stopped} notification.
29578 In non-stop mode, only the context thread is interrupted by default.
29579 All threads (in all inferiors) will be interrupted if the
29580 @samp{--all} option is specified. If the @samp{--thread-group}
29581 option is specified, all threads in that group will be interrupted.
29583 @subsubheading @value{GDBN} Command
29585 The corresponding @value{GDBN} command is @samp{interrupt}.
29587 @subsubheading Example
29598 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29599 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29600 fullname="/home/foo/bar/try.c",line="13"@}
29605 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29609 @subheading The @code{-exec-jump} Command
29612 @subsubheading Synopsis
29615 -exec-jump @var{location}
29618 Resumes execution of the inferior program at the location specified by
29619 parameter. @xref{Specify Location}, for a description of the
29620 different forms of @var{location}.
29622 @subsubheading @value{GDBN} Command
29624 The corresponding @value{GDBN} command is @samp{jump}.
29626 @subsubheading Example
29629 -exec-jump foo.c:10
29630 *running,thread-id="all"
29635 @subheading The @code{-exec-next} Command
29638 @subsubheading Synopsis
29641 -exec-next [--reverse]
29644 Resumes execution of the inferior program, stopping when the beginning
29645 of the next source line is reached.
29647 If the @samp{--reverse} option is specified, resumes reverse execution
29648 of the inferior program, stopping at the beginning of the previous
29649 source line. If you issue this command on the first line of a
29650 function, it will take you back to the caller of that function, to the
29651 source line where the function was called.
29654 @subsubheading @value{GDBN} Command
29656 The corresponding @value{GDBN} command is @samp{next}.
29658 @subsubheading Example
29664 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29669 @subheading The @code{-exec-next-instruction} Command
29670 @findex -exec-next-instruction
29672 @subsubheading Synopsis
29675 -exec-next-instruction [--reverse]
29678 Executes one machine instruction. If the instruction is a function
29679 call, continues until the function returns. If the program stops at an
29680 instruction in the middle of a source line, the address will be
29683 If the @samp{--reverse} option is specified, resumes reverse execution
29684 of the inferior program, stopping at the previous instruction. If the
29685 previously executed instruction was a return from another function,
29686 it will continue to execute in reverse until the call to that function
29687 (from the current stack frame) is reached.
29689 @subsubheading @value{GDBN} Command
29691 The corresponding @value{GDBN} command is @samp{nexti}.
29693 @subsubheading Example
29697 -exec-next-instruction
29701 *stopped,reason="end-stepping-range",
29702 addr="0x000100d4",line="5",file="hello.c"
29707 @subheading The @code{-exec-return} Command
29708 @findex -exec-return
29710 @subsubheading Synopsis
29716 Makes current function return immediately. Doesn't execute the inferior.
29717 Displays the new current frame.
29719 @subsubheading @value{GDBN} Command
29721 The corresponding @value{GDBN} command is @samp{return}.
29723 @subsubheading Example
29727 200-break-insert callee4
29728 200^done,bkpt=@{number="1",addr="0x00010734",
29729 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29734 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29735 frame=@{func="callee4",args=[],
29736 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29737 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29743 111^done,frame=@{level="0",func="callee3",
29744 args=[@{name="strarg",
29745 value="0x11940 \"A string argument.\""@}],
29746 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29747 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29752 @subheading The @code{-exec-run} Command
29755 @subsubheading Synopsis
29758 -exec-run [--all | --thread-group N]
29761 Starts execution of the inferior from the beginning. The inferior
29762 executes until either a breakpoint is encountered or the program
29763 exits. In the latter case the output will include an exit code, if
29764 the program has exited exceptionally.
29766 When no option is specified, the current inferior is started. If the
29767 @samp{--thread-group} option is specified, it should refer to a thread
29768 group of type @samp{process}, and that thread group will be started.
29769 If the @samp{--all} option is specified, then all inferiors will be started.
29771 @subsubheading @value{GDBN} Command
29773 The corresponding @value{GDBN} command is @samp{run}.
29775 @subsubheading Examples
29780 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29785 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29786 frame=@{func="main",args=[],file="recursive2.c",
29787 fullname="/home/foo/bar/recursive2.c",line="4"@}
29792 Program exited normally:
29800 *stopped,reason="exited-normally"
29805 Program exited exceptionally:
29813 *stopped,reason="exited",exit-code="01"
29817 Another way the program can terminate is if it receives a signal such as
29818 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29822 *stopped,reason="exited-signalled",signal-name="SIGINT",
29823 signal-meaning="Interrupt"
29827 @c @subheading -exec-signal
29830 @subheading The @code{-exec-step} Command
29833 @subsubheading Synopsis
29836 -exec-step [--reverse]
29839 Resumes execution of the inferior program, stopping when the beginning
29840 of the next source line is reached, if the next source line is not a
29841 function call. If it is, stop at the first instruction of the called
29842 function. If the @samp{--reverse} option is specified, resumes reverse
29843 execution of the inferior program, stopping at the beginning of the
29844 previously executed source line.
29846 @subsubheading @value{GDBN} Command
29848 The corresponding @value{GDBN} command is @samp{step}.
29850 @subsubheading Example
29852 Stepping into a function:
29858 *stopped,reason="end-stepping-range",
29859 frame=@{func="foo",args=[@{name="a",value="10"@},
29860 @{name="b",value="0"@}],file="recursive2.c",
29861 fullname="/home/foo/bar/recursive2.c",line="11"@}
29871 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
29876 @subheading The @code{-exec-step-instruction} Command
29877 @findex -exec-step-instruction
29879 @subsubheading Synopsis
29882 -exec-step-instruction [--reverse]
29885 Resumes the inferior which executes one machine instruction. If the
29886 @samp{--reverse} option is specified, resumes reverse execution of the
29887 inferior program, stopping at the previously executed instruction.
29888 The output, once @value{GDBN} has stopped, will vary depending on
29889 whether we have stopped in the middle of a source line or not. In the
29890 former case, the address at which the program stopped will be printed
29893 @subsubheading @value{GDBN} Command
29895 The corresponding @value{GDBN} command is @samp{stepi}.
29897 @subsubheading Example
29901 -exec-step-instruction
29905 *stopped,reason="end-stepping-range",
29906 frame=@{func="foo",args=[],file="try.c",
29907 fullname="/home/foo/bar/try.c",line="10"@}
29909 -exec-step-instruction
29913 *stopped,reason="end-stepping-range",
29914 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
29915 fullname="/home/foo/bar/try.c",line="10"@}
29920 @subheading The @code{-exec-until} Command
29921 @findex -exec-until
29923 @subsubheading Synopsis
29926 -exec-until [ @var{location} ]
29929 Executes the inferior until the @var{location} specified in the
29930 argument is reached. If there is no argument, the inferior executes
29931 until a source line greater than the current one is reached. The
29932 reason for stopping in this case will be @samp{location-reached}.
29934 @subsubheading @value{GDBN} Command
29936 The corresponding @value{GDBN} command is @samp{until}.
29938 @subsubheading Example
29942 -exec-until recursive2.c:6
29946 *stopped,reason="location-reached",frame=@{func="main",args=[],
29947 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
29952 @subheading -file-clear
29953 Is this going away????
29956 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29957 @node GDB/MI Stack Manipulation
29958 @section @sc{gdb/mi} Stack Manipulation Commands
29961 @subheading The @code{-stack-info-frame} Command
29962 @findex -stack-info-frame
29964 @subsubheading Synopsis
29970 Get info on the selected frame.
29972 @subsubheading @value{GDBN} Command
29974 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
29975 (without arguments).
29977 @subsubheading Example
29982 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
29983 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29984 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
29988 @subheading The @code{-stack-info-depth} Command
29989 @findex -stack-info-depth
29991 @subsubheading Synopsis
29994 -stack-info-depth [ @var{max-depth} ]
29997 Return the depth of the stack. If the integer argument @var{max-depth}
29998 is specified, do not count beyond @var{max-depth} frames.
30000 @subsubheading @value{GDBN} Command
30002 There's no equivalent @value{GDBN} command.
30004 @subsubheading Example
30006 For a stack with frame levels 0 through 11:
30013 -stack-info-depth 4
30016 -stack-info-depth 12
30019 -stack-info-depth 11
30022 -stack-info-depth 13
30027 @subheading The @code{-stack-list-arguments} Command
30028 @findex -stack-list-arguments
30030 @subsubheading Synopsis
30033 -stack-list-arguments @var{print-values}
30034 [ @var{low-frame} @var{high-frame} ]
30037 Display a list of the arguments for the frames between @var{low-frame}
30038 and @var{high-frame} (inclusive). If @var{low-frame} and
30039 @var{high-frame} are not provided, list the arguments for the whole
30040 call stack. If the two arguments are equal, show the single frame
30041 at the corresponding level. It is an error if @var{low-frame} is
30042 larger than the actual number of frames. On the other hand,
30043 @var{high-frame} may be larger than the actual number of frames, in
30044 which case only existing frames will be returned.
30046 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30047 the variables; if it is 1 or @code{--all-values}, print also their
30048 values; and if it is 2 or @code{--simple-values}, print the name,
30049 type and value for simple data types, and the name and type for arrays,
30050 structures and unions.
30052 Use of this command to obtain arguments in a single frame is
30053 deprecated in favor of the @samp{-stack-list-variables} command.
30055 @subsubheading @value{GDBN} Command
30057 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30058 @samp{gdb_get_args} command which partially overlaps with the
30059 functionality of @samp{-stack-list-arguments}.
30061 @subsubheading Example
30068 frame=@{level="0",addr="0x00010734",func="callee4",
30069 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30070 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30071 frame=@{level="1",addr="0x0001076c",func="callee3",
30072 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30073 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30074 frame=@{level="2",addr="0x0001078c",func="callee2",
30075 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30076 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30077 frame=@{level="3",addr="0x000107b4",func="callee1",
30078 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30079 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30080 frame=@{level="4",addr="0x000107e0",func="main",
30081 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30082 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30084 -stack-list-arguments 0
30087 frame=@{level="0",args=[]@},
30088 frame=@{level="1",args=[name="strarg"]@},
30089 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30090 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30091 frame=@{level="4",args=[]@}]
30093 -stack-list-arguments 1
30096 frame=@{level="0",args=[]@},
30098 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30099 frame=@{level="2",args=[
30100 @{name="intarg",value="2"@},
30101 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30102 @{frame=@{level="3",args=[
30103 @{name="intarg",value="2"@},
30104 @{name="strarg",value="0x11940 \"A string argument.\""@},
30105 @{name="fltarg",value="3.5"@}]@},
30106 frame=@{level="4",args=[]@}]
30108 -stack-list-arguments 0 2 2
30109 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30111 -stack-list-arguments 1 2 2
30112 ^done,stack-args=[frame=@{level="2",
30113 args=[@{name="intarg",value="2"@},
30114 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30118 @c @subheading -stack-list-exception-handlers
30121 @subheading The @code{-stack-list-frames} Command
30122 @findex -stack-list-frames
30124 @subsubheading Synopsis
30127 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30130 List the frames currently on the stack. For each frame it displays the
30135 The frame number, 0 being the topmost frame, i.e., the innermost function.
30137 The @code{$pc} value for that frame.
30141 File name of the source file where the function lives.
30142 @item @var{fullname}
30143 The full file name of the source file where the function lives.
30145 Line number corresponding to the @code{$pc}.
30147 The shared library where this function is defined. This is only given
30148 if the frame's function is not known.
30151 If invoked without arguments, this command prints a backtrace for the
30152 whole stack. If given two integer arguments, it shows the frames whose
30153 levels are between the two arguments (inclusive). If the two arguments
30154 are equal, it shows the single frame at the corresponding level. It is
30155 an error if @var{low-frame} is larger than the actual number of
30156 frames. On the other hand, @var{high-frame} may be larger than the
30157 actual number of frames, in which case only existing frames will be returned.
30159 @subsubheading @value{GDBN} Command
30161 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30163 @subsubheading Example
30165 Full stack backtrace:
30171 [frame=@{level="0",addr="0x0001076c",func="foo",
30172 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30173 frame=@{level="1",addr="0x000107a4",func="foo",
30174 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30175 frame=@{level="2",addr="0x000107a4",func="foo",
30176 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30177 frame=@{level="3",addr="0x000107a4",func="foo",
30178 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30179 frame=@{level="4",addr="0x000107a4",func="foo",
30180 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30181 frame=@{level="5",addr="0x000107a4",func="foo",
30182 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30183 frame=@{level="6",addr="0x000107a4",func="foo",
30184 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30185 frame=@{level="7",addr="0x000107a4",func="foo",
30186 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30187 frame=@{level="8",addr="0x000107a4",func="foo",
30188 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30189 frame=@{level="9",addr="0x000107a4",func="foo",
30190 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30191 frame=@{level="10",addr="0x000107a4",func="foo",
30192 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30193 frame=@{level="11",addr="0x00010738",func="main",
30194 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30198 Show frames between @var{low_frame} and @var{high_frame}:
30202 -stack-list-frames 3 5
30204 [frame=@{level="3",addr="0x000107a4",func="foo",
30205 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30206 frame=@{level="4",addr="0x000107a4",func="foo",
30207 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30208 frame=@{level="5",addr="0x000107a4",func="foo",
30209 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30213 Show a single frame:
30217 -stack-list-frames 3 3
30219 [frame=@{level="3",addr="0x000107a4",func="foo",
30220 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30225 @subheading The @code{-stack-list-locals} Command
30226 @findex -stack-list-locals
30228 @subsubheading Synopsis
30231 -stack-list-locals @var{print-values}
30234 Display the local variable names for the selected frame. If
30235 @var{print-values} is 0 or @code{--no-values}, print only the names of
30236 the variables; if it is 1 or @code{--all-values}, print also their
30237 values; and if it is 2 or @code{--simple-values}, print the name,
30238 type and value for simple data types, and the name and type for arrays,
30239 structures and unions. In this last case, a frontend can immediately
30240 display the value of simple data types and create variable objects for
30241 other data types when the user wishes to explore their values in
30244 This command is deprecated in favor of the
30245 @samp{-stack-list-variables} command.
30247 @subsubheading @value{GDBN} Command
30249 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30251 @subsubheading Example
30255 -stack-list-locals 0
30256 ^done,locals=[name="A",name="B",name="C"]
30258 -stack-list-locals --all-values
30259 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30260 @{name="C",value="@{1, 2, 3@}"@}]
30261 -stack-list-locals --simple-values
30262 ^done,locals=[@{name="A",type="int",value="1"@},
30263 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30267 @subheading The @code{-stack-list-variables} Command
30268 @findex -stack-list-variables
30270 @subsubheading Synopsis
30273 -stack-list-variables @var{print-values}
30276 Display the names of local variables and function arguments for the selected frame. If
30277 @var{print-values} is 0 or @code{--no-values}, print only the names of
30278 the variables; if it is 1 or @code{--all-values}, print also their
30279 values; and if it is 2 or @code{--simple-values}, print the name,
30280 type and value for simple data types, and the name and type for arrays,
30281 structures and unions.
30283 @subsubheading Example
30287 -stack-list-variables --thread 1 --frame 0 --all-values
30288 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30293 @subheading The @code{-stack-select-frame} Command
30294 @findex -stack-select-frame
30296 @subsubheading Synopsis
30299 -stack-select-frame @var{framenum}
30302 Change the selected frame. Select a different frame @var{framenum} on
30305 This command in deprecated in favor of passing the @samp{--frame}
30306 option to every command.
30308 @subsubheading @value{GDBN} Command
30310 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30311 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30313 @subsubheading Example
30317 -stack-select-frame 2
30322 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30323 @node GDB/MI Variable Objects
30324 @section @sc{gdb/mi} Variable Objects
30328 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30330 For the implementation of a variable debugger window (locals, watched
30331 expressions, etc.), we are proposing the adaptation of the existing code
30332 used by @code{Insight}.
30334 The two main reasons for that are:
30338 It has been proven in practice (it is already on its second generation).
30341 It will shorten development time (needless to say how important it is
30345 The original interface was designed to be used by Tcl code, so it was
30346 slightly changed so it could be used through @sc{gdb/mi}. This section
30347 describes the @sc{gdb/mi} operations that will be available and gives some
30348 hints about their use.
30350 @emph{Note}: In addition to the set of operations described here, we
30351 expect the @sc{gui} implementation of a variable window to require, at
30352 least, the following operations:
30355 @item @code{-gdb-show} @code{output-radix}
30356 @item @code{-stack-list-arguments}
30357 @item @code{-stack-list-locals}
30358 @item @code{-stack-select-frame}
30363 @subheading Introduction to Variable Objects
30365 @cindex variable objects in @sc{gdb/mi}
30367 Variable objects are "object-oriented" MI interface for examining and
30368 changing values of expressions. Unlike some other MI interfaces that
30369 work with expressions, variable objects are specifically designed for
30370 simple and efficient presentation in the frontend. A variable object
30371 is identified by string name. When a variable object is created, the
30372 frontend specifies the expression for that variable object. The
30373 expression can be a simple variable, or it can be an arbitrary complex
30374 expression, and can even involve CPU registers. After creating a
30375 variable object, the frontend can invoke other variable object
30376 operations---for example to obtain or change the value of a variable
30377 object, or to change display format.
30379 Variable objects have hierarchical tree structure. Any variable object
30380 that corresponds to a composite type, such as structure in C, has
30381 a number of child variable objects, for example corresponding to each
30382 element of a structure. A child variable object can itself have
30383 children, recursively. Recursion ends when we reach
30384 leaf variable objects, which always have built-in types. Child variable
30385 objects are created only by explicit request, so if a frontend
30386 is not interested in the children of a particular variable object, no
30387 child will be created.
30389 For a leaf variable object it is possible to obtain its value as a
30390 string, or set the value from a string. String value can be also
30391 obtained for a non-leaf variable object, but it's generally a string
30392 that only indicates the type of the object, and does not list its
30393 contents. Assignment to a non-leaf variable object is not allowed.
30395 A frontend does not need to read the values of all variable objects each time
30396 the program stops. Instead, MI provides an update command that lists all
30397 variable objects whose values has changed since the last update
30398 operation. This considerably reduces the amount of data that must
30399 be transferred to the frontend. As noted above, children variable
30400 objects are created on demand, and only leaf variable objects have a
30401 real value. As result, gdb will read target memory only for leaf
30402 variables that frontend has created.
30404 The automatic update is not always desirable. For example, a frontend
30405 might want to keep a value of some expression for future reference,
30406 and never update it. For another example, fetching memory is
30407 relatively slow for embedded targets, so a frontend might want
30408 to disable automatic update for the variables that are either not
30409 visible on the screen, or ``closed''. This is possible using so
30410 called ``frozen variable objects''. Such variable objects are never
30411 implicitly updated.
30413 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30414 fixed variable object, the expression is parsed when the variable
30415 object is created, including associating identifiers to specific
30416 variables. The meaning of expression never changes. For a floating
30417 variable object the values of variables whose names appear in the
30418 expressions are re-evaluated every time in the context of the current
30419 frame. Consider this example:
30424 struct work_state state;
30431 If a fixed variable object for the @code{state} variable is created in
30432 this function, and we enter the recursive call, the variable
30433 object will report the value of @code{state} in the top-level
30434 @code{do_work} invocation. On the other hand, a floating variable
30435 object will report the value of @code{state} in the current frame.
30437 If an expression specified when creating a fixed variable object
30438 refers to a local variable, the variable object becomes bound to the
30439 thread and frame in which the variable object is created. When such
30440 variable object is updated, @value{GDBN} makes sure that the
30441 thread/frame combination the variable object is bound to still exists,
30442 and re-evaluates the variable object in context of that thread/frame.
30444 The following is the complete set of @sc{gdb/mi} operations defined to
30445 access this functionality:
30447 @multitable @columnfractions .4 .6
30448 @item @strong{Operation}
30449 @tab @strong{Description}
30451 @item @code{-enable-pretty-printing}
30452 @tab enable Python-based pretty-printing
30453 @item @code{-var-create}
30454 @tab create a variable object
30455 @item @code{-var-delete}
30456 @tab delete the variable object and/or its children
30457 @item @code{-var-set-format}
30458 @tab set the display format of this variable
30459 @item @code{-var-show-format}
30460 @tab show the display format of this variable
30461 @item @code{-var-info-num-children}
30462 @tab tells how many children this object has
30463 @item @code{-var-list-children}
30464 @tab return a list of the object's children
30465 @item @code{-var-info-type}
30466 @tab show the type of this variable object
30467 @item @code{-var-info-expression}
30468 @tab print parent-relative expression that this variable object represents
30469 @item @code{-var-info-path-expression}
30470 @tab print full expression that this variable object represents
30471 @item @code{-var-show-attributes}
30472 @tab is this variable editable? does it exist here?
30473 @item @code{-var-evaluate-expression}
30474 @tab get the value of this variable
30475 @item @code{-var-assign}
30476 @tab set the value of this variable
30477 @item @code{-var-update}
30478 @tab update the variable and its children
30479 @item @code{-var-set-frozen}
30480 @tab set frozeness attribute
30481 @item @code{-var-set-update-range}
30482 @tab set range of children to display on update
30485 In the next subsection we describe each operation in detail and suggest
30486 how it can be used.
30488 @subheading Description And Use of Operations on Variable Objects
30490 @subheading The @code{-enable-pretty-printing} Command
30491 @findex -enable-pretty-printing
30494 -enable-pretty-printing
30497 @value{GDBN} allows Python-based visualizers to affect the output of the
30498 MI variable object commands. However, because there was no way to
30499 implement this in a fully backward-compatible way, a front end must
30500 request that this functionality be enabled.
30502 Once enabled, this feature cannot be disabled.
30504 Note that if Python support has not been compiled into @value{GDBN},
30505 this command will still succeed (and do nothing).
30507 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30508 may work differently in future versions of @value{GDBN}.
30510 @subheading The @code{-var-create} Command
30511 @findex -var-create
30513 @subsubheading Synopsis
30516 -var-create @{@var{name} | "-"@}
30517 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30520 This operation creates a variable object, which allows the monitoring of
30521 a variable, the result of an expression, a memory cell or a CPU
30524 The @var{name} parameter is the string by which the object can be
30525 referenced. It must be unique. If @samp{-} is specified, the varobj
30526 system will generate a string ``varNNNNNN'' automatically. It will be
30527 unique provided that one does not specify @var{name} of that format.
30528 The command fails if a duplicate name is found.
30530 The frame under which the expression should be evaluated can be
30531 specified by @var{frame-addr}. A @samp{*} indicates that the current
30532 frame should be used. A @samp{@@} indicates that a floating variable
30533 object must be created.
30535 @var{expression} is any expression valid on the current language set (must not
30536 begin with a @samp{*}), or one of the following:
30540 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30543 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30546 @samp{$@var{regname}} --- a CPU register name
30549 @cindex dynamic varobj
30550 A varobj's contents may be provided by a Python-based pretty-printer. In this
30551 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30552 have slightly different semantics in some cases. If the
30553 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30554 will never create a dynamic varobj. This ensures backward
30555 compatibility for existing clients.
30557 @subsubheading Result
30559 This operation returns attributes of the newly-created varobj. These
30564 The name of the varobj.
30567 The number of children of the varobj. This number is not necessarily
30568 reliable for a dynamic varobj. Instead, you must examine the
30569 @samp{has_more} attribute.
30572 The varobj's scalar value. For a varobj whose type is some sort of
30573 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30574 will not be interesting.
30577 The varobj's type. This is a string representation of the type, as
30578 would be printed by the @value{GDBN} CLI. If @samp{print object}
30579 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30580 @emph{actual} (derived) type of the object is shown rather than the
30581 @emph{declared} one.
30584 If a variable object is bound to a specific thread, then this is the
30585 thread's identifier.
30588 For a dynamic varobj, this indicates whether there appear to be any
30589 children available. For a non-dynamic varobj, this will be 0.
30592 This attribute will be present and have the value @samp{1} if the
30593 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30594 then this attribute will not be present.
30597 A dynamic varobj can supply a display hint to the front end. The
30598 value comes directly from the Python pretty-printer object's
30599 @code{display_hint} method. @xref{Pretty Printing API}.
30602 Typical output will look like this:
30605 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30606 has_more="@var{has_more}"
30610 @subheading The @code{-var-delete} Command
30611 @findex -var-delete
30613 @subsubheading Synopsis
30616 -var-delete [ -c ] @var{name}
30619 Deletes a previously created variable object and all of its children.
30620 With the @samp{-c} option, just deletes the children.
30622 Returns an error if the object @var{name} is not found.
30625 @subheading The @code{-var-set-format} Command
30626 @findex -var-set-format
30628 @subsubheading Synopsis
30631 -var-set-format @var{name} @var{format-spec}
30634 Sets the output format for the value of the object @var{name} to be
30637 @anchor{-var-set-format}
30638 The syntax for the @var{format-spec} is as follows:
30641 @var{format-spec} @expansion{}
30642 @{binary | decimal | hexadecimal | octal | natural@}
30645 The natural format is the default format choosen automatically
30646 based on the variable type (like decimal for an @code{int}, hex
30647 for pointers, etc.).
30649 For a variable with children, the format is set only on the
30650 variable itself, and the children are not affected.
30652 @subheading The @code{-var-show-format} Command
30653 @findex -var-show-format
30655 @subsubheading Synopsis
30658 -var-show-format @var{name}
30661 Returns the format used to display the value of the object @var{name}.
30664 @var{format} @expansion{}
30669 @subheading The @code{-var-info-num-children} Command
30670 @findex -var-info-num-children
30672 @subsubheading Synopsis
30675 -var-info-num-children @var{name}
30678 Returns the number of children of a variable object @var{name}:
30684 Note that this number is not completely reliable for a dynamic varobj.
30685 It will return the current number of children, but more children may
30689 @subheading The @code{-var-list-children} Command
30690 @findex -var-list-children
30692 @subsubheading Synopsis
30695 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30697 @anchor{-var-list-children}
30699 Return a list of the children of the specified variable object and
30700 create variable objects for them, if they do not already exist. With
30701 a single argument or if @var{print-values} has a value of 0 or
30702 @code{--no-values}, print only the names of the variables; if
30703 @var{print-values} is 1 or @code{--all-values}, also print their
30704 values; and if it is 2 or @code{--simple-values} print the name and
30705 value for simple data types and just the name for arrays, structures
30708 @var{from} and @var{to}, if specified, indicate the range of children
30709 to report. If @var{from} or @var{to} is less than zero, the range is
30710 reset and all children will be reported. Otherwise, children starting
30711 at @var{from} (zero-based) and up to and excluding @var{to} will be
30714 If a child range is requested, it will only affect the current call to
30715 @code{-var-list-children}, but not future calls to @code{-var-update}.
30716 For this, you must instead use @code{-var-set-update-range}. The
30717 intent of this approach is to enable a front end to implement any
30718 update approach it likes; for example, scrolling a view may cause the
30719 front end to request more children with @code{-var-list-children}, and
30720 then the front end could call @code{-var-set-update-range} with a
30721 different range to ensure that future updates are restricted to just
30724 For each child the following results are returned:
30729 Name of the variable object created for this child.
30732 The expression to be shown to the user by the front end to designate this child.
30733 For example this may be the name of a structure member.
30735 For a dynamic varobj, this value cannot be used to form an
30736 expression. There is no way to do this at all with a dynamic varobj.
30738 For C/C@t{++} structures there are several pseudo children returned to
30739 designate access qualifiers. For these pseudo children @var{exp} is
30740 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30741 type and value are not present.
30743 A dynamic varobj will not report the access qualifying
30744 pseudo-children, regardless of the language. This information is not
30745 available at all with a dynamic varobj.
30748 Number of children this child has. For a dynamic varobj, this will be
30752 The type of the child. If @samp{print object}
30753 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30754 @emph{actual} (derived) type of the object is shown rather than the
30755 @emph{declared} one.
30758 If values were requested, this is the value.
30761 If this variable object is associated with a thread, this is the thread id.
30762 Otherwise this result is not present.
30765 If the variable object is frozen, this variable will be present with a value of 1.
30768 The result may have its own attributes:
30772 A dynamic varobj can supply a display hint to the front end. The
30773 value comes directly from the Python pretty-printer object's
30774 @code{display_hint} method. @xref{Pretty Printing API}.
30777 This is an integer attribute which is nonzero if there are children
30778 remaining after the end of the selected range.
30781 @subsubheading Example
30785 -var-list-children n
30786 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30787 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30789 -var-list-children --all-values n
30790 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30791 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30795 @subheading The @code{-var-info-type} Command
30796 @findex -var-info-type
30798 @subsubheading Synopsis
30801 -var-info-type @var{name}
30804 Returns the type of the specified variable @var{name}. The type is
30805 returned as a string in the same format as it is output by the
30809 type=@var{typename}
30813 @subheading The @code{-var-info-expression} Command
30814 @findex -var-info-expression
30816 @subsubheading Synopsis
30819 -var-info-expression @var{name}
30822 Returns a string that is suitable for presenting this
30823 variable object in user interface. The string is generally
30824 not valid expression in the current language, and cannot be evaluated.
30826 For example, if @code{a} is an array, and variable object
30827 @code{A} was created for @code{a}, then we'll get this output:
30830 (gdb) -var-info-expression A.1
30831 ^done,lang="C",exp="1"
30835 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
30837 Note that the output of the @code{-var-list-children} command also
30838 includes those expressions, so the @code{-var-info-expression} command
30841 @subheading The @code{-var-info-path-expression} Command
30842 @findex -var-info-path-expression
30844 @subsubheading Synopsis
30847 -var-info-path-expression @var{name}
30850 Returns an expression that can be evaluated in the current
30851 context and will yield the same value that a variable object has.
30852 Compare this with the @code{-var-info-expression} command, which
30853 result can be used only for UI presentation. Typical use of
30854 the @code{-var-info-path-expression} command is creating a
30855 watchpoint from a variable object.
30857 This command is currently not valid for children of a dynamic varobj,
30858 and will give an error when invoked on one.
30860 For example, suppose @code{C} is a C@t{++} class, derived from class
30861 @code{Base}, and that the @code{Base} class has a member called
30862 @code{m_size}. Assume a variable @code{c} is has the type of
30863 @code{C} and a variable object @code{C} was created for variable
30864 @code{c}. Then, we'll get this output:
30866 (gdb) -var-info-path-expression C.Base.public.m_size
30867 ^done,path_expr=((Base)c).m_size)
30870 @subheading The @code{-var-show-attributes} Command
30871 @findex -var-show-attributes
30873 @subsubheading Synopsis
30876 -var-show-attributes @var{name}
30879 List attributes of the specified variable object @var{name}:
30882 status=@var{attr} [ ( ,@var{attr} )* ]
30886 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
30888 @subheading The @code{-var-evaluate-expression} Command
30889 @findex -var-evaluate-expression
30891 @subsubheading Synopsis
30894 -var-evaluate-expression [-f @var{format-spec}] @var{name}
30897 Evaluates the expression that is represented by the specified variable
30898 object and returns its value as a string. The format of the string
30899 can be specified with the @samp{-f} option. The possible values of
30900 this option are the same as for @code{-var-set-format}
30901 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
30902 the current display format will be used. The current display format
30903 can be changed using the @code{-var-set-format} command.
30909 Note that one must invoke @code{-var-list-children} for a variable
30910 before the value of a child variable can be evaluated.
30912 @subheading The @code{-var-assign} Command
30913 @findex -var-assign
30915 @subsubheading Synopsis
30918 -var-assign @var{name} @var{expression}
30921 Assigns the value of @var{expression} to the variable object specified
30922 by @var{name}. The object must be @samp{editable}. If the variable's
30923 value is altered by the assign, the variable will show up in any
30924 subsequent @code{-var-update} list.
30926 @subsubheading Example
30934 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
30938 @subheading The @code{-var-update} Command
30939 @findex -var-update
30941 @subsubheading Synopsis
30944 -var-update [@var{print-values}] @{@var{name} | "*"@}
30947 Reevaluate the expressions corresponding to the variable object
30948 @var{name} and all its direct and indirect children, and return the
30949 list of variable objects whose values have changed; @var{name} must
30950 be a root variable object. Here, ``changed'' means that the result of
30951 @code{-var-evaluate-expression} before and after the
30952 @code{-var-update} is different. If @samp{*} is used as the variable
30953 object names, all existing variable objects are updated, except
30954 for frozen ones (@pxref{-var-set-frozen}). The option
30955 @var{print-values} determines whether both names and values, or just
30956 names are printed. The possible values of this option are the same
30957 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
30958 recommended to use the @samp{--all-values} option, to reduce the
30959 number of MI commands needed on each program stop.
30961 With the @samp{*} parameter, if a variable object is bound to a
30962 currently running thread, it will not be updated, without any
30965 If @code{-var-set-update-range} was previously used on a varobj, then
30966 only the selected range of children will be reported.
30968 @code{-var-update} reports all the changed varobjs in a tuple named
30971 Each item in the change list is itself a tuple holding:
30975 The name of the varobj.
30978 If values were requested for this update, then this field will be
30979 present and will hold the value of the varobj.
30982 @anchor{-var-update}
30983 This field is a string which may take one of three values:
30987 The variable object's current value is valid.
30990 The variable object does not currently hold a valid value but it may
30991 hold one in the future if its associated expression comes back into
30995 The variable object no longer holds a valid value.
30996 This can occur when the executable file being debugged has changed,
30997 either through recompilation or by using the @value{GDBN} @code{file}
30998 command. The front end should normally choose to delete these variable
31002 In the future new values may be added to this list so the front should
31003 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31006 This is only present if the varobj is still valid. If the type
31007 changed, then this will be the string @samp{true}; otherwise it will
31010 When a varobj's type changes, its children are also likely to have
31011 become incorrect. Therefore, the varobj's children are automatically
31012 deleted when this attribute is @samp{true}. Also, the varobj's update
31013 range, when set using the @code{-var-set-update-range} command, is
31017 If the varobj's type changed, then this field will be present and will
31020 @item new_num_children
31021 For a dynamic varobj, if the number of children changed, or if the
31022 type changed, this will be the new number of children.
31024 The @samp{numchild} field in other varobj responses is generally not
31025 valid for a dynamic varobj -- it will show the number of children that
31026 @value{GDBN} knows about, but because dynamic varobjs lazily
31027 instantiate their children, this will not reflect the number of
31028 children which may be available.
31030 The @samp{new_num_children} attribute only reports changes to the
31031 number of children known by @value{GDBN}. This is the only way to
31032 detect whether an update has removed children (which necessarily can
31033 only happen at the end of the update range).
31036 The display hint, if any.
31039 This is an integer value, which will be 1 if there are more children
31040 available outside the varobj's update range.
31043 This attribute will be present and have the value @samp{1} if the
31044 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31045 then this attribute will not be present.
31048 If new children were added to a dynamic varobj within the selected
31049 update range (as set by @code{-var-set-update-range}), then they will
31050 be listed in this attribute.
31053 @subsubheading Example
31060 -var-update --all-values var1
31061 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31062 type_changed="false"@}]
31066 @subheading The @code{-var-set-frozen} Command
31067 @findex -var-set-frozen
31068 @anchor{-var-set-frozen}
31070 @subsubheading Synopsis
31073 -var-set-frozen @var{name} @var{flag}
31076 Set the frozenness flag on the variable object @var{name}. The
31077 @var{flag} parameter should be either @samp{1} to make the variable
31078 frozen or @samp{0} to make it unfrozen. If a variable object is
31079 frozen, then neither itself, nor any of its children, are
31080 implicitly updated by @code{-var-update} of
31081 a parent variable or by @code{-var-update *}. Only
31082 @code{-var-update} of the variable itself will update its value and
31083 values of its children. After a variable object is unfrozen, it is
31084 implicitly updated by all subsequent @code{-var-update} operations.
31085 Unfreezing a variable does not update it, only subsequent
31086 @code{-var-update} does.
31088 @subsubheading Example
31092 -var-set-frozen V 1
31097 @subheading The @code{-var-set-update-range} command
31098 @findex -var-set-update-range
31099 @anchor{-var-set-update-range}
31101 @subsubheading Synopsis
31104 -var-set-update-range @var{name} @var{from} @var{to}
31107 Set the range of children to be returned by future invocations of
31108 @code{-var-update}.
31110 @var{from} and @var{to} indicate the range of children to report. If
31111 @var{from} or @var{to} is less than zero, the range is reset and all
31112 children will be reported. Otherwise, children starting at @var{from}
31113 (zero-based) and up to and excluding @var{to} will be reported.
31115 @subsubheading Example
31119 -var-set-update-range V 1 2
31123 @subheading The @code{-var-set-visualizer} command
31124 @findex -var-set-visualizer
31125 @anchor{-var-set-visualizer}
31127 @subsubheading Synopsis
31130 -var-set-visualizer @var{name} @var{visualizer}
31133 Set a visualizer for the variable object @var{name}.
31135 @var{visualizer} is the visualizer to use. The special value
31136 @samp{None} means to disable any visualizer in use.
31138 If not @samp{None}, @var{visualizer} must be a Python expression.
31139 This expression must evaluate to a callable object which accepts a
31140 single argument. @value{GDBN} will call this object with the value of
31141 the varobj @var{name} as an argument (this is done so that the same
31142 Python pretty-printing code can be used for both the CLI and MI).
31143 When called, this object must return an object which conforms to the
31144 pretty-printing interface (@pxref{Pretty Printing API}).
31146 The pre-defined function @code{gdb.default_visualizer} may be used to
31147 select a visualizer by following the built-in process
31148 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31149 a varobj is created, and so ordinarily is not needed.
31151 This feature is only available if Python support is enabled. The MI
31152 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31153 can be used to check this.
31155 @subsubheading Example
31157 Resetting the visualizer:
31161 -var-set-visualizer V None
31165 Reselecting the default (type-based) visualizer:
31169 -var-set-visualizer V gdb.default_visualizer
31173 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31174 can be used to instantiate this class for a varobj:
31178 -var-set-visualizer V "lambda val: SomeClass()"
31182 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31183 @node GDB/MI Data Manipulation
31184 @section @sc{gdb/mi} Data Manipulation
31186 @cindex data manipulation, in @sc{gdb/mi}
31187 @cindex @sc{gdb/mi}, data manipulation
31188 This section describes the @sc{gdb/mi} commands that manipulate data:
31189 examine memory and registers, evaluate expressions, etc.
31191 @c REMOVED FROM THE INTERFACE.
31192 @c @subheading -data-assign
31193 @c Change the value of a program variable. Plenty of side effects.
31194 @c @subsubheading GDB Command
31196 @c @subsubheading Example
31199 @subheading The @code{-data-disassemble} Command
31200 @findex -data-disassemble
31202 @subsubheading Synopsis
31206 [ -s @var{start-addr} -e @var{end-addr} ]
31207 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31215 @item @var{start-addr}
31216 is the beginning address (or @code{$pc})
31217 @item @var{end-addr}
31219 @item @var{filename}
31220 is the name of the file to disassemble
31221 @item @var{linenum}
31222 is the line number to disassemble around
31224 is the number of disassembly lines to be produced. If it is -1,
31225 the whole function will be disassembled, in case no @var{end-addr} is
31226 specified. If @var{end-addr} is specified as a non-zero value, and
31227 @var{lines} is lower than the number of disassembly lines between
31228 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31229 displayed; if @var{lines} is higher than the number of lines between
31230 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31233 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31234 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31235 mixed source and disassembly with raw opcodes).
31238 @subsubheading Result
31240 The result of the @code{-data-disassemble} command will be a list named
31241 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31242 used with the @code{-data-disassemble} command.
31244 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31249 The address at which this instruction was disassembled.
31252 The name of the function this instruction is within.
31255 The decimal offset in bytes from the start of @samp{func-name}.
31258 The text disassembly for this @samp{address}.
31261 This field is only present for mode 2. This contains the raw opcode
31262 bytes for the @samp{inst} field.
31266 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31267 @samp{src_and_asm_line}, each of which has the following fields:
31271 The line number within @samp{file}.
31274 The file name from the compilation unit. This might be an absolute
31275 file name or a relative file name depending on the compile command
31279 Absolute file name of @samp{file}. It is converted to a canonical form
31280 using the source file search path
31281 (@pxref{Source Path, ,Specifying Source Directories})
31282 and after resolving all the symbolic links.
31284 If the source file is not found this field will contain the path as
31285 present in the debug information.
31287 @item line_asm_insn
31288 This is a list of tuples containing the disassembly for @samp{line} in
31289 @samp{file}. The fields of each tuple are the same as for
31290 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31291 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31296 Note that whatever included in the @samp{inst} field, is not
31297 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31300 @subsubheading @value{GDBN} Command
31302 The corresponding @value{GDBN} command is @samp{disassemble}.
31304 @subsubheading Example
31306 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31310 -data-disassemble -s $pc -e "$pc + 20" -- 0
31313 @{address="0x000107c0",func-name="main",offset="4",
31314 inst="mov 2, %o0"@},
31315 @{address="0x000107c4",func-name="main",offset="8",
31316 inst="sethi %hi(0x11800), %o2"@},
31317 @{address="0x000107c8",func-name="main",offset="12",
31318 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31319 @{address="0x000107cc",func-name="main",offset="16",
31320 inst="sethi %hi(0x11800), %o2"@},
31321 @{address="0x000107d0",func-name="main",offset="20",
31322 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31326 Disassemble the whole @code{main} function. Line 32 is part of
31330 -data-disassemble -f basics.c -l 32 -- 0
31332 @{address="0x000107bc",func-name="main",offset="0",
31333 inst="save %sp, -112, %sp"@},
31334 @{address="0x000107c0",func-name="main",offset="4",
31335 inst="mov 2, %o0"@},
31336 @{address="0x000107c4",func-name="main",offset="8",
31337 inst="sethi %hi(0x11800), %o2"@},
31339 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31340 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31344 Disassemble 3 instructions from the start of @code{main}:
31348 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31350 @{address="0x000107bc",func-name="main",offset="0",
31351 inst="save %sp, -112, %sp"@},
31352 @{address="0x000107c0",func-name="main",offset="4",
31353 inst="mov 2, %o0"@},
31354 @{address="0x000107c4",func-name="main",offset="8",
31355 inst="sethi %hi(0x11800), %o2"@}]
31359 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31363 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31365 src_and_asm_line=@{line="31",
31366 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31367 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31368 line_asm_insn=[@{address="0x000107bc",
31369 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31370 src_and_asm_line=@{line="32",
31371 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31372 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31373 line_asm_insn=[@{address="0x000107c0",
31374 func-name="main",offset="4",inst="mov 2, %o0"@},
31375 @{address="0x000107c4",func-name="main",offset="8",
31376 inst="sethi %hi(0x11800), %o2"@}]@}]
31381 @subheading The @code{-data-evaluate-expression} Command
31382 @findex -data-evaluate-expression
31384 @subsubheading Synopsis
31387 -data-evaluate-expression @var{expr}
31390 Evaluate @var{expr} as an expression. The expression could contain an
31391 inferior function call. The function call will execute synchronously.
31392 If the expression contains spaces, it must be enclosed in double quotes.
31394 @subsubheading @value{GDBN} Command
31396 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31397 @samp{call}. In @code{gdbtk} only, there's a corresponding
31398 @samp{gdb_eval} command.
31400 @subsubheading Example
31402 In the following example, the numbers that precede the commands are the
31403 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31404 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31408 211-data-evaluate-expression A
31411 311-data-evaluate-expression &A
31412 311^done,value="0xefffeb7c"
31414 411-data-evaluate-expression A+3
31417 511-data-evaluate-expression "A + 3"
31423 @subheading The @code{-data-list-changed-registers} Command
31424 @findex -data-list-changed-registers
31426 @subsubheading Synopsis
31429 -data-list-changed-registers
31432 Display a list of the registers that have changed.
31434 @subsubheading @value{GDBN} Command
31436 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31437 has the corresponding command @samp{gdb_changed_register_list}.
31439 @subsubheading Example
31441 On a PPC MBX board:
31449 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31450 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31453 -data-list-changed-registers
31454 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31455 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31456 "24","25","26","27","28","30","31","64","65","66","67","69"]
31461 @subheading The @code{-data-list-register-names} Command
31462 @findex -data-list-register-names
31464 @subsubheading Synopsis
31467 -data-list-register-names [ ( @var{regno} )+ ]
31470 Show a list of register names for the current target. If no arguments
31471 are given, it shows a list of the names of all the registers. If
31472 integer numbers are given as arguments, it will print a list of the
31473 names of the registers corresponding to the arguments. To ensure
31474 consistency between a register name and its number, the output list may
31475 include empty register names.
31477 @subsubheading @value{GDBN} Command
31479 @value{GDBN} does not have a command which corresponds to
31480 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31481 corresponding command @samp{gdb_regnames}.
31483 @subsubheading Example
31485 For the PPC MBX board:
31488 -data-list-register-names
31489 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31490 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31491 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31492 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31493 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31494 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31495 "", "pc","ps","cr","lr","ctr","xer"]
31497 -data-list-register-names 1 2 3
31498 ^done,register-names=["r1","r2","r3"]
31502 @subheading The @code{-data-list-register-values} Command
31503 @findex -data-list-register-values
31505 @subsubheading Synopsis
31508 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31511 Display the registers' contents. @var{fmt} is the format according to
31512 which the registers' contents are to be returned, followed by an optional
31513 list of numbers specifying the registers to display. A missing list of
31514 numbers indicates that the contents of all the registers must be returned.
31516 Allowed formats for @var{fmt} are:
31533 @subsubheading @value{GDBN} Command
31535 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31536 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31538 @subsubheading Example
31540 For a PPC MBX board (note: line breaks are for readability only, they
31541 don't appear in the actual output):
31545 -data-list-register-values r 64 65
31546 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31547 @{number="65",value="0x00029002"@}]
31549 -data-list-register-values x
31550 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31551 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31552 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31553 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31554 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31555 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31556 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31557 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31558 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31559 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31560 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31561 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31562 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31563 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31564 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31565 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31566 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31567 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31568 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31569 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31570 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31571 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31572 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31573 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31574 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31575 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31576 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31577 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31578 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31579 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31580 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31581 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31582 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31583 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31584 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31585 @{number="69",value="0x20002b03"@}]
31590 @subheading The @code{-data-read-memory} Command
31591 @findex -data-read-memory
31593 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31595 @subsubheading Synopsis
31598 -data-read-memory [ -o @var{byte-offset} ]
31599 @var{address} @var{word-format} @var{word-size}
31600 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31607 @item @var{address}
31608 An expression specifying the address of the first memory word to be
31609 read. Complex expressions containing embedded white space should be
31610 quoted using the C convention.
31612 @item @var{word-format}
31613 The format to be used to print the memory words. The notation is the
31614 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31617 @item @var{word-size}
31618 The size of each memory word in bytes.
31620 @item @var{nr-rows}
31621 The number of rows in the output table.
31623 @item @var{nr-cols}
31624 The number of columns in the output table.
31627 If present, indicates that each row should include an @sc{ascii} dump. The
31628 value of @var{aschar} is used as a padding character when a byte is not a
31629 member of the printable @sc{ascii} character set (printable @sc{ascii}
31630 characters are those whose code is between 32 and 126, inclusively).
31632 @item @var{byte-offset}
31633 An offset to add to the @var{address} before fetching memory.
31636 This command displays memory contents as a table of @var{nr-rows} by
31637 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31638 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31639 (returned as @samp{total-bytes}). Should less than the requested number
31640 of bytes be returned by the target, the missing words are identified
31641 using @samp{N/A}. The number of bytes read from the target is returned
31642 in @samp{nr-bytes} and the starting address used to read memory in
31645 The address of the next/previous row or page is available in
31646 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31649 @subsubheading @value{GDBN} Command
31651 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31652 @samp{gdb_get_mem} memory read command.
31654 @subsubheading Example
31656 Read six bytes of memory starting at @code{bytes+6} but then offset by
31657 @code{-6} bytes. Format as three rows of two columns. One byte per
31658 word. Display each word in hex.
31662 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31663 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31664 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31665 prev-page="0x0000138a",memory=[
31666 @{addr="0x00001390",data=["0x00","0x01"]@},
31667 @{addr="0x00001392",data=["0x02","0x03"]@},
31668 @{addr="0x00001394",data=["0x04","0x05"]@}]
31672 Read two bytes of memory starting at address @code{shorts + 64} and
31673 display as a single word formatted in decimal.
31677 5-data-read-memory shorts+64 d 2 1 1
31678 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31679 next-row="0x00001512",prev-row="0x0000150e",
31680 next-page="0x00001512",prev-page="0x0000150e",memory=[
31681 @{addr="0x00001510",data=["128"]@}]
31685 Read thirty two bytes of memory starting at @code{bytes+16} and format
31686 as eight rows of four columns. Include a string encoding with @samp{x}
31687 used as the non-printable character.
31691 4-data-read-memory bytes+16 x 1 8 4 x
31692 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31693 next-row="0x000013c0",prev-row="0x0000139c",
31694 next-page="0x000013c0",prev-page="0x00001380",memory=[
31695 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31696 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31697 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31698 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31699 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31700 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31701 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31702 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31706 @subheading The @code{-data-read-memory-bytes} Command
31707 @findex -data-read-memory-bytes
31709 @subsubheading Synopsis
31712 -data-read-memory-bytes [ -o @var{byte-offset} ]
31713 @var{address} @var{count}
31720 @item @var{address}
31721 An expression specifying the address of the first memory word to be
31722 read. Complex expressions containing embedded white space should be
31723 quoted using the C convention.
31726 The number of bytes to read. This should be an integer literal.
31728 @item @var{byte-offset}
31729 The offsets in bytes relative to @var{address} at which to start
31730 reading. This should be an integer literal. This option is provided
31731 so that a frontend is not required to first evaluate address and then
31732 perform address arithmetics itself.
31736 This command attempts to read all accessible memory regions in the
31737 specified range. First, all regions marked as unreadable in the memory
31738 map (if one is defined) will be skipped. @xref{Memory Region
31739 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31740 regions. For each one, if reading full region results in an errors,
31741 @value{GDBN} will try to read a subset of the region.
31743 In general, every single byte in the region may be readable or not,
31744 and the only way to read every readable byte is to try a read at
31745 every address, which is not practical. Therefore, @value{GDBN} will
31746 attempt to read all accessible bytes at either beginning or the end
31747 of the region, using a binary division scheme. This heuristic works
31748 well for reading accross a memory map boundary. Note that if a region
31749 has a readable range that is neither at the beginning or the end,
31750 @value{GDBN} will not read it.
31752 The result record (@pxref{GDB/MI Result Records}) that is output of
31753 the command includes a field named @samp{memory} whose content is a
31754 list of tuples. Each tuple represent a successfully read memory block
31755 and has the following fields:
31759 The start address of the memory block, as hexadecimal literal.
31762 The end address of the memory block, as hexadecimal literal.
31765 The offset of the memory block, as hexadecimal literal, relative to
31766 the start address passed to @code{-data-read-memory-bytes}.
31769 The contents of the memory block, in hex.
31775 @subsubheading @value{GDBN} Command
31777 The corresponding @value{GDBN} command is @samp{x}.
31779 @subsubheading Example
31783 -data-read-memory-bytes &a 10
31784 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31786 contents="01000000020000000300"@}]
31791 @subheading The @code{-data-write-memory-bytes} Command
31792 @findex -data-write-memory-bytes
31794 @subsubheading Synopsis
31797 -data-write-memory-bytes @var{address} @var{contents}
31798 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31805 @item @var{address}
31806 An expression specifying the address of the first memory word to be
31807 read. Complex expressions containing embedded white space should be
31808 quoted using the C convention.
31810 @item @var{contents}
31811 The hex-encoded bytes to write.
31814 Optional argument indicating the number of bytes to be written. If @var{count}
31815 is greater than @var{contents}' length, @value{GDBN} will repeatedly
31816 write @var{contents} until it fills @var{count} bytes.
31820 @subsubheading @value{GDBN} Command
31822 There's no corresponding @value{GDBN} command.
31824 @subsubheading Example
31828 -data-write-memory-bytes &a "aabbccdd"
31835 -data-write-memory-bytes &a "aabbccdd" 16e
31840 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31841 @node GDB/MI Tracepoint Commands
31842 @section @sc{gdb/mi} Tracepoint Commands
31844 The commands defined in this section implement MI support for
31845 tracepoints. For detailed introduction, see @ref{Tracepoints}.
31847 @subheading The @code{-trace-find} Command
31848 @findex -trace-find
31850 @subsubheading Synopsis
31853 -trace-find @var{mode} [@var{parameters}@dots{}]
31856 Find a trace frame using criteria defined by @var{mode} and
31857 @var{parameters}. The following table lists permissible
31858 modes and their parameters. For details of operation, see @ref{tfind}.
31863 No parameters are required. Stops examining trace frames.
31866 An integer is required as parameter. Selects tracepoint frame with
31869 @item tracepoint-number
31870 An integer is required as parameter. Finds next
31871 trace frame that corresponds to tracepoint with the specified number.
31874 An address is required as parameter. Finds
31875 next trace frame that corresponds to any tracepoint at the specified
31878 @item pc-inside-range
31879 Two addresses are required as parameters. Finds next trace
31880 frame that corresponds to a tracepoint at an address inside the
31881 specified range. Both bounds are considered to be inside the range.
31883 @item pc-outside-range
31884 Two addresses are required as parameters. Finds
31885 next trace frame that corresponds to a tracepoint at an address outside
31886 the specified range. Both bounds are considered to be inside the range.
31889 Line specification is required as parameter. @xref{Specify Location}.
31890 Finds next trace frame that corresponds to a tracepoint at
31891 the specified location.
31895 If @samp{none} was passed as @var{mode}, the response does not
31896 have fields. Otherwise, the response may have the following fields:
31900 This field has either @samp{0} or @samp{1} as the value, depending
31901 on whether a matching tracepoint was found.
31904 The index of the found traceframe. This field is present iff
31905 the @samp{found} field has value of @samp{1}.
31908 The index of the found tracepoint. This field is present iff
31909 the @samp{found} field has value of @samp{1}.
31912 The information about the frame corresponding to the found trace
31913 frame. This field is present only if a trace frame was found.
31914 @xref{GDB/MI Frame Information}, for description of this field.
31918 @subsubheading @value{GDBN} Command
31920 The corresponding @value{GDBN} command is @samp{tfind}.
31922 @subheading -trace-define-variable
31923 @findex -trace-define-variable
31925 @subsubheading Synopsis
31928 -trace-define-variable @var{name} [ @var{value} ]
31931 Create trace variable @var{name} if it does not exist. If
31932 @var{value} is specified, sets the initial value of the specified
31933 trace variable to that value. Note that the @var{name} should start
31934 with the @samp{$} character.
31936 @subsubheading @value{GDBN} Command
31938 The corresponding @value{GDBN} command is @samp{tvariable}.
31940 @subheading -trace-list-variables
31941 @findex -trace-list-variables
31943 @subsubheading Synopsis
31946 -trace-list-variables
31949 Return a table of all defined trace variables. Each element of the
31950 table has the following fields:
31954 The name of the trace variable. This field is always present.
31957 The initial value. This is a 64-bit signed integer. This
31958 field is always present.
31961 The value the trace variable has at the moment. This is a 64-bit
31962 signed integer. This field is absent iff current value is
31963 not defined, for example if the trace was never run, or is
31968 @subsubheading @value{GDBN} Command
31970 The corresponding @value{GDBN} command is @samp{tvariables}.
31972 @subsubheading Example
31976 -trace-list-variables
31977 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
31978 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
31979 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
31980 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
31981 body=[variable=@{name="$trace_timestamp",initial="0"@}
31982 variable=@{name="$foo",initial="10",current="15"@}]@}
31986 @subheading -trace-save
31987 @findex -trace-save
31989 @subsubheading Synopsis
31992 -trace-save [-r ] @var{filename}
31995 Saves the collected trace data to @var{filename}. Without the
31996 @samp{-r} option, the data is downloaded from the target and saved
31997 in a local file. With the @samp{-r} option the target is asked
31998 to perform the save.
32000 @subsubheading @value{GDBN} Command
32002 The corresponding @value{GDBN} command is @samp{tsave}.
32005 @subheading -trace-start
32006 @findex -trace-start
32008 @subsubheading Synopsis
32014 Starts a tracing experiments. The result of this command does not
32017 @subsubheading @value{GDBN} Command
32019 The corresponding @value{GDBN} command is @samp{tstart}.
32021 @subheading -trace-status
32022 @findex -trace-status
32024 @subsubheading Synopsis
32030 Obtains the status of a tracing experiment. The result may include
32031 the following fields:
32036 May have a value of either @samp{0}, when no tracing operations are
32037 supported, @samp{1}, when all tracing operations are supported, or
32038 @samp{file} when examining trace file. In the latter case, examining
32039 of trace frame is possible but new tracing experiement cannot be
32040 started. This field is always present.
32043 May have a value of either @samp{0} or @samp{1} depending on whether
32044 tracing experiement is in progress on target. This field is present
32045 if @samp{supported} field is not @samp{0}.
32048 Report the reason why the tracing was stopped last time. This field
32049 may be absent iff tracing was never stopped on target yet. The
32050 value of @samp{request} means the tracing was stopped as result of
32051 the @code{-trace-stop} command. The value of @samp{overflow} means
32052 the tracing buffer is full. The value of @samp{disconnection} means
32053 tracing was automatically stopped when @value{GDBN} has disconnected.
32054 The value of @samp{passcount} means tracing was stopped when a
32055 tracepoint was passed a maximal number of times for that tracepoint.
32056 This field is present if @samp{supported} field is not @samp{0}.
32058 @item stopping-tracepoint
32059 The number of tracepoint whose passcount as exceeded. This field is
32060 present iff the @samp{stop-reason} field has the value of
32064 @itemx frames-created
32065 The @samp{frames} field is a count of the total number of trace frames
32066 in the trace buffer, while @samp{frames-created} is the total created
32067 during the run, including ones that were discarded, such as when a
32068 circular trace buffer filled up. Both fields are optional.
32072 These fields tell the current size of the tracing buffer and the
32073 remaining space. These fields are optional.
32076 The value of the circular trace buffer flag. @code{1} means that the
32077 trace buffer is circular and old trace frames will be discarded if
32078 necessary to make room, @code{0} means that the trace buffer is linear
32082 The value of the disconnected tracing flag. @code{1} means that
32083 tracing will continue after @value{GDBN} disconnects, @code{0} means
32084 that the trace run will stop.
32087 The filename of the trace file being examined. This field is
32088 optional, and only present when examining a trace file.
32092 @subsubheading @value{GDBN} Command
32094 The corresponding @value{GDBN} command is @samp{tstatus}.
32096 @subheading -trace-stop
32097 @findex -trace-stop
32099 @subsubheading Synopsis
32105 Stops a tracing experiment. The result of this command has the same
32106 fields as @code{-trace-status}, except that the @samp{supported} and
32107 @samp{running} fields are not output.
32109 @subsubheading @value{GDBN} Command
32111 The corresponding @value{GDBN} command is @samp{tstop}.
32114 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32115 @node GDB/MI Symbol Query
32116 @section @sc{gdb/mi} Symbol Query Commands
32120 @subheading The @code{-symbol-info-address} Command
32121 @findex -symbol-info-address
32123 @subsubheading Synopsis
32126 -symbol-info-address @var{symbol}
32129 Describe where @var{symbol} is stored.
32131 @subsubheading @value{GDBN} Command
32133 The corresponding @value{GDBN} command is @samp{info address}.
32135 @subsubheading Example
32139 @subheading The @code{-symbol-info-file} Command
32140 @findex -symbol-info-file
32142 @subsubheading Synopsis
32148 Show the file for the symbol.
32150 @subsubheading @value{GDBN} Command
32152 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32153 @samp{gdb_find_file}.
32155 @subsubheading Example
32159 @subheading The @code{-symbol-info-function} Command
32160 @findex -symbol-info-function
32162 @subsubheading Synopsis
32165 -symbol-info-function
32168 Show which function the symbol lives in.
32170 @subsubheading @value{GDBN} Command
32172 @samp{gdb_get_function} in @code{gdbtk}.
32174 @subsubheading Example
32178 @subheading The @code{-symbol-info-line} Command
32179 @findex -symbol-info-line
32181 @subsubheading Synopsis
32187 Show the core addresses of the code for a source line.
32189 @subsubheading @value{GDBN} Command
32191 The corresponding @value{GDBN} command is @samp{info line}.
32192 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32194 @subsubheading Example
32198 @subheading The @code{-symbol-info-symbol} Command
32199 @findex -symbol-info-symbol
32201 @subsubheading Synopsis
32204 -symbol-info-symbol @var{addr}
32207 Describe what symbol is at location @var{addr}.
32209 @subsubheading @value{GDBN} Command
32211 The corresponding @value{GDBN} command is @samp{info symbol}.
32213 @subsubheading Example
32217 @subheading The @code{-symbol-list-functions} Command
32218 @findex -symbol-list-functions
32220 @subsubheading Synopsis
32223 -symbol-list-functions
32226 List the functions in the executable.
32228 @subsubheading @value{GDBN} Command
32230 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32231 @samp{gdb_search} in @code{gdbtk}.
32233 @subsubheading Example
32238 @subheading The @code{-symbol-list-lines} Command
32239 @findex -symbol-list-lines
32241 @subsubheading Synopsis
32244 -symbol-list-lines @var{filename}
32247 Print the list of lines that contain code and their associated program
32248 addresses for the given source filename. The entries are sorted in
32249 ascending PC order.
32251 @subsubheading @value{GDBN} Command
32253 There is no corresponding @value{GDBN} command.
32255 @subsubheading Example
32258 -symbol-list-lines basics.c
32259 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32265 @subheading The @code{-symbol-list-types} Command
32266 @findex -symbol-list-types
32268 @subsubheading Synopsis
32274 List all the type names.
32276 @subsubheading @value{GDBN} Command
32278 The corresponding commands are @samp{info types} in @value{GDBN},
32279 @samp{gdb_search} in @code{gdbtk}.
32281 @subsubheading Example
32285 @subheading The @code{-symbol-list-variables} Command
32286 @findex -symbol-list-variables
32288 @subsubheading Synopsis
32291 -symbol-list-variables
32294 List all the global and static variable names.
32296 @subsubheading @value{GDBN} Command
32298 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32300 @subsubheading Example
32304 @subheading The @code{-symbol-locate} Command
32305 @findex -symbol-locate
32307 @subsubheading Synopsis
32313 @subsubheading @value{GDBN} Command
32315 @samp{gdb_loc} in @code{gdbtk}.
32317 @subsubheading Example
32321 @subheading The @code{-symbol-type} Command
32322 @findex -symbol-type
32324 @subsubheading Synopsis
32327 -symbol-type @var{variable}
32330 Show type of @var{variable}.
32332 @subsubheading @value{GDBN} Command
32334 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32335 @samp{gdb_obj_variable}.
32337 @subsubheading Example
32342 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32343 @node GDB/MI File Commands
32344 @section @sc{gdb/mi} File Commands
32346 This section describes the GDB/MI commands to specify executable file names
32347 and to read in and obtain symbol table information.
32349 @subheading The @code{-file-exec-and-symbols} Command
32350 @findex -file-exec-and-symbols
32352 @subsubheading Synopsis
32355 -file-exec-and-symbols @var{file}
32358 Specify the executable file to be debugged. This file is the one from
32359 which the symbol table is also read. If no file is specified, the
32360 command clears the executable and symbol information. If breakpoints
32361 are set when using this command with no arguments, @value{GDBN} will produce
32362 error messages. Otherwise, no output is produced, except a completion
32365 @subsubheading @value{GDBN} Command
32367 The corresponding @value{GDBN} command is @samp{file}.
32369 @subsubheading Example
32373 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32379 @subheading The @code{-file-exec-file} Command
32380 @findex -file-exec-file
32382 @subsubheading Synopsis
32385 -file-exec-file @var{file}
32388 Specify the executable file to be debugged. Unlike
32389 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32390 from this file. If used without argument, @value{GDBN} clears the information
32391 about the executable file. No output is produced, except a completion
32394 @subsubheading @value{GDBN} Command
32396 The corresponding @value{GDBN} command is @samp{exec-file}.
32398 @subsubheading Example
32402 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32409 @subheading The @code{-file-list-exec-sections} Command
32410 @findex -file-list-exec-sections
32412 @subsubheading Synopsis
32415 -file-list-exec-sections
32418 List the sections of the current executable file.
32420 @subsubheading @value{GDBN} Command
32422 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32423 information as this command. @code{gdbtk} has a corresponding command
32424 @samp{gdb_load_info}.
32426 @subsubheading Example
32431 @subheading The @code{-file-list-exec-source-file} Command
32432 @findex -file-list-exec-source-file
32434 @subsubheading Synopsis
32437 -file-list-exec-source-file
32440 List the line number, the current source file, and the absolute path
32441 to the current source file for the current executable. The macro
32442 information field has a value of @samp{1} or @samp{0} depending on
32443 whether or not the file includes preprocessor macro information.
32445 @subsubheading @value{GDBN} Command
32447 The @value{GDBN} equivalent is @samp{info source}
32449 @subsubheading Example
32453 123-file-list-exec-source-file
32454 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32459 @subheading The @code{-file-list-exec-source-files} Command
32460 @findex -file-list-exec-source-files
32462 @subsubheading Synopsis
32465 -file-list-exec-source-files
32468 List the source files for the current executable.
32470 It will always output both the filename and fullname (absolute file
32471 name) of a source file.
32473 @subsubheading @value{GDBN} Command
32475 The @value{GDBN} equivalent is @samp{info sources}.
32476 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32478 @subsubheading Example
32481 -file-list-exec-source-files
32483 @{file=foo.c,fullname=/home/foo.c@},
32484 @{file=/home/bar.c,fullname=/home/bar.c@},
32485 @{file=gdb_could_not_find_fullpath.c@}]
32490 @subheading The @code{-file-list-shared-libraries} Command
32491 @findex -file-list-shared-libraries
32493 @subsubheading Synopsis
32496 -file-list-shared-libraries
32499 List the shared libraries in the program.
32501 @subsubheading @value{GDBN} Command
32503 The corresponding @value{GDBN} command is @samp{info shared}.
32505 @subsubheading Example
32509 @subheading The @code{-file-list-symbol-files} Command
32510 @findex -file-list-symbol-files
32512 @subsubheading Synopsis
32515 -file-list-symbol-files
32520 @subsubheading @value{GDBN} Command
32522 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32524 @subsubheading Example
32529 @subheading The @code{-file-symbol-file} Command
32530 @findex -file-symbol-file
32532 @subsubheading Synopsis
32535 -file-symbol-file @var{file}
32538 Read symbol table info from the specified @var{file} argument. When
32539 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32540 produced, except for a completion notification.
32542 @subsubheading @value{GDBN} Command
32544 The corresponding @value{GDBN} command is @samp{symbol-file}.
32546 @subsubheading Example
32550 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32556 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32557 @node GDB/MI Memory Overlay Commands
32558 @section @sc{gdb/mi} Memory Overlay Commands
32560 The memory overlay commands are not implemented.
32562 @c @subheading -overlay-auto
32564 @c @subheading -overlay-list-mapping-state
32566 @c @subheading -overlay-list-overlays
32568 @c @subheading -overlay-map
32570 @c @subheading -overlay-off
32572 @c @subheading -overlay-on
32574 @c @subheading -overlay-unmap
32576 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32577 @node GDB/MI Signal Handling Commands
32578 @section @sc{gdb/mi} Signal Handling Commands
32580 Signal handling commands are not implemented.
32582 @c @subheading -signal-handle
32584 @c @subheading -signal-list-handle-actions
32586 @c @subheading -signal-list-signal-types
32590 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32591 @node GDB/MI Target Manipulation
32592 @section @sc{gdb/mi} Target Manipulation Commands
32595 @subheading The @code{-target-attach} Command
32596 @findex -target-attach
32598 @subsubheading Synopsis
32601 -target-attach @var{pid} | @var{gid} | @var{file}
32604 Attach to a process @var{pid} or a file @var{file} outside of
32605 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32606 group, the id previously returned by
32607 @samp{-list-thread-groups --available} must be used.
32609 @subsubheading @value{GDBN} Command
32611 The corresponding @value{GDBN} command is @samp{attach}.
32613 @subsubheading Example
32617 =thread-created,id="1"
32618 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32624 @subheading The @code{-target-compare-sections} Command
32625 @findex -target-compare-sections
32627 @subsubheading Synopsis
32630 -target-compare-sections [ @var{section} ]
32633 Compare data of section @var{section} on target to the exec file.
32634 Without the argument, all sections are compared.
32636 @subsubheading @value{GDBN} Command
32638 The @value{GDBN} equivalent is @samp{compare-sections}.
32640 @subsubheading Example
32645 @subheading The @code{-target-detach} Command
32646 @findex -target-detach
32648 @subsubheading Synopsis
32651 -target-detach [ @var{pid} | @var{gid} ]
32654 Detach from the remote target which normally resumes its execution.
32655 If either @var{pid} or @var{gid} is specified, detaches from either
32656 the specified process, or specified thread group. There's no output.
32658 @subsubheading @value{GDBN} Command
32660 The corresponding @value{GDBN} command is @samp{detach}.
32662 @subsubheading Example
32672 @subheading The @code{-target-disconnect} Command
32673 @findex -target-disconnect
32675 @subsubheading Synopsis
32681 Disconnect from the remote target. There's no output and the target is
32682 generally not resumed.
32684 @subsubheading @value{GDBN} Command
32686 The corresponding @value{GDBN} command is @samp{disconnect}.
32688 @subsubheading Example
32698 @subheading The @code{-target-download} Command
32699 @findex -target-download
32701 @subsubheading Synopsis
32707 Loads the executable onto the remote target.
32708 It prints out an update message every half second, which includes the fields:
32712 The name of the section.
32714 The size of what has been sent so far for that section.
32716 The size of the section.
32718 The total size of what was sent so far (the current and the previous sections).
32720 The size of the overall executable to download.
32724 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32725 @sc{gdb/mi} Output Syntax}).
32727 In addition, it prints the name and size of the sections, as they are
32728 downloaded. These messages include the following fields:
32732 The name of the section.
32734 The size of the section.
32736 The size of the overall executable to download.
32740 At the end, a summary is printed.
32742 @subsubheading @value{GDBN} Command
32744 The corresponding @value{GDBN} command is @samp{load}.
32746 @subsubheading Example
32748 Note: each status message appears on a single line. Here the messages
32749 have been broken down so that they can fit onto a page.
32754 +download,@{section=".text",section-size="6668",total-size="9880"@}
32755 +download,@{section=".text",section-sent="512",section-size="6668",
32756 total-sent="512",total-size="9880"@}
32757 +download,@{section=".text",section-sent="1024",section-size="6668",
32758 total-sent="1024",total-size="9880"@}
32759 +download,@{section=".text",section-sent="1536",section-size="6668",
32760 total-sent="1536",total-size="9880"@}
32761 +download,@{section=".text",section-sent="2048",section-size="6668",
32762 total-sent="2048",total-size="9880"@}
32763 +download,@{section=".text",section-sent="2560",section-size="6668",
32764 total-sent="2560",total-size="9880"@}
32765 +download,@{section=".text",section-sent="3072",section-size="6668",
32766 total-sent="3072",total-size="9880"@}
32767 +download,@{section=".text",section-sent="3584",section-size="6668",
32768 total-sent="3584",total-size="9880"@}
32769 +download,@{section=".text",section-sent="4096",section-size="6668",
32770 total-sent="4096",total-size="9880"@}
32771 +download,@{section=".text",section-sent="4608",section-size="6668",
32772 total-sent="4608",total-size="9880"@}
32773 +download,@{section=".text",section-sent="5120",section-size="6668",
32774 total-sent="5120",total-size="9880"@}
32775 +download,@{section=".text",section-sent="5632",section-size="6668",
32776 total-sent="5632",total-size="9880"@}
32777 +download,@{section=".text",section-sent="6144",section-size="6668",
32778 total-sent="6144",total-size="9880"@}
32779 +download,@{section=".text",section-sent="6656",section-size="6668",
32780 total-sent="6656",total-size="9880"@}
32781 +download,@{section=".init",section-size="28",total-size="9880"@}
32782 +download,@{section=".fini",section-size="28",total-size="9880"@}
32783 +download,@{section=".data",section-size="3156",total-size="9880"@}
32784 +download,@{section=".data",section-sent="512",section-size="3156",
32785 total-sent="7236",total-size="9880"@}
32786 +download,@{section=".data",section-sent="1024",section-size="3156",
32787 total-sent="7748",total-size="9880"@}
32788 +download,@{section=".data",section-sent="1536",section-size="3156",
32789 total-sent="8260",total-size="9880"@}
32790 +download,@{section=".data",section-sent="2048",section-size="3156",
32791 total-sent="8772",total-size="9880"@}
32792 +download,@{section=".data",section-sent="2560",section-size="3156",
32793 total-sent="9284",total-size="9880"@}
32794 +download,@{section=".data",section-sent="3072",section-size="3156",
32795 total-sent="9796",total-size="9880"@}
32796 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32803 @subheading The @code{-target-exec-status} Command
32804 @findex -target-exec-status
32806 @subsubheading Synopsis
32809 -target-exec-status
32812 Provide information on the state of the target (whether it is running or
32813 not, for instance).
32815 @subsubheading @value{GDBN} Command
32817 There's no equivalent @value{GDBN} command.
32819 @subsubheading Example
32823 @subheading The @code{-target-list-available-targets} Command
32824 @findex -target-list-available-targets
32826 @subsubheading Synopsis
32829 -target-list-available-targets
32832 List the possible targets to connect to.
32834 @subsubheading @value{GDBN} Command
32836 The corresponding @value{GDBN} command is @samp{help target}.
32838 @subsubheading Example
32842 @subheading The @code{-target-list-current-targets} Command
32843 @findex -target-list-current-targets
32845 @subsubheading Synopsis
32848 -target-list-current-targets
32851 Describe the current target.
32853 @subsubheading @value{GDBN} Command
32855 The corresponding information is printed by @samp{info file} (among
32858 @subsubheading Example
32862 @subheading The @code{-target-list-parameters} Command
32863 @findex -target-list-parameters
32865 @subsubheading Synopsis
32868 -target-list-parameters
32874 @subsubheading @value{GDBN} Command
32878 @subsubheading Example
32882 @subheading The @code{-target-select} Command
32883 @findex -target-select
32885 @subsubheading Synopsis
32888 -target-select @var{type} @var{parameters @dots{}}
32891 Connect @value{GDBN} to the remote target. This command takes two args:
32895 The type of target, for instance @samp{remote}, etc.
32896 @item @var{parameters}
32897 Device names, host names and the like. @xref{Target Commands, ,
32898 Commands for Managing Targets}, for more details.
32901 The output is a connection notification, followed by the address at
32902 which the target program is, in the following form:
32905 ^connected,addr="@var{address}",func="@var{function name}",
32906 args=[@var{arg list}]
32909 @subsubheading @value{GDBN} Command
32911 The corresponding @value{GDBN} command is @samp{target}.
32913 @subsubheading Example
32917 -target-select remote /dev/ttya
32918 ^connected,addr="0xfe00a300",func="??",args=[]
32922 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32923 @node GDB/MI File Transfer Commands
32924 @section @sc{gdb/mi} File Transfer Commands
32927 @subheading The @code{-target-file-put} Command
32928 @findex -target-file-put
32930 @subsubheading Synopsis
32933 -target-file-put @var{hostfile} @var{targetfile}
32936 Copy file @var{hostfile} from the host system (the machine running
32937 @value{GDBN}) to @var{targetfile} on the target system.
32939 @subsubheading @value{GDBN} Command
32941 The corresponding @value{GDBN} command is @samp{remote put}.
32943 @subsubheading Example
32947 -target-file-put localfile remotefile
32953 @subheading The @code{-target-file-get} Command
32954 @findex -target-file-get
32956 @subsubheading Synopsis
32959 -target-file-get @var{targetfile} @var{hostfile}
32962 Copy file @var{targetfile} from the target system to @var{hostfile}
32963 on the host system.
32965 @subsubheading @value{GDBN} Command
32967 The corresponding @value{GDBN} command is @samp{remote get}.
32969 @subsubheading Example
32973 -target-file-get remotefile localfile
32979 @subheading The @code{-target-file-delete} Command
32980 @findex -target-file-delete
32982 @subsubheading Synopsis
32985 -target-file-delete @var{targetfile}
32988 Delete @var{targetfile} from the target system.
32990 @subsubheading @value{GDBN} Command
32992 The corresponding @value{GDBN} command is @samp{remote delete}.
32994 @subsubheading Example
32998 -target-file-delete remotefile
33004 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33005 @node GDB/MI Miscellaneous Commands
33006 @section Miscellaneous @sc{gdb/mi} Commands
33008 @c @subheading -gdb-complete
33010 @subheading The @code{-gdb-exit} Command
33013 @subsubheading Synopsis
33019 Exit @value{GDBN} immediately.
33021 @subsubheading @value{GDBN} Command
33023 Approximately corresponds to @samp{quit}.
33025 @subsubheading Example
33035 @subheading The @code{-exec-abort} Command
33036 @findex -exec-abort
33038 @subsubheading Synopsis
33044 Kill the inferior running program.
33046 @subsubheading @value{GDBN} Command
33048 The corresponding @value{GDBN} command is @samp{kill}.
33050 @subsubheading Example
33055 @subheading The @code{-gdb-set} Command
33058 @subsubheading Synopsis
33064 Set an internal @value{GDBN} variable.
33065 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33067 @subsubheading @value{GDBN} Command
33069 The corresponding @value{GDBN} command is @samp{set}.
33071 @subsubheading Example
33081 @subheading The @code{-gdb-show} Command
33084 @subsubheading Synopsis
33090 Show the current value of a @value{GDBN} variable.
33092 @subsubheading @value{GDBN} Command
33094 The corresponding @value{GDBN} command is @samp{show}.
33096 @subsubheading Example
33105 @c @subheading -gdb-source
33108 @subheading The @code{-gdb-version} Command
33109 @findex -gdb-version
33111 @subsubheading Synopsis
33117 Show version information for @value{GDBN}. Used mostly in testing.
33119 @subsubheading @value{GDBN} Command
33121 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33122 default shows this information when you start an interactive session.
33124 @subsubheading Example
33126 @c This example modifies the actual output from GDB to avoid overfull
33132 ~Copyright 2000 Free Software Foundation, Inc.
33133 ~GDB is free software, covered by the GNU General Public License, and
33134 ~you are welcome to change it and/or distribute copies of it under
33135 ~ certain conditions.
33136 ~Type "show copying" to see the conditions.
33137 ~There is absolutely no warranty for GDB. Type "show warranty" for
33139 ~This GDB was configured as
33140 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33145 @subheading The @code{-list-features} Command
33146 @findex -list-features
33148 Returns a list of particular features of the MI protocol that
33149 this version of gdb implements. A feature can be a command,
33150 or a new field in an output of some command, or even an
33151 important bugfix. While a frontend can sometimes detect presence
33152 of a feature at runtime, it is easier to perform detection at debugger
33155 The command returns a list of strings, with each string naming an
33156 available feature. Each returned string is just a name, it does not
33157 have any internal structure. The list of possible feature names
33163 (gdb) -list-features
33164 ^done,result=["feature1","feature2"]
33167 The current list of features is:
33170 @item frozen-varobjs
33171 Indicates support for the @code{-var-set-frozen} command, as well
33172 as possible presense of the @code{frozen} field in the output
33173 of @code{-varobj-create}.
33174 @item pending-breakpoints
33175 Indicates support for the @option{-f} option to the @code{-break-insert}
33178 Indicates Python scripting support, Python-based
33179 pretty-printing commands, and possible presence of the
33180 @samp{display_hint} field in the output of @code{-var-list-children}
33182 Indicates support for the @code{-thread-info} command.
33183 @item data-read-memory-bytes
33184 Indicates support for the @code{-data-read-memory-bytes} and the
33185 @code{-data-write-memory-bytes} commands.
33186 @item breakpoint-notifications
33187 Indicates that changes to breakpoints and breakpoints created via the
33188 CLI will be announced via async records.
33189 @item ada-task-info
33190 Indicates support for the @code{-ada-task-info} command.
33193 @subheading The @code{-list-target-features} Command
33194 @findex -list-target-features
33196 Returns a list of particular features that are supported by the
33197 target. Those features affect the permitted MI commands, but
33198 unlike the features reported by the @code{-list-features} command, the
33199 features depend on which target GDB is using at the moment. Whenever
33200 a target can change, due to commands such as @code{-target-select},
33201 @code{-target-attach} or @code{-exec-run}, the list of target features
33202 may change, and the frontend should obtain it again.
33206 (gdb) -list-features
33207 ^done,result=["async"]
33210 The current list of features is:
33214 Indicates that the target is capable of asynchronous command
33215 execution, which means that @value{GDBN} will accept further commands
33216 while the target is running.
33219 Indicates that the target is capable of reverse execution.
33220 @xref{Reverse Execution}, for more information.
33224 @subheading The @code{-list-thread-groups} Command
33225 @findex -list-thread-groups
33227 @subheading Synopsis
33230 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33233 Lists thread groups (@pxref{Thread groups}). When a single thread
33234 group is passed as the argument, lists the children of that group.
33235 When several thread group are passed, lists information about those
33236 thread groups. Without any parameters, lists information about all
33237 top-level thread groups.
33239 Normally, thread groups that are being debugged are reported.
33240 With the @samp{--available} option, @value{GDBN} reports thread groups
33241 available on the target.
33243 The output of this command may have either a @samp{threads} result or
33244 a @samp{groups} result. The @samp{thread} result has a list of tuples
33245 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33246 Information}). The @samp{groups} result has a list of tuples as value,
33247 each tuple describing a thread group. If top-level groups are
33248 requested (that is, no parameter is passed), or when several groups
33249 are passed, the output always has a @samp{groups} result. The format
33250 of the @samp{group} result is described below.
33252 To reduce the number of roundtrips it's possible to list thread groups
33253 together with their children, by passing the @samp{--recurse} option
33254 and the recursion depth. Presently, only recursion depth of 1 is
33255 permitted. If this option is present, then every reported thread group
33256 will also include its children, either as @samp{group} or
33257 @samp{threads} field.
33259 In general, any combination of option and parameters is permitted, with
33260 the following caveats:
33264 When a single thread group is passed, the output will typically
33265 be the @samp{threads} result. Because threads may not contain
33266 anything, the @samp{recurse} option will be ignored.
33269 When the @samp{--available} option is passed, limited information may
33270 be available. In particular, the list of threads of a process might
33271 be inaccessible. Further, specifying specific thread groups might
33272 not give any performance advantage over listing all thread groups.
33273 The frontend should assume that @samp{-list-thread-groups --available}
33274 is always an expensive operation and cache the results.
33278 The @samp{groups} result is a list of tuples, where each tuple may
33279 have the following fields:
33283 Identifier of the thread group. This field is always present.
33284 The identifier is an opaque string; frontends should not try to
33285 convert it to an integer, even though it might look like one.
33288 The type of the thread group. At present, only @samp{process} is a
33292 The target-specific process identifier. This field is only present
33293 for thread groups of type @samp{process} and only if the process exists.
33296 The number of children this thread group has. This field may be
33297 absent for an available thread group.
33300 This field has a list of tuples as value, each tuple describing a
33301 thread. It may be present if the @samp{--recurse} option is
33302 specified, and it's actually possible to obtain the threads.
33305 This field is a list of integers, each identifying a core that one
33306 thread of the group is running on. This field may be absent if
33307 such information is not available.
33310 The name of the executable file that corresponds to this thread group.
33311 The field is only present for thread groups of type @samp{process},
33312 and only if there is a corresponding executable file.
33316 @subheading Example
33320 -list-thread-groups
33321 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33322 -list-thread-groups 17
33323 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33324 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33325 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33326 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33327 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33328 -list-thread-groups --available
33329 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33330 -list-thread-groups --available --recurse 1
33331 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33332 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33333 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33334 -list-thread-groups --available --recurse 1 17 18
33335 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33336 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33337 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33340 @subheading The @code{-info-os} Command
33343 @subsubheading Synopsis
33346 -info-os [ @var{type} ]
33349 If no argument is supplied, the command returns a table of available
33350 operating-system-specific information types. If one of these types is
33351 supplied as an argument @var{type}, then the command returns a table
33352 of data of that type.
33354 The types of information available depend on the target operating
33357 @subsubheading @value{GDBN} Command
33359 The corresponding @value{GDBN} command is @samp{info os}.
33361 @subsubheading Example
33363 When run on a @sc{gnu}/Linux system, the output will look something
33369 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33370 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33371 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33372 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33373 body=[item=@{col0="processes",col1="Listing of all processes",
33374 col2="Processes"@},
33375 item=@{col0="procgroups",col1="Listing of all process groups",
33376 col2="Process groups"@},
33377 item=@{col0="threads",col1="Listing of all threads",
33379 item=@{col0="files",col1="Listing of all file descriptors",
33380 col2="File descriptors"@},
33381 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33383 item=@{col0="shm",col1="Listing of all shared-memory regions",
33384 col2="Shared-memory regions"@},
33385 item=@{col0="semaphores",col1="Listing of all semaphores",
33386 col2="Semaphores"@},
33387 item=@{col0="msg",col1="Listing of all message queues",
33388 col2="Message queues"@},
33389 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33390 col2="Kernel modules"@}]@}
33393 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33394 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33395 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33396 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33397 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33398 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33399 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33400 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33402 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33403 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33407 (Note that the MI output here includes a @code{"Title"} column that
33408 does not appear in command-line @code{info os}; this column is useful
33409 for MI clients that want to enumerate the types of data, such as in a
33410 popup menu, but is needless clutter on the command line, and
33411 @code{info os} omits it.)
33413 @subheading The @code{-add-inferior} Command
33414 @findex -add-inferior
33416 @subheading Synopsis
33422 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33423 inferior is not associated with any executable. Such association may
33424 be established with the @samp{-file-exec-and-symbols} command
33425 (@pxref{GDB/MI File Commands}). The command response has a single
33426 field, @samp{thread-group}, whose value is the identifier of the
33427 thread group corresponding to the new inferior.
33429 @subheading Example
33434 ^done,thread-group="i3"
33437 @subheading The @code{-interpreter-exec} Command
33438 @findex -interpreter-exec
33440 @subheading Synopsis
33443 -interpreter-exec @var{interpreter} @var{command}
33445 @anchor{-interpreter-exec}
33447 Execute the specified @var{command} in the given @var{interpreter}.
33449 @subheading @value{GDBN} Command
33451 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33453 @subheading Example
33457 -interpreter-exec console "break main"
33458 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33459 &"During symbol reading, bad structure-type format.\n"
33460 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33465 @subheading The @code{-inferior-tty-set} Command
33466 @findex -inferior-tty-set
33468 @subheading Synopsis
33471 -inferior-tty-set /dev/pts/1
33474 Set terminal for future runs of the program being debugged.
33476 @subheading @value{GDBN} Command
33478 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33480 @subheading Example
33484 -inferior-tty-set /dev/pts/1
33489 @subheading The @code{-inferior-tty-show} Command
33490 @findex -inferior-tty-show
33492 @subheading Synopsis
33498 Show terminal for future runs of program being debugged.
33500 @subheading @value{GDBN} Command
33502 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33504 @subheading Example
33508 -inferior-tty-set /dev/pts/1
33512 ^done,inferior_tty_terminal="/dev/pts/1"
33516 @subheading The @code{-enable-timings} Command
33517 @findex -enable-timings
33519 @subheading Synopsis
33522 -enable-timings [yes | no]
33525 Toggle the printing of the wallclock, user and system times for an MI
33526 command as a field in its output. This command is to help frontend
33527 developers optimize the performance of their code. No argument is
33528 equivalent to @samp{yes}.
33530 @subheading @value{GDBN} Command
33534 @subheading Example
33542 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33543 addr="0x080484ed",func="main",file="myprog.c",
33544 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33546 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33554 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33555 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33556 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33557 fullname="/home/nickrob/myprog.c",line="73"@}
33562 @chapter @value{GDBN} Annotations
33564 This chapter describes annotations in @value{GDBN}. Annotations were
33565 designed to interface @value{GDBN} to graphical user interfaces or other
33566 similar programs which want to interact with @value{GDBN} at a
33567 relatively high level.
33569 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33573 This is Edition @value{EDITION}, @value{DATE}.
33577 * Annotations Overview:: What annotations are; the general syntax.
33578 * Server Prefix:: Issuing a command without affecting user state.
33579 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33580 * Errors:: Annotations for error messages.
33581 * Invalidation:: Some annotations describe things now invalid.
33582 * Annotations for Running::
33583 Whether the program is running, how it stopped, etc.
33584 * Source Annotations:: Annotations describing source code.
33587 @node Annotations Overview
33588 @section What is an Annotation?
33589 @cindex annotations
33591 Annotations start with a newline character, two @samp{control-z}
33592 characters, and the name of the annotation. If there is no additional
33593 information associated with this annotation, the name of the annotation
33594 is followed immediately by a newline. If there is additional
33595 information, the name of the annotation is followed by a space, the
33596 additional information, and a newline. The additional information
33597 cannot contain newline characters.
33599 Any output not beginning with a newline and two @samp{control-z}
33600 characters denotes literal output from @value{GDBN}. Currently there is
33601 no need for @value{GDBN} to output a newline followed by two
33602 @samp{control-z} characters, but if there was such a need, the
33603 annotations could be extended with an @samp{escape} annotation which
33604 means those three characters as output.
33606 The annotation @var{level}, which is specified using the
33607 @option{--annotate} command line option (@pxref{Mode Options}), controls
33608 how much information @value{GDBN} prints together with its prompt,
33609 values of expressions, source lines, and other types of output. Level 0
33610 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33611 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33612 for programs that control @value{GDBN}, and level 2 annotations have
33613 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33614 Interface, annotate, GDB's Obsolete Annotations}).
33617 @kindex set annotate
33618 @item set annotate @var{level}
33619 The @value{GDBN} command @code{set annotate} sets the level of
33620 annotations to the specified @var{level}.
33622 @item show annotate
33623 @kindex show annotate
33624 Show the current annotation level.
33627 This chapter describes level 3 annotations.
33629 A simple example of starting up @value{GDBN} with annotations is:
33632 $ @kbd{gdb --annotate=3}
33634 Copyright 2003 Free Software Foundation, Inc.
33635 GDB is free software, covered by the GNU General Public License,
33636 and you are welcome to change it and/or distribute copies of it
33637 under certain conditions.
33638 Type "show copying" to see the conditions.
33639 There is absolutely no warranty for GDB. Type "show warranty"
33641 This GDB was configured as "i386-pc-linux-gnu"
33652 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33653 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33654 denotes a @samp{control-z} character) are annotations; the rest is
33655 output from @value{GDBN}.
33657 @node Server Prefix
33658 @section The Server Prefix
33659 @cindex server prefix
33661 If you prefix a command with @samp{server } then it will not affect
33662 the command history, nor will it affect @value{GDBN}'s notion of which
33663 command to repeat if @key{RET} is pressed on a line by itself. This
33664 means that commands can be run behind a user's back by a front-end in
33665 a transparent manner.
33667 The @code{server } prefix does not affect the recording of values into
33668 the value history; to print a value without recording it into the
33669 value history, use the @code{output} command instead of the
33670 @code{print} command.
33672 Using this prefix also disables confirmation requests
33673 (@pxref{confirmation requests}).
33676 @section Annotation for @value{GDBN} Input
33678 @cindex annotations for prompts
33679 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33680 to know when to send output, when the output from a given command is
33683 Different kinds of input each have a different @dfn{input type}. Each
33684 input type has three annotations: a @code{pre-} annotation, which
33685 denotes the beginning of any prompt which is being output, a plain
33686 annotation, which denotes the end of the prompt, and then a @code{post-}
33687 annotation which denotes the end of any echo which may (or may not) be
33688 associated with the input. For example, the @code{prompt} input type
33689 features the following annotations:
33697 The input types are
33700 @findex pre-prompt annotation
33701 @findex prompt annotation
33702 @findex post-prompt annotation
33704 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33706 @findex pre-commands annotation
33707 @findex commands annotation
33708 @findex post-commands annotation
33710 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33711 command. The annotations are repeated for each command which is input.
33713 @findex pre-overload-choice annotation
33714 @findex overload-choice annotation
33715 @findex post-overload-choice annotation
33716 @item overload-choice
33717 When @value{GDBN} wants the user to select between various overloaded functions.
33719 @findex pre-query annotation
33720 @findex query annotation
33721 @findex post-query annotation
33723 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33725 @findex pre-prompt-for-continue annotation
33726 @findex prompt-for-continue annotation
33727 @findex post-prompt-for-continue annotation
33728 @item prompt-for-continue
33729 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33730 expect this to work well; instead use @code{set height 0} to disable
33731 prompting. This is because the counting of lines is buggy in the
33732 presence of annotations.
33737 @cindex annotations for errors, warnings and interrupts
33739 @findex quit annotation
33744 This annotation occurs right before @value{GDBN} responds to an interrupt.
33746 @findex error annotation
33751 This annotation occurs right before @value{GDBN} responds to an error.
33753 Quit and error annotations indicate that any annotations which @value{GDBN} was
33754 in the middle of may end abruptly. For example, if a
33755 @code{value-history-begin} annotation is followed by a @code{error}, one
33756 cannot expect to receive the matching @code{value-history-end}. One
33757 cannot expect not to receive it either, however; an error annotation
33758 does not necessarily mean that @value{GDBN} is immediately returning all the way
33761 @findex error-begin annotation
33762 A quit or error annotation may be preceded by
33768 Any output between that and the quit or error annotation is the error
33771 Warning messages are not yet annotated.
33772 @c If we want to change that, need to fix warning(), type_error(),
33773 @c range_error(), and possibly other places.
33776 @section Invalidation Notices
33778 @cindex annotations for invalidation messages
33779 The following annotations say that certain pieces of state may have
33783 @findex frames-invalid annotation
33784 @item ^Z^Zframes-invalid
33786 The frames (for example, output from the @code{backtrace} command) may
33789 @findex breakpoints-invalid annotation
33790 @item ^Z^Zbreakpoints-invalid
33792 The breakpoints may have changed. For example, the user just added or
33793 deleted a breakpoint.
33796 @node Annotations for Running
33797 @section Running the Program
33798 @cindex annotations for running programs
33800 @findex starting annotation
33801 @findex stopping annotation
33802 When the program starts executing due to a @value{GDBN} command such as
33803 @code{step} or @code{continue},
33809 is output. When the program stops,
33815 is output. Before the @code{stopped} annotation, a variety of
33816 annotations describe how the program stopped.
33819 @findex exited annotation
33820 @item ^Z^Zexited @var{exit-status}
33821 The program exited, and @var{exit-status} is the exit status (zero for
33822 successful exit, otherwise nonzero).
33824 @findex signalled annotation
33825 @findex signal-name annotation
33826 @findex signal-name-end annotation
33827 @findex signal-string annotation
33828 @findex signal-string-end annotation
33829 @item ^Z^Zsignalled
33830 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33831 annotation continues:
33837 ^Z^Zsignal-name-end
33841 ^Z^Zsignal-string-end
33846 where @var{name} is the name of the signal, such as @code{SIGILL} or
33847 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
33848 as @code{Illegal Instruction} or @code{Segmentation fault}.
33849 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
33850 user's benefit and have no particular format.
33852 @findex signal annotation
33854 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
33855 just saying that the program received the signal, not that it was
33856 terminated with it.
33858 @findex breakpoint annotation
33859 @item ^Z^Zbreakpoint @var{number}
33860 The program hit breakpoint number @var{number}.
33862 @findex watchpoint annotation
33863 @item ^Z^Zwatchpoint @var{number}
33864 The program hit watchpoint number @var{number}.
33867 @node Source Annotations
33868 @section Displaying Source
33869 @cindex annotations for source display
33871 @findex source annotation
33872 The following annotation is used instead of displaying source code:
33875 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
33878 where @var{filename} is an absolute file name indicating which source
33879 file, @var{line} is the line number within that file (where 1 is the
33880 first line in the file), @var{character} is the character position
33881 within the file (where 0 is the first character in the file) (for most
33882 debug formats this will necessarily point to the beginning of a line),
33883 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
33884 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
33885 @var{addr} is the address in the target program associated with the
33886 source which is being displayed. @var{addr} is in the form @samp{0x}
33887 followed by one or more lowercase hex digits (note that this does not
33888 depend on the language).
33890 @node JIT Interface
33891 @chapter JIT Compilation Interface
33892 @cindex just-in-time compilation
33893 @cindex JIT compilation interface
33895 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
33896 interface. A JIT compiler is a program or library that generates native
33897 executable code at runtime and executes it, usually in order to achieve good
33898 performance while maintaining platform independence.
33900 Programs that use JIT compilation are normally difficult to debug because
33901 portions of their code are generated at runtime, instead of being loaded from
33902 object files, which is where @value{GDBN} normally finds the program's symbols
33903 and debug information. In order to debug programs that use JIT compilation,
33904 @value{GDBN} has an interface that allows the program to register in-memory
33905 symbol files with @value{GDBN} at runtime.
33907 If you are using @value{GDBN} to debug a program that uses this interface, then
33908 it should work transparently so long as you have not stripped the binary. If
33909 you are developing a JIT compiler, then the interface is documented in the rest
33910 of this chapter. At this time, the only known client of this interface is the
33913 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
33914 JIT compiler communicates with @value{GDBN} by writing data into a global
33915 variable and calling a fuction at a well-known symbol. When @value{GDBN}
33916 attaches, it reads a linked list of symbol files from the global variable to
33917 find existing code, and puts a breakpoint in the function so that it can find
33918 out about additional code.
33921 * Declarations:: Relevant C struct declarations
33922 * Registering Code:: Steps to register code
33923 * Unregistering Code:: Steps to unregister code
33924 * Custom Debug Info:: Emit debug information in a custom format
33928 @section JIT Declarations
33930 These are the relevant struct declarations that a C program should include to
33931 implement the interface:
33941 struct jit_code_entry
33943 struct jit_code_entry *next_entry;
33944 struct jit_code_entry *prev_entry;
33945 const char *symfile_addr;
33946 uint64_t symfile_size;
33949 struct jit_descriptor
33952 /* This type should be jit_actions_t, but we use uint32_t
33953 to be explicit about the bitwidth. */
33954 uint32_t action_flag;
33955 struct jit_code_entry *relevant_entry;
33956 struct jit_code_entry *first_entry;
33959 /* GDB puts a breakpoint in this function. */
33960 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
33962 /* Make sure to specify the version statically, because the
33963 debugger may check the version before we can set it. */
33964 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
33967 If the JIT is multi-threaded, then it is important that the JIT synchronize any
33968 modifications to this global data properly, which can easily be done by putting
33969 a global mutex around modifications to these structures.
33971 @node Registering Code
33972 @section Registering Code
33974 To register code with @value{GDBN}, the JIT should follow this protocol:
33978 Generate an object file in memory with symbols and other desired debug
33979 information. The file must include the virtual addresses of the sections.
33982 Create a code entry for the file, which gives the start and size of the symbol
33986 Add it to the linked list in the JIT descriptor.
33989 Point the relevant_entry field of the descriptor at the entry.
33992 Set @code{action_flag} to @code{JIT_REGISTER} and call
33993 @code{__jit_debug_register_code}.
33996 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
33997 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
33998 new code. However, the linked list must still be maintained in order to allow
33999 @value{GDBN} to attach to a running process and still find the symbol files.
34001 @node Unregistering Code
34002 @section Unregistering Code
34004 If code is freed, then the JIT should use the following protocol:
34008 Remove the code entry corresponding to the code from the linked list.
34011 Point the @code{relevant_entry} field of the descriptor at the code entry.
34014 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34015 @code{__jit_debug_register_code}.
34018 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34019 and the JIT will leak the memory used for the associated symbol files.
34021 @node Custom Debug Info
34022 @section Custom Debug Info
34023 @cindex custom JIT debug info
34024 @cindex JIT debug info reader
34026 Generating debug information in platform-native file formats (like ELF
34027 or COFF) may be an overkill for JIT compilers; especially if all the
34028 debug info is used for is displaying a meaningful backtrace. The
34029 issue can be resolved by having the JIT writers decide on a debug info
34030 format and also provide a reader that parses the debug info generated
34031 by the JIT compiler. This section gives a brief overview on writing
34032 such a parser. More specific details can be found in the source file
34033 @file{gdb/jit-reader.in}, which is also installed as a header at
34034 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34036 The reader is implemented as a shared object (so this functionality is
34037 not available on platforms which don't allow loading shared objects at
34038 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34039 @code{jit-reader-unload} are provided, to be used to load and unload
34040 the readers from a preconfigured directory. Once loaded, the shared
34041 object is used the parse the debug information emitted by the JIT
34045 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34046 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34049 @node Using JIT Debug Info Readers
34050 @subsection Using JIT Debug Info Readers
34051 @kindex jit-reader-load
34052 @kindex jit-reader-unload
34054 Readers can be loaded and unloaded using the @code{jit-reader-load}
34055 and @code{jit-reader-unload} commands.
34058 @item jit-reader-load @var{reader}
34059 Load the JIT reader named @var{reader}. @var{reader} is a shared
34060 object specified as either an absolute or a relative file name. In
34061 the latter case, @value{GDBN} will try to load the reader from a
34062 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34063 system (here @var{libdir} is the system library directory, often
34064 @file{/usr/local/lib}).
34066 Only one reader can be active at a time; trying to load a second
34067 reader when one is already loaded will result in @value{GDBN}
34068 reporting an error. A new JIT reader can be loaded by first unloading
34069 the current one using @code{jit-reader-unload} and then invoking
34070 @code{jit-reader-load}.
34072 @item jit-reader-unload
34073 Unload the currently loaded JIT reader.
34077 @node Writing JIT Debug Info Readers
34078 @subsection Writing JIT Debug Info Readers
34079 @cindex writing JIT debug info readers
34081 As mentioned, a reader is essentially a shared object conforming to a
34082 certain ABI. This ABI is described in @file{jit-reader.h}.
34084 @file{jit-reader.h} defines the structures, macros and functions
34085 required to write a reader. It is installed (along with
34086 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34087 the system include directory.
34089 Readers need to be released under a GPL compatible license. A reader
34090 can be declared as released under such a license by placing the macro
34091 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34093 The entry point for readers is the symbol @code{gdb_init_reader},
34094 which is expected to be a function with the prototype
34096 @findex gdb_init_reader
34098 extern struct gdb_reader_funcs *gdb_init_reader (void);
34101 @cindex @code{struct gdb_reader_funcs}
34103 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34104 functions. These functions are executed to read the debug info
34105 generated by the JIT compiler (@code{read}), to unwind stack frames
34106 (@code{unwind}) and to create canonical frame IDs
34107 (@code{get_Frame_id}). It also has a callback that is called when the
34108 reader is being unloaded (@code{destroy}). The struct looks like this
34111 struct gdb_reader_funcs
34113 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34114 int reader_version;
34116 /* For use by the reader. */
34119 gdb_read_debug_info *read;
34120 gdb_unwind_frame *unwind;
34121 gdb_get_frame_id *get_frame_id;
34122 gdb_destroy_reader *destroy;
34126 @cindex @code{struct gdb_symbol_callbacks}
34127 @cindex @code{struct gdb_unwind_callbacks}
34129 The callbacks are provided with another set of callbacks by
34130 @value{GDBN} to do their job. For @code{read}, these callbacks are
34131 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34132 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34133 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34134 files and new symbol tables inside those object files. @code{struct
34135 gdb_unwind_callbacks} has callbacks to read registers off the current
34136 frame and to write out the values of the registers in the previous
34137 frame. Both have a callback (@code{target_read}) to read bytes off the
34138 target's address space.
34140 @node In-Process Agent
34141 @chapter In-Process Agent
34142 @cindex debugging agent
34143 The traditional debugging model is conceptually low-speed, but works fine,
34144 because most bugs can be reproduced in debugging-mode execution. However,
34145 as multi-core or many-core processors are becoming mainstream, and
34146 multi-threaded programs become more and more popular, there should be more
34147 and more bugs that only manifest themselves at normal-mode execution, for
34148 example, thread races, because debugger's interference with the program's
34149 timing may conceal the bugs. On the other hand, in some applications,
34150 it is not feasible for the debugger to interrupt the program's execution
34151 long enough for the developer to learn anything helpful about its behavior.
34152 If the program's correctness depends on its real-time behavior, delays
34153 introduced by a debugger might cause the program to fail, even when the
34154 code itself is correct. It is useful to be able to observe the program's
34155 behavior without interrupting it.
34157 Therefore, traditional debugging model is too intrusive to reproduce
34158 some bugs. In order to reduce the interference with the program, we can
34159 reduce the number of operations performed by debugger. The
34160 @dfn{In-Process Agent}, a shared library, is running within the same
34161 process with inferior, and is able to perform some debugging operations
34162 itself. As a result, debugger is only involved when necessary, and
34163 performance of debugging can be improved accordingly. Note that
34164 interference with program can be reduced but can't be removed completely,
34165 because the in-process agent will still stop or slow down the program.
34167 The in-process agent can interpret and execute Agent Expressions
34168 (@pxref{Agent Expressions}) during performing debugging operations. The
34169 agent expressions can be used for different purposes, such as collecting
34170 data in tracepoints, and condition evaluation in breakpoints.
34172 @anchor{Control Agent}
34173 You can control whether the in-process agent is used as an aid for
34174 debugging with the following commands:
34177 @kindex set agent on
34179 Causes the in-process agent to perform some operations on behalf of the
34180 debugger. Just which operations requested by the user will be done
34181 by the in-process agent depends on the its capabilities. For example,
34182 if you request to evaluate breakpoint conditions in the in-process agent,
34183 and the in-process agent has such capability as well, then breakpoint
34184 conditions will be evaluated in the in-process agent.
34186 @kindex set agent off
34187 @item set agent off
34188 Disables execution of debugging operations by the in-process agent. All
34189 of the operations will be performed by @value{GDBN}.
34193 Display the current setting of execution of debugging operations by
34194 the in-process agent.
34198 * In-Process Agent Protocol::
34201 @node In-Process Agent Protocol
34202 @section In-Process Agent Protocol
34203 @cindex in-process agent protocol
34205 The in-process agent is able to communicate with both @value{GDBN} and
34206 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34207 used for communications between @value{GDBN} or GDBserver and the IPA.
34208 In general, @value{GDBN} or GDBserver sends commands
34209 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34210 in-process agent replies back with the return result of the command, or
34211 some other information. The data sent to in-process agent is composed
34212 of primitive data types, such as 4-byte or 8-byte type, and composite
34213 types, which are called objects (@pxref{IPA Protocol Objects}).
34216 * IPA Protocol Objects::
34217 * IPA Protocol Commands::
34220 @node IPA Protocol Objects
34221 @subsection IPA Protocol Objects
34222 @cindex ipa protocol objects
34224 The commands sent to and results received from agent may contain some
34225 complex data types called @dfn{objects}.
34227 The in-process agent is running on the same machine with @value{GDBN}
34228 or GDBserver, so it doesn't have to handle as much differences between
34229 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34230 However, there are still some differences of two ends in two processes:
34234 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34235 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34237 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34238 GDBserver is compiled with one, and in-process agent is compiled with
34242 Here are the IPA Protocol Objects:
34246 agent expression object. It represents an agent expression
34247 (@pxref{Agent Expressions}).
34248 @anchor{agent expression object}
34250 tracepoint action object. It represents a tracepoint action
34251 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34252 memory, static trace data and to evaluate expression.
34253 @anchor{tracepoint action object}
34255 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34256 @anchor{tracepoint object}
34260 The following table describes important attributes of each IPA protocol
34263 @multitable @columnfractions .30 .20 .50
34264 @headitem Name @tab Size @tab Description
34265 @item @emph{agent expression object} @tab @tab
34266 @item length @tab 4 @tab length of bytes code
34267 @item byte code @tab @var{length} @tab contents of byte code
34268 @item @emph{tracepoint action for collecting memory} @tab @tab
34269 @item 'M' @tab 1 @tab type of tracepoint action
34270 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34271 address of the lowest byte to collect, otherwise @var{addr} is the offset
34272 of @var{basereg} for memory collecting.
34273 @item len @tab 8 @tab length of memory for collecting
34274 @item basereg @tab 4 @tab the register number containing the starting
34275 memory address for collecting.
34276 @item @emph{tracepoint action for collecting registers} @tab @tab
34277 @item 'R' @tab 1 @tab type of tracepoint action
34278 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34279 @item 'L' @tab 1 @tab type of tracepoint action
34280 @item @emph{tracepoint action for expression evaluation} @tab @tab
34281 @item 'X' @tab 1 @tab type of tracepoint action
34282 @item agent expression @tab length of @tab @ref{agent expression object}
34283 @item @emph{tracepoint object} @tab @tab
34284 @item number @tab 4 @tab number of tracepoint
34285 @item address @tab 8 @tab address of tracepoint inserted on
34286 @item type @tab 4 @tab type of tracepoint
34287 @item enabled @tab 1 @tab enable or disable of tracepoint
34288 @item step_count @tab 8 @tab step
34289 @item pass_count @tab 8 @tab pass
34290 @item numactions @tab 4 @tab number of tracepoint actions
34291 @item hit count @tab 8 @tab hit count
34292 @item trace frame usage @tab 8 @tab trace frame usage
34293 @item compiled_cond @tab 8 @tab compiled condition
34294 @item orig_size @tab 8 @tab orig size
34295 @item condition @tab 4 if condition is NULL otherwise length of
34296 @ref{agent expression object}
34297 @tab zero if condition is NULL, otherwise is
34298 @ref{agent expression object}
34299 @item actions @tab variable
34300 @tab numactions number of @ref{tracepoint action object}
34303 @node IPA Protocol Commands
34304 @subsection IPA Protocol Commands
34305 @cindex ipa protocol commands
34307 The spaces in each command are delimiters to ease reading this commands
34308 specification. They don't exist in real commands.
34312 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34313 Installs a new fast tracepoint described by @var{tracepoint_object}
34314 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34315 head of @dfn{jumppad}, which is used to jump to data collection routine
34320 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34321 @var{target_address} is address of tracepoint in the inferior.
34322 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34323 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34324 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34325 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34332 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34333 is about to kill inferiors.
34341 @item probe_marker_at:@var{address}
34342 Asks in-process agent to probe the marker at @var{address}.
34349 @item unprobe_marker_at:@var{address}
34350 Asks in-process agent to unprobe the marker at @var{address}.
34354 @chapter Reporting Bugs in @value{GDBN}
34355 @cindex bugs in @value{GDBN}
34356 @cindex reporting bugs in @value{GDBN}
34358 Your bug reports play an essential role in making @value{GDBN} reliable.
34360 Reporting a bug may help you by bringing a solution to your problem, or it
34361 may not. But in any case the principal function of a bug report is to help
34362 the entire community by making the next version of @value{GDBN} work better. Bug
34363 reports are your contribution to the maintenance of @value{GDBN}.
34365 In order for a bug report to serve its purpose, you must include the
34366 information that enables us to fix the bug.
34369 * Bug Criteria:: Have you found a bug?
34370 * Bug Reporting:: How to report bugs
34374 @section Have You Found a Bug?
34375 @cindex bug criteria
34377 If you are not sure whether you have found a bug, here are some guidelines:
34380 @cindex fatal signal
34381 @cindex debugger crash
34382 @cindex crash of debugger
34384 If the debugger gets a fatal signal, for any input whatever, that is a
34385 @value{GDBN} bug. Reliable debuggers never crash.
34387 @cindex error on valid input
34389 If @value{GDBN} produces an error message for valid input, that is a
34390 bug. (Note that if you're cross debugging, the problem may also be
34391 somewhere in the connection to the target.)
34393 @cindex invalid input
34395 If @value{GDBN} does not produce an error message for invalid input,
34396 that is a bug. However, you should note that your idea of
34397 ``invalid input'' might be our idea of ``an extension'' or ``support
34398 for traditional practice''.
34401 If you are an experienced user of debugging tools, your suggestions
34402 for improvement of @value{GDBN} are welcome in any case.
34405 @node Bug Reporting
34406 @section How to Report Bugs
34407 @cindex bug reports
34408 @cindex @value{GDBN} bugs, reporting
34410 A number of companies and individuals offer support for @sc{gnu} products.
34411 If you obtained @value{GDBN} from a support organization, we recommend you
34412 contact that organization first.
34414 You can find contact information for many support companies and
34415 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34417 @c should add a web page ref...
34420 @ifset BUGURL_DEFAULT
34421 In any event, we also recommend that you submit bug reports for
34422 @value{GDBN}. The preferred method is to submit them directly using
34423 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34424 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34427 @strong{Do not send bug reports to @samp{info-gdb}, or to
34428 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34429 not want to receive bug reports. Those that do have arranged to receive
34432 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34433 serves as a repeater. The mailing list and the newsgroup carry exactly
34434 the same messages. Often people think of posting bug reports to the
34435 newsgroup instead of mailing them. This appears to work, but it has one
34436 problem which can be crucial: a newsgroup posting often lacks a mail
34437 path back to the sender. Thus, if we need to ask for more information,
34438 we may be unable to reach you. For this reason, it is better to send
34439 bug reports to the mailing list.
34441 @ifclear BUGURL_DEFAULT
34442 In any event, we also recommend that you submit bug reports for
34443 @value{GDBN} to @value{BUGURL}.
34447 The fundamental principle of reporting bugs usefully is this:
34448 @strong{report all the facts}. If you are not sure whether to state a
34449 fact or leave it out, state it!
34451 Often people omit facts because they think they know what causes the
34452 problem and assume that some details do not matter. Thus, you might
34453 assume that the name of the variable you use in an example does not matter.
34454 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34455 stray memory reference which happens to fetch from the location where that
34456 name is stored in memory; perhaps, if the name were different, the contents
34457 of that location would fool the debugger into doing the right thing despite
34458 the bug. Play it safe and give a specific, complete example. That is the
34459 easiest thing for you to do, and the most helpful.
34461 Keep in mind that the purpose of a bug report is to enable us to fix the
34462 bug. It may be that the bug has been reported previously, but neither
34463 you nor we can know that unless your bug report is complete and
34466 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34467 bell?'' Those bug reports are useless, and we urge everyone to
34468 @emph{refuse to respond to them} except to chide the sender to report
34471 To enable us to fix the bug, you should include all these things:
34475 The version of @value{GDBN}. @value{GDBN} announces it if you start
34476 with no arguments; you can also print it at any time using @code{show
34479 Without this, we will not know whether there is any point in looking for
34480 the bug in the current version of @value{GDBN}.
34483 The type of machine you are using, and the operating system name and
34487 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34488 ``@value{GCC}--2.8.1''.
34491 What compiler (and its version) was used to compile the program you are
34492 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34493 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34494 to get this information; for other compilers, see the documentation for
34498 The command arguments you gave the compiler to compile your example and
34499 observe the bug. For example, did you use @samp{-O}? To guarantee
34500 you will not omit something important, list them all. A copy of the
34501 Makefile (or the output from make) is sufficient.
34503 If we were to try to guess the arguments, we would probably guess wrong
34504 and then we might not encounter the bug.
34507 A complete input script, and all necessary source files, that will
34511 A description of what behavior you observe that you believe is
34512 incorrect. For example, ``It gets a fatal signal.''
34514 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34515 will certainly notice it. But if the bug is incorrect output, we might
34516 not notice unless it is glaringly wrong. You might as well not give us
34517 a chance to make a mistake.
34519 Even if the problem you experience is a fatal signal, you should still
34520 say so explicitly. Suppose something strange is going on, such as, your
34521 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34522 the C library on your system. (This has happened!) Your copy might
34523 crash and ours would not. If you told us to expect a crash, then when
34524 ours fails to crash, we would know that the bug was not happening for
34525 us. If you had not told us to expect a crash, then we would not be able
34526 to draw any conclusion from our observations.
34529 @cindex recording a session script
34530 To collect all this information, you can use a session recording program
34531 such as @command{script}, which is available on many Unix systems.
34532 Just run your @value{GDBN} session inside @command{script} and then
34533 include the @file{typescript} file with your bug report.
34535 Another way to record a @value{GDBN} session is to run @value{GDBN}
34536 inside Emacs and then save the entire buffer to a file.
34539 If you wish to suggest changes to the @value{GDBN} source, send us context
34540 diffs. If you even discuss something in the @value{GDBN} source, refer to
34541 it by context, not by line number.
34543 The line numbers in our development sources will not match those in your
34544 sources. Your line numbers would convey no useful information to us.
34548 Here are some things that are not necessary:
34552 A description of the envelope of the bug.
34554 Often people who encounter a bug spend a lot of time investigating
34555 which changes to the input file will make the bug go away and which
34556 changes will not affect it.
34558 This is often time consuming and not very useful, because the way we
34559 will find the bug is by running a single example under the debugger
34560 with breakpoints, not by pure deduction from a series of examples.
34561 We recommend that you save your time for something else.
34563 Of course, if you can find a simpler example to report @emph{instead}
34564 of the original one, that is a convenience for us. Errors in the
34565 output will be easier to spot, running under the debugger will take
34566 less time, and so on.
34568 However, simplification is not vital; if you do not want to do this,
34569 report the bug anyway and send us the entire test case you used.
34572 A patch for the bug.
34574 A patch for the bug does help us if it is a good one. But do not omit
34575 the necessary information, such as the test case, on the assumption that
34576 a patch is all we need. We might see problems with your patch and decide
34577 to fix the problem another way, or we might not understand it at all.
34579 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34580 construct an example that will make the program follow a certain path
34581 through the code. If you do not send us the example, we will not be able
34582 to construct one, so we will not be able to verify that the bug is fixed.
34584 And if we cannot understand what bug you are trying to fix, or why your
34585 patch should be an improvement, we will not install it. A test case will
34586 help us to understand.
34589 A guess about what the bug is or what it depends on.
34591 Such guesses are usually wrong. Even we cannot guess right about such
34592 things without first using the debugger to find the facts.
34595 @c The readline documentation is distributed with the readline code
34596 @c and consists of the two following files:
34599 @c Use -I with makeinfo to point to the appropriate directory,
34600 @c environment var TEXINPUTS with TeX.
34601 @ifclear SYSTEM_READLINE
34602 @include rluser.texi
34603 @include hsuser.texi
34607 @appendix In Memoriam
34609 The @value{GDBN} project mourns the loss of the following long-time
34614 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34615 to Free Software in general. Outside of @value{GDBN}, he was known in
34616 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34618 @item Michael Snyder
34619 Michael was one of the Global Maintainers of the @value{GDBN} project,
34620 with contributions recorded as early as 1996, until 2011. In addition
34621 to his day to day participation, he was a large driving force behind
34622 adding Reverse Debugging to @value{GDBN}.
34625 Beyond their technical contributions to the project, they were also
34626 enjoyable members of the Free Software Community. We will miss them.
34628 @node Formatting Documentation
34629 @appendix Formatting Documentation
34631 @cindex @value{GDBN} reference card
34632 @cindex reference card
34633 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34634 for printing with PostScript or Ghostscript, in the @file{gdb}
34635 subdirectory of the main source directory@footnote{In
34636 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34637 release.}. If you can use PostScript or Ghostscript with your printer,
34638 you can print the reference card immediately with @file{refcard.ps}.
34640 The release also includes the source for the reference card. You
34641 can format it, using @TeX{}, by typing:
34647 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34648 mode on US ``letter'' size paper;
34649 that is, on a sheet 11 inches wide by 8.5 inches
34650 high. You will need to specify this form of printing as an option to
34651 your @sc{dvi} output program.
34653 @cindex documentation
34655 All the documentation for @value{GDBN} comes as part of the machine-readable
34656 distribution. The documentation is written in Texinfo format, which is
34657 a documentation system that uses a single source file to produce both
34658 on-line information and a printed manual. You can use one of the Info
34659 formatting commands to create the on-line version of the documentation
34660 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34662 @value{GDBN} includes an already formatted copy of the on-line Info
34663 version of this manual in the @file{gdb} subdirectory. The main Info
34664 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34665 subordinate files matching @samp{gdb.info*} in the same directory. If
34666 necessary, you can print out these files, or read them with any editor;
34667 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34668 Emacs or the standalone @code{info} program, available as part of the
34669 @sc{gnu} Texinfo distribution.
34671 If you want to format these Info files yourself, you need one of the
34672 Info formatting programs, such as @code{texinfo-format-buffer} or
34675 If you have @code{makeinfo} installed, and are in the top level
34676 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34677 version @value{GDBVN}), you can make the Info file by typing:
34684 If you want to typeset and print copies of this manual, you need @TeX{},
34685 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34686 Texinfo definitions file.
34688 @TeX{} is a typesetting program; it does not print files directly, but
34689 produces output files called @sc{dvi} files. To print a typeset
34690 document, you need a program to print @sc{dvi} files. If your system
34691 has @TeX{} installed, chances are it has such a program. The precise
34692 command to use depends on your system; @kbd{lpr -d} is common; another
34693 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34694 require a file name without any extension or a @samp{.dvi} extension.
34696 @TeX{} also requires a macro definitions file called
34697 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34698 written in Texinfo format. On its own, @TeX{} cannot either read or
34699 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34700 and is located in the @file{gdb-@var{version-number}/texinfo}
34703 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34704 typeset and print this manual. First switch to the @file{gdb}
34705 subdirectory of the main source directory (for example, to
34706 @file{gdb-@value{GDBVN}/gdb}) and type:
34712 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34714 @node Installing GDB
34715 @appendix Installing @value{GDBN}
34716 @cindex installation
34719 * Requirements:: Requirements for building @value{GDBN}
34720 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34721 * Separate Objdir:: Compiling @value{GDBN} in another directory
34722 * Config Names:: Specifying names for hosts and targets
34723 * Configure Options:: Summary of options for configure
34724 * System-wide configuration:: Having a system-wide init file
34728 @section Requirements for Building @value{GDBN}
34729 @cindex building @value{GDBN}, requirements for
34731 Building @value{GDBN} requires various tools and packages to be available.
34732 Other packages will be used only if they are found.
34734 @heading Tools/Packages Necessary for Building @value{GDBN}
34736 @item ISO C90 compiler
34737 @value{GDBN} is written in ISO C90. It should be buildable with any
34738 working C90 compiler, e.g.@: GCC.
34742 @heading Tools/Packages Optional for Building @value{GDBN}
34746 @value{GDBN} can use the Expat XML parsing library. This library may be
34747 included with your operating system distribution; if it is not, you
34748 can get the latest version from @url{http://expat.sourceforge.net}.
34749 The @file{configure} script will search for this library in several
34750 standard locations; if it is installed in an unusual path, you can
34751 use the @option{--with-libexpat-prefix} option to specify its location.
34757 Remote protocol memory maps (@pxref{Memory Map Format})
34759 Target descriptions (@pxref{Target Descriptions})
34761 Remote shared library lists (@xref{Library List Format},
34762 or alternatively @pxref{Library List Format for SVR4 Targets})
34764 MS-Windows shared libraries (@pxref{Shared Libraries})
34766 Traceframe info (@pxref{Traceframe Info Format})
34770 @cindex compressed debug sections
34771 @value{GDBN} will use the @samp{zlib} library, if available, to read
34772 compressed debug sections. Some linkers, such as GNU gold, are capable
34773 of producing binaries with compressed debug sections. If @value{GDBN}
34774 is compiled with @samp{zlib}, it will be able to read the debug
34775 information in such binaries.
34777 The @samp{zlib} library is likely included with your operating system
34778 distribution; if it is not, you can get the latest version from
34779 @url{http://zlib.net}.
34782 @value{GDBN}'s features related to character sets (@pxref{Character
34783 Sets}) require a functioning @code{iconv} implementation. If you are
34784 on a GNU system, then this is provided by the GNU C Library. Some
34785 other systems also provide a working @code{iconv}.
34787 If @value{GDBN} is using the @code{iconv} program which is installed
34788 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34789 This is done with @option{--with-iconv-bin} which specifies the
34790 directory that contains the @code{iconv} program.
34792 On systems without @code{iconv}, you can install GNU Libiconv. If you
34793 have previously installed Libiconv, you can use the
34794 @option{--with-libiconv-prefix} option to configure.
34796 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34797 arrange to build Libiconv if a directory named @file{libiconv} appears
34798 in the top-most source directory. If Libiconv is built this way, and
34799 if the operating system does not provide a suitable @code{iconv}
34800 implementation, then the just-built library will automatically be used
34801 by @value{GDBN}. One easy way to set this up is to download GNU
34802 Libiconv, unpack it, and then rename the directory holding the
34803 Libiconv source code to @samp{libiconv}.
34806 @node Running Configure
34807 @section Invoking the @value{GDBN} @file{configure} Script
34808 @cindex configuring @value{GDBN}
34809 @value{GDBN} comes with a @file{configure} script that automates the process
34810 of preparing @value{GDBN} for installation; you can then use @code{make} to
34811 build the @code{gdb} program.
34813 @c irrelevant in info file; it's as current as the code it lives with.
34814 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34815 look at the @file{README} file in the sources; we may have improved the
34816 installation procedures since publishing this manual.}
34819 The @value{GDBN} distribution includes all the source code you need for
34820 @value{GDBN} in a single directory, whose name is usually composed by
34821 appending the version number to @samp{gdb}.
34823 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34824 @file{gdb-@value{GDBVN}} directory. That directory contains:
34827 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34828 script for configuring @value{GDBN} and all its supporting libraries
34830 @item gdb-@value{GDBVN}/gdb
34831 the source specific to @value{GDBN} itself
34833 @item gdb-@value{GDBVN}/bfd
34834 source for the Binary File Descriptor library
34836 @item gdb-@value{GDBVN}/include
34837 @sc{gnu} include files
34839 @item gdb-@value{GDBVN}/libiberty
34840 source for the @samp{-liberty} free software library
34842 @item gdb-@value{GDBVN}/opcodes
34843 source for the library of opcode tables and disassemblers
34845 @item gdb-@value{GDBVN}/readline
34846 source for the @sc{gnu} command-line interface
34848 @item gdb-@value{GDBVN}/glob
34849 source for the @sc{gnu} filename pattern-matching subroutine
34851 @item gdb-@value{GDBVN}/mmalloc
34852 source for the @sc{gnu} memory-mapped malloc package
34855 The simplest way to configure and build @value{GDBN} is to run @file{configure}
34856 from the @file{gdb-@var{version-number}} source directory, which in
34857 this example is the @file{gdb-@value{GDBVN}} directory.
34859 First switch to the @file{gdb-@var{version-number}} source directory
34860 if you are not already in it; then run @file{configure}. Pass the
34861 identifier for the platform on which @value{GDBN} will run as an
34867 cd gdb-@value{GDBVN}
34868 ./configure @var{host}
34873 where @var{host} is an identifier such as @samp{sun4} or
34874 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
34875 (You can often leave off @var{host}; @file{configure} tries to guess the
34876 correct value by examining your system.)
34878 Running @samp{configure @var{host}} and then running @code{make} builds the
34879 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
34880 libraries, then @code{gdb} itself. The configured source files, and the
34881 binaries, are left in the corresponding source directories.
34884 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
34885 system does not recognize this automatically when you run a different
34886 shell, you may need to run @code{sh} on it explicitly:
34889 sh configure @var{host}
34892 If you run @file{configure} from a directory that contains source
34893 directories for multiple libraries or programs, such as the
34894 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
34896 creates configuration files for every directory level underneath (unless
34897 you tell it not to, with the @samp{--norecursion} option).
34899 You should run the @file{configure} script from the top directory in the
34900 source tree, the @file{gdb-@var{version-number}} directory. If you run
34901 @file{configure} from one of the subdirectories, you will configure only
34902 that subdirectory. That is usually not what you want. In particular,
34903 if you run the first @file{configure} from the @file{gdb} subdirectory
34904 of the @file{gdb-@var{version-number}} directory, you will omit the
34905 configuration of @file{bfd}, @file{readline}, and other sibling
34906 directories of the @file{gdb} subdirectory. This leads to build errors
34907 about missing include files such as @file{bfd/bfd.h}.
34909 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
34910 However, you should make sure that the shell on your path (named by
34911 the @samp{SHELL} environment variable) is publicly readable. Remember
34912 that @value{GDBN} uses the shell to start your program---some systems refuse to
34913 let @value{GDBN} debug child processes whose programs are not readable.
34915 @node Separate Objdir
34916 @section Compiling @value{GDBN} in Another Directory
34918 If you want to run @value{GDBN} versions for several host or target machines,
34919 you need a different @code{gdb} compiled for each combination of
34920 host and target. @file{configure} is designed to make this easy by
34921 allowing you to generate each configuration in a separate subdirectory,
34922 rather than in the source directory. If your @code{make} program
34923 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
34924 @code{make} in each of these directories builds the @code{gdb}
34925 program specified there.
34927 To build @code{gdb} in a separate directory, run @file{configure}
34928 with the @samp{--srcdir} option to specify where to find the source.
34929 (You also need to specify a path to find @file{configure}
34930 itself from your working directory. If the path to @file{configure}
34931 would be the same as the argument to @samp{--srcdir}, you can leave out
34932 the @samp{--srcdir} option; it is assumed.)
34934 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
34935 separate directory for a Sun 4 like this:
34939 cd gdb-@value{GDBVN}
34942 ../gdb-@value{GDBVN}/configure sun4
34947 When @file{configure} builds a configuration using a remote source
34948 directory, it creates a tree for the binaries with the same structure
34949 (and using the same names) as the tree under the source directory. In
34950 the example, you'd find the Sun 4 library @file{libiberty.a} in the
34951 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
34952 @file{gdb-sun4/gdb}.
34954 Make sure that your path to the @file{configure} script has just one
34955 instance of @file{gdb} in it. If your path to @file{configure} looks
34956 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
34957 one subdirectory of @value{GDBN}, not the whole package. This leads to
34958 build errors about missing include files such as @file{bfd/bfd.h}.
34960 One popular reason to build several @value{GDBN} configurations in separate
34961 directories is to configure @value{GDBN} for cross-compiling (where
34962 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
34963 programs that run on another machine---the @dfn{target}).
34964 You specify a cross-debugging target by
34965 giving the @samp{--target=@var{target}} option to @file{configure}.
34967 When you run @code{make} to build a program or library, you must run
34968 it in a configured directory---whatever directory you were in when you
34969 called @file{configure} (or one of its subdirectories).
34971 The @code{Makefile} that @file{configure} generates in each source
34972 directory also runs recursively. If you type @code{make} in a source
34973 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
34974 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
34975 will build all the required libraries, and then build GDB.
34977 When you have multiple hosts or targets configured in separate
34978 directories, you can run @code{make} on them in parallel (for example,
34979 if they are NFS-mounted on each of the hosts); they will not interfere
34983 @section Specifying Names for Hosts and Targets
34985 The specifications used for hosts and targets in the @file{configure}
34986 script are based on a three-part naming scheme, but some short predefined
34987 aliases are also supported. The full naming scheme encodes three pieces
34988 of information in the following pattern:
34991 @var{architecture}-@var{vendor}-@var{os}
34994 For example, you can use the alias @code{sun4} as a @var{host} argument,
34995 or as the value for @var{target} in a @code{--target=@var{target}}
34996 option. The equivalent full name is @samp{sparc-sun-sunos4}.
34998 The @file{configure} script accompanying @value{GDBN} does not provide
34999 any query facility to list all supported host and target names or
35000 aliases. @file{configure} calls the Bourne shell script
35001 @code{config.sub} to map abbreviations to full names; you can read the
35002 script, if you wish, or you can use it to test your guesses on
35003 abbreviations---for example:
35006 % sh config.sub i386-linux
35008 % sh config.sub alpha-linux
35009 alpha-unknown-linux-gnu
35010 % sh config.sub hp9k700
35012 % sh config.sub sun4
35013 sparc-sun-sunos4.1.1
35014 % sh config.sub sun3
35015 m68k-sun-sunos4.1.1
35016 % sh config.sub i986v
35017 Invalid configuration `i986v': machine `i986v' not recognized
35021 @code{config.sub} is also distributed in the @value{GDBN} source
35022 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35024 @node Configure Options
35025 @section @file{configure} Options
35027 Here is a summary of the @file{configure} options and arguments that
35028 are most often useful for building @value{GDBN}. @file{configure} also has
35029 several other options not listed here. @inforef{What Configure
35030 Does,,configure.info}, for a full explanation of @file{configure}.
35033 configure @r{[}--help@r{]}
35034 @r{[}--prefix=@var{dir}@r{]}
35035 @r{[}--exec-prefix=@var{dir}@r{]}
35036 @r{[}--srcdir=@var{dirname}@r{]}
35037 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35038 @r{[}--target=@var{target}@r{]}
35043 You may introduce options with a single @samp{-} rather than
35044 @samp{--} if you prefer; but you may abbreviate option names if you use
35049 Display a quick summary of how to invoke @file{configure}.
35051 @item --prefix=@var{dir}
35052 Configure the source to install programs and files under directory
35055 @item --exec-prefix=@var{dir}
35056 Configure the source to install programs under directory
35059 @c avoid splitting the warning from the explanation:
35061 @item --srcdir=@var{dirname}
35062 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35063 @code{make} that implements the @code{VPATH} feature.}@*
35064 Use this option to make configurations in directories separate from the
35065 @value{GDBN} source directories. Among other things, you can use this to
35066 build (or maintain) several configurations simultaneously, in separate
35067 directories. @file{configure} writes configuration-specific files in
35068 the current directory, but arranges for them to use the source in the
35069 directory @var{dirname}. @file{configure} creates directories under
35070 the working directory in parallel to the source directories below
35073 @item --norecursion
35074 Configure only the directory level where @file{configure} is executed; do not
35075 propagate configuration to subdirectories.
35077 @item --target=@var{target}
35078 Configure @value{GDBN} for cross-debugging programs running on the specified
35079 @var{target}. Without this option, @value{GDBN} is configured to debug
35080 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35082 There is no convenient way to generate a list of all available targets.
35084 @item @var{host} @dots{}
35085 Configure @value{GDBN} to run on the specified @var{host}.
35087 There is no convenient way to generate a list of all available hosts.
35090 There are many other options available as well, but they are generally
35091 needed for special purposes only.
35093 @node System-wide configuration
35094 @section System-wide configuration and settings
35095 @cindex system-wide init file
35097 @value{GDBN} can be configured to have a system-wide init file;
35098 this file will be read and executed at startup (@pxref{Startup, , What
35099 @value{GDBN} does during startup}).
35101 Here is the corresponding configure option:
35104 @item --with-system-gdbinit=@var{file}
35105 Specify that the default location of the system-wide init file is
35109 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35110 it may be subject to relocation. Two possible cases:
35114 If the default location of this init file contains @file{$prefix},
35115 it will be subject to relocation. Suppose that the configure options
35116 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35117 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35118 init file is looked for as @file{$install/etc/gdbinit} instead of
35119 @file{$prefix/etc/gdbinit}.
35122 By contrast, if the default location does not contain the prefix,
35123 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35124 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35125 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35126 wherever @value{GDBN} is installed.
35129 If the configured location of the system-wide init file (as given by the
35130 @option{--with-system-gdbinit} option at configure time) is in the
35131 data-directory (as specified by @option{--with-gdb-datadir} at configure
35132 time) or in one of its subdirectories, then @value{GDBN} will look for the
35133 system-wide init file in the directory specified by the
35134 @option{--data-directory} command-line option.
35135 Note that the system-wide init file is only read once, during @value{GDBN}
35136 initialization. If the data-directory is changed after @value{GDBN} has
35137 started with the @code{set data-directory} command, the file will not be
35140 @node Maintenance Commands
35141 @appendix Maintenance Commands
35142 @cindex maintenance commands
35143 @cindex internal commands
35145 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35146 includes a number of commands intended for @value{GDBN} developers,
35147 that are not documented elsewhere in this manual. These commands are
35148 provided here for reference. (For commands that turn on debugging
35149 messages, see @ref{Debugging Output}.)
35152 @kindex maint agent
35153 @kindex maint agent-eval
35154 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35155 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35156 Translate the given @var{expression} into remote agent bytecodes.
35157 This command is useful for debugging the Agent Expression mechanism
35158 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35159 expression useful for data collection, such as by tracepoints, while
35160 @samp{maint agent-eval} produces an expression that evaluates directly
35161 to a result. For instance, a collection expression for @code{globa +
35162 globb} will include bytecodes to record four bytes of memory at each
35163 of the addresses of @code{globa} and @code{globb}, while discarding
35164 the result of the addition, while an evaluation expression will do the
35165 addition and return the sum.
35166 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35167 If not, generate remote agent bytecode for current frame PC address.
35169 @kindex maint agent-printf
35170 @item maint agent-printf @var{format},@var{expr},...
35171 Translate the given format string and list of argument expressions
35172 into remote agent bytecodes and display them as a disassembled list.
35173 This command is useful for debugging the agent version of dynamic
35174 printf (@pxref{Dynamic Printf}.
35176 @kindex maint info breakpoints
35177 @item @anchor{maint info breakpoints}maint info breakpoints
35178 Using the same format as @samp{info breakpoints}, display both the
35179 breakpoints you've set explicitly, and those @value{GDBN} is using for
35180 internal purposes. Internal breakpoints are shown with negative
35181 breakpoint numbers. The type column identifies what kind of breakpoint
35186 Normal, explicitly set breakpoint.
35189 Normal, explicitly set watchpoint.
35192 Internal breakpoint, used to handle correctly stepping through
35193 @code{longjmp} calls.
35195 @item longjmp resume
35196 Internal breakpoint at the target of a @code{longjmp}.
35199 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35202 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35205 Shared library events.
35209 @kindex maint info bfds
35210 @item maint info bfds
35211 This prints information about each @code{bfd} object that is known to
35212 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35214 @kindex set displaced-stepping
35215 @kindex show displaced-stepping
35216 @cindex displaced stepping support
35217 @cindex out-of-line single-stepping
35218 @item set displaced-stepping
35219 @itemx show displaced-stepping
35220 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35221 if the target supports it. Displaced stepping is a way to single-step
35222 over breakpoints without removing them from the inferior, by executing
35223 an out-of-line copy of the instruction that was originally at the
35224 breakpoint location. It is also known as out-of-line single-stepping.
35227 @item set displaced-stepping on
35228 If the target architecture supports it, @value{GDBN} will use
35229 displaced stepping to step over breakpoints.
35231 @item set displaced-stepping off
35232 @value{GDBN} will not use displaced stepping to step over breakpoints,
35233 even if such is supported by the target architecture.
35235 @cindex non-stop mode, and @samp{set displaced-stepping}
35236 @item set displaced-stepping auto
35237 This is the default mode. @value{GDBN} will use displaced stepping
35238 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35239 architecture supports displaced stepping.
35242 @kindex maint check-symtabs
35243 @item maint check-symtabs
35244 Check the consistency of psymtabs and symtabs.
35246 @kindex maint cplus first_component
35247 @item maint cplus first_component @var{name}
35248 Print the first C@t{++} class/namespace component of @var{name}.
35250 @kindex maint cplus namespace
35251 @item maint cplus namespace
35252 Print the list of possible C@t{++} namespaces.
35254 @kindex maint demangle
35255 @item maint demangle @var{name}
35256 Demangle a C@t{++} or Objective-C mangled @var{name}.
35258 @kindex maint deprecate
35259 @kindex maint undeprecate
35260 @cindex deprecated commands
35261 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35262 @itemx maint undeprecate @var{command}
35263 Deprecate or undeprecate the named @var{command}. Deprecated commands
35264 cause @value{GDBN} to issue a warning when you use them. The optional
35265 argument @var{replacement} says which newer command should be used in
35266 favor of the deprecated one; if it is given, @value{GDBN} will mention
35267 the replacement as part of the warning.
35269 @kindex maint dump-me
35270 @item maint dump-me
35271 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35272 Cause a fatal signal in the debugger and force it to dump its core.
35273 This is supported only on systems which support aborting a program
35274 with the @code{SIGQUIT} signal.
35276 @kindex maint internal-error
35277 @kindex maint internal-warning
35278 @item maint internal-error @r{[}@var{message-text}@r{]}
35279 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35280 Cause @value{GDBN} to call the internal function @code{internal_error}
35281 or @code{internal_warning} and hence behave as though an internal error
35282 or internal warning has been detected. In addition to reporting the
35283 internal problem, these functions give the user the opportunity to
35284 either quit @value{GDBN} or create a core file of the current
35285 @value{GDBN} session.
35287 These commands take an optional parameter @var{message-text} that is
35288 used as the text of the error or warning message.
35290 Here's an example of using @code{internal-error}:
35293 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35294 @dots{}/maint.c:121: internal-error: testing, 1, 2
35295 A problem internal to GDB has been detected. Further
35296 debugging may prove unreliable.
35297 Quit this debugging session? (y or n) @kbd{n}
35298 Create a core file? (y or n) @kbd{n}
35302 @cindex @value{GDBN} internal error
35303 @cindex internal errors, control of @value{GDBN} behavior
35305 @kindex maint set internal-error
35306 @kindex maint show internal-error
35307 @kindex maint set internal-warning
35308 @kindex maint show internal-warning
35309 @item maint set internal-error @var{action} [ask|yes|no]
35310 @itemx maint show internal-error @var{action}
35311 @itemx maint set internal-warning @var{action} [ask|yes|no]
35312 @itemx maint show internal-warning @var{action}
35313 When @value{GDBN} reports an internal problem (error or warning) it
35314 gives the user the opportunity to both quit @value{GDBN} and create a
35315 core file of the current @value{GDBN} session. These commands let you
35316 override the default behaviour for each particular @var{action},
35317 described in the table below.
35321 You can specify that @value{GDBN} should always (yes) or never (no)
35322 quit. The default is to ask the user what to do.
35325 You can specify that @value{GDBN} should always (yes) or never (no)
35326 create a core file. The default is to ask the user what to do.
35329 @kindex maint packet
35330 @item maint packet @var{text}
35331 If @value{GDBN} is talking to an inferior via the serial protocol,
35332 then this command sends the string @var{text} to the inferior, and
35333 displays the response packet. @value{GDBN} supplies the initial
35334 @samp{$} character, the terminating @samp{#} character, and the
35337 @kindex maint print architecture
35338 @item maint print architecture @r{[}@var{file}@r{]}
35339 Print the entire architecture configuration. The optional argument
35340 @var{file} names the file where the output goes.
35342 @kindex maint print c-tdesc
35343 @item maint print c-tdesc
35344 Print the current target description (@pxref{Target Descriptions}) as
35345 a C source file. The created source file can be used in @value{GDBN}
35346 when an XML parser is not available to parse the description.
35348 @kindex maint print dummy-frames
35349 @item maint print dummy-frames
35350 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35353 (@value{GDBP}) @kbd{b add}
35355 (@value{GDBP}) @kbd{print add(2,3)}
35356 Breakpoint 2, add (a=2, b=3) at @dots{}
35358 The program being debugged stopped while in a function called from GDB.
35360 (@value{GDBP}) @kbd{maint print dummy-frames}
35361 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35362 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35363 call_lo=0x01014000 call_hi=0x01014001
35367 Takes an optional file parameter.
35369 @kindex maint print registers
35370 @kindex maint print raw-registers
35371 @kindex maint print cooked-registers
35372 @kindex maint print register-groups
35373 @kindex maint print remote-registers
35374 @item maint print registers @r{[}@var{file}@r{]}
35375 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35376 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35377 @itemx maint print register-groups @r{[}@var{file}@r{]}
35378 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35379 Print @value{GDBN}'s internal register data structures.
35381 The command @code{maint print raw-registers} includes the contents of
35382 the raw register cache; the command @code{maint print
35383 cooked-registers} includes the (cooked) value of all registers,
35384 including registers which aren't available on the target nor visible
35385 to user; the command @code{maint print register-groups} includes the
35386 groups that each register is a member of; and the command @code{maint
35387 print remote-registers} includes the remote target's register numbers
35388 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35389 @value{GDBN} Internals}.
35391 These commands take an optional parameter, a file name to which to
35392 write the information.
35394 @kindex maint print reggroups
35395 @item maint print reggroups @r{[}@var{file}@r{]}
35396 Print @value{GDBN}'s internal register group data structures. The
35397 optional argument @var{file} tells to what file to write the
35400 The register groups info looks like this:
35403 (@value{GDBP}) @kbd{maint print reggroups}
35416 This command forces @value{GDBN} to flush its internal register cache.
35418 @kindex maint print objfiles
35419 @cindex info for known object files
35420 @item maint print objfiles
35421 Print a dump of all known object files. For each object file, this
35422 command prints its name, address in memory, and all of its psymtabs
35425 @kindex maint print section-scripts
35426 @cindex info for known .debug_gdb_scripts-loaded scripts
35427 @item maint print section-scripts [@var{regexp}]
35428 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35429 If @var{regexp} is specified, only print scripts loaded by object files
35430 matching @var{regexp}.
35431 For each script, this command prints its name as specified in the objfile,
35432 and the full path if known.
35433 @xref{dotdebug_gdb_scripts section}.
35435 @kindex maint print statistics
35436 @cindex bcache statistics
35437 @item maint print statistics
35438 This command prints, for each object file in the program, various data
35439 about that object file followed by the byte cache (@dfn{bcache})
35440 statistics for the object file. The objfile data includes the number
35441 of minimal, partial, full, and stabs symbols, the number of types
35442 defined by the objfile, the number of as yet unexpanded psym tables,
35443 the number of line tables and string tables, and the amount of memory
35444 used by the various tables. The bcache statistics include the counts,
35445 sizes, and counts of duplicates of all and unique objects, max,
35446 average, and median entry size, total memory used and its overhead and
35447 savings, and various measures of the hash table size and chain
35450 @kindex maint print target-stack
35451 @cindex target stack description
35452 @item maint print target-stack
35453 A @dfn{target} is an interface between the debugger and a particular
35454 kind of file or process. Targets can be stacked in @dfn{strata},
35455 so that more than one target can potentially respond to a request.
35456 In particular, memory accesses will walk down the stack of targets
35457 until they find a target that is interested in handling that particular
35460 This command prints a short description of each layer that was pushed on
35461 the @dfn{target stack}, starting from the top layer down to the bottom one.
35463 @kindex maint print type
35464 @cindex type chain of a data type
35465 @item maint print type @var{expr}
35466 Print the type chain for a type specified by @var{expr}. The argument
35467 can be either a type name or a symbol. If it is a symbol, the type of
35468 that symbol is described. The type chain produced by this command is
35469 a recursive definition of the data type as stored in @value{GDBN}'s
35470 data structures, including its flags and contained types.
35472 @kindex maint set dwarf2 always-disassemble
35473 @kindex maint show dwarf2 always-disassemble
35474 @item maint set dwarf2 always-disassemble
35475 @item maint show dwarf2 always-disassemble
35476 Control the behavior of @code{info address} when using DWARF debugging
35479 The default is @code{off}, which means that @value{GDBN} should try to
35480 describe a variable's location in an easily readable format. When
35481 @code{on}, @value{GDBN} will instead display the DWARF location
35482 expression in an assembly-like format. Note that some locations are
35483 too complex for @value{GDBN} to describe simply; in this case you will
35484 always see the disassembly form.
35486 Here is an example of the resulting disassembly:
35489 (gdb) info addr argc
35490 Symbol "argc" is a complex DWARF expression:
35494 For more information on these expressions, see
35495 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35497 @kindex maint set dwarf2 max-cache-age
35498 @kindex maint show dwarf2 max-cache-age
35499 @item maint set dwarf2 max-cache-age
35500 @itemx maint show dwarf2 max-cache-age
35501 Control the DWARF 2 compilation unit cache.
35503 @cindex DWARF 2 compilation units cache
35504 In object files with inter-compilation-unit references, such as those
35505 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35506 reader needs to frequently refer to previously read compilation units.
35507 This setting controls how long a compilation unit will remain in the
35508 cache if it is not referenced. A higher limit means that cached
35509 compilation units will be stored in memory longer, and more total
35510 memory will be used. Setting it to zero disables caching, which will
35511 slow down @value{GDBN} startup, but reduce memory consumption.
35513 @kindex maint set profile
35514 @kindex maint show profile
35515 @cindex profiling GDB
35516 @item maint set profile
35517 @itemx maint show profile
35518 Control profiling of @value{GDBN}.
35520 Profiling will be disabled until you use the @samp{maint set profile}
35521 command to enable it. When you enable profiling, the system will begin
35522 collecting timing and execution count data; when you disable profiling or
35523 exit @value{GDBN}, the results will be written to a log file. Remember that
35524 if you use profiling, @value{GDBN} will overwrite the profiling log file
35525 (often called @file{gmon.out}). If you have a record of important profiling
35526 data in a @file{gmon.out} file, be sure to move it to a safe location.
35528 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35529 compiled with the @samp{-pg} compiler option.
35531 @kindex maint set show-debug-regs
35532 @kindex maint show show-debug-regs
35533 @cindex hardware debug registers
35534 @item maint set show-debug-regs
35535 @itemx maint show show-debug-regs
35536 Control whether to show variables that mirror the hardware debug
35537 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35538 enabled, the debug registers values are shown when @value{GDBN} inserts or
35539 removes a hardware breakpoint or watchpoint, and when the inferior
35540 triggers a hardware-assisted breakpoint or watchpoint.
35542 @kindex maint set show-all-tib
35543 @kindex maint show show-all-tib
35544 @item maint set show-all-tib
35545 @itemx maint show show-all-tib
35546 Control whether to show all non zero areas within a 1k block starting
35547 at thread local base, when using the @samp{info w32 thread-information-block}
35550 @kindex maint space
35551 @cindex memory used by commands
35553 Control whether to display memory usage for each command. If set to a
35554 nonzero value, @value{GDBN} will display how much memory each command
35555 took, following the command's own output. This can also be requested
35556 by invoking @value{GDBN} with the @option{--statistics} command-line
35557 switch (@pxref{Mode Options}).
35560 @cindex time of command execution
35562 Control whether to display the execution time of @value{GDBN} for each command.
35563 If set to a nonzero value, @value{GDBN} will display how much time it
35564 took to execute each command, following the command's own output.
35565 Both CPU time and wallclock time are printed.
35566 Printing both is useful when trying to determine whether the cost is
35567 CPU or, e.g., disk/network, latency.
35568 Note that the CPU time printed is for @value{GDBN} only, it does not include
35569 the execution time of the inferior because there's no mechanism currently
35570 to compute how much time was spent by @value{GDBN} and how much time was
35571 spent by the program been debugged.
35572 This can also be requested by invoking @value{GDBN} with the
35573 @option{--statistics} command-line switch (@pxref{Mode Options}).
35575 @kindex maint translate-address
35576 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35577 Find the symbol stored at the location specified by the address
35578 @var{addr} and an optional section name @var{section}. If found,
35579 @value{GDBN} prints the name of the closest symbol and an offset from
35580 the symbol's location to the specified address. This is similar to
35581 the @code{info address} command (@pxref{Symbols}), except that this
35582 command also allows to find symbols in other sections.
35584 If section was not specified, the section in which the symbol was found
35585 is also printed. For dynamically linked executables, the name of
35586 executable or shared library containing the symbol is printed as well.
35590 The following command is useful for non-interactive invocations of
35591 @value{GDBN}, such as in the test suite.
35594 @item set watchdog @var{nsec}
35595 @kindex set watchdog
35596 @cindex watchdog timer
35597 @cindex timeout for commands
35598 Set the maximum number of seconds @value{GDBN} will wait for the
35599 target operation to finish. If this time expires, @value{GDBN}
35600 reports and error and the command is aborted.
35602 @item show watchdog
35603 Show the current setting of the target wait timeout.
35606 @node Remote Protocol
35607 @appendix @value{GDBN} Remote Serial Protocol
35612 * Stop Reply Packets::
35613 * General Query Packets::
35614 * Architecture-Specific Protocol Details::
35615 * Tracepoint Packets::
35616 * Host I/O Packets::
35618 * Notification Packets::
35619 * Remote Non-Stop::
35620 * Packet Acknowledgment::
35622 * File-I/O Remote Protocol Extension::
35623 * Library List Format::
35624 * Library List Format for SVR4 Targets::
35625 * Memory Map Format::
35626 * Thread List Format::
35627 * Traceframe Info Format::
35633 There may be occasions when you need to know something about the
35634 protocol---for example, if there is only one serial port to your target
35635 machine, you might want your program to do something special if it
35636 recognizes a packet meant for @value{GDBN}.
35638 In the examples below, @samp{->} and @samp{<-} are used to indicate
35639 transmitted and received data, respectively.
35641 @cindex protocol, @value{GDBN} remote serial
35642 @cindex serial protocol, @value{GDBN} remote
35643 @cindex remote serial protocol
35644 All @value{GDBN} commands and responses (other than acknowledgments
35645 and notifications, see @ref{Notification Packets}) are sent as a
35646 @var{packet}. A @var{packet} is introduced with the character
35647 @samp{$}, the actual @var{packet-data}, and the terminating character
35648 @samp{#} followed by a two-digit @var{checksum}:
35651 @code{$}@var{packet-data}@code{#}@var{checksum}
35655 @cindex checksum, for @value{GDBN} remote
35657 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35658 characters between the leading @samp{$} and the trailing @samp{#} (an
35659 eight bit unsigned checksum).
35661 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35662 specification also included an optional two-digit @var{sequence-id}:
35665 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35668 @cindex sequence-id, for @value{GDBN} remote
35670 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35671 has never output @var{sequence-id}s. Stubs that handle packets added
35672 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35674 When either the host or the target machine receives a packet, the first
35675 response expected is an acknowledgment: either @samp{+} (to indicate
35676 the package was received correctly) or @samp{-} (to request
35680 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35685 The @samp{+}/@samp{-} acknowledgments can be disabled
35686 once a connection is established.
35687 @xref{Packet Acknowledgment}, for details.
35689 The host (@value{GDBN}) sends @var{command}s, and the target (the
35690 debugging stub incorporated in your program) sends a @var{response}. In
35691 the case of step and continue @var{command}s, the response is only sent
35692 when the operation has completed, and the target has again stopped all
35693 threads in all attached processes. This is the default all-stop mode
35694 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35695 execution mode; see @ref{Remote Non-Stop}, for details.
35697 @var{packet-data} consists of a sequence of characters with the
35698 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35701 @cindex remote protocol, field separator
35702 Fields within the packet should be separated using @samp{,} @samp{;} or
35703 @samp{:}. Except where otherwise noted all numbers are represented in
35704 @sc{hex} with leading zeros suppressed.
35706 Implementors should note that prior to @value{GDBN} 5.0, the character
35707 @samp{:} could not appear as the third character in a packet (as it
35708 would potentially conflict with the @var{sequence-id}).
35710 @cindex remote protocol, binary data
35711 @anchor{Binary Data}
35712 Binary data in most packets is encoded either as two hexadecimal
35713 digits per byte of binary data. This allowed the traditional remote
35714 protocol to work over connections which were only seven-bit clean.
35715 Some packets designed more recently assume an eight-bit clean
35716 connection, and use a more efficient encoding to send and receive
35719 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35720 as an escape character. Any escaped byte is transmitted as the escape
35721 character followed by the original character XORed with @code{0x20}.
35722 For example, the byte @code{0x7d} would be transmitted as the two
35723 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35724 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35725 @samp{@}}) must always be escaped. Responses sent by the stub
35726 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35727 is not interpreted as the start of a run-length encoded sequence
35730 Response @var{data} can be run-length encoded to save space.
35731 Run-length encoding replaces runs of identical characters with one
35732 instance of the repeated character, followed by a @samp{*} and a
35733 repeat count. The repeat count is itself sent encoded, to avoid
35734 binary characters in @var{data}: a value of @var{n} is sent as
35735 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35736 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35737 code 32) for a repeat count of 3. (This is because run-length
35738 encoding starts to win for counts 3 or more.) Thus, for example,
35739 @samp{0* } is a run-length encoding of ``0000'': the space character
35740 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35743 The printable characters @samp{#} and @samp{$} or with a numeric value
35744 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35745 seven repeats (@samp{$}) can be expanded using a repeat count of only
35746 five (@samp{"}). For example, @samp{00000000} can be encoded as
35749 The error response returned for some packets includes a two character
35750 error number. That number is not well defined.
35752 @cindex empty response, for unsupported packets
35753 For any @var{command} not supported by the stub, an empty response
35754 (@samp{$#00}) should be returned. That way it is possible to extend the
35755 protocol. A newer @value{GDBN} can tell if a packet is supported based
35758 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35759 commands for register access, and the @samp{m} and @samp{M} commands
35760 for memory access. Stubs that only control single-threaded targets
35761 can implement run control with the @samp{c} (continue), and @samp{s}
35762 (step) commands. Stubs that support multi-threading targets should
35763 support the @samp{vCont} command. All other commands are optional.
35768 The following table provides a complete list of all currently defined
35769 @var{command}s and their corresponding response @var{data}.
35770 @xref{File-I/O Remote Protocol Extension}, for details about the File
35771 I/O extension of the remote protocol.
35773 Each packet's description has a template showing the packet's overall
35774 syntax, followed by an explanation of the packet's meaning. We
35775 include spaces in some of the templates for clarity; these are not
35776 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35777 separate its components. For example, a template like @samp{foo
35778 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35779 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35780 @var{baz}. @value{GDBN} does not transmit a space character between the
35781 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35784 @cindex @var{thread-id}, in remote protocol
35785 @anchor{thread-id syntax}
35786 Several packets and replies include a @var{thread-id} field to identify
35787 a thread. Normally these are positive numbers with a target-specific
35788 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35789 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35792 In addition, the remote protocol supports a multiprocess feature in
35793 which the @var{thread-id} syntax is extended to optionally include both
35794 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35795 The @var{pid} (process) and @var{tid} (thread) components each have the
35796 format described above: a positive number with target-specific
35797 interpretation formatted as a big-endian hex string, literal @samp{-1}
35798 to indicate all processes or threads (respectively), or @samp{0} to
35799 indicate an arbitrary process or thread. Specifying just a process, as
35800 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35801 error to specify all processes but a specific thread, such as
35802 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35803 for those packets and replies explicitly documented to include a process
35804 ID, rather than a @var{thread-id}.
35806 The multiprocess @var{thread-id} syntax extensions are only used if both
35807 @value{GDBN} and the stub report support for the @samp{multiprocess}
35808 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35811 Note that all packet forms beginning with an upper- or lower-case
35812 letter, other than those described here, are reserved for future use.
35814 Here are the packet descriptions.
35819 @cindex @samp{!} packet
35820 @anchor{extended mode}
35821 Enable extended mode. In extended mode, the remote server is made
35822 persistent. The @samp{R} packet is used to restart the program being
35828 The remote target both supports and has enabled extended mode.
35832 @cindex @samp{?} packet
35833 Indicate the reason the target halted. The reply is the same as for
35834 step and continue. This packet has a special interpretation when the
35835 target is in non-stop mode; see @ref{Remote Non-Stop}.
35838 @xref{Stop Reply Packets}, for the reply specifications.
35840 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
35841 @cindex @samp{A} packet
35842 Initialized @code{argv[]} array passed into program. @var{arglen}
35843 specifies the number of bytes in the hex encoded byte stream
35844 @var{arg}. See @code{gdbserver} for more details.
35849 The arguments were set.
35855 @cindex @samp{b} packet
35856 (Don't use this packet; its behavior is not well-defined.)
35857 Change the serial line speed to @var{baud}.
35859 JTC: @emph{When does the transport layer state change? When it's
35860 received, or after the ACK is transmitted. In either case, there are
35861 problems if the command or the acknowledgment packet is dropped.}
35863 Stan: @emph{If people really wanted to add something like this, and get
35864 it working for the first time, they ought to modify ser-unix.c to send
35865 some kind of out-of-band message to a specially-setup stub and have the
35866 switch happen "in between" packets, so that from remote protocol's point
35867 of view, nothing actually happened.}
35869 @item B @var{addr},@var{mode}
35870 @cindex @samp{B} packet
35871 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
35872 breakpoint at @var{addr}.
35874 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
35875 (@pxref{insert breakpoint or watchpoint packet}).
35877 @cindex @samp{bc} packet
35880 Backward continue. Execute the target system in reverse. No parameter.
35881 @xref{Reverse Execution}, for more information.
35884 @xref{Stop Reply Packets}, for the reply specifications.
35886 @cindex @samp{bs} packet
35889 Backward single step. Execute one instruction in reverse. No parameter.
35890 @xref{Reverse Execution}, for more information.
35893 @xref{Stop Reply Packets}, for the reply specifications.
35895 @item c @r{[}@var{addr}@r{]}
35896 @cindex @samp{c} packet
35897 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
35898 resume at current address.
35900 This packet is deprecated for multi-threading support. @xref{vCont
35904 @xref{Stop Reply Packets}, for the reply specifications.
35906 @item C @var{sig}@r{[};@var{addr}@r{]}
35907 @cindex @samp{C} packet
35908 Continue with signal @var{sig} (hex signal number). If
35909 @samp{;@var{addr}} is omitted, resume at same address.
35911 This packet is deprecated for multi-threading support. @xref{vCont
35915 @xref{Stop Reply Packets}, for the reply specifications.
35918 @cindex @samp{d} packet
35921 Don't use this packet; instead, define a general set packet
35922 (@pxref{General Query Packets}).
35926 @cindex @samp{D} packet
35927 The first form of the packet is used to detach @value{GDBN} from the
35928 remote system. It is sent to the remote target
35929 before @value{GDBN} disconnects via the @code{detach} command.
35931 The second form, including a process ID, is used when multiprocess
35932 protocol extensions are enabled (@pxref{multiprocess extensions}), to
35933 detach only a specific process. The @var{pid} is specified as a
35934 big-endian hex string.
35944 @item F @var{RC},@var{EE},@var{CF};@var{XX}
35945 @cindex @samp{F} packet
35946 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
35947 This is part of the File-I/O protocol extension. @xref{File-I/O
35948 Remote Protocol Extension}, for the specification.
35951 @anchor{read registers packet}
35952 @cindex @samp{g} packet
35953 Read general registers.
35957 @item @var{XX@dots{}}
35958 Each byte of register data is described by two hex digits. The bytes
35959 with the register are transmitted in target byte order. The size of
35960 each register and their position within the @samp{g} packet are
35961 determined by the @value{GDBN} internal gdbarch functions
35962 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
35963 specification of several standard @samp{g} packets is specified below.
35965 When reading registers from a trace frame (@pxref{Analyze Collected
35966 Data,,Using the Collected Data}), the stub may also return a string of
35967 literal @samp{x}'s in place of the register data digits, to indicate
35968 that the corresponding register has not been collected, thus its value
35969 is unavailable. For example, for an architecture with 4 registers of
35970 4 bytes each, the following reply indicates to @value{GDBN} that
35971 registers 0 and 2 have not been collected, while registers 1 and 3
35972 have been collected, and both have zero value:
35976 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
35983 @item G @var{XX@dots{}}
35984 @cindex @samp{G} packet
35985 Write general registers. @xref{read registers packet}, for a
35986 description of the @var{XX@dots{}} data.
35996 @item H @var{op} @var{thread-id}
35997 @cindex @samp{H} packet
35998 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
35999 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
36000 it should be @samp{c} for step and continue operations (note that this
36001 is deprecated, supporting the @samp{vCont} command is a better
36002 option), @samp{g} for other operations. The thread designator
36003 @var{thread-id} has the format and interpretation described in
36004 @ref{thread-id syntax}.
36015 @c 'H': How restrictive (or permissive) is the thread model. If a
36016 @c thread is selected and stopped, are other threads allowed
36017 @c to continue to execute? As I mentioned above, I think the
36018 @c semantics of each command when a thread is selected must be
36019 @c described. For example:
36021 @c 'g': If the stub supports threads and a specific thread is
36022 @c selected, returns the register block from that thread;
36023 @c otherwise returns current registers.
36025 @c 'G' If the stub supports threads and a specific thread is
36026 @c selected, sets the registers of the register block of
36027 @c that thread; otherwise sets current registers.
36029 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36030 @anchor{cycle step packet}
36031 @cindex @samp{i} packet
36032 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36033 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36034 step starting at that address.
36037 @cindex @samp{I} packet
36038 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36042 @cindex @samp{k} packet
36045 FIXME: @emph{There is no description of how to operate when a specific
36046 thread context has been selected (i.e.@: does 'k' kill only that
36049 @item m @var{addr},@var{length}
36050 @cindex @samp{m} packet
36051 Read @var{length} bytes of memory starting at address @var{addr}.
36052 Note that @var{addr} may not be aligned to any particular boundary.
36054 The stub need not use any particular size or alignment when gathering
36055 data from memory for the response; even if @var{addr} is word-aligned
36056 and @var{length} is a multiple of the word size, the stub is free to
36057 use byte accesses, or not. For this reason, this packet may not be
36058 suitable for accessing memory-mapped I/O devices.
36059 @cindex alignment of remote memory accesses
36060 @cindex size of remote memory accesses
36061 @cindex memory, alignment and size of remote accesses
36065 @item @var{XX@dots{}}
36066 Memory contents; each byte is transmitted as a two-digit hexadecimal
36067 number. The reply may contain fewer bytes than requested if the
36068 server was able to read only part of the region of memory.
36073 @item M @var{addr},@var{length}:@var{XX@dots{}}
36074 @cindex @samp{M} packet
36075 Write @var{length} bytes of memory starting at address @var{addr}.
36076 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
36077 hexadecimal number.
36084 for an error (this includes the case where only part of the data was
36089 @cindex @samp{p} packet
36090 Read the value of register @var{n}; @var{n} is in hex.
36091 @xref{read registers packet}, for a description of how the returned
36092 register value is encoded.
36096 @item @var{XX@dots{}}
36097 the register's value
36101 Indicating an unrecognized @var{query}.
36104 @item P @var{n@dots{}}=@var{r@dots{}}
36105 @anchor{write register packet}
36106 @cindex @samp{P} packet
36107 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36108 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36109 digits for each byte in the register (target byte order).
36119 @item q @var{name} @var{params}@dots{}
36120 @itemx Q @var{name} @var{params}@dots{}
36121 @cindex @samp{q} packet
36122 @cindex @samp{Q} packet
36123 General query (@samp{q}) and set (@samp{Q}). These packets are
36124 described fully in @ref{General Query Packets}.
36127 @cindex @samp{r} packet
36128 Reset the entire system.
36130 Don't use this packet; use the @samp{R} packet instead.
36133 @cindex @samp{R} packet
36134 Restart the program being debugged. @var{XX}, while needed, is ignored.
36135 This packet is only available in extended mode (@pxref{extended mode}).
36137 The @samp{R} packet has no reply.
36139 @item s @r{[}@var{addr}@r{]}
36140 @cindex @samp{s} packet
36141 Single step. @var{addr} is the address at which to resume. If
36142 @var{addr} is omitted, resume at same address.
36144 This packet is deprecated for multi-threading support. @xref{vCont
36148 @xref{Stop Reply Packets}, for the reply specifications.
36150 @item S @var{sig}@r{[};@var{addr}@r{]}
36151 @anchor{step with signal packet}
36152 @cindex @samp{S} packet
36153 Step with signal. This is analogous to the @samp{C} packet, but
36154 requests a single-step, rather than a normal resumption of execution.
36156 This packet is deprecated for multi-threading support. @xref{vCont
36160 @xref{Stop Reply Packets}, for the reply specifications.
36162 @item t @var{addr}:@var{PP},@var{MM}
36163 @cindex @samp{t} packet
36164 Search backwards starting at address @var{addr} for a match with pattern
36165 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36166 @var{addr} must be at least 3 digits.
36168 @item T @var{thread-id}
36169 @cindex @samp{T} packet
36170 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36175 thread is still alive
36181 Packets starting with @samp{v} are identified by a multi-letter name,
36182 up to the first @samp{;} or @samp{?} (or the end of the packet).
36184 @item vAttach;@var{pid}
36185 @cindex @samp{vAttach} packet
36186 Attach to a new process with the specified process ID @var{pid}.
36187 The process ID is a
36188 hexadecimal integer identifying the process. In all-stop mode, all
36189 threads in the attached process are stopped; in non-stop mode, it may be
36190 attached without being stopped if that is supported by the target.
36192 @c In non-stop mode, on a successful vAttach, the stub should set the
36193 @c current thread to a thread of the newly-attached process. After
36194 @c attaching, GDB queries for the attached process's thread ID with qC.
36195 @c Also note that, from a user perspective, whether or not the
36196 @c target is stopped on attach in non-stop mode depends on whether you
36197 @c use the foreground or background version of the attach command, not
36198 @c on what vAttach does; GDB does the right thing with respect to either
36199 @c stopping or restarting threads.
36201 This packet is only available in extended mode (@pxref{extended mode}).
36207 @item @r{Any stop packet}
36208 for success in all-stop mode (@pxref{Stop Reply Packets})
36210 for success in non-stop mode (@pxref{Remote Non-Stop})
36213 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36214 @cindex @samp{vCont} packet
36215 @anchor{vCont packet}
36216 Resume the inferior, specifying different actions for each thread.
36217 If an action is specified with no @var{thread-id}, then it is applied to any
36218 threads that don't have a specific action specified; if no default action is
36219 specified then other threads should remain stopped in all-stop mode and
36220 in their current state in non-stop mode.
36221 Specifying multiple
36222 default actions is an error; specifying no actions is also an error.
36223 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36225 Currently supported actions are:
36231 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36235 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36240 The optional argument @var{addr} normally associated with the
36241 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36242 not supported in @samp{vCont}.
36244 The @samp{t} action is only relevant in non-stop mode
36245 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36246 A stop reply should be generated for any affected thread not already stopped.
36247 When a thread is stopped by means of a @samp{t} action,
36248 the corresponding stop reply should indicate that the thread has stopped with
36249 signal @samp{0}, regardless of whether the target uses some other signal
36250 as an implementation detail.
36252 The stub must support @samp{vCont} if it reports support for
36253 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36254 this case @samp{vCont} actions can be specified to apply to all threads
36255 in a process by using the @samp{p@var{pid}.-1} form of the
36259 @xref{Stop Reply Packets}, for the reply specifications.
36262 @cindex @samp{vCont?} packet
36263 Request a list of actions supported by the @samp{vCont} packet.
36267 @item vCont@r{[};@var{action}@dots{}@r{]}
36268 The @samp{vCont} packet is supported. Each @var{action} is a supported
36269 command in the @samp{vCont} packet.
36271 The @samp{vCont} packet is not supported.
36274 @item vFile:@var{operation}:@var{parameter}@dots{}
36275 @cindex @samp{vFile} packet
36276 Perform a file operation on the target system. For details,
36277 see @ref{Host I/O Packets}.
36279 @item vFlashErase:@var{addr},@var{length}
36280 @cindex @samp{vFlashErase} packet
36281 Direct the stub to erase @var{length} bytes of flash starting at
36282 @var{addr}. The region may enclose any number of flash blocks, but
36283 its start and end must fall on block boundaries, as indicated by the
36284 flash block size appearing in the memory map (@pxref{Memory Map
36285 Format}). @value{GDBN} groups flash memory programming operations
36286 together, and sends a @samp{vFlashDone} request after each group; the
36287 stub is allowed to delay erase operation until the @samp{vFlashDone}
36288 packet is received.
36298 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36299 @cindex @samp{vFlashWrite} packet
36300 Direct the stub to write data to flash address @var{addr}. The data
36301 is passed in binary form using the same encoding as for the @samp{X}
36302 packet (@pxref{Binary Data}). The memory ranges specified by
36303 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36304 not overlap, and must appear in order of increasing addresses
36305 (although @samp{vFlashErase} packets for higher addresses may already
36306 have been received; the ordering is guaranteed only between
36307 @samp{vFlashWrite} packets). If a packet writes to an address that was
36308 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36309 target-specific method, the results are unpredictable.
36317 for vFlashWrite addressing non-flash memory
36323 @cindex @samp{vFlashDone} packet
36324 Indicate to the stub that flash programming operation is finished.
36325 The stub is permitted to delay or batch the effects of a group of
36326 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36327 @samp{vFlashDone} packet is received. The contents of the affected
36328 regions of flash memory are unpredictable until the @samp{vFlashDone}
36329 request is completed.
36331 @item vKill;@var{pid}
36332 @cindex @samp{vKill} packet
36333 Kill the process with the specified process ID. @var{pid} is a
36334 hexadecimal integer identifying the process. This packet is used in
36335 preference to @samp{k} when multiprocess protocol extensions are
36336 supported; see @ref{multiprocess extensions}.
36346 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36347 @cindex @samp{vRun} packet
36348 Run the program @var{filename}, passing it each @var{argument} on its
36349 command line. The file and arguments are hex-encoded strings. If
36350 @var{filename} is an empty string, the stub may use a default program
36351 (e.g.@: the last program run). The program is created in the stopped
36354 @c FIXME: What about non-stop mode?
36356 This packet is only available in extended mode (@pxref{extended mode}).
36362 @item @r{Any stop packet}
36363 for success (@pxref{Stop Reply Packets})
36367 @cindex @samp{vStopped} packet
36368 @xref{Notification Packets}.
36370 @item X @var{addr},@var{length}:@var{XX@dots{}}
36372 @cindex @samp{X} packet
36373 Write data to memory, where the data is transmitted in binary.
36374 @var{addr} is address, @var{length} is number of bytes,
36375 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36385 @item z @var{type},@var{addr},@var{kind}
36386 @itemx Z @var{type},@var{addr},@var{kind}
36387 @anchor{insert breakpoint or watchpoint packet}
36388 @cindex @samp{z} packet
36389 @cindex @samp{Z} packets
36390 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36391 watchpoint starting at address @var{address} of kind @var{kind}.
36393 Each breakpoint and watchpoint packet @var{type} is documented
36396 @emph{Implementation notes: A remote target shall return an empty string
36397 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36398 remote target shall support either both or neither of a given
36399 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36400 avoid potential problems with duplicate packets, the operations should
36401 be implemented in an idempotent way.}
36403 @item z0,@var{addr},@var{kind}
36404 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36405 @cindex @samp{z0} packet
36406 @cindex @samp{Z0} packet
36407 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36408 @var{addr} of type @var{kind}.
36410 A memory breakpoint is implemented by replacing the instruction at
36411 @var{addr} with a software breakpoint or trap instruction. The
36412 @var{kind} is target-specific and typically indicates the size of
36413 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36414 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36415 architectures have additional meanings for @var{kind};
36416 @var{cond_list} is an optional list of conditional expressions in bytecode
36417 form that should be evaluated on the target's side. These are the
36418 conditions that should be taken into consideration when deciding if
36419 the breakpoint trigger should be reported back to @var{GDBN}.
36421 The @var{cond_list} parameter is comprised of a series of expressions,
36422 concatenated without separators. Each expression has the following form:
36426 @item X @var{len},@var{expr}
36427 @var{len} is the length of the bytecode expression and @var{expr} is the
36428 actual conditional expression in bytecode form.
36432 The optional @var{cmd_list} parameter introduces commands that may be
36433 run on the target, rather than being reported back to @value{GDBN}.
36434 The parameter starts with a numeric flag @var{persist}; if the flag is
36435 nonzero, then the breakpoint may remain active and the commands
36436 continue to be run even when @value{GDBN} disconnects from the target.
36437 Following this flag is a series of expressions concatenated with no
36438 separators. Each expression has the following form:
36442 @item X @var{len},@var{expr}
36443 @var{len} is the length of the bytecode expression and @var{expr} is the
36444 actual conditional expression in bytecode form.
36448 see @ref{Architecture-Specific Protocol Details}.
36450 @emph{Implementation note: It is possible for a target to copy or move
36451 code that contains memory breakpoints (e.g., when implementing
36452 overlays). The behavior of this packet, in the presence of such a
36453 target, is not defined.}
36465 @item z1,@var{addr},@var{kind}
36466 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36467 @cindex @samp{z1} packet
36468 @cindex @samp{Z1} packet
36469 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36470 address @var{addr}.
36472 A hardware breakpoint is implemented using a mechanism that is not
36473 dependant on being able to modify the target's memory. @var{kind}
36474 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36476 @emph{Implementation note: A hardware breakpoint is not affected by code
36489 @item z2,@var{addr},@var{kind}
36490 @itemx Z2,@var{addr},@var{kind}
36491 @cindex @samp{z2} packet
36492 @cindex @samp{Z2} packet
36493 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36494 @var{kind} is interpreted as the number of bytes to watch.
36506 @item z3,@var{addr},@var{kind}
36507 @itemx Z3,@var{addr},@var{kind}
36508 @cindex @samp{z3} packet
36509 @cindex @samp{Z3} packet
36510 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36511 @var{kind} is interpreted as the number of bytes to watch.
36523 @item z4,@var{addr},@var{kind}
36524 @itemx Z4,@var{addr},@var{kind}
36525 @cindex @samp{z4} packet
36526 @cindex @samp{Z4} packet
36527 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36528 @var{kind} is interpreted as the number of bytes to watch.
36542 @node Stop Reply Packets
36543 @section Stop Reply Packets
36544 @cindex stop reply packets
36546 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36547 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36548 receive any of the below as a reply. Except for @samp{?}
36549 and @samp{vStopped}, that reply is only returned
36550 when the target halts. In the below the exact meaning of @dfn{signal
36551 number} is defined by the header @file{include/gdb/signals.h} in the
36552 @value{GDBN} source code.
36554 As in the description of request packets, we include spaces in the
36555 reply templates for clarity; these are not part of the reply packet's
36556 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36562 The program received signal number @var{AA} (a two-digit hexadecimal
36563 number). This is equivalent to a @samp{T} response with no
36564 @var{n}:@var{r} pairs.
36566 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36567 @cindex @samp{T} packet reply
36568 The program received signal number @var{AA} (a two-digit hexadecimal
36569 number). This is equivalent to an @samp{S} response, except that the
36570 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36571 and other information directly in the stop reply packet, reducing
36572 round-trip latency. Single-step and breakpoint traps are reported
36573 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36577 If @var{n} is a hexadecimal number, it is a register number, and the
36578 corresponding @var{r} gives that register's value. @var{r} is a
36579 series of bytes in target byte order, with each byte given by a
36580 two-digit hex number.
36583 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36584 the stopped thread, as specified in @ref{thread-id syntax}.
36587 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36588 the core on which the stop event was detected.
36591 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36592 specific event that stopped the target. The currently defined stop
36593 reasons are listed below. @var{aa} should be @samp{05}, the trap
36594 signal. At most one stop reason should be present.
36597 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36598 and go on to the next; this allows us to extend the protocol in the
36602 The currently defined stop reasons are:
36608 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36611 @cindex shared library events, remote reply
36613 The packet indicates that the loaded libraries have changed.
36614 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36615 list of loaded libraries. @var{r} is ignored.
36617 @cindex replay log events, remote reply
36619 The packet indicates that the target cannot continue replaying
36620 logged execution events, because it has reached the end (or the
36621 beginning when executing backward) of the log. The value of @var{r}
36622 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36623 for more information.
36627 @itemx W @var{AA} ; process:@var{pid}
36628 The process exited, and @var{AA} is the exit status. This is only
36629 applicable to certain targets.
36631 The second form of the response, including the process ID of the exited
36632 process, can be used only when @value{GDBN} has reported support for
36633 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36634 The @var{pid} is formatted as a big-endian hex string.
36637 @itemx X @var{AA} ; process:@var{pid}
36638 The process terminated with signal @var{AA}.
36640 The second form of the response, including the process ID of the
36641 terminated process, can be used only when @value{GDBN} has reported
36642 support for multiprocess protocol extensions; see @ref{multiprocess
36643 extensions}. The @var{pid} is formatted as a big-endian hex string.
36645 @item O @var{XX}@dots{}
36646 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36647 written as the program's console output. This can happen at any time
36648 while the program is running and the debugger should continue to wait
36649 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36651 @item F @var{call-id},@var{parameter}@dots{}
36652 @var{call-id} is the identifier which says which host system call should
36653 be called. This is just the name of the function. Translation into the
36654 correct system call is only applicable as it's defined in @value{GDBN}.
36655 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36658 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36659 this very system call.
36661 The target replies with this packet when it expects @value{GDBN} to
36662 call a host system call on behalf of the target. @value{GDBN} replies
36663 with an appropriate @samp{F} packet and keeps up waiting for the next
36664 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36665 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36666 Protocol Extension}, for more details.
36670 @node General Query Packets
36671 @section General Query Packets
36672 @cindex remote query requests
36674 Packets starting with @samp{q} are @dfn{general query packets};
36675 packets starting with @samp{Q} are @dfn{general set packets}. General
36676 query and set packets are a semi-unified form for retrieving and
36677 sending information to and from the stub.
36679 The initial letter of a query or set packet is followed by a name
36680 indicating what sort of thing the packet applies to. For example,
36681 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36682 definitions with the stub. These packet names follow some
36687 The name must not contain commas, colons or semicolons.
36689 Most @value{GDBN} query and set packets have a leading upper case
36692 The names of custom vendor packets should use a company prefix, in
36693 lower case, followed by a period. For example, packets designed at
36694 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36695 foos) or @samp{Qacme.bar} (for setting bars).
36698 The name of a query or set packet should be separated from any
36699 parameters by a @samp{:}; the parameters themselves should be
36700 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36701 full packet name, and check for a separator or the end of the packet,
36702 in case two packet names share a common prefix. New packets should not begin
36703 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36704 packets predate these conventions, and have arguments without any terminator
36705 for the packet name; we suspect they are in widespread use in places that
36706 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36707 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36710 Like the descriptions of the other packets, each description here
36711 has a template showing the packet's overall syntax, followed by an
36712 explanation of the packet's meaning. We include spaces in some of the
36713 templates for clarity; these are not part of the packet's syntax. No
36714 @value{GDBN} packet uses spaces to separate its components.
36716 Here are the currently defined query and set packets:
36722 Turn on or off the agent as a helper to perform some debugging operations
36723 delegated from @value{GDBN} (@pxref{Control Agent}).
36725 @item QAllow:@var{op}:@var{val}@dots{}
36726 @cindex @samp{QAllow} packet
36727 Specify which operations @value{GDBN} expects to request of the
36728 target, as a semicolon-separated list of operation name and value
36729 pairs. Possible values for @var{op} include @samp{WriteReg},
36730 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36731 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36732 indicating that @value{GDBN} will not request the operation, or 1,
36733 indicating that it may. (The target can then use this to set up its
36734 own internals optimally, for instance if the debugger never expects to
36735 insert breakpoints, it may not need to install its own trap handler.)
36738 @cindex current thread, remote request
36739 @cindex @samp{qC} packet
36740 Return the current thread ID.
36744 @item QC @var{thread-id}
36745 Where @var{thread-id} is a thread ID as documented in
36746 @ref{thread-id syntax}.
36747 @item @r{(anything else)}
36748 Any other reply implies the old thread ID.
36751 @item qCRC:@var{addr},@var{length}
36752 @cindex CRC of memory block, remote request
36753 @cindex @samp{qCRC} packet
36754 Compute the CRC checksum of a block of memory using CRC-32 defined in
36755 IEEE 802.3. The CRC is computed byte at a time, taking the most
36756 significant bit of each byte first. The initial pattern code
36757 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36759 @emph{Note:} This is the same CRC used in validating separate debug
36760 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36761 Files}). However the algorithm is slightly different. When validating
36762 separate debug files, the CRC is computed taking the @emph{least}
36763 significant bit of each byte first, and the final result is inverted to
36764 detect trailing zeros.
36769 An error (such as memory fault)
36770 @item C @var{crc32}
36771 The specified memory region's checksum is @var{crc32}.
36774 @item QDisableRandomization:@var{value}
36775 @cindex disable address space randomization, remote request
36776 @cindex @samp{QDisableRandomization} packet
36777 Some target operating systems will randomize the virtual address space
36778 of the inferior process as a security feature, but provide a feature
36779 to disable such randomization, e.g.@: to allow for a more deterministic
36780 debugging experience. On such systems, this packet with a @var{value}
36781 of 1 directs the target to disable address space randomization for
36782 processes subsequently started via @samp{vRun} packets, while a packet
36783 with a @var{value} of 0 tells the target to enable address space
36786 This packet is only available in extended mode (@pxref{extended mode}).
36791 The request succeeded.
36794 An error occurred. @var{nn} are hex digits.
36797 An empty reply indicates that @samp{QDisableRandomization} is not supported
36801 This packet is not probed by default; the remote stub must request it,
36802 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36803 This should only be done on targets that actually support disabling
36804 address space randomization.
36807 @itemx qsThreadInfo
36808 @cindex list active threads, remote request
36809 @cindex @samp{qfThreadInfo} packet
36810 @cindex @samp{qsThreadInfo} packet
36811 Obtain a list of all active thread IDs from the target (OS). Since there
36812 may be too many active threads to fit into one reply packet, this query
36813 works iteratively: it may require more than one query/reply sequence to
36814 obtain the entire list of threads. The first query of the sequence will
36815 be the @samp{qfThreadInfo} query; subsequent queries in the
36816 sequence will be the @samp{qsThreadInfo} query.
36818 NOTE: This packet replaces the @samp{qL} query (see below).
36822 @item m @var{thread-id}
36824 @item m @var{thread-id},@var{thread-id}@dots{}
36825 a comma-separated list of thread IDs
36827 (lower case letter @samp{L}) denotes end of list.
36830 In response to each query, the target will reply with a list of one or
36831 more thread IDs, separated by commas.
36832 @value{GDBN} will respond to each reply with a request for more thread
36833 ids (using the @samp{qs} form of the query), until the target responds
36834 with @samp{l} (lower-case ell, for @dfn{last}).
36835 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
36838 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
36839 @cindex get thread-local storage address, remote request
36840 @cindex @samp{qGetTLSAddr} packet
36841 Fetch the address associated with thread local storage specified
36842 by @var{thread-id}, @var{offset}, and @var{lm}.
36844 @var{thread-id} is the thread ID associated with the
36845 thread for which to fetch the TLS address. @xref{thread-id syntax}.
36847 @var{offset} is the (big endian, hex encoded) offset associated with the
36848 thread local variable. (This offset is obtained from the debug
36849 information associated with the variable.)
36851 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
36852 load module associated with the thread local storage. For example,
36853 a @sc{gnu}/Linux system will pass the link map address of the shared
36854 object associated with the thread local storage under consideration.
36855 Other operating environments may choose to represent the load module
36856 differently, so the precise meaning of this parameter will vary.
36860 @item @var{XX}@dots{}
36861 Hex encoded (big endian) bytes representing the address of the thread
36862 local storage requested.
36865 An error occurred. @var{nn} are hex digits.
36868 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
36871 @item qGetTIBAddr:@var{thread-id}
36872 @cindex get thread information block address
36873 @cindex @samp{qGetTIBAddr} packet
36874 Fetch address of the Windows OS specific Thread Information Block.
36876 @var{thread-id} is the thread ID associated with the thread.
36880 @item @var{XX}@dots{}
36881 Hex encoded (big endian) bytes representing the linear address of the
36882 thread information block.
36885 An error occured. This means that either the thread was not found, or the
36886 address could not be retrieved.
36889 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
36892 @item qL @var{startflag} @var{threadcount} @var{nextthread}
36893 Obtain thread information from RTOS. Where: @var{startflag} (one hex
36894 digit) is one to indicate the first query and zero to indicate a
36895 subsequent query; @var{threadcount} (two hex digits) is the maximum
36896 number of threads the response packet can contain; and @var{nextthread}
36897 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
36898 returned in the response as @var{argthread}.
36900 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
36904 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
36905 Where: @var{count} (two hex digits) is the number of threads being
36906 returned; @var{done} (one hex digit) is zero to indicate more threads
36907 and one indicates no further threads; @var{argthreadid} (eight hex
36908 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
36909 is a sequence of thread IDs from the target. @var{threadid} (eight hex
36910 digits). See @code{remote.c:parse_threadlist_response()}.
36914 @cindex section offsets, remote request
36915 @cindex @samp{qOffsets} packet
36916 Get section offsets that the target used when relocating the downloaded
36921 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
36922 Relocate the @code{Text} section by @var{xxx} from its original address.
36923 Relocate the @code{Data} section by @var{yyy} from its original address.
36924 If the object file format provides segment information (e.g.@: @sc{elf}
36925 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
36926 segments by the supplied offsets.
36928 @emph{Note: while a @code{Bss} offset may be included in the response,
36929 @value{GDBN} ignores this and instead applies the @code{Data} offset
36930 to the @code{Bss} section.}
36932 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
36933 Relocate the first segment of the object file, which conventionally
36934 contains program code, to a starting address of @var{xxx}. If
36935 @samp{DataSeg} is specified, relocate the second segment, which
36936 conventionally contains modifiable data, to a starting address of
36937 @var{yyy}. @value{GDBN} will report an error if the object file
36938 does not contain segment information, or does not contain at least
36939 as many segments as mentioned in the reply. Extra segments are
36940 kept at fixed offsets relative to the last relocated segment.
36943 @item qP @var{mode} @var{thread-id}
36944 @cindex thread information, remote request
36945 @cindex @samp{qP} packet
36946 Returns information on @var{thread-id}. Where: @var{mode} is a hex
36947 encoded 32 bit mode; @var{thread-id} is a thread ID
36948 (@pxref{thread-id syntax}).
36950 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
36953 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
36957 @cindex non-stop mode, remote request
36958 @cindex @samp{QNonStop} packet
36960 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
36961 @xref{Remote Non-Stop}, for more information.
36966 The request succeeded.
36969 An error occurred. @var{nn} are hex digits.
36972 An empty reply indicates that @samp{QNonStop} is not supported by
36976 This packet is not probed by default; the remote stub must request it,
36977 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36978 Use of this packet is controlled by the @code{set non-stop} command;
36979 @pxref{Non-Stop Mode}.
36981 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
36982 @cindex pass signals to inferior, remote request
36983 @cindex @samp{QPassSignals} packet
36984 @anchor{QPassSignals}
36985 Each listed @var{signal} should be passed directly to the inferior process.
36986 Signals are numbered identically to continue packets and stop replies
36987 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
36988 strictly greater than the previous item. These signals do not need to stop
36989 the inferior, or be reported to @value{GDBN}. All other signals should be
36990 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
36991 combine; any earlier @samp{QPassSignals} list is completely replaced by the
36992 new list. This packet improves performance when using @samp{handle
36993 @var{signal} nostop noprint pass}.
36998 The request succeeded.
37001 An error occurred. @var{nn} are hex digits.
37004 An empty reply indicates that @samp{QPassSignals} is not supported by
37008 Use of this packet is controlled by the @code{set remote pass-signals}
37009 command (@pxref{Remote Configuration, set remote pass-signals}).
37010 This packet is not probed by default; the remote stub must request it,
37011 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37013 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37014 @cindex signals the inferior may see, remote request
37015 @cindex @samp{QProgramSignals} packet
37016 @anchor{QProgramSignals}
37017 Each listed @var{signal} may be delivered to the inferior process.
37018 Others should be silently discarded.
37020 In some cases, the remote stub may need to decide whether to deliver a
37021 signal to the program or not without @value{GDBN} involvement. One
37022 example of that is while detaching --- the program's threads may have
37023 stopped for signals that haven't yet had a chance of being reported to
37024 @value{GDBN}, and so the remote stub can use the signal list specified
37025 by this packet to know whether to deliver or ignore those pending
37028 This does not influence whether to deliver a signal as requested by a
37029 resumption packet (@pxref{vCont packet}).
37031 Signals are numbered identically to continue packets and stop replies
37032 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37033 strictly greater than the previous item. Multiple
37034 @samp{QProgramSignals} packets do not combine; any earlier
37035 @samp{QProgramSignals} list is completely replaced by the new list.
37040 The request succeeded.
37043 An error occurred. @var{nn} are hex digits.
37046 An empty reply indicates that @samp{QProgramSignals} is not supported
37050 Use of this packet is controlled by the @code{set remote program-signals}
37051 command (@pxref{Remote Configuration, set remote program-signals}).
37052 This packet is not probed by default; the remote stub must request it,
37053 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37055 @item qRcmd,@var{command}
37056 @cindex execute remote command, remote request
37057 @cindex @samp{qRcmd} packet
37058 @var{command} (hex encoded) is passed to the local interpreter for
37059 execution. Invalid commands should be reported using the output
37060 string. Before the final result packet, the target may also respond
37061 with a number of intermediate @samp{O@var{output}} console output
37062 packets. @emph{Implementors should note that providing access to a
37063 stubs's interpreter may have security implications}.
37068 A command response with no output.
37070 A command response with the hex encoded output string @var{OUTPUT}.
37072 Indicate a badly formed request.
37074 An empty reply indicates that @samp{qRcmd} is not recognized.
37077 (Note that the @code{qRcmd} packet's name is separated from the
37078 command by a @samp{,}, not a @samp{:}, contrary to the naming
37079 conventions above. Please don't use this packet as a model for new
37082 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37083 @cindex searching memory, in remote debugging
37084 @cindex @samp{qSearch:memory} packet
37085 @anchor{qSearch memory}
37086 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37087 @var{address} and @var{length} are encoded in hex.
37088 @var{search-pattern} is a sequence of bytes, hex encoded.
37093 The pattern was not found.
37095 The pattern was found at @var{address}.
37097 A badly formed request or an error was encountered while searching memory.
37099 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37102 @item QStartNoAckMode
37103 @cindex @samp{QStartNoAckMode} packet
37104 @anchor{QStartNoAckMode}
37105 Request that the remote stub disable the normal @samp{+}/@samp{-}
37106 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37111 The stub has switched to no-acknowledgment mode.
37112 @value{GDBN} acknowledges this reponse,
37113 but neither the stub nor @value{GDBN} shall send or expect further
37114 @samp{+}/@samp{-} acknowledgments in the current connection.
37116 An empty reply indicates that the stub does not support no-acknowledgment mode.
37119 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37120 @cindex supported packets, remote query
37121 @cindex features of the remote protocol
37122 @cindex @samp{qSupported} packet
37123 @anchor{qSupported}
37124 Tell the remote stub about features supported by @value{GDBN}, and
37125 query the stub for features it supports. This packet allows
37126 @value{GDBN} and the remote stub to take advantage of each others'
37127 features. @samp{qSupported} also consolidates multiple feature probes
37128 at startup, to improve @value{GDBN} performance---a single larger
37129 packet performs better than multiple smaller probe packets on
37130 high-latency links. Some features may enable behavior which must not
37131 be on by default, e.g.@: because it would confuse older clients or
37132 stubs. Other features may describe packets which could be
37133 automatically probed for, but are not. These features must be
37134 reported before @value{GDBN} will use them. This ``default
37135 unsupported'' behavior is not appropriate for all packets, but it
37136 helps to keep the initial connection time under control with new
37137 versions of @value{GDBN} which support increasing numbers of packets.
37141 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37142 The stub supports or does not support each returned @var{stubfeature},
37143 depending on the form of each @var{stubfeature} (see below for the
37146 An empty reply indicates that @samp{qSupported} is not recognized,
37147 or that no features needed to be reported to @value{GDBN}.
37150 The allowed forms for each feature (either a @var{gdbfeature} in the
37151 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37155 @item @var{name}=@var{value}
37156 The remote protocol feature @var{name} is supported, and associated
37157 with the specified @var{value}. The format of @var{value} depends
37158 on the feature, but it must not include a semicolon.
37160 The remote protocol feature @var{name} is supported, and does not
37161 need an associated value.
37163 The remote protocol feature @var{name} is not supported.
37165 The remote protocol feature @var{name} may be supported, and
37166 @value{GDBN} should auto-detect support in some other way when it is
37167 needed. This form will not be used for @var{gdbfeature} notifications,
37168 but may be used for @var{stubfeature} responses.
37171 Whenever the stub receives a @samp{qSupported} request, the
37172 supplied set of @value{GDBN} features should override any previous
37173 request. This allows @value{GDBN} to put the stub in a known
37174 state, even if the stub had previously been communicating with
37175 a different version of @value{GDBN}.
37177 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37182 This feature indicates whether @value{GDBN} supports multiprocess
37183 extensions to the remote protocol. @value{GDBN} does not use such
37184 extensions unless the stub also reports that it supports them by
37185 including @samp{multiprocess+} in its @samp{qSupported} reply.
37186 @xref{multiprocess extensions}, for details.
37189 This feature indicates that @value{GDBN} supports the XML target
37190 description. If the stub sees @samp{xmlRegisters=} with target
37191 specific strings separated by a comma, it will report register
37195 This feature indicates whether @value{GDBN} supports the
37196 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37197 instruction reply packet}).
37200 Stubs should ignore any unknown values for
37201 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37202 packet supports receiving packets of unlimited length (earlier
37203 versions of @value{GDBN} may reject overly long responses). Additional values
37204 for @var{gdbfeature} may be defined in the future to let the stub take
37205 advantage of new features in @value{GDBN}, e.g.@: incompatible
37206 improvements in the remote protocol---the @samp{multiprocess} feature is
37207 an example of such a feature. The stub's reply should be independent
37208 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37209 describes all the features it supports, and then the stub replies with
37210 all the features it supports.
37212 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37213 responses, as long as each response uses one of the standard forms.
37215 Some features are flags. A stub which supports a flag feature
37216 should respond with a @samp{+} form response. Other features
37217 require values, and the stub should respond with an @samp{=}
37220 Each feature has a default value, which @value{GDBN} will use if
37221 @samp{qSupported} is not available or if the feature is not mentioned
37222 in the @samp{qSupported} response. The default values are fixed; a
37223 stub is free to omit any feature responses that match the defaults.
37225 Not all features can be probed, but for those which can, the probing
37226 mechanism is useful: in some cases, a stub's internal
37227 architecture may not allow the protocol layer to know some information
37228 about the underlying target in advance. This is especially common in
37229 stubs which may be configured for multiple targets.
37231 These are the currently defined stub features and their properties:
37233 @multitable @columnfractions 0.35 0.2 0.12 0.2
37234 @c NOTE: The first row should be @headitem, but we do not yet require
37235 @c a new enough version of Texinfo (4.7) to use @headitem.
37237 @tab Value Required
37241 @item @samp{PacketSize}
37246 @item @samp{qXfer:auxv:read}
37251 @item @samp{qXfer:features:read}
37256 @item @samp{qXfer:libraries:read}
37261 @item @samp{qXfer:memory-map:read}
37266 @item @samp{qXfer:sdata:read}
37271 @item @samp{qXfer:spu:read}
37276 @item @samp{qXfer:spu:write}
37281 @item @samp{qXfer:siginfo:read}
37286 @item @samp{qXfer:siginfo:write}
37291 @item @samp{qXfer:threads:read}
37296 @item @samp{qXfer:traceframe-info:read}
37301 @item @samp{qXfer:uib:read}
37306 @item @samp{qXfer:fdpic:read}
37311 @item @samp{QNonStop}
37316 @item @samp{QPassSignals}
37321 @item @samp{QStartNoAckMode}
37326 @item @samp{multiprocess}
37331 @item @samp{ConditionalBreakpoints}
37336 @item @samp{ConditionalTracepoints}
37341 @item @samp{ReverseContinue}
37346 @item @samp{ReverseStep}
37351 @item @samp{TracepointSource}
37356 @item @samp{QAgent}
37361 @item @samp{QAllow}
37366 @item @samp{QDisableRandomization}
37371 @item @samp{EnableDisableTracepoints}
37376 @item @samp{tracenz}
37381 @item @samp{BreakpointCommands}
37388 These are the currently defined stub features, in more detail:
37391 @cindex packet size, remote protocol
37392 @item PacketSize=@var{bytes}
37393 The remote stub can accept packets up to at least @var{bytes} in
37394 length. @value{GDBN} will send packets up to this size for bulk
37395 transfers, and will never send larger packets. This is a limit on the
37396 data characters in the packet, including the frame and checksum.
37397 There is no trailing NUL byte in a remote protocol packet; if the stub
37398 stores packets in a NUL-terminated format, it should allow an extra
37399 byte in its buffer for the NUL. If this stub feature is not supported,
37400 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37402 @item qXfer:auxv:read
37403 The remote stub understands the @samp{qXfer:auxv:read} packet
37404 (@pxref{qXfer auxiliary vector read}).
37406 @item qXfer:features:read
37407 The remote stub understands the @samp{qXfer:features:read} packet
37408 (@pxref{qXfer target description read}).
37410 @item qXfer:libraries:read
37411 The remote stub understands the @samp{qXfer:libraries:read} packet
37412 (@pxref{qXfer library list read}).
37414 @item qXfer:libraries-svr4:read
37415 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37416 (@pxref{qXfer svr4 library list read}).
37418 @item qXfer:memory-map:read
37419 The remote stub understands the @samp{qXfer:memory-map:read} packet
37420 (@pxref{qXfer memory map read}).
37422 @item qXfer:sdata:read
37423 The remote stub understands the @samp{qXfer:sdata:read} packet
37424 (@pxref{qXfer sdata read}).
37426 @item qXfer:spu:read
37427 The remote stub understands the @samp{qXfer:spu:read} packet
37428 (@pxref{qXfer spu read}).
37430 @item qXfer:spu:write
37431 The remote stub understands the @samp{qXfer:spu:write} packet
37432 (@pxref{qXfer spu write}).
37434 @item qXfer:siginfo:read
37435 The remote stub understands the @samp{qXfer:siginfo:read} packet
37436 (@pxref{qXfer siginfo read}).
37438 @item qXfer:siginfo:write
37439 The remote stub understands the @samp{qXfer:siginfo:write} packet
37440 (@pxref{qXfer siginfo write}).
37442 @item qXfer:threads:read
37443 The remote stub understands the @samp{qXfer:threads:read} packet
37444 (@pxref{qXfer threads read}).
37446 @item qXfer:traceframe-info:read
37447 The remote stub understands the @samp{qXfer:traceframe-info:read}
37448 packet (@pxref{qXfer traceframe info read}).
37450 @item qXfer:uib:read
37451 The remote stub understands the @samp{qXfer:uib:read}
37452 packet (@pxref{qXfer unwind info block}).
37454 @item qXfer:fdpic:read
37455 The remote stub understands the @samp{qXfer:fdpic:read}
37456 packet (@pxref{qXfer fdpic loadmap read}).
37459 The remote stub understands the @samp{QNonStop} packet
37460 (@pxref{QNonStop}).
37463 The remote stub understands the @samp{QPassSignals} packet
37464 (@pxref{QPassSignals}).
37466 @item QStartNoAckMode
37467 The remote stub understands the @samp{QStartNoAckMode} packet and
37468 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37471 @anchor{multiprocess extensions}
37472 @cindex multiprocess extensions, in remote protocol
37473 The remote stub understands the multiprocess extensions to the remote
37474 protocol syntax. The multiprocess extensions affect the syntax of
37475 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37476 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37477 replies. Note that reporting this feature indicates support for the
37478 syntactic extensions only, not that the stub necessarily supports
37479 debugging of more than one process at a time. The stub must not use
37480 multiprocess extensions in packet replies unless @value{GDBN} has also
37481 indicated it supports them in its @samp{qSupported} request.
37483 @item qXfer:osdata:read
37484 The remote stub understands the @samp{qXfer:osdata:read} packet
37485 ((@pxref{qXfer osdata read}).
37487 @item ConditionalBreakpoints
37488 The target accepts and implements evaluation of conditional expressions
37489 defined for breakpoints. The target will only report breakpoint triggers
37490 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37492 @item ConditionalTracepoints
37493 The remote stub accepts and implements conditional expressions defined
37494 for tracepoints (@pxref{Tracepoint Conditions}).
37496 @item ReverseContinue
37497 The remote stub accepts and implements the reverse continue packet
37501 The remote stub accepts and implements the reverse step packet
37504 @item TracepointSource
37505 The remote stub understands the @samp{QTDPsrc} packet that supplies
37506 the source form of tracepoint definitions.
37509 The remote stub understands the @samp{QAgent} packet.
37512 The remote stub understands the @samp{QAllow} packet.
37514 @item QDisableRandomization
37515 The remote stub understands the @samp{QDisableRandomization} packet.
37517 @item StaticTracepoint
37518 @cindex static tracepoints, in remote protocol
37519 The remote stub supports static tracepoints.
37521 @item InstallInTrace
37522 @anchor{install tracepoint in tracing}
37523 The remote stub supports installing tracepoint in tracing.
37525 @item EnableDisableTracepoints
37526 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37527 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37528 to be enabled and disabled while a trace experiment is running.
37531 @cindex string tracing, in remote protocol
37532 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37533 See @ref{Bytecode Descriptions} for details about the bytecode.
37535 @item BreakpointCommands
37536 @cindex breakpoint commands, in remote protocol
37537 The remote stub supports running a breakpoint's command list itself,
37538 rather than reporting the hit to @value{GDBN}.
37543 @cindex symbol lookup, remote request
37544 @cindex @samp{qSymbol} packet
37545 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37546 requests. Accept requests from the target for the values of symbols.
37551 The target does not need to look up any (more) symbols.
37552 @item qSymbol:@var{sym_name}
37553 The target requests the value of symbol @var{sym_name} (hex encoded).
37554 @value{GDBN} may provide the value by using the
37555 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37559 @item qSymbol:@var{sym_value}:@var{sym_name}
37560 Set the value of @var{sym_name} to @var{sym_value}.
37562 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37563 target has previously requested.
37565 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37566 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37572 The target does not need to look up any (more) symbols.
37573 @item qSymbol:@var{sym_name}
37574 The target requests the value of a new symbol @var{sym_name} (hex
37575 encoded). @value{GDBN} will continue to supply the values of symbols
37576 (if available), until the target ceases to request them.
37581 @itemx QTDisconnected
37588 @itemx qTMinFTPILen
37590 @xref{Tracepoint Packets}.
37592 @item qThreadExtraInfo,@var{thread-id}
37593 @cindex thread attributes info, remote request
37594 @cindex @samp{qThreadExtraInfo} packet
37595 Obtain a printable string description of a thread's attributes from
37596 the target OS. @var{thread-id} is a thread ID;
37597 see @ref{thread-id syntax}. This
37598 string may contain anything that the target OS thinks is interesting
37599 for @value{GDBN} to tell the user about the thread. The string is
37600 displayed in @value{GDBN}'s @code{info threads} display. Some
37601 examples of possible thread extra info strings are @samp{Runnable}, or
37602 @samp{Blocked on Mutex}.
37606 @item @var{XX}@dots{}
37607 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37608 comprising the printable string containing the extra information about
37609 the thread's attributes.
37612 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37613 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37614 conventions above. Please don't use this packet as a model for new
37633 @xref{Tracepoint Packets}.
37635 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37636 @cindex read special object, remote request
37637 @cindex @samp{qXfer} packet
37638 @anchor{qXfer read}
37639 Read uninterpreted bytes from the target's special data area
37640 identified by the keyword @var{object}. Request @var{length} bytes
37641 starting at @var{offset} bytes into the data. The content and
37642 encoding of @var{annex} is specific to @var{object}; it can supply
37643 additional details about what data to access.
37645 Here are the specific requests of this form defined so far. All
37646 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37647 formats, listed below.
37650 @item qXfer:auxv:read::@var{offset},@var{length}
37651 @anchor{qXfer auxiliary vector read}
37652 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37653 auxiliary vector}. Note @var{annex} must be empty.
37655 This packet is not probed by default; the remote stub must request it,
37656 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37658 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37659 @anchor{qXfer target description read}
37660 Access the @dfn{target description}. @xref{Target Descriptions}. The
37661 annex specifies which XML document to access. The main description is
37662 always loaded from the @samp{target.xml} annex.
37664 This packet is not probed by default; the remote stub must request it,
37665 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37667 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37668 @anchor{qXfer library list read}
37669 Access the target's list of loaded libraries. @xref{Library List Format}.
37670 The annex part of the generic @samp{qXfer} packet must be empty
37671 (@pxref{qXfer read}).
37673 Targets which maintain a list of libraries in the program's memory do
37674 not need to implement this packet; it is designed for platforms where
37675 the operating system manages the list of loaded libraries.
37677 This packet is not probed by default; the remote stub must request it,
37678 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37680 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37681 @anchor{qXfer svr4 library list read}
37682 Access the target's list of loaded libraries when the target is an SVR4
37683 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37684 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37686 This packet is optional for better performance on SVR4 targets.
37687 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37689 This packet is not probed by default; the remote stub must request it,
37690 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37692 @item qXfer:memory-map:read::@var{offset},@var{length}
37693 @anchor{qXfer memory map read}
37694 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37695 annex part of the generic @samp{qXfer} packet must be empty
37696 (@pxref{qXfer read}).
37698 This packet is not probed by default; the remote stub must request it,
37699 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37701 @item qXfer:sdata:read::@var{offset},@var{length}
37702 @anchor{qXfer sdata read}
37704 Read contents of the extra collected static tracepoint marker
37705 information. The annex part of the generic @samp{qXfer} packet must
37706 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37709 This packet is not probed by default; the remote stub must request it,
37710 by supplying an appropriate @samp{qSupported} response
37711 (@pxref{qSupported}).
37713 @item qXfer:siginfo:read::@var{offset},@var{length}
37714 @anchor{qXfer siginfo read}
37715 Read contents of the extra signal information on the target
37716 system. The annex part of the generic @samp{qXfer} packet must be
37717 empty (@pxref{qXfer read}).
37719 This packet is not probed by default; the remote stub must request it,
37720 by supplying an appropriate @samp{qSupported} response
37721 (@pxref{qSupported}).
37723 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37724 @anchor{qXfer spu read}
37725 Read contents of an @code{spufs} file on the target system. The
37726 annex specifies which file to read; it must be of the form
37727 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37728 in the target process, and @var{name} identifes the @code{spufs} file
37729 in that context to be accessed.
37731 This packet is not probed by default; the remote stub must request it,
37732 by supplying an appropriate @samp{qSupported} response
37733 (@pxref{qSupported}).
37735 @item qXfer:threads:read::@var{offset},@var{length}
37736 @anchor{qXfer threads read}
37737 Access the list of threads on target. @xref{Thread List Format}. The
37738 annex part of the generic @samp{qXfer} packet must be empty
37739 (@pxref{qXfer read}).
37741 This packet is not probed by default; the remote stub must request it,
37742 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37744 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37745 @anchor{qXfer traceframe info read}
37747 Return a description of the current traceframe's contents.
37748 @xref{Traceframe Info Format}. The annex part of the generic
37749 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37751 This packet is not probed by default; the remote stub must request it,
37752 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37754 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37755 @anchor{qXfer unwind info block}
37757 Return the unwind information block for @var{pc}. This packet is used
37758 on OpenVMS/ia64 to ask the kernel unwind information.
37760 This packet is not probed by default.
37762 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37763 @anchor{qXfer fdpic loadmap read}
37764 Read contents of @code{loadmap}s on the target system. The
37765 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37766 executable @code{loadmap} or interpreter @code{loadmap} to read.
37768 This packet is not probed by default; the remote stub must request it,
37769 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37771 @item qXfer:osdata:read::@var{offset},@var{length}
37772 @anchor{qXfer osdata read}
37773 Access the target's @dfn{operating system information}.
37774 @xref{Operating System Information}.
37781 Data @var{data} (@pxref{Binary Data}) has been read from the
37782 target. There may be more data at a higher address (although
37783 it is permitted to return @samp{m} even for the last valid
37784 block of data, as long as at least one byte of data was read).
37785 @var{data} may have fewer bytes than the @var{length} in the
37789 Data @var{data} (@pxref{Binary Data}) has been read from the target.
37790 There is no more data to be read. @var{data} may have fewer bytes
37791 than the @var{length} in the request.
37794 The @var{offset} in the request is at the end of the data.
37795 There is no more data to be read.
37798 The request was malformed, or @var{annex} was invalid.
37801 The offset was invalid, or there was an error encountered reading the data.
37802 @var{nn} is a hex-encoded @code{errno} value.
37805 An empty reply indicates the @var{object} string was not recognized by
37806 the stub, or that the object does not support reading.
37809 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
37810 @cindex write data into object, remote request
37811 @anchor{qXfer write}
37812 Write uninterpreted bytes into the target's special data area
37813 identified by the keyword @var{object}, starting at @var{offset} bytes
37814 into the data. @var{data}@dots{} is the binary-encoded data
37815 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
37816 is specific to @var{object}; it can supply additional details about what data
37819 Here are the specific requests of this form defined so far. All
37820 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
37821 formats, listed below.
37824 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
37825 @anchor{qXfer siginfo write}
37826 Write @var{data} to the extra signal information on the target system.
37827 The annex part of the generic @samp{qXfer} packet must be
37828 empty (@pxref{qXfer write}).
37830 This packet is not probed by default; the remote stub must request it,
37831 by supplying an appropriate @samp{qSupported} response
37832 (@pxref{qSupported}).
37834 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
37835 @anchor{qXfer spu write}
37836 Write @var{data} to an @code{spufs} file on the target system. The
37837 annex specifies which file to write; it must be of the form
37838 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37839 in the target process, and @var{name} identifes the @code{spufs} file
37840 in that context to be accessed.
37842 This packet is not probed by default; the remote stub must request it,
37843 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37849 @var{nn} (hex encoded) is the number of bytes written.
37850 This may be fewer bytes than supplied in the request.
37853 The request was malformed, or @var{annex} was invalid.
37856 The offset was invalid, or there was an error encountered writing the data.
37857 @var{nn} is a hex-encoded @code{errno} value.
37860 An empty reply indicates the @var{object} string was not
37861 recognized by the stub, or that the object does not support writing.
37864 @item qXfer:@var{object}:@var{operation}:@dots{}
37865 Requests of this form may be added in the future. When a stub does
37866 not recognize the @var{object} keyword, or its support for
37867 @var{object} does not recognize the @var{operation} keyword, the stub
37868 must respond with an empty packet.
37870 @item qAttached:@var{pid}
37871 @cindex query attached, remote request
37872 @cindex @samp{qAttached} packet
37873 Return an indication of whether the remote server attached to an
37874 existing process or created a new process. When the multiprocess
37875 protocol extensions are supported (@pxref{multiprocess extensions}),
37876 @var{pid} is an integer in hexadecimal format identifying the target
37877 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
37878 the query packet will be simplified as @samp{qAttached}.
37880 This query is used, for example, to know whether the remote process
37881 should be detached or killed when a @value{GDBN} session is ended with
37882 the @code{quit} command.
37887 The remote server attached to an existing process.
37889 The remote server created a new process.
37891 A badly formed request or an error was encountered.
37896 @node Architecture-Specific Protocol Details
37897 @section Architecture-Specific Protocol Details
37899 This section describes how the remote protocol is applied to specific
37900 target architectures. Also see @ref{Standard Target Features}, for
37901 details of XML target descriptions for each architecture.
37904 * ARM-Specific Protocol Details::
37905 * MIPS-Specific Protocol Details::
37908 @node ARM-Specific Protocol Details
37909 @subsection @acronym{ARM}-specific Protocol Details
37912 * ARM Breakpoint Kinds::
37915 @node ARM Breakpoint Kinds
37916 @subsubsection @acronym{ARM} Breakpoint Kinds
37917 @cindex breakpoint kinds, @acronym{ARM}
37919 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37924 16-bit Thumb mode breakpoint.
37927 32-bit Thumb mode (Thumb-2) breakpoint.
37930 32-bit @acronym{ARM} mode breakpoint.
37934 @node MIPS-Specific Protocol Details
37935 @subsection @acronym{MIPS}-specific Protocol Details
37938 * MIPS Register packet Format::
37939 * MIPS Breakpoint Kinds::
37942 @node MIPS Register packet Format
37943 @subsubsection @acronym{MIPS} Register Packet Format
37944 @cindex register packet format, @acronym{MIPS}
37946 The following @code{g}/@code{G} packets have previously been defined.
37947 In the below, some thirty-two bit registers are transferred as
37948 sixty-four bits. Those registers should be zero/sign extended (which?)
37949 to fill the space allocated. Register bytes are transferred in target
37950 byte order. The two nibbles within a register byte are transferred
37951 most-significant -- least-significant.
37956 All registers are transferred as thirty-two bit quantities in the order:
37957 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
37958 registers; fsr; fir; fp.
37961 All registers are transferred as sixty-four bit quantities (including
37962 thirty-two bit registers such as @code{sr}). The ordering is the same
37967 @node MIPS Breakpoint Kinds
37968 @subsubsection @acronym{MIPS} Breakpoint Kinds
37969 @cindex breakpoint kinds, @acronym{MIPS}
37971 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
37976 16-bit @acronym{MIPS16} mode breakpoint.
37979 16-bit @acronym{microMIPS} mode breakpoint.
37982 32-bit standard @acronym{MIPS} mode breakpoint.
37985 32-bit @acronym{microMIPS} mode breakpoint.
37989 @node Tracepoint Packets
37990 @section Tracepoint Packets
37991 @cindex tracepoint packets
37992 @cindex packets, tracepoint
37994 Here we describe the packets @value{GDBN} uses to implement
37995 tracepoints (@pxref{Tracepoints}).
37999 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38000 @cindex @samp{QTDP} packet
38001 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38002 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38003 the tracepoint is disabled. @var{step} is the tracepoint's step
38004 count, and @var{pass} is its pass count. If an @samp{F} is present,
38005 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38006 the number of bytes that the target should copy elsewhere to make room
38007 for the tracepoint. If an @samp{X} is present, it introduces a
38008 tracepoint condition, which consists of a hexadecimal length, followed
38009 by a comma and hex-encoded bytes, in a manner similar to action
38010 encodings as described below. If the trailing @samp{-} is present,
38011 further @samp{QTDP} packets will follow to specify this tracepoint's
38017 The packet was understood and carried out.
38019 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38021 The packet was not recognized.
38024 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38025 Define actions to be taken when a tracepoint is hit. @var{n} and
38026 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38027 this tracepoint. This packet may only be sent immediately after
38028 another @samp{QTDP} packet that ended with a @samp{-}. If the
38029 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38030 specifying more actions for this tracepoint.
38032 In the series of action packets for a given tracepoint, at most one
38033 can have an @samp{S} before its first @var{action}. If such a packet
38034 is sent, it and the following packets define ``while-stepping''
38035 actions. Any prior packets define ordinary actions --- that is, those
38036 taken when the tracepoint is first hit. If no action packet has an
38037 @samp{S}, then all the packets in the series specify ordinary
38038 tracepoint actions.
38040 The @samp{@var{action}@dots{}} portion of the packet is a series of
38041 actions, concatenated without separators. Each action has one of the
38047 Collect the registers whose bits are set in @var{mask}. @var{mask} is
38048 a hexadecimal number whose @var{i}'th bit is set if register number
38049 @var{i} should be collected. (The least significant bit is numbered
38050 zero.) Note that @var{mask} may be any number of digits long; it may
38051 not fit in a 32-bit word.
38053 @item M @var{basereg},@var{offset},@var{len}
38054 Collect @var{len} bytes of memory starting at the address in register
38055 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38056 @samp{-1}, then the range has a fixed address: @var{offset} is the
38057 address of the lowest byte to collect. The @var{basereg},
38058 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38059 values (the @samp{-1} value for @var{basereg} is a special case).
38061 @item X @var{len},@var{expr}
38062 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38063 it directs. @var{expr} is an agent expression, as described in
38064 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38065 two-digit hex number in the packet; @var{len} is the number of bytes
38066 in the expression (and thus one-half the number of hex digits in the
38071 Any number of actions may be packed together in a single @samp{QTDP}
38072 packet, as long as the packet does not exceed the maximum packet
38073 length (400 bytes, for many stubs). There may be only one @samp{R}
38074 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38075 actions. Any registers referred to by @samp{M} and @samp{X} actions
38076 must be collected by a preceding @samp{R} action. (The
38077 ``while-stepping'' actions are treated as if they were attached to a
38078 separate tracepoint, as far as these restrictions are concerned.)
38083 The packet was understood and carried out.
38085 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38087 The packet was not recognized.
38090 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38091 @cindex @samp{QTDPsrc} packet
38092 Specify a source string of tracepoint @var{n} at address @var{addr}.
38093 This is useful to get accurate reproduction of the tracepoints
38094 originally downloaded at the beginning of the trace run. @var{type}
38095 is the name of the tracepoint part, such as @samp{cond} for the
38096 tracepoint's conditional expression (see below for a list of types), while
38097 @var{bytes} is the string, encoded in hexadecimal.
38099 @var{start} is the offset of the @var{bytes} within the overall source
38100 string, while @var{slen} is the total length of the source string.
38101 This is intended for handling source strings that are longer than will
38102 fit in a single packet.
38103 @c Add detailed example when this info is moved into a dedicated
38104 @c tracepoint descriptions section.
38106 The available string types are @samp{at} for the location,
38107 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38108 @value{GDBN} sends a separate packet for each command in the action
38109 list, in the same order in which the commands are stored in the list.
38111 The target does not need to do anything with source strings except
38112 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38115 Although this packet is optional, and @value{GDBN} will only send it
38116 if the target replies with @samp{TracepointSource} @xref{General
38117 Query Packets}, it makes both disconnected tracing and trace files
38118 much easier to use. Otherwise the user must be careful that the
38119 tracepoints in effect while looking at trace frames are identical to
38120 the ones in effect during the trace run; even a small discrepancy
38121 could cause @samp{tdump} not to work, or a particular trace frame not
38124 @item QTDV:@var{n}:@var{value}
38125 @cindex define trace state variable, remote request
38126 @cindex @samp{QTDV} packet
38127 Create a new trace state variable, number @var{n}, with an initial
38128 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38129 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38130 the option of not using this packet for initial values of zero; the
38131 target should simply create the trace state variables as they are
38132 mentioned in expressions.
38134 @item QTFrame:@var{n}
38135 @cindex @samp{QTFrame} packet
38136 Select the @var{n}'th tracepoint frame from the buffer, and use the
38137 register and memory contents recorded there to answer subsequent
38138 request packets from @value{GDBN}.
38140 A successful reply from the stub indicates that the stub has found the
38141 requested frame. The response is a series of parts, concatenated
38142 without separators, describing the frame we selected. Each part has
38143 one of the following forms:
38147 The selected frame is number @var{n} in the trace frame buffer;
38148 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38149 was no frame matching the criteria in the request packet.
38152 The selected trace frame records a hit of tracepoint number @var{t};
38153 @var{t} is a hexadecimal number.
38157 @item QTFrame:pc:@var{addr}
38158 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38159 currently selected frame whose PC is @var{addr};
38160 @var{addr} is a hexadecimal number.
38162 @item QTFrame:tdp:@var{t}
38163 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38164 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38165 is a hexadecimal number.
38167 @item QTFrame:range:@var{start}:@var{end}
38168 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38169 currently selected frame whose PC is between @var{start} (inclusive)
38170 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38173 @item QTFrame:outside:@var{start}:@var{end}
38174 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38175 frame @emph{outside} the given range of addresses (exclusive).
38178 @cindex @samp{qTMinFTPILen} packet
38179 This packet requests the minimum length of instruction at which a fast
38180 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38181 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38182 it depends on the target system being able to create trampolines in
38183 the first 64K of memory, which might or might not be possible for that
38184 system. So the reply to this packet will be 4 if it is able to
38191 The minimum instruction length is currently unknown.
38193 The minimum instruction length is @var{length}, where @var{length} is greater
38194 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38195 that a fast tracepoint may be placed on any instruction regardless of size.
38197 An error has occurred.
38199 An empty reply indicates that the request is not supported by the stub.
38203 @cindex @samp{QTStart} packet
38204 Begin the tracepoint experiment. Begin collecting data from
38205 tracepoint hits in the trace frame buffer. This packet supports the
38206 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38207 instruction reply packet}).
38210 @cindex @samp{QTStop} packet
38211 End the tracepoint experiment. Stop collecting trace frames.
38213 @item QTEnable:@var{n}:@var{addr}
38215 @cindex @samp{QTEnable} packet
38216 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38217 experiment. If the tracepoint was previously disabled, then collection
38218 of data from it will resume.
38220 @item QTDisable:@var{n}:@var{addr}
38222 @cindex @samp{QTDisable} packet
38223 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38224 experiment. No more data will be collected from the tracepoint unless
38225 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38228 @cindex @samp{QTinit} packet
38229 Clear the table of tracepoints, and empty the trace frame buffer.
38231 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38232 @cindex @samp{QTro} packet
38233 Establish the given ranges of memory as ``transparent''. The stub
38234 will answer requests for these ranges from memory's current contents,
38235 if they were not collected as part of the tracepoint hit.
38237 @value{GDBN} uses this to mark read-only regions of memory, like those
38238 containing program code. Since these areas never change, they should
38239 still have the same contents they did when the tracepoint was hit, so
38240 there's no reason for the stub to refuse to provide their contents.
38242 @item QTDisconnected:@var{value}
38243 @cindex @samp{QTDisconnected} packet
38244 Set the choice to what to do with the tracing run when @value{GDBN}
38245 disconnects from the target. A @var{value} of 1 directs the target to
38246 continue the tracing run, while 0 tells the target to stop tracing if
38247 @value{GDBN} is no longer in the picture.
38250 @cindex @samp{qTStatus} packet
38251 Ask the stub if there is a trace experiment running right now.
38253 The reply has the form:
38257 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38258 @var{running} is a single digit @code{1} if the trace is presently
38259 running, or @code{0} if not. It is followed by semicolon-separated
38260 optional fields that an agent may use to report additional status.
38264 If the trace is not running, the agent may report any of several
38265 explanations as one of the optional fields:
38270 No trace has been run yet.
38272 @item tstop[:@var{text}]:0
38273 The trace was stopped by a user-originated stop command. The optional
38274 @var{text} field is a user-supplied string supplied as part of the
38275 stop command (for instance, an explanation of why the trace was
38276 stopped manually). It is hex-encoded.
38279 The trace stopped because the trace buffer filled up.
38281 @item tdisconnected:0
38282 The trace stopped because @value{GDBN} disconnected from the target.
38284 @item tpasscount:@var{tpnum}
38285 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38287 @item terror:@var{text}:@var{tpnum}
38288 The trace stopped because tracepoint @var{tpnum} had an error. The
38289 string @var{text} is available to describe the nature of the error
38290 (for instance, a divide by zero in the condition expression).
38291 @var{text} is hex encoded.
38294 The trace stopped for some other reason.
38298 Additional optional fields supply statistical and other information.
38299 Although not required, they are extremely useful for users monitoring
38300 the progress of a trace run. If a trace has stopped, and these
38301 numbers are reported, they must reflect the state of the just-stopped
38306 @item tframes:@var{n}
38307 The number of trace frames in the buffer.
38309 @item tcreated:@var{n}
38310 The total number of trace frames created during the run. This may
38311 be larger than the trace frame count, if the buffer is circular.
38313 @item tsize:@var{n}
38314 The total size of the trace buffer, in bytes.
38316 @item tfree:@var{n}
38317 The number of bytes still unused in the buffer.
38319 @item circular:@var{n}
38320 The value of the circular trace buffer flag. @code{1} means that the
38321 trace buffer is circular and old trace frames will be discarded if
38322 necessary to make room, @code{0} means that the trace buffer is linear
38325 @item disconn:@var{n}
38326 The value of the disconnected tracing flag. @code{1} means that
38327 tracing will continue after @value{GDBN} disconnects, @code{0} means
38328 that the trace run will stop.
38332 @item qTP:@var{tp}:@var{addr}
38333 @cindex tracepoint status, remote request
38334 @cindex @samp{qTP} packet
38335 Ask the stub for the current state of tracepoint number @var{tp} at
38336 address @var{addr}.
38340 @item V@var{hits}:@var{usage}
38341 The tracepoint has been hit @var{hits} times so far during the trace
38342 run, and accounts for @var{usage} in the trace buffer. Note that
38343 @code{while-stepping} steps are not counted as separate hits, but the
38344 steps' space consumption is added into the usage number.
38348 @item qTV:@var{var}
38349 @cindex trace state variable value, remote request
38350 @cindex @samp{qTV} packet
38351 Ask the stub for the value of the trace state variable number @var{var}.
38356 The value of the variable is @var{value}. This will be the current
38357 value of the variable if the user is examining a running target, or a
38358 saved value if the variable was collected in the trace frame that the
38359 user is looking at. Note that multiple requests may result in
38360 different reply values, such as when requesting values while the
38361 program is running.
38364 The value of the variable is unknown. This would occur, for example,
38365 if the user is examining a trace frame in which the requested variable
38370 @cindex @samp{qTfP} packet
38372 @cindex @samp{qTsP} packet
38373 These packets request data about tracepoints that are being used by
38374 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38375 of data, and multiple @code{qTsP} to get additional pieces. Replies
38376 to these packets generally take the form of the @code{QTDP} packets
38377 that define tracepoints. (FIXME add detailed syntax)
38380 @cindex @samp{qTfV} packet
38382 @cindex @samp{qTsV} packet
38383 These packets request data about trace state variables that are on the
38384 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38385 and multiple @code{qTsV} to get additional variables. Replies to
38386 these packets follow the syntax of the @code{QTDV} packets that define
38387 trace state variables.
38393 @cindex @samp{qTfSTM} packet
38394 @cindex @samp{qTsSTM} packet
38395 These packets request data about static tracepoint markers that exist
38396 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38397 first piece of data, and multiple @code{qTsSTM} to get additional
38398 pieces. Replies to these packets take the following form:
38402 @item m @var{address}:@var{id}:@var{extra}
38404 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38405 a comma-separated list of markers
38407 (lower case letter @samp{L}) denotes end of list.
38409 An error occurred. @var{nn} are hex digits.
38411 An empty reply indicates that the request is not supported by the
38415 @var{address} is encoded in hex.
38416 @var{id} and @var{extra} are strings encoded in hex.
38418 In response to each query, the target will reply with a list of one or
38419 more markers, separated by commas. @value{GDBN} will respond to each
38420 reply with a request for more markers (using the @samp{qs} form of the
38421 query), until the target responds with @samp{l} (lower-case ell, for
38424 @item qTSTMat:@var{address}
38426 @cindex @samp{qTSTMat} packet
38427 This packets requests data about static tracepoint markers in the
38428 target program at @var{address}. Replies to this packet follow the
38429 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38430 tracepoint markers.
38432 @item QTSave:@var{filename}
38433 @cindex @samp{QTSave} packet
38434 This packet directs the target to save trace data to the file name
38435 @var{filename} in the target's filesystem. @var{filename} is encoded
38436 as a hex string; the interpretation of the file name (relative vs
38437 absolute, wild cards, etc) is up to the target.
38439 @item qTBuffer:@var{offset},@var{len}
38440 @cindex @samp{qTBuffer} packet
38441 Return up to @var{len} bytes of the current contents of trace buffer,
38442 starting at @var{offset}. The trace buffer is treated as if it were
38443 a contiguous collection of traceframes, as per the trace file format.
38444 The reply consists as many hex-encoded bytes as the target can deliver
38445 in a packet; it is not an error to return fewer than were asked for.
38446 A reply consisting of just @code{l} indicates that no bytes are
38449 @item QTBuffer:circular:@var{value}
38450 This packet directs the target to use a circular trace buffer if
38451 @var{value} is 1, or a linear buffer if the value is 0.
38453 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38454 @cindex @samp{QTNotes} packet
38455 This packet adds optional textual notes to the trace run. Allowable
38456 types include @code{user}, @code{notes}, and @code{tstop}, the
38457 @var{text} fields are arbitrary strings, hex-encoded.
38461 @subsection Relocate instruction reply packet
38462 When installing fast tracepoints in memory, the target may need to
38463 relocate the instruction currently at the tracepoint address to a
38464 different address in memory. For most instructions, a simple copy is
38465 enough, but, for example, call instructions that implicitly push the
38466 return address on the stack, and relative branches or other
38467 PC-relative instructions require offset adjustment, so that the effect
38468 of executing the instruction at a different address is the same as if
38469 it had executed in the original location.
38471 In response to several of the tracepoint packets, the target may also
38472 respond with a number of intermediate @samp{qRelocInsn} request
38473 packets before the final result packet, to have @value{GDBN} handle
38474 this relocation operation. If a packet supports this mechanism, its
38475 documentation will explicitly say so. See for example the above
38476 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38477 format of the request is:
38480 @item qRelocInsn:@var{from};@var{to}
38482 This requests @value{GDBN} to copy instruction at address @var{from}
38483 to address @var{to}, possibly adjusted so that executing the
38484 instruction at @var{to} has the same effect as executing it at
38485 @var{from}. @value{GDBN} writes the adjusted instruction to target
38486 memory starting at @var{to}.
38491 @item qRelocInsn:@var{adjusted_size}
38492 Informs the stub the relocation is complete. @var{adjusted_size} is
38493 the length in bytes of resulting relocated instruction sequence.
38495 A badly formed request was detected, or an error was encountered while
38496 relocating the instruction.
38499 @node Host I/O Packets
38500 @section Host I/O Packets
38501 @cindex Host I/O, remote protocol
38502 @cindex file transfer, remote protocol
38504 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38505 operations on the far side of a remote link. For example, Host I/O is
38506 used to upload and download files to a remote target with its own
38507 filesystem. Host I/O uses the same constant values and data structure
38508 layout as the target-initiated File-I/O protocol. However, the
38509 Host I/O packets are structured differently. The target-initiated
38510 protocol relies on target memory to store parameters and buffers.
38511 Host I/O requests are initiated by @value{GDBN}, and the
38512 target's memory is not involved. @xref{File-I/O Remote Protocol
38513 Extension}, for more details on the target-initiated protocol.
38515 The Host I/O request packets all encode a single operation along with
38516 its arguments. They have this format:
38520 @item vFile:@var{operation}: @var{parameter}@dots{}
38521 @var{operation} is the name of the particular request; the target
38522 should compare the entire packet name up to the second colon when checking
38523 for a supported operation. The format of @var{parameter} depends on
38524 the operation. Numbers are always passed in hexadecimal. Negative
38525 numbers have an explicit minus sign (i.e.@: two's complement is not
38526 used). Strings (e.g.@: filenames) are encoded as a series of
38527 hexadecimal bytes. The last argument to a system call may be a
38528 buffer of escaped binary data (@pxref{Binary Data}).
38532 The valid responses to Host I/O packets are:
38536 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38537 @var{result} is the integer value returned by this operation, usually
38538 non-negative for success and -1 for errors. If an error has occured,
38539 @var{errno} will be included in the result. @var{errno} will have a
38540 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38541 operations which return data, @var{attachment} supplies the data as a
38542 binary buffer. Binary buffers in response packets are escaped in the
38543 normal way (@pxref{Binary Data}). See the individual packet
38544 documentation for the interpretation of @var{result} and
38548 An empty response indicates that this operation is not recognized.
38552 These are the supported Host I/O operations:
38555 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38556 Open a file at @var{pathname} and return a file descriptor for it, or
38557 return -1 if an error occurs. @var{pathname} is a string,
38558 @var{flags} is an integer indicating a mask of open flags
38559 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38560 of mode bits to use if the file is created (@pxref{mode_t Values}).
38561 @xref{open}, for details of the open flags and mode values.
38563 @item vFile:close: @var{fd}
38564 Close the open file corresponding to @var{fd} and return 0, or
38565 -1 if an error occurs.
38567 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38568 Read data from the open file corresponding to @var{fd}. Up to
38569 @var{count} bytes will be read from the file, starting at @var{offset}
38570 relative to the start of the file. The target may read fewer bytes;
38571 common reasons include packet size limits and an end-of-file
38572 condition. The number of bytes read is returned. Zero should only be
38573 returned for a successful read at the end of the file, or if
38574 @var{count} was zero.
38576 The data read should be returned as a binary attachment on success.
38577 If zero bytes were read, the response should include an empty binary
38578 attachment (i.e.@: a trailing semicolon). The return value is the
38579 number of target bytes read; the binary attachment may be longer if
38580 some characters were escaped.
38582 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38583 Write @var{data} (a binary buffer) to the open file corresponding
38584 to @var{fd}. Start the write at @var{offset} from the start of the
38585 file. Unlike many @code{write} system calls, there is no
38586 separate @var{count} argument; the length of @var{data} in the
38587 packet is used. @samp{vFile:write} returns the number of bytes written,
38588 which may be shorter than the length of @var{data}, or -1 if an
38591 @item vFile:unlink: @var{pathname}
38592 Delete the file at @var{pathname} on the target. Return 0,
38593 or -1 if an error occurs. @var{pathname} is a string.
38595 @item vFile:readlink: @var{filename}
38596 Read value of symbolic link @var{filename} on the target. Return
38597 the number of bytes read, or -1 if an error occurs.
38599 The data read should be returned as a binary attachment on success.
38600 If zero bytes were read, the response should include an empty binary
38601 attachment (i.e.@: a trailing semicolon). The return value is the
38602 number of target bytes read; the binary attachment may be longer if
38603 some characters were escaped.
38608 @section Interrupts
38609 @cindex interrupts (remote protocol)
38611 When a program on the remote target is running, @value{GDBN} may
38612 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38613 a @code{BREAK} followed by @code{g},
38614 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38616 The precise meaning of @code{BREAK} is defined by the transport
38617 mechanism and may, in fact, be undefined. @value{GDBN} does not
38618 currently define a @code{BREAK} mechanism for any of the network
38619 interfaces except for TCP, in which case @value{GDBN} sends the
38620 @code{telnet} BREAK sequence.
38622 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38623 transport mechanisms. It is represented by sending the single byte
38624 @code{0x03} without any of the usual packet overhead described in
38625 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38626 transmitted as part of a packet, it is considered to be packet data
38627 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38628 (@pxref{X packet}), used for binary downloads, may include an unescaped
38629 @code{0x03} as part of its packet.
38631 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38632 When Linux kernel receives this sequence from serial port,
38633 it stops execution and connects to gdb.
38635 Stubs are not required to recognize these interrupt mechanisms and the
38636 precise meaning associated with receipt of the interrupt is
38637 implementation defined. If the target supports debugging of multiple
38638 threads and/or processes, it should attempt to interrupt all
38639 currently-executing threads and processes.
38640 If the stub is successful at interrupting the
38641 running program, it should send one of the stop
38642 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38643 of successfully stopping the program in all-stop mode, and a stop reply
38644 for each stopped thread in non-stop mode.
38645 Interrupts received while the
38646 program is stopped are discarded.
38648 @node Notification Packets
38649 @section Notification Packets
38650 @cindex notification packets
38651 @cindex packets, notification
38653 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38654 packets that require no acknowledgment. Both the GDB and the stub
38655 may send notifications (although the only notifications defined at
38656 present are sent by the stub). Notifications carry information
38657 without incurring the round-trip latency of an acknowledgment, and so
38658 are useful for low-impact communications where occasional packet loss
38661 A notification packet has the form @samp{% @var{data} #
38662 @var{checksum}}, where @var{data} is the content of the notification,
38663 and @var{checksum} is a checksum of @var{data}, computed and formatted
38664 as for ordinary @value{GDBN} packets. A notification's @var{data}
38665 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38666 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38667 to acknowledge the notification's receipt or to report its corruption.
38669 Every notification's @var{data} begins with a name, which contains no
38670 colon characters, followed by a colon character.
38672 Recipients should silently ignore corrupted notifications and
38673 notifications they do not understand. Recipients should restart
38674 timeout periods on receipt of a well-formed notification, whether or
38675 not they understand it.
38677 Senders should only send the notifications described here when this
38678 protocol description specifies that they are permitted. In the
38679 future, we may extend the protocol to permit existing notifications in
38680 new contexts; this rule helps older senders avoid confusing newer
38683 (Older versions of @value{GDBN} ignore bytes received until they see
38684 the @samp{$} byte that begins an ordinary packet, so new stubs may
38685 transmit notifications without fear of confusing older clients. There
38686 are no notifications defined for @value{GDBN} to send at the moment, but we
38687 assume that most older stubs would ignore them, as well.)
38689 Each notification is comprised of three parts:
38691 @item @var{name}:@var{event}
38692 The notification packet is sent by the side that initiates the
38693 exchange (currently, only the stub does that), with @var{event}
38694 carrying the specific information about the notification.
38695 @var{name} is the name of the notification.
38697 The acknowledge sent by the other side, usually @value{GDBN}, to
38698 acknowledge the exchange and request the event.
38701 The purpose of an asynchronous notification mechanism is to report to
38702 @value{GDBN} that something interesting happened in the remote stub.
38704 The remote stub may send notification @var{name}:@var{event}
38705 at any time, but @value{GDBN} acknowledges the notification when
38706 appropriate. The notification event is pending before @value{GDBN}
38707 acknowledges. Only one notification at a time may be pending; if
38708 additional events occur before @value{GDBN} has acknowledged the
38709 previous notification, they must be queued by the stub for later
38710 synchronous transmission in response to @var{ack} packets from
38711 @value{GDBN}. Because the notification mechanism is unreliable,
38712 the stub is permitted to resend a notification if it believes
38713 @value{GDBN} may not have received it.
38715 Specifically, notifications may appear when @value{GDBN} is not
38716 otherwise reading input from the stub, or when @value{GDBN} is
38717 expecting to read a normal synchronous response or a
38718 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38719 Notification packets are distinct from any other communication from
38720 the stub so there is no ambiguity.
38722 After receiving a notification, @value{GDBN} shall acknowledge it by
38723 sending a @var{ack} packet as a regular, synchronous request to the
38724 stub. Such acknowledgment is not required to happen immediately, as
38725 @value{GDBN} is permitted to send other, unrelated packets to the
38726 stub first, which the stub should process normally.
38728 Upon receiving a @var{ack} packet, if the stub has other queued
38729 events to report to @value{GDBN}, it shall respond by sending a
38730 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38731 packet to solicit further responses; again, it is permitted to send
38732 other, unrelated packets as well which the stub should process
38735 If the stub receives a @var{ack} packet and there are no additional
38736 @var{event} to report, the stub shall return an @samp{OK} response.
38737 At this point, @value{GDBN} has finished processing a notification
38738 and the stub has completed sending any queued events. @value{GDBN}
38739 won't accept any new notifications until the final @samp{OK} is
38740 received . If further notification events occur, the stub shall send
38741 a new notification, @value{GDBN} shall accept the notification, and
38742 the process shall be repeated.
38744 The process of asynchronous notification can be illustrated by the
38747 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
38750 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
38752 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
38757 The following notifications are defined:
38758 @multitable @columnfractions 0.12 0.12 0.38 0.38
38767 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
38768 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
38769 for information on how these notifications are acknowledged by
38771 @tab Report an asynchronous stop event in non-stop mode.
38775 @node Remote Non-Stop
38776 @section Remote Protocol Support for Non-Stop Mode
38778 @value{GDBN}'s remote protocol supports non-stop debugging of
38779 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
38780 supports non-stop mode, it should report that to @value{GDBN} by including
38781 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
38783 @value{GDBN} typically sends a @samp{QNonStop} packet only when
38784 establishing a new connection with the stub. Entering non-stop mode
38785 does not alter the state of any currently-running threads, but targets
38786 must stop all threads in any already-attached processes when entering
38787 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
38788 probe the target state after a mode change.
38790 In non-stop mode, when an attached process encounters an event that
38791 would otherwise be reported with a stop reply, it uses the
38792 asynchronous notification mechanism (@pxref{Notification Packets}) to
38793 inform @value{GDBN}. In contrast to all-stop mode, where all threads
38794 in all processes are stopped when a stop reply is sent, in non-stop
38795 mode only the thread reporting the stop event is stopped. That is,
38796 when reporting a @samp{S} or @samp{T} response to indicate completion
38797 of a step operation, hitting a breakpoint, or a fault, only the
38798 affected thread is stopped; any other still-running threads continue
38799 to run. When reporting a @samp{W} or @samp{X} response, all running
38800 threads belonging to other attached processes continue to run.
38802 In non-stop mode, the target shall respond to the @samp{?} packet as
38803 follows. First, any incomplete stop reply notification/@samp{vStopped}
38804 sequence in progress is abandoned. The target must begin a new
38805 sequence reporting stop events for all stopped threads, whether or not
38806 it has previously reported those events to @value{GDBN}. The first
38807 stop reply is sent as a synchronous reply to the @samp{?} packet, and
38808 subsequent stop replies are sent as responses to @samp{vStopped} packets
38809 using the mechanism described above. The target must not send
38810 asynchronous stop reply notifications until the sequence is complete.
38811 If all threads are running when the target receives the @samp{?} packet,
38812 or if the target is not attached to any process, it shall respond
38815 @node Packet Acknowledgment
38816 @section Packet Acknowledgment
38818 @cindex acknowledgment, for @value{GDBN} remote
38819 @cindex packet acknowledgment, for @value{GDBN} remote
38820 By default, when either the host or the target machine receives a packet,
38821 the first response expected is an acknowledgment: either @samp{+} (to indicate
38822 the package was received correctly) or @samp{-} (to request retransmission).
38823 This mechanism allows the @value{GDBN} remote protocol to operate over
38824 unreliable transport mechanisms, such as a serial line.
38826 In cases where the transport mechanism is itself reliable (such as a pipe or
38827 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
38828 It may be desirable to disable them in that case to reduce communication
38829 overhead, or for other reasons. This can be accomplished by means of the
38830 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
38832 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
38833 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
38834 and response format still includes the normal checksum, as described in
38835 @ref{Overview}, but the checksum may be ignored by the receiver.
38837 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
38838 no-acknowledgment mode, it should report that to @value{GDBN}
38839 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
38840 @pxref{qSupported}.
38841 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
38842 disabled via the @code{set remote noack-packet off} command
38843 (@pxref{Remote Configuration}),
38844 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
38845 Only then may the stub actually turn off packet acknowledgments.
38846 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
38847 response, which can be safely ignored by the stub.
38849 Note that @code{set remote noack-packet} command only affects negotiation
38850 between @value{GDBN} and the stub when subsequent connections are made;
38851 it does not affect the protocol acknowledgment state for any current
38853 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
38854 new connection is established,
38855 there is also no protocol request to re-enable the acknowledgments
38856 for the current connection, once disabled.
38861 Example sequence of a target being re-started. Notice how the restart
38862 does not get any direct output:
38867 @emph{target restarts}
38870 <- @code{T001:1234123412341234}
38874 Example sequence of a target being stepped by a single instruction:
38877 -> @code{G1445@dots{}}
38882 <- @code{T001:1234123412341234}
38886 <- @code{1455@dots{}}
38890 @node File-I/O Remote Protocol Extension
38891 @section File-I/O Remote Protocol Extension
38892 @cindex File-I/O remote protocol extension
38895 * File-I/O Overview::
38896 * Protocol Basics::
38897 * The F Request Packet::
38898 * The F Reply Packet::
38899 * The Ctrl-C Message::
38901 * List of Supported Calls::
38902 * Protocol-specific Representation of Datatypes::
38904 * File-I/O Examples::
38907 @node File-I/O Overview
38908 @subsection File-I/O Overview
38909 @cindex file-i/o overview
38911 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
38912 target to use the host's file system and console I/O to perform various
38913 system calls. System calls on the target system are translated into a
38914 remote protocol packet to the host system, which then performs the needed
38915 actions and returns a response packet to the target system.
38916 This simulates file system operations even on targets that lack file systems.
38918 The protocol is defined to be independent of both the host and target systems.
38919 It uses its own internal representation of datatypes and values. Both
38920 @value{GDBN} and the target's @value{GDBN} stub are responsible for
38921 translating the system-dependent value representations into the internal
38922 protocol representations when data is transmitted.
38924 The communication is synchronous. A system call is possible only when
38925 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
38926 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
38927 the target is stopped to allow deterministic access to the target's
38928 memory. Therefore File-I/O is not interruptible by target signals. On
38929 the other hand, it is possible to interrupt File-I/O by a user interrupt
38930 (@samp{Ctrl-C}) within @value{GDBN}.
38932 The target's request to perform a host system call does not finish
38933 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
38934 after finishing the system call, the target returns to continuing the
38935 previous activity (continue, step). No additional continue or step
38936 request from @value{GDBN} is required.
38939 (@value{GDBP}) continue
38940 <- target requests 'system call X'
38941 target is stopped, @value{GDBN} executes system call
38942 -> @value{GDBN} returns result
38943 ... target continues, @value{GDBN} returns to wait for the target
38944 <- target hits breakpoint and sends a Txx packet
38947 The protocol only supports I/O on the console and to regular files on
38948 the host file system. Character or block special devices, pipes,
38949 named pipes, sockets or any other communication method on the host
38950 system are not supported by this protocol.
38952 File I/O is not supported in non-stop mode.
38954 @node Protocol Basics
38955 @subsection Protocol Basics
38956 @cindex protocol basics, file-i/o
38958 The File-I/O protocol uses the @code{F} packet as the request as well
38959 as reply packet. Since a File-I/O system call can only occur when
38960 @value{GDBN} is waiting for a response from the continuing or stepping target,
38961 the File-I/O request is a reply that @value{GDBN} has to expect as a result
38962 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
38963 This @code{F} packet contains all information needed to allow @value{GDBN}
38964 to call the appropriate host system call:
38968 A unique identifier for the requested system call.
38971 All parameters to the system call. Pointers are given as addresses
38972 in the target memory address space. Pointers to strings are given as
38973 pointer/length pair. Numerical values are given as they are.
38974 Numerical control flags are given in a protocol-specific representation.
38978 At this point, @value{GDBN} has to perform the following actions.
38982 If the parameters include pointer values to data needed as input to a
38983 system call, @value{GDBN} requests this data from the target with a
38984 standard @code{m} packet request. This additional communication has to be
38985 expected by the target implementation and is handled as any other @code{m}
38989 @value{GDBN} translates all value from protocol representation to host
38990 representation as needed. Datatypes are coerced into the host types.
38993 @value{GDBN} calls the system call.
38996 It then coerces datatypes back to protocol representation.
38999 If the system call is expected to return data in buffer space specified
39000 by pointer parameters to the call, the data is transmitted to the
39001 target using a @code{M} or @code{X} packet. This packet has to be expected
39002 by the target implementation and is handled as any other @code{M} or @code{X}
39007 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39008 necessary information for the target to continue. This at least contains
39015 @code{errno}, if has been changed by the system call.
39022 After having done the needed type and value coercion, the target continues
39023 the latest continue or step action.
39025 @node The F Request Packet
39026 @subsection The @code{F} Request Packet
39027 @cindex file-i/o request packet
39028 @cindex @code{F} request packet
39030 The @code{F} request packet has the following format:
39033 @item F@var{call-id},@var{parameter@dots{}}
39035 @var{call-id} is the identifier to indicate the host system call to be called.
39036 This is just the name of the function.
39038 @var{parameter@dots{}} are the parameters to the system call.
39039 Parameters are hexadecimal integer values, either the actual values in case
39040 of scalar datatypes, pointers to target buffer space in case of compound
39041 datatypes and unspecified memory areas, or pointer/length pairs in case
39042 of string parameters. These are appended to the @var{call-id} as a
39043 comma-delimited list. All values are transmitted in ASCII
39044 string representation, pointer/length pairs separated by a slash.
39050 @node The F Reply Packet
39051 @subsection The @code{F} Reply Packet
39052 @cindex file-i/o reply packet
39053 @cindex @code{F} reply packet
39055 The @code{F} reply packet has the following format:
39059 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39061 @var{retcode} is the return code of the system call as hexadecimal value.
39063 @var{errno} is the @code{errno} set by the call, in protocol-specific
39065 This parameter can be omitted if the call was successful.
39067 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39068 case, @var{errno} must be sent as well, even if the call was successful.
39069 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39076 or, if the call was interrupted before the host call has been performed:
39083 assuming 4 is the protocol-specific representation of @code{EINTR}.
39088 @node The Ctrl-C Message
39089 @subsection The @samp{Ctrl-C} Message
39090 @cindex ctrl-c message, in file-i/o protocol
39092 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39093 reply packet (@pxref{The F Reply Packet}),
39094 the target should behave as if it had
39095 gotten a break message. The meaning for the target is ``system call
39096 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39097 (as with a break message) and return to @value{GDBN} with a @code{T02}
39100 It's important for the target to know in which
39101 state the system call was interrupted. There are two possible cases:
39105 The system call hasn't been performed on the host yet.
39108 The system call on the host has been finished.
39112 These two states can be distinguished by the target by the value of the
39113 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39114 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39115 on POSIX systems. In any other case, the target may presume that the
39116 system call has been finished --- successfully or not --- and should behave
39117 as if the break message arrived right after the system call.
39119 @value{GDBN} must behave reliably. If the system call has not been called
39120 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39121 @code{errno} in the packet. If the system call on the host has been finished
39122 before the user requests a break, the full action must be finished by
39123 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39124 The @code{F} packet may only be sent when either nothing has happened
39125 or the full action has been completed.
39128 @subsection Console I/O
39129 @cindex console i/o as part of file-i/o
39131 By default and if not explicitly closed by the target system, the file
39132 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39133 on the @value{GDBN} console is handled as any other file output operation
39134 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39135 by @value{GDBN} so that after the target read request from file descriptor
39136 0 all following typing is buffered until either one of the following
39141 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39143 system call is treated as finished.
39146 The user presses @key{RET}. This is treated as end of input with a trailing
39150 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39151 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39155 If the user has typed more characters than fit in the buffer given to
39156 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39157 either another @code{read(0, @dots{})} is requested by the target, or debugging
39158 is stopped at the user's request.
39161 @node List of Supported Calls
39162 @subsection List of Supported Calls
39163 @cindex list of supported file-i/o calls
39180 @unnumberedsubsubsec open
39181 @cindex open, file-i/o system call
39186 int open(const char *pathname, int flags);
39187 int open(const char *pathname, int flags, mode_t mode);
39191 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39194 @var{flags} is the bitwise @code{OR} of the following values:
39198 If the file does not exist it will be created. The host
39199 rules apply as far as file ownership and time stamps
39203 When used with @code{O_CREAT}, if the file already exists it is
39204 an error and open() fails.
39207 If the file already exists and the open mode allows
39208 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39209 truncated to zero length.
39212 The file is opened in append mode.
39215 The file is opened for reading only.
39218 The file is opened for writing only.
39221 The file is opened for reading and writing.
39225 Other bits are silently ignored.
39229 @var{mode} is the bitwise @code{OR} of the following values:
39233 User has read permission.
39236 User has write permission.
39239 Group has read permission.
39242 Group has write permission.
39245 Others have read permission.
39248 Others have write permission.
39252 Other bits are silently ignored.
39255 @item Return value:
39256 @code{open} returns the new file descriptor or -1 if an error
39263 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39266 @var{pathname} refers to a directory.
39269 The requested access is not allowed.
39272 @var{pathname} was too long.
39275 A directory component in @var{pathname} does not exist.
39278 @var{pathname} refers to a device, pipe, named pipe or socket.
39281 @var{pathname} refers to a file on a read-only filesystem and
39282 write access was requested.
39285 @var{pathname} is an invalid pointer value.
39288 No space on device to create the file.
39291 The process already has the maximum number of files open.
39294 The limit on the total number of files open on the system
39298 The call was interrupted by the user.
39304 @unnumberedsubsubsec close
39305 @cindex close, file-i/o system call
39314 @samp{Fclose,@var{fd}}
39316 @item Return value:
39317 @code{close} returns zero on success, or -1 if an error occurred.
39323 @var{fd} isn't a valid open file descriptor.
39326 The call was interrupted by the user.
39332 @unnumberedsubsubsec read
39333 @cindex read, file-i/o system call
39338 int read(int fd, void *buf, unsigned int count);
39342 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39344 @item Return value:
39345 On success, the number of bytes read is returned.
39346 Zero indicates end of file. If count is zero, read
39347 returns zero as well. On error, -1 is returned.
39353 @var{fd} is not a valid file descriptor or is not open for
39357 @var{bufptr} is an invalid pointer value.
39360 The call was interrupted by the user.
39366 @unnumberedsubsubsec write
39367 @cindex write, file-i/o system call
39372 int write(int fd, const void *buf, unsigned int count);
39376 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39378 @item Return value:
39379 On success, the number of bytes written are returned.
39380 Zero indicates nothing was written. On error, -1
39387 @var{fd} is not a valid file descriptor or is not open for
39391 @var{bufptr} is an invalid pointer value.
39394 An attempt was made to write a file that exceeds the
39395 host-specific maximum file size allowed.
39398 No space on device to write the data.
39401 The call was interrupted by the user.
39407 @unnumberedsubsubsec lseek
39408 @cindex lseek, file-i/o system call
39413 long lseek (int fd, long offset, int flag);
39417 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39419 @var{flag} is one of:
39423 The offset is set to @var{offset} bytes.
39426 The offset is set to its current location plus @var{offset}
39430 The offset is set to the size of the file plus @var{offset}
39434 @item Return value:
39435 On success, the resulting unsigned offset in bytes from
39436 the beginning of the file is returned. Otherwise, a
39437 value of -1 is returned.
39443 @var{fd} is not a valid open file descriptor.
39446 @var{fd} is associated with the @value{GDBN} console.
39449 @var{flag} is not a proper value.
39452 The call was interrupted by the user.
39458 @unnumberedsubsubsec rename
39459 @cindex rename, file-i/o system call
39464 int rename(const char *oldpath, const char *newpath);
39468 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39470 @item Return value:
39471 On success, zero is returned. On error, -1 is returned.
39477 @var{newpath} is an existing directory, but @var{oldpath} is not a
39481 @var{newpath} is a non-empty directory.
39484 @var{oldpath} or @var{newpath} is a directory that is in use by some
39488 An attempt was made to make a directory a subdirectory
39492 A component used as a directory in @var{oldpath} or new
39493 path is not a directory. Or @var{oldpath} is a directory
39494 and @var{newpath} exists but is not a directory.
39497 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39500 No access to the file or the path of the file.
39504 @var{oldpath} or @var{newpath} was too long.
39507 A directory component in @var{oldpath} or @var{newpath} does not exist.
39510 The file is on a read-only filesystem.
39513 The device containing the file has no room for the new
39517 The call was interrupted by the user.
39523 @unnumberedsubsubsec unlink
39524 @cindex unlink, file-i/o system call
39529 int unlink(const char *pathname);
39533 @samp{Funlink,@var{pathnameptr}/@var{len}}
39535 @item Return value:
39536 On success, zero is returned. On error, -1 is returned.
39542 No access to the file or the path of the file.
39545 The system does not allow unlinking of directories.
39548 The file @var{pathname} cannot be unlinked because it's
39549 being used by another process.
39552 @var{pathnameptr} is an invalid pointer value.
39555 @var{pathname} was too long.
39558 A directory component in @var{pathname} does not exist.
39561 A component of the path is not a directory.
39564 The file is on a read-only filesystem.
39567 The call was interrupted by the user.
39573 @unnumberedsubsubsec stat/fstat
39574 @cindex fstat, file-i/o system call
39575 @cindex stat, file-i/o system call
39580 int stat(const char *pathname, struct stat *buf);
39581 int fstat(int fd, struct stat *buf);
39585 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39586 @samp{Ffstat,@var{fd},@var{bufptr}}
39588 @item Return value:
39589 On success, zero is returned. On error, -1 is returned.
39595 @var{fd} is not a valid open file.
39598 A directory component in @var{pathname} does not exist or the
39599 path is an empty string.
39602 A component of the path is not a directory.
39605 @var{pathnameptr} is an invalid pointer value.
39608 No access to the file or the path of the file.
39611 @var{pathname} was too long.
39614 The call was interrupted by the user.
39620 @unnumberedsubsubsec gettimeofday
39621 @cindex gettimeofday, file-i/o system call
39626 int gettimeofday(struct timeval *tv, void *tz);
39630 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39632 @item Return value:
39633 On success, 0 is returned, -1 otherwise.
39639 @var{tz} is a non-NULL pointer.
39642 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39648 @unnumberedsubsubsec isatty
39649 @cindex isatty, file-i/o system call
39654 int isatty(int fd);
39658 @samp{Fisatty,@var{fd}}
39660 @item Return value:
39661 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39667 The call was interrupted by the user.
39672 Note that the @code{isatty} call is treated as a special case: it returns
39673 1 to the target if the file descriptor is attached
39674 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39675 would require implementing @code{ioctl} and would be more complex than
39680 @unnumberedsubsubsec system
39681 @cindex system, file-i/o system call
39686 int system(const char *command);
39690 @samp{Fsystem,@var{commandptr}/@var{len}}
39692 @item Return value:
39693 If @var{len} is zero, the return value indicates whether a shell is
39694 available. A zero return value indicates a shell is not available.
39695 For non-zero @var{len}, the value returned is -1 on error and the
39696 return status of the command otherwise. Only the exit status of the
39697 command is returned, which is extracted from the host's @code{system}
39698 return value by calling @code{WEXITSTATUS(retval)}. In case
39699 @file{/bin/sh} could not be executed, 127 is returned.
39705 The call was interrupted by the user.
39710 @value{GDBN} takes over the full task of calling the necessary host calls
39711 to perform the @code{system} call. The return value of @code{system} on
39712 the host is simplified before it's returned
39713 to the target. Any termination signal information from the child process
39714 is discarded, and the return value consists
39715 entirely of the exit status of the called command.
39717 Due to security concerns, the @code{system} call is by default refused
39718 by @value{GDBN}. The user has to allow this call explicitly with the
39719 @code{set remote system-call-allowed 1} command.
39722 @item set remote system-call-allowed
39723 @kindex set remote system-call-allowed
39724 Control whether to allow the @code{system} calls in the File I/O
39725 protocol for the remote target. The default is zero (disabled).
39727 @item show remote system-call-allowed
39728 @kindex show remote system-call-allowed
39729 Show whether the @code{system} calls are allowed in the File I/O
39733 @node Protocol-specific Representation of Datatypes
39734 @subsection Protocol-specific Representation of Datatypes
39735 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39738 * Integral Datatypes::
39740 * Memory Transfer::
39745 @node Integral Datatypes
39746 @unnumberedsubsubsec Integral Datatypes
39747 @cindex integral datatypes, in file-i/o protocol
39749 The integral datatypes used in the system calls are @code{int},
39750 @code{unsigned int}, @code{long}, @code{unsigned long},
39751 @code{mode_t}, and @code{time_t}.
39753 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
39754 implemented as 32 bit values in this protocol.
39756 @code{long} and @code{unsigned long} are implemented as 64 bit types.
39758 @xref{Limits}, for corresponding MIN and MAX values (similar to those
39759 in @file{limits.h}) to allow range checking on host and target.
39761 @code{time_t} datatypes are defined as seconds since the Epoch.
39763 All integral datatypes transferred as part of a memory read or write of a
39764 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
39767 @node Pointer Values
39768 @unnumberedsubsubsec Pointer Values
39769 @cindex pointer values, in file-i/o protocol
39771 Pointers to target data are transmitted as they are. An exception
39772 is made for pointers to buffers for which the length isn't
39773 transmitted as part of the function call, namely strings. Strings
39774 are transmitted as a pointer/length pair, both as hex values, e.g.@:
39781 which is a pointer to data of length 18 bytes at position 0x1aaf.
39782 The length is defined as the full string length in bytes, including
39783 the trailing null byte. For example, the string @code{"hello world"}
39784 at address 0x123456 is transmitted as
39790 @node Memory Transfer
39791 @unnumberedsubsubsec Memory Transfer
39792 @cindex memory transfer, in file-i/o protocol
39794 Structured data which is transferred using a memory read or write (for
39795 example, a @code{struct stat}) is expected to be in a protocol-specific format
39796 with all scalar multibyte datatypes being big endian. Translation to
39797 this representation needs to be done both by the target before the @code{F}
39798 packet is sent, and by @value{GDBN} before
39799 it transfers memory to the target. Transferred pointers to structured
39800 data should point to the already-coerced data at any time.
39804 @unnumberedsubsubsec struct stat
39805 @cindex struct stat, in file-i/o protocol
39807 The buffer of type @code{struct stat} used by the target and @value{GDBN}
39808 is defined as follows:
39812 unsigned int st_dev; /* device */
39813 unsigned int st_ino; /* inode */
39814 mode_t st_mode; /* protection */
39815 unsigned int st_nlink; /* number of hard links */
39816 unsigned int st_uid; /* user ID of owner */
39817 unsigned int st_gid; /* group ID of owner */
39818 unsigned int st_rdev; /* device type (if inode device) */
39819 unsigned long st_size; /* total size, in bytes */
39820 unsigned long st_blksize; /* blocksize for filesystem I/O */
39821 unsigned long st_blocks; /* number of blocks allocated */
39822 time_t st_atime; /* time of last access */
39823 time_t st_mtime; /* time of last modification */
39824 time_t st_ctime; /* time of last change */
39828 The integral datatypes conform to the definitions given in the
39829 appropriate section (see @ref{Integral Datatypes}, for details) so this
39830 structure is of size 64 bytes.
39832 The values of several fields have a restricted meaning and/or
39838 A value of 0 represents a file, 1 the console.
39841 No valid meaning for the target. Transmitted unchanged.
39844 Valid mode bits are described in @ref{Constants}. Any other
39845 bits have currently no meaning for the target.
39850 No valid meaning for the target. Transmitted unchanged.
39855 These values have a host and file system dependent
39856 accuracy. Especially on Windows hosts, the file system may not
39857 support exact timing values.
39860 The target gets a @code{struct stat} of the above representation and is
39861 responsible for coercing it to the target representation before
39864 Note that due to size differences between the host, target, and protocol
39865 representations of @code{struct stat} members, these members could eventually
39866 get truncated on the target.
39868 @node struct timeval
39869 @unnumberedsubsubsec struct timeval
39870 @cindex struct timeval, in file-i/o protocol
39872 The buffer of type @code{struct timeval} used by the File-I/O protocol
39873 is defined as follows:
39877 time_t tv_sec; /* second */
39878 long tv_usec; /* microsecond */
39882 The integral datatypes conform to the definitions given in the
39883 appropriate section (see @ref{Integral Datatypes}, for details) so this
39884 structure is of size 8 bytes.
39887 @subsection Constants
39888 @cindex constants, in file-i/o protocol
39890 The following values are used for the constants inside of the
39891 protocol. @value{GDBN} and target are responsible for translating these
39892 values before and after the call as needed.
39903 @unnumberedsubsubsec Open Flags
39904 @cindex open flags, in file-i/o protocol
39906 All values are given in hexadecimal representation.
39918 @node mode_t Values
39919 @unnumberedsubsubsec mode_t Values
39920 @cindex mode_t values, in file-i/o protocol
39922 All values are given in octal representation.
39939 @unnumberedsubsubsec Errno Values
39940 @cindex errno values, in file-i/o protocol
39942 All values are given in decimal representation.
39967 @code{EUNKNOWN} is used as a fallback error value if a host system returns
39968 any error value not in the list of supported error numbers.
39971 @unnumberedsubsubsec Lseek Flags
39972 @cindex lseek flags, in file-i/o protocol
39981 @unnumberedsubsubsec Limits
39982 @cindex limits, in file-i/o protocol
39984 All values are given in decimal representation.
39987 INT_MIN -2147483648
39989 UINT_MAX 4294967295
39990 LONG_MIN -9223372036854775808
39991 LONG_MAX 9223372036854775807
39992 ULONG_MAX 18446744073709551615
39995 @node File-I/O Examples
39996 @subsection File-I/O Examples
39997 @cindex file-i/o examples
39999 Example sequence of a write call, file descriptor 3, buffer is at target
40000 address 0x1234, 6 bytes should be written:
40003 <- @code{Fwrite,3,1234,6}
40004 @emph{request memory read from target}
40007 @emph{return "6 bytes written"}
40011 Example sequence of a read call, file descriptor 3, buffer is at target
40012 address 0x1234, 6 bytes should be read:
40015 <- @code{Fread,3,1234,6}
40016 @emph{request memory write to target}
40017 -> @code{X1234,6:XXXXXX}
40018 @emph{return "6 bytes read"}
40022 Example sequence of a read call, call fails on the host due to invalid
40023 file descriptor (@code{EBADF}):
40026 <- @code{Fread,3,1234,6}
40030 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40034 <- @code{Fread,3,1234,6}
40039 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40043 <- @code{Fread,3,1234,6}
40044 -> @code{X1234,6:XXXXXX}
40048 @node Library List Format
40049 @section Library List Format
40050 @cindex library list format, remote protocol
40052 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40053 same process as your application to manage libraries. In this case,
40054 @value{GDBN} can use the loader's symbol table and normal memory
40055 operations to maintain a list of shared libraries. On other
40056 platforms, the operating system manages loaded libraries.
40057 @value{GDBN} can not retrieve the list of currently loaded libraries
40058 through memory operations, so it uses the @samp{qXfer:libraries:read}
40059 packet (@pxref{qXfer library list read}) instead. The remote stub
40060 queries the target's operating system and reports which libraries
40063 The @samp{qXfer:libraries:read} packet returns an XML document which
40064 lists loaded libraries and their offsets. Each library has an
40065 associated name and one or more segment or section base addresses,
40066 which report where the library was loaded in memory.
40068 For the common case of libraries that are fully linked binaries, the
40069 library should have a list of segments. If the target supports
40070 dynamic linking of a relocatable object file, its library XML element
40071 should instead include a list of allocated sections. The segment or
40072 section bases are start addresses, not relocation offsets; they do not
40073 depend on the library's link-time base addresses.
40075 @value{GDBN} must be linked with the Expat library to support XML
40076 library lists. @xref{Expat}.
40078 A simple memory map, with one loaded library relocated by a single
40079 offset, looks like this:
40083 <library name="/lib/libc.so.6">
40084 <segment address="0x10000000"/>
40089 Another simple memory map, with one loaded library with three
40090 allocated sections (.text, .data, .bss), looks like this:
40094 <library name="sharedlib.o">
40095 <section address="0x10000000"/>
40096 <section address="0x20000000"/>
40097 <section address="0x30000000"/>
40102 The format of a library list is described by this DTD:
40105 <!-- library-list: Root element with versioning -->
40106 <!ELEMENT library-list (library)*>
40107 <!ATTLIST library-list version CDATA #FIXED "1.0">
40108 <!ELEMENT library (segment*, section*)>
40109 <!ATTLIST library name CDATA #REQUIRED>
40110 <!ELEMENT segment EMPTY>
40111 <!ATTLIST segment address CDATA #REQUIRED>
40112 <!ELEMENT section EMPTY>
40113 <!ATTLIST section address CDATA #REQUIRED>
40116 In addition, segments and section descriptors cannot be mixed within a
40117 single library element, and you must supply at least one segment or
40118 section for each library.
40120 @node Library List Format for SVR4 Targets
40121 @section Library List Format for SVR4 Targets
40122 @cindex library list format, remote protocol
40124 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40125 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40126 shared libraries. Still a special library list provided by this packet is
40127 more efficient for the @value{GDBN} remote protocol.
40129 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40130 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40131 target, the following parameters are reported:
40135 @code{name}, the absolute file name from the @code{l_name} field of
40136 @code{struct link_map}.
40138 @code{lm} with address of @code{struct link_map} used for TLS
40139 (Thread Local Storage) access.
40141 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40142 @code{struct link_map}. For prelinked libraries this is not an absolute
40143 memory address. It is a displacement of absolute memory address against
40144 address the file was prelinked to during the library load.
40146 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40149 Additionally the single @code{main-lm} attribute specifies address of
40150 @code{struct link_map} used for the main executable. This parameter is used
40151 for TLS access and its presence is optional.
40153 @value{GDBN} must be linked with the Expat library to support XML
40154 SVR4 library lists. @xref{Expat}.
40156 A simple memory map, with two loaded libraries (which do not use prelink),
40160 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40161 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40163 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40165 </library-list-svr>
40168 The format of an SVR4 library list is described by this DTD:
40171 <!-- library-list-svr4: Root element with versioning -->
40172 <!ELEMENT library-list-svr4 (library)*>
40173 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40174 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40175 <!ELEMENT library EMPTY>
40176 <!ATTLIST library name CDATA #REQUIRED>
40177 <!ATTLIST library lm CDATA #REQUIRED>
40178 <!ATTLIST library l_addr CDATA #REQUIRED>
40179 <!ATTLIST library l_ld CDATA #REQUIRED>
40182 @node Memory Map Format
40183 @section Memory Map Format
40184 @cindex memory map format
40186 To be able to write into flash memory, @value{GDBN} needs to obtain a
40187 memory map from the target. This section describes the format of the
40190 The memory map is obtained using the @samp{qXfer:memory-map:read}
40191 (@pxref{qXfer memory map read}) packet and is an XML document that
40192 lists memory regions.
40194 @value{GDBN} must be linked with the Expat library to support XML
40195 memory maps. @xref{Expat}.
40197 The top-level structure of the document is shown below:
40200 <?xml version="1.0"?>
40201 <!DOCTYPE memory-map
40202 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40203 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40209 Each region can be either:
40214 A region of RAM starting at @var{addr} and extending for @var{length}
40218 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40223 A region of read-only memory:
40226 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40231 A region of flash memory, with erasure blocks @var{blocksize}
40235 <memory type="flash" start="@var{addr}" length="@var{length}">
40236 <property name="blocksize">@var{blocksize}</property>
40242 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40243 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40244 packets to write to addresses in such ranges.
40246 The formal DTD for memory map format is given below:
40249 <!-- ................................................... -->
40250 <!-- Memory Map XML DTD ................................ -->
40251 <!-- File: memory-map.dtd .............................. -->
40252 <!-- .................................... .............. -->
40253 <!-- memory-map.dtd -->
40254 <!-- memory-map: Root element with versioning -->
40255 <!ELEMENT memory-map (memory | property)>
40256 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40257 <!ELEMENT memory (property)>
40258 <!-- memory: Specifies a memory region,
40259 and its type, or device. -->
40260 <!ATTLIST memory type CDATA #REQUIRED
40261 start CDATA #REQUIRED
40262 length CDATA #REQUIRED
40263 device CDATA #IMPLIED>
40264 <!-- property: Generic attribute tag -->
40265 <!ELEMENT property (#PCDATA | property)*>
40266 <!ATTLIST property name CDATA #REQUIRED>
40269 @node Thread List Format
40270 @section Thread List Format
40271 @cindex thread list format
40273 To efficiently update the list of threads and their attributes,
40274 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40275 (@pxref{qXfer threads read}) and obtains the XML document with
40276 the following structure:
40279 <?xml version="1.0"?>
40281 <thread id="id" core="0">
40282 ... description ...
40287 Each @samp{thread} element must have the @samp{id} attribute that
40288 identifies the thread (@pxref{thread-id syntax}). The
40289 @samp{core} attribute, if present, specifies which processor core
40290 the thread was last executing on. The content of the of @samp{thread}
40291 element is interpreted as human-readable auxilliary information.
40293 @node Traceframe Info Format
40294 @section Traceframe Info Format
40295 @cindex traceframe info format
40297 To be able to know which objects in the inferior can be examined when
40298 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40299 memory ranges, registers and trace state variables that have been
40300 collected in a traceframe.
40302 This list is obtained using the @samp{qXfer:traceframe-info:read}
40303 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40305 @value{GDBN} must be linked with the Expat library to support XML
40306 traceframe info discovery. @xref{Expat}.
40308 The top-level structure of the document is shown below:
40311 <?xml version="1.0"?>
40312 <!DOCTYPE traceframe-info
40313 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40314 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40320 Each traceframe block can be either:
40325 A region of collected memory starting at @var{addr} and extending for
40326 @var{length} bytes from there:
40329 <memory start="@var{addr}" length="@var{length}"/>
40334 The formal DTD for the traceframe info format is given below:
40337 <!ELEMENT traceframe-info (memory)* >
40338 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40340 <!ELEMENT memory EMPTY>
40341 <!ATTLIST memory start CDATA #REQUIRED
40342 length CDATA #REQUIRED>
40345 @include agentexpr.texi
40347 @node Target Descriptions
40348 @appendix Target Descriptions
40349 @cindex target descriptions
40351 One of the challenges of using @value{GDBN} to debug embedded systems
40352 is that there are so many minor variants of each processor
40353 architecture in use. It is common practice for vendors to start with
40354 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40355 and then make changes to adapt it to a particular market niche. Some
40356 architectures have hundreds of variants, available from dozens of
40357 vendors. This leads to a number of problems:
40361 With so many different customized processors, it is difficult for
40362 the @value{GDBN} maintainers to keep up with the changes.
40364 Since individual variants may have short lifetimes or limited
40365 audiences, it may not be worthwhile to carry information about every
40366 variant in the @value{GDBN} source tree.
40368 When @value{GDBN} does support the architecture of the embedded system
40369 at hand, the task of finding the correct architecture name to give the
40370 @command{set architecture} command can be error-prone.
40373 To address these problems, the @value{GDBN} remote protocol allows a
40374 target system to not only identify itself to @value{GDBN}, but to
40375 actually describe its own features. This lets @value{GDBN} support
40376 processor variants it has never seen before --- to the extent that the
40377 descriptions are accurate, and that @value{GDBN} understands them.
40379 @value{GDBN} must be linked with the Expat library to support XML
40380 target descriptions. @xref{Expat}.
40383 * Retrieving Descriptions:: How descriptions are fetched from a target.
40384 * Target Description Format:: The contents of a target description.
40385 * Predefined Target Types:: Standard types available for target
40387 * Standard Target Features:: Features @value{GDBN} knows about.
40390 @node Retrieving Descriptions
40391 @section Retrieving Descriptions
40393 Target descriptions can be read from the target automatically, or
40394 specified by the user manually. The default behavior is to read the
40395 description from the target. @value{GDBN} retrieves it via the remote
40396 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40397 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40398 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40399 XML document, of the form described in @ref{Target Description
40402 Alternatively, you can specify a file to read for the target description.
40403 If a file is set, the target will not be queried. The commands to
40404 specify a file are:
40407 @cindex set tdesc filename
40408 @item set tdesc filename @var{path}
40409 Read the target description from @var{path}.
40411 @cindex unset tdesc filename
40412 @item unset tdesc filename
40413 Do not read the XML target description from a file. @value{GDBN}
40414 will use the description supplied by the current target.
40416 @cindex show tdesc filename
40417 @item show tdesc filename
40418 Show the filename to read for a target description, if any.
40422 @node Target Description Format
40423 @section Target Description Format
40424 @cindex target descriptions, XML format
40426 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40427 document which complies with the Document Type Definition provided in
40428 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40429 means you can use generally available tools like @command{xmllint} to
40430 check that your feature descriptions are well-formed and valid.
40431 However, to help people unfamiliar with XML write descriptions for
40432 their targets, we also describe the grammar here.
40434 Target descriptions can identify the architecture of the remote target
40435 and (for some architectures) provide information about custom register
40436 sets. They can also identify the OS ABI of the remote target.
40437 @value{GDBN} can use this information to autoconfigure for your
40438 target, or to warn you if you connect to an unsupported target.
40440 Here is a simple target description:
40443 <target version="1.0">
40444 <architecture>i386:x86-64</architecture>
40449 This minimal description only says that the target uses
40450 the x86-64 architecture.
40452 A target description has the following overall form, with [ ] marking
40453 optional elements and @dots{} marking repeatable elements. The elements
40454 are explained further below.
40457 <?xml version="1.0"?>
40458 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40459 <target version="1.0">
40460 @r{[}@var{architecture}@r{]}
40461 @r{[}@var{osabi}@r{]}
40462 @r{[}@var{compatible}@r{]}
40463 @r{[}@var{feature}@dots{}@r{]}
40468 The description is generally insensitive to whitespace and line
40469 breaks, under the usual common-sense rules. The XML version
40470 declaration and document type declaration can generally be omitted
40471 (@value{GDBN} does not require them), but specifying them may be
40472 useful for XML validation tools. The @samp{version} attribute for
40473 @samp{<target>} may also be omitted, but we recommend
40474 including it; if future versions of @value{GDBN} use an incompatible
40475 revision of @file{gdb-target.dtd}, they will detect and report
40476 the version mismatch.
40478 @subsection Inclusion
40479 @cindex target descriptions, inclusion
40482 @cindex <xi:include>
40485 It can sometimes be valuable to split a target description up into
40486 several different annexes, either for organizational purposes, or to
40487 share files between different possible target descriptions. You can
40488 divide a description into multiple files by replacing any element of
40489 the target description with an inclusion directive of the form:
40492 <xi:include href="@var{document}"/>
40496 When @value{GDBN} encounters an element of this form, it will retrieve
40497 the named XML @var{document}, and replace the inclusion directive with
40498 the contents of that document. If the current description was read
40499 using @samp{qXfer}, then so will be the included document;
40500 @var{document} will be interpreted as the name of an annex. If the
40501 current description was read from a file, @value{GDBN} will look for
40502 @var{document} as a file in the same directory where it found the
40503 original description.
40505 @subsection Architecture
40506 @cindex <architecture>
40508 An @samp{<architecture>} element has this form:
40511 <architecture>@var{arch}</architecture>
40514 @var{arch} is one of the architectures from the set accepted by
40515 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40518 @cindex @code{<osabi>}
40520 This optional field was introduced in @value{GDBN} version 7.0.
40521 Previous versions of @value{GDBN} ignore it.
40523 An @samp{<osabi>} element has this form:
40526 <osabi>@var{abi-name}</osabi>
40529 @var{abi-name} is an OS ABI name from the same selection accepted by
40530 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40532 @subsection Compatible Architecture
40533 @cindex @code{<compatible>}
40535 This optional field was introduced in @value{GDBN} version 7.0.
40536 Previous versions of @value{GDBN} ignore it.
40538 A @samp{<compatible>} element has this form:
40541 <compatible>@var{arch}</compatible>
40544 @var{arch} is one of the architectures from the set accepted by
40545 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40547 A @samp{<compatible>} element is used to specify that the target
40548 is able to run binaries in some other than the main target architecture
40549 given by the @samp{<architecture>} element. For example, on the
40550 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40551 or @code{powerpc:common64}, but the system is able to run binaries
40552 in the @code{spu} architecture as well. The way to describe this
40553 capability with @samp{<compatible>} is as follows:
40556 <architecture>powerpc:common</architecture>
40557 <compatible>spu</compatible>
40560 @subsection Features
40563 Each @samp{<feature>} describes some logical portion of the target
40564 system. Features are currently used to describe available CPU
40565 registers and the types of their contents. A @samp{<feature>} element
40569 <feature name="@var{name}">
40570 @r{[}@var{type}@dots{}@r{]}
40576 Each feature's name should be unique within the description. The name
40577 of a feature does not matter unless @value{GDBN} has some special
40578 knowledge of the contents of that feature; if it does, the feature
40579 should have its standard name. @xref{Standard Target Features}.
40583 Any register's value is a collection of bits which @value{GDBN} must
40584 interpret. The default interpretation is a two's complement integer,
40585 but other types can be requested by name in the register description.
40586 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40587 Target Types}), and the description can define additional composite types.
40589 Each type element must have an @samp{id} attribute, which gives
40590 a unique (within the containing @samp{<feature>}) name to the type.
40591 Types must be defined before they are used.
40594 Some targets offer vector registers, which can be treated as arrays
40595 of scalar elements. These types are written as @samp{<vector>} elements,
40596 specifying the array element type, @var{type}, and the number of elements,
40600 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40604 If a register's value is usefully viewed in multiple ways, define it
40605 with a union type containing the useful representations. The
40606 @samp{<union>} element contains one or more @samp{<field>} elements,
40607 each of which has a @var{name} and a @var{type}:
40610 <union id="@var{id}">
40611 <field name="@var{name}" type="@var{type}"/>
40617 If a register's value is composed from several separate values, define
40618 it with a structure type. There are two forms of the @samp{<struct>}
40619 element; a @samp{<struct>} element must either contain only bitfields
40620 or contain no bitfields. If the structure contains only bitfields,
40621 its total size in bytes must be specified, each bitfield must have an
40622 explicit start and end, and bitfields are automatically assigned an
40623 integer type. The field's @var{start} should be less than or
40624 equal to its @var{end}, and zero represents the least significant bit.
40627 <struct id="@var{id}" size="@var{size}">
40628 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40633 If the structure contains no bitfields, then each field has an
40634 explicit type, and no implicit padding is added.
40637 <struct id="@var{id}">
40638 <field name="@var{name}" type="@var{type}"/>
40644 If a register's value is a series of single-bit flags, define it with
40645 a flags type. The @samp{<flags>} element has an explicit @var{size}
40646 and contains one or more @samp{<field>} elements. Each field has a
40647 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40651 <flags id="@var{id}" size="@var{size}">
40652 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40657 @subsection Registers
40660 Each register is represented as an element with this form:
40663 <reg name="@var{name}"
40664 bitsize="@var{size}"
40665 @r{[}regnum="@var{num}"@r{]}
40666 @r{[}save-restore="@var{save-restore}"@r{]}
40667 @r{[}type="@var{type}"@r{]}
40668 @r{[}group="@var{group}"@r{]}/>
40672 The components are as follows:
40677 The register's name; it must be unique within the target description.
40680 The register's size, in bits.
40683 The register's number. If omitted, a register's number is one greater
40684 than that of the previous register (either in the current feature or in
40685 a preceding feature); the first register in the target description
40686 defaults to zero. This register number is used to read or write
40687 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40688 packets, and registers appear in the @code{g} and @code{G} packets
40689 in order of increasing register number.
40692 Whether the register should be preserved across inferior function
40693 calls; this must be either @code{yes} or @code{no}. The default is
40694 @code{yes}, which is appropriate for most registers except for
40695 some system control registers; this is not related to the target's
40699 The type of the register. @var{type} may be a predefined type, a type
40700 defined in the current feature, or one of the special types @code{int}
40701 and @code{float}. @code{int} is an integer type of the correct size
40702 for @var{bitsize}, and @code{float} is a floating point type (in the
40703 architecture's normal floating point format) of the correct size for
40704 @var{bitsize}. The default is @code{int}.
40707 The register group to which this register belongs. @var{group} must
40708 be either @code{general}, @code{float}, or @code{vector}. If no
40709 @var{group} is specified, @value{GDBN} will not display the register
40710 in @code{info registers}.
40714 @node Predefined Target Types
40715 @section Predefined Target Types
40716 @cindex target descriptions, predefined types
40718 Type definitions in the self-description can build up composite types
40719 from basic building blocks, but can not define fundamental types. Instead,
40720 standard identifiers are provided by @value{GDBN} for the fundamental
40721 types. The currently supported types are:
40730 Signed integer types holding the specified number of bits.
40737 Unsigned integer types holding the specified number of bits.
40741 Pointers to unspecified code and data. The program counter and
40742 any dedicated return address register may be marked as code
40743 pointers; printing a code pointer converts it into a symbolic
40744 address. The stack pointer and any dedicated address registers
40745 may be marked as data pointers.
40748 Single precision IEEE floating point.
40751 Double precision IEEE floating point.
40754 The 12-byte extended precision format used by ARM FPA registers.
40757 The 10-byte extended precision format used by x87 registers.
40760 32bit @sc{eflags} register used by x86.
40763 32bit @sc{mxcsr} register used by x86.
40767 @node Standard Target Features
40768 @section Standard Target Features
40769 @cindex target descriptions, standard features
40771 A target description must contain either no registers or all the
40772 target's registers. If the description contains no registers, then
40773 @value{GDBN} will assume a default register layout, selected based on
40774 the architecture. If the description contains any registers, the
40775 default layout will not be used; the standard registers must be
40776 described in the target description, in such a way that @value{GDBN}
40777 can recognize them.
40779 This is accomplished by giving specific names to feature elements
40780 which contain standard registers. @value{GDBN} will look for features
40781 with those names and verify that they contain the expected registers;
40782 if any known feature is missing required registers, or if any required
40783 feature is missing, @value{GDBN} will reject the target
40784 description. You can add additional registers to any of the
40785 standard features --- @value{GDBN} will display them just as if
40786 they were added to an unrecognized feature.
40788 This section lists the known features and their expected contents.
40789 Sample XML documents for these features are included in the
40790 @value{GDBN} source tree, in the directory @file{gdb/features}.
40792 Names recognized by @value{GDBN} should include the name of the
40793 company or organization which selected the name, and the overall
40794 architecture to which the feature applies; so e.g.@: the feature
40795 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
40797 The names of registers are not case sensitive for the purpose
40798 of recognizing standard features, but @value{GDBN} will only display
40799 registers using the capitalization used in the description.
40802 * AArch64 Features::
40807 * PowerPC Features::
40812 @node AArch64 Features
40813 @subsection AArch64 Features
40814 @cindex target descriptions, AArch64 features
40816 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
40817 targets. It should contain registers @samp{x0} through @samp{x30},
40818 @samp{sp}, @samp{pc}, and @samp{cpsr}.
40820 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
40821 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
40825 @subsection ARM Features
40826 @cindex target descriptions, ARM features
40828 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
40830 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
40831 @samp{lr}, @samp{pc}, and @samp{cpsr}.
40833 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
40834 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
40835 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
40838 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
40839 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
40841 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
40842 it should contain at least registers @samp{wR0} through @samp{wR15} and
40843 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
40844 @samp{wCSSF}, and @samp{wCASF} registers are optional.
40846 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
40847 should contain at least registers @samp{d0} through @samp{d15}. If
40848 they are present, @samp{d16} through @samp{d31} should also be included.
40849 @value{GDBN} will synthesize the single-precision registers from
40850 halves of the double-precision registers.
40852 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
40853 need to contain registers; it instructs @value{GDBN} to display the
40854 VFP double-precision registers as vectors and to synthesize the
40855 quad-precision registers from pairs of double-precision registers.
40856 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
40857 be present and include 32 double-precision registers.
40859 @node i386 Features
40860 @subsection i386 Features
40861 @cindex target descriptions, i386 features
40863 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
40864 targets. It should describe the following registers:
40868 @samp{eax} through @samp{edi} plus @samp{eip} for i386
40870 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
40872 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
40873 @samp{fs}, @samp{gs}
40875 @samp{st0} through @samp{st7}
40877 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
40878 @samp{foseg}, @samp{fooff} and @samp{fop}
40881 The register sets may be different, depending on the target.
40883 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
40884 describe registers:
40888 @samp{xmm0} through @samp{xmm7} for i386
40890 @samp{xmm0} through @samp{xmm15} for amd64
40895 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
40896 @samp{org.gnu.gdb.i386.sse} feature. It should
40897 describe the upper 128 bits of @sc{ymm} registers:
40901 @samp{ymm0h} through @samp{ymm7h} for i386
40903 @samp{ymm0h} through @samp{ymm15h} for amd64
40906 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
40907 describe a single register, @samp{orig_eax}.
40909 @node MIPS Features
40910 @subsection @acronym{MIPS} Features
40911 @cindex target descriptions, @acronym{MIPS} features
40913 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
40914 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
40915 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
40918 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
40919 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
40920 registers. They may be 32-bit or 64-bit depending on the target.
40922 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
40923 it may be optional in a future version of @value{GDBN}. It should
40924 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
40925 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
40927 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
40928 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
40929 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
40930 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
40932 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
40933 contain a single register, @samp{restart}, which is used by the
40934 Linux kernel to control restartable syscalls.
40936 @node M68K Features
40937 @subsection M68K Features
40938 @cindex target descriptions, M68K features
40941 @item @samp{org.gnu.gdb.m68k.core}
40942 @itemx @samp{org.gnu.gdb.coldfire.core}
40943 @itemx @samp{org.gnu.gdb.fido.core}
40944 One of those features must be always present.
40945 The feature that is present determines which flavor of m68k is
40946 used. The feature that is present should contain registers
40947 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
40948 @samp{sp}, @samp{ps} and @samp{pc}.
40950 @item @samp{org.gnu.gdb.coldfire.fp}
40951 This feature is optional. If present, it should contain registers
40952 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
40956 @node PowerPC Features
40957 @subsection PowerPC Features
40958 @cindex target descriptions, PowerPC features
40960 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
40961 targets. It should contain registers @samp{r0} through @samp{r31},
40962 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
40963 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
40965 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
40966 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
40968 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
40969 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
40972 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
40973 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
40974 will combine these registers with the floating point registers
40975 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
40976 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
40977 through @samp{vs63}, the set of vector registers for POWER7.
40979 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
40980 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
40981 @samp{spefscr}. SPE targets should provide 32-bit registers in
40982 @samp{org.gnu.gdb.power.core} and provide the upper halves in
40983 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
40984 these to present registers @samp{ev0} through @samp{ev31} to the
40987 @node TIC6x Features
40988 @subsection TMS320C6x Features
40989 @cindex target descriptions, TIC6x features
40990 @cindex target descriptions, TMS320C6x features
40991 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
40992 targets. It should contain registers @samp{A0} through @samp{A15},
40993 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
40995 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
40996 contain registers @samp{A16} through @samp{A31} and @samp{B16}
40997 through @samp{B31}.
40999 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41000 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41002 @node Operating System Information
41003 @appendix Operating System Information
41004 @cindex operating system information
41010 Users of @value{GDBN} often wish to obtain information about the state of
41011 the operating system running on the target---for example the list of
41012 processes, or the list of open files. This section describes the
41013 mechanism that makes it possible. This mechanism is similar to the
41014 target features mechanism (@pxref{Target Descriptions}), but focuses
41015 on a different aspect of target.
41017 Operating system information is retrived from the target via the
41018 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41019 read}). The object name in the request should be @samp{osdata}, and
41020 the @var{annex} identifies the data to be fetched.
41023 @appendixsection Process list
41024 @cindex operating system information, process list
41026 When requesting the process list, the @var{annex} field in the
41027 @samp{qXfer} request should be @samp{processes}. The returned data is
41028 an XML document. The formal syntax of this document is defined in
41029 @file{gdb/features/osdata.dtd}.
41031 An example document is:
41034 <?xml version="1.0"?>
41035 <!DOCTYPE target SYSTEM "osdata.dtd">
41036 <osdata type="processes">
41038 <column name="pid">1</column>
41039 <column name="user">root</column>
41040 <column name="command">/sbin/init</column>
41041 <column name="cores">1,2,3</column>
41046 Each item should include a column whose name is @samp{pid}. The value
41047 of that column should identify the process on the target. The
41048 @samp{user} and @samp{command} columns are optional, and will be
41049 displayed by @value{GDBN}. The @samp{cores} column, if present,
41050 should contain a comma-separated list of cores that this process
41051 is running on. Target may provide additional columns,
41052 which @value{GDBN} currently ignores.
41054 @node Trace File Format
41055 @appendix Trace File Format
41056 @cindex trace file format
41058 The trace file comes in three parts: a header, a textual description
41059 section, and a trace frame section with binary data.
41061 The header has the form @code{\x7fTRACE0\n}. The first byte is
41062 @code{0x7f} so as to indicate that the file contains binary data,
41063 while the @code{0} is a version number that may have different values
41066 The description section consists of multiple lines of @sc{ascii} text
41067 separated by newline characters (@code{0xa}). The lines may include a
41068 variety of optional descriptive or context-setting information, such
41069 as tracepoint definitions or register set size. @value{GDBN} will
41070 ignore any line that it does not recognize. An empty line marks the end
41073 @c FIXME add some specific types of data
41075 The trace frame section consists of a number of consecutive frames.
41076 Each frame begins with a two-byte tracepoint number, followed by a
41077 four-byte size giving the amount of data in the frame. The data in
41078 the frame consists of a number of blocks, each introduced by a
41079 character indicating its type (at least register, memory, and trace
41080 state variable). The data in this section is raw binary, not a
41081 hexadecimal or other encoding; its endianness matches the target's
41084 @c FIXME bi-arch may require endianness/arch info in description section
41087 @item R @var{bytes}
41088 Register block. The number and ordering of bytes matches that of a
41089 @code{g} packet in the remote protocol. Note that these are the
41090 actual bytes, in target order and @value{GDBN} register order, not a
41091 hexadecimal encoding.
41093 @item M @var{address} @var{length} @var{bytes}...
41094 Memory block. This is a contiguous block of memory, at the 8-byte
41095 address @var{address}, with a 2-byte length @var{length}, followed by
41096 @var{length} bytes.
41098 @item V @var{number} @var{value}
41099 Trace state variable block. This records the 8-byte signed value
41100 @var{value} of trace state variable numbered @var{number}.
41104 Future enhancements of the trace file format may include additional types
41107 @node Index Section Format
41108 @appendix @code{.gdb_index} section format
41109 @cindex .gdb_index section format
41110 @cindex index section format
41112 This section documents the index section that is created by @code{save
41113 gdb-index} (@pxref{Index Files}). The index section is
41114 DWARF-specific; some knowledge of DWARF is assumed in this
41117 The mapped index file format is designed to be directly
41118 @code{mmap}able on any architecture. In most cases, a datum is
41119 represented using a little-endian 32-bit integer value, called an
41120 @code{offset_type}. Big endian machines must byte-swap the values
41121 before using them. Exceptions to this rule are noted. The data is
41122 laid out such that alignment is always respected.
41124 A mapped index consists of several areas, laid out in order.
41128 The file header. This is a sequence of values, of @code{offset_type}
41129 unless otherwise noted:
41133 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41134 Version 4 uses a different hashing function from versions 5 and 6.
41135 Version 6 includes symbols for inlined functions, whereas versions 4
41136 and 5 do not. Version 7 adds attributes to the CU indices in the
41137 symbol table. Version 8 specifies that symbols from DWARF type units
41138 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41139 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41141 @value{GDBN} will only read version 4, 5, or 6 indices
41142 by specifying @code{set use-deprecated-index-sections on}.
41143 GDB has a workaround for potentially broken version 7 indices so it is
41144 currently not flagged as deprecated.
41147 The offset, from the start of the file, of the CU list.
41150 The offset, from the start of the file, of the types CU list. Note
41151 that this area can be empty, in which case this offset will be equal
41152 to the next offset.
41155 The offset, from the start of the file, of the address area.
41158 The offset, from the start of the file, of the symbol table.
41161 The offset, from the start of the file, of the constant pool.
41165 The CU list. This is a sequence of pairs of 64-bit little-endian
41166 values, sorted by the CU offset. The first element in each pair is
41167 the offset of a CU in the @code{.debug_info} section. The second
41168 element in each pair is the length of that CU. References to a CU
41169 elsewhere in the map are done using a CU index, which is just the
41170 0-based index into this table. Note that if there are type CUs, then
41171 conceptually CUs and type CUs form a single list for the purposes of
41175 The types CU list. This is a sequence of triplets of 64-bit
41176 little-endian values. In a triplet, the first value is the CU offset,
41177 the second value is the type offset in the CU, and the third value is
41178 the type signature. The types CU list is not sorted.
41181 The address area. The address area consists of a sequence of address
41182 entries. Each address entry has three elements:
41186 The low address. This is a 64-bit little-endian value.
41189 The high address. This is a 64-bit little-endian value. Like
41190 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41193 The CU index. This is an @code{offset_type} value.
41197 The symbol table. This is an open-addressed hash table. The size of
41198 the hash table is always a power of 2.
41200 Each slot in the hash table consists of a pair of @code{offset_type}
41201 values. The first value is the offset of the symbol's name in the
41202 constant pool. The second value is the offset of the CU vector in the
41205 If both values are 0, then this slot in the hash table is empty. This
41206 is ok because while 0 is a valid constant pool index, it cannot be a
41207 valid index for both a string and a CU vector.
41209 The hash value for a table entry is computed by applying an
41210 iterative hash function to the symbol's name. Starting with an
41211 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41212 the string is incorporated into the hash using the formula depending on the
41217 The formula is @code{r = r * 67 + c - 113}.
41219 @item Versions 5 to 7
41220 The formula is @code{r = r * 67 + tolower (c) - 113}.
41223 The terminating @samp{\0} is not incorporated into the hash.
41225 The step size used in the hash table is computed via
41226 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41227 value, and @samp{size} is the size of the hash table. The step size
41228 is used to find the next candidate slot when handling a hash
41231 The names of C@t{++} symbols in the hash table are canonicalized. We
41232 don't currently have a simple description of the canonicalization
41233 algorithm; if you intend to create new index sections, you must read
41237 The constant pool. This is simply a bunch of bytes. It is organized
41238 so that alignment is correct: CU vectors are stored first, followed by
41241 A CU vector in the constant pool is a sequence of @code{offset_type}
41242 values. The first value is the number of CU indices in the vector.
41243 Each subsequent value is the index and symbol attributes of a CU in
41244 the CU list. This element in the hash table is used to indicate which
41245 CUs define the symbol and how the symbol is used.
41246 See below for the format of each CU index+attributes entry.
41248 A string in the constant pool is zero-terminated.
41251 Attributes were added to CU index values in @code{.gdb_index} version 7.
41252 If a symbol has multiple uses within a CU then there is one
41253 CU index+attributes value for each use.
41255 The format of each CU index+attributes entry is as follows
41261 This is the index of the CU in the CU list.
41263 These bits are reserved for future purposes and must be zero.
41265 The kind of the symbol in the CU.
41269 This value is reserved and should not be used.
41270 By reserving zero the full @code{offset_type} value is backwards compatible
41271 with previous versions of the index.
41273 The symbol is a type.
41275 The symbol is a variable or an enum value.
41277 The symbol is a function.
41279 Any other kind of symbol.
41281 These values are reserved.
41285 This bit is zero if the value is global and one if it is static.
41287 The determination of whether a symbol is global or static is complicated.
41288 The authorative reference is the file @file{dwarf2read.c} in
41289 @value{GDBN} sources.
41293 This pseudo-code describes the computation of a symbol's kind and
41294 global/static attributes in the index.
41297 is_external = get_attribute (die, DW_AT_external);
41298 language = get_attribute (cu_die, DW_AT_language);
41301 case DW_TAG_typedef:
41302 case DW_TAG_base_type:
41303 case DW_TAG_subrange_type:
41307 case DW_TAG_enumerator:
41309 is_static = (language != CPLUS && language != JAVA);
41311 case DW_TAG_subprogram:
41313 is_static = ! (is_external || language == ADA);
41315 case DW_TAG_constant:
41317 is_static = ! is_external;
41319 case DW_TAG_variable:
41321 is_static = ! is_external;
41323 case DW_TAG_namespace:
41327 case DW_TAG_class_type:
41328 case DW_TAG_interface_type:
41329 case DW_TAG_structure_type:
41330 case DW_TAG_union_type:
41331 case DW_TAG_enumeration_type:
41333 is_static = (language != CPLUS && language != JAVA);
41342 @node GNU Free Documentation License
41343 @appendix GNU Free Documentation License
41346 @node Concept Index
41347 @unnumbered Concept Index
41351 @node Command and Variable Index
41352 @unnumbered Command, Variable, and Function Index
41357 % I think something like @@colophon should be in texinfo. In the
41359 \long\def\colophon{\hbox to0pt{}\vfill
41360 \centerline{The body of this manual is set in}
41361 \centerline{\fontname\tenrm,}
41362 \centerline{with headings in {\bf\fontname\tenbf}}
41363 \centerline{and examples in {\tt\fontname\tentt}.}
41364 \centerline{{\it\fontname\tenit\/},}
41365 \centerline{{\bf\fontname\tenbf}, and}
41366 \centerline{{\sl\fontname\tensl\/}}
41367 \centerline{are used for emphasis.}\vfill}
41369 % Blame: doc@@cygnus.com, 1991.