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
6120 @kindex target record-full
6121 @kindex target record-btrace
6124 @kindex record btrace
6128 @item record @var{method}
6129 This command starts the process record and replay target. The
6130 recording method can be specified as parameter. Without a parameter
6131 the command uses the @code{full} recording method. The following
6132 recording methods are available:
6136 Full record/replay recording using @value{GDBN}'s software record and
6137 replay implementation. This method allows replaying and reverse
6141 Hardware-supported instruction recording. This method does not allow
6142 replaying and reverse execution.
6144 This recording method may not be available on all processors.
6147 The process record and replay target can only debug a process that is
6148 already running. Therefore, you need first to start the process with
6149 the @kbd{run} or @kbd{start} commands, and then start the recording
6150 with the @kbd{record @var{method}} command.
6152 Both @code{record @var{method}} and @code{rec @var{method}} are
6153 aliases of @code{target record-@var{method}}.
6155 @cindex displaced stepping, and process record and replay
6156 Displaced stepping (@pxref{Maintenance Commands,, displaced stepping})
6157 will be automatically disabled when process record and replay target
6158 is started. That's because the process record and replay target
6159 doesn't support displaced stepping.
6161 @cindex non-stop mode, and process record and replay
6162 @cindex asynchronous execution, and process record and replay
6163 If the inferior is in the non-stop mode (@pxref{Non-Stop Mode}) or in
6164 the asynchronous execution mode (@pxref{Background Execution}), not
6165 all recording methods are available. The @code{full} recording method
6166 does not support these two modes.
6171 Stop the process record and replay target. When process record and
6172 replay target stops, the entire execution log will be deleted and the
6173 inferior will either be terminated, or will remain in its final state.
6175 When you stop the process record and replay target in record mode (at
6176 the end of the execution log), the inferior will be stopped at the
6177 next instruction that would have been recorded. In other words, if
6178 you record for a while and then stop recording, the inferior process
6179 will be left in the same state as if the recording never happened.
6181 On the other hand, if the process record and replay target is stopped
6182 while in replay mode (that is, not at the end of the execution log,
6183 but at some earlier point), the inferior process will become ``live''
6184 at that earlier state, and it will then be possible to continue the
6185 usual ``live'' debugging of the process from that state.
6187 When the inferior process exits, or @value{GDBN} detaches from it,
6188 process record and replay target will automatically stop itself.
6191 @item record save @var{filename}
6192 Save the execution log to a file @file{@var{filename}}.
6193 Default filename is @file{gdb_record.@var{process_id}}, where
6194 @var{process_id} is the process ID of the inferior.
6196 This command may not be available for all recording methods.
6198 @kindex record restore
6199 @item record restore @var{filename}
6200 Restore the execution log from a file @file{@var{filename}}.
6201 File must have been created with @code{record save}.
6203 @kindex set record full
6204 @item set record full insn-number-max @var{limit}
6205 Set the limit of instructions to be recorded for the @code{full}
6206 recording method. Default value is 200000.
6208 If @var{limit} is a positive number, then @value{GDBN} will start
6209 deleting instructions from the log once the number of the record
6210 instructions becomes greater than @var{limit}. For every new recorded
6211 instruction, @value{GDBN} will delete the earliest recorded
6212 instruction to keep the number of recorded instructions at the limit.
6213 (Since deleting recorded instructions loses information, @value{GDBN}
6214 lets you control what happens when the limit is reached, by means of
6215 the @code{stop-at-limit} option, described below.)
6217 If @var{limit} is zero, @value{GDBN} will never delete recorded
6218 instructions from the execution log. The number of recorded
6219 instructions is unlimited in this case.
6221 @kindex show record full
6222 @item show record full insn-number-max
6223 Show the limit of instructions to be recorded with the @code{full}
6226 @item set record full stop-at-limit
6227 Control the behavior of the @code{full} recording method when the
6228 number of recorded instructions reaches the limit. If ON (the
6229 default), @value{GDBN} will stop when the limit is reached for the
6230 first time and ask you whether you want to stop the inferior or
6231 continue running it and recording the execution log. If you decide
6232 to continue recording, each new recorded instruction will cause the
6233 oldest one to be deleted.
6235 If this option is OFF, @value{GDBN} will automatically delete the
6236 oldest record to make room for each new one, without asking.
6238 @item show record full stop-at-limit
6239 Show the current setting of @code{stop-at-limit}.
6241 @item set record full memory-query
6242 Control the behavior when @value{GDBN} is unable to record memory
6243 changes caused by an instruction for the @code{full} recording method.
6244 If ON, @value{GDBN} will query whether to stop the inferior in that
6247 If this option is OFF (the default), @value{GDBN} will automatically
6248 ignore the effect of such instructions on memory. Later, when
6249 @value{GDBN} replays this execution log, it will mark the log of this
6250 instruction as not accessible, and it will not affect the replay
6253 @item show record full memory-query
6254 Show the current setting of @code{memory-query}.
6258 Show various statistics about the recording depending on the recording
6263 For the @code{full} recording method, it shows the state of process
6264 record and its in-memory execution log buffer, including:
6268 Whether in record mode or replay mode.
6270 Lowest recorded instruction number (counting from when the current execution log started recording instructions).
6272 Highest recorded instruction number.
6274 Current instruction about to be replayed (if in replay mode).
6276 Number of instructions contained in the execution log.
6278 Maximum number of instructions that may be contained in the execution log.
6282 For the @code{btrace} recording method, it shows the number of
6283 instructions that have been recorded and the number of blocks of
6284 sequential control-flow that is formed by the recorded instructions.
6287 @kindex record delete
6290 When record target runs in replay mode (``in the past''), delete the
6291 subsequent execution log and begin to record a new execution log starting
6292 from the current address. This means you will abandon the previously
6293 recorded ``future'' and begin recording a new ``future''.
6295 @kindex record instruction-history
6296 @kindex rec instruction-history
6297 @item record instruction-history
6298 Disassembles instructions from the recorded execution log. By
6299 default, ten instructions are disassembled. This can be changed using
6300 the @code{set record instruction-history-size} command. Instructions
6301 are printed in execution order. There are several ways to specify
6302 what part of the execution log to disassemble:
6305 @item record instruction-history @var{insn}
6306 Disassembles ten instructions starting from instruction number
6309 @item record instruction-history @var{insn}, +/-@var{n}
6310 Disassembles @var{n} instructions around instruction number
6311 @var{insn}. If @var{n} is preceded with @code{+}, disassembles
6312 @var{n} instructions after instruction number @var{insn}. If
6313 @var{n} is preceded with @code{-}, disassembles @var{n}
6314 instructions before instruction number @var{insn}.
6316 @item record instruction-history
6317 Disassembles ten more instructions after the last disassembly.
6319 @item record instruction-history -
6320 Disassembles ten more instructions before the last disassembly.
6322 @item record instruction-history @var{begin} @var{end}
6323 Disassembles instructions beginning with instruction number
6324 @var{begin} until instruction number @var{end}. The instruction
6325 number @var{end} is not included.
6328 This command may not be available for all recording methods.
6331 @item set record instruction-history-size
6332 Define how many instructions to disassemble in the @code{record
6333 instruction-history} command. The default value is 10.
6336 @item show record instruction-history-size
6337 Show how many instructions to disassemble in the @code{record
6338 instruction-history} command.
6340 @kindex record function-call-history
6341 @kindex rec function-call-history
6342 @item record function-call-history
6343 Prints the execution history at function granularity. It prints one
6344 line for each sequence of instructions that belong to the same
6345 function giving the name of that function, the source lines
6346 for this instruction sequence (if the @code{/l} modifier is
6347 specified), and the instructions numbers that form the sequence (if
6348 the @code{/i} modifier is specified).
6351 (@value{GDBP}) @b{list 1, 10}
6362 (@value{GDBP}) @b{record function-call-history /l}
6368 By default, ten lines are printed. This can be changed using the
6369 @code{set record function-call-history-size} command. Functions are
6370 printed in execution order. There are several ways to specify what
6374 @item record function-call-history @var{func}
6375 Prints ten functions starting from function number @var{func}.
6377 @item record function-call-history @var{func}, +/-@var{n}
6378 Prints @var{n} functions around function number @var{func}. If
6379 @var{n} is preceded with @code{+}, prints @var{n} functions after
6380 function number @var{func}. If @var{n} is preceded with @code{-},
6381 prints @var{n} functions before function number @var{func}.
6383 @item record function-call-history
6384 Prints ten more functions after the last ten-line print.
6386 @item record function-call-history -
6387 Prints ten more functions before the last ten-line print.
6389 @item record function-call-history @var{begin} @var{end}
6390 Prints functions beginning with function number @var{begin} until
6391 function number @var{end}. The function number @var{end} is not
6395 This command may not be available for all recording methods.
6397 @item set record function-call-history-size
6398 Define how many lines to print in the
6399 @code{record function-call-history} command. The default value is 10.
6401 @item show record function-call-history-size
6402 Show how many lines to print in the
6403 @code{record function-call-history} command.
6408 @chapter Examining the Stack
6410 When your program has stopped, the first thing you need to know is where it
6411 stopped and how it got there.
6414 Each time your program performs a function call, information about the call
6416 That information includes the location of the call in your program,
6417 the arguments of the call,
6418 and the local variables of the function being called.
6419 The information is saved in a block of data called a @dfn{stack frame}.
6420 The stack frames are allocated in a region of memory called the @dfn{call
6423 When your program stops, the @value{GDBN} commands for examining the
6424 stack allow you to see all of this information.
6426 @cindex selected frame
6427 One of the stack frames is @dfn{selected} by @value{GDBN} and many
6428 @value{GDBN} commands refer implicitly to the selected frame. In
6429 particular, whenever you ask @value{GDBN} for the value of a variable in
6430 your program, the value is found in the selected frame. There are
6431 special @value{GDBN} commands to select whichever frame you are
6432 interested in. @xref{Selection, ,Selecting a Frame}.
6434 When your program stops, @value{GDBN} automatically selects the
6435 currently executing frame and describes it briefly, similar to the
6436 @code{frame} command (@pxref{Frame Info, ,Information about a Frame}).
6439 * Frames:: Stack frames
6440 * Backtrace:: Backtraces
6441 * Selection:: Selecting a frame
6442 * Frame Info:: Information on a frame
6447 @section Stack Frames
6449 @cindex frame, definition
6451 The call stack is divided up into contiguous pieces called @dfn{stack
6452 frames}, or @dfn{frames} for short; each frame is the data associated
6453 with one call to one function. The frame contains the arguments given
6454 to the function, the function's local variables, and the address at
6455 which the function is executing.
6457 @cindex initial frame
6458 @cindex outermost frame
6459 @cindex innermost frame
6460 When your program is started, the stack has only one frame, that of the
6461 function @code{main}. This is called the @dfn{initial} frame or the
6462 @dfn{outermost} frame. Each time a function is called, a new frame is
6463 made. Each time a function returns, the frame for that function invocation
6464 is eliminated. If a function is recursive, there can be many frames for
6465 the same function. The frame for the function in which execution is
6466 actually occurring is called the @dfn{innermost} frame. This is the most
6467 recently created of all the stack frames that still exist.
6469 @cindex frame pointer
6470 Inside your program, stack frames are identified by their addresses. A
6471 stack frame consists of many bytes, each of which has its own address; each
6472 kind of computer has a convention for choosing one byte whose
6473 address serves as the address of the frame. Usually this address is kept
6474 in a register called the @dfn{frame pointer register}
6475 (@pxref{Registers, $fp}) while execution is going on in that frame.
6477 @cindex frame number
6478 @value{GDBN} assigns numbers to all existing stack frames, starting with
6479 zero for the innermost frame, one for the frame that called it,
6480 and so on upward. These numbers do not really exist in your program;
6481 they are assigned by @value{GDBN} to give you a way of designating stack
6482 frames in @value{GDBN} commands.
6484 @c The -fomit-frame-pointer below perennially causes hbox overflow
6485 @c underflow problems.
6486 @cindex frameless execution
6487 Some compilers provide a way to compile functions so that they operate
6488 without stack frames. (For example, the @value{NGCC} option
6490 @samp{-fomit-frame-pointer}
6492 generates functions without a frame.)
6493 This is occasionally done with heavily used library functions to save
6494 the frame setup time. @value{GDBN} has limited facilities for dealing
6495 with these function invocations. If the innermost function invocation
6496 has no stack frame, @value{GDBN} nevertheless regards it as though
6497 it had a separate frame, which is numbered zero as usual, allowing
6498 correct tracing of the function call chain. However, @value{GDBN} has
6499 no provision for frameless functions elsewhere in the stack.
6502 @kindex frame@r{, command}
6503 @cindex current stack frame
6504 @item frame @var{args}
6505 The @code{frame} command allows you to move from one stack frame to another,
6506 and to print the stack frame you select. @var{args} may be either the
6507 address of the frame or the stack frame number. Without an argument,
6508 @code{frame} prints the current stack frame.
6510 @kindex select-frame
6511 @cindex selecting frame silently
6513 The @code{select-frame} command allows you to move from one stack frame
6514 to another without printing the frame. This is the silent version of
6522 @cindex call stack traces
6523 A backtrace is a summary of how your program got where it is. It shows one
6524 line per frame, for many frames, starting with the currently executing
6525 frame (frame zero), followed by its caller (frame one), and on up the
6530 @kindex bt @r{(@code{backtrace})}
6533 Print a backtrace of the entire stack: one line per frame for all
6534 frames in the stack.
6536 You can stop the backtrace at any time by typing the system interrupt
6537 character, normally @kbd{Ctrl-c}.
6539 @item backtrace @var{n}
6541 Similar, but print only the innermost @var{n} frames.
6543 @item backtrace -@var{n}
6545 Similar, but print only the outermost @var{n} frames.
6547 @item backtrace full
6549 @itemx bt full @var{n}
6550 @itemx bt full -@var{n}
6551 Print the values of the local variables also. @var{n} specifies the
6552 number of frames to print, as described above.
6557 The names @code{where} and @code{info stack} (abbreviated @code{info s})
6558 are additional aliases for @code{backtrace}.
6560 @cindex multiple threads, backtrace
6561 In a multi-threaded program, @value{GDBN} by default shows the
6562 backtrace only for the current thread. To display the backtrace for
6563 several or all of the threads, use the command @code{thread apply}
6564 (@pxref{Threads, thread apply}). For example, if you type @kbd{thread
6565 apply all backtrace}, @value{GDBN} will display the backtrace for all
6566 the threads; this is handy when you debug a core dump of a
6567 multi-threaded program.
6569 Each line in the backtrace shows the frame number and the function name.
6570 The program counter value is also shown---unless you use @code{set
6571 print address off}. The backtrace also shows the source file name and
6572 line number, as well as the arguments to the function. The program
6573 counter value is omitted if it is at the beginning of the code for that
6576 Here is an example of a backtrace. It was made with the command
6577 @samp{bt 3}, so it shows the innermost three frames.
6581 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6583 #1 0x6e38 in expand_macro (sym=0x2b600, data=...) at macro.c:242
6584 #2 0x6840 in expand_token (obs=0x0, t=177664, td=0xf7fffb08)
6586 (More stack frames follow...)
6591 The display for frame zero does not begin with a program counter
6592 value, indicating that your program has stopped at the beginning of the
6593 code for line @code{993} of @code{builtin.c}.
6596 The value of parameter @code{data} in frame 1 has been replaced by
6597 @code{@dots{}}. By default, @value{GDBN} prints the value of a parameter
6598 only if it is a scalar (integer, pointer, enumeration, etc). See command
6599 @kbd{set print frame-arguments} in @ref{Print Settings} for more details
6600 on how to configure the way function parameter values are printed.
6602 @cindex optimized out, in backtrace
6603 @cindex function call arguments, optimized out
6604 If your program was compiled with optimizations, some compilers will
6605 optimize away arguments passed to functions if those arguments are
6606 never used after the call. Such optimizations generate code that
6607 passes arguments through registers, but doesn't store those arguments
6608 in the stack frame. @value{GDBN} has no way of displaying such
6609 arguments in stack frames other than the innermost one. Here's what
6610 such a backtrace might look like:
6614 #0 m4_traceon (obs=0x24eb0, argc=1, argv=0x2b8c8)
6616 #1 0x6e38 in expand_macro (sym=<optimized out>) at macro.c:242
6617 #2 0x6840 in expand_token (obs=0x0, t=<optimized out>, td=0xf7fffb08)
6619 (More stack frames follow...)
6624 The values of arguments that were not saved in their stack frames are
6625 shown as @samp{<optimized out>}.
6627 If you need to display the values of such optimized-out arguments,
6628 either deduce that from other variables whose values depend on the one
6629 you are interested in, or recompile without optimizations.
6631 @cindex backtrace beyond @code{main} function
6632 @cindex program entry point
6633 @cindex startup code, and backtrace
6634 Most programs have a standard user entry point---a place where system
6635 libraries and startup code transition into user code. For C this is
6636 @code{main}@footnote{
6637 Note that embedded programs (the so-called ``free-standing''
6638 environment) are not required to have a @code{main} function as the
6639 entry point. They could even have multiple entry points.}.
6640 When @value{GDBN} finds the entry function in a backtrace
6641 it will terminate the backtrace, to avoid tracing into highly
6642 system-specific (and generally uninteresting) code.
6644 If you need to examine the startup code, or limit the number of levels
6645 in a backtrace, you can change this behavior:
6648 @item set backtrace past-main
6649 @itemx set backtrace past-main on
6650 @kindex set backtrace
6651 Backtraces will continue past the user entry point.
6653 @item set backtrace past-main off
6654 Backtraces will stop when they encounter the user entry point. This is the
6657 @item show backtrace past-main
6658 @kindex show backtrace
6659 Display the current user entry point backtrace policy.
6661 @item set backtrace past-entry
6662 @itemx set backtrace past-entry on
6663 Backtraces will continue past the internal entry point of an application.
6664 This entry point is encoded by the linker when the application is built,
6665 and is likely before the user entry point @code{main} (or equivalent) is called.
6667 @item set backtrace past-entry off
6668 Backtraces will stop when they encounter the internal entry point of an
6669 application. This is the default.
6671 @item show backtrace past-entry
6672 Display the current internal entry point backtrace policy.
6674 @item set backtrace limit @var{n}
6675 @itemx set backtrace limit 0
6676 @cindex backtrace limit
6677 Limit the backtrace to @var{n} levels. A value of zero means
6680 @item show backtrace limit
6681 Display the current limit on backtrace levels.
6684 You can control how file names are displayed.
6687 @item set filename-display
6688 @itemx set filename-display relative
6689 @cindex filename-display
6690 Display file names relative to the compilation directory. This is the default.
6692 @item set filename-display basename
6693 Display only basename of a filename.
6695 @item set filename-display absolute
6696 Display an absolute filename.
6698 @item show filename-display
6699 Show the current way to display filenames.
6703 @section Selecting a Frame
6705 Most commands for examining the stack and other data in your program work on
6706 whichever stack frame is selected at the moment. Here are the commands for
6707 selecting a stack frame; all of them finish by printing a brief description
6708 of the stack frame just selected.
6711 @kindex frame@r{, selecting}
6712 @kindex f @r{(@code{frame})}
6715 Select frame number @var{n}. Recall that frame zero is the innermost
6716 (currently executing) frame, frame one is the frame that called the
6717 innermost one, and so on. The highest-numbered frame is the one for
6720 @item frame @var{addr}
6722 Select the frame at address @var{addr}. This is useful mainly if the
6723 chaining of stack frames has been damaged by a bug, making it
6724 impossible for @value{GDBN} to assign numbers properly to all frames. In
6725 addition, this can be useful when your program has multiple stacks and
6726 switches between them.
6728 On the SPARC architecture, @code{frame} needs two addresses to
6729 select an arbitrary frame: a frame pointer and a stack pointer.
6731 On the @acronym{MIPS} and Alpha architecture, it needs two addresses: a stack
6732 pointer and a program counter.
6734 On the 29k architecture, it needs three addresses: a register stack
6735 pointer, a program counter, and a memory stack pointer.
6739 Move @var{n} frames up the stack. For positive numbers @var{n}, this
6740 advances toward the outermost frame, to higher frame numbers, to frames
6741 that have existed longer. @var{n} defaults to one.
6744 @kindex do @r{(@code{down})}
6746 Move @var{n} frames down the stack. For positive numbers @var{n}, this
6747 advances toward the innermost frame, to lower frame numbers, to frames
6748 that were created more recently. @var{n} defaults to one. You may
6749 abbreviate @code{down} as @code{do}.
6752 All of these commands end by printing two lines of output describing the
6753 frame. The first line shows the frame number, the function name, the
6754 arguments, and the source file and line number of execution in that
6755 frame. The second line shows the text of that source line.
6763 #1 0x22f0 in main (argc=1, argv=0xf7fffbf4, env=0xf7fffbfc)
6765 10 read_input_file (argv[i]);
6769 After such a printout, the @code{list} command with no arguments
6770 prints ten lines centered on the point of execution in the frame.
6771 You can also edit the program at the point of execution with your favorite
6772 editing program by typing @code{edit}.
6773 @xref{List, ,Printing Source Lines},
6777 @kindex down-silently
6779 @item up-silently @var{n}
6780 @itemx down-silently @var{n}
6781 These two commands are variants of @code{up} and @code{down},
6782 respectively; they differ in that they do their work silently, without
6783 causing display of the new frame. They are intended primarily for use
6784 in @value{GDBN} command scripts, where the output might be unnecessary and
6789 @section Information About a Frame
6791 There are several other commands to print information about the selected
6797 When used without any argument, this command does not change which
6798 frame is selected, but prints a brief description of the currently
6799 selected stack frame. It can be abbreviated @code{f}. With an
6800 argument, this command is used to select a stack frame.
6801 @xref{Selection, ,Selecting a Frame}.
6804 @kindex info f @r{(@code{info frame})}
6807 This command prints a verbose description of the selected stack frame,
6812 the address of the frame
6814 the address of the next frame down (called by this frame)
6816 the address of the next frame up (caller of this frame)
6818 the language in which the source code corresponding to this frame is written
6820 the address of the frame's arguments
6822 the address of the frame's local variables
6824 the program counter saved in it (the address of execution in the caller frame)
6826 which registers were saved in the frame
6829 @noindent The verbose description is useful when
6830 something has gone wrong that has made the stack format fail to fit
6831 the usual conventions.
6833 @item info frame @var{addr}
6834 @itemx info f @var{addr}
6835 Print a verbose description of the frame at address @var{addr}, without
6836 selecting that frame. The selected frame remains unchanged by this
6837 command. This requires the same kind of address (more than one for some
6838 architectures) that you specify in the @code{frame} command.
6839 @xref{Selection, ,Selecting a Frame}.
6843 Print the arguments of the selected frame, each on a separate line.
6847 Print the local variables of the selected frame, each on a separate
6848 line. These are all variables (declared either static or automatic)
6849 accessible at the point of execution of the selected frame.
6855 @chapter Examining Source Files
6857 @value{GDBN} can print parts of your program's source, since the debugging
6858 information recorded in the program tells @value{GDBN} what source files were
6859 used to build it. When your program stops, @value{GDBN} spontaneously prints
6860 the line where it stopped. Likewise, when you select a stack frame
6861 (@pxref{Selection, ,Selecting a Frame}), @value{GDBN} prints the line where
6862 execution in that frame has stopped. You can print other portions of
6863 source files by explicit command.
6865 If you use @value{GDBN} through its @sc{gnu} Emacs interface, you may
6866 prefer to use Emacs facilities to view source; see @ref{Emacs, ,Using
6867 @value{GDBN} under @sc{gnu} Emacs}.
6870 * List:: Printing source lines
6871 * Specify Location:: How to specify code locations
6872 * Edit:: Editing source files
6873 * Search:: Searching source files
6874 * Source Path:: Specifying source directories
6875 * Machine Code:: Source and machine code
6879 @section Printing Source Lines
6882 @kindex l @r{(@code{list})}
6883 To print lines from a source file, use the @code{list} command
6884 (abbreviated @code{l}). By default, ten lines are printed.
6885 There are several ways to specify what part of the file you want to
6886 print; see @ref{Specify Location}, for the full list.
6888 Here are the forms of the @code{list} command most commonly used:
6891 @item list @var{linenum}
6892 Print lines centered around line number @var{linenum} in the
6893 current source file.
6895 @item list @var{function}
6896 Print lines centered around the beginning of function
6900 Print more lines. If the last lines printed were printed with a
6901 @code{list} command, this prints lines following the last lines
6902 printed; however, if the last line printed was a solitary line printed
6903 as part of displaying a stack frame (@pxref{Stack, ,Examining the
6904 Stack}), this prints lines centered around that line.
6907 Print lines just before the lines last printed.
6910 @cindex @code{list}, how many lines to display
6911 By default, @value{GDBN} prints ten source lines with any of these forms of
6912 the @code{list} command. You can change this using @code{set listsize}:
6915 @kindex set listsize
6916 @item set listsize @var{count}
6917 Make the @code{list} command display @var{count} source lines (unless
6918 the @code{list} argument explicitly specifies some other number).
6919 Setting @var{count} to -1 means there's no limit and 0 means suppress
6920 display of source lines.
6922 @kindex show listsize
6924 Display the number of lines that @code{list} prints.
6927 Repeating a @code{list} command with @key{RET} discards the argument,
6928 so it is equivalent to typing just @code{list}. This is more useful
6929 than listing the same lines again. An exception is made for an
6930 argument of @samp{-}; that argument is preserved in repetition so that
6931 each repetition moves up in the source file.
6933 In general, the @code{list} command expects you to supply zero, one or two
6934 @dfn{linespecs}. Linespecs specify source lines; there are several ways
6935 of writing them (@pxref{Specify Location}), but the effect is always
6936 to specify some source line.
6938 Here is a complete description of the possible arguments for @code{list}:
6941 @item list @var{linespec}
6942 Print lines centered around the line specified by @var{linespec}.
6944 @item list @var{first},@var{last}
6945 Print lines from @var{first} to @var{last}. Both arguments are
6946 linespecs. When a @code{list} command has two linespecs, and the
6947 source file of the second linespec is omitted, this refers to
6948 the same source file as the first linespec.
6950 @item list ,@var{last}
6951 Print lines ending with @var{last}.
6953 @item list @var{first},
6954 Print lines starting with @var{first}.
6957 Print lines just after the lines last printed.
6960 Print lines just before the lines last printed.
6963 As described in the preceding table.
6966 @node Specify Location
6967 @section Specifying a Location
6968 @cindex specifying location
6971 Several @value{GDBN} commands accept arguments that specify a location
6972 of your program's code. Since @value{GDBN} is a source-level
6973 debugger, a location usually specifies some line in the source code;
6974 for that reason, locations are also known as @dfn{linespecs}.
6976 Here are all the different ways of specifying a code location that
6977 @value{GDBN} understands:
6981 Specifies the line number @var{linenum} of the current source file.
6984 @itemx +@var{offset}
6985 Specifies the line @var{offset} lines before or after the @dfn{current
6986 line}. For the @code{list} command, the current line is the last one
6987 printed; for the breakpoint commands, this is the line at which
6988 execution stopped in the currently selected @dfn{stack frame}
6989 (@pxref{Frames, ,Frames}, for a description of stack frames.) When
6990 used as the second of the two linespecs in a @code{list} command,
6991 this specifies the line @var{offset} lines up or down from the first
6994 @item @var{filename}:@var{linenum}
6995 Specifies the line @var{linenum} in the source file @var{filename}.
6996 If @var{filename} is a relative file name, then it will match any
6997 source file name with the same trailing components. For example, if
6998 @var{filename} is @samp{gcc/expr.c}, then it will match source file
6999 name of @file{/build/trunk/gcc/expr.c}, but not
7000 @file{/build/trunk/libcpp/expr.c} or @file{/build/trunk/gcc/x-expr.c}.
7002 @item @var{function}
7003 Specifies the line that begins the body of the function @var{function}.
7004 For example, in C, this is the line with the open brace.
7006 @item @var{function}:@var{label}
7007 Specifies the line where @var{label} appears in @var{function}.
7009 @item @var{filename}:@var{function}
7010 Specifies the line that begins the body of the function @var{function}
7011 in the file @var{filename}. You only need the file name with a
7012 function name to avoid ambiguity when there are identically named
7013 functions in different source files.
7016 Specifies the line at which the label named @var{label} appears.
7017 @value{GDBN} searches for the label in the function corresponding to
7018 the currently selected stack frame. If there is no current selected
7019 stack frame (for instance, if the inferior is not running), then
7020 @value{GDBN} will not search for a label.
7022 @item *@var{address}
7023 Specifies the program address @var{address}. For line-oriented
7024 commands, such as @code{list} and @code{edit}, this specifies a source
7025 line that contains @var{address}. For @code{break} and other
7026 breakpoint oriented commands, this can be used to set breakpoints in
7027 parts of your program which do not have debugging information or
7030 Here @var{address} may be any expression valid in the current working
7031 language (@pxref{Languages, working language}) that specifies a code
7032 address. In addition, as a convenience, @value{GDBN} extends the
7033 semantics of expressions used in locations to cover the situations
7034 that frequently happen during debugging. Here are the various forms
7038 @item @var{expression}
7039 Any expression valid in the current working language.
7041 @item @var{funcaddr}
7042 An address of a function or procedure derived from its name. In C,
7043 C@t{++}, Java, Objective-C, Fortran, minimal, and assembly, this is
7044 simply the function's name @var{function} (and actually a special case
7045 of a valid expression). In Pascal and Modula-2, this is
7046 @code{&@var{function}}. In Ada, this is @code{@var{function}'Address}
7047 (although the Pascal form also works).
7049 This form specifies the address of the function's first instruction,
7050 before the stack frame and arguments have been set up.
7052 @item '@var{filename}'::@var{funcaddr}
7053 Like @var{funcaddr} above, but also specifies the name of the source
7054 file explicitly. This is useful if the name of the function does not
7055 specify the function unambiguously, e.g., if there are several
7056 functions with identical names in different source files.
7059 @cindex breakpoint at static probe point
7060 @item -pstap|-probe-stap @r{[}@var{objfile}:@r{[}@var{provider}:@r{]}@r{]}@var{name}
7061 The @sc{gnu}/Linux tool @code{SystemTap} provides a way for
7062 applications to embed static probes. @xref{Static Probe Points}, for more
7063 information on finding and using static probes. This form of linespec
7064 specifies the location of such a static probe.
7066 If @var{objfile} is given, only probes coming from that shared library
7067 or executable matching @var{objfile} as a regular expression are considered.
7068 If @var{provider} is given, then only probes from that provider are considered.
7069 If several probes match the spec, @value{GDBN} will insert a breakpoint at
7070 each one of those probes.
7076 @section Editing Source Files
7077 @cindex editing source files
7080 @kindex e @r{(@code{edit})}
7081 To edit the lines in a source file, use the @code{edit} command.
7082 The editing program of your choice
7083 is invoked with the current line set to
7084 the active line in the program.
7085 Alternatively, there are several ways to specify what part of the file you
7086 want to print if you want to see other parts of the program:
7089 @item edit @var{location}
7090 Edit the source file specified by @code{location}. Editing starts at
7091 that @var{location}, e.g., at the specified source line of the
7092 specified file. @xref{Specify Location}, for all the possible forms
7093 of the @var{location} argument; here are the forms of the @code{edit}
7094 command most commonly used:
7097 @item edit @var{number}
7098 Edit the current source file with @var{number} as the active line number.
7100 @item edit @var{function}
7101 Edit the file containing @var{function} at the beginning of its definition.
7106 @subsection Choosing your Editor
7107 You can customize @value{GDBN} to use any editor you want
7109 The only restriction is that your editor (say @code{ex}), recognizes the
7110 following command-line syntax:
7112 ex +@var{number} file
7114 The optional numeric value +@var{number} specifies the number of the line in
7115 the file where to start editing.}.
7116 By default, it is @file{@value{EDITOR}}, but you can change this
7117 by setting the environment variable @code{EDITOR} before using
7118 @value{GDBN}. For example, to configure @value{GDBN} to use the
7119 @code{vi} editor, you could use these commands with the @code{sh} shell:
7125 or in the @code{csh} shell,
7127 setenv EDITOR /usr/bin/vi
7132 @section Searching Source Files
7133 @cindex searching source files
7135 There are two commands for searching through the current source file for a
7140 @kindex forward-search
7141 @kindex fo @r{(@code{forward-search})}
7142 @item forward-search @var{regexp}
7143 @itemx search @var{regexp}
7144 The command @samp{forward-search @var{regexp}} checks each line,
7145 starting with the one following the last line listed, for a match for
7146 @var{regexp}. It lists the line that is found. You can use the
7147 synonym @samp{search @var{regexp}} or abbreviate the command name as
7150 @kindex reverse-search
7151 @item reverse-search @var{regexp}
7152 The command @samp{reverse-search @var{regexp}} checks each line, starting
7153 with the one before the last line listed and going backward, for a match
7154 for @var{regexp}. It lists the line that is found. You can abbreviate
7155 this command as @code{rev}.
7159 @section Specifying Source Directories
7162 @cindex directories for source files
7163 Executable programs sometimes do not record the directories of the source
7164 files from which they were compiled, just the names. Even when they do,
7165 the directories could be moved between the compilation and your debugging
7166 session. @value{GDBN} has a list of directories to search for source files;
7167 this is called the @dfn{source path}. Each time @value{GDBN} wants a source file,
7168 it tries all the directories in the list, in the order they are present
7169 in the list, until it finds a file with the desired name.
7171 For example, suppose an executable references the file
7172 @file{/usr/src/foo-1.0/lib/foo.c}, and our source path is
7173 @file{/mnt/cross}. The file is first looked up literally; if this
7174 fails, @file{/mnt/cross/usr/src/foo-1.0/lib/foo.c} is tried; if this
7175 fails, @file{/mnt/cross/foo.c} is opened; if this fails, an error
7176 message is printed. @value{GDBN} does not look up the parts of the
7177 source file name, such as @file{/mnt/cross/src/foo-1.0/lib/foo.c}.
7178 Likewise, the subdirectories of the source path are not searched: if
7179 the source path is @file{/mnt/cross}, and the binary refers to
7180 @file{foo.c}, @value{GDBN} would not find it under
7181 @file{/mnt/cross/usr/src/foo-1.0/lib}.
7183 Plain file names, relative file names with leading directories, file
7184 names containing dots, etc.@: are all treated as described above; for
7185 instance, if the source path is @file{/mnt/cross}, and the source file
7186 is recorded as @file{../lib/foo.c}, @value{GDBN} would first try
7187 @file{../lib/foo.c}, then @file{/mnt/cross/../lib/foo.c}, and after
7188 that---@file{/mnt/cross/foo.c}.
7190 Note that the executable search path is @emph{not} used to locate the
7193 Whenever you reset or rearrange the source path, @value{GDBN} clears out
7194 any information it has cached about where source files are found and where
7195 each line is in the file.
7199 When you start @value{GDBN}, its source path includes only @samp{cdir}
7200 and @samp{cwd}, in that order.
7201 To add other directories, use the @code{directory} command.
7203 The search path is used to find both program source files and @value{GDBN}
7204 script files (read using the @samp{-command} option and @samp{source} command).
7206 In addition to the source path, @value{GDBN} provides a set of commands
7207 that manage a list of source path substitution rules. A @dfn{substitution
7208 rule} specifies how to rewrite source directories stored in the program's
7209 debug information in case the sources were moved to a different
7210 directory between compilation and debugging. A rule is made of
7211 two strings, the first specifying what needs to be rewritten in
7212 the path, and the second specifying how it should be rewritten.
7213 In @ref{set substitute-path}, we name these two parts @var{from} and
7214 @var{to} respectively. @value{GDBN} does a simple string replacement
7215 of @var{from} with @var{to} at the start of the directory part of the
7216 source file name, and uses that result instead of the original file
7217 name to look up the sources.
7219 Using the previous example, suppose the @file{foo-1.0} tree has been
7220 moved from @file{/usr/src} to @file{/mnt/cross}, then you can tell
7221 @value{GDBN} to replace @file{/usr/src} in all source path names with
7222 @file{/mnt/cross}. The first lookup will then be
7223 @file{/mnt/cross/foo-1.0/lib/foo.c} in place of the original location
7224 of @file{/usr/src/foo-1.0/lib/foo.c}. To define a source path
7225 substitution rule, use the @code{set substitute-path} command
7226 (@pxref{set substitute-path}).
7228 To avoid unexpected substitution results, a rule is applied only if the
7229 @var{from} part of the directory name ends at a directory separator.
7230 For instance, a rule substituting @file{/usr/source} into
7231 @file{/mnt/cross} will be applied to @file{/usr/source/foo-1.0} but
7232 not to @file{/usr/sourceware/foo-2.0}. And because the substitution
7233 is applied only at the beginning of the directory name, this rule will
7234 not be applied to @file{/root/usr/source/baz.c} either.
7236 In many cases, you can achieve the same result using the @code{directory}
7237 command. However, @code{set substitute-path} can be more efficient in
7238 the case where the sources are organized in a complex tree with multiple
7239 subdirectories. With the @code{directory} command, you need to add each
7240 subdirectory of your project. If you moved the entire tree while
7241 preserving its internal organization, then @code{set substitute-path}
7242 allows you to direct the debugger to all the sources with one single
7245 @code{set substitute-path} is also more than just a shortcut command.
7246 The source path is only used if the file at the original location no
7247 longer exists. On the other hand, @code{set substitute-path} modifies
7248 the debugger behavior to look at the rewritten location instead. So, if
7249 for any reason a source file that is not relevant to your executable is
7250 located at the original location, a substitution rule is the only
7251 method available to point @value{GDBN} at the new location.
7253 @cindex @samp{--with-relocated-sources}
7254 @cindex default source path substitution
7255 You can configure a default source path substitution rule by
7256 configuring @value{GDBN} with the
7257 @samp{--with-relocated-sources=@var{dir}} option. The @var{dir}
7258 should be the name of a directory under @value{GDBN}'s configured
7259 prefix (set with @samp{--prefix} or @samp{--exec-prefix}), and
7260 directory names in debug information under @var{dir} will be adjusted
7261 automatically if the installed @value{GDBN} is moved to a new
7262 location. This is useful if @value{GDBN}, libraries or executables
7263 with debug information and corresponding source code are being moved
7267 @item directory @var{dirname} @dots{}
7268 @item dir @var{dirname} @dots{}
7269 Add directory @var{dirname} to the front of the source path. Several
7270 directory names may be given to this command, separated by @samp{:}
7271 (@samp{;} on MS-DOS and MS-Windows, where @samp{:} usually appears as
7272 part of absolute file names) or
7273 whitespace. You may specify a directory that is already in the source
7274 path; this moves it forward, so @value{GDBN} searches it sooner.
7278 @vindex $cdir@r{, convenience variable}
7279 @vindex $cwd@r{, convenience variable}
7280 @cindex compilation directory
7281 @cindex current directory
7282 @cindex working directory
7283 @cindex directory, current
7284 @cindex directory, compilation
7285 You can use the string @samp{$cdir} to refer to the compilation
7286 directory (if one is recorded), and @samp{$cwd} to refer to the current
7287 working directory. @samp{$cwd} is not the same as @samp{.}---the former
7288 tracks the current working directory as it changes during your @value{GDBN}
7289 session, while the latter is immediately expanded to the current
7290 directory at the time you add an entry to the source path.
7293 Reset the source path to its default value (@samp{$cdir:$cwd} on Unix systems). This requires confirmation.
7295 @c RET-repeat for @code{directory} is explicitly disabled, but since
7296 @c repeating it would be a no-op we do not say that. (thanks to RMS)
7298 @item set directories @var{path-list}
7299 @kindex set directories
7300 Set the source path to @var{path-list}.
7301 @samp{$cdir:$cwd} are added if missing.
7303 @item show directories
7304 @kindex show directories
7305 Print the source path: show which directories it contains.
7307 @anchor{set substitute-path}
7308 @item set substitute-path @var{from} @var{to}
7309 @kindex set substitute-path
7310 Define a source path substitution rule, and add it at the end of the
7311 current list of existing substitution rules. If a rule with the same
7312 @var{from} was already defined, then the old rule is also deleted.
7314 For example, if the file @file{/foo/bar/baz.c} was moved to
7315 @file{/mnt/cross/baz.c}, then the command
7318 (@value{GDBP}) set substitute-path /usr/src /mnt/cross
7322 will tell @value{GDBN} to replace @samp{/usr/src} with
7323 @samp{/mnt/cross}, which will allow @value{GDBN} to find the file
7324 @file{baz.c} even though it was moved.
7326 In the case when more than one substitution rule have been defined,
7327 the rules are evaluated one by one in the order where they have been
7328 defined. The first one matching, if any, is selected to perform
7331 For instance, if we had entered the following commands:
7334 (@value{GDBP}) set substitute-path /usr/src/include /mnt/include
7335 (@value{GDBP}) set substitute-path /usr/src /mnt/src
7339 @value{GDBN} would then rewrite @file{/usr/src/include/defs.h} into
7340 @file{/mnt/include/defs.h} by using the first rule. However, it would
7341 use the second rule to rewrite @file{/usr/src/lib/foo.c} into
7342 @file{/mnt/src/lib/foo.c}.
7345 @item unset substitute-path [path]
7346 @kindex unset substitute-path
7347 If a path is specified, search the current list of substitution rules
7348 for a rule that would rewrite that path. Delete that rule if found.
7349 A warning is emitted by the debugger if no rule could be found.
7351 If no path is specified, then all substitution rules are deleted.
7353 @item show substitute-path [path]
7354 @kindex show substitute-path
7355 If a path is specified, then print the source path substitution rule
7356 which would rewrite that path, if any.
7358 If no path is specified, then print all existing source path substitution
7363 If your source path is cluttered with directories that are no longer of
7364 interest, @value{GDBN} may sometimes cause confusion by finding the wrong
7365 versions of source. You can correct the situation as follows:
7369 Use @code{directory} with no argument to reset the source path to its default value.
7372 Use @code{directory} with suitable arguments to reinstall the
7373 directories you want in the source path. You can add all the
7374 directories in one command.
7378 @section Source and Machine Code
7379 @cindex source line and its code address
7381 You can use the command @code{info line} to map source lines to program
7382 addresses (and vice versa), and the command @code{disassemble} to display
7383 a range of addresses as machine instructions. You can use the command
7384 @code{set disassemble-next-line} to set whether to disassemble next
7385 source line when execution stops. When run under @sc{gnu} Emacs
7386 mode, the @code{info line} command causes the arrow to point to the
7387 line specified. Also, @code{info line} prints addresses in symbolic form as
7392 @item info line @var{linespec}
7393 Print the starting and ending addresses of the compiled code for
7394 source line @var{linespec}. You can specify source lines in any of
7395 the ways documented in @ref{Specify Location}.
7398 For example, we can use @code{info line} to discover the location of
7399 the object code for the first line of function
7400 @code{m4_changequote}:
7402 @c FIXME: I think this example should also show the addresses in
7403 @c symbolic form, as they usually would be displayed.
7405 (@value{GDBP}) info line m4_changequote
7406 Line 895 of "builtin.c" starts at pc 0x634c and ends at 0x6350.
7410 @cindex code address and its source line
7411 We can also inquire (using @code{*@var{addr}} as the form for
7412 @var{linespec}) what source line covers a particular address:
7414 (@value{GDBP}) info line *0x63ff
7415 Line 926 of "builtin.c" starts at pc 0x63e4 and ends at 0x6404.
7418 @cindex @code{$_} and @code{info line}
7419 @cindex @code{x} command, default address
7420 @kindex x@r{(examine), and} info line
7421 After @code{info line}, the default address for the @code{x} command
7422 is changed to the starting address of the line, so that @samp{x/i} is
7423 sufficient to begin examining the machine code (@pxref{Memory,
7424 ,Examining Memory}). Also, this address is saved as the value of the
7425 convenience variable @code{$_} (@pxref{Convenience Vars, ,Convenience
7430 @cindex assembly instructions
7431 @cindex instructions, assembly
7432 @cindex machine instructions
7433 @cindex listing machine instructions
7435 @itemx disassemble /m
7436 @itemx disassemble /r
7437 This specialized command dumps a range of memory as machine
7438 instructions. It can also print mixed source+disassembly by specifying
7439 the @code{/m} modifier and print the raw instructions in hex as well as
7440 in symbolic form by specifying the @code{/r}.
7441 The default memory range is the function surrounding the
7442 program counter of the selected frame. A single argument to this
7443 command is a program counter value; @value{GDBN} dumps the function
7444 surrounding this value. When two arguments are given, they should
7445 be separated by a comma, possibly surrounded by whitespace. The
7446 arguments specify a range of addresses to dump, in one of two forms:
7449 @item @var{start},@var{end}
7450 the addresses from @var{start} (inclusive) to @var{end} (exclusive)
7451 @item @var{start},+@var{length}
7452 the addresses from @var{start} (inclusive) to
7453 @code{@var{start}+@var{length}} (exclusive).
7457 When 2 arguments are specified, the name of the function is also
7458 printed (since there could be several functions in the given range).
7460 The argument(s) can be any expression yielding a numeric value, such as
7461 @samp{0x32c4}, @samp{&main+10} or @samp{$pc - 8}.
7463 If the range of memory being disassembled contains current program counter,
7464 the instruction at that location is shown with a @code{=>} marker.
7467 The following example shows the disassembly of a range of addresses of
7468 HP PA-RISC 2.0 code:
7471 (@value{GDBP}) disas 0x32c4, 0x32e4
7472 Dump of assembler code from 0x32c4 to 0x32e4:
7473 0x32c4 <main+204>: addil 0,dp
7474 0x32c8 <main+208>: ldw 0x22c(sr0,r1),r26
7475 0x32cc <main+212>: ldil 0x3000,r31
7476 0x32d0 <main+216>: ble 0x3f8(sr4,r31)
7477 0x32d4 <main+220>: ldo 0(r31),rp
7478 0x32d8 <main+224>: addil -0x800,dp
7479 0x32dc <main+228>: ldo 0x588(r1),r26
7480 0x32e0 <main+232>: ldil 0x3000,r31
7481 End of assembler dump.
7484 Here is an example showing mixed source+assembly for Intel x86, when the
7485 program is stopped just after function prologue:
7488 (@value{GDBP}) disas /m main
7489 Dump of assembler code for function main:
7491 0x08048330 <+0>: push %ebp
7492 0x08048331 <+1>: mov %esp,%ebp
7493 0x08048333 <+3>: sub $0x8,%esp
7494 0x08048336 <+6>: and $0xfffffff0,%esp
7495 0x08048339 <+9>: sub $0x10,%esp
7497 6 printf ("Hello.\n");
7498 => 0x0804833c <+12>: movl $0x8048440,(%esp)
7499 0x08048343 <+19>: call 0x8048284 <puts@@plt>
7503 0x08048348 <+24>: mov $0x0,%eax
7504 0x0804834d <+29>: leave
7505 0x0804834e <+30>: ret
7507 End of assembler dump.
7510 Here is another example showing raw instructions in hex for AMD x86-64,
7513 (gdb) disas /r 0x400281,+10
7514 Dump of assembler code from 0x400281 to 0x40028b:
7515 0x0000000000400281: 38 36 cmp %dh,(%rsi)
7516 0x0000000000400283: 2d 36 34 2e 73 sub $0x732e3436,%eax
7517 0x0000000000400288: 6f outsl %ds:(%rsi),(%dx)
7518 0x0000000000400289: 2e 32 00 xor %cs:(%rax),%al
7519 End of assembler dump.
7522 Addresses cannot be specified as a linespec (@pxref{Specify Location}).
7523 So, for example, if you want to disassemble function @code{bar}
7524 in file @file{foo.c}, you must type @samp{disassemble 'foo.c'::bar}
7525 and not @samp{disassemble foo.c:bar}.
7527 Some architectures have more than one commonly-used set of instruction
7528 mnemonics or other syntax.
7530 For programs that were dynamically linked and use shared libraries,
7531 instructions that call functions or branch to locations in the shared
7532 libraries might show a seemingly bogus location---it's actually a
7533 location of the relocation table. On some architectures, @value{GDBN}
7534 might be able to resolve these to actual function names.
7537 @kindex set disassembly-flavor
7538 @cindex Intel disassembly flavor
7539 @cindex AT&T disassembly flavor
7540 @item set disassembly-flavor @var{instruction-set}
7541 Select the instruction set to use when disassembling the
7542 program via the @code{disassemble} or @code{x/i} commands.
7544 Currently this command is only defined for the Intel x86 family. You
7545 can set @var{instruction-set} to either @code{intel} or @code{att}.
7546 The default is @code{att}, the AT&T flavor used by default by Unix
7547 assemblers for x86-based targets.
7549 @kindex show disassembly-flavor
7550 @item show disassembly-flavor
7551 Show the current setting of the disassembly flavor.
7555 @kindex set disassemble-next-line
7556 @kindex show disassemble-next-line
7557 @item set disassemble-next-line
7558 @itemx show disassemble-next-line
7559 Control whether or not @value{GDBN} will disassemble the next source
7560 line or instruction when execution stops. If ON, @value{GDBN} will
7561 display disassembly of the next source line when execution of the
7562 program being debugged stops. This is @emph{in addition} to
7563 displaying the source line itself, which @value{GDBN} always does if
7564 possible. If the next source line cannot be displayed for some reason
7565 (e.g., if @value{GDBN} cannot find the source file, or there's no line
7566 info in the debug info), @value{GDBN} will display disassembly of the
7567 next @emph{instruction} instead of showing the next source line. If
7568 AUTO, @value{GDBN} will display disassembly of next instruction only
7569 if the source line cannot be displayed. This setting causes
7570 @value{GDBN} to display some feedback when you step through a function
7571 with no line info or whose source file is unavailable. The default is
7572 OFF, which means never display the disassembly of the next line or
7578 @chapter Examining Data
7580 @cindex printing data
7581 @cindex examining data
7584 The usual way to examine data in your program is with the @code{print}
7585 command (abbreviated @code{p}), or its synonym @code{inspect}. It
7586 evaluates and prints the value of an expression of the language your
7587 program is written in (@pxref{Languages, ,Using @value{GDBN} with
7588 Different Languages}). It may also print the expression using a
7589 Python-based pretty-printer (@pxref{Pretty Printing}).
7592 @item print @var{expr}
7593 @itemx print /@var{f} @var{expr}
7594 @var{expr} is an expression (in the source language). By default the
7595 value of @var{expr} is printed in a format appropriate to its data type;
7596 you can choose a different format by specifying @samp{/@var{f}}, where
7597 @var{f} is a letter specifying the format; see @ref{Output Formats,,Output
7601 @itemx print /@var{f}
7602 @cindex reprint the last value
7603 If you omit @var{expr}, @value{GDBN} displays the last value again (from the
7604 @dfn{value history}; @pxref{Value History, ,Value History}). This allows you to
7605 conveniently inspect the same value in an alternative format.
7608 A more low-level way of examining data is with the @code{x} command.
7609 It examines data in memory at a specified address and prints it in a
7610 specified format. @xref{Memory, ,Examining Memory}.
7612 If you are interested in information about types, or about how the
7613 fields of a struct or a class are declared, use the @code{ptype @var{exp}}
7614 command rather than @code{print}. @xref{Symbols, ,Examining the Symbol
7617 @cindex exploring hierarchical data structures
7619 Another way of examining values of expressions and type information is
7620 through the Python extension command @code{explore} (available only if
7621 the @value{GDBN} build is configured with @code{--with-python}). It
7622 offers an interactive way to start at the highest level (or, the most
7623 abstract level) of the data type of an expression (or, the data type
7624 itself) and explore all the way down to leaf scalar values/fields
7625 embedded in the higher level data types.
7628 @item explore @var{arg}
7629 @var{arg} is either an expression (in the source language), or a type
7630 visible in the current context of the program being debugged.
7633 The working of the @code{explore} command can be illustrated with an
7634 example. If a data type @code{struct ComplexStruct} is defined in your
7644 struct ComplexStruct
7646 struct SimpleStruct *ss_p;
7652 followed by variable declarations as
7655 struct SimpleStruct ss = @{ 10, 1.11 @};
7656 struct ComplexStruct cs = @{ &ss, @{ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 @} @};
7660 then, the value of the variable @code{cs} can be explored using the
7661 @code{explore} command as follows.
7665 The value of `cs' is a struct/class of type `struct ComplexStruct' with
7666 the following fields:
7668 ss_p = <Enter 0 to explore this field of type `struct SimpleStruct *'>
7669 arr = <Enter 1 to explore this field of type `int [10]'>
7671 Enter the field number of choice:
7675 Since the fields of @code{cs} are not scalar values, you are being
7676 prompted to chose the field you want to explore. Let's say you choose
7677 the field @code{ss_p} by entering @code{0}. Then, since this field is a
7678 pointer, you will be asked if it is pointing to a single value. From
7679 the declaration of @code{cs} above, it is indeed pointing to a single
7680 value, hence you enter @code{y}. If you enter @code{n}, then you will
7681 be asked if it were pointing to an array of values, in which case this
7682 field will be explored as if it were an array.
7685 `cs.ss_p' is a pointer to a value of type `struct SimpleStruct'
7686 Continue exploring it as a pointer to a single value [y/n]: y
7687 The value of `*(cs.ss_p)' is a struct/class of type `struct
7688 SimpleStruct' with the following fields:
7690 i = 10 .. (Value of type `int')
7691 d = 1.1100000000000001 .. (Value of type `double')
7693 Press enter to return to parent value:
7697 If the field @code{arr} of @code{cs} was chosen for exploration by
7698 entering @code{1} earlier, then since it is as array, you will be
7699 prompted to enter the index of the element in the array that you want
7703 `cs.arr' is an array of `int'.
7704 Enter the index of the element you want to explore in `cs.arr': 5
7706 `(cs.arr)[5]' is a scalar value of type `int'.
7710 Press enter to return to parent value:
7713 In general, at any stage of exploration, you can go deeper towards the
7714 leaf values by responding to the prompts appropriately, or hit the
7715 return key to return to the enclosing data structure (the @i{higher}
7716 level data structure).
7718 Similar to exploring values, you can use the @code{explore} command to
7719 explore types. Instead of specifying a value (which is typically a
7720 variable name or an expression valid in the current context of the
7721 program being debugged), you specify a type name. If you consider the
7722 same example as above, your can explore the type
7723 @code{struct ComplexStruct} by passing the argument
7724 @code{struct ComplexStruct} to the @code{explore} command.
7727 (gdb) explore struct ComplexStruct
7731 By responding to the prompts appropriately in the subsequent interactive
7732 session, you can explore the type @code{struct ComplexStruct} in a
7733 manner similar to how the value @code{cs} was explored in the above
7736 The @code{explore} command also has two sub-commands,
7737 @code{explore value} and @code{explore type}. The former sub-command is
7738 a way to explicitly specify that value exploration of the argument is
7739 being invoked, while the latter is a way to explicitly specify that type
7740 exploration of the argument is being invoked.
7743 @item explore value @var{expr}
7744 @cindex explore value
7745 This sub-command of @code{explore} explores the value of the
7746 expression @var{expr} (if @var{expr} is an expression valid in the
7747 current context of the program being debugged). The behavior of this
7748 command is identical to that of the behavior of the @code{explore}
7749 command being passed the argument @var{expr}.
7751 @item explore type @var{arg}
7752 @cindex explore type
7753 This sub-command of @code{explore} explores the type of @var{arg} (if
7754 @var{arg} is a type visible in the current context of program being
7755 debugged), or the type of the value/expression @var{arg} (if @var{arg}
7756 is an expression valid in the current context of the program being
7757 debugged). If @var{arg} is a type, then the behavior of this command is
7758 identical to that of the @code{explore} command being passed the
7759 argument @var{arg}. If @var{arg} is an expression, then the behavior of
7760 this command will be identical to that of the @code{explore} command
7761 being passed the type of @var{arg} as the argument.
7765 * Expressions:: Expressions
7766 * Ambiguous Expressions:: Ambiguous Expressions
7767 * Variables:: Program variables
7768 * Arrays:: Artificial arrays
7769 * Output Formats:: Output formats
7770 * Memory:: Examining memory
7771 * Auto Display:: Automatic display
7772 * Print Settings:: Print settings
7773 * Pretty Printing:: Python pretty printing
7774 * Value History:: Value history
7775 * Convenience Vars:: Convenience variables
7776 * Convenience Funs:: Convenience functions
7777 * Registers:: Registers
7778 * Floating Point Hardware:: Floating point hardware
7779 * Vector Unit:: Vector Unit
7780 * OS Information:: Auxiliary data provided by operating system
7781 * Memory Region Attributes:: Memory region attributes
7782 * Dump/Restore Files:: Copy between memory and a file
7783 * Core File Generation:: Cause a program dump its core
7784 * Character Sets:: Debugging programs that use a different
7785 character set than GDB does
7786 * Caching Remote Data:: Data caching for remote targets
7787 * Searching Memory:: Searching memory for a sequence of bytes
7791 @section Expressions
7794 @code{print} and many other @value{GDBN} commands accept an expression and
7795 compute its value. Any kind of constant, variable or operator defined
7796 by the programming language you are using is valid in an expression in
7797 @value{GDBN}. This includes conditional expressions, function calls,
7798 casts, and string constants. It also includes preprocessor macros, if
7799 you compiled your program to include this information; see
7802 @cindex arrays in expressions
7803 @value{GDBN} supports array constants in expressions input by
7804 the user. The syntax is @{@var{element}, @var{element}@dots{}@}. For example,
7805 you can use the command @code{print @{1, 2, 3@}} to create an array
7806 of three integers. If you pass an array to a function or assign it
7807 to a program variable, @value{GDBN} copies the array to memory that
7808 is @code{malloc}ed in the target program.
7810 Because C is so widespread, most of the expressions shown in examples in
7811 this manual are in C. @xref{Languages, , Using @value{GDBN} with Different
7812 Languages}, for information on how to use expressions in other
7815 In this section, we discuss operators that you can use in @value{GDBN}
7816 expressions regardless of your programming language.
7818 @cindex casts, in expressions
7819 Casts are supported in all languages, not just in C, because it is so
7820 useful to cast a number into a pointer in order to examine a structure
7821 at that address in memory.
7822 @c FIXME: casts supported---Mod2 true?
7824 @value{GDBN} supports these operators, in addition to those common
7825 to programming languages:
7829 @samp{@@} is a binary operator for treating parts of memory as arrays.
7830 @xref{Arrays, ,Artificial Arrays}, for more information.
7833 @samp{::} allows you to specify a variable in terms of the file or
7834 function where it is defined. @xref{Variables, ,Program Variables}.
7836 @cindex @{@var{type}@}
7837 @cindex type casting memory
7838 @cindex memory, viewing as typed object
7839 @cindex casts, to view memory
7840 @item @{@var{type}@} @var{addr}
7841 Refers to an object of type @var{type} stored at address @var{addr} in
7842 memory. @var{addr} may be any expression whose value is an integer or
7843 pointer (but parentheses are required around binary operators, just as in
7844 a cast). This construct is allowed regardless of what kind of data is
7845 normally supposed to reside at @var{addr}.
7848 @node Ambiguous Expressions
7849 @section Ambiguous Expressions
7850 @cindex ambiguous expressions
7852 Expressions can sometimes contain some ambiguous elements. For instance,
7853 some programming languages (notably Ada, C@t{++} and Objective-C) permit
7854 a single function name to be defined several times, for application in
7855 different contexts. This is called @dfn{overloading}. Another example
7856 involving Ada is generics. A @dfn{generic package} is similar to C@t{++}
7857 templates and is typically instantiated several times, resulting in
7858 the same function name being defined in different contexts.
7860 In some cases and depending on the language, it is possible to adjust
7861 the expression to remove the ambiguity. For instance in C@t{++}, you
7862 can specify the signature of the function you want to break on, as in
7863 @kbd{break @var{function}(@var{types})}. In Ada, using the fully
7864 qualified name of your function often makes the expression unambiguous
7867 When an ambiguity that needs to be resolved is detected, the debugger
7868 has the capability to display a menu of numbered choices for each
7869 possibility, and then waits for the selection with the prompt @samp{>}.
7870 The first option is always @samp{[0] cancel}, and typing @kbd{0 @key{RET}}
7871 aborts the current command. If the command in which the expression was
7872 used allows more than one choice to be selected, the next option in the
7873 menu is @samp{[1] all}, and typing @kbd{1 @key{RET}} selects all possible
7876 For example, the following session excerpt shows an attempt to set a
7877 breakpoint at the overloaded symbol @code{String::after}.
7878 We choose three particular definitions of that function name:
7880 @c FIXME! This is likely to change to show arg type lists, at least
7883 (@value{GDBP}) b String::after
7886 [2] file:String.cc; line number:867
7887 [3] file:String.cc; line number:860
7888 [4] file:String.cc; line number:875
7889 [5] file:String.cc; line number:853
7890 [6] file:String.cc; line number:846
7891 [7] file:String.cc; line number:735
7893 Breakpoint 1 at 0xb26c: file String.cc, line 867.
7894 Breakpoint 2 at 0xb344: file String.cc, line 875.
7895 Breakpoint 3 at 0xafcc: file String.cc, line 846.
7896 Multiple breakpoints were set.
7897 Use the "delete" command to delete unwanted
7904 @kindex set multiple-symbols
7905 @item set multiple-symbols @var{mode}
7906 @cindex multiple-symbols menu
7908 This option allows you to adjust the debugger behavior when an expression
7911 By default, @var{mode} is set to @code{all}. If the command with which
7912 the expression is used allows more than one choice, then @value{GDBN}
7913 automatically selects all possible choices. For instance, inserting
7914 a breakpoint on a function using an ambiguous name results in a breakpoint
7915 inserted on each possible match. However, if a unique choice must be made,
7916 then @value{GDBN} uses the menu to help you disambiguate the expression.
7917 For instance, printing the address of an overloaded function will result
7918 in the use of the menu.
7920 When @var{mode} is set to @code{ask}, the debugger always uses the menu
7921 when an ambiguity is detected.
7923 Finally, when @var{mode} is set to @code{cancel}, the debugger reports
7924 an error due to the ambiguity and the command is aborted.
7926 @kindex show multiple-symbols
7927 @item show multiple-symbols
7928 Show the current value of the @code{multiple-symbols} setting.
7932 @section Program Variables
7934 The most common kind of expression to use is the name of a variable
7937 Variables in expressions are understood in the selected stack frame
7938 (@pxref{Selection, ,Selecting a Frame}); they must be either:
7942 global (or file-static)
7949 visible according to the scope rules of the
7950 programming language from the point of execution in that frame
7953 @noindent This means that in the function
7968 you can examine and use the variable @code{a} whenever your program is
7969 executing within the function @code{foo}, but you can only use or
7970 examine the variable @code{b} while your program is executing inside
7971 the block where @code{b} is declared.
7973 @cindex variable name conflict
7974 There is an exception: you can refer to a variable or function whose
7975 scope is a single source file even if the current execution point is not
7976 in this file. But it is possible to have more than one such variable or
7977 function with the same name (in different source files). If that
7978 happens, referring to that name has unpredictable effects. If you wish,
7979 you can specify a static variable in a particular function or file by
7980 using the colon-colon (@code{::}) notation:
7982 @cindex colon-colon, context for variables/functions
7984 @c info cannot cope with a :: index entry, but why deprive hard copy readers?
7985 @cindex @code{::}, context for variables/functions
7988 @var{file}::@var{variable}
7989 @var{function}::@var{variable}
7993 Here @var{file} or @var{function} is the name of the context for the
7994 static @var{variable}. In the case of file names, you can use quotes to
7995 make sure @value{GDBN} parses the file name as a single word---for example,
7996 to print a global value of @code{x} defined in @file{f2.c}:
7999 (@value{GDBP}) p 'f2.c'::x
8002 The @code{::} notation is normally used for referring to
8003 static variables, since you typically disambiguate uses of local variables
8004 in functions by selecting the appropriate frame and using the
8005 simple name of the variable. However, you may also use this notation
8006 to refer to local variables in frames enclosing the selected frame:
8015 process (a); /* Stop here */
8026 For example, if there is a breakpoint at the commented line,
8027 here is what you might see
8028 when the program stops after executing the call @code{bar(0)}:
8033 (@value{GDBP}) p bar::a
8036 #2 0x080483d0 in foo (a=5) at foobar.c:12
8039 (@value{GDBP}) p bar::a
8043 @cindex C@t{++} scope resolution
8044 These uses of @samp{::} are very rarely in conflict with the very similar
8045 use of the same notation in C@t{++}. @value{GDBN} also supports use of the C@t{++}
8046 scope resolution operator in @value{GDBN} expressions.
8047 @c FIXME: Um, so what happens in one of those rare cases where it's in
8050 @cindex wrong values
8051 @cindex variable values, wrong
8052 @cindex function entry/exit, wrong values of variables
8053 @cindex optimized code, wrong values of variables
8055 @emph{Warning:} Occasionally, a local variable may appear to have the
8056 wrong value at certain points in a function---just after entry to a new
8057 scope, and just before exit.
8059 You may see this problem when you are stepping by machine instructions.
8060 This is because, on most machines, it takes more than one instruction to
8061 set up a stack frame (including local variable definitions); if you are
8062 stepping by machine instructions, variables may appear to have the wrong
8063 values until the stack frame is completely built. On exit, it usually
8064 also takes more than one machine instruction to destroy a stack frame;
8065 after you begin stepping through that group of instructions, local
8066 variable definitions may be gone.
8068 This may also happen when the compiler does significant optimizations.
8069 To be sure of always seeing accurate values, turn off all optimization
8072 @cindex ``No symbol "foo" in current context''
8073 Another possible effect of compiler optimizations is to optimize
8074 unused variables out of existence, or assign variables to registers (as
8075 opposed to memory addresses). Depending on the support for such cases
8076 offered by the debug info format used by the compiler, @value{GDBN}
8077 might not be able to display values for such local variables. If that
8078 happens, @value{GDBN} will print a message like this:
8081 No symbol "foo" in current context.
8084 To solve such problems, either recompile without optimizations, or use a
8085 different debug info format, if the compiler supports several such
8086 formats. @xref{Compilation}, for more information on choosing compiler
8087 options. @xref{C, ,C and C@t{++}}, for more information about debug
8088 info formats that are best suited to C@t{++} programs.
8090 If you ask to print an object whose contents are unknown to
8091 @value{GDBN}, e.g., because its data type is not completely specified
8092 by the debug information, @value{GDBN} will say @samp{<incomplete
8093 type>}. @xref{Symbols, incomplete type}, for more about this.
8095 If you append @kbd{@@entry} string to a function parameter name you get its
8096 value at the time the function got called. If the value is not available an
8097 error message is printed. Entry values are available only with some compilers.
8098 Entry values are normally also printed at the function parameter list according
8099 to @ref{set print entry-values}.
8102 Breakpoint 1, d (i=30) at gdb.base/entry-value.c:29
8108 (gdb) print i@@entry
8112 Strings are identified as arrays of @code{char} values without specified
8113 signedness. Arrays of either @code{signed char} or @code{unsigned char} get
8114 printed as arrays of 1 byte sized integers. @code{-fsigned-char} or
8115 @code{-funsigned-char} @value{NGCC} options have no effect as @value{GDBN}
8116 defines literal string type @code{"char"} as @code{char} without a sign.
8121 signed char var1[] = "A";
8124 You get during debugging
8129 $2 = @{65 'A', 0 '\0'@}
8133 @section Artificial Arrays
8135 @cindex artificial array
8137 @kindex @@@r{, referencing memory as an array}
8138 It is often useful to print out several successive objects of the
8139 same type in memory; a section of an array, or an array of
8140 dynamically determined size for which only a pointer exists in the
8143 You can do this by referring to a contiguous span of memory as an
8144 @dfn{artificial array}, using the binary operator @samp{@@}. The left
8145 operand of @samp{@@} should be the first element of the desired array
8146 and be an individual object. The right operand should be the desired length
8147 of the array. The result is an array value whose elements are all of
8148 the type of the left argument. The first element is actually the left
8149 argument; the second element comes from bytes of memory immediately
8150 following those that hold the first element, and so on. Here is an
8151 example. If a program says
8154 int *array = (int *) malloc (len * sizeof (int));
8158 you can print the contents of @code{array} with
8164 The left operand of @samp{@@} must reside in memory. Array values made
8165 with @samp{@@} in this way behave just like other arrays in terms of
8166 subscripting, and are coerced to pointers when used in expressions.
8167 Artificial arrays most often appear in expressions via the value history
8168 (@pxref{Value History, ,Value History}), after printing one out.
8170 Another way to create an artificial array is to use a cast.
8171 This re-interprets a value as if it were an array.
8172 The value need not be in memory:
8174 (@value{GDBP}) p/x (short[2])0x12345678
8175 $1 = @{0x1234, 0x5678@}
8178 As a convenience, if you leave the array length out (as in
8179 @samp{(@var{type}[])@var{value}}) @value{GDBN} calculates the size to fill
8180 the value (as @samp{sizeof(@var{value})/sizeof(@var{type})}:
8182 (@value{GDBP}) p/x (short[])0x12345678
8183 $2 = @{0x1234, 0x5678@}
8186 Sometimes the artificial array mechanism is not quite enough; in
8187 moderately complex data structures, the elements of interest may not
8188 actually be adjacent---for example, if you are interested in the values
8189 of pointers in an array. One useful work-around in this situation is
8190 to use a convenience variable (@pxref{Convenience Vars, ,Convenience
8191 Variables}) as a counter in an expression that prints the first
8192 interesting value, and then repeat that expression via @key{RET}. For
8193 instance, suppose you have an array @code{dtab} of pointers to
8194 structures, and you are interested in the values of a field @code{fv}
8195 in each structure. Here is an example of what you might type:
8205 @node Output Formats
8206 @section Output Formats
8208 @cindex formatted output
8209 @cindex output formats
8210 By default, @value{GDBN} prints a value according to its data type. Sometimes
8211 this is not what you want. For example, you might want to print a number
8212 in hex, or a pointer in decimal. Or you might want to view data in memory
8213 at a certain address as a character string or as an instruction. To do
8214 these things, specify an @dfn{output format} when you print a value.
8216 The simplest use of output formats is to say how to print a value
8217 already computed. This is done by starting the arguments of the
8218 @code{print} command with a slash and a format letter. The format
8219 letters supported are:
8223 Regard the bits of the value as an integer, and print the integer in
8227 Print as integer in signed decimal.
8230 Print as integer in unsigned decimal.
8233 Print as integer in octal.
8236 Print as integer in binary. The letter @samp{t} stands for ``two''.
8237 @footnote{@samp{b} cannot be used because these format letters are also
8238 used with the @code{x} command, where @samp{b} stands for ``byte'';
8239 see @ref{Memory,,Examining Memory}.}
8242 @cindex unknown address, locating
8243 @cindex locate address
8244 Print as an address, both absolute in hexadecimal and as an offset from
8245 the nearest preceding symbol. You can use this format used to discover
8246 where (in what function) an unknown address is located:
8249 (@value{GDBP}) p/a 0x54320
8250 $3 = 0x54320 <_initialize_vx+396>
8254 The command @code{info symbol 0x54320} yields similar results.
8255 @xref{Symbols, info symbol}.
8258 Regard as an integer and print it as a character constant. This
8259 prints both the numerical value and its character representation. The
8260 character representation is replaced with the octal escape @samp{\nnn}
8261 for characters outside the 7-bit @sc{ascii} range.
8263 Without this format, @value{GDBN} displays @code{char},
8264 @w{@code{unsigned char}}, and @w{@code{signed char}} data as character
8265 constants. Single-byte members of vectors are displayed as integer
8269 Regard the bits of the value as a floating point number and print
8270 using typical floating point syntax.
8273 @cindex printing strings
8274 @cindex printing byte arrays
8275 Regard as a string, if possible. With this format, pointers to single-byte
8276 data are displayed as null-terminated strings and arrays of single-byte data
8277 are displayed as fixed-length strings. Other values are displayed in their
8280 Without this format, @value{GDBN} displays pointers to and arrays of
8281 @code{char}, @w{@code{unsigned char}}, and @w{@code{signed char}} as
8282 strings. Single-byte members of a vector are displayed as an integer
8286 @cindex raw printing
8287 Print using the @samp{raw} formatting. By default, @value{GDBN} will
8288 use a Python-based pretty-printer, if one is available (@pxref{Pretty
8289 Printing}). This typically results in a higher-level display of the
8290 value's contents. The @samp{r} format bypasses any Python
8291 pretty-printer which might exist.
8294 For example, to print the program counter in hex (@pxref{Registers}), type
8301 Note that no space is required before the slash; this is because command
8302 names in @value{GDBN} cannot contain a slash.
8304 To reprint the last value in the value history with a different format,
8305 you can use the @code{print} command with just a format and no
8306 expression. For example, @samp{p/x} reprints the last value in hex.
8309 @section Examining Memory
8311 You can use the command @code{x} (for ``examine'') to examine memory in
8312 any of several formats, independently of your program's data types.
8314 @cindex examining memory
8316 @kindex x @r{(examine memory)}
8317 @item x/@var{nfu} @var{addr}
8320 Use the @code{x} command to examine memory.
8323 @var{n}, @var{f}, and @var{u} are all optional parameters that specify how
8324 much memory to display and how to format it; @var{addr} is an
8325 expression giving the address where you want to start displaying memory.
8326 If you use defaults for @var{nfu}, you need not type the slash @samp{/}.
8327 Several commands set convenient defaults for @var{addr}.
8330 @item @var{n}, the repeat count
8331 The repeat count is a decimal integer; the default is 1. It specifies
8332 how much memory (counting by units @var{u}) to display.
8333 @c This really is **decimal**; unaffected by 'set radix' as of GDB
8336 @item @var{f}, the display format
8337 The display format is one of the formats used by @code{print}
8338 (@samp{x}, @samp{d}, @samp{u}, @samp{o}, @samp{t}, @samp{a}, @samp{c},
8339 @samp{f}, @samp{s}), and in addition @samp{i} (for machine instructions).
8340 The default is @samp{x} (hexadecimal) initially. The default changes
8341 each time you use either @code{x} or @code{print}.
8343 @item @var{u}, the unit size
8344 The unit size is any of
8350 Halfwords (two bytes).
8352 Words (four bytes). This is the initial default.
8354 Giant words (eight bytes).
8357 Each time you specify a unit size with @code{x}, that size becomes the
8358 default unit the next time you use @code{x}. For the @samp{i} format,
8359 the unit size is ignored and is normally not written. For the @samp{s} format,
8360 the unit size defaults to @samp{b}, unless it is explicitly given.
8361 Use @kbd{x /hs} to display 16-bit char strings and @kbd{x /ws} to display
8362 32-bit strings. The next use of @kbd{x /s} will again display 8-bit strings.
8363 Note that the results depend on the programming language of the
8364 current compilation unit. If the language is C, the @samp{s}
8365 modifier will use the UTF-16 encoding while @samp{w} will use
8366 UTF-32. The encoding is set by the programming language and cannot
8369 @item @var{addr}, starting display address
8370 @var{addr} is the address where you want @value{GDBN} to begin displaying
8371 memory. The expression need not have a pointer value (though it may);
8372 it is always interpreted as an integer address of a byte of memory.
8373 @xref{Expressions, ,Expressions}, for more information on expressions. The default for
8374 @var{addr} is usually just after the last address examined---but several
8375 other commands also set the default address: @code{info breakpoints} (to
8376 the address of the last breakpoint listed), @code{info line} (to the
8377 starting address of a line), and @code{print} (if you use it to display
8378 a value from memory).
8381 For example, @samp{x/3uh 0x54320} is a request to display three halfwords
8382 (@code{h}) of memory, formatted as unsigned decimal integers (@samp{u}),
8383 starting at address @code{0x54320}. @samp{x/4xw $sp} prints the four
8384 words (@samp{w}) of memory above the stack pointer (here, @samp{$sp};
8385 @pxref{Registers, ,Registers}) in hexadecimal (@samp{x}).
8387 Since the letters indicating unit sizes are all distinct from the
8388 letters specifying output formats, you do not have to remember whether
8389 unit size or format comes first; either order works. The output
8390 specifications @samp{4xw} and @samp{4wx} mean exactly the same thing.
8391 (However, the count @var{n} must come first; @samp{wx4} does not work.)
8393 Even though the unit size @var{u} is ignored for the formats @samp{s}
8394 and @samp{i}, you might still want to use a count @var{n}; for example,
8395 @samp{3i} specifies that you want to see three machine instructions,
8396 including any operands. For convenience, especially when used with
8397 the @code{display} command, the @samp{i} format also prints branch delay
8398 slot instructions, if any, beyond the count specified, which immediately
8399 follow the last instruction that is within the count. The command
8400 @code{disassemble} gives an alternative way of inspecting machine
8401 instructions; see @ref{Machine Code,,Source and Machine Code}.
8403 All the defaults for the arguments to @code{x} are designed to make it
8404 easy to continue scanning memory with minimal specifications each time
8405 you use @code{x}. For example, after you have inspected three machine
8406 instructions with @samp{x/3i @var{addr}}, you can inspect the next seven
8407 with just @samp{x/7}. If you use @key{RET} to repeat the @code{x} command,
8408 the repeat count @var{n} is used again; the other arguments default as
8409 for successive uses of @code{x}.
8411 When examining machine instructions, the instruction at current program
8412 counter is shown with a @code{=>} marker. For example:
8415 (@value{GDBP}) x/5i $pc-6
8416 0x804837f <main+11>: mov %esp,%ebp
8417 0x8048381 <main+13>: push %ecx
8418 0x8048382 <main+14>: sub $0x4,%esp
8419 => 0x8048385 <main+17>: movl $0x8048460,(%esp)
8420 0x804838c <main+24>: call 0x80482d4 <puts@@plt>
8423 @cindex @code{$_}, @code{$__}, and value history
8424 The addresses and contents printed by the @code{x} command are not saved
8425 in the value history because there is often too much of them and they
8426 would get in the way. Instead, @value{GDBN} makes these values available for
8427 subsequent use in expressions as values of the convenience variables
8428 @code{$_} and @code{$__}. After an @code{x} command, the last address
8429 examined is available for use in expressions in the convenience variable
8430 @code{$_}. The contents of that address, as examined, are available in
8431 the convenience variable @code{$__}.
8433 If the @code{x} command has a repeat count, the address and contents saved
8434 are from the last memory unit printed; this is not the same as the last
8435 address printed if several units were printed on the last line of output.
8437 @cindex remote memory comparison
8438 @cindex verify remote memory image
8439 When you are debugging a program running on a remote target machine
8440 (@pxref{Remote Debugging}), you may wish to verify the program's image in the
8441 remote machine's memory against the executable file you downloaded to
8442 the target. The @code{compare-sections} command is provided for such
8446 @kindex compare-sections
8447 @item compare-sections @r{[}@var{section-name}@r{]}
8448 Compare the data of a loadable section @var{section-name} in the
8449 executable file of the program being debugged with the same section in
8450 the remote machine's memory, and report any mismatches. With no
8451 arguments, compares all loadable sections. This command's
8452 availability depends on the target's support for the @code{"qCRC"}
8457 @section Automatic Display
8458 @cindex automatic display
8459 @cindex display of expressions
8461 If you find that you want to print the value of an expression frequently
8462 (to see how it changes), you might want to add it to the @dfn{automatic
8463 display list} so that @value{GDBN} prints its value each time your program stops.
8464 Each expression added to the list is given a number to identify it;
8465 to remove an expression from the list, you specify that number.
8466 The automatic display looks like this:
8470 3: bar[5] = (struct hack *) 0x3804
8474 This display shows item numbers, expressions and their current values. As with
8475 displays you request manually using @code{x} or @code{print}, you can
8476 specify the output format you prefer; in fact, @code{display} decides
8477 whether to use @code{print} or @code{x} depending your format
8478 specification---it uses @code{x} if you specify either the @samp{i}
8479 or @samp{s} format, or a unit size; otherwise it uses @code{print}.
8483 @item display @var{expr}
8484 Add the expression @var{expr} to the list of expressions to display
8485 each time your program stops. @xref{Expressions, ,Expressions}.
8487 @code{display} does not repeat if you press @key{RET} again after using it.
8489 @item display/@var{fmt} @var{expr}
8490 For @var{fmt} specifying only a display format and not a size or
8491 count, add the expression @var{expr} to the auto-display list but
8492 arrange to display it each time in the specified format @var{fmt}.
8493 @xref{Output Formats,,Output Formats}.
8495 @item display/@var{fmt} @var{addr}
8496 For @var{fmt} @samp{i} or @samp{s}, or including a unit-size or a
8497 number of units, add the expression @var{addr} as a memory address to
8498 be examined each time your program stops. Examining means in effect
8499 doing @samp{x/@var{fmt} @var{addr}}. @xref{Memory, ,Examining Memory}.
8502 For example, @samp{display/i $pc} can be helpful, to see the machine
8503 instruction about to be executed each time execution stops (@samp{$pc}
8504 is a common name for the program counter; @pxref{Registers, ,Registers}).
8507 @kindex delete display
8509 @item undisplay @var{dnums}@dots{}
8510 @itemx delete display @var{dnums}@dots{}
8511 Remove items from the list of expressions to display. Specify the
8512 numbers of the displays that you want affected with the command
8513 argument @var{dnums}. It can be a single display number, one of the
8514 numbers shown in the first field of the @samp{info display} display;
8515 or it could be a range of display numbers, as in @code{2-4}.
8517 @code{undisplay} does not repeat if you press @key{RET} after using it.
8518 (Otherwise you would just get the error @samp{No display number @dots{}}.)
8520 @kindex disable display
8521 @item disable display @var{dnums}@dots{}
8522 Disable the display of item numbers @var{dnums}. A disabled display
8523 item is not printed automatically, but is not forgotten. It may be
8524 enabled again later. Specify the numbers of the displays that you
8525 want affected with the command argument @var{dnums}. It can be a
8526 single display number, one of the numbers shown in the first field of
8527 the @samp{info display} display; or it could be a range of display
8528 numbers, as in @code{2-4}.
8530 @kindex enable display
8531 @item enable display @var{dnums}@dots{}
8532 Enable display of item numbers @var{dnums}. It becomes effective once
8533 again in auto display of its expression, until you specify otherwise.
8534 Specify the numbers of the displays that you want affected with the
8535 command argument @var{dnums}. It can be a single display number, one
8536 of the numbers shown in the first field of the @samp{info display}
8537 display; or it could be a range of display numbers, as in @code{2-4}.
8540 Display the current values of the expressions on the list, just as is
8541 done when your program stops.
8543 @kindex info display
8545 Print the list of expressions previously set up to display
8546 automatically, each one with its item number, but without showing the
8547 values. This includes disabled expressions, which are marked as such.
8548 It also includes expressions which would not be displayed right now
8549 because they refer to automatic variables not currently available.
8552 @cindex display disabled out of scope
8553 If a display expression refers to local variables, then it does not make
8554 sense outside the lexical context for which it was set up. Such an
8555 expression is disabled when execution enters a context where one of its
8556 variables is not defined. For example, if you give the command
8557 @code{display last_char} while inside a function with an argument
8558 @code{last_char}, @value{GDBN} displays this argument while your program
8559 continues to stop inside that function. When it stops elsewhere---where
8560 there is no variable @code{last_char}---the display is disabled
8561 automatically. The next time your program stops where @code{last_char}
8562 is meaningful, you can enable the display expression once again.
8564 @node Print Settings
8565 @section Print Settings
8567 @cindex format options
8568 @cindex print settings
8569 @value{GDBN} provides the following ways to control how arrays, structures,
8570 and symbols are printed.
8573 These settings are useful for debugging programs in any language:
8577 @item set print address
8578 @itemx set print address on
8579 @cindex print/don't print memory addresses
8580 @value{GDBN} prints memory addresses showing the location of stack
8581 traces, structure values, pointer values, breakpoints, and so forth,
8582 even when it also displays the contents of those addresses. The default
8583 is @code{on}. For example, this is what a stack frame display looks like with
8584 @code{set print address on}:
8589 #0 set_quotes (lq=0x34c78 "<<", rq=0x34c88 ">>")
8591 530 if (lquote != def_lquote)
8595 @item set print address off
8596 Do not print addresses when displaying their contents. For example,
8597 this is the same stack frame displayed with @code{set print address off}:
8601 (@value{GDBP}) set print addr off
8603 #0 set_quotes (lq="<<", rq=">>") at input.c:530
8604 530 if (lquote != def_lquote)
8608 You can use @samp{set print address off} to eliminate all machine
8609 dependent displays from the @value{GDBN} interface. For example, with
8610 @code{print address off}, you should get the same text for backtraces on
8611 all machines---whether or not they involve pointer arguments.
8614 @item show print address
8615 Show whether or not addresses are to be printed.
8618 When @value{GDBN} prints a symbolic address, it normally prints the
8619 closest earlier symbol plus an offset. If that symbol does not uniquely
8620 identify the address (for example, it is a name whose scope is a single
8621 source file), you may need to clarify. One way to do this is with
8622 @code{info line}, for example @samp{info line *0x4537}. Alternately,
8623 you can set @value{GDBN} to print the source file and line number when
8624 it prints a symbolic address:
8627 @item set print symbol-filename on
8628 @cindex source file and line of a symbol
8629 @cindex symbol, source file and line
8630 Tell @value{GDBN} to print the source file name and line number of a
8631 symbol in the symbolic form of an address.
8633 @item set print symbol-filename off
8634 Do not print source file name and line number of a symbol. This is the
8637 @item show print symbol-filename
8638 Show whether or not @value{GDBN} will print the source file name and
8639 line number of a symbol in the symbolic form of an address.
8642 Another situation where it is helpful to show symbol filenames and line
8643 numbers is when disassembling code; @value{GDBN} shows you the line
8644 number and source file that corresponds to each instruction.
8646 Also, you may wish to see the symbolic form only if the address being
8647 printed is reasonably close to the closest earlier symbol:
8650 @item set print max-symbolic-offset @var{max-offset}
8651 @cindex maximum value for offset of closest symbol
8652 Tell @value{GDBN} to only display the symbolic form of an address if the
8653 offset between the closest earlier symbol and the address is less than
8654 @var{max-offset}. The default is 0, which tells @value{GDBN}
8655 to always print the symbolic form of an address if any symbol precedes it.
8657 @item show print max-symbolic-offset
8658 Ask how large the maximum offset is that @value{GDBN} prints in a
8662 @cindex wild pointer, interpreting
8663 @cindex pointer, finding referent
8664 If you have a pointer and you are not sure where it points, try
8665 @samp{set print symbol-filename on}. Then you can determine the name
8666 and source file location of the variable where it points, using
8667 @samp{p/a @var{pointer}}. This interprets the address in symbolic form.
8668 For example, here @value{GDBN} shows that a variable @code{ptt} points
8669 at another variable @code{t}, defined in @file{hi2.c}:
8672 (@value{GDBP}) set print symbol-filename on
8673 (@value{GDBP}) p/a ptt
8674 $4 = 0xe008 <t in hi2.c>
8678 @emph{Warning:} For pointers that point to a local variable, @samp{p/a}
8679 does not show the symbol name and filename of the referent, even with
8680 the appropriate @code{set print} options turned on.
8683 You can also enable @samp{/a}-like formatting all the time using
8684 @samp{set print symbol on}:
8687 @item set print symbol on
8688 Tell @value{GDBN} to print the symbol corresponding to an address, if
8691 @item set print symbol off
8692 Tell @value{GDBN} not to print the symbol corresponding to an
8693 address. In this mode, @value{GDBN} will still print the symbol
8694 corresponding to pointers to functions. This is the default.
8696 @item show print symbol
8697 Show whether @value{GDBN} will display the symbol corresponding to an
8701 Other settings control how different kinds of objects are printed:
8704 @item set print array
8705 @itemx set print array on
8706 @cindex pretty print arrays
8707 Pretty print arrays. This format is more convenient to read,
8708 but uses more space. The default is off.
8710 @item set print array off
8711 Return to compressed format for arrays.
8713 @item show print array
8714 Show whether compressed or pretty format is selected for displaying
8717 @cindex print array indexes
8718 @item set print array-indexes
8719 @itemx set print array-indexes on
8720 Print the index of each element when displaying arrays. May be more
8721 convenient to locate a given element in the array or quickly find the
8722 index of a given element in that printed array. The default is off.
8724 @item set print array-indexes off
8725 Stop printing element indexes when displaying arrays.
8727 @item show print array-indexes
8728 Show whether the index of each element is printed when displaying
8731 @item set print elements @var{number-of-elements}
8732 @cindex number of array elements to print
8733 @cindex limit on number of printed array elements
8734 Set a limit on how many elements of an array @value{GDBN} will print.
8735 If @value{GDBN} is printing a large array, it stops printing after it has
8736 printed the number of elements set by the @code{set print elements} command.
8737 This limit also applies to the display of strings.
8738 When @value{GDBN} starts, this limit is set to 200.
8739 Setting @var{number-of-elements} to zero means that the printing is unlimited.
8741 @item show print elements
8742 Display the number of elements of a large array that @value{GDBN} will print.
8743 If the number is 0, then the printing is unlimited.
8745 @item set print frame-arguments @var{value}
8746 @kindex set print frame-arguments
8747 @cindex printing frame argument values
8748 @cindex print all frame argument values
8749 @cindex print frame argument values for scalars only
8750 @cindex do not print frame argument values
8751 This command allows to control how the values of arguments are printed
8752 when the debugger prints a frame (@pxref{Frames}). The possible
8757 The values of all arguments are printed.
8760 Print the value of an argument only if it is a scalar. The value of more
8761 complex arguments such as arrays, structures, unions, etc, is replaced
8762 by @code{@dots{}}. This is the default. Here is an example where
8763 only scalar arguments are shown:
8766 #1 0x08048361 in call_me (i=3, s=@dots{}, ss=0xbf8d508c, u=@dots{}, e=green)
8771 None of the argument values are printed. Instead, the value of each argument
8772 is replaced by @code{@dots{}}. In this case, the example above now becomes:
8775 #1 0x08048361 in call_me (i=@dots{}, s=@dots{}, ss=@dots{}, u=@dots{}, e=@dots{})
8780 By default, only scalar arguments are printed. This command can be used
8781 to configure the debugger to print the value of all arguments, regardless
8782 of their type. However, it is often advantageous to not print the value
8783 of more complex parameters. For instance, it reduces the amount of
8784 information printed in each frame, making the backtrace more readable.
8785 Also, it improves performance when displaying Ada frames, because
8786 the computation of large arguments can sometimes be CPU-intensive,
8787 especially in large applications. Setting @code{print frame-arguments}
8788 to @code{scalars} (the default) or @code{none} avoids this computation,
8789 thus speeding up the display of each Ada frame.
8791 @item show print frame-arguments
8792 Show how the value of arguments should be displayed when printing a frame.
8794 @anchor{set print entry-values}
8795 @item set print entry-values @var{value}
8796 @kindex set print entry-values
8797 Set printing of frame argument values at function entry. In some cases
8798 @value{GDBN} can determine the value of function argument which was passed by
8799 the function caller, even if the value was modified inside the called function
8800 and therefore is different. With optimized code, the current value could be
8801 unavailable, but the entry value may still be known.
8803 The default value is @code{default} (see below for its description). Older
8804 @value{GDBN} behaved as with the setting @code{no}. Compilers not supporting
8805 this feature will behave in the @code{default} setting the same way as with the
8808 This functionality is currently supported only by DWARF 2 debugging format and
8809 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
8810 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
8813 The @var{value} parameter can be one of the following:
8817 Print only actual parameter values, never print values from function entry
8821 #0 different (val=6)
8822 #0 lost (val=<optimized out>)
8824 #0 invalid (val=<optimized out>)
8828 Print only parameter values from function entry point. The actual parameter
8829 values are never printed.
8831 #0 equal (val@@entry=5)
8832 #0 different (val@@entry=5)
8833 #0 lost (val@@entry=5)
8834 #0 born (val@@entry=<optimized out>)
8835 #0 invalid (val@@entry=<optimized out>)
8839 Print only parameter values from function entry point. If value from function
8840 entry point is not known while the actual value is known, print the actual
8841 value for such parameter.
8843 #0 equal (val@@entry=5)
8844 #0 different (val@@entry=5)
8845 #0 lost (val@@entry=5)
8847 #0 invalid (val@@entry=<optimized out>)
8851 Print actual parameter values. If actual parameter value is not known while
8852 value from function entry point is known, print the entry point value for such
8856 #0 different (val=6)
8857 #0 lost (val@@entry=5)
8859 #0 invalid (val=<optimized out>)
8863 Always print both the actual parameter value and its value from function entry
8864 point, even if values of one or both are not available due to compiler
8867 #0 equal (val=5, val@@entry=5)
8868 #0 different (val=6, val@@entry=5)
8869 #0 lost (val=<optimized out>, val@@entry=5)
8870 #0 born (val=10, val@@entry=<optimized out>)
8871 #0 invalid (val=<optimized out>, val@@entry=<optimized out>)
8875 Print the actual parameter value if it is known and also its value from
8876 function entry point if it is known. If neither is known, print for the actual
8877 value @code{<optimized out>}. If not in MI mode (@pxref{GDB/MI}) and if both
8878 values are known and identical, print the shortened
8879 @code{param=param@@entry=VALUE} notation.
8881 #0 equal (val=val@@entry=5)
8882 #0 different (val=6, val@@entry=5)
8883 #0 lost (val@@entry=5)
8885 #0 invalid (val=<optimized out>)
8889 Always print the actual parameter value. Print also its value from function
8890 entry point, but only if it is known. If not in MI mode (@pxref{GDB/MI}) and
8891 if both values are known and identical, print the shortened
8892 @code{param=param@@entry=VALUE} notation.
8894 #0 equal (val=val@@entry=5)
8895 #0 different (val=6, val@@entry=5)
8896 #0 lost (val=<optimized out>, val@@entry=5)
8898 #0 invalid (val=<optimized out>)
8902 For analysis messages on possible failures of frame argument values at function
8903 entry resolution see @ref{set debug entry-values}.
8905 @item show print entry-values
8906 Show the method being used for printing of frame argument values at function
8909 @item set print repeats
8910 @cindex repeated array elements
8911 Set the threshold for suppressing display of repeated array
8912 elements. When the number of consecutive identical elements of an
8913 array exceeds the threshold, @value{GDBN} prints the string
8914 @code{"<repeats @var{n} times>"}, where @var{n} is the number of
8915 identical repetitions, instead of displaying the identical elements
8916 themselves. Setting the threshold to zero will cause all elements to
8917 be individually printed. The default threshold is 10.
8919 @item show print repeats
8920 Display the current threshold for printing repeated identical
8923 @item set print null-stop
8924 @cindex @sc{null} elements in arrays
8925 Cause @value{GDBN} to stop printing the characters of an array when the first
8926 @sc{null} is encountered. This is useful when large arrays actually
8927 contain only short strings.
8930 @item show print null-stop
8931 Show whether @value{GDBN} stops printing an array on the first
8932 @sc{null} character.
8934 @item set print pretty on
8935 @cindex print structures in indented form
8936 @cindex indentation in structure display
8937 Cause @value{GDBN} to print structures in an indented format with one member
8938 per line, like this:
8953 @item set print pretty off
8954 Cause @value{GDBN} to print structures in a compact format, like this:
8958 $1 = @{next = 0x0, flags = @{sweet = 1, sour = 1@}, \
8959 meat = 0x54 "Pork"@}
8964 This is the default format.
8966 @item show print pretty
8967 Show which format @value{GDBN} is using to print structures.
8969 @item set print sevenbit-strings on
8970 @cindex eight-bit characters in strings
8971 @cindex octal escapes in strings
8972 Print using only seven-bit characters; if this option is set,
8973 @value{GDBN} displays any eight-bit characters (in strings or
8974 character values) using the notation @code{\}@var{nnn}. This setting is
8975 best if you are working in English (@sc{ascii}) and you use the
8976 high-order bit of characters as a marker or ``meta'' bit.
8978 @item set print sevenbit-strings off
8979 Print full eight-bit characters. This allows the use of more
8980 international character sets, and is the default.
8982 @item show print sevenbit-strings
8983 Show whether or not @value{GDBN} is printing only seven-bit characters.
8985 @item set print union on
8986 @cindex unions in structures, printing
8987 Tell @value{GDBN} to print unions which are contained in structures
8988 and other unions. This is the default setting.
8990 @item set print union off
8991 Tell @value{GDBN} not to print unions which are contained in
8992 structures and other unions. @value{GDBN} will print @code{"@{...@}"}
8995 @item show print union
8996 Ask @value{GDBN} whether or not it will print unions which are contained in
8997 structures and other unions.
8999 For example, given the declarations
9002 typedef enum @{Tree, Bug@} Species;
9003 typedef enum @{Big_tree, Acorn, Seedling@} Tree_forms;
9004 typedef enum @{Caterpillar, Cocoon, Butterfly@}
9015 struct thing foo = @{Tree, @{Acorn@}@};
9019 with @code{set print union on} in effect @samp{p foo} would print
9022 $1 = @{it = Tree, form = @{tree = Acorn, bug = Cocoon@}@}
9026 and with @code{set print union off} in effect it would print
9029 $1 = @{it = Tree, form = @{...@}@}
9033 @code{set print union} affects programs written in C-like languages
9039 These settings are of interest when debugging C@t{++} programs:
9042 @cindex demangling C@t{++} names
9043 @item set print demangle
9044 @itemx set print demangle on
9045 Print C@t{++} names in their source form rather than in the encoded
9046 (``mangled'') form passed to the assembler and linker for type-safe
9047 linkage. The default is on.
9049 @item show print demangle
9050 Show whether C@t{++} names are printed in mangled or demangled form.
9052 @item set print asm-demangle
9053 @itemx set print asm-demangle on
9054 Print C@t{++} names in their source form rather than their mangled form, even
9055 in assembler code printouts such as instruction disassemblies.
9058 @item show print asm-demangle
9059 Show whether C@t{++} names in assembly listings are printed in mangled
9062 @cindex C@t{++} symbol decoding style
9063 @cindex symbol decoding style, C@t{++}
9064 @kindex set demangle-style
9065 @item set demangle-style @var{style}
9066 Choose among several encoding schemes used by different compilers to
9067 represent C@t{++} names. The choices for @var{style} are currently:
9071 Allow @value{GDBN} to choose a decoding style by inspecting your program.
9072 This is the default.
9075 Decode based on the @sc{gnu} C@t{++} compiler (@code{g++}) encoding algorithm.
9078 Decode based on the HP ANSI C@t{++} (@code{aCC}) encoding algorithm.
9081 Decode based on the Lucid C@t{++} compiler (@code{lcc}) encoding algorithm.
9084 Decode using the algorithm in the @cite{C@t{++} Annotated Reference Manual}.
9085 @strong{Warning:} this setting alone is not sufficient to allow
9086 debugging @code{cfront}-generated executables. @value{GDBN} would
9087 require further enhancement to permit that.
9090 If you omit @var{style}, you will see a list of possible formats.
9092 @item show demangle-style
9093 Display the encoding style currently in use for decoding C@t{++} symbols.
9095 @item set print object
9096 @itemx set print object on
9097 @cindex derived type of an object, printing
9098 @cindex display derived types
9099 When displaying a pointer to an object, identify the @emph{actual}
9100 (derived) type of the object rather than the @emph{declared} type, using
9101 the virtual function table. Note that the virtual function table is
9102 required---this feature can only work for objects that have run-time
9103 type identification; a single virtual method in the object's declared
9104 type is sufficient. Note that this setting is also taken into account when
9105 working with variable objects via MI (@pxref{GDB/MI}).
9107 @item set print object off
9108 Display only the declared type of objects, without reference to the
9109 virtual function table. This is the default setting.
9111 @item show print object
9112 Show whether actual, or declared, object types are displayed.
9114 @item set print static-members
9115 @itemx set print static-members on
9116 @cindex static members of C@t{++} objects
9117 Print static members when displaying a C@t{++} object. The default is on.
9119 @item set print static-members off
9120 Do not print static members when displaying a C@t{++} object.
9122 @item show print static-members
9123 Show whether C@t{++} static members are printed or not.
9125 @item set print pascal_static-members
9126 @itemx set print pascal_static-members on
9127 @cindex static members of Pascal objects
9128 @cindex Pascal objects, static members display
9129 Print static members when displaying a Pascal object. The default is on.
9131 @item set print pascal_static-members off
9132 Do not print static members when displaying a Pascal object.
9134 @item show print pascal_static-members
9135 Show whether Pascal static members are printed or not.
9137 @c These don't work with HP ANSI C++ yet.
9138 @item set print vtbl
9139 @itemx set print vtbl on
9140 @cindex pretty print C@t{++} virtual function tables
9141 @cindex virtual functions (C@t{++}) display
9142 @cindex VTBL display
9143 Pretty print C@t{++} virtual function tables. The default is off.
9144 (The @code{vtbl} commands do not work on programs compiled with the HP
9145 ANSI C@t{++} compiler (@code{aCC}).)
9147 @item set print vtbl off
9148 Do not pretty print C@t{++} virtual function tables.
9150 @item show print vtbl
9151 Show whether C@t{++} virtual function tables are pretty printed, or not.
9154 @node Pretty Printing
9155 @section Pretty Printing
9157 @value{GDBN} provides a mechanism to allow pretty-printing of values using
9158 Python code. It greatly simplifies the display of complex objects. This
9159 mechanism works for both MI and the CLI.
9162 * Pretty-Printer Introduction:: Introduction to pretty-printers
9163 * Pretty-Printer Example:: An example pretty-printer
9164 * Pretty-Printer Commands:: Pretty-printer commands
9167 @node Pretty-Printer Introduction
9168 @subsection Pretty-Printer Introduction
9170 When @value{GDBN} prints a value, it first sees if there is a pretty-printer
9171 registered for the value. If there is then @value{GDBN} invokes the
9172 pretty-printer to print the value. Otherwise the value is printed normally.
9174 Pretty-printers are normally named. This makes them easy to manage.
9175 The @samp{info pretty-printer} command will list all the installed
9176 pretty-printers with their names.
9177 If a pretty-printer can handle multiple data types, then its
9178 @dfn{subprinters} are the printers for the individual data types.
9179 Each such subprinter has its own name.
9180 The format of the name is @var{printer-name};@var{subprinter-name}.
9182 Pretty-printers are installed by @dfn{registering} them with @value{GDBN}.
9183 Typically they are automatically loaded and registered when the corresponding
9184 debug information is loaded, thus making them available without having to
9185 do anything special.
9187 There are three places where a pretty-printer can be registered.
9191 Pretty-printers registered globally are available when debugging
9195 Pretty-printers registered with a program space are available only
9196 when debugging that program.
9197 @xref{Progspaces In Python}, for more details on program spaces in Python.
9200 Pretty-printers registered with an objfile are loaded and unloaded
9201 with the corresponding objfile (e.g., shared library).
9202 @xref{Objfiles In Python}, for more details on objfiles in Python.
9205 @xref{Selecting Pretty-Printers}, for further information on how
9206 pretty-printers are selected,
9208 @xref{Writing a Pretty-Printer}, for implementing pretty printers
9211 @node Pretty-Printer Example
9212 @subsection Pretty-Printer Example
9214 Here is how a C@t{++} @code{std::string} looks without a pretty-printer:
9217 (@value{GDBP}) print s
9219 static npos = 4294967295,
9221 <std::allocator<char>> = @{
9222 <__gnu_cxx::new_allocator<char>> = @{
9223 <No data fields>@}, <No data fields>
9225 members of std::basic_string<char, std::char_traits<char>,
9226 std::allocator<char> >::_Alloc_hider:
9227 _M_p = 0x804a014 "abcd"
9232 With a pretty-printer for @code{std::string} only the contents are printed:
9235 (@value{GDBP}) print s
9239 @node Pretty-Printer Commands
9240 @subsection Pretty-Printer Commands
9241 @cindex pretty-printer commands
9244 @kindex info pretty-printer
9245 @item info pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9246 Print the list of installed pretty-printers.
9247 This includes disabled pretty-printers, which are marked as such.
9249 @var{object-regexp} is a regular expression matching the objects
9250 whose pretty-printers to list.
9251 Objects can be @code{global}, the program space's file
9252 (@pxref{Progspaces In Python}),
9253 and the object files within that program space (@pxref{Objfiles In Python}).
9254 @xref{Selecting Pretty-Printers}, for details on how @value{GDBN}
9255 looks up a printer from these three objects.
9257 @var{name-regexp} is a regular expression matching the name of the printers
9260 @kindex disable pretty-printer
9261 @item disable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9262 Disable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9263 A disabled pretty-printer is not forgotten, it may be enabled again later.
9265 @kindex enable pretty-printer
9266 @item enable pretty-printer [@var{object-regexp} [@var{name-regexp}]]
9267 Enable pretty-printers matching @var{object-regexp} and @var{name-regexp}.
9272 Suppose we have three pretty-printers installed: one from library1.so
9273 named @code{foo} that prints objects of type @code{foo}, and
9274 another from library2.so named @code{bar} that prints two types of objects,
9275 @code{bar1} and @code{bar2}.
9278 (gdb) info pretty-printer
9285 (gdb) info pretty-printer library2
9290 (gdb) disable pretty-printer library1
9292 2 of 3 printers enabled
9293 (gdb) info pretty-printer
9300 (gdb) disable pretty-printer library2 bar:bar1
9302 1 of 3 printers enabled
9303 (gdb) info pretty-printer library2
9310 (gdb) disable pretty-printer library2 bar
9312 0 of 3 printers enabled
9313 (gdb) info pretty-printer library2
9322 Note that for @code{bar} the entire printer can be disabled,
9323 as can each individual subprinter.
9326 @section Value History
9328 @cindex value history
9329 @cindex history of values printed by @value{GDBN}
9330 Values printed by the @code{print} command are saved in the @value{GDBN}
9331 @dfn{value history}. This allows you to refer to them in other expressions.
9332 Values are kept until the symbol table is re-read or discarded
9333 (for example with the @code{file} or @code{symbol-file} commands).
9334 When the symbol table changes, the value history is discarded,
9335 since the values may contain pointers back to the types defined in the
9340 @cindex history number
9341 The values printed are given @dfn{history numbers} by which you can
9342 refer to them. These are successive integers starting with one.
9343 @code{print} shows you the history number assigned to a value by
9344 printing @samp{$@var{num} = } before the value; here @var{num} is the
9347 To refer to any previous value, use @samp{$} followed by the value's
9348 history number. The way @code{print} labels its output is designed to
9349 remind you of this. Just @code{$} refers to the most recent value in
9350 the history, and @code{$$} refers to the value before that.
9351 @code{$$@var{n}} refers to the @var{n}th value from the end; @code{$$2}
9352 is the value just prior to @code{$$}, @code{$$1} is equivalent to
9353 @code{$$}, and @code{$$0} is equivalent to @code{$}.
9355 For example, suppose you have just printed a pointer to a structure and
9356 want to see the contents of the structure. It suffices to type
9362 If you have a chain of structures where the component @code{next} points
9363 to the next one, you can print the contents of the next one with this:
9370 You can print successive links in the chain by repeating this
9371 command---which you can do by just typing @key{RET}.
9373 Note that the history records values, not expressions. If the value of
9374 @code{x} is 4 and you type these commands:
9382 then the value recorded in the value history by the @code{print} command
9383 remains 4 even though the value of @code{x} has changed.
9388 Print the last ten values in the value history, with their item numbers.
9389 This is like @samp{p@ $$9} repeated ten times, except that @code{show
9390 values} does not change the history.
9392 @item show values @var{n}
9393 Print ten history values centered on history item number @var{n}.
9396 Print ten history values just after the values last printed. If no more
9397 values are available, @code{show values +} produces no display.
9400 Pressing @key{RET} to repeat @code{show values @var{n}} has exactly the
9401 same effect as @samp{show values +}.
9403 @node Convenience Vars
9404 @section Convenience Variables
9406 @cindex convenience variables
9407 @cindex user-defined variables
9408 @value{GDBN} provides @dfn{convenience variables} that you can use within
9409 @value{GDBN} to hold on to a value and refer to it later. These variables
9410 exist entirely within @value{GDBN}; they are not part of your program, and
9411 setting a convenience variable has no direct effect on further execution
9412 of your program. That is why you can use them freely.
9414 Convenience variables are prefixed with @samp{$}. Any name preceded by
9415 @samp{$} can be used for a convenience variable, unless it is one of
9416 the predefined machine-specific register names (@pxref{Registers, ,Registers}).
9417 (Value history references, in contrast, are @emph{numbers} preceded
9418 by @samp{$}. @xref{Value History, ,Value History}.)
9420 You can save a value in a convenience variable with an assignment
9421 expression, just as you would set a variable in your program.
9425 set $foo = *object_ptr
9429 would save in @code{$foo} the value contained in the object pointed to by
9432 Using a convenience variable for the first time creates it, but its
9433 value is @code{void} until you assign a new value. You can alter the
9434 value with another assignment at any time.
9436 Convenience variables have no fixed types. You can assign a convenience
9437 variable any type of value, including structures and arrays, even if
9438 that variable already has a value of a different type. The convenience
9439 variable, when used as an expression, has the type of its current value.
9442 @kindex show convenience
9443 @cindex show all user variables and functions
9444 @item show convenience
9445 Print a list of convenience variables used so far, and their values,
9446 as well as a list of the convenience functions.
9447 Abbreviated @code{show conv}.
9449 @kindex init-if-undefined
9450 @cindex convenience variables, initializing
9451 @item init-if-undefined $@var{variable} = @var{expression}
9452 Set a convenience variable if it has not already been set. This is useful
9453 for user-defined commands that keep some state. It is similar, in concept,
9454 to using local static variables with initializers in C (except that
9455 convenience variables are global). It can also be used to allow users to
9456 override default values used in a command script.
9458 If the variable is already defined then the expression is not evaluated so
9459 any side-effects do not occur.
9462 One of the ways to use a convenience variable is as a counter to be
9463 incremented or a pointer to be advanced. For example, to print
9464 a field from successive elements of an array of structures:
9468 print bar[$i++]->contents
9472 Repeat that command by typing @key{RET}.
9474 Some convenience variables are created automatically by @value{GDBN} and given
9475 values likely to be useful.
9478 @vindex $_@r{, convenience variable}
9480 The variable @code{$_} is automatically set by the @code{x} command to
9481 the last address examined (@pxref{Memory, ,Examining Memory}). Other
9482 commands which provide a default address for @code{x} to examine also
9483 set @code{$_} to that address; these commands include @code{info line}
9484 and @code{info breakpoint}. The type of @code{$_} is @code{void *}
9485 except when set by the @code{x} command, in which case it is a pointer
9486 to the type of @code{$__}.
9488 @vindex $__@r{, convenience variable}
9490 The variable @code{$__} is automatically set by the @code{x} command
9491 to the value found in the last address examined. Its type is chosen
9492 to match the format in which the data was printed.
9495 @vindex $_exitcode@r{, convenience variable}
9496 The variable @code{$_exitcode} is automatically set to the exit code when
9497 the program being debugged terminates.
9500 @itemx $_probe_arg0@dots{}$_probe_arg11
9501 Arguments to a static probe. @xref{Static Probe Points}.
9504 @vindex $_sdata@r{, inspect, convenience variable}
9505 The variable @code{$_sdata} contains extra collected static tracepoint
9506 data. @xref{Tracepoint Actions,,Tracepoint Action Lists}. Note that
9507 @code{$_sdata} could be empty, if not inspecting a trace buffer, or
9508 if extra static tracepoint data has not been collected.
9511 @vindex $_siginfo@r{, convenience variable}
9512 The variable @code{$_siginfo} contains extra signal information
9513 (@pxref{extra signal information}). Note that @code{$_siginfo}
9514 could be empty, if the application has not yet received any signals.
9515 For example, it will be empty before you execute the @code{run} command.
9518 @vindex $_tlb@r{, convenience variable}
9519 The variable @code{$_tlb} is automatically set when debugging
9520 applications running on MS-Windows in native mode or connected to
9521 gdbserver that supports the @code{qGetTIBAddr} request.
9522 @xref{General Query Packets}.
9523 This variable contains the address of the thread information block.
9527 On HP-UX systems, if you refer to a function or variable name that
9528 begins with a dollar sign, @value{GDBN} searches for a user or system
9529 name first, before it searches for a convenience variable.
9531 @node Convenience Funs
9532 @section Convenience Functions
9534 @cindex convenience functions
9535 @value{GDBN} also supplies some @dfn{convenience functions}. These
9536 have a syntax similar to convenience variables. A convenience
9537 function can be used in an expression just like an ordinary function;
9538 however, a convenience function is implemented internally to
9541 These functions require @value{GDBN} to be configured with
9542 @code{Python} support.
9546 @item $_memeq(@var{buf1}, @var{buf2}, @var{length})
9547 @findex $_memeq@r{, convenience function}
9548 Returns one if the @var{length} bytes at the addresses given by
9549 @var{buf1} and @var{buf2} are equal.
9550 Otherwise it returns zero.
9552 @item $_regex(@var{str}, @var{regex})
9553 @findex $_regex@r{, convenience function}
9554 Returns one if the string @var{str} matches the regular expression
9555 @var{regex}. Otherwise it returns zero.
9556 The syntax of the regular expression is that specified by @code{Python}'s
9557 regular expression support.
9559 @item $_streq(@var{str1}, @var{str2})
9560 @findex $_streq@r{, convenience function}
9561 Returns one if the strings @var{str1} and @var{str2} are equal.
9562 Otherwise it returns zero.
9564 @item $_strlen(@var{str})
9565 @findex $_strlen@r{, convenience function}
9566 Returns the length of string @var{str}.
9570 @value{GDBN} provides the ability to list and get help on
9571 convenience functions.
9575 @kindex help function
9576 @cindex show all convenience functions
9577 Print a list of all convenience functions.
9584 You can refer to machine register contents, in expressions, as variables
9585 with names starting with @samp{$}. The names of registers are different
9586 for each machine; use @code{info registers} to see the names used on
9590 @kindex info registers
9591 @item info registers
9592 Print the names and values of all registers except floating-point
9593 and vector registers (in the selected stack frame).
9595 @kindex info all-registers
9596 @cindex floating point registers
9597 @item info all-registers
9598 Print the names and values of all registers, including floating-point
9599 and vector registers (in the selected stack frame).
9601 @item info registers @var{regname} @dots{}
9602 Print the @dfn{relativized} value of each specified register @var{regname}.
9603 As discussed in detail below, register values are normally relative to
9604 the selected stack frame. @var{regname} may be any register name valid on
9605 the machine you are using, with or without the initial @samp{$}.
9608 @cindex stack pointer register
9609 @cindex program counter register
9610 @cindex process status register
9611 @cindex frame pointer register
9612 @cindex standard registers
9613 @value{GDBN} has four ``standard'' register names that are available (in
9614 expressions) on most machines---whenever they do not conflict with an
9615 architecture's canonical mnemonics for registers. The register names
9616 @code{$pc} and @code{$sp} are used for the program counter register and
9617 the stack pointer. @code{$fp} is used for a register that contains a
9618 pointer to the current stack frame, and @code{$ps} is used for a
9619 register that contains the processor status. For example,
9620 you could print the program counter in hex with
9627 or print the instruction to be executed next with
9634 or add four to the stack pointer@footnote{This is a way of removing
9635 one word from the stack, on machines where stacks grow downward in
9636 memory (most machines, nowadays). This assumes that the innermost
9637 stack frame is selected; setting @code{$sp} is not allowed when other
9638 stack frames are selected. To pop entire frames off the stack,
9639 regardless of machine architecture, use @code{return};
9640 see @ref{Returning, ,Returning from a Function}.} with
9646 Whenever possible, these four standard register names are available on
9647 your machine even though the machine has different canonical mnemonics,
9648 so long as there is no conflict. The @code{info registers} command
9649 shows the canonical names. For example, on the SPARC, @code{info
9650 registers} displays the processor status register as @code{$psr} but you
9651 can also refer to it as @code{$ps}; and on x86-based machines @code{$ps}
9652 is an alias for the @sc{eflags} register.
9654 @value{GDBN} always considers the contents of an ordinary register as an
9655 integer when the register is examined in this way. Some machines have
9656 special registers which can hold nothing but floating point; these
9657 registers are considered to have floating point values. There is no way
9658 to refer to the contents of an ordinary register as floating point value
9659 (although you can @emph{print} it as a floating point value with
9660 @samp{print/f $@var{regname}}).
9662 Some registers have distinct ``raw'' and ``virtual'' data formats. This
9663 means that the data format in which the register contents are saved by
9664 the operating system is not the same one that your program normally
9665 sees. For example, the registers of the 68881 floating point
9666 coprocessor are always saved in ``extended'' (raw) format, but all C
9667 programs expect to work with ``double'' (virtual) format. In such
9668 cases, @value{GDBN} normally works with the virtual format only (the format
9669 that makes sense for your program), but the @code{info registers} command
9670 prints the data in both formats.
9672 @cindex SSE registers (x86)
9673 @cindex MMX registers (x86)
9674 Some machines have special registers whose contents can be interpreted
9675 in several different ways. For example, modern x86-based machines
9676 have SSE and MMX registers that can hold several values packed
9677 together in several different formats. @value{GDBN} refers to such
9678 registers in @code{struct} notation:
9681 (@value{GDBP}) print $xmm1
9683 v4_float = @{0, 3.43859137e-038, 1.54142831e-044, 1.821688e-044@},
9684 v2_double = @{9.92129282474342e-303, 2.7585945287983262e-313@},
9685 v16_int8 = "\000\000\000\000\3706;\001\v\000\000\000\r\000\000",
9686 v8_int16 = @{0, 0, 14072, 315, 11, 0, 13, 0@},
9687 v4_int32 = @{0, 20657912, 11, 13@},
9688 v2_int64 = @{88725056443645952, 55834574859@},
9689 uint128 = 0x0000000d0000000b013b36f800000000
9694 To set values of such registers, you need to tell @value{GDBN} which
9695 view of the register you wish to change, as if you were assigning
9696 value to a @code{struct} member:
9699 (@value{GDBP}) set $xmm1.uint128 = 0x000000000000000000000000FFFFFFFF
9702 Normally, register values are relative to the selected stack frame
9703 (@pxref{Selection, ,Selecting a Frame}). This means that you get the
9704 value that the register would contain if all stack frames farther in
9705 were exited and their saved registers restored. In order to see the
9706 true contents of hardware registers, you must select the innermost
9707 frame (with @samp{frame 0}).
9709 However, @value{GDBN} must deduce where registers are saved, from the machine
9710 code generated by your compiler. If some registers are not saved, or if
9711 @value{GDBN} is unable to locate the saved registers, the selected stack
9712 frame makes no difference.
9714 @node Floating Point Hardware
9715 @section Floating Point Hardware
9716 @cindex floating point
9718 Depending on the configuration, @value{GDBN} may be able to give
9719 you more information about the status of the floating point hardware.
9724 Display hardware-dependent information about the floating
9725 point unit. The exact contents and layout vary depending on the
9726 floating point chip. Currently, @samp{info float} is supported on
9727 the ARM and x86 machines.
9731 @section Vector Unit
9734 Depending on the configuration, @value{GDBN} may be able to give you
9735 more information about the status of the vector unit.
9740 Display information about the vector unit. The exact contents and
9741 layout vary depending on the hardware.
9744 @node OS Information
9745 @section Operating System Auxiliary Information
9746 @cindex OS information
9748 @value{GDBN} provides interfaces to useful OS facilities that can help
9749 you debug your program.
9751 @cindex auxiliary vector
9752 @cindex vector, auxiliary
9753 Some operating systems supply an @dfn{auxiliary vector} to programs at
9754 startup. This is akin to the arguments and environment that you
9755 specify for a program, but contains a system-dependent variety of
9756 binary values that tell system libraries important details about the
9757 hardware, operating system, and process. Each value's purpose is
9758 identified by an integer tag; the meanings are well-known but system-specific.
9759 Depending on the configuration and operating system facilities,
9760 @value{GDBN} may be able to show you this information. For remote
9761 targets, this functionality may further depend on the remote stub's
9762 support of the @samp{qXfer:auxv:read} packet, see
9763 @ref{qXfer auxiliary vector read}.
9768 Display the auxiliary vector of the inferior, which can be either a
9769 live process or a core dump file. @value{GDBN} prints each tag value
9770 numerically, and also shows names and text descriptions for recognized
9771 tags. Some values in the vector are numbers, some bit masks, and some
9772 pointers to strings or other data. @value{GDBN} displays each value in the
9773 most appropriate form for a recognized tag, and in hexadecimal for
9774 an unrecognized tag.
9777 On some targets, @value{GDBN} can access operating system-specific
9778 information and show it to you. The types of information available
9779 will differ depending on the type of operating system running on the
9780 target. The mechanism used to fetch the data is described in
9781 @ref{Operating System Information}. For remote targets, this
9782 functionality depends on the remote stub's support of the
9783 @samp{qXfer:osdata:read} packet, see @ref{qXfer osdata read}.
9787 @item info os @var{infotype}
9789 Display OS information of the requested type.
9791 On @sc{gnu}/Linux, the following values of @var{infotype} are valid:
9793 @anchor{linux info os infotypes}
9795 @kindex info os processes
9797 Display the list of processes on the target. For each process,
9798 @value{GDBN} prints the process identifier, the name of the user, the
9799 command corresponding to the process, and the list of processor cores
9800 that the process is currently running on. (To understand what these
9801 properties mean, for this and the following info types, please consult
9802 the general @sc{gnu}/Linux documentation.)
9804 @kindex info os procgroups
9806 Display the list of process groups on the target. For each process,
9807 @value{GDBN} prints the identifier of the process group that it belongs
9808 to, the command corresponding to the process group leader, the process
9809 identifier, and the command line of the process. The list is sorted
9810 first by the process group identifier, then by the process identifier,
9811 so that processes belonging to the same process group are grouped together
9812 and the process group leader is listed first.
9814 @kindex info os threads
9816 Display the list of threads running on the target. For each thread,
9817 @value{GDBN} prints the identifier of the process that the thread
9818 belongs to, the command of the process, the thread identifier, and the
9819 processor core that it is currently running on. The main thread of a
9820 process is not listed.
9822 @kindex info os files
9824 Display the list of open file descriptors on the target. For each
9825 file descriptor, @value{GDBN} prints the identifier of the process
9826 owning the descriptor, the command of the owning process, the value
9827 of the descriptor, and the target of the descriptor.
9829 @kindex info os sockets
9831 Display the list of Internet-domain sockets on the target. For each
9832 socket, @value{GDBN} prints the address and port of the local and
9833 remote endpoints, the current state of the connection, the creator of
9834 the socket, the IP address family of the socket, and the type of the
9839 Display the list of all System V shared-memory regions on the target.
9840 For each shared-memory region, @value{GDBN} prints the region key,
9841 the shared-memory identifier, the access permissions, the size of the
9842 region, the process that created the region, the process that last
9843 attached to or detached from the region, the current number of live
9844 attaches to the region, and the times at which the region was last
9845 attached to, detach from, and changed.
9847 @kindex info os semaphores
9849 Display the list of all System V semaphore sets on the target. For each
9850 semaphore set, @value{GDBN} prints the semaphore set key, the semaphore
9851 set identifier, the access permissions, the number of semaphores in the
9852 set, the user and group of the owner and creator of the semaphore set,
9853 and the times at which the semaphore set was operated upon and changed.
9857 Display the list of all System V message queues on the target. For each
9858 message queue, @value{GDBN} prints the message queue key, the message
9859 queue identifier, the access permissions, the current number of bytes
9860 on the queue, the current number of messages on the queue, the processes
9861 that last sent and received a message on the queue, the user and group
9862 of the owner and creator of the message queue, the times at which a
9863 message was last sent and received on the queue, and the time at which
9864 the message queue was last changed.
9866 @kindex info os modules
9868 Display the list of all loaded kernel modules on the target. For each
9869 module, @value{GDBN} prints the module name, the size of the module in
9870 bytes, the number of times the module is used, the dependencies of the
9871 module, the status of the module, and the address of the loaded module
9876 If @var{infotype} is omitted, then list the possible values for
9877 @var{infotype} and the kind of OS information available for each
9878 @var{infotype}. If the target does not return a list of possible
9879 types, this command will report an error.
9882 @node Memory Region Attributes
9883 @section Memory Region Attributes
9884 @cindex memory region attributes
9886 @dfn{Memory region attributes} allow you to describe special handling
9887 required by regions of your target's memory. @value{GDBN} uses
9888 attributes to determine whether to allow certain types of memory
9889 accesses; whether to use specific width accesses; and whether to cache
9890 target memory. By default the description of memory regions is
9891 fetched from the target (if the current target supports this), but the
9892 user can override the fetched regions.
9894 Defined memory regions can be individually enabled and disabled. When a
9895 memory region is disabled, @value{GDBN} uses the default attributes when
9896 accessing memory in that region. Similarly, if no memory regions have
9897 been defined, @value{GDBN} uses the default attributes when accessing
9900 When a memory region is defined, it is given a number to identify it;
9901 to enable, disable, or remove a memory region, you specify that number.
9905 @item mem @var{lower} @var{upper} @var{attributes}@dots{}
9906 Define a memory region bounded by @var{lower} and @var{upper} with
9907 attributes @var{attributes}@dots{}, and add it to the list of regions
9908 monitored by @value{GDBN}. Note that @var{upper} == 0 is a special
9909 case: it is treated as the target's maximum memory address.
9910 (0xffff on 16 bit targets, 0xffffffff on 32 bit targets, etc.)
9913 Discard any user changes to the memory regions and use target-supplied
9914 regions, if available, or no regions if the target does not support.
9917 @item delete mem @var{nums}@dots{}
9918 Remove memory regions @var{nums}@dots{} from the list of regions
9919 monitored by @value{GDBN}.
9922 @item disable mem @var{nums}@dots{}
9923 Disable monitoring of memory regions @var{nums}@dots{}.
9924 A disabled memory region is not forgotten.
9925 It may be enabled again later.
9928 @item enable mem @var{nums}@dots{}
9929 Enable monitoring of memory regions @var{nums}@dots{}.
9933 Print a table of all defined memory regions, with the following columns
9937 @item Memory Region Number
9938 @item Enabled or Disabled.
9939 Enabled memory regions are marked with @samp{y}.
9940 Disabled memory regions are marked with @samp{n}.
9943 The address defining the inclusive lower bound of the memory region.
9946 The address defining the exclusive upper bound of the memory region.
9949 The list of attributes set for this memory region.
9954 @subsection Attributes
9956 @subsubsection Memory Access Mode
9957 The access mode attributes set whether @value{GDBN} may make read or
9958 write accesses to a memory region.
9960 While these attributes prevent @value{GDBN} from performing invalid
9961 memory accesses, they do nothing to prevent the target system, I/O DMA,
9962 etc.@: from accessing memory.
9966 Memory is read only.
9968 Memory is write only.
9970 Memory is read/write. This is the default.
9973 @subsubsection Memory Access Size
9974 The access size attribute tells @value{GDBN} to use specific sized
9975 accesses in the memory region. Often memory mapped device registers
9976 require specific sized accesses. If no access size attribute is
9977 specified, @value{GDBN} may use accesses of any size.
9981 Use 8 bit memory accesses.
9983 Use 16 bit memory accesses.
9985 Use 32 bit memory accesses.
9987 Use 64 bit memory accesses.
9990 @c @subsubsection Hardware/Software Breakpoints
9991 @c The hardware/software breakpoint attributes set whether @value{GDBN}
9992 @c will use hardware or software breakpoints for the internal breakpoints
9993 @c used by the step, next, finish, until, etc. commands.
9997 @c Always use hardware breakpoints
9998 @c @item swbreak (default)
10001 @subsubsection Data Cache
10002 The data cache attributes set whether @value{GDBN} will cache target
10003 memory. While this generally improves performance by reducing debug
10004 protocol overhead, it can lead to incorrect results because @value{GDBN}
10005 does not know about volatile variables or memory mapped device
10010 Enable @value{GDBN} to cache target memory.
10012 Disable @value{GDBN} from caching target memory. This is the default.
10015 @subsection Memory Access Checking
10016 @value{GDBN} can be instructed to refuse accesses to memory that is
10017 not explicitly described. This can be useful if accessing such
10018 regions has undesired effects for a specific target, or to provide
10019 better error checking. The following commands control this behaviour.
10022 @kindex set mem inaccessible-by-default
10023 @item set mem inaccessible-by-default [on|off]
10024 If @code{on} is specified, make @value{GDBN} treat memory not
10025 explicitly described by the memory ranges as non-existent and refuse accesses
10026 to such memory. The checks are only performed if there's at least one
10027 memory range defined. If @code{off} is specified, make @value{GDBN}
10028 treat the memory not explicitly described by the memory ranges as RAM.
10029 The default value is @code{on}.
10030 @kindex show mem inaccessible-by-default
10031 @item show mem inaccessible-by-default
10032 Show the current handling of accesses to unknown memory.
10036 @c @subsubsection Memory Write Verification
10037 @c The memory write verification attributes set whether @value{GDBN}
10038 @c will re-reads data after each write to verify the write was successful.
10042 @c @item noverify (default)
10045 @node Dump/Restore Files
10046 @section Copy Between Memory and a File
10047 @cindex dump/restore files
10048 @cindex append data to a file
10049 @cindex dump data to a file
10050 @cindex restore data from a file
10052 You can use the commands @code{dump}, @code{append}, and
10053 @code{restore} to copy data between target memory and a file. The
10054 @code{dump} and @code{append} commands write data to a file, and the
10055 @code{restore} command reads data from a file back into the inferior's
10056 memory. Files may be in binary, Motorola S-record, Intel hex, or
10057 Tektronix Hex format; however, @value{GDBN} can only append to binary
10063 @item dump @r{[}@var{format}@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10064 @itemx dump @r{[}@var{format}@r{]} value @var{filename} @var{expr}
10065 Dump the contents of memory from @var{start_addr} to @var{end_addr},
10066 or the value of @var{expr}, to @var{filename} in the given format.
10068 The @var{format} parameter may be any one of:
10075 Motorola S-record format.
10077 Tektronix Hex format.
10080 @value{GDBN} uses the same definitions of these formats as the
10081 @sc{gnu} binary utilities, like @samp{objdump} and @samp{objcopy}. If
10082 @var{format} is omitted, @value{GDBN} dumps the data in raw binary
10086 @item append @r{[}binary@r{]} memory @var{filename} @var{start_addr} @var{end_addr}
10087 @itemx append @r{[}binary@r{]} value @var{filename} @var{expr}
10088 Append the contents of memory from @var{start_addr} to @var{end_addr},
10089 or the value of @var{expr}, to the file @var{filename}, in raw binary form.
10090 (@value{GDBN} can only append data to files in raw binary form.)
10093 @item restore @var{filename} @r{[}binary@r{]} @var{bias} @var{start} @var{end}
10094 Restore the contents of file @var{filename} into memory. The
10095 @code{restore} command can automatically recognize any known @sc{bfd}
10096 file format, except for raw binary. To restore a raw binary file you
10097 must specify the optional keyword @code{binary} after the filename.
10099 If @var{bias} is non-zero, its value will be added to the addresses
10100 contained in the file. Binary files always start at address zero, so
10101 they will be restored at address @var{bias}. Other bfd files have
10102 a built-in location; they will be restored at offset @var{bias}
10103 from that location.
10105 If @var{start} and/or @var{end} are non-zero, then only data between
10106 file offset @var{start} and file offset @var{end} will be restored.
10107 These offsets are relative to the addresses in the file, before
10108 the @var{bias} argument is applied.
10112 @node Core File Generation
10113 @section How to Produce a Core File from Your Program
10114 @cindex dump core from inferior
10116 A @dfn{core file} or @dfn{core dump} is a file that records the memory
10117 image of a running process and its process status (register values
10118 etc.). Its primary use is post-mortem debugging of a program that
10119 crashed while it ran outside a debugger. A program that crashes
10120 automatically produces a core file, unless this feature is disabled by
10121 the user. @xref{Files}, for information on invoking @value{GDBN} in
10122 the post-mortem debugging mode.
10124 Occasionally, you may wish to produce a core file of the program you
10125 are debugging in order to preserve a snapshot of its state.
10126 @value{GDBN} has a special command for that.
10130 @kindex generate-core-file
10131 @item generate-core-file [@var{file}]
10132 @itemx gcore [@var{file}]
10133 Produce a core dump of the inferior process. The optional argument
10134 @var{file} specifies the file name where to put the core dump. If not
10135 specified, the file name defaults to @file{core.@var{pid}}, where
10136 @var{pid} is the inferior process ID.
10138 Note that this command is implemented only for some systems (as of
10139 this writing, @sc{gnu}/Linux, FreeBSD, Solaris, and S390).
10142 @node Character Sets
10143 @section Character Sets
10144 @cindex character sets
10146 @cindex translating between character sets
10147 @cindex host character set
10148 @cindex target character set
10150 If the program you are debugging uses a different character set to
10151 represent characters and strings than the one @value{GDBN} uses itself,
10152 @value{GDBN} can automatically translate between the character sets for
10153 you. The character set @value{GDBN} uses we call the @dfn{host
10154 character set}; the one the inferior program uses we call the
10155 @dfn{target character set}.
10157 For example, if you are running @value{GDBN} on a @sc{gnu}/Linux system, which
10158 uses the ISO Latin 1 character set, but you are using @value{GDBN}'s
10159 remote protocol (@pxref{Remote Debugging}) to debug a program
10160 running on an IBM mainframe, which uses the @sc{ebcdic} character set,
10161 then the host character set is Latin-1, and the target character set is
10162 @sc{ebcdic}. If you give @value{GDBN} the command @code{set
10163 target-charset EBCDIC-US}, then @value{GDBN} translates between
10164 @sc{ebcdic} and Latin 1 as you print character or string values, or use
10165 character and string literals in expressions.
10167 @value{GDBN} has no way to automatically recognize which character set
10168 the inferior program uses; you must tell it, using the @code{set
10169 target-charset} command, described below.
10171 Here are the commands for controlling @value{GDBN}'s character set
10175 @item set target-charset @var{charset}
10176 @kindex set target-charset
10177 Set the current target character set to @var{charset}. To display the
10178 list of supported target character sets, type
10179 @kbd{@w{set target-charset @key{TAB}@key{TAB}}}.
10181 @item set host-charset @var{charset}
10182 @kindex set host-charset
10183 Set the current host character set to @var{charset}.
10185 By default, @value{GDBN} uses a host character set appropriate to the
10186 system it is running on; you can override that default using the
10187 @code{set host-charset} command. On some systems, @value{GDBN} cannot
10188 automatically determine the appropriate host character set. In this
10189 case, @value{GDBN} uses @samp{UTF-8}.
10191 @value{GDBN} can only use certain character sets as its host character
10192 set. If you type @kbd{@w{set host-charset @key{TAB}@key{TAB}}},
10193 @value{GDBN} will list the host character sets it supports.
10195 @item set charset @var{charset}
10196 @kindex set charset
10197 Set the current host and target character sets to @var{charset}. As
10198 above, if you type @kbd{@w{set charset @key{TAB}@key{TAB}}},
10199 @value{GDBN} will list the names of the character sets that can be used
10200 for both host and target.
10203 @kindex show charset
10204 Show the names of the current host and target character sets.
10206 @item show host-charset
10207 @kindex show host-charset
10208 Show the name of the current host character set.
10210 @item show target-charset
10211 @kindex show target-charset
10212 Show the name of the current target character set.
10214 @item set target-wide-charset @var{charset}
10215 @kindex set target-wide-charset
10216 Set the current target's wide character set to @var{charset}. This is
10217 the character set used by the target's @code{wchar_t} type. To
10218 display the list of supported wide character sets, type
10219 @kbd{@w{set target-wide-charset @key{TAB}@key{TAB}}}.
10221 @item show target-wide-charset
10222 @kindex show target-wide-charset
10223 Show the name of the current target's wide character set.
10226 Here is an example of @value{GDBN}'s character set support in action.
10227 Assume that the following source code has been placed in the file
10228 @file{charset-test.c}:
10234 = @{72, 101, 108, 108, 111, 44, 32, 119,
10235 111, 114, 108, 100, 33, 10, 0@};
10236 char ibm1047_hello[]
10237 = @{200, 133, 147, 147, 150, 107, 64, 166,
10238 150, 153, 147, 132, 90, 37, 0@};
10242 printf ("Hello, world!\n");
10246 In this program, @code{ascii_hello} and @code{ibm1047_hello} are arrays
10247 containing the string @samp{Hello, world!} followed by a newline,
10248 encoded in the @sc{ascii} and @sc{ibm1047} character sets.
10250 We compile the program, and invoke the debugger on it:
10253 $ gcc -g charset-test.c -o charset-test
10254 $ gdb -nw charset-test
10255 GNU gdb 2001-12-19-cvs
10256 Copyright 2001 Free Software Foundation, Inc.
10261 We can use the @code{show charset} command to see what character sets
10262 @value{GDBN} is currently using to interpret and display characters and
10266 (@value{GDBP}) show charset
10267 The current host and target character set is `ISO-8859-1'.
10271 For the sake of printing this manual, let's use @sc{ascii} as our
10272 initial character set:
10274 (@value{GDBP}) set charset ASCII
10275 (@value{GDBP}) show charset
10276 The current host and target character set is `ASCII'.
10280 Let's assume that @sc{ascii} is indeed the correct character set for our
10281 host system --- in other words, let's assume that if @value{GDBN} prints
10282 characters using the @sc{ascii} character set, our terminal will display
10283 them properly. Since our current target character set is also
10284 @sc{ascii}, the contents of @code{ascii_hello} print legibly:
10287 (@value{GDBP}) print ascii_hello
10288 $1 = 0x401698 "Hello, world!\n"
10289 (@value{GDBP}) print ascii_hello[0]
10294 @value{GDBN} uses the target character set for character and string
10295 literals you use in expressions:
10298 (@value{GDBP}) print '+'
10303 The @sc{ascii} character set uses the number 43 to encode the @samp{+}
10306 @value{GDBN} relies on the user to tell it which character set the
10307 target program uses. If we print @code{ibm1047_hello} while our target
10308 character set is still @sc{ascii}, we get jibberish:
10311 (@value{GDBP}) print ibm1047_hello
10312 $4 = 0x4016a8 "\310\205\223\223\226k@@\246\226\231\223\204Z%"
10313 (@value{GDBP}) print ibm1047_hello[0]
10318 If we invoke the @code{set target-charset} followed by @key{TAB}@key{TAB},
10319 @value{GDBN} tells us the character sets it supports:
10322 (@value{GDBP}) set target-charset
10323 ASCII EBCDIC-US IBM1047 ISO-8859-1
10324 (@value{GDBP}) set target-charset
10327 We can select @sc{ibm1047} as our target character set, and examine the
10328 program's strings again. Now the @sc{ascii} string is wrong, but
10329 @value{GDBN} translates the contents of @code{ibm1047_hello} from the
10330 target character set, @sc{ibm1047}, to the host character set,
10331 @sc{ascii}, and they display correctly:
10334 (@value{GDBP}) set target-charset IBM1047
10335 (@value{GDBP}) show charset
10336 The current host character set is `ASCII'.
10337 The current target character set is `IBM1047'.
10338 (@value{GDBP}) print ascii_hello
10339 $6 = 0x401698 "\110\145%%?\054\040\167?\162%\144\041\012"
10340 (@value{GDBP}) print ascii_hello[0]
10342 (@value{GDBP}) print ibm1047_hello
10343 $8 = 0x4016a8 "Hello, world!\n"
10344 (@value{GDBP}) print ibm1047_hello[0]
10349 As above, @value{GDBN} uses the target character set for character and
10350 string literals you use in expressions:
10353 (@value{GDBP}) print '+'
10358 The @sc{ibm1047} character set uses the number 78 to encode the @samp{+}
10361 @node Caching Remote Data
10362 @section Caching Data of Remote Targets
10363 @cindex caching data of remote targets
10365 @value{GDBN} caches data exchanged between the debugger and a
10366 remote target (@pxref{Remote Debugging}). Such caching generally improves
10367 performance, because it reduces the overhead of the remote protocol by
10368 bundling memory reads and writes into large chunks. Unfortunately, simply
10369 caching everything would lead to incorrect results, since @value{GDBN}
10370 does not necessarily know anything about volatile values, memory-mapped I/O
10371 addresses, etc. Furthermore, in non-stop mode (@pxref{Non-Stop Mode})
10372 memory can be changed @emph{while} a gdb command is executing.
10373 Therefore, by default, @value{GDBN} only caches data
10374 known to be on the stack@footnote{In non-stop mode, it is moderately
10375 rare for a running thread to modify the stack of a stopped thread
10376 in a way that would interfere with a backtrace, and caching of
10377 stack reads provides a significant speed up of remote backtraces.}.
10378 Other regions of memory can be explicitly marked as
10379 cacheable; see @pxref{Memory Region Attributes}.
10382 @kindex set remotecache
10383 @item set remotecache on
10384 @itemx set remotecache off
10385 This option no longer does anything; it exists for compatibility
10388 @kindex show remotecache
10389 @item show remotecache
10390 Show the current state of the obsolete remotecache flag.
10392 @kindex set stack-cache
10393 @item set stack-cache on
10394 @itemx set stack-cache off
10395 Enable or disable caching of stack accesses. When @code{ON}, use
10396 caching. By default, this option is @code{ON}.
10398 @kindex show stack-cache
10399 @item show stack-cache
10400 Show the current state of data caching for memory accesses.
10402 @kindex info dcache
10403 @item info dcache @r{[}line@r{]}
10404 Print the information about the data cache performance. The
10405 information displayed includes the dcache width and depth, and for
10406 each cache line, its number, address, and how many times it was
10407 referenced. This command is useful for debugging the data cache
10410 If a line number is specified, the contents of that line will be
10413 @item set dcache size @var{size}
10414 @cindex dcache size
10415 @kindex set dcache size
10416 Set maximum number of entries in dcache (dcache depth above).
10418 @item set dcache line-size @var{line-size}
10419 @cindex dcache line-size
10420 @kindex set dcache line-size
10421 Set number of bytes each dcache entry caches (dcache width above).
10422 Must be a power of 2.
10424 @item show dcache size
10425 @kindex show dcache size
10426 Show maximum number of dcache entries. See also @ref{Caching Remote Data, info dcache}.
10428 @item show dcache line-size
10429 @kindex show dcache line-size
10430 Show default size of dcache lines. See also @ref{Caching Remote Data, info dcache}.
10434 @node Searching Memory
10435 @section Search Memory
10436 @cindex searching memory
10438 Memory can be searched for a particular sequence of bytes with the
10439 @code{find} command.
10443 @item find @r{[}/@var{sn}@r{]} @var{start_addr}, +@var{len}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10444 @itemx find @r{[}/@var{sn}@r{]} @var{start_addr}, @var{end_addr}, @var{val1} @r{[}, @var{val2}, @dots{}@r{]}
10445 Search memory for the sequence of bytes specified by @var{val1}, @var{val2},
10446 etc. The search begins at address @var{start_addr} and continues for either
10447 @var{len} bytes or through to @var{end_addr} inclusive.
10450 @var{s} and @var{n} are optional parameters.
10451 They may be specified in either order, apart or together.
10454 @item @var{s}, search query size
10455 The size of each search query value.
10461 halfwords (two bytes)
10465 giant words (eight bytes)
10468 All values are interpreted in the current language.
10469 This means, for example, that if the current source language is C/C@t{++}
10470 then searching for the string ``hello'' includes the trailing '\0'.
10472 If the value size is not specified, it is taken from the
10473 value's type in the current language.
10474 This is useful when one wants to specify the search
10475 pattern as a mixture of types.
10476 Note that this means, for example, that in the case of C-like languages
10477 a search for an untyped 0x42 will search for @samp{(int) 0x42}
10478 which is typically four bytes.
10480 @item @var{n}, maximum number of finds
10481 The maximum number of matches to print. The default is to print all finds.
10484 You can use strings as search values. Quote them with double-quotes
10486 The string value is copied into the search pattern byte by byte,
10487 regardless of the endianness of the target and the size specification.
10489 The address of each match found is printed as well as a count of the
10490 number of matches found.
10492 The address of the last value found is stored in convenience variable
10494 A count of the number of matches is stored in @samp{$numfound}.
10496 For example, if stopped at the @code{printf} in this function:
10502 static char hello[] = "hello-hello";
10503 static struct @{ char c; short s; int i; @}
10504 __attribute__ ((packed)) mixed
10505 = @{ 'c', 0x1234, 0x87654321 @};
10506 printf ("%s\n", hello);
10511 you get during debugging:
10514 (gdb) find &hello[0], +sizeof(hello), "hello"
10515 0x804956d <hello.1620+6>
10517 (gdb) find &hello[0], +sizeof(hello), 'h', 'e', 'l', 'l', 'o'
10518 0x8049567 <hello.1620>
10519 0x804956d <hello.1620+6>
10521 (gdb) find /b1 &hello[0], +sizeof(hello), 'h', 0x65, 'l'
10522 0x8049567 <hello.1620>
10524 (gdb) find &mixed, +sizeof(mixed), (char) 'c', (short) 0x1234, (int) 0x87654321
10525 0x8049560 <mixed.1625>
10527 (gdb) print $numfound
10530 $2 = (void *) 0x8049560
10533 @node Optimized Code
10534 @chapter Debugging Optimized Code
10535 @cindex optimized code, debugging
10536 @cindex debugging optimized code
10538 Almost all compilers support optimization. With optimization
10539 disabled, the compiler generates assembly code that corresponds
10540 directly to your source code, in a simplistic way. As the compiler
10541 applies more powerful optimizations, the generated assembly code
10542 diverges from your original source code. With help from debugging
10543 information generated by the compiler, @value{GDBN} can map from
10544 the running program back to constructs from your original source.
10546 @value{GDBN} is more accurate with optimization disabled. If you
10547 can recompile without optimization, it is easier to follow the
10548 progress of your program during debugging. But, there are many cases
10549 where you may need to debug an optimized version.
10551 When you debug a program compiled with @samp{-g -O}, remember that the
10552 optimizer has rearranged your code; the debugger shows you what is
10553 really there. Do not be too surprised when the execution path does not
10554 exactly match your source file! An extreme example: if you define a
10555 variable, but never use it, @value{GDBN} never sees that
10556 variable---because the compiler optimizes it out of existence.
10558 Some things do not work as well with @samp{-g -O} as with just
10559 @samp{-g}, particularly on machines with instruction scheduling. If in
10560 doubt, recompile with @samp{-g} alone, and if this fixes the problem,
10561 please report it to us as a bug (including a test case!).
10562 @xref{Variables}, for more information about debugging optimized code.
10565 * Inline Functions:: How @value{GDBN} presents inlining
10566 * Tail Call Frames:: @value{GDBN} analysis of jumps to functions
10569 @node Inline Functions
10570 @section Inline Functions
10571 @cindex inline functions, debugging
10573 @dfn{Inlining} is an optimization that inserts a copy of the function
10574 body directly at each call site, instead of jumping to a shared
10575 routine. @value{GDBN} displays inlined functions just like
10576 non-inlined functions. They appear in backtraces. You can view their
10577 arguments and local variables, step into them with @code{step}, skip
10578 them with @code{next}, and escape from them with @code{finish}.
10579 You can check whether a function was inlined by using the
10580 @code{info frame} command.
10582 For @value{GDBN} to support inlined functions, the compiler must
10583 record information about inlining in the debug information ---
10584 @value{NGCC} using the @sc{dwarf 2} format does this, and several
10585 other compilers do also. @value{GDBN} only supports inlined functions
10586 when using @sc{dwarf 2}. Versions of @value{NGCC} before 4.1
10587 do not emit two required attributes (@samp{DW_AT_call_file} and
10588 @samp{DW_AT_call_line}); @value{GDBN} does not display inlined
10589 function calls with earlier versions of @value{NGCC}. It instead
10590 displays the arguments and local variables of inlined functions as
10591 local variables in the caller.
10593 The body of an inlined function is directly included at its call site;
10594 unlike a non-inlined function, there are no instructions devoted to
10595 the call. @value{GDBN} still pretends that the call site and the
10596 start of the inlined function are different instructions. Stepping to
10597 the call site shows the call site, and then stepping again shows
10598 the first line of the inlined function, even though no additional
10599 instructions are executed.
10601 This makes source-level debugging much clearer; you can see both the
10602 context of the call and then the effect of the call. Only stepping by
10603 a single instruction using @code{stepi} or @code{nexti} does not do
10604 this; single instruction steps always show the inlined body.
10606 There are some ways that @value{GDBN} does not pretend that inlined
10607 function calls are the same as normal calls:
10611 Setting breakpoints at the call site of an inlined function may not
10612 work, because the call site does not contain any code. @value{GDBN}
10613 may incorrectly move the breakpoint to the next line of the enclosing
10614 function, after the call. This limitation will be removed in a future
10615 version of @value{GDBN}; until then, set a breakpoint on an earlier line
10616 or inside the inlined function instead.
10619 @value{GDBN} cannot locate the return value of inlined calls after
10620 using the @code{finish} command. This is a limitation of compiler-generated
10621 debugging information; after @code{finish}, you can step to the next line
10622 and print a variable where your program stored the return value.
10626 @node Tail Call Frames
10627 @section Tail Call Frames
10628 @cindex tail call frames, debugging
10630 Function @code{B} can call function @code{C} in its very last statement. In
10631 unoptimized compilation the call of @code{C} is immediately followed by return
10632 instruction at the end of @code{B} code. Optimizing compiler may replace the
10633 call and return in function @code{B} into one jump to function @code{C}
10634 instead. Such use of a jump instruction is called @dfn{tail call}.
10636 During execution of function @code{C}, there will be no indication in the
10637 function call stack frames that it was tail-called from @code{B}. If function
10638 @code{A} regularly calls function @code{B} which tail-calls function @code{C},
10639 then @value{GDBN} will see @code{A} as the caller of @code{C}. However, in
10640 some cases @value{GDBN} can determine that @code{C} was tail-called from
10641 @code{B}, and it will then create fictitious call frame for that, with the
10642 return address set up as if @code{B} called @code{C} normally.
10644 This functionality is currently supported only by DWARF 2 debugging format and
10645 the compiler has to produce @samp{DW_TAG_GNU_call_site} tags. With
10646 @value{NGCC}, you need to specify @option{-O -g} during compilation, to get
10649 @kbd{info frame} command (@pxref{Frame Info}) will indicate the tail call frame
10650 kind by text @code{tail call frame} such as in this sample @value{GDBN} output:
10654 0x40066b <b(int, double)+11>: jmp 0x400640 <c(int, double)>
10656 Stack level 1, frame at 0x7fffffffda30:
10657 rip = 0x40066d in b (amd64-entry-value.cc:59); saved rip 0x4004c5
10658 tail call frame, caller of frame at 0x7fffffffda30
10659 source language c++.
10660 Arglist at unknown address.
10661 Locals at unknown address, Previous frame's sp is 0x7fffffffda30
10664 The detection of all the possible code path executions can find them ambiguous.
10665 There is no execution history stored (possible @ref{Reverse Execution} is never
10666 used for this purpose) and the last known caller could have reached the known
10667 callee by multiple different jump sequences. In such case @value{GDBN} still
10668 tries to show at least all the unambiguous top tail callers and all the
10669 unambiguous bottom tail calees, if any.
10672 @anchor{set debug entry-values}
10673 @item set debug entry-values
10674 @kindex set debug entry-values
10675 When set to on, enables printing of analysis messages for both frame argument
10676 values at function entry and tail calls. It will show all the possible valid
10677 tail calls code paths it has considered. It will also print the intersection
10678 of them with the final unambiguous (possibly partial or even empty) code path
10681 @item show debug entry-values
10682 @kindex show debug entry-values
10683 Show the current state of analysis messages printing for both frame argument
10684 values at function entry and tail calls.
10687 The analysis messages for tail calls can for example show why the virtual tail
10688 call frame for function @code{c} has not been recognized (due to the indirect
10689 reference by variable @code{x}):
10692 static void __attribute__((noinline, noclone)) c (void);
10693 void (*x) (void) = c;
10694 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10695 static void __attribute__((noinline, noclone)) c (void) @{ a (); @}
10696 int main (void) @{ x (); return 0; @}
10698 Breakpoint 1, DW_OP_GNU_entry_value resolving cannot find
10699 DW_TAG_GNU_call_site 0x40039a in main
10701 3 static void __attribute__((noinline, noclone)) a (void) @{ x++; @}
10704 #1 0x000000000040039a in main () at t.c:5
10707 Another possibility is an ambiguous virtual tail call frames resolution:
10711 static void __attribute__((noinline, noclone)) f (void) @{ i++; @}
10712 static void __attribute__((noinline, noclone)) e (void) @{ f (); @}
10713 static void __attribute__((noinline, noclone)) d (void) @{ f (); @}
10714 static void __attribute__((noinline, noclone)) c (void) @{ d (); @}
10715 static void __attribute__((noinline, noclone)) b (void)
10716 @{ if (i) c (); else e (); @}
10717 static void __attribute__((noinline, noclone)) a (void) @{ b (); @}
10718 int main (void) @{ a (); return 0; @}
10720 tailcall: initial: 0x4004d2(a) 0x4004ce(b) 0x4004b2(c) 0x4004a2(d)
10721 tailcall: compare: 0x4004d2(a) 0x4004cc(b) 0x400492(e)
10722 tailcall: reduced: 0x4004d2(a) |
10725 #1 0x00000000004004d2 in a () at t.c:8
10726 #2 0x0000000000400395 in main () at t.c:9
10729 @set CALLSEQ1A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}c@value{ARROW}d@value{ARROW}f}
10730 @set CALLSEQ2A @code{main@value{ARROW}a@value{ARROW}b@value{ARROW}e@value{ARROW}f}
10732 @c Convert CALLSEQ#A to CALLSEQ#B depending on HAVE_MAKEINFO_CLICK.
10733 @ifset HAVE_MAKEINFO_CLICK
10734 @set ARROW @click{}
10735 @set CALLSEQ1B @clicksequence{@value{CALLSEQ1A}}
10736 @set CALLSEQ2B @clicksequence{@value{CALLSEQ2A}}
10738 @ifclear HAVE_MAKEINFO_CLICK
10740 @set CALLSEQ1B @value{CALLSEQ1A}
10741 @set CALLSEQ2B @value{CALLSEQ2A}
10744 Frames #0 and #2 are real, #1 is a virtual tail call frame.
10745 The code can have possible execution paths @value{CALLSEQ1B} or
10746 @value{CALLSEQ2B}, @value{GDBN} cannot find which one from the inferior state.
10748 @code{initial:} state shows some random possible calling sequence @value{GDBN}
10749 has found. It then finds another possible calling sequcen - that one is
10750 prefixed by @code{compare:}. The non-ambiguous intersection of these two is
10751 printed as the @code{reduced:} calling sequence. That one could have many
10752 futher @code{compare:} and @code{reduced:} statements as long as there remain
10753 any non-ambiguous sequence entries.
10755 For the frame of function @code{b} in both cases there are different possible
10756 @code{$pc} values (@code{0x4004cc} or @code{0x4004ce}), therefore this frame is
10757 also ambigous. The only non-ambiguous frame is the one for function @code{a},
10758 therefore this one is displayed to the user while the ambiguous frames are
10761 There can be also reasons why printing of frame argument values at function
10766 static void __attribute__((noinline, noclone)) c (int i) @{ v++; @}
10767 static void __attribute__((noinline, noclone)) a (int i);
10768 static void __attribute__((noinline, noclone)) b (int i) @{ a (i); @}
10769 static void __attribute__((noinline, noclone)) a (int i)
10770 @{ if (i) b (i - 1); else c (0); @}
10771 int main (void) @{ a (5); return 0; @}
10774 #0 c (i=i@@entry=0) at t.c:2
10775 #1 0x0000000000400428 in a (DW_OP_GNU_entry_value resolving has found
10776 function "a" at 0x400420 can call itself via tail calls
10777 i=<optimized out>) at t.c:6
10778 #2 0x000000000040036e in main () at t.c:7
10781 @value{GDBN} cannot find out from the inferior state if and how many times did
10782 function @code{a} call itself (via function @code{b}) as these calls would be
10783 tail calls. Such tail calls would modify thue @code{i} variable, therefore
10784 @value{GDBN} cannot be sure the value it knows would be right - @value{GDBN}
10785 prints @code{<optimized out>} instead.
10788 @chapter C Preprocessor Macros
10790 Some languages, such as C and C@t{++}, provide a way to define and invoke
10791 ``preprocessor macros'' which expand into strings of tokens.
10792 @value{GDBN} can evaluate expressions containing macro invocations, show
10793 the result of macro expansion, and show a macro's definition, including
10794 where it was defined.
10796 You may need to compile your program specially to provide @value{GDBN}
10797 with information about preprocessor macros. Most compilers do not
10798 include macros in their debugging information, even when you compile
10799 with the @option{-g} flag. @xref{Compilation}.
10801 A program may define a macro at one point, remove that definition later,
10802 and then provide a different definition after that. Thus, at different
10803 points in the program, a macro may have different definitions, or have
10804 no definition at all. If there is a current stack frame, @value{GDBN}
10805 uses the macros in scope at that frame's source code line. Otherwise,
10806 @value{GDBN} uses the macros in scope at the current listing location;
10809 Whenever @value{GDBN} evaluates an expression, it always expands any
10810 macro invocations present in the expression. @value{GDBN} also provides
10811 the following commands for working with macros explicitly.
10815 @kindex macro expand
10816 @cindex macro expansion, showing the results of preprocessor
10817 @cindex preprocessor macro expansion, showing the results of
10818 @cindex expanding preprocessor macros
10819 @item macro expand @var{expression}
10820 @itemx macro exp @var{expression}
10821 Show the results of expanding all preprocessor macro invocations in
10822 @var{expression}. Since @value{GDBN} simply expands macros, but does
10823 not parse the result, @var{expression} need not be a valid expression;
10824 it can be any string of tokens.
10827 @item macro expand-once @var{expression}
10828 @itemx macro exp1 @var{expression}
10829 @cindex expand macro once
10830 @i{(This command is not yet implemented.)} Show the results of
10831 expanding those preprocessor macro invocations that appear explicitly in
10832 @var{expression}. Macro invocations appearing in that expansion are
10833 left unchanged. This command allows you to see the effect of a
10834 particular macro more clearly, without being confused by further
10835 expansions. Since @value{GDBN} simply expands macros, but does not
10836 parse the result, @var{expression} need not be a valid expression; it
10837 can be any string of tokens.
10840 @cindex macro definition, showing
10841 @cindex definition of a macro, showing
10842 @cindex macros, from debug info
10843 @item info macro [-a|-all] [--] @var{macro}
10844 Show the current definition or all definitions of the named @var{macro},
10845 and describe the source location or compiler command-line where that
10846 definition was established. The optional double dash is to signify the end of
10847 argument processing and the beginning of @var{macro} for non C-like macros where
10848 the macro may begin with a hyphen.
10850 @kindex info macros
10851 @item info macros @var{linespec}
10852 Show all macro definitions that are in effect at the location specified
10853 by @var{linespec}, and describe the source location or compiler
10854 command-line where those definitions were established.
10856 @kindex macro define
10857 @cindex user-defined macros
10858 @cindex defining macros interactively
10859 @cindex macros, user-defined
10860 @item macro define @var{macro} @var{replacement-list}
10861 @itemx macro define @var{macro}(@var{arglist}) @var{replacement-list}
10862 Introduce a definition for a preprocessor macro named @var{macro},
10863 invocations of which are replaced by the tokens given in
10864 @var{replacement-list}. The first form of this command defines an
10865 ``object-like'' macro, which takes no arguments; the second form
10866 defines a ``function-like'' macro, which takes the arguments given in
10869 A definition introduced by this command is in scope in every
10870 expression evaluated in @value{GDBN}, until it is removed with the
10871 @code{macro undef} command, described below. The definition overrides
10872 all definitions for @var{macro} present in the program being debugged,
10873 as well as any previous user-supplied definition.
10875 @kindex macro undef
10876 @item macro undef @var{macro}
10877 Remove any user-supplied definition for the macro named @var{macro}.
10878 This command only affects definitions provided with the @code{macro
10879 define} command, described above; it cannot remove definitions present
10880 in the program being debugged.
10884 List all the macros defined using the @code{macro define} command.
10887 @cindex macros, example of debugging with
10888 Here is a transcript showing the above commands in action. First, we
10889 show our source files:
10894 #include "sample.h"
10897 #define ADD(x) (M + x)
10902 printf ("Hello, world!\n");
10904 printf ("We're so creative.\n");
10906 printf ("Goodbye, world!\n");
10913 Now, we compile the program using the @sc{gnu} C compiler,
10914 @value{NGCC}. We pass the @option{-gdwarf-2}@footnote{This is the
10915 minimum. Recent versions of @value{NGCC} support @option{-gdwarf-3}
10916 and @option{-gdwarf-4}; we recommend always choosing the most recent
10917 version of DWARF.} @emph{and} @option{-g3} flags to ensure the compiler
10918 includes information about preprocessor macros in the debugging
10922 $ gcc -gdwarf-2 -g3 sample.c -o sample
10926 Now, we start @value{GDBN} on our sample program:
10930 GNU gdb 2002-05-06-cvs
10931 Copyright 2002 Free Software Foundation, Inc.
10932 GDB is free software, @dots{}
10936 We can expand macros and examine their definitions, even when the
10937 program is not running. @value{GDBN} uses the current listing position
10938 to decide which macro definitions are in scope:
10941 (@value{GDBP}) list main
10944 5 #define ADD(x) (M + x)
10949 10 printf ("Hello, world!\n");
10951 12 printf ("We're so creative.\n");
10952 (@value{GDBP}) info macro ADD
10953 Defined at /home/jimb/gdb/macros/play/sample.c:5
10954 #define ADD(x) (M + x)
10955 (@value{GDBP}) info macro Q
10956 Defined at /home/jimb/gdb/macros/play/sample.h:1
10957 included at /home/jimb/gdb/macros/play/sample.c:2
10959 (@value{GDBP}) macro expand ADD(1)
10960 expands to: (42 + 1)
10961 (@value{GDBP}) macro expand-once ADD(1)
10962 expands to: once (M + 1)
10966 In the example above, note that @code{macro expand-once} expands only
10967 the macro invocation explicit in the original text --- the invocation of
10968 @code{ADD} --- but does not expand the invocation of the macro @code{M},
10969 which was introduced by @code{ADD}.
10971 Once the program is running, @value{GDBN} uses the macro definitions in
10972 force at the source line of the current stack frame:
10975 (@value{GDBP}) break main
10976 Breakpoint 1 at 0x8048370: file sample.c, line 10.
10978 Starting program: /home/jimb/gdb/macros/play/sample
10980 Breakpoint 1, main () at sample.c:10
10981 10 printf ("Hello, world!\n");
10985 At line 10, the definition of the macro @code{N} at line 9 is in force:
10988 (@value{GDBP}) info macro N
10989 Defined at /home/jimb/gdb/macros/play/sample.c:9
10991 (@value{GDBP}) macro expand N Q M
10992 expands to: 28 < 42
10993 (@value{GDBP}) print N Q M
10998 As we step over directives that remove @code{N}'s definition, and then
10999 give it a new definition, @value{GDBN} finds the definition (or lack
11000 thereof) in force at each point:
11003 (@value{GDBP}) next
11005 12 printf ("We're so creative.\n");
11006 (@value{GDBP}) info macro N
11007 The symbol `N' has no definition as a C/C++ preprocessor macro
11008 at /home/jimb/gdb/macros/play/sample.c:12
11009 (@value{GDBP}) next
11011 14 printf ("Goodbye, world!\n");
11012 (@value{GDBP}) info macro N
11013 Defined at /home/jimb/gdb/macros/play/sample.c:13
11015 (@value{GDBP}) macro expand N Q M
11016 expands to: 1729 < 42
11017 (@value{GDBP}) print N Q M
11022 In addition to source files, macros can be defined on the compilation command
11023 line using the @option{-D@var{name}=@var{value}} syntax. For macros defined in
11024 such a way, @value{GDBN} displays the location of their definition as line zero
11025 of the source file submitted to the compiler.
11028 (@value{GDBP}) info macro __STDC__
11029 Defined at /home/jimb/gdb/macros/play/sample.c:0
11036 @chapter Tracepoints
11037 @c This chapter is based on the documentation written by Michael
11038 @c Snyder, David Taylor, Jim Blandy, and Elena Zannoni.
11040 @cindex tracepoints
11041 In some applications, it is not feasible for the debugger to interrupt
11042 the program's execution long enough for the developer to learn
11043 anything helpful about its behavior. If the program's correctness
11044 depends on its real-time behavior, delays introduced by a debugger
11045 might cause the program to change its behavior drastically, or perhaps
11046 fail, even when the code itself is correct. It is useful to be able
11047 to observe the program's behavior without interrupting it.
11049 Using @value{GDBN}'s @code{trace} and @code{collect} commands, you can
11050 specify locations in the program, called @dfn{tracepoints}, and
11051 arbitrary expressions to evaluate when those tracepoints are reached.
11052 Later, using the @code{tfind} command, you can examine the values
11053 those expressions had when the program hit the tracepoints. The
11054 expressions may also denote objects in memory---structures or arrays,
11055 for example---whose values @value{GDBN} should record; while visiting
11056 a particular tracepoint, you may inspect those objects as if they were
11057 in memory at that moment. However, because @value{GDBN} records these
11058 values without interacting with you, it can do so quickly and
11059 unobtrusively, hopefully not disturbing the program's behavior.
11061 The tracepoint facility is currently available only for remote
11062 targets. @xref{Targets}. In addition, your remote target must know
11063 how to collect trace data. This functionality is implemented in the
11064 remote stub; however, none of the stubs distributed with @value{GDBN}
11065 support tracepoints as of this writing. The format of the remote
11066 packets used to implement tracepoints are described in @ref{Tracepoint
11069 It is also possible to get trace data from a file, in a manner reminiscent
11070 of corefiles; you specify the filename, and use @code{tfind} to search
11071 through the file. @xref{Trace Files}, for more details.
11073 This chapter describes the tracepoint commands and features.
11076 * Set Tracepoints::
11077 * Analyze Collected Data::
11078 * Tracepoint Variables::
11082 @node Set Tracepoints
11083 @section Commands to Set Tracepoints
11085 Before running such a @dfn{trace experiment}, an arbitrary number of
11086 tracepoints can be set. A tracepoint is actually a special type of
11087 breakpoint (@pxref{Set Breaks}), so you can manipulate it using
11088 standard breakpoint commands. For instance, as with breakpoints,
11089 tracepoint numbers are successive integers starting from one, and many
11090 of the commands associated with tracepoints take the tracepoint number
11091 as their argument, to identify which tracepoint to work on.
11093 For each tracepoint, you can specify, in advance, some arbitrary set
11094 of data that you want the target to collect in the trace buffer when
11095 it hits that tracepoint. The collected data can include registers,
11096 local variables, or global data. Later, you can use @value{GDBN}
11097 commands to examine the values these data had at the time the
11098 tracepoint was hit.
11100 Tracepoints do not support every breakpoint feature. Ignore counts on
11101 tracepoints have no effect, and tracepoints cannot run @value{GDBN}
11102 commands when they are hit. Tracepoints may not be thread-specific
11105 @cindex fast tracepoints
11106 Some targets may support @dfn{fast tracepoints}, which are inserted in
11107 a different way (such as with a jump instead of a trap), that is
11108 faster but possibly restricted in where they may be installed.
11110 @cindex static tracepoints
11111 @cindex markers, static tracepoints
11112 @cindex probing markers, static tracepoints
11113 Regular and fast tracepoints are dynamic tracing facilities, meaning
11114 that they can be used to insert tracepoints at (almost) any location
11115 in the target. Some targets may also support controlling @dfn{static
11116 tracepoints} from @value{GDBN}. With static tracing, a set of
11117 instrumentation points, also known as @dfn{markers}, are embedded in
11118 the target program, and can be activated or deactivated by name or
11119 address. These are usually placed at locations which facilitate
11120 investigating what the target is actually doing. @value{GDBN}'s
11121 support for static tracing includes being able to list instrumentation
11122 points, and attach them with @value{GDBN} defined high level
11123 tracepoints that expose the whole range of convenience of
11124 @value{GDBN}'s tracepoints support. Namely, support for collecting
11125 registers values and values of global or local (to the instrumentation
11126 point) variables; tracepoint conditions and trace state variables.
11127 The act of installing a @value{GDBN} static tracepoint on an
11128 instrumentation point, or marker, is referred to as @dfn{probing} a
11129 static tracepoint marker.
11131 @code{gdbserver} supports tracepoints on some target systems.
11132 @xref{Server,,Tracepoints support in @code{gdbserver}}.
11134 This section describes commands to set tracepoints and associated
11135 conditions and actions.
11138 * Create and Delete Tracepoints::
11139 * Enable and Disable Tracepoints::
11140 * Tracepoint Passcounts::
11141 * Tracepoint Conditions::
11142 * Trace State Variables::
11143 * Tracepoint Actions::
11144 * Listing Tracepoints::
11145 * Listing Static Tracepoint Markers::
11146 * Starting and Stopping Trace Experiments::
11147 * Tracepoint Restrictions::
11150 @node Create and Delete Tracepoints
11151 @subsection Create and Delete Tracepoints
11154 @cindex set tracepoint
11156 @item trace @var{location}
11157 The @code{trace} command is very similar to the @code{break} command.
11158 Its argument @var{location} can be a source line, a function name, or
11159 an address in the target program. @xref{Specify Location}. The
11160 @code{trace} command defines a tracepoint, which is a point in the
11161 target program where the debugger will briefly stop, collect some
11162 data, and then allow the program to continue. Setting a tracepoint or
11163 changing its actions takes effect immediately if the remote stub
11164 supports the @samp{InstallInTrace} feature (@pxref{install tracepoint
11166 If remote stub doesn't support the @samp{InstallInTrace} feature, all
11167 these changes don't take effect until the next @code{tstart}
11168 command, and once a trace experiment is running, further changes will
11169 not have any effect until the next trace experiment starts. In addition,
11170 @value{GDBN} supports @dfn{pending tracepoints}---tracepoints whose
11171 address is not yet resolved. (This is similar to pending breakpoints.)
11172 Pending tracepoints are not downloaded to the target and not installed
11173 until they are resolved. The resolution of pending tracepoints requires
11174 @value{GDBN} support---when debugging with the remote target, and
11175 @value{GDBN} disconnects from the remote stub (@pxref{disconnected
11176 tracing}), pending tracepoints can not be resolved (and downloaded to
11177 the remote stub) while @value{GDBN} is disconnected.
11179 Here are some examples of using the @code{trace} command:
11182 (@value{GDBP}) @b{trace foo.c:121} // a source file and line number
11184 (@value{GDBP}) @b{trace +2} // 2 lines forward
11186 (@value{GDBP}) @b{trace my_function} // first source line of function
11188 (@value{GDBP}) @b{trace *my_function} // EXACT start address of function
11190 (@value{GDBP}) @b{trace *0x2117c4} // an address
11194 You can abbreviate @code{trace} as @code{tr}.
11196 @item trace @var{location} if @var{cond}
11197 Set a tracepoint with condition @var{cond}; evaluate the expression
11198 @var{cond} each time the tracepoint is reached, and collect data only
11199 if the value is nonzero---that is, if @var{cond} evaluates as true.
11200 @xref{Tracepoint Conditions, ,Tracepoint Conditions}, for more
11201 information on tracepoint conditions.
11203 @item ftrace @var{location} [ if @var{cond} ]
11204 @cindex set fast tracepoint
11205 @cindex fast tracepoints, setting
11207 The @code{ftrace} command sets a fast tracepoint. For targets that
11208 support them, fast tracepoints will use a more efficient but possibly
11209 less general technique to trigger data collection, such as a jump
11210 instruction instead of a trap, or some sort of hardware support. It
11211 may not be possible to create a fast tracepoint at the desired
11212 location, in which case the command will exit with an explanatory
11215 @value{GDBN} handles arguments to @code{ftrace} exactly as for
11218 On 32-bit x86-architecture systems, fast tracepoints normally need to
11219 be placed at an instruction that is 5 bytes or longer, but can be
11220 placed at 4-byte instructions if the low 64K of memory of the target
11221 program is available to install trampolines. Some Unix-type systems,
11222 such as @sc{gnu}/Linux, exclude low addresses from the program's
11223 address space; but for instance with the Linux kernel it is possible
11224 to let @value{GDBN} use this area by doing a @command{sysctl} command
11225 to set the @code{mmap_min_addr} kernel parameter, as in
11228 sudo sysctl -w vm.mmap_min_addr=32768
11232 which sets the low address to 32K, which leaves plenty of room for
11233 trampolines. The minimum address should be set to a page boundary.
11235 @item strace @var{location} [ if @var{cond} ]
11236 @cindex set static tracepoint
11237 @cindex static tracepoints, setting
11238 @cindex probe static tracepoint marker
11240 The @code{strace} command sets a static tracepoint. For targets that
11241 support it, setting a static tracepoint probes a static
11242 instrumentation point, or marker, found at @var{location}. It may not
11243 be possible to set a static tracepoint at the desired location, in
11244 which case the command will exit with an explanatory message.
11246 @value{GDBN} handles arguments to @code{strace} exactly as for
11247 @code{trace}, with the addition that the user can also specify
11248 @code{-m @var{marker}} as @var{location}. This probes the marker
11249 identified by the @var{marker} string identifier. This identifier
11250 depends on the static tracepoint backend library your program is
11251 using. You can find all the marker identifiers in the @samp{ID} field
11252 of the @code{info static-tracepoint-markers} command output.
11253 @xref{Listing Static Tracepoint Markers,,Listing Static Tracepoint
11254 Markers}. For example, in the following small program using the UST
11260 trace_mark(ust, bar33, "str %s", "FOOBAZ");
11265 the marker id is composed of joining the first two arguments to the
11266 @code{trace_mark} call with a slash, which translates to:
11269 (@value{GDBP}) info static-tracepoint-markers
11270 Cnt Enb ID Address What
11271 1 n ust/bar33 0x0000000000400ddc in main at stexample.c:22
11277 so you may probe the marker above with:
11280 (@value{GDBP}) strace -m ust/bar33
11283 Static tracepoints accept an extra collect action --- @code{collect
11284 $_sdata}. This collects arbitrary user data passed in the probe point
11285 call to the tracing library. In the UST example above, you'll see
11286 that the third argument to @code{trace_mark} is a printf-like format
11287 string. The user data is then the result of running that formating
11288 string against the following arguments. Note that @code{info
11289 static-tracepoint-markers} command output lists that format string in
11290 the @samp{Data:} field.
11292 You can inspect this data when analyzing the trace buffer, by printing
11293 the $_sdata variable like any other variable available to
11294 @value{GDBN}. @xref{Tracepoint Actions,,Tracepoint Action Lists}.
11297 @cindex last tracepoint number
11298 @cindex recent tracepoint number
11299 @cindex tracepoint number
11300 The convenience variable @code{$tpnum} records the tracepoint number
11301 of the most recently set tracepoint.
11303 @kindex delete tracepoint
11304 @cindex tracepoint deletion
11305 @item delete tracepoint @r{[}@var{num}@r{]}
11306 Permanently delete one or more tracepoints. With no argument, the
11307 default is to delete all tracepoints. Note that the regular
11308 @code{delete} command can remove tracepoints also.
11313 (@value{GDBP}) @b{delete trace 1 2 3} // remove three tracepoints
11315 (@value{GDBP}) @b{delete trace} // remove all tracepoints
11319 You can abbreviate this command as @code{del tr}.
11322 @node Enable and Disable Tracepoints
11323 @subsection Enable and Disable Tracepoints
11325 These commands are deprecated; they are equivalent to plain @code{disable} and @code{enable}.
11328 @kindex disable tracepoint
11329 @item disable tracepoint @r{[}@var{num}@r{]}
11330 Disable tracepoint @var{num}, or all tracepoints if no argument
11331 @var{num} is given. A disabled tracepoint will have no effect during
11332 a trace experiment, but it is not forgotten. You can re-enable
11333 a disabled tracepoint using the @code{enable tracepoint} command.
11334 If the command is issued during a trace experiment and the debug target
11335 has support for disabling tracepoints during a trace experiment, then the
11336 change will be effective immediately. Otherwise, it will be applied to the
11337 next trace experiment.
11339 @kindex enable tracepoint
11340 @item enable tracepoint @r{[}@var{num}@r{]}
11341 Enable tracepoint @var{num}, or all tracepoints. If this command is
11342 issued during a trace experiment and the debug target supports enabling
11343 tracepoints during a trace experiment, then the enabled tracepoints will
11344 become effective immediately. Otherwise, they will become effective the
11345 next time a trace experiment is run.
11348 @node Tracepoint Passcounts
11349 @subsection Tracepoint Passcounts
11353 @cindex tracepoint pass count
11354 @item passcount @r{[}@var{n} @r{[}@var{num}@r{]]}
11355 Set the @dfn{passcount} of a tracepoint. The passcount is a way to
11356 automatically stop a trace experiment. If a tracepoint's passcount is
11357 @var{n}, then the trace experiment will be automatically stopped on
11358 the @var{n}'th time that tracepoint is hit. If the tracepoint number
11359 @var{num} is not specified, the @code{passcount} command sets the
11360 passcount of the most recently defined tracepoint. If no passcount is
11361 given, the trace experiment will run until stopped explicitly by the
11367 (@value{GDBP}) @b{passcount 5 2} // Stop on the 5th execution of
11368 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// tracepoint 2}
11370 (@value{GDBP}) @b{passcount 12} // Stop on the 12th execution of the
11371 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// most recently defined tracepoint.}
11372 (@value{GDBP}) @b{trace foo}
11373 (@value{GDBP}) @b{pass 3}
11374 (@value{GDBP}) @b{trace bar}
11375 (@value{GDBP}) @b{pass 2}
11376 (@value{GDBP}) @b{trace baz}
11377 (@value{GDBP}) @b{pass 1} // Stop tracing when foo has been
11378 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// executed 3 times OR when bar has}
11379 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// been executed 2 times}
11380 @exdent @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @ @code{// OR when baz has been executed 1 time.}
11384 @node Tracepoint Conditions
11385 @subsection Tracepoint Conditions
11386 @cindex conditional tracepoints
11387 @cindex tracepoint conditions
11389 The simplest sort of tracepoint collects data every time your program
11390 reaches a specified place. You can also specify a @dfn{condition} for
11391 a tracepoint. A condition is just a Boolean expression in your
11392 programming language (@pxref{Expressions, ,Expressions}). A
11393 tracepoint with a condition evaluates the expression each time your
11394 program reaches it, and data collection happens only if the condition
11397 Tracepoint conditions can be specified when a tracepoint is set, by
11398 using @samp{if} in the arguments to the @code{trace} command.
11399 @xref{Create and Delete Tracepoints, ,Setting Tracepoints}. They can
11400 also be set or changed at any time with the @code{condition} command,
11401 just as with breakpoints.
11403 Unlike breakpoint conditions, @value{GDBN} does not actually evaluate
11404 the conditional expression itself. Instead, @value{GDBN} encodes the
11405 expression into an agent expression (@pxref{Agent Expressions})
11406 suitable for execution on the target, independently of @value{GDBN}.
11407 Global variables become raw memory locations, locals become stack
11408 accesses, and so forth.
11410 For instance, suppose you have a function that is usually called
11411 frequently, but should not be called after an error has occurred. You
11412 could use the following tracepoint command to collect data about calls
11413 of that function that happen while the error code is propagating
11414 through the program; an unconditional tracepoint could end up
11415 collecting thousands of useless trace frames that you would have to
11419 (@value{GDBP}) @kbd{trace normal_operation if errcode > 0}
11422 @node Trace State Variables
11423 @subsection Trace State Variables
11424 @cindex trace state variables
11426 A @dfn{trace state variable} is a special type of variable that is
11427 created and managed by target-side code. The syntax is the same as
11428 that for GDB's convenience variables (a string prefixed with ``$''),
11429 but they are stored on the target. They must be created explicitly,
11430 using a @code{tvariable} command. They are always 64-bit signed
11433 Trace state variables are remembered by @value{GDBN}, and downloaded
11434 to the target along with tracepoint information when the trace
11435 experiment starts. There are no intrinsic limits on the number of
11436 trace state variables, beyond memory limitations of the target.
11438 @cindex convenience variables, and trace state variables
11439 Although trace state variables are managed by the target, you can use
11440 them in print commands and expressions as if they were convenience
11441 variables; @value{GDBN} will get the current value from the target
11442 while the trace experiment is running. Trace state variables share
11443 the same namespace as other ``$'' variables, which means that you
11444 cannot have trace state variables with names like @code{$23} or
11445 @code{$pc}, nor can you have a trace state variable and a convenience
11446 variable with the same name.
11450 @item tvariable $@var{name} [ = @var{expression} ]
11452 The @code{tvariable} command creates a new trace state variable named
11453 @code{$@var{name}}, and optionally gives it an initial value of
11454 @var{expression}. @var{expression} is evaluated when this command is
11455 entered; the result will be converted to an integer if possible,
11456 otherwise @value{GDBN} will report an error. A subsequent
11457 @code{tvariable} command specifying the same name does not create a
11458 variable, but instead assigns the supplied initial value to the
11459 existing variable of that name, overwriting any previous initial
11460 value. The default initial value is 0.
11462 @item info tvariables
11463 @kindex info tvariables
11464 List all the trace state variables along with their initial values.
11465 Their current values may also be displayed, if the trace experiment is
11468 @item delete tvariable @r{[} $@var{name} @dots{} @r{]}
11469 @kindex delete tvariable
11470 Delete the given trace state variables, or all of them if no arguments
11475 @node Tracepoint Actions
11476 @subsection Tracepoint Action Lists
11480 @cindex tracepoint actions
11481 @item actions @r{[}@var{num}@r{]}
11482 This command will prompt for a list of actions to be taken when the
11483 tracepoint is hit. If the tracepoint number @var{num} is not
11484 specified, this command sets the actions for the one that was most
11485 recently defined (so that you can define a tracepoint and then say
11486 @code{actions} without bothering about its number). You specify the
11487 actions themselves on the following lines, one action at a time, and
11488 terminate the actions list with a line containing just @code{end}. So
11489 far, the only defined actions are @code{collect}, @code{teval}, and
11490 @code{while-stepping}.
11492 @code{actions} is actually equivalent to @code{commands} (@pxref{Break
11493 Commands, ,Breakpoint Command Lists}), except that only the defined
11494 actions are allowed; any other @value{GDBN} command is rejected.
11496 @cindex remove actions from a tracepoint
11497 To remove all actions from a tracepoint, type @samp{actions @var{num}}
11498 and follow it immediately with @samp{end}.
11501 (@value{GDBP}) @b{collect @var{data}} // collect some data
11503 (@value{GDBP}) @b{while-stepping 5} // single-step 5 times, collect data
11505 (@value{GDBP}) @b{end} // signals the end of actions.
11508 In the following example, the action list begins with @code{collect}
11509 commands indicating the things to be collected when the tracepoint is
11510 hit. Then, in order to single-step and collect additional data
11511 following the tracepoint, a @code{while-stepping} command is used,
11512 followed by the list of things to be collected after each step in a
11513 sequence of single steps. The @code{while-stepping} command is
11514 terminated by its own separate @code{end} command. Lastly, the action
11515 list is terminated by an @code{end} command.
11518 (@value{GDBP}) @b{trace foo}
11519 (@value{GDBP}) @b{actions}
11520 Enter actions for tracepoint 1, one per line:
11523 > while-stepping 12
11524 > collect $pc, arr[i]
11529 @kindex collect @r{(tracepoints)}
11530 @item collect@r{[}/@var{mods}@r{]} @var{expr1}, @var{expr2}, @dots{}
11531 Collect values of the given expressions when the tracepoint is hit.
11532 This command accepts a comma-separated list of any valid expressions.
11533 In addition to global, static, or local variables, the following
11534 special arguments are supported:
11538 Collect all registers.
11541 Collect all function arguments.
11544 Collect all local variables.
11547 Collect the return address. This is helpful if you want to see more
11551 Collects the number of arguments from the static probe at which the
11552 tracepoint is located.
11553 @xref{Static Probe Points}.
11555 @item $_probe_arg@var{n}
11556 @var{n} is an integer between 0 and 11. Collects the @var{n}th argument
11557 from the static probe at which the tracepoint is located.
11558 @xref{Static Probe Points}.
11561 @vindex $_sdata@r{, collect}
11562 Collect static tracepoint marker specific data. Only available for
11563 static tracepoints. @xref{Tracepoint Actions,,Tracepoint Action
11564 Lists}. On the UST static tracepoints library backend, an
11565 instrumentation point resembles a @code{printf} function call. The
11566 tracing library is able to collect user specified data formatted to a
11567 character string using the format provided by the programmer that
11568 instrumented the program. Other backends have similar mechanisms.
11569 Here's an example of a UST marker call:
11572 const char master_name[] = "$your_name";
11573 trace_mark(channel1, marker1, "hello %s", master_name)
11576 In this case, collecting @code{$_sdata} collects the string
11577 @samp{hello $yourname}. When analyzing the trace buffer, you can
11578 inspect @samp{$_sdata} like any other variable available to
11582 You can give several consecutive @code{collect} commands, each one
11583 with a single argument, or one @code{collect} command with several
11584 arguments separated by commas; the effect is the same.
11586 The optional @var{mods} changes the usual handling of the arguments.
11587 @code{s} requests that pointers to chars be handled as strings, in
11588 particular collecting the contents of the memory being pointed at, up
11589 to the first zero. The upper bound is by default the value of the
11590 @code{print elements} variable; if @code{s} is followed by a decimal
11591 number, that is the upper bound instead. So for instance
11592 @samp{collect/s25 mystr} collects as many as 25 characters at
11595 The command @code{info scope} (@pxref{Symbols, info scope}) is
11596 particularly useful for figuring out what data to collect.
11598 @kindex teval @r{(tracepoints)}
11599 @item teval @var{expr1}, @var{expr2}, @dots{}
11600 Evaluate the given expressions when the tracepoint is hit. This
11601 command accepts a comma-separated list of expressions. The results
11602 are discarded, so this is mainly useful for assigning values to trace
11603 state variables (@pxref{Trace State Variables}) without adding those
11604 values to the trace buffer, as would be the case if the @code{collect}
11607 @kindex while-stepping @r{(tracepoints)}
11608 @item while-stepping @var{n}
11609 Perform @var{n} single-step instruction traces after the tracepoint,
11610 collecting new data after each step. The @code{while-stepping}
11611 command is followed by the list of what to collect while stepping
11612 (followed by its own @code{end} command):
11615 > while-stepping 12
11616 > collect $regs, myglobal
11622 Note that @code{$pc} is not automatically collected by
11623 @code{while-stepping}; you need to explicitly collect that register if
11624 you need it. You may abbreviate @code{while-stepping} as @code{ws} or
11627 @item set default-collect @var{expr1}, @var{expr2}, @dots{}
11628 @kindex set default-collect
11629 @cindex default collection action
11630 This variable is a list of expressions to collect at each tracepoint
11631 hit. It is effectively an additional @code{collect} action prepended
11632 to every tracepoint action list. The expressions are parsed
11633 individually for each tracepoint, so for instance a variable named
11634 @code{xyz} may be interpreted as a global for one tracepoint, and a
11635 local for another, as appropriate to the tracepoint's location.
11637 @item show default-collect
11638 @kindex show default-collect
11639 Show the list of expressions that are collected by default at each
11644 @node Listing Tracepoints
11645 @subsection Listing Tracepoints
11648 @kindex info tracepoints @r{[}@var{n}@dots{}@r{]}
11649 @kindex info tp @r{[}@var{n}@dots{}@r{]}
11650 @cindex information about tracepoints
11651 @item info tracepoints @r{[}@var{num}@dots{}@r{]}
11652 Display information about the tracepoint @var{num}. If you don't
11653 specify a tracepoint number, displays information about all the
11654 tracepoints defined so far. The format is similar to that used for
11655 @code{info breakpoints}; in fact, @code{info tracepoints} is the same
11656 command, simply restricting itself to tracepoints.
11658 A tracepoint's listing may include additional information specific to
11663 its passcount as given by the @code{passcount @var{n}} command
11666 the state about installed on target of each location
11670 (@value{GDBP}) @b{info trace}
11671 Num Type Disp Enb Address What
11672 1 tracepoint keep y 0x0804ab57 in foo() at main.cxx:7
11674 collect globfoo, $regs
11679 2 tracepoint keep y <MULTIPLE>
11681 2.1 y 0x0804859c in func4 at change-loc.h:35
11682 installed on target
11683 2.2 y 0xb7ffc480 in func4 at change-loc.h:35
11684 installed on target
11685 2.3 y <PENDING> set_tracepoint
11686 3 tracepoint keep y 0x080485b1 in foo at change-loc.c:29
11687 not installed on target
11692 This command can be abbreviated @code{info tp}.
11695 @node Listing Static Tracepoint Markers
11696 @subsection Listing Static Tracepoint Markers
11699 @kindex info static-tracepoint-markers
11700 @cindex information about static tracepoint markers
11701 @item info static-tracepoint-markers
11702 Display information about all static tracepoint markers defined in the
11705 For each marker, the following columns are printed:
11709 An incrementing counter, output to help readability. This is not a
11712 The marker ID, as reported by the target.
11713 @item Enabled or Disabled
11714 Probed markers are tagged with @samp{y}. @samp{n} identifies marks
11715 that are not enabled.
11717 Where the marker is in your program, as a memory address.
11719 Where the marker is in the source for your program, as a file and line
11720 number. If the debug information included in the program does not
11721 allow @value{GDBN} to locate the source of the marker, this column
11722 will be left blank.
11726 In addition, the following information may be printed for each marker:
11730 User data passed to the tracing library by the marker call. In the
11731 UST backend, this is the format string passed as argument to the
11733 @item Static tracepoints probing the marker
11734 The list of static tracepoints attached to the marker.
11738 (@value{GDBP}) info static-tracepoint-markers
11739 Cnt ID Enb Address What
11740 1 ust/bar2 y 0x0000000000400e1a in main at stexample.c:25
11741 Data: number1 %d number2 %d
11742 Probed by static tracepoints: #2
11743 2 ust/bar33 n 0x0000000000400c87 in main at stexample.c:24
11749 @node Starting and Stopping Trace Experiments
11750 @subsection Starting and Stopping Trace Experiments
11753 @kindex tstart [ @var{notes} ]
11754 @cindex start a new trace experiment
11755 @cindex collected data discarded
11757 This command starts the trace experiment, and begins collecting data.
11758 It has the side effect of discarding all the data collected in the
11759 trace buffer during the previous trace experiment. If any arguments
11760 are supplied, they are taken as a note and stored with the trace
11761 experiment's state. The notes may be arbitrary text, and are
11762 especially useful with disconnected tracing in a multi-user context;
11763 the notes can explain what the trace is doing, supply user contact
11764 information, and so forth.
11766 @kindex tstop [ @var{notes} ]
11767 @cindex stop a running trace experiment
11769 This command stops the trace experiment. If any arguments are
11770 supplied, they are recorded with the experiment as a note. This is
11771 useful if you are stopping a trace started by someone else, for
11772 instance if the trace is interfering with the system's behavior and
11773 needs to be stopped quickly.
11775 @strong{Note}: a trace experiment and data collection may stop
11776 automatically if any tracepoint's passcount is reached
11777 (@pxref{Tracepoint Passcounts}), or if the trace buffer becomes full.
11780 @cindex status of trace data collection
11781 @cindex trace experiment, status of
11783 This command displays the status of the current trace data
11787 Here is an example of the commands we described so far:
11790 (@value{GDBP}) @b{trace gdb_c_test}
11791 (@value{GDBP}) @b{actions}
11792 Enter actions for tracepoint #1, one per line.
11793 > collect $regs,$locals,$args
11794 > while-stepping 11
11798 (@value{GDBP}) @b{tstart}
11799 [time passes @dots{}]
11800 (@value{GDBP}) @b{tstop}
11803 @anchor{disconnected tracing}
11804 @cindex disconnected tracing
11805 You can choose to continue running the trace experiment even if
11806 @value{GDBN} disconnects from the target, voluntarily or
11807 involuntarily. For commands such as @code{detach}, the debugger will
11808 ask what you want to do with the trace. But for unexpected
11809 terminations (@value{GDBN} crash, network outage), it would be
11810 unfortunate to lose hard-won trace data, so the variable
11811 @code{disconnected-tracing} lets you decide whether the trace should
11812 continue running without @value{GDBN}.
11815 @item set disconnected-tracing on
11816 @itemx set disconnected-tracing off
11817 @kindex set disconnected-tracing
11818 Choose whether a tracing run should continue to run if @value{GDBN}
11819 has disconnected from the target. Note that @code{detach} or
11820 @code{quit} will ask you directly what to do about a running trace no
11821 matter what this variable's setting, so the variable is mainly useful
11822 for handling unexpected situations, such as loss of the network.
11824 @item show disconnected-tracing
11825 @kindex show disconnected-tracing
11826 Show the current choice for disconnected tracing.
11830 When you reconnect to the target, the trace experiment may or may not
11831 still be running; it might have filled the trace buffer in the
11832 meantime, or stopped for one of the other reasons. If it is running,
11833 it will continue after reconnection.
11835 Upon reconnection, the target will upload information about the
11836 tracepoints in effect. @value{GDBN} will then compare that
11837 information to the set of tracepoints currently defined, and attempt
11838 to match them up, allowing for the possibility that the numbers may
11839 have changed due to creation and deletion in the meantime. If one of
11840 the target's tracepoints does not match any in @value{GDBN}, the
11841 debugger will create a new tracepoint, so that you have a number with
11842 which to specify that tracepoint. This matching-up process is
11843 necessarily heuristic, and it may result in useless tracepoints being
11844 created; you may simply delete them if they are of no use.
11846 @cindex circular trace buffer
11847 If your target agent supports a @dfn{circular trace buffer}, then you
11848 can run a trace experiment indefinitely without filling the trace
11849 buffer; when space runs out, the agent deletes already-collected trace
11850 frames, oldest first, until there is enough room to continue
11851 collecting. This is especially useful if your tracepoints are being
11852 hit too often, and your trace gets terminated prematurely because the
11853 buffer is full. To ask for a circular trace buffer, simply set
11854 @samp{circular-trace-buffer} to on. You can set this at any time,
11855 including during tracing; if the agent can do it, it will change
11856 buffer handling on the fly, otherwise it will not take effect until
11860 @item set circular-trace-buffer on
11861 @itemx set circular-trace-buffer off
11862 @kindex set circular-trace-buffer
11863 Choose whether a tracing run should use a linear or circular buffer
11864 for trace data. A linear buffer will not lose any trace data, but may
11865 fill up prematurely, while a circular buffer will discard old trace
11866 data, but it will have always room for the latest tracepoint hits.
11868 @item show circular-trace-buffer
11869 @kindex show circular-trace-buffer
11870 Show the current choice for the trace buffer. Note that this may not
11871 match the agent's current buffer handling, nor is it guaranteed to
11872 match the setting that might have been in effect during a past run,
11873 for instance if you are looking at frames from a trace file.
11878 @item set trace-buffer-size @var{n}
11879 @kindex set trace-buffer-size
11880 Request that the target use a trace buffer of @var{n} bytes. Not all
11881 targets will honor the request; they may have a compiled-in size for
11882 the trace buffer, or some other limitation. Set to a value of
11883 @code{-1} to let the target use whatever size it likes. This is also
11886 @item show trace-buffer-size
11887 @kindex show trace-buffer-size
11888 Show the current requested size for the trace buffer. Note that this
11889 will only match the actual size if the target supports size-setting,
11890 and was able to handle the requested size. For instance, if the
11891 target can only change buffer size between runs, this variable will
11892 not reflect the change until the next run starts. Use @code{tstatus}
11893 to get a report of the actual buffer size.
11897 @item set trace-user @var{text}
11898 @kindex set trace-user
11900 @item show trace-user
11901 @kindex show trace-user
11903 @item set trace-notes @var{text}
11904 @kindex set trace-notes
11905 Set the trace run's notes.
11907 @item show trace-notes
11908 @kindex show trace-notes
11909 Show the trace run's notes.
11911 @item set trace-stop-notes @var{text}
11912 @kindex set trace-stop-notes
11913 Set the trace run's stop notes. The handling of the note is as for
11914 @code{tstop} arguments; the set command is convenient way to fix a
11915 stop note that is mistaken or incomplete.
11917 @item show trace-stop-notes
11918 @kindex show trace-stop-notes
11919 Show the trace run's stop notes.
11923 @node Tracepoint Restrictions
11924 @subsection Tracepoint Restrictions
11926 @cindex tracepoint restrictions
11927 There are a number of restrictions on the use of tracepoints. As
11928 described above, tracepoint data gathering occurs on the target
11929 without interaction from @value{GDBN}. Thus the full capabilities of
11930 the debugger are not available during data gathering, and then at data
11931 examination time, you will be limited by only having what was
11932 collected. The following items describe some common problems, but it
11933 is not exhaustive, and you may run into additional difficulties not
11939 Tracepoint expressions are intended to gather objects (lvalues). Thus
11940 the full flexibility of GDB's expression evaluator is not available.
11941 You cannot call functions, cast objects to aggregate types, access
11942 convenience variables or modify values (except by assignment to trace
11943 state variables). Some language features may implicitly call
11944 functions (for instance Objective-C fields with accessors), and therefore
11945 cannot be collected either.
11948 Collection of local variables, either individually or in bulk with
11949 @code{$locals} or @code{$args}, during @code{while-stepping} may
11950 behave erratically. The stepping action may enter a new scope (for
11951 instance by stepping into a function), or the location of the variable
11952 may change (for instance it is loaded into a register). The
11953 tracepoint data recorded uses the location information for the
11954 variables that is correct for the tracepoint location. When the
11955 tracepoint is created, it is not possible, in general, to determine
11956 where the steps of a @code{while-stepping} sequence will advance the
11957 program---particularly if a conditional branch is stepped.
11960 Collection of an incompletely-initialized or partially-destroyed object
11961 may result in something that @value{GDBN} cannot display, or displays
11962 in a misleading way.
11965 When @value{GDBN} displays a pointer to character it automatically
11966 dereferences the pointer to also display characters of the string
11967 being pointed to. However, collecting the pointer during tracing does
11968 not automatically collect the string. You need to explicitly
11969 dereference the pointer and provide size information if you want to
11970 collect not only the pointer, but the memory pointed to. For example,
11971 @code{*ptr@@50} can be used to collect the 50 element array pointed to
11975 It is not possible to collect a complete stack backtrace at a
11976 tracepoint. Instead, you may collect the registers and a few hundred
11977 bytes from the stack pointer with something like @code{*(unsigned char *)$esp@@300}
11978 (adjust to use the name of the actual stack pointer register on your
11979 target architecture, and the amount of stack you wish to capture).
11980 Then the @code{backtrace} command will show a partial backtrace when
11981 using a trace frame. The number of stack frames that can be examined
11982 depends on the sizes of the frames in the collected stack. Note that
11983 if you ask for a block so large that it goes past the bottom of the
11984 stack, the target agent may report an error trying to read from an
11988 If you do not collect registers at a tracepoint, @value{GDBN} can
11989 infer that the value of @code{$pc} must be the same as the address of
11990 the tracepoint and use that when you are looking at a trace frame
11991 for that tracepoint. However, this cannot work if the tracepoint has
11992 multiple locations (for instance if it was set in a function that was
11993 inlined), or if it has a @code{while-stepping} loop. In those cases
11994 @value{GDBN} will warn you that it can't infer @code{$pc}, and default
11999 @node Analyze Collected Data
12000 @section Using the Collected Data
12002 After the tracepoint experiment ends, you use @value{GDBN} commands
12003 for examining the trace data. The basic idea is that each tracepoint
12004 collects a trace @dfn{snapshot} every time it is hit and another
12005 snapshot every time it single-steps. All these snapshots are
12006 consecutively numbered from zero and go into a buffer, and you can
12007 examine them later. The way you examine them is to @dfn{focus} on a
12008 specific trace snapshot. When the remote stub is focused on a trace
12009 snapshot, it will respond to all @value{GDBN} requests for memory and
12010 registers by reading from the buffer which belongs to that snapshot,
12011 rather than from @emph{real} memory or registers of the program being
12012 debugged. This means that @strong{all} @value{GDBN} commands
12013 (@code{print}, @code{info registers}, @code{backtrace}, etc.) will
12014 behave as if we were currently debugging the program state as it was
12015 when the tracepoint occurred. Any requests for data that are not in
12016 the buffer will fail.
12019 * tfind:: How to select a trace snapshot
12020 * tdump:: How to display all data for a snapshot
12021 * save tracepoints:: How to save tracepoints for a future run
12025 @subsection @code{tfind @var{n}}
12028 @cindex select trace snapshot
12029 @cindex find trace snapshot
12030 The basic command for selecting a trace snapshot from the buffer is
12031 @code{tfind @var{n}}, which finds trace snapshot number @var{n},
12032 counting from zero. If no argument @var{n} is given, the next
12033 snapshot is selected.
12035 Here are the various forms of using the @code{tfind} command.
12039 Find the first snapshot in the buffer. This is a synonym for
12040 @code{tfind 0} (since 0 is the number of the first snapshot).
12043 Stop debugging trace snapshots, resume @emph{live} debugging.
12046 Same as @samp{tfind none}.
12049 No argument means find the next trace snapshot.
12052 Find the previous trace snapshot before the current one. This permits
12053 retracing earlier steps.
12055 @item tfind tracepoint @var{num}
12056 Find the next snapshot associated with tracepoint @var{num}. Search
12057 proceeds forward from the last examined trace snapshot. If no
12058 argument @var{num} is given, it means find the next snapshot collected
12059 for the same tracepoint as the current snapshot.
12061 @item tfind pc @var{addr}
12062 Find the next snapshot associated with the value @var{addr} of the
12063 program counter. Search proceeds forward from the last examined trace
12064 snapshot. If no argument @var{addr} is given, it means find the next
12065 snapshot with the same value of PC as the current snapshot.
12067 @item tfind outside @var{addr1}, @var{addr2}
12068 Find the next snapshot whose PC is outside the given range of
12069 addresses (exclusive).
12071 @item tfind range @var{addr1}, @var{addr2}
12072 Find the next snapshot whose PC is between @var{addr1} and
12073 @var{addr2} (inclusive).
12075 @item tfind line @r{[}@var{file}:@r{]}@var{n}
12076 Find the next snapshot associated with the source line @var{n}. If
12077 the optional argument @var{file} is given, refer to line @var{n} in
12078 that source file. Search proceeds forward from the last examined
12079 trace snapshot. If no argument @var{n} is given, it means find the
12080 next line other than the one currently being examined; thus saying
12081 @code{tfind line} repeatedly can appear to have the same effect as
12082 stepping from line to line in a @emph{live} debugging session.
12085 The default arguments for the @code{tfind} commands are specifically
12086 designed to make it easy to scan through the trace buffer. For
12087 instance, @code{tfind} with no argument selects the next trace
12088 snapshot, and @code{tfind -} with no argument selects the previous
12089 trace snapshot. So, by giving one @code{tfind} command, and then
12090 simply hitting @key{RET} repeatedly you can examine all the trace
12091 snapshots in order. Or, by saying @code{tfind -} and then hitting
12092 @key{RET} repeatedly you can examine the snapshots in reverse order.
12093 The @code{tfind line} command with no argument selects the snapshot
12094 for the next source line executed. The @code{tfind pc} command with
12095 no argument selects the next snapshot with the same program counter
12096 (PC) as the current frame. The @code{tfind tracepoint} command with
12097 no argument selects the next trace snapshot collected by the same
12098 tracepoint as the current one.
12100 In addition to letting you scan through the trace buffer manually,
12101 these commands make it easy to construct @value{GDBN} scripts that
12102 scan through the trace buffer and print out whatever collected data
12103 you are interested in. Thus, if we want to examine the PC, FP, and SP
12104 registers from each trace frame in the buffer, we can say this:
12107 (@value{GDBP}) @b{tfind start}
12108 (@value{GDBP}) @b{while ($trace_frame != -1)}
12109 > printf "Frame %d, PC = %08X, SP = %08X, FP = %08X\n", \
12110 $trace_frame, $pc, $sp, $fp
12114 Frame 0, PC = 0020DC64, SP = 0030BF3C, FP = 0030BF44
12115 Frame 1, PC = 0020DC6C, SP = 0030BF38, FP = 0030BF44
12116 Frame 2, PC = 0020DC70, SP = 0030BF34, FP = 0030BF44
12117 Frame 3, PC = 0020DC74, SP = 0030BF30, FP = 0030BF44
12118 Frame 4, PC = 0020DC78, SP = 0030BF2C, FP = 0030BF44
12119 Frame 5, PC = 0020DC7C, SP = 0030BF28, FP = 0030BF44
12120 Frame 6, PC = 0020DC80, SP = 0030BF24, FP = 0030BF44
12121 Frame 7, PC = 0020DC84, SP = 0030BF20, FP = 0030BF44
12122 Frame 8, PC = 0020DC88, SP = 0030BF1C, FP = 0030BF44
12123 Frame 9, PC = 0020DC8E, SP = 0030BF18, FP = 0030BF44
12124 Frame 10, PC = 00203F6C, SP = 0030BE3C, FP = 0030BF14
12127 Or, if we want to examine the variable @code{X} at each source line in
12131 (@value{GDBP}) @b{tfind start}
12132 (@value{GDBP}) @b{while ($trace_frame != -1)}
12133 > printf "Frame %d, X == %d\n", $trace_frame, X
12143 @subsection @code{tdump}
12145 @cindex dump all data collected at tracepoint
12146 @cindex tracepoint data, display
12148 This command takes no arguments. It prints all the data collected at
12149 the current trace snapshot.
12152 (@value{GDBP}) @b{trace 444}
12153 (@value{GDBP}) @b{actions}
12154 Enter actions for tracepoint #2, one per line:
12155 > collect $regs, $locals, $args, gdb_long_test
12158 (@value{GDBP}) @b{tstart}
12160 (@value{GDBP}) @b{tfind line 444}
12161 #0 gdb_test (p1=0x11, p2=0x22, p3=0x33, p4=0x44, p5=0x55, p6=0x66)
12163 444 printp( "%s: arguments = 0x%X 0x%X 0x%X 0x%X 0x%X 0x%X\n", )
12165 (@value{GDBP}) @b{tdump}
12166 Data collected at tracepoint 2, trace frame 1:
12167 d0 0xc4aa0085 -995491707
12171 d4 0x71aea3d 119204413
12174 d7 0x380035 3670069
12175 a0 0x19e24a 1696330
12176 a1 0x3000668 50333288
12178 a3 0x322000 3284992
12179 a4 0x3000698 50333336
12180 a5 0x1ad3cc 1758156
12181 fp 0x30bf3c 0x30bf3c
12182 sp 0x30bf34 0x30bf34
12184 pc 0x20b2c8 0x20b2c8
12188 p = 0x20e5b4 "gdb-test"
12195 gdb_long_test = 17 '\021'
12200 @code{tdump} works by scanning the tracepoint's current collection
12201 actions and printing the value of each expression listed. So
12202 @code{tdump} can fail, if after a run, you change the tracepoint's
12203 actions to mention variables that were not collected during the run.
12205 Also, for tracepoints with @code{while-stepping} loops, @code{tdump}
12206 uses the collected value of @code{$pc} to distinguish between trace
12207 frames that were collected at the tracepoint hit, and frames that were
12208 collected while stepping. This allows it to correctly choose whether
12209 to display the basic list of collections, or the collections from the
12210 body of the while-stepping loop. However, if @code{$pc} was not collected,
12211 then @code{tdump} will always attempt to dump using the basic collection
12212 list, and may fail if a while-stepping frame does not include all the
12213 same data that is collected at the tracepoint hit.
12214 @c This is getting pretty arcane, example would be good.
12216 @node save tracepoints
12217 @subsection @code{save tracepoints @var{filename}}
12218 @kindex save tracepoints
12219 @kindex save-tracepoints
12220 @cindex save tracepoints for future sessions
12222 This command saves all current tracepoint definitions together with
12223 their actions and passcounts, into a file @file{@var{filename}}
12224 suitable for use in a later debugging session. To read the saved
12225 tracepoint definitions, use the @code{source} command (@pxref{Command
12226 Files}). The @w{@code{save-tracepoints}} command is a deprecated
12227 alias for @w{@code{save tracepoints}}
12229 @node Tracepoint Variables
12230 @section Convenience Variables for Tracepoints
12231 @cindex tracepoint variables
12232 @cindex convenience variables for tracepoints
12235 @vindex $trace_frame
12236 @item (int) $trace_frame
12237 The current trace snapshot (a.k.a.@: @dfn{frame}) number, or -1 if no
12238 snapshot is selected.
12240 @vindex $tracepoint
12241 @item (int) $tracepoint
12242 The tracepoint for the current trace snapshot.
12244 @vindex $trace_line
12245 @item (int) $trace_line
12246 The line number for the current trace snapshot.
12248 @vindex $trace_file
12249 @item (char []) $trace_file
12250 The source file for the current trace snapshot.
12252 @vindex $trace_func
12253 @item (char []) $trace_func
12254 The name of the function containing @code{$tracepoint}.
12257 Note: @code{$trace_file} is not suitable for use in @code{printf},
12258 use @code{output} instead.
12260 Here's a simple example of using these convenience variables for
12261 stepping through all the trace snapshots and printing some of their
12262 data. Note that these are not the same as trace state variables,
12263 which are managed by the target.
12266 (@value{GDBP}) @b{tfind start}
12268 (@value{GDBP}) @b{while $trace_frame != -1}
12269 > output $trace_file
12270 > printf ", line %d (tracepoint #%d)\n", $trace_line, $tracepoint
12276 @section Using Trace Files
12277 @cindex trace files
12279 In some situations, the target running a trace experiment may no
12280 longer be available; perhaps it crashed, or the hardware was needed
12281 for a different activity. To handle these cases, you can arrange to
12282 dump the trace data into a file, and later use that file as a source
12283 of trace data, via the @code{target tfile} command.
12288 @item tsave [ -r ] @var{filename}
12289 Save the trace data to @var{filename}. By default, this command
12290 assumes that @var{filename} refers to the host filesystem, so if
12291 necessary @value{GDBN} will copy raw trace data up from the target and
12292 then save it. If the target supports it, you can also supply the
12293 optional argument @code{-r} (``remote'') to direct the target to save
12294 the data directly into @var{filename} in its own filesystem, which may be
12295 more efficient if the trace buffer is very large. (Note, however, that
12296 @code{target tfile} can only read from files accessible to the host.)
12298 @kindex target tfile
12300 @item target tfile @var{filename}
12301 Use the file named @var{filename} as a source of trace data. Commands
12302 that examine data work as they do with a live target, but it is not
12303 possible to run any new trace experiments. @code{tstatus} will report
12304 the state of the trace run at the moment the data was saved, as well
12305 as the current trace frame you are examining. @var{filename} must be
12306 on a filesystem accessible to the host.
12311 @chapter Debugging Programs That Use Overlays
12314 If your program is too large to fit completely in your target system's
12315 memory, you can sometimes use @dfn{overlays} to work around this
12316 problem. @value{GDBN} provides some support for debugging programs that
12320 * How Overlays Work:: A general explanation of overlays.
12321 * Overlay Commands:: Managing overlays in @value{GDBN}.
12322 * Automatic Overlay Debugging:: @value{GDBN} can find out which overlays are
12323 mapped by asking the inferior.
12324 * Overlay Sample Program:: A sample program using overlays.
12327 @node How Overlays Work
12328 @section How Overlays Work
12329 @cindex mapped overlays
12330 @cindex unmapped overlays
12331 @cindex load address, overlay's
12332 @cindex mapped address
12333 @cindex overlay area
12335 Suppose you have a computer whose instruction address space is only 64
12336 kilobytes long, but which has much more memory which can be accessed by
12337 other means: special instructions, segment registers, or memory
12338 management hardware, for example. Suppose further that you want to
12339 adapt a program which is larger than 64 kilobytes to run on this system.
12341 One solution is to identify modules of your program which are relatively
12342 independent, and need not call each other directly; call these modules
12343 @dfn{overlays}. Separate the overlays from the main program, and place
12344 their machine code in the larger memory. Place your main program in
12345 instruction memory, but leave at least enough space there to hold the
12346 largest overlay as well.
12348 Now, to call a function located in an overlay, you must first copy that
12349 overlay's machine code from the large memory into the space set aside
12350 for it in the instruction memory, and then jump to its entry point
12353 @c NB: In the below the mapped area's size is greater or equal to the
12354 @c size of all overlays. This is intentional to remind the developer
12355 @c that overlays don't necessarily need to be the same size.
12359 Data Instruction Larger
12360 Address Space Address Space Address Space
12361 +-----------+ +-----------+ +-----------+
12363 +-----------+ +-----------+ +-----------+<-- overlay 1
12364 | program | | main | .----| overlay 1 | load address
12365 | variables | | program | | +-----------+
12366 | and heap | | | | | |
12367 +-----------+ | | | +-----------+<-- overlay 2
12368 | | +-----------+ | | | load address
12369 +-----------+ | | | .-| overlay 2 |
12371 mapped --->+-----------+ | | +-----------+
12372 address | | | | | |
12373 | overlay | <-' | | |
12374 | area | <---' +-----------+<-- overlay 3
12375 | | <---. | | load address
12376 +-----------+ `--| overlay 3 |
12383 @anchor{A code overlay}A code overlay
12387 The diagram (@pxref{A code overlay}) shows a system with separate data
12388 and instruction address spaces. To map an overlay, the program copies
12389 its code from the larger address space to the instruction address space.
12390 Since the overlays shown here all use the same mapped address, only one
12391 may be mapped at a time. For a system with a single address space for
12392 data and instructions, the diagram would be similar, except that the
12393 program variables and heap would share an address space with the main
12394 program and the overlay area.
12396 An overlay loaded into instruction memory and ready for use is called a
12397 @dfn{mapped} overlay; its @dfn{mapped address} is its address in the
12398 instruction memory. An overlay not present (or only partially present)
12399 in instruction memory is called @dfn{unmapped}; its @dfn{load address}
12400 is its address in the larger memory. The mapped address is also called
12401 the @dfn{virtual memory address}, or @dfn{VMA}; the load address is also
12402 called the @dfn{load memory address}, or @dfn{LMA}.
12404 Unfortunately, overlays are not a completely transparent way to adapt a
12405 program to limited instruction memory. They introduce a new set of
12406 global constraints you must keep in mind as you design your program:
12411 Before calling or returning to a function in an overlay, your program
12412 must make sure that overlay is actually mapped. Otherwise, the call or
12413 return will transfer control to the right address, but in the wrong
12414 overlay, and your program will probably crash.
12417 If the process of mapping an overlay is expensive on your system, you
12418 will need to choose your overlays carefully to minimize their effect on
12419 your program's performance.
12422 The executable file you load onto your system must contain each
12423 overlay's instructions, appearing at the overlay's load address, not its
12424 mapped address. However, each overlay's instructions must be relocated
12425 and its symbols defined as if the overlay were at its mapped address.
12426 You can use GNU linker scripts to specify different load and relocation
12427 addresses for pieces of your program; see @ref{Overlay Description,,,
12428 ld.info, Using ld: the GNU linker}.
12431 The procedure for loading executable files onto your system must be able
12432 to load their contents into the larger address space as well as the
12433 instruction and data spaces.
12437 The overlay system described above is rather simple, and could be
12438 improved in many ways:
12443 If your system has suitable bank switch registers or memory management
12444 hardware, you could use those facilities to make an overlay's load area
12445 contents simply appear at their mapped address in instruction space.
12446 This would probably be faster than copying the overlay to its mapped
12447 area in the usual way.
12450 If your overlays are small enough, you could set aside more than one
12451 overlay area, and have more than one overlay mapped at a time.
12454 You can use overlays to manage data, as well as instructions. In
12455 general, data overlays are even less transparent to your design than
12456 code overlays: whereas code overlays only require care when you call or
12457 return to functions, data overlays require care every time you access
12458 the data. Also, if you change the contents of a data overlay, you
12459 must copy its contents back out to its load address before you can copy a
12460 different data overlay into the same mapped area.
12465 @node Overlay Commands
12466 @section Overlay Commands
12468 To use @value{GDBN}'s overlay support, each overlay in your program must
12469 correspond to a separate section of the executable file. The section's
12470 virtual memory address and load memory address must be the overlay's
12471 mapped and load addresses. Identifying overlays with sections allows
12472 @value{GDBN} to determine the appropriate address of a function or
12473 variable, depending on whether the overlay is mapped or not.
12475 @value{GDBN}'s overlay commands all start with the word @code{overlay};
12476 you can abbreviate this as @code{ov} or @code{ovly}. The commands are:
12481 Disable @value{GDBN}'s overlay support. When overlay support is
12482 disabled, @value{GDBN} assumes that all functions and variables are
12483 always present at their mapped addresses. By default, @value{GDBN}'s
12484 overlay support is disabled.
12486 @item overlay manual
12487 @cindex manual overlay debugging
12488 Enable @dfn{manual} overlay debugging. In this mode, @value{GDBN}
12489 relies on you to tell it which overlays are mapped, and which are not,
12490 using the @code{overlay map-overlay} and @code{overlay unmap-overlay}
12491 commands described below.
12493 @item overlay map-overlay @var{overlay}
12494 @itemx overlay map @var{overlay}
12495 @cindex map an overlay
12496 Tell @value{GDBN} that @var{overlay} is now mapped; @var{overlay} must
12497 be the name of the object file section containing the overlay. When an
12498 overlay is mapped, @value{GDBN} assumes it can find the overlay's
12499 functions and variables at their mapped addresses. @value{GDBN} assumes
12500 that any other overlays whose mapped ranges overlap that of
12501 @var{overlay} are now unmapped.
12503 @item overlay unmap-overlay @var{overlay}
12504 @itemx overlay unmap @var{overlay}
12505 @cindex unmap an overlay
12506 Tell @value{GDBN} that @var{overlay} is no longer mapped; @var{overlay}
12507 must be the name of the object file section containing the overlay.
12508 When an overlay is unmapped, @value{GDBN} assumes it can find the
12509 overlay's functions and variables at their load addresses.
12512 Enable @dfn{automatic} overlay debugging. In this mode, @value{GDBN}
12513 consults a data structure the overlay manager maintains in the inferior
12514 to see which overlays are mapped. For details, see @ref{Automatic
12515 Overlay Debugging}.
12517 @item overlay load-target
12518 @itemx overlay load
12519 @cindex reloading the overlay table
12520 Re-read the overlay table from the inferior. Normally, @value{GDBN}
12521 re-reads the table @value{GDBN} automatically each time the inferior
12522 stops, so this command should only be necessary if you have changed the
12523 overlay mapping yourself using @value{GDBN}. This command is only
12524 useful when using automatic overlay debugging.
12526 @item overlay list-overlays
12527 @itemx overlay list
12528 @cindex listing mapped overlays
12529 Display a list of the overlays currently mapped, along with their mapped
12530 addresses, load addresses, and sizes.
12534 Normally, when @value{GDBN} prints a code address, it includes the name
12535 of the function the address falls in:
12538 (@value{GDBP}) print main
12539 $3 = @{int ()@} 0x11a0 <main>
12542 When overlay debugging is enabled, @value{GDBN} recognizes code in
12543 unmapped overlays, and prints the names of unmapped functions with
12544 asterisks around them. For example, if @code{foo} is a function in an
12545 unmapped overlay, @value{GDBN} prints it this way:
12548 (@value{GDBP}) overlay list
12549 No sections are mapped.
12550 (@value{GDBP}) print foo
12551 $5 = @{int (int)@} 0x100000 <*foo*>
12554 When @code{foo}'s overlay is mapped, @value{GDBN} prints the function's
12558 (@value{GDBP}) overlay list
12559 Section .ov.foo.text, loaded at 0x100000 - 0x100034,
12560 mapped at 0x1016 - 0x104a
12561 (@value{GDBP}) print foo
12562 $6 = @{int (int)@} 0x1016 <foo>
12565 When overlay debugging is enabled, @value{GDBN} can find the correct
12566 address for functions and variables in an overlay, whether or not the
12567 overlay is mapped. This allows most @value{GDBN} commands, like
12568 @code{break} and @code{disassemble}, to work normally, even on unmapped
12569 code. However, @value{GDBN}'s breakpoint support has some limitations:
12573 @cindex breakpoints in overlays
12574 @cindex overlays, setting breakpoints in
12575 You can set breakpoints in functions in unmapped overlays, as long as
12576 @value{GDBN} can write to the overlay at its load address.
12578 @value{GDBN} can not set hardware or simulator-based breakpoints in
12579 unmapped overlays. However, if you set a breakpoint at the end of your
12580 overlay manager (and tell @value{GDBN} which overlays are now mapped, if
12581 you are using manual overlay management), @value{GDBN} will re-set its
12582 breakpoints properly.
12586 @node Automatic Overlay Debugging
12587 @section Automatic Overlay Debugging
12588 @cindex automatic overlay debugging
12590 @value{GDBN} can automatically track which overlays are mapped and which
12591 are not, given some simple co-operation from the overlay manager in the
12592 inferior. If you enable automatic overlay debugging with the
12593 @code{overlay auto} command (@pxref{Overlay Commands}), @value{GDBN}
12594 looks in the inferior's memory for certain variables describing the
12595 current state of the overlays.
12597 Here are the variables your overlay manager must define to support
12598 @value{GDBN}'s automatic overlay debugging:
12602 @item @code{_ovly_table}:
12603 This variable must be an array of the following structures:
12608 /* The overlay's mapped address. */
12611 /* The size of the overlay, in bytes. */
12612 unsigned long size;
12614 /* The overlay's load address. */
12617 /* Non-zero if the overlay is currently mapped;
12619 unsigned long mapped;
12623 @item @code{_novlys}:
12624 This variable must be a four-byte signed integer, holding the total
12625 number of elements in @code{_ovly_table}.
12629 To decide whether a particular overlay is mapped or not, @value{GDBN}
12630 looks for an entry in @w{@code{_ovly_table}} whose @code{vma} and
12631 @code{lma} members equal the VMA and LMA of the overlay's section in the
12632 executable file. When @value{GDBN} finds a matching entry, it consults
12633 the entry's @code{mapped} member to determine whether the overlay is
12636 In addition, your overlay manager may define a function called
12637 @code{_ovly_debug_event}. If this function is defined, @value{GDBN}
12638 will silently set a breakpoint there. If the overlay manager then
12639 calls this function whenever it has changed the overlay table, this
12640 will enable @value{GDBN} to accurately keep track of which overlays
12641 are in program memory, and update any breakpoints that may be set
12642 in overlays. This will allow breakpoints to work even if the
12643 overlays are kept in ROM or other non-writable memory while they
12644 are not being executed.
12646 @node Overlay Sample Program
12647 @section Overlay Sample Program
12648 @cindex overlay example program
12650 When linking a program which uses overlays, you must place the overlays
12651 at their load addresses, while relocating them to run at their mapped
12652 addresses. To do this, you must write a linker script (@pxref{Overlay
12653 Description,,, ld.info, Using ld: the GNU linker}). Unfortunately,
12654 since linker scripts are specific to a particular host system, target
12655 architecture, and target memory layout, this manual cannot provide
12656 portable sample code demonstrating @value{GDBN}'s overlay support.
12658 However, the @value{GDBN} source distribution does contain an overlaid
12659 program, with linker scripts for a few systems, as part of its test
12660 suite. The program consists of the following files from
12661 @file{gdb/testsuite/gdb.base}:
12665 The main program file.
12667 A simple overlay manager, used by @file{overlays.c}.
12672 Overlay modules, loaded and used by @file{overlays.c}.
12675 Linker scripts for linking the test program on the @code{d10v-elf}
12676 and @code{m32r-elf} targets.
12679 You can build the test program using the @code{d10v-elf} GCC
12680 cross-compiler like this:
12683 $ d10v-elf-gcc -g -c overlays.c
12684 $ d10v-elf-gcc -g -c ovlymgr.c
12685 $ d10v-elf-gcc -g -c foo.c
12686 $ d10v-elf-gcc -g -c bar.c
12687 $ d10v-elf-gcc -g -c baz.c
12688 $ d10v-elf-gcc -g -c grbx.c
12689 $ d10v-elf-gcc -g overlays.o ovlymgr.o foo.o bar.o \
12690 baz.o grbx.o -Wl,-Td10v.ld -o overlays
12693 The build process is identical for any other architecture, except that
12694 you must substitute the appropriate compiler and linker script for the
12695 target system for @code{d10v-elf-gcc} and @code{d10v.ld}.
12699 @chapter Using @value{GDBN} with Different Languages
12702 Although programming languages generally have common aspects, they are
12703 rarely expressed in the same manner. For instance, in ANSI C,
12704 dereferencing a pointer @code{p} is accomplished by @code{*p}, but in
12705 Modula-2, it is accomplished by @code{p^}. Values can also be
12706 represented (and displayed) differently. Hex numbers in C appear as
12707 @samp{0x1ae}, while in Modula-2 they appear as @samp{1AEH}.
12709 @cindex working language
12710 Language-specific information is built into @value{GDBN} for some languages,
12711 allowing you to express operations like the above in your program's
12712 native language, and allowing @value{GDBN} to output values in a manner
12713 consistent with the syntax of your program's native language. The
12714 language you use to build expressions is called the @dfn{working
12718 * Setting:: Switching between source languages
12719 * Show:: Displaying the language
12720 * Checks:: Type and range checks
12721 * Supported Languages:: Supported languages
12722 * Unsupported Languages:: Unsupported languages
12726 @section Switching Between Source Languages
12728 There are two ways to control the working language---either have @value{GDBN}
12729 set it automatically, or select it manually yourself. You can use the
12730 @code{set language} command for either purpose. On startup, @value{GDBN}
12731 defaults to setting the language automatically. The working language is
12732 used to determine how expressions you type are interpreted, how values
12735 In addition to the working language, every source file that
12736 @value{GDBN} knows about has its own working language. For some object
12737 file formats, the compiler might indicate which language a particular
12738 source file is in. However, most of the time @value{GDBN} infers the
12739 language from the name of the file. The language of a source file
12740 controls whether C@t{++} names are demangled---this way @code{backtrace} can
12741 show each frame appropriately for its own language. There is no way to
12742 set the language of a source file from within @value{GDBN}, but you can
12743 set the language associated with a filename extension. @xref{Show, ,
12744 Displaying the Language}.
12746 This is most commonly a problem when you use a program, such
12747 as @code{cfront} or @code{f2c}, that generates C but is written in
12748 another language. In that case, make the
12749 program use @code{#line} directives in its C output; that way
12750 @value{GDBN} will know the correct language of the source code of the original
12751 program, and will display that source code, not the generated C code.
12754 * Filenames:: Filename extensions and languages.
12755 * Manually:: Setting the working language manually
12756 * Automatically:: Having @value{GDBN} infer the source language
12760 @subsection List of Filename Extensions and Languages
12762 If a source file name ends in one of the following extensions, then
12763 @value{GDBN} infers that its language is the one indicated.
12781 C@t{++} source file
12787 Objective-C source file
12791 Fortran source file
12794 Modula-2 source file
12798 Assembler source file. This actually behaves almost like C, but
12799 @value{GDBN} does not skip over function prologues when stepping.
12802 In addition, you may set the language associated with a filename
12803 extension. @xref{Show, , Displaying the Language}.
12806 @subsection Setting the Working Language
12808 If you allow @value{GDBN} to set the language automatically,
12809 expressions are interpreted the same way in your debugging session and
12812 @kindex set language
12813 If you wish, you may set the language manually. To do this, issue the
12814 command @samp{set language @var{lang}}, where @var{lang} is the name of
12815 a language, such as
12816 @code{c} or @code{modula-2}.
12817 For a list of the supported languages, type @samp{set language}.
12819 Setting the language manually prevents @value{GDBN} from updating the working
12820 language automatically. This can lead to confusion if you try
12821 to debug a program when the working language is not the same as the
12822 source language, when an expression is acceptable to both
12823 languages---but means different things. For instance, if the current
12824 source file were written in C, and @value{GDBN} was parsing Modula-2, a
12832 might not have the effect you intended. In C, this means to add
12833 @code{b} and @code{c} and place the result in @code{a}. The result
12834 printed would be the value of @code{a}. In Modula-2, this means to compare
12835 @code{a} to the result of @code{b+c}, yielding a @code{BOOLEAN} value.
12837 @node Automatically
12838 @subsection Having @value{GDBN} Infer the Source Language
12840 To have @value{GDBN} set the working language automatically, use
12841 @samp{set language local} or @samp{set language auto}. @value{GDBN}
12842 then infers the working language. That is, when your program stops in a
12843 frame (usually by encountering a breakpoint), @value{GDBN} sets the
12844 working language to the language recorded for the function in that
12845 frame. If the language for a frame is unknown (that is, if the function
12846 or block corresponding to the frame was defined in a source file that
12847 does not have a recognized extension), the current working language is
12848 not changed, and @value{GDBN} issues a warning.
12850 This may not seem necessary for most programs, which are written
12851 entirely in one source language. However, program modules and libraries
12852 written in one source language can be used by a main program written in
12853 a different source language. Using @samp{set language auto} in this
12854 case frees you from having to set the working language manually.
12857 @section Displaying the Language
12859 The following commands help you find out which language is the
12860 working language, and also what language source files were written in.
12863 @item show language
12864 @kindex show language
12865 Display the current working language. This is the
12866 language you can use with commands such as @code{print} to
12867 build and compute expressions that may involve variables in your program.
12870 @kindex info frame@r{, show the source language}
12871 Display the source language for this frame. This language becomes the
12872 working language if you use an identifier from this frame.
12873 @xref{Frame Info, ,Information about a Frame}, to identify the other
12874 information listed here.
12877 @kindex info source@r{, show the source language}
12878 Display the source language of this source file.
12879 @xref{Symbols, ,Examining the Symbol Table}, to identify the other
12880 information listed here.
12883 In unusual circumstances, you may have source files with extensions
12884 not in the standard list. You can then set the extension associated
12885 with a language explicitly:
12888 @item set extension-language @var{ext} @var{language}
12889 @kindex set extension-language
12890 Tell @value{GDBN} that source files with extension @var{ext} are to be
12891 assumed as written in the source language @var{language}.
12893 @item info extensions
12894 @kindex info extensions
12895 List all the filename extensions and the associated languages.
12899 @section Type and Range Checking
12901 Some languages are designed to guard you against making seemingly common
12902 errors through a series of compile- and run-time checks. These include
12903 checking the type of arguments to functions and operators and making
12904 sure mathematical overflows are caught at run time. Checks such as
12905 these help to ensure a program's correctness once it has been compiled
12906 by eliminating type mismatches and providing active checks for range
12907 errors when your program is running.
12909 By default @value{GDBN} checks for these errors according to the
12910 rules of the current source language. Although @value{GDBN} does not check
12911 the statements in your program, it can check expressions entered directly
12912 into @value{GDBN} for evaluation via the @code{print} command, for example.
12915 * Type Checking:: An overview of type checking
12916 * Range Checking:: An overview of range checking
12919 @cindex type checking
12920 @cindex checks, type
12921 @node Type Checking
12922 @subsection An Overview of Type Checking
12924 Some languages, such as C and C@t{++}, are strongly typed, meaning that the
12925 arguments to operators and functions have to be of the correct type,
12926 otherwise an error occurs. These checks prevent type mismatch
12927 errors from ever causing any run-time problems. For example,
12930 int klass::my_method(char *b) @{ return b ? 1 : 2; @}
12932 (@value{GDBP}) print obj.my_method (0)
12935 (@value{GDBP}) print obj.my_method (0x1234)
12936 Cannot resolve method klass::my_method to any overloaded instance
12939 The second example fails because in C@t{++} the integer constant
12940 @samp{0x1234} is not type-compatible with the pointer parameter type.
12942 For the expressions you use in @value{GDBN} commands, you can tell
12943 @value{GDBN} to not enforce strict type checking or
12944 to treat any mismatches as errors and abandon the expression;
12945 When type checking is disabled, @value{GDBN} successfully evaluates
12946 expressions like the second example above.
12948 Even if type checking is off, there may be other reasons
12949 related to type that prevent @value{GDBN} from evaluating an expression.
12950 For instance, @value{GDBN} does not know how to add an @code{int} and
12951 a @code{struct foo}. These particular type errors have nothing to do
12952 with the language in use and usually arise from expressions which make
12953 little sense to evaluate anyway.
12955 @value{GDBN} provides some additional commands for controlling type checking:
12957 @kindex set check type
12958 @kindex show check type
12960 @item set check type on
12961 @itemx set check type off
12962 Set strict type checking on or off. If any type mismatches occur in
12963 evaluating an expression while type checking is on, @value{GDBN} prints a
12964 message and aborts evaluation of the expression.
12966 @item show check type
12967 Show the current setting of type checking and whether @value{GDBN}
12968 is enforcing strict type checking rules.
12971 @cindex range checking
12972 @cindex checks, range
12973 @node Range Checking
12974 @subsection An Overview of Range Checking
12976 In some languages (such as Modula-2), it is an error to exceed the
12977 bounds of a type; this is enforced with run-time checks. Such range
12978 checking is meant to ensure program correctness by making sure
12979 computations do not overflow, or indices on an array element access do
12980 not exceed the bounds of the array.
12982 For expressions you use in @value{GDBN} commands, you can tell
12983 @value{GDBN} to treat range errors in one of three ways: ignore them,
12984 always treat them as errors and abandon the expression, or issue
12985 warnings but evaluate the expression anyway.
12987 A range error can result from numerical overflow, from exceeding an
12988 array index bound, or when you type a constant that is not a member
12989 of any type. Some languages, however, do not treat overflows as an
12990 error. In many implementations of C, mathematical overflow causes the
12991 result to ``wrap around'' to lower values---for example, if @var{m} is
12992 the largest integer value, and @var{s} is the smallest, then
12995 @var{m} + 1 @result{} @var{s}
12998 This, too, is specific to individual languages, and in some cases
12999 specific to individual compilers or machines. @xref{Supported Languages, ,
13000 Supported Languages}, for further details on specific languages.
13002 @value{GDBN} provides some additional commands for controlling the range checker:
13004 @kindex set check range
13005 @kindex show check range
13007 @item set check range auto
13008 Set range checking on or off based on the current working language.
13009 @xref{Supported Languages, ,Supported Languages}, for the default settings for
13012 @item set check range on
13013 @itemx set check range off
13014 Set range checking on or off, overriding the default setting for the
13015 current working language. A warning is issued if the setting does not
13016 match the language default. If a range error occurs and range checking is on,
13017 then a message is printed and evaluation of the expression is aborted.
13019 @item set check range warn
13020 Output messages when the @value{GDBN} range checker detects a range error,
13021 but attempt to evaluate the expression anyway. Evaluating the
13022 expression may still be impossible for other reasons, such as accessing
13023 memory that the process does not own (a typical example from many Unix
13027 Show the current setting of the range checker, and whether or not it is
13028 being set automatically by @value{GDBN}.
13031 @node Supported Languages
13032 @section Supported Languages
13034 @value{GDBN} supports C, C@t{++}, D, Go, Objective-C, Fortran, Java,
13035 OpenCL C, Pascal, assembly, Modula-2, and Ada.
13036 @c This is false ...
13037 Some @value{GDBN} features may be used in expressions regardless of the
13038 language you use: the @value{GDBN} @code{@@} and @code{::} operators,
13039 and the @samp{@{type@}addr} construct (@pxref{Expressions,
13040 ,Expressions}) can be used with the constructs of any supported
13043 The following sections detail to what degree each source language is
13044 supported by @value{GDBN}. These sections are not meant to be language
13045 tutorials or references, but serve only as a reference guide to what the
13046 @value{GDBN} expression parser accepts, and what input and output
13047 formats should look like for different languages. There are many good
13048 books written on each of these languages; please look to these for a
13049 language reference or tutorial.
13052 * C:: C and C@t{++}
13055 * Objective-C:: Objective-C
13056 * OpenCL C:: OpenCL C
13057 * Fortran:: Fortran
13059 * Modula-2:: Modula-2
13064 @subsection C and C@t{++}
13066 @cindex C and C@t{++}
13067 @cindex expressions in C or C@t{++}
13069 Since C and C@t{++} are so closely related, many features of @value{GDBN} apply
13070 to both languages. Whenever this is the case, we discuss those languages
13074 @cindex @code{g++}, @sc{gnu} C@t{++} compiler
13075 @cindex @sc{gnu} C@t{++}
13076 The C@t{++} debugging facilities are jointly implemented by the C@t{++}
13077 compiler and @value{GDBN}. Therefore, to debug your C@t{++} code
13078 effectively, you must compile your C@t{++} programs with a supported
13079 C@t{++} compiler, such as @sc{gnu} @code{g++}, or the HP ANSI C@t{++}
13080 compiler (@code{aCC}).
13083 * C Operators:: C and C@t{++} operators
13084 * C Constants:: C and C@t{++} constants
13085 * C Plus Plus Expressions:: C@t{++} expressions
13086 * C Defaults:: Default settings for C and C@t{++}
13087 * C Checks:: C and C@t{++} type and range checks
13088 * Debugging C:: @value{GDBN} and C
13089 * Debugging C Plus Plus:: @value{GDBN} features for C@t{++}
13090 * Decimal Floating Point:: Numbers in Decimal Floating Point format
13094 @subsubsection C and C@t{++} Operators
13096 @cindex C and C@t{++} operators
13098 Operators must be defined on values of specific types. For instance,
13099 @code{+} is defined on numbers, but not on structures. Operators are
13100 often defined on groups of types.
13102 For the purposes of C and C@t{++}, the following definitions hold:
13107 @emph{Integral types} include @code{int} with any of its storage-class
13108 specifiers; @code{char}; @code{enum}; and, for C@t{++}, @code{bool}.
13111 @emph{Floating-point types} include @code{float}, @code{double}, and
13112 @code{long double} (if supported by the target platform).
13115 @emph{Pointer types} include all types defined as @code{(@var{type} *)}.
13118 @emph{Scalar types} include all of the above.
13123 The following operators are supported. They are listed here
13124 in order of increasing precedence:
13128 The comma or sequencing operator. Expressions in a comma-separated list
13129 are evaluated from left to right, with the result of the entire
13130 expression being the last expression evaluated.
13133 Assignment. The value of an assignment expression is the value
13134 assigned. Defined on scalar types.
13137 Used in an expression of the form @w{@code{@var{a} @var{op}= @var{b}}},
13138 and translated to @w{@code{@var{a} = @var{a op b}}}.
13139 @w{@code{@var{op}=}} and @code{=} have the same precedence.
13140 @var{op} is any one of the operators @code{|}, @code{^}, @code{&},
13141 @code{<<}, @code{>>}, @code{+}, @code{-}, @code{*}, @code{/}, @code{%}.
13144 The ternary operator. @code{@var{a} ? @var{b} : @var{c}} can be thought
13145 of as: if @var{a} then @var{b} else @var{c}. @var{a} should be of an
13149 Logical @sc{or}. Defined on integral types.
13152 Logical @sc{and}. Defined on integral types.
13155 Bitwise @sc{or}. Defined on integral types.
13158 Bitwise exclusive-@sc{or}. Defined on integral types.
13161 Bitwise @sc{and}. Defined on integral types.
13164 Equality and inequality. Defined on scalar types. The value of these
13165 expressions is 0 for false and non-zero for true.
13167 @item <@r{, }>@r{, }<=@r{, }>=
13168 Less than, greater than, less than or equal, greater than or equal.
13169 Defined on scalar types. The value of these expressions is 0 for false
13170 and non-zero for true.
13173 left shift, and right shift. Defined on integral types.
13176 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13179 Addition and subtraction. Defined on integral types, floating-point types and
13182 @item *@r{, }/@r{, }%
13183 Multiplication, division, and modulus. Multiplication and division are
13184 defined on integral and floating-point types. Modulus is defined on
13188 Increment and decrement. When appearing before a variable, the
13189 operation is performed before the variable is used in an expression;
13190 when appearing after it, the variable's value is used before the
13191 operation takes place.
13194 Pointer dereferencing. Defined on pointer types. Same precedence as
13198 Address operator. Defined on variables. Same precedence as @code{++}.
13200 For debugging C@t{++}, @value{GDBN} implements a use of @samp{&} beyond what is
13201 allowed in the C@t{++} language itself: you can use @samp{&(&@var{ref})}
13202 to examine the address
13203 where a C@t{++} reference variable (declared with @samp{&@var{ref}}) is
13207 Negative. Defined on integral and floating-point types. Same
13208 precedence as @code{++}.
13211 Logical negation. Defined on integral types. Same precedence as
13215 Bitwise complement operator. Defined on integral types. Same precedence as
13220 Structure member, and pointer-to-structure member. For convenience,
13221 @value{GDBN} regards the two as equivalent, choosing whether to dereference a
13222 pointer based on the stored type information.
13223 Defined on @code{struct} and @code{union} data.
13226 Dereferences of pointers to members.
13229 Array indexing. @code{@var{a}[@var{i}]} is defined as
13230 @code{*(@var{a}+@var{i})}. Same precedence as @code{->}.
13233 Function parameter list. Same precedence as @code{->}.
13236 C@t{++} scope resolution operator. Defined on @code{struct}, @code{union},
13237 and @code{class} types.
13240 Doubled colons also represent the @value{GDBN} scope operator
13241 (@pxref{Expressions, ,Expressions}). Same precedence as @code{::},
13245 If an operator is redefined in the user code, @value{GDBN} usually
13246 attempts to invoke the redefined version instead of using the operator's
13247 predefined meaning.
13250 @subsubsection C and C@t{++} Constants
13252 @cindex C and C@t{++} constants
13254 @value{GDBN} allows you to express the constants of C and C@t{++} in the
13259 Integer constants are a sequence of digits. Octal constants are
13260 specified by a leading @samp{0} (i.e.@: zero), and hexadecimal constants
13261 by a leading @samp{0x} or @samp{0X}. Constants may also end with a letter
13262 @samp{l}, specifying that the constant should be treated as a
13266 Floating point constants are a sequence of digits, followed by a decimal
13267 point, followed by a sequence of digits, and optionally followed by an
13268 exponent. An exponent is of the form:
13269 @samp{@w{e@r{[[}+@r{]|}-@r{]}@var{nnn}}}, where @var{nnn} is another
13270 sequence of digits. The @samp{+} is optional for positive exponents.
13271 A floating-point constant may also end with a letter @samp{f} or
13272 @samp{F}, specifying that the constant should be treated as being of
13273 the @code{float} (as opposed to the default @code{double}) type; or with
13274 a letter @samp{l} or @samp{L}, which specifies a @code{long double}
13278 Enumerated constants consist of enumerated identifiers, or their
13279 integral equivalents.
13282 Character constants are a single character surrounded by single quotes
13283 (@code{'}), or a number---the ordinal value of the corresponding character
13284 (usually its @sc{ascii} value). Within quotes, the single character may
13285 be represented by a letter or by @dfn{escape sequences}, which are of
13286 the form @samp{\@var{nnn}}, where @var{nnn} is the octal representation
13287 of the character's ordinal value; or of the form @samp{\@var{x}}, where
13288 @samp{@var{x}} is a predefined special character---for example,
13289 @samp{\n} for newline.
13291 Wide character constants can be written by prefixing a character
13292 constant with @samp{L}, as in C. For example, @samp{L'x'} is the wide
13293 form of @samp{x}. The target wide character set is used when
13294 computing the value of this constant (@pxref{Character Sets}).
13297 String constants are a sequence of character constants surrounded by
13298 double quotes (@code{"}). Any valid character constant (as described
13299 above) may appear. Double quotes within the string must be preceded by
13300 a backslash, so for instance @samp{"a\"b'c"} is a string of five
13303 Wide string constants can be written by prefixing a string constant
13304 with @samp{L}, as in C. The target wide character set is used when
13305 computing the value of this constant (@pxref{Character Sets}).
13308 Pointer constants are an integral value. You can also write pointers
13309 to constants using the C operator @samp{&}.
13312 Array constants are comma-separated lists surrounded by braces @samp{@{}
13313 and @samp{@}}; for example, @samp{@{1,2,3@}} is a three-element array of
13314 integers, @samp{@{@{1,2@}, @{3,4@}, @{5,6@}@}} is a three-by-two array,
13315 and @samp{@{&"hi", &"there", &"fred"@}} is a three-element array of pointers.
13318 @node C Plus Plus Expressions
13319 @subsubsection C@t{++} Expressions
13321 @cindex expressions in C@t{++}
13322 @value{GDBN} expression handling can interpret most C@t{++} expressions.
13324 @cindex debugging C@t{++} programs
13325 @cindex C@t{++} compilers
13326 @cindex debug formats and C@t{++}
13327 @cindex @value{NGCC} and C@t{++}
13329 @emph{Warning:} @value{GDBN} can only debug C@t{++} code if you use
13330 the proper compiler and the proper debug format. Currently,
13331 @value{GDBN} works best when debugging C@t{++} code that is compiled
13332 with the most recent version of @value{NGCC} possible. The DWARF
13333 debugging format is preferred; @value{NGCC} defaults to this on most
13334 popular platforms. Other compilers and/or debug formats are likely to
13335 work badly or not at all when using @value{GDBN} to debug C@t{++}
13336 code. @xref{Compilation}.
13341 @cindex member functions
13343 Member function calls are allowed; you can use expressions like
13346 count = aml->GetOriginal(x, y)
13349 @vindex this@r{, inside C@t{++} member functions}
13350 @cindex namespace in C@t{++}
13352 While a member function is active (in the selected stack frame), your
13353 expressions have the same namespace available as the member function;
13354 that is, @value{GDBN} allows implicit references to the class instance
13355 pointer @code{this} following the same rules as C@t{++}. @code{using}
13356 declarations in the current scope are also respected by @value{GDBN}.
13358 @cindex call overloaded functions
13359 @cindex overloaded functions, calling
13360 @cindex type conversions in C@t{++}
13362 You can call overloaded functions; @value{GDBN} resolves the function
13363 call to the right definition, with some restrictions. @value{GDBN} does not
13364 perform overload resolution involving user-defined type conversions,
13365 calls to constructors, or instantiations of templates that do not exist
13366 in the program. It also cannot handle ellipsis argument lists or
13369 It does perform integral conversions and promotions, floating-point
13370 promotions, arithmetic conversions, pointer conversions, conversions of
13371 class objects to base classes, and standard conversions such as those of
13372 functions or arrays to pointers; it requires an exact match on the
13373 number of function arguments.
13375 Overload resolution is always performed, unless you have specified
13376 @code{set overload-resolution off}. @xref{Debugging C Plus Plus,
13377 ,@value{GDBN} Features for C@t{++}}.
13379 You must specify @code{set overload-resolution off} in order to use an
13380 explicit function signature to call an overloaded function, as in
13382 p 'foo(char,int)'('x', 13)
13385 The @value{GDBN} command-completion facility can simplify this;
13386 see @ref{Completion, ,Command Completion}.
13388 @cindex reference declarations
13390 @value{GDBN} understands variables declared as C@t{++} references; you can use
13391 them in expressions just as you do in C@t{++} source---they are automatically
13394 In the parameter list shown when @value{GDBN} displays a frame, the values of
13395 reference variables are not displayed (unlike other variables); this
13396 avoids clutter, since references are often used for large structures.
13397 The @emph{address} of a reference variable is always shown, unless
13398 you have specified @samp{set print address off}.
13401 @value{GDBN} supports the C@t{++} name resolution operator @code{::}---your
13402 expressions can use it just as expressions in your program do. Since
13403 one scope may be defined in another, you can use @code{::} repeatedly if
13404 necessary, for example in an expression like
13405 @samp{@var{scope1}::@var{scope2}::@var{name}}. @value{GDBN} also allows
13406 resolving name scope by reference to source files, in both C and C@t{++}
13407 debugging (@pxref{Variables, ,Program Variables}).
13410 @value{GDBN} performs argument-dependent lookup, following the C@t{++}
13415 @subsubsection C and C@t{++} Defaults
13417 @cindex C and C@t{++} defaults
13419 If you allow @value{GDBN} to set range checking automatically, it
13420 defaults to @code{off} whenever the working language changes to
13421 C or C@t{++}. This happens regardless of whether you or @value{GDBN}
13422 selects the working language.
13424 If you allow @value{GDBN} to set the language automatically, it
13425 recognizes source files whose names end with @file{.c}, @file{.C}, or
13426 @file{.cc}, etc, and when @value{GDBN} enters code compiled from one of
13427 these files, it sets the working language to C or C@t{++}.
13428 @xref{Automatically, ,Having @value{GDBN} Infer the Source Language},
13429 for further details.
13432 @subsubsection C and C@t{++} Type and Range Checks
13434 @cindex C and C@t{++} checks
13436 By default, when @value{GDBN} parses C or C@t{++} expressions, strict type
13437 checking is used. However, if you turn type checking off, @value{GDBN}
13438 will allow certain non-standard conversions, such as promoting integer
13439 constants to pointers.
13441 Range checking, if turned on, is done on mathematical operations. Array
13442 indices are not checked, since they are often used to index a pointer
13443 that is not itself an array.
13446 @subsubsection @value{GDBN} and C
13448 The @code{set print union} and @code{show print union} commands apply to
13449 the @code{union} type. When set to @samp{on}, any @code{union} that is
13450 inside a @code{struct} or @code{class} is also printed. Otherwise, it
13451 appears as @samp{@{...@}}.
13453 The @code{@@} operator aids in the debugging of dynamic arrays, formed
13454 with pointers and a memory allocation function. @xref{Expressions,
13457 @node Debugging C Plus Plus
13458 @subsubsection @value{GDBN} Features for C@t{++}
13460 @cindex commands for C@t{++}
13462 Some @value{GDBN} commands are particularly useful with C@t{++}, and some are
13463 designed specifically for use with C@t{++}. Here is a summary:
13466 @cindex break in overloaded functions
13467 @item @r{breakpoint menus}
13468 When you want a breakpoint in a function whose name is overloaded,
13469 @value{GDBN} has the capability to display a menu of possible breakpoint
13470 locations to help you specify which function definition you want.
13471 @xref{Ambiguous Expressions,,Ambiguous Expressions}.
13473 @cindex overloading in C@t{++}
13474 @item rbreak @var{regex}
13475 Setting breakpoints using regular expressions is helpful for setting
13476 breakpoints on overloaded functions that are not members of any special
13478 @xref{Set Breaks, ,Setting Breakpoints}.
13480 @cindex C@t{++} exception handling
13483 Debug C@t{++} exception handling using these commands. @xref{Set
13484 Catchpoints, , Setting Catchpoints}.
13486 @cindex inheritance
13487 @item ptype @var{typename}
13488 Print inheritance relationships as well as other information for type
13490 @xref{Symbols, ,Examining the Symbol Table}.
13492 @item info vtbl @var{expression}.
13493 The @code{info vtbl} command can be used to display the virtual
13494 method tables of the object computed by @var{expression}. This shows
13495 one entry per virtual table; there may be multiple virtual tables when
13496 multiple inheritance is in use.
13498 @cindex C@t{++} symbol display
13499 @item set print demangle
13500 @itemx show print demangle
13501 @itemx set print asm-demangle
13502 @itemx show print asm-demangle
13503 Control whether C@t{++} symbols display in their source form, both when
13504 displaying code as C@t{++} source and when displaying disassemblies.
13505 @xref{Print Settings, ,Print Settings}.
13507 @item set print object
13508 @itemx show print object
13509 Choose whether to print derived (actual) or declared types of objects.
13510 @xref{Print Settings, ,Print Settings}.
13512 @item set print vtbl
13513 @itemx show print vtbl
13514 Control the format for printing virtual function tables.
13515 @xref{Print Settings, ,Print Settings}.
13516 (The @code{vtbl} commands do not work on programs compiled with the HP
13517 ANSI C@t{++} compiler (@code{aCC}).)
13519 @kindex set overload-resolution
13520 @cindex overloaded functions, overload resolution
13521 @item set overload-resolution on
13522 Enable overload resolution for C@t{++} expression evaluation. The default
13523 is on. For overloaded functions, @value{GDBN} evaluates the arguments
13524 and searches for a function whose signature matches the argument types,
13525 using the standard C@t{++} conversion rules (see @ref{C Plus Plus
13526 Expressions, ,C@t{++} Expressions}, for details).
13527 If it cannot find a match, it emits a message.
13529 @item set overload-resolution off
13530 Disable overload resolution for C@t{++} expression evaluation. For
13531 overloaded functions that are not class member functions, @value{GDBN}
13532 chooses the first function of the specified name that it finds in the
13533 symbol table, whether or not its arguments are of the correct type. For
13534 overloaded functions that are class member functions, @value{GDBN}
13535 searches for a function whose signature @emph{exactly} matches the
13538 @kindex show overload-resolution
13539 @item show overload-resolution
13540 Show the current setting of overload resolution.
13542 @item @r{Overloaded symbol names}
13543 You can specify a particular definition of an overloaded symbol, using
13544 the same notation that is used to declare such symbols in C@t{++}: type
13545 @code{@var{symbol}(@var{types})} rather than just @var{symbol}. You can
13546 also use the @value{GDBN} command-line word completion facilities to list the
13547 available choices, or to finish the type list for you.
13548 @xref{Completion,, Command Completion}, for details on how to do this.
13551 @node Decimal Floating Point
13552 @subsubsection Decimal Floating Point format
13553 @cindex decimal floating point format
13555 @value{GDBN} can examine, set and perform computations with numbers in
13556 decimal floating point format, which in the C language correspond to the
13557 @code{_Decimal32}, @code{_Decimal64} and @code{_Decimal128} types as
13558 specified by the extension to support decimal floating-point arithmetic.
13560 There are two encodings in use, depending on the architecture: BID (Binary
13561 Integer Decimal) for x86 and x86-64, and DPD (Densely Packed Decimal) for
13562 PowerPC. @value{GDBN} will use the appropriate encoding for the configured
13565 Because of a limitation in @file{libdecnumber}, the library used by @value{GDBN}
13566 to manipulate decimal floating point numbers, it is not possible to convert
13567 (using a cast, for example) integers wider than 32-bit to decimal float.
13569 In addition, in order to imitate @value{GDBN}'s behaviour with binary floating
13570 point computations, error checking in decimal float operations ignores
13571 underflow, overflow and divide by zero exceptions.
13573 In the PowerPC architecture, @value{GDBN} provides a set of pseudo-registers
13574 to inspect @code{_Decimal128} values stored in floating point registers.
13575 See @ref{PowerPC,,PowerPC} for more details.
13581 @value{GDBN} can be used to debug programs written in D and compiled with
13582 GDC, LDC or DMD compilers. Currently @value{GDBN} supports only one D
13583 specific feature --- dynamic arrays.
13588 @cindex Go (programming language)
13589 @value{GDBN} can be used to debug programs written in Go and compiled with
13590 @file{gccgo} or @file{6g} compilers.
13592 Here is a summary of the Go-specific features and restrictions:
13595 @cindex current Go package
13596 @item The current Go package
13597 The name of the current package does not need to be specified when
13598 specifying global variables and functions.
13600 For example, given the program:
13604 var myglob = "Shall we?"
13610 When stopped inside @code{main} either of these work:
13614 (gdb) p main.myglob
13617 @cindex builtin Go types
13618 @item Builtin Go types
13619 The @code{string} type is recognized by @value{GDBN} and is printed
13622 @cindex builtin Go functions
13623 @item Builtin Go functions
13624 The @value{GDBN} expression parser recognizes the @code{unsafe.Sizeof}
13625 function and handles it internally.
13627 @cindex restrictions on Go expressions
13628 @item Restrictions on Go expressions
13629 All Go operators are supported except @code{&^}.
13630 The Go @code{_} ``blank identifier'' is not supported.
13631 Automatic dereferencing of pointers is not supported.
13635 @subsection Objective-C
13637 @cindex Objective-C
13638 This section provides information about some commands and command
13639 options that are useful for debugging Objective-C code. See also
13640 @ref{Symbols, info classes}, and @ref{Symbols, info selectors}, for a
13641 few more commands specific to Objective-C support.
13644 * Method Names in Commands::
13645 * The Print Command with Objective-C::
13648 @node Method Names in Commands
13649 @subsubsection Method Names in Commands
13651 The following commands have been extended to accept Objective-C method
13652 names as line specifications:
13654 @kindex clear@r{, and Objective-C}
13655 @kindex break@r{, and Objective-C}
13656 @kindex info line@r{, and Objective-C}
13657 @kindex jump@r{, and Objective-C}
13658 @kindex list@r{, and Objective-C}
13662 @item @code{info line}
13667 A fully qualified Objective-C method name is specified as
13670 -[@var{Class} @var{methodName}]
13673 where the minus sign is used to indicate an instance method and a
13674 plus sign (not shown) is used to indicate a class method. The class
13675 name @var{Class} and method name @var{methodName} are enclosed in
13676 brackets, similar to the way messages are specified in Objective-C
13677 source code. For example, to set a breakpoint at the @code{create}
13678 instance method of class @code{Fruit} in the program currently being
13682 break -[Fruit create]
13685 To list ten program lines around the @code{initialize} class method,
13689 list +[NSText initialize]
13692 In the current version of @value{GDBN}, the plus or minus sign is
13693 required. In future versions of @value{GDBN}, the plus or minus
13694 sign will be optional, but you can use it to narrow the search. It
13695 is also possible to specify just a method name:
13701 You must specify the complete method name, including any colons. If
13702 your program's source files contain more than one @code{create} method,
13703 you'll be presented with a numbered list of classes that implement that
13704 method. Indicate your choice by number, or type @samp{0} to exit if
13707 As another example, to clear a breakpoint established at the
13708 @code{makeKeyAndOrderFront:} method of the @code{NSWindow} class, enter:
13711 clear -[NSWindow makeKeyAndOrderFront:]
13714 @node The Print Command with Objective-C
13715 @subsubsection The Print Command With Objective-C
13716 @cindex Objective-C, print objects
13717 @kindex print-object
13718 @kindex po @r{(@code{print-object})}
13720 The print command has also been extended to accept methods. For example:
13723 print -[@var{object} hash]
13726 @cindex print an Objective-C object description
13727 @cindex @code{_NSPrintForDebugger}, and printing Objective-C objects
13729 will tell @value{GDBN} to send the @code{hash} message to @var{object}
13730 and print the result. Also, an additional command has been added,
13731 @code{print-object} or @code{po} for short, which is meant to print
13732 the description of an object. However, this command may only work
13733 with certain Objective-C libraries that have a particular hook
13734 function, @code{_NSPrintForDebugger}, defined.
13737 @subsection OpenCL C
13740 This section provides information about @value{GDBN}s OpenCL C support.
13743 * OpenCL C Datatypes::
13744 * OpenCL C Expressions::
13745 * OpenCL C Operators::
13748 @node OpenCL C Datatypes
13749 @subsubsection OpenCL C Datatypes
13751 @cindex OpenCL C Datatypes
13752 @value{GDBN} supports the builtin scalar and vector datatypes specified
13753 by OpenCL 1.1. In addition the half- and double-precision floating point
13754 data types of the @code{cl_khr_fp16} and @code{cl_khr_fp64} OpenCL
13755 extensions are also known to @value{GDBN}.
13757 @node OpenCL C Expressions
13758 @subsubsection OpenCL C Expressions
13760 @cindex OpenCL C Expressions
13761 @value{GDBN} supports accesses to vector components including the access as
13762 lvalue where possible. Since OpenCL C is based on C99 most C expressions
13763 supported by @value{GDBN} can be used as well.
13765 @node OpenCL C Operators
13766 @subsubsection OpenCL C Operators
13768 @cindex OpenCL C Operators
13769 @value{GDBN} supports the operators specified by OpenCL 1.1 for scalar and
13773 @subsection Fortran
13774 @cindex Fortran-specific support in @value{GDBN}
13776 @value{GDBN} can be used to debug programs written in Fortran, but it
13777 currently supports only the features of Fortran 77 language.
13779 @cindex trailing underscore, in Fortran symbols
13780 Some Fortran compilers (@sc{gnu} Fortran 77 and Fortran 95 compilers
13781 among them) append an underscore to the names of variables and
13782 functions. When you debug programs compiled by those compilers, you
13783 will need to refer to variables and functions with a trailing
13787 * Fortran Operators:: Fortran operators and expressions
13788 * Fortran Defaults:: Default settings for Fortran
13789 * Special Fortran Commands:: Special @value{GDBN} commands for Fortran
13792 @node Fortran Operators
13793 @subsubsection Fortran Operators and Expressions
13795 @cindex Fortran operators and expressions
13797 Operators must be defined on values of specific types. For instance,
13798 @code{+} is defined on numbers, but not on characters or other non-
13799 arithmetic types. Operators are often defined on groups of types.
13803 The exponentiation operator. It raises the first operand to the power
13807 The range operator. Normally used in the form of array(low:high) to
13808 represent a section of array.
13811 The access component operator. Normally used to access elements in derived
13812 types. Also suitable for unions. As unions aren't part of regular Fortran,
13813 this can only happen when accessing a register that uses a gdbarch-defined
13817 @node Fortran Defaults
13818 @subsubsection Fortran Defaults
13820 @cindex Fortran Defaults
13822 Fortran symbols are usually case-insensitive, so @value{GDBN} by
13823 default uses case-insensitive matches for Fortran symbols. You can
13824 change that with the @samp{set case-insensitive} command, see
13825 @ref{Symbols}, for the details.
13827 @node Special Fortran Commands
13828 @subsubsection Special Fortran Commands
13830 @cindex Special Fortran commands
13832 @value{GDBN} has some commands to support Fortran-specific features,
13833 such as displaying common blocks.
13836 @cindex @code{COMMON} blocks, Fortran
13837 @kindex info common
13838 @item info common @r{[}@var{common-name}@r{]}
13839 This command prints the values contained in the Fortran @code{COMMON}
13840 block whose name is @var{common-name}. With no argument, the names of
13841 all @code{COMMON} blocks visible at the current program location are
13848 @cindex Pascal support in @value{GDBN}, limitations
13849 Debugging Pascal programs which use sets, subranges, file variables, or
13850 nested functions does not currently work. @value{GDBN} does not support
13851 entering expressions, printing values, or similar features using Pascal
13854 The Pascal-specific command @code{set print pascal_static-members}
13855 controls whether static members of Pascal objects are displayed.
13856 @xref{Print Settings, pascal_static-members}.
13859 @subsection Modula-2
13861 @cindex Modula-2, @value{GDBN} support
13863 The extensions made to @value{GDBN} to support Modula-2 only support
13864 output from the @sc{gnu} Modula-2 compiler (which is currently being
13865 developed). Other Modula-2 compilers are not currently supported, and
13866 attempting to debug executables produced by them is most likely
13867 to give an error as @value{GDBN} reads in the executable's symbol
13870 @cindex expressions in Modula-2
13872 * M2 Operators:: Built-in operators
13873 * Built-In Func/Proc:: Built-in functions and procedures
13874 * M2 Constants:: Modula-2 constants
13875 * M2 Types:: Modula-2 types
13876 * M2 Defaults:: Default settings for Modula-2
13877 * Deviations:: Deviations from standard Modula-2
13878 * M2 Checks:: Modula-2 type and range checks
13879 * M2 Scope:: The scope operators @code{::} and @code{.}
13880 * GDB/M2:: @value{GDBN} and Modula-2
13884 @subsubsection Operators
13885 @cindex Modula-2 operators
13887 Operators must be defined on values of specific types. For instance,
13888 @code{+} is defined on numbers, but not on structures. Operators are
13889 often defined on groups of types. For the purposes of Modula-2, the
13890 following definitions hold:
13895 @emph{Integral types} consist of @code{INTEGER}, @code{CARDINAL}, and
13899 @emph{Character types} consist of @code{CHAR} and its subranges.
13902 @emph{Floating-point types} consist of @code{REAL}.
13905 @emph{Pointer types} consist of anything declared as @code{POINTER TO
13909 @emph{Scalar types} consist of all of the above.
13912 @emph{Set types} consist of @code{SET} and @code{BITSET} types.
13915 @emph{Boolean types} consist of @code{BOOLEAN}.
13919 The following operators are supported, and appear in order of
13920 increasing precedence:
13924 Function argument or array index separator.
13927 Assignment. The value of @var{var} @code{:=} @var{value} is
13931 Less than, greater than on integral, floating-point, or enumerated
13935 Less than or equal to, greater than or equal to
13936 on integral, floating-point and enumerated types, or set inclusion on
13937 set types. Same precedence as @code{<}.
13939 @item =@r{, }<>@r{, }#
13940 Equality and two ways of expressing inequality, valid on scalar types.
13941 Same precedence as @code{<}. In @value{GDBN} scripts, only @code{<>} is
13942 available for inequality, since @code{#} conflicts with the script
13946 Set membership. Defined on set types and the types of their members.
13947 Same precedence as @code{<}.
13950 Boolean disjunction. Defined on boolean types.
13953 Boolean conjunction. Defined on boolean types.
13956 The @value{GDBN} ``artificial array'' operator (@pxref{Expressions, ,Expressions}).
13959 Addition and subtraction on integral and floating-point types, or union
13960 and difference on set types.
13963 Multiplication on integral and floating-point types, or set intersection
13967 Division on floating-point types, or symmetric set difference on set
13968 types. Same precedence as @code{*}.
13971 Integer division and remainder. Defined on integral types. Same
13972 precedence as @code{*}.
13975 Negative. Defined on @code{INTEGER} and @code{REAL} data.
13978 Pointer dereferencing. Defined on pointer types.
13981 Boolean negation. Defined on boolean types. Same precedence as
13985 @code{RECORD} field selector. Defined on @code{RECORD} data. Same
13986 precedence as @code{^}.
13989 Array indexing. Defined on @code{ARRAY} data. Same precedence as @code{^}.
13992 Procedure argument list. Defined on @code{PROCEDURE} objects. Same precedence
13996 @value{GDBN} and Modula-2 scope operators.
14000 @emph{Warning:} Set expressions and their operations are not yet supported, so @value{GDBN}
14001 treats the use of the operator @code{IN}, or the use of operators
14002 @code{+}, @code{-}, @code{*}, @code{/}, @code{=}, , @code{<>}, @code{#},
14003 @code{<=}, and @code{>=} on sets as an error.
14007 @node Built-In Func/Proc
14008 @subsubsection Built-in Functions and Procedures
14009 @cindex Modula-2 built-ins
14011 Modula-2 also makes available several built-in procedures and functions.
14012 In describing these, the following metavariables are used:
14017 represents an @code{ARRAY} variable.
14020 represents a @code{CHAR} constant or variable.
14023 represents a variable or constant of integral type.
14026 represents an identifier that belongs to a set. Generally used in the
14027 same function with the metavariable @var{s}. The type of @var{s} should
14028 be @code{SET OF @var{mtype}} (where @var{mtype} is the type of @var{m}).
14031 represents a variable or constant of integral or floating-point type.
14034 represents a variable or constant of floating-point type.
14040 represents a variable.
14043 represents a variable or constant of one of many types. See the
14044 explanation of the function for details.
14047 All Modula-2 built-in procedures also return a result, described below.
14051 Returns the absolute value of @var{n}.
14054 If @var{c} is a lower case letter, it returns its upper case
14055 equivalent, otherwise it returns its argument.
14058 Returns the character whose ordinal value is @var{i}.
14061 Decrements the value in the variable @var{v} by one. Returns the new value.
14063 @item DEC(@var{v},@var{i})
14064 Decrements the value in the variable @var{v} by @var{i}. Returns the
14067 @item EXCL(@var{m},@var{s})
14068 Removes the element @var{m} from the set @var{s}. Returns the new
14071 @item FLOAT(@var{i})
14072 Returns the floating point equivalent of the integer @var{i}.
14074 @item HIGH(@var{a})
14075 Returns the index of the last member of @var{a}.
14078 Increments the value in the variable @var{v} by one. Returns the new value.
14080 @item INC(@var{v},@var{i})
14081 Increments the value in the variable @var{v} by @var{i}. Returns the
14084 @item INCL(@var{m},@var{s})
14085 Adds the element @var{m} to the set @var{s} if it is not already
14086 there. Returns the new set.
14089 Returns the maximum value of the type @var{t}.
14092 Returns the minimum value of the type @var{t}.
14095 Returns boolean TRUE if @var{i} is an odd number.
14098 Returns the ordinal value of its argument. For example, the ordinal
14099 value of a character is its @sc{ascii} value (on machines supporting the
14100 @sc{ascii} character set). @var{x} must be of an ordered type, which include
14101 integral, character and enumerated types.
14103 @item SIZE(@var{x})
14104 Returns the size of its argument. @var{x} can be a variable or a type.
14106 @item TRUNC(@var{r})
14107 Returns the integral part of @var{r}.
14109 @item TSIZE(@var{x})
14110 Returns the size of its argument. @var{x} can be a variable or a type.
14112 @item VAL(@var{t},@var{i})
14113 Returns the member of the type @var{t} whose ordinal value is @var{i}.
14117 @emph{Warning:} Sets and their operations are not yet supported, so
14118 @value{GDBN} treats the use of procedures @code{INCL} and @code{EXCL} as
14122 @cindex Modula-2 constants
14124 @subsubsection Constants
14126 @value{GDBN} allows you to express the constants of Modula-2 in the following
14132 Integer constants are simply a sequence of digits. When used in an
14133 expression, a constant is interpreted to be type-compatible with the
14134 rest of the expression. Hexadecimal integers are specified by a
14135 trailing @samp{H}, and octal integers by a trailing @samp{B}.
14138 Floating point constants appear as a sequence of digits, followed by a
14139 decimal point and another sequence of digits. An optional exponent can
14140 then be specified, in the form @samp{E@r{[}+@r{|}-@r{]}@var{nnn}}, where
14141 @samp{@r{[}+@r{|}-@r{]}@var{nnn}} is the desired exponent. All of the
14142 digits of the floating point constant must be valid decimal (base 10)
14146 Character constants consist of a single character enclosed by a pair of
14147 like quotes, either single (@code{'}) or double (@code{"}). They may
14148 also be expressed by their ordinal value (their @sc{ascii} value, usually)
14149 followed by a @samp{C}.
14152 String constants consist of a sequence of characters enclosed by a
14153 pair of like quotes, either single (@code{'}) or double (@code{"}).
14154 Escape sequences in the style of C are also allowed. @xref{C
14155 Constants, ,C and C@t{++} Constants}, for a brief explanation of escape
14159 Enumerated constants consist of an enumerated identifier.
14162 Boolean constants consist of the identifiers @code{TRUE} and
14166 Pointer constants consist of integral values only.
14169 Set constants are not yet supported.
14173 @subsubsection Modula-2 Types
14174 @cindex Modula-2 types
14176 Currently @value{GDBN} can print the following data types in Modula-2
14177 syntax: array types, record types, set types, pointer types, procedure
14178 types, enumerated types, subrange types and base types. You can also
14179 print the contents of variables declared using these type.
14180 This section gives a number of simple source code examples together with
14181 sample @value{GDBN} sessions.
14183 The first example contains the following section of code:
14192 and you can request @value{GDBN} to interrogate the type and value of
14193 @code{r} and @code{s}.
14196 (@value{GDBP}) print s
14198 (@value{GDBP}) ptype s
14200 (@value{GDBP}) print r
14202 (@value{GDBP}) ptype r
14207 Likewise if your source code declares @code{s} as:
14211 s: SET ['A'..'Z'] ;
14215 then you may query the type of @code{s} by:
14218 (@value{GDBP}) ptype s
14219 type = SET ['A'..'Z']
14223 Note that at present you cannot interactively manipulate set
14224 expressions using the debugger.
14226 The following example shows how you might declare an array in Modula-2
14227 and how you can interact with @value{GDBN} to print its type and contents:
14231 s: ARRAY [-10..10] OF CHAR ;
14235 (@value{GDBP}) ptype s
14236 ARRAY [-10..10] OF CHAR
14239 Note that the array handling is not yet complete and although the type
14240 is printed correctly, expression handling still assumes that all
14241 arrays have a lower bound of zero and not @code{-10} as in the example
14244 Here are some more type related Modula-2 examples:
14248 colour = (blue, red, yellow, green) ;
14249 t = [blue..yellow] ;
14257 The @value{GDBN} interaction shows how you can query the data type
14258 and value of a variable.
14261 (@value{GDBP}) print s
14263 (@value{GDBP}) ptype t
14264 type = [blue..yellow]
14268 In this example a Modula-2 array is declared and its contents
14269 displayed. Observe that the contents are written in the same way as
14270 their @code{C} counterparts.
14274 s: ARRAY [1..5] OF CARDINAL ;
14280 (@value{GDBP}) print s
14281 $1 = @{1, 0, 0, 0, 0@}
14282 (@value{GDBP}) ptype s
14283 type = ARRAY [1..5] OF CARDINAL
14286 The Modula-2 language interface to @value{GDBN} also understands
14287 pointer types as shown in this example:
14291 s: POINTER TO ARRAY [1..5] OF CARDINAL ;
14298 and you can request that @value{GDBN} describes the type of @code{s}.
14301 (@value{GDBP}) ptype s
14302 type = POINTER TO ARRAY [1..5] OF CARDINAL
14305 @value{GDBN} handles compound types as we can see in this example.
14306 Here we combine array types, record types, pointer types and subrange
14317 myarray = ARRAY myrange OF CARDINAL ;
14318 myrange = [-2..2] ;
14320 s: POINTER TO ARRAY myrange OF foo ;
14324 and you can ask @value{GDBN} to describe the type of @code{s} as shown
14328 (@value{GDBP}) ptype s
14329 type = POINTER TO ARRAY [-2..2] OF foo = RECORD
14332 f3 : ARRAY [-2..2] OF CARDINAL;
14337 @subsubsection Modula-2 Defaults
14338 @cindex Modula-2 defaults
14340 If type and range checking are set automatically by @value{GDBN}, they
14341 both default to @code{on} whenever the working language changes to
14342 Modula-2. This happens regardless of whether you or @value{GDBN}
14343 selected the working language.
14345 If you allow @value{GDBN} to set the language automatically, then entering
14346 code compiled from a file whose name ends with @file{.mod} sets the
14347 working language to Modula-2. @xref{Automatically, ,Having @value{GDBN}
14348 Infer the Source Language}, for further details.
14351 @subsubsection Deviations from Standard Modula-2
14352 @cindex Modula-2, deviations from
14354 A few changes have been made to make Modula-2 programs easier to debug.
14355 This is done primarily via loosening its type strictness:
14359 Unlike in standard Modula-2, pointer constants can be formed by
14360 integers. This allows you to modify pointer variables during
14361 debugging. (In standard Modula-2, the actual address contained in a
14362 pointer variable is hidden from you; it can only be modified
14363 through direct assignment to another pointer variable or expression that
14364 returned a pointer.)
14367 C escape sequences can be used in strings and characters to represent
14368 non-printable characters. @value{GDBN} prints out strings with these
14369 escape sequences embedded. Single non-printable characters are
14370 printed using the @samp{CHR(@var{nnn})} format.
14373 The assignment operator (@code{:=}) returns the value of its right-hand
14377 All built-in procedures both modify @emph{and} return their argument.
14381 @subsubsection Modula-2 Type and Range Checks
14382 @cindex Modula-2 checks
14385 @emph{Warning:} in this release, @value{GDBN} does not yet perform type or
14388 @c FIXME remove warning when type/range checks added
14390 @value{GDBN} considers two Modula-2 variables type equivalent if:
14394 They are of types that have been declared equivalent via a @code{TYPE
14395 @var{t1} = @var{t2}} statement
14398 They have been declared on the same line. (Note: This is true of the
14399 @sc{gnu} Modula-2 compiler, but it may not be true of other compilers.)
14402 As long as type checking is enabled, any attempt to combine variables
14403 whose types are not equivalent is an error.
14405 Range checking is done on all mathematical operations, assignment, array
14406 index bounds, and all built-in functions and procedures.
14409 @subsubsection The Scope Operators @code{::} and @code{.}
14411 @cindex @code{.}, Modula-2 scope operator
14412 @cindex colon, doubled as scope operator
14414 @vindex colon-colon@r{, in Modula-2}
14415 @c Info cannot handle :: but TeX can.
14418 @vindex ::@r{, in Modula-2}
14421 There are a few subtle differences between the Modula-2 scope operator
14422 (@code{.}) and the @value{GDBN} scope operator (@code{::}). The two have
14427 @var{module} . @var{id}
14428 @var{scope} :: @var{id}
14432 where @var{scope} is the name of a module or a procedure,
14433 @var{module} the name of a module, and @var{id} is any declared
14434 identifier within your program, except another module.
14436 Using the @code{::} operator makes @value{GDBN} search the scope
14437 specified by @var{scope} for the identifier @var{id}. If it is not
14438 found in the specified scope, then @value{GDBN} searches all scopes
14439 enclosing the one specified by @var{scope}.
14441 Using the @code{.} operator makes @value{GDBN} search the current scope for
14442 the identifier specified by @var{id} that was imported from the
14443 definition module specified by @var{module}. With this operator, it is
14444 an error if the identifier @var{id} was not imported from definition
14445 module @var{module}, or if @var{id} is not an identifier in
14449 @subsubsection @value{GDBN} and Modula-2
14451 Some @value{GDBN} commands have little use when debugging Modula-2 programs.
14452 Five subcommands of @code{set print} and @code{show print} apply
14453 specifically to C and C@t{++}: @samp{vtbl}, @samp{demangle},
14454 @samp{asm-demangle}, @samp{object}, and @samp{union}. The first four
14455 apply to C@t{++}, and the last to the C @code{union} type, which has no direct
14456 analogue in Modula-2.
14458 The @code{@@} operator (@pxref{Expressions, ,Expressions}), while available
14459 with any language, is not useful with Modula-2. Its
14460 intent is to aid the debugging of @dfn{dynamic arrays}, which cannot be
14461 created in Modula-2 as they can in C or C@t{++}. However, because an
14462 address can be specified by an integral constant, the construct
14463 @samp{@{@var{type}@}@var{adrexp}} is still useful.
14465 @cindex @code{#} in Modula-2
14466 In @value{GDBN} scripts, the Modula-2 inequality operator @code{#} is
14467 interpreted as the beginning of a comment. Use @code{<>} instead.
14473 The extensions made to @value{GDBN} for Ada only support
14474 output from the @sc{gnu} Ada (GNAT) compiler.
14475 Other Ada compilers are not currently supported, and
14476 attempting to debug executables produced by them is most likely
14480 @cindex expressions in Ada
14482 * Ada Mode Intro:: General remarks on the Ada syntax
14483 and semantics supported by Ada mode
14485 * Omissions from Ada:: Restrictions on the Ada expression syntax.
14486 * Additions to Ada:: Extensions of the Ada expression syntax.
14487 * Stopping Before Main Program:: Debugging the program during elaboration.
14488 * Ada Tasks:: Listing and setting breakpoints in tasks.
14489 * Ada Tasks and Core Files:: Tasking Support when Debugging Core Files
14490 * Ravenscar Profile:: Tasking Support when using the Ravenscar
14492 * Ada Glitches:: Known peculiarities of Ada mode.
14495 @node Ada Mode Intro
14496 @subsubsection Introduction
14497 @cindex Ada mode, general
14499 The Ada mode of @value{GDBN} supports a fairly large subset of Ada expression
14500 syntax, with some extensions.
14501 The philosophy behind the design of this subset is
14505 That @value{GDBN} should provide basic literals and access to operations for
14506 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
14507 leaving more sophisticated computations to subprograms written into the
14508 program (which therefore may be called from @value{GDBN}).
14511 That type safety and strict adherence to Ada language restrictions
14512 are not particularly important to the @value{GDBN} user.
14515 That brevity is important to the @value{GDBN} user.
14518 Thus, for brevity, the debugger acts as if all names declared in
14519 user-written packages are directly visible, even if they are not visible
14520 according to Ada rules, thus making it unnecessary to fully qualify most
14521 names with their packages, regardless of context. Where this causes
14522 ambiguity, @value{GDBN} asks the user's intent.
14524 The debugger will start in Ada mode if it detects an Ada main program.
14525 As for other languages, it will enter Ada mode when stopped in a program that
14526 was translated from an Ada source file.
14528 While in Ada mode, you may use `@t{--}' for comments. This is useful
14529 mostly for documenting command files. The standard @value{GDBN} comment
14530 (@samp{#}) still works at the beginning of a line in Ada mode, but not in the
14531 middle (to allow based literals).
14533 The debugger supports limited overloading. Given a subprogram call in which
14534 the function symbol has multiple definitions, it will use the number of
14535 actual parameters and some information about their types to attempt to narrow
14536 the set of definitions. It also makes very limited use of context, preferring
14537 procedures to functions in the context of the @code{call} command, and
14538 functions to procedures elsewhere.
14540 @node Omissions from Ada
14541 @subsubsection Omissions from Ada
14542 @cindex Ada, omissions from
14544 Here are the notable omissions from the subset:
14548 Only a subset of the attributes are supported:
14552 @t{'First}, @t{'Last}, and @t{'Length}
14553 on array objects (not on types and subtypes).
14556 @t{'Min} and @t{'Max}.
14559 @t{'Pos} and @t{'Val}.
14565 @t{'Range} on array objects (not subtypes), but only as the right
14566 operand of the membership (@code{in}) operator.
14569 @t{'Access}, @t{'Unchecked_Access}, and
14570 @t{'Unrestricted_Access} (a GNAT extension).
14578 @code{Characters.Latin_1} are not available and
14579 concatenation is not implemented. Thus, escape characters in strings are
14580 not currently available.
14583 Equality tests (@samp{=} and @samp{/=}) on arrays test for bitwise
14584 equality of representations. They will generally work correctly
14585 for strings and arrays whose elements have integer or enumeration types.
14586 They may not work correctly for arrays whose element
14587 types have user-defined equality, for arrays of real values
14588 (in particular, IEEE-conformant floating point, because of negative
14589 zeroes and NaNs), and for arrays whose elements contain unused bits with
14590 indeterminate values.
14593 The other component-by-component array operations (@code{and}, @code{or},
14594 @code{xor}, @code{not}, and relational tests other than equality)
14595 are not implemented.
14598 @cindex array aggregates (Ada)
14599 @cindex record aggregates (Ada)
14600 @cindex aggregates (Ada)
14601 There is limited support for array and record aggregates. They are
14602 permitted only on the right sides of assignments, as in these examples:
14605 (@value{GDBP}) set An_Array := (1, 2, 3, 4, 5, 6)
14606 (@value{GDBP}) set An_Array := (1, others => 0)
14607 (@value{GDBP}) set An_Array := (0|4 => 1, 1..3 => 2, 5 => 6)
14608 (@value{GDBP}) set A_2D_Array := ((1, 2, 3), (4, 5, 6), (7, 8, 9))
14609 (@value{GDBP}) set A_Record := (1, "Peter", True);
14610 (@value{GDBP}) set A_Record := (Name => "Peter", Id => 1, Alive => True)
14614 discriminant's value by assigning an aggregate has an
14615 undefined effect if that discriminant is used within the record.
14616 However, you can first modify discriminants by directly assigning to
14617 them (which normally would not be allowed in Ada), and then performing an
14618 aggregate assignment. For example, given a variable @code{A_Rec}
14619 declared to have a type such as:
14622 type Rec (Len : Small_Integer := 0) is record
14624 Vals : IntArray (1 .. Len);
14628 you can assign a value with a different size of @code{Vals} with two
14632 (@value{GDBP}) set A_Rec.Len := 4
14633 (@value{GDBP}) set A_Rec := (Id => 42, Vals => (1, 2, 3, 4))
14636 As this example also illustrates, @value{GDBN} is very loose about the usual
14637 rules concerning aggregates. You may leave out some of the
14638 components of an array or record aggregate (such as the @code{Len}
14639 component in the assignment to @code{A_Rec} above); they will retain their
14640 original values upon assignment. You may freely use dynamic values as
14641 indices in component associations. You may even use overlapping or
14642 redundant component associations, although which component values are
14643 assigned in such cases is not defined.
14646 Calls to dispatching subprograms are not implemented.
14649 The overloading algorithm is much more limited (i.e., less selective)
14650 than that of real Ada. It makes only limited use of the context in
14651 which a subexpression appears to resolve its meaning, and it is much
14652 looser in its rules for allowing type matches. As a result, some
14653 function calls will be ambiguous, and the user will be asked to choose
14654 the proper resolution.
14657 The @code{new} operator is not implemented.
14660 Entry calls are not implemented.
14663 Aside from printing, arithmetic operations on the native VAX floating-point
14664 formats are not supported.
14667 It is not possible to slice a packed array.
14670 The names @code{True} and @code{False}, when not part of a qualified name,
14671 are interpreted as if implicitly prefixed by @code{Standard}, regardless of
14673 Should your program
14674 redefine these names in a package or procedure (at best a dubious practice),
14675 you will have to use fully qualified names to access their new definitions.
14678 @node Additions to Ada
14679 @subsubsection Additions to Ada
14680 @cindex Ada, deviations from
14682 As it does for other languages, @value{GDBN} makes certain generic
14683 extensions to Ada (@pxref{Expressions}):
14687 If the expression @var{E} is a variable residing in memory (typically
14688 a local variable or array element) and @var{N} is a positive integer,
14689 then @code{@var{E}@@@var{N}} displays the values of @var{E} and the
14690 @var{N}-1 adjacent variables following it in memory as an array. In
14691 Ada, this operator is generally not necessary, since its prime use is
14692 in displaying parts of an array, and slicing will usually do this in
14693 Ada. However, there are occasional uses when debugging programs in
14694 which certain debugging information has been optimized away.
14697 @code{@var{B}::@var{var}} means ``the variable named @var{var} that
14698 appears in function or file @var{B}.'' When @var{B} is a file name,
14699 you must typically surround it in single quotes.
14702 The expression @code{@{@var{type}@} @var{addr}} means ``the variable of type
14703 @var{type} that appears at address @var{addr}.''
14706 A name starting with @samp{$} is a convenience variable
14707 (@pxref{Convenience Vars}) or a machine register (@pxref{Registers}).
14710 In addition, @value{GDBN} provides a few other shortcuts and outright
14711 additions specific to Ada:
14715 The assignment statement is allowed as an expression, returning
14716 its right-hand operand as its value. Thus, you may enter
14719 (@value{GDBP}) set x := y + 3
14720 (@value{GDBP}) print A(tmp := y + 1)
14724 The semicolon is allowed as an ``operator,'' returning as its value
14725 the value of its right-hand operand.
14726 This allows, for example,
14727 complex conditional breaks:
14730 (@value{GDBP}) break f
14731 (@value{GDBP}) condition 1 (report(i); k += 1; A(k) > 100)
14735 Rather than use catenation and symbolic character names to introduce special
14736 characters into strings, one may instead use a special bracket notation,
14737 which is also used to print strings. A sequence of characters of the form
14738 @samp{["@var{XX}"]} within a string or character literal denotes the
14739 (single) character whose numeric encoding is @var{XX} in hexadecimal. The
14740 sequence of characters @samp{["""]} also denotes a single quotation mark
14741 in strings. For example,
14743 "One line.["0a"]Next line.["0a"]"
14746 contains an ASCII newline character (@code{Ada.Characters.Latin_1.LF})
14750 The subtype used as a prefix for the attributes @t{'Pos}, @t{'Min}, and
14751 @t{'Max} is optional (and is ignored in any case). For example, it is valid
14755 (@value{GDBP}) print 'max(x, y)
14759 When printing arrays, @value{GDBN} uses positional notation when the
14760 array has a lower bound of 1, and uses a modified named notation otherwise.
14761 For example, a one-dimensional array of three integers with a lower bound
14762 of 3 might print as
14769 That is, in contrast to valid Ada, only the first component has a @code{=>}
14773 You may abbreviate attributes in expressions with any unique,
14774 multi-character subsequence of
14775 their names (an exact match gets preference).
14776 For example, you may use @t{a'len}, @t{a'gth}, or @t{a'lh}
14777 in place of @t{a'length}.
14780 @cindex quoting Ada internal identifiers
14781 Since Ada is case-insensitive, the debugger normally maps identifiers you type
14782 to lower case. The GNAT compiler uses upper-case characters for
14783 some of its internal identifiers, which are normally of no interest to users.
14784 For the rare occasions when you actually have to look at them,
14785 enclose them in angle brackets to avoid the lower-case mapping.
14788 (@value{GDBP}) print <JMPBUF_SAVE>[0]
14792 Printing an object of class-wide type or dereferencing an
14793 access-to-class-wide value will display all the components of the object's
14794 specific type (as indicated by its run-time tag). Likewise, component
14795 selection on such a value will operate on the specific type of the
14800 @node Stopping Before Main Program
14801 @subsubsection Stopping at the Very Beginning
14803 @cindex breakpointing Ada elaboration code
14804 It is sometimes necessary to debug the program during elaboration, and
14805 before reaching the main procedure.
14806 As defined in the Ada Reference
14807 Manual, the elaboration code is invoked from a procedure called
14808 @code{adainit}. To run your program up to the beginning of
14809 elaboration, simply use the following two commands:
14810 @code{tbreak adainit} and @code{run}.
14813 @subsubsection Extensions for Ada Tasks
14814 @cindex Ada, tasking
14816 Support for Ada tasks is analogous to that for threads (@pxref{Threads}).
14817 @value{GDBN} provides the following task-related commands:
14822 This command shows a list of current Ada tasks, as in the following example:
14829 (@value{GDBP}) info tasks
14830 ID TID P-ID Pri State Name
14831 1 8088000 0 15 Child Activation Wait main_task
14832 2 80a4000 1 15 Accept Statement b
14833 3 809a800 1 15 Child Activation Wait a
14834 * 4 80ae800 3 15 Runnable c
14839 In this listing, the asterisk before the last task indicates it to be the
14840 task currently being inspected.
14844 Represents @value{GDBN}'s internal task number.
14850 The parent's task ID (@value{GDBN}'s internal task number).
14853 The base priority of the task.
14856 Current state of the task.
14860 The task has been created but has not been activated. It cannot be
14864 The task is not blocked for any reason known to Ada. (It may be waiting
14865 for a mutex, though.) It is conceptually "executing" in normal mode.
14868 The task is terminated, in the sense of ARM 9.3 (5). Any dependents
14869 that were waiting on terminate alternatives have been awakened and have
14870 terminated themselves.
14872 @item Child Activation Wait
14873 The task is waiting for created tasks to complete activation.
14875 @item Accept Statement
14876 The task is waiting on an accept or selective wait statement.
14878 @item Waiting on entry call
14879 The task is waiting on an entry call.
14881 @item Async Select Wait
14882 The task is waiting to start the abortable part of an asynchronous
14886 The task is waiting on a select statement with only a delay
14889 @item Child Termination Wait
14890 The task is sleeping having completed a master within itself, and is
14891 waiting for the tasks dependent on that master to become terminated or
14892 waiting on a terminate Phase.
14894 @item Wait Child in Term Alt
14895 The task is sleeping waiting for tasks on terminate alternatives to
14896 finish terminating.
14898 @item Accepting RV with @var{taskno}
14899 The task is accepting a rendez-vous with the task @var{taskno}.
14903 Name of the task in the program.
14907 @kindex info task @var{taskno}
14908 @item info task @var{taskno}
14909 This command shows detailled informations on the specified task, as in
14910 the following example:
14915 (@value{GDBP}) info tasks
14916 ID TID P-ID Pri State Name
14917 1 8077880 0 15 Child Activation Wait main_task
14918 * 2 807c468 1 15 Runnable task_1
14919 (@value{GDBP}) info task 2
14920 Ada Task: 0x807c468
14923 Parent: 1 (main_task)
14929 @kindex task@r{ (Ada)}
14930 @cindex current Ada task ID
14931 This command prints the ID of the current task.
14937 (@value{GDBP}) info tasks
14938 ID TID P-ID Pri State Name
14939 1 8077870 0 15 Child Activation Wait main_task
14940 * 2 807c458 1 15 Runnable t
14941 (@value{GDBP}) task
14942 [Current task is 2]
14945 @item task @var{taskno}
14946 @cindex Ada task switching
14947 This command is like the @code{thread @var{threadno}}
14948 command (@pxref{Threads}). It switches the context of debugging
14949 from the current task to the given task.
14955 (@value{GDBP}) info tasks
14956 ID TID P-ID Pri State Name
14957 1 8077870 0 15 Child Activation Wait main_task
14958 * 2 807c458 1 15 Runnable t
14959 (@value{GDBP}) task 1
14960 [Switching to task 1]
14961 #0 0x8067726 in pthread_cond_wait ()
14963 #0 0x8067726 in pthread_cond_wait ()
14964 #1 0x8056714 in system.os_interface.pthread_cond_wait ()
14965 #2 0x805cb63 in system.task_primitives.operations.sleep ()
14966 #3 0x806153e in system.tasking.stages.activate_tasks ()
14967 #4 0x804aacc in un () at un.adb:5
14970 @item break @var{linespec} task @var{taskno}
14971 @itemx break @var{linespec} task @var{taskno} if @dots{}
14972 @cindex breakpoints and tasks, in Ada
14973 @cindex task breakpoints, in Ada
14974 @kindex break @dots{} task @var{taskno}@r{ (Ada)}
14975 These commands are like the @code{break @dots{} thread @dots{}}
14976 command (@pxref{Thread Stops}).
14977 @var{linespec} specifies source lines, as described
14978 in @ref{Specify Location}.
14980 Use the qualifier @samp{task @var{taskno}} with a breakpoint command
14981 to specify that you only want @value{GDBN} to stop the program when a
14982 particular Ada task reaches this breakpoint. @var{taskno} is one of the
14983 numeric task identifiers assigned by @value{GDBN}, shown in the first
14984 column of the @samp{info tasks} display.
14986 If you do not specify @samp{task @var{taskno}} when you set a
14987 breakpoint, the breakpoint applies to @emph{all} tasks of your
14990 You can use the @code{task} qualifier on conditional breakpoints as
14991 well; in this case, place @samp{task @var{taskno}} before the
14992 breakpoint condition (before the @code{if}).
15000 (@value{GDBP}) info tasks
15001 ID TID P-ID Pri State Name
15002 1 140022020 0 15 Child Activation Wait main_task
15003 2 140045060 1 15 Accept/Select Wait t2
15004 3 140044840 1 15 Runnable t1
15005 * 4 140056040 1 15 Runnable t3
15006 (@value{GDBP}) b 15 task 2
15007 Breakpoint 5 at 0x120044cb0: file test_task_debug.adb, line 15.
15008 (@value{GDBP}) cont
15013 Breakpoint 5, test_task_debug () at test_task_debug.adb:15
15015 (@value{GDBP}) info tasks
15016 ID TID P-ID Pri State Name
15017 1 140022020 0 15 Child Activation Wait main_task
15018 * 2 140045060 1 15 Runnable t2
15019 3 140044840 1 15 Runnable t1
15020 4 140056040 1 15 Delay Sleep t3
15024 @node Ada Tasks and Core Files
15025 @subsubsection Tasking Support when Debugging Core Files
15026 @cindex Ada tasking and core file debugging
15028 When inspecting a core file, as opposed to debugging a live program,
15029 tasking support may be limited or even unavailable, depending on
15030 the platform being used.
15031 For instance, on x86-linux, the list of tasks is available, but task
15032 switching is not supported. On Tru64, however, task switching will work
15035 On certain platforms, including Tru64, the debugger needs to perform some
15036 memory writes in order to provide Ada tasking support. When inspecting
15037 a core file, this means that the core file must be opened with read-write
15038 privileges, using the command @samp{"set write on"} (@pxref{Patching}).
15039 Under these circumstances, you should make a backup copy of the core
15040 file before inspecting it with @value{GDBN}.
15042 @node Ravenscar Profile
15043 @subsubsection Tasking Support when using the Ravenscar Profile
15044 @cindex Ravenscar Profile
15046 The @dfn{Ravenscar Profile} is a subset of the Ada tasking features,
15047 specifically designed for systems with safety-critical real-time
15051 @kindex set ravenscar task-switching on
15052 @cindex task switching with program using Ravenscar Profile
15053 @item set ravenscar task-switching on
15054 Allows task switching when debugging a program that uses the Ravenscar
15055 Profile. This is the default.
15057 @kindex set ravenscar task-switching off
15058 @item set ravenscar task-switching off
15059 Turn off task switching when debugging a program that uses the Ravenscar
15060 Profile. This is mostly intended to disable the code that adds support
15061 for the Ravenscar Profile, in case a bug in either @value{GDBN} or in
15062 the Ravenscar runtime is preventing @value{GDBN} from working properly.
15063 To be effective, this command should be run before the program is started.
15065 @kindex show ravenscar task-switching
15066 @item show ravenscar task-switching
15067 Show whether it is possible to switch from task to task in a program
15068 using the Ravenscar Profile.
15073 @subsubsection Known Peculiarities of Ada Mode
15074 @cindex Ada, problems
15076 Besides the omissions listed previously (@pxref{Omissions from Ada}),
15077 we know of several problems with and limitations of Ada mode in
15079 some of which will be fixed with planned future releases of the debugger
15080 and the GNU Ada compiler.
15084 Static constants that the compiler chooses not to materialize as objects in
15085 storage are invisible to the debugger.
15088 Named parameter associations in function argument lists are ignored (the
15089 argument lists are treated as positional).
15092 Many useful library packages are currently invisible to the debugger.
15095 Fixed-point arithmetic, conversions, input, and output is carried out using
15096 floating-point arithmetic, and may give results that only approximate those on
15100 The GNAT compiler never generates the prefix @code{Standard} for any of
15101 the standard symbols defined by the Ada language. @value{GDBN} knows about
15102 this: it will strip the prefix from names when you use it, and will never
15103 look for a name you have so qualified among local symbols, nor match against
15104 symbols in other packages or subprograms. If you have
15105 defined entities anywhere in your program other than parameters and
15106 local variables whose simple names match names in @code{Standard},
15107 GNAT's lack of qualification here can cause confusion. When this happens,
15108 you can usually resolve the confusion
15109 by qualifying the problematic names with package
15110 @code{Standard} explicitly.
15113 Older versions of the compiler sometimes generate erroneous debugging
15114 information, resulting in the debugger incorrectly printing the value
15115 of affected entities. In some cases, the debugger is able to work
15116 around an issue automatically. In other cases, the debugger is able
15117 to work around the issue, but the work-around has to be specifically
15120 @kindex set ada trust-PAD-over-XVS
15121 @kindex show ada trust-PAD-over-XVS
15124 @item set ada trust-PAD-over-XVS on
15125 Configure GDB to strictly follow the GNAT encoding when computing the
15126 value of Ada entities, particularly when @code{PAD} and @code{PAD___XVS}
15127 types are involved (see @code{ada/exp_dbug.ads} in the GCC sources for
15128 a complete description of the encoding used by the GNAT compiler).
15129 This is the default.
15131 @item set ada trust-PAD-over-XVS off
15132 This is related to the encoding using by the GNAT compiler. If @value{GDBN}
15133 sometimes prints the wrong value for certain entities, changing @code{ada
15134 trust-PAD-over-XVS} to @code{off} activates a work-around which may fix
15135 the issue. It is always safe to set @code{ada trust-PAD-over-XVS} to
15136 @code{off}, but this incurs a slight performance penalty, so it is
15137 recommended to leave this setting to @code{on} unless necessary.
15141 @node Unsupported Languages
15142 @section Unsupported Languages
15144 @cindex unsupported languages
15145 @cindex minimal language
15146 In addition to the other fully-supported programming languages,
15147 @value{GDBN} also provides a pseudo-language, called @code{minimal}.
15148 It does not represent a real programming language, but provides a set
15149 of capabilities close to what the C or assembly languages provide.
15150 This should allow most simple operations to be performed while debugging
15151 an application that uses a language currently not supported by @value{GDBN}.
15153 If the language is set to @code{auto}, @value{GDBN} will automatically
15154 select this language if the current frame corresponds to an unsupported
15158 @chapter Examining the Symbol Table
15160 The commands described in this chapter allow you to inquire about the
15161 symbols (names of variables, functions and types) defined in your
15162 program. This information is inherent in the text of your program and
15163 does not change as your program executes. @value{GDBN} finds it in your
15164 program's symbol table, in the file indicated when you started @value{GDBN}
15165 (@pxref{File Options, ,Choosing Files}), or by one of the
15166 file-management commands (@pxref{Files, ,Commands to Specify Files}).
15168 @cindex symbol names
15169 @cindex names of symbols
15170 @cindex quoting names
15171 Occasionally, you may need to refer to symbols that contain unusual
15172 characters, which @value{GDBN} ordinarily treats as word delimiters. The
15173 most frequent case is in referring to static variables in other
15174 source files (@pxref{Variables,,Program Variables}). File names
15175 are recorded in object files as debugging symbols, but @value{GDBN} would
15176 ordinarily parse a typical file name, like @file{foo.c}, as the three words
15177 @samp{foo} @samp{.} @samp{c}. To allow @value{GDBN} to recognize
15178 @samp{foo.c} as a single symbol, enclose it in single quotes; for example,
15185 looks up the value of @code{x} in the scope of the file @file{foo.c}.
15188 @cindex case-insensitive symbol names
15189 @cindex case sensitivity in symbol names
15190 @kindex set case-sensitive
15191 @item set case-sensitive on
15192 @itemx set case-sensitive off
15193 @itemx set case-sensitive auto
15194 Normally, when @value{GDBN} looks up symbols, it matches their names
15195 with case sensitivity determined by the current source language.
15196 Occasionally, you may wish to control that. The command @code{set
15197 case-sensitive} lets you do that by specifying @code{on} for
15198 case-sensitive matches or @code{off} for case-insensitive ones. If
15199 you specify @code{auto}, case sensitivity is reset to the default
15200 suitable for the source language. The default is case-sensitive
15201 matches for all languages except for Fortran, for which the default is
15202 case-insensitive matches.
15204 @kindex show case-sensitive
15205 @item show case-sensitive
15206 This command shows the current setting of case sensitivity for symbols
15209 @kindex set print type methods
15210 @item set print type methods
15211 @itemx set print type methods on
15212 @itemx set print type methods off
15213 Normally, when @value{GDBN} prints a class, it displays any methods
15214 declared in that class. You can control this behavior either by
15215 passing the appropriate flag to @code{ptype}, or using @command{set
15216 print type methods}. Specifying @code{on} will cause @value{GDBN} to
15217 display the methods; this is the default. Specifying @code{off} will
15218 cause @value{GDBN} to omit the methods.
15220 @kindex show print type methods
15221 @item show print type methods
15222 This command shows the current setting of method display when printing
15225 @kindex set print type typedefs
15226 @item set print type typedefs
15227 @itemx set print type typedefs on
15228 @itemx set print type typedefs off
15230 Normally, when @value{GDBN} prints a class, it displays any typedefs
15231 defined in that class. You can control this behavior either by
15232 passing the appropriate flag to @code{ptype}, or using @command{set
15233 print type typedefs}. Specifying @code{on} will cause @value{GDBN} to
15234 display the typedef definitions; this is the default. Specifying
15235 @code{off} will cause @value{GDBN} to omit the typedef definitions.
15236 Note that this controls whether the typedef definition itself is
15237 printed, not whether typedef names are substituted when printing other
15240 @kindex show print type typedefs
15241 @item show print type typedefs
15242 This command shows the current setting of typedef display when
15245 @kindex info address
15246 @cindex address of a symbol
15247 @item info address @var{symbol}
15248 Describe where the data for @var{symbol} is stored. For a register
15249 variable, this says which register it is kept in. For a non-register
15250 local variable, this prints the stack-frame offset at which the variable
15253 Note the contrast with @samp{print &@var{symbol}}, which does not work
15254 at all for a register variable, and for a stack local variable prints
15255 the exact address of the current instantiation of the variable.
15257 @kindex info symbol
15258 @cindex symbol from address
15259 @cindex closest symbol and offset for an address
15260 @item info symbol @var{addr}
15261 Print the name of a symbol which is stored at the address @var{addr}.
15262 If no symbol is stored exactly at @var{addr}, @value{GDBN} prints the
15263 nearest symbol and an offset from it:
15266 (@value{GDBP}) info symbol 0x54320
15267 _initialize_vx + 396 in section .text
15271 This is the opposite of the @code{info address} command. You can use
15272 it to find out the name of a variable or a function given its address.
15274 For dynamically linked executables, the name of executable or shared
15275 library containing the symbol is also printed:
15278 (@value{GDBP}) info symbol 0x400225
15279 _start + 5 in section .text of /tmp/a.out
15280 (@value{GDBP}) info symbol 0x2aaaac2811cf
15281 __read_nocancel + 6 in section .text of /usr/lib64/libc.so.6
15285 @item whatis[/@var{flags}] [@var{arg}]
15286 Print the data type of @var{arg}, which can be either an expression
15287 or a name of a data type. With no argument, print the data type of
15288 @code{$}, the last value in the value history.
15290 If @var{arg} is an expression (@pxref{Expressions, ,Expressions}), it
15291 is not actually evaluated, and any side-effecting operations (such as
15292 assignments or function calls) inside it do not take place.
15294 If @var{arg} is a variable or an expression, @code{whatis} prints its
15295 literal type as it is used in the source code. If the type was
15296 defined using a @code{typedef}, @code{whatis} will @emph{not} print
15297 the data type underlying the @code{typedef}. If the type of the
15298 variable or the expression is a compound data type, such as
15299 @code{struct} or @code{class}, @code{whatis} never prints their
15300 fields or methods. It just prints the @code{struct}/@code{class}
15301 name (a.k.a.@: its @dfn{tag}). If you want to see the members of
15302 such a compound data type, use @code{ptype}.
15304 If @var{arg} is a type name that was defined using @code{typedef},
15305 @code{whatis} @dfn{unrolls} only one level of that @code{typedef}.
15306 Unrolling means that @code{whatis} will show the underlying type used
15307 in the @code{typedef} declaration of @var{arg}. However, if that
15308 underlying type is also a @code{typedef}, @code{whatis} will not
15311 For C code, the type names may also have the form @samp{class
15312 @var{class-name}}, @samp{struct @var{struct-tag}}, @samp{union
15313 @var{union-tag}} or @samp{enum @var{enum-tag}}.
15315 @var{flags} can be used to modify how the type is displayed.
15316 Available flags are:
15320 Display in ``raw'' form. Normally, @value{GDBN} substitutes template
15321 parameters and typedefs defined in a class when printing the class'
15322 members. The @code{/r} flag disables this.
15325 Do not print methods defined in the class.
15328 Print methods defined in the class. This is the default, but the flag
15329 exists in case you change the default with @command{set print type methods}.
15332 Do not print typedefs defined in the class. Note that this controls
15333 whether the typedef definition itself is printed, not whether typedef
15334 names are substituted when printing other types.
15337 Print typedefs defined in the class. This is the default, but the flag
15338 exists in case you change the default with @command{set print type typedefs}.
15342 @item ptype[/@var{flags}] [@var{arg}]
15343 @code{ptype} accepts the same arguments as @code{whatis}, but prints a
15344 detailed description of the type, instead of just the name of the type.
15345 @xref{Expressions, ,Expressions}.
15347 Contrary to @code{whatis}, @code{ptype} always unrolls any
15348 @code{typedef}s in its argument declaration, whether the argument is
15349 a variable, expression, or a data type. This means that @code{ptype}
15350 of a variable or an expression will not print literally its type as
15351 present in the source code---use @code{whatis} for that. @code{typedef}s at
15352 the pointer or reference targets are also unrolled. Only @code{typedef}s of
15353 fields, methods and inner @code{class typedef}s of @code{struct}s,
15354 @code{class}es and @code{union}s are not unrolled even with @code{ptype}.
15356 For example, for this variable declaration:
15359 typedef double real_t;
15360 struct complex @{ real_t real; double imag; @};
15361 typedef struct complex complex_t;
15363 real_t *real_pointer_var;
15367 the two commands give this output:
15371 (@value{GDBP}) whatis var
15373 (@value{GDBP}) ptype var
15374 type = struct complex @{
15378 (@value{GDBP}) whatis complex_t
15379 type = struct complex
15380 (@value{GDBP}) whatis struct complex
15381 type = struct complex
15382 (@value{GDBP}) ptype struct complex
15383 type = struct complex @{
15387 (@value{GDBP}) whatis real_pointer_var
15389 (@value{GDBP}) ptype real_pointer_var
15395 As with @code{whatis}, using @code{ptype} without an argument refers to
15396 the type of @code{$}, the last value in the value history.
15398 @cindex incomplete type
15399 Sometimes, programs use opaque data types or incomplete specifications
15400 of complex data structure. If the debug information included in the
15401 program does not allow @value{GDBN} to display a full declaration of
15402 the data type, it will say @samp{<incomplete type>}. For example,
15403 given these declarations:
15407 struct foo *fooptr;
15411 but no definition for @code{struct foo} itself, @value{GDBN} will say:
15414 (@value{GDBP}) ptype foo
15415 $1 = <incomplete type>
15419 ``Incomplete type'' is C terminology for data types that are not
15420 completely specified.
15423 @item info types @var{regexp}
15425 Print a brief description of all types whose names match the regular
15426 expression @var{regexp} (or all types in your program, if you supply
15427 no argument). Each complete typename is matched as though it were a
15428 complete line; thus, @samp{i type value} gives information on all
15429 types in your program whose names include the string @code{value}, but
15430 @samp{i type ^value$} gives information only on types whose complete
15431 name is @code{value}.
15433 This command differs from @code{ptype} in two ways: first, like
15434 @code{whatis}, it does not print a detailed description; second, it
15435 lists all source files where a type is defined.
15437 @kindex info type-printers
15438 @item info type-printers
15439 Versions of @value{GDBN} that ship with Python scripting enabled may
15440 have ``type printers'' available. When using @command{ptype} or
15441 @command{whatis}, these printers are consulted when the name of a type
15442 is needed. @xref{Type Printing API}, for more information on writing
15445 @code{info type-printers} displays all the available type printers.
15447 @kindex enable type-printer
15448 @kindex disable type-printer
15449 @item enable type-printer @var{name}@dots{}
15450 @item disable type-printer @var{name}@dots{}
15451 These commands can be used to enable or disable type printers.
15454 @cindex local variables
15455 @item info scope @var{location}
15456 List all the variables local to a particular scope. This command
15457 accepts a @var{location} argument---a function name, a source line, or
15458 an address preceded by a @samp{*}, and prints all the variables local
15459 to the scope defined by that location. (@xref{Specify Location}, for
15460 details about supported forms of @var{location}.) For example:
15463 (@value{GDBP}) @b{info scope command_line_handler}
15464 Scope for command_line_handler:
15465 Symbol rl is an argument at stack/frame offset 8, length 4.
15466 Symbol linebuffer is in static storage at address 0x150a18, length 4.
15467 Symbol linelength is in static storage at address 0x150a1c, length 4.
15468 Symbol p is a local variable in register $esi, length 4.
15469 Symbol p1 is a local variable in register $ebx, length 4.
15470 Symbol nline is a local variable in register $edx, length 4.
15471 Symbol repeat is a local variable at frame offset -8, length 4.
15475 This command is especially useful for determining what data to collect
15476 during a @dfn{trace experiment}, see @ref{Tracepoint Actions,
15479 @kindex info source
15481 Show information about the current source file---that is, the source file for
15482 the function containing the current point of execution:
15485 the name of the source file, and the directory containing it,
15487 the directory it was compiled in,
15489 its length, in lines,
15491 which programming language it is written in,
15493 whether the executable includes debugging information for that file, and
15494 if so, what format the information is in (e.g., STABS, Dwarf 2, etc.), and
15496 whether the debugging information includes information about
15497 preprocessor macros.
15501 @kindex info sources
15503 Print the names of all source files in your program for which there is
15504 debugging information, organized into two lists: files whose symbols
15505 have already been read, and files whose symbols will be read when needed.
15507 @kindex info functions
15508 @item info functions
15509 Print the names and data types of all defined functions.
15511 @item info functions @var{regexp}
15512 Print the names and data types of all defined functions
15513 whose names contain a match for regular expression @var{regexp}.
15514 Thus, @samp{info fun step} finds all functions whose names
15515 include @code{step}; @samp{info fun ^step} finds those whose names
15516 start with @code{step}. If a function name contains characters
15517 that conflict with the regular expression language (e.g.@:
15518 @samp{operator*()}), they may be quoted with a backslash.
15520 @kindex info variables
15521 @item info variables
15522 Print the names and data types of all variables that are defined
15523 outside of functions (i.e.@: excluding local variables).
15525 @item info variables @var{regexp}
15526 Print the names and data types of all variables (except for local
15527 variables) whose names contain a match for regular expression
15530 @kindex info classes
15531 @cindex Objective-C, classes and selectors
15533 @itemx info classes @var{regexp}
15534 Display all Objective-C classes in your program, or
15535 (with the @var{regexp} argument) all those matching a particular regular
15538 @kindex info selectors
15539 @item info selectors
15540 @itemx info selectors @var{regexp}
15541 Display all Objective-C selectors in your program, or
15542 (with the @var{regexp} argument) all those matching a particular regular
15546 This was never implemented.
15547 @kindex info methods
15549 @itemx info methods @var{regexp}
15550 The @code{info methods} command permits the user to examine all defined
15551 methods within C@t{++} program, or (with the @var{regexp} argument) a
15552 specific set of methods found in the various C@t{++} classes. Many
15553 C@t{++} classes provide a large number of methods. Thus, the output
15554 from the @code{ptype} command can be overwhelming and hard to use. The
15555 @code{info-methods} command filters the methods, printing only those
15556 which match the regular-expression @var{regexp}.
15559 @cindex opaque data types
15560 @kindex set opaque-type-resolution
15561 @item set opaque-type-resolution on
15562 Tell @value{GDBN} to resolve opaque types. An opaque type is a type
15563 declared as a pointer to a @code{struct}, @code{class}, or
15564 @code{union}---for example, @code{struct MyType *}---that is used in one
15565 source file although the full declaration of @code{struct MyType} is in
15566 another source file. The default is on.
15568 A change in the setting of this subcommand will not take effect until
15569 the next time symbols for a file are loaded.
15571 @item set opaque-type-resolution off
15572 Tell @value{GDBN} not to resolve opaque types. In this case, the type
15573 is printed as follows:
15575 @{<no data fields>@}
15578 @kindex show opaque-type-resolution
15579 @item show opaque-type-resolution
15580 Show whether opaque types are resolved or not.
15582 @kindex maint print symbols
15583 @cindex symbol dump
15584 @kindex maint print psymbols
15585 @cindex partial symbol dump
15586 @item maint print symbols @var{filename}
15587 @itemx maint print psymbols @var{filename}
15588 @itemx maint print msymbols @var{filename}
15589 Write a dump of debugging symbol data into the file @var{filename}.
15590 These commands are used to debug the @value{GDBN} symbol-reading code. Only
15591 symbols with debugging data are included. If you use @samp{maint print
15592 symbols}, @value{GDBN} includes all the symbols for which it has already
15593 collected full details: that is, @var{filename} reflects symbols for
15594 only those files whose symbols @value{GDBN} has read. You can use the
15595 command @code{info sources} to find out which files these are. If you
15596 use @samp{maint print psymbols} instead, the dump shows information about
15597 symbols that @value{GDBN} only knows partially---that is, symbols defined in
15598 files that @value{GDBN} has skimmed, but not yet read completely. Finally,
15599 @samp{maint print msymbols} dumps just the minimal symbol information
15600 required for each object file from which @value{GDBN} has read some symbols.
15601 @xref{Files, ,Commands to Specify Files}, for a discussion of how
15602 @value{GDBN} reads symbols (in the description of @code{symbol-file}).
15604 @kindex maint info symtabs
15605 @kindex maint info psymtabs
15606 @cindex listing @value{GDBN}'s internal symbol tables
15607 @cindex symbol tables, listing @value{GDBN}'s internal
15608 @cindex full symbol tables, listing @value{GDBN}'s internal
15609 @cindex partial symbol tables, listing @value{GDBN}'s internal
15610 @item maint info symtabs @r{[} @var{regexp} @r{]}
15611 @itemx maint info psymtabs @r{[} @var{regexp} @r{]}
15613 List the @code{struct symtab} or @code{struct partial_symtab}
15614 structures whose names match @var{regexp}. If @var{regexp} is not
15615 given, list them all. The output includes expressions which you can
15616 copy into a @value{GDBN} debugging this one to examine a particular
15617 structure in more detail. For example:
15620 (@value{GDBP}) maint info psymtabs dwarf2read
15621 @{ objfile /home/gnu/build/gdb/gdb
15622 ((struct objfile *) 0x82e69d0)
15623 @{ psymtab /home/gnu/src/gdb/dwarf2read.c
15624 ((struct partial_symtab *) 0x8474b10)
15627 text addresses 0x814d3c8 -- 0x8158074
15628 globals (* (struct partial_symbol **) 0x8507a08 @@ 9)
15629 statics (* (struct partial_symbol **) 0x40e95b78 @@ 2882)
15630 dependencies (none)
15633 (@value{GDBP}) maint info symtabs
15637 We see that there is one partial symbol table whose filename contains
15638 the string @samp{dwarf2read}, belonging to the @samp{gdb} executable;
15639 and we see that @value{GDBN} has not read in any symtabs yet at all.
15640 If we set a breakpoint on a function, that will cause @value{GDBN} to
15641 read the symtab for the compilation unit containing that function:
15644 (@value{GDBP}) break dwarf2_psymtab_to_symtab
15645 Breakpoint 1 at 0x814e5da: file /home/gnu/src/gdb/dwarf2read.c,
15647 (@value{GDBP}) maint info symtabs
15648 @{ objfile /home/gnu/build/gdb/gdb
15649 ((struct objfile *) 0x82e69d0)
15650 @{ symtab /home/gnu/src/gdb/dwarf2read.c
15651 ((struct symtab *) 0x86c1f38)
15654 blockvector ((struct blockvector *) 0x86c1bd0) (primary)
15655 linetable ((struct linetable *) 0x8370fa0)
15656 debugformat DWARF 2
15665 @chapter Altering Execution
15667 Once you think you have found an error in your program, you might want to
15668 find out for certain whether correcting the apparent error would lead to
15669 correct results in the rest of the run. You can find the answer by
15670 experiment, using the @value{GDBN} features for altering execution of the
15673 For example, you can store new values into variables or memory
15674 locations, give your program a signal, restart it at a different
15675 address, or even return prematurely from a function.
15678 * Assignment:: Assignment to variables
15679 * Jumping:: Continuing at a different address
15680 * Signaling:: Giving your program a signal
15681 * Returning:: Returning from a function
15682 * Calling:: Calling your program's functions
15683 * Patching:: Patching your program
15687 @section Assignment to Variables
15690 @cindex setting variables
15691 To alter the value of a variable, evaluate an assignment expression.
15692 @xref{Expressions, ,Expressions}. For example,
15699 stores the value 4 into the variable @code{x}, and then prints the
15700 value of the assignment expression (which is 4).
15701 @xref{Languages, ,Using @value{GDBN} with Different Languages}, for more
15702 information on operators in supported languages.
15704 @kindex set variable
15705 @cindex variables, setting
15706 If you are not interested in seeing the value of the assignment, use the
15707 @code{set} command instead of the @code{print} command. @code{set} is
15708 really the same as @code{print} except that the expression's value is
15709 not printed and is not put in the value history (@pxref{Value History,
15710 ,Value History}). The expression is evaluated only for its effects.
15712 If the beginning of the argument string of the @code{set} command
15713 appears identical to a @code{set} subcommand, use the @code{set
15714 variable} command instead of just @code{set}. This command is identical
15715 to @code{set} except for its lack of subcommands. For example, if your
15716 program has a variable @code{width}, you get an error if you try to set
15717 a new value with just @samp{set width=13}, because @value{GDBN} has the
15718 command @code{set width}:
15721 (@value{GDBP}) whatis width
15723 (@value{GDBP}) p width
15725 (@value{GDBP}) set width=47
15726 Invalid syntax in expression.
15730 The invalid expression, of course, is @samp{=47}. In
15731 order to actually set the program's variable @code{width}, use
15734 (@value{GDBP}) set var width=47
15737 Because the @code{set} command has many subcommands that can conflict
15738 with the names of program variables, it is a good idea to use the
15739 @code{set variable} command instead of just @code{set}. For example, if
15740 your program has a variable @code{g}, you run into problems if you try
15741 to set a new value with just @samp{set g=4}, because @value{GDBN} has
15742 the command @code{set gnutarget}, abbreviated @code{set g}:
15746 (@value{GDBP}) whatis g
15750 (@value{GDBP}) set g=4
15754 The program being debugged has been started already.
15755 Start it from the beginning? (y or n) y
15756 Starting program: /home/smith/cc_progs/a.out
15757 "/home/smith/cc_progs/a.out": can't open to read symbols:
15758 Invalid bfd target.
15759 (@value{GDBP}) show g
15760 The current BFD target is "=4".
15765 The program variable @code{g} did not change, and you silently set the
15766 @code{gnutarget} to an invalid value. In order to set the variable
15770 (@value{GDBP}) set var g=4
15773 @value{GDBN} allows more implicit conversions in assignments than C; you can
15774 freely store an integer value into a pointer variable or vice versa,
15775 and you can convert any structure to any other structure that is the
15776 same length or shorter.
15777 @comment FIXME: how do structs align/pad in these conversions?
15778 @comment /doc@cygnus.com 18dec1990
15780 To store values into arbitrary places in memory, use the @samp{@{@dots{}@}}
15781 construct to generate a value of specified type at a specified address
15782 (@pxref{Expressions, ,Expressions}). For example, @code{@{int@}0x83040} refers
15783 to memory location @code{0x83040} as an integer (which implies a certain size
15784 and representation in memory), and
15787 set @{int@}0x83040 = 4
15791 stores the value 4 into that memory location.
15794 @section Continuing at a Different Address
15796 Ordinarily, when you continue your program, you do so at the place where
15797 it stopped, with the @code{continue} command. You can instead continue at
15798 an address of your own choosing, with the following commands:
15802 @kindex j @r{(@code{jump})}
15803 @item jump @var{linespec}
15804 @itemx j @var{linespec}
15805 @itemx jump @var{location}
15806 @itemx j @var{location}
15807 Resume execution at line @var{linespec} or at address given by
15808 @var{location}. Execution stops again immediately if there is a
15809 breakpoint there. @xref{Specify Location}, for a description of the
15810 different forms of @var{linespec} and @var{location}. It is common
15811 practice to use the @code{tbreak} command in conjunction with
15812 @code{jump}. @xref{Set Breaks, ,Setting Breakpoints}.
15814 The @code{jump} command does not change the current stack frame, or
15815 the stack pointer, or the contents of any memory location or any
15816 register other than the program counter. If line @var{linespec} is in
15817 a different function from the one currently executing, the results may
15818 be bizarre if the two functions expect different patterns of arguments or
15819 of local variables. For this reason, the @code{jump} command requests
15820 confirmation if the specified line is not in the function currently
15821 executing. However, even bizarre results are predictable if you are
15822 well acquainted with the machine-language code of your program.
15825 @c Doesn't work on HP-UX; have to set $pcoqh and $pcoqt.
15826 On many systems, you can get much the same effect as the @code{jump}
15827 command by storing a new value into the register @code{$pc}. The
15828 difference is that this does not start your program running; it only
15829 changes the address of where it @emph{will} run when you continue. For
15837 makes the next @code{continue} command or stepping command execute at
15838 address @code{0x485}, rather than at the address where your program stopped.
15839 @xref{Continuing and Stepping, ,Continuing and Stepping}.
15841 The most common occasion to use the @code{jump} command is to back
15842 up---perhaps with more breakpoints set---over a portion of a program
15843 that has already executed, in order to examine its execution in more
15848 @section Giving your Program a Signal
15849 @cindex deliver a signal to a program
15853 @item signal @var{signal}
15854 Resume execution where your program stopped, but immediately give it the
15855 signal @var{signal}. @var{signal} can be the name or the number of a
15856 signal. For example, on many systems @code{signal 2} and @code{signal
15857 SIGINT} are both ways of sending an interrupt signal.
15859 Alternatively, if @var{signal} is zero, continue execution without
15860 giving a signal. This is useful when your program stopped on account of
15861 a signal and would ordinarily see the signal when resumed with the
15862 @code{continue} command; @samp{signal 0} causes it to resume without a
15865 @code{signal} does not repeat when you press @key{RET} a second time
15866 after executing the command.
15870 Invoking the @code{signal} command is not the same as invoking the
15871 @code{kill} utility from the shell. Sending a signal with @code{kill}
15872 causes @value{GDBN} to decide what to do with the signal depending on
15873 the signal handling tables (@pxref{Signals}). The @code{signal} command
15874 passes the signal directly to your program.
15878 @section Returning from a Function
15881 @cindex returning from a function
15884 @itemx return @var{expression}
15885 You can cancel execution of a function call with the @code{return}
15886 command. If you give an
15887 @var{expression} argument, its value is used as the function's return
15891 When you use @code{return}, @value{GDBN} discards the selected stack frame
15892 (and all frames within it). You can think of this as making the
15893 discarded frame return prematurely. If you wish to specify a value to
15894 be returned, give that value as the argument to @code{return}.
15896 This pops the selected stack frame (@pxref{Selection, ,Selecting a
15897 Frame}), and any other frames inside of it, leaving its caller as the
15898 innermost remaining frame. That frame becomes selected. The
15899 specified value is stored in the registers used for returning values
15902 The @code{return} command does not resume execution; it leaves the
15903 program stopped in the state that would exist if the function had just
15904 returned. In contrast, the @code{finish} command (@pxref{Continuing
15905 and Stepping, ,Continuing and Stepping}) resumes execution until the
15906 selected stack frame returns naturally.
15908 @value{GDBN} needs to know how the @var{expression} argument should be set for
15909 the inferior. The concrete registers assignment depends on the OS ABI and the
15910 type being returned by the selected stack frame. For example it is common for
15911 OS ABI to return floating point values in FPU registers while integer values in
15912 CPU registers. Still some ABIs return even floating point values in CPU
15913 registers. Larger integer widths (such as @code{long long int}) also have
15914 specific placement rules. @value{GDBN} already knows the OS ABI from its
15915 current target so it needs to find out also the type being returned to make the
15916 assignment into the right register(s).
15918 Normally, the selected stack frame has debug info. @value{GDBN} will always
15919 use the debug info instead of the implicit type of @var{expression} when the
15920 debug info is available. For example, if you type @kbd{return -1}, and the
15921 function in the current stack frame is declared to return a @code{long long
15922 int}, @value{GDBN} transparently converts the implicit @code{int} value of -1
15923 into a @code{long long int}:
15926 Breakpoint 1, func () at gdb.base/return-nodebug.c:29
15928 (@value{GDBP}) return -1
15929 Make func return now? (y or n) y
15930 #0 0x004004f6 in main () at gdb.base/return-nodebug.c:43
15931 43 printf ("result=%lld\n", func ());
15935 However, if the selected stack frame does not have a debug info, e.g., if the
15936 function was compiled without debug info, @value{GDBN} has to find out the type
15937 to return from user. Specifying a different type by mistake may set the value
15938 in different inferior registers than the caller code expects. For example,
15939 typing @kbd{return -1} with its implicit type @code{int} would set only a part
15940 of a @code{long long int} result for a debug info less function (on 32-bit
15941 architectures). Therefore the user is required to specify the return type by
15942 an appropriate cast explicitly:
15945 Breakpoint 2, 0x0040050b in func ()
15946 (@value{GDBP}) return -1
15947 Return value type not available for selected stack frame.
15948 Please use an explicit cast of the value to return.
15949 (@value{GDBP}) return (long long int) -1
15950 Make selected stack frame return now? (y or n) y
15951 #0 0x00400526 in main ()
15956 @section Calling Program Functions
15959 @cindex calling functions
15960 @cindex inferior functions, calling
15961 @item print @var{expr}
15962 Evaluate the expression @var{expr} and display the resulting value.
15963 @var{expr} may include calls to functions in the program being
15967 @item call @var{expr}
15968 Evaluate the expression @var{expr} without displaying @code{void}
15971 You can use this variant of the @code{print} command if you want to
15972 execute a function from your program that does not return anything
15973 (a.k.a.@: @dfn{a void function}), but without cluttering the output
15974 with @code{void} returned values that @value{GDBN} will otherwise
15975 print. If the result is not void, it is printed and saved in the
15979 It is possible for the function you call via the @code{print} or
15980 @code{call} command to generate a signal (e.g., if there's a bug in
15981 the function, or if you passed it incorrect arguments). What happens
15982 in that case is controlled by the @code{set unwindonsignal} command.
15984 Similarly, with a C@t{++} program it is possible for the function you
15985 call via the @code{print} or @code{call} command to generate an
15986 exception that is not handled due to the constraints of the dummy
15987 frame. In this case, any exception that is raised in the frame, but has
15988 an out-of-frame exception handler will not be found. GDB builds a
15989 dummy-frame for the inferior function call, and the unwinder cannot
15990 seek for exception handlers outside of this dummy-frame. What happens
15991 in that case is controlled by the
15992 @code{set unwind-on-terminating-exception} command.
15995 @item set unwindonsignal
15996 @kindex set unwindonsignal
15997 @cindex unwind stack in called functions
15998 @cindex call dummy stack unwinding
15999 Set unwinding of the stack if a signal is received while in a function
16000 that @value{GDBN} called in the program being debugged. If set to on,
16001 @value{GDBN} unwinds the stack it created for the call and restores
16002 the context to what it was before the call. If set to off (the
16003 default), @value{GDBN} stops in the frame where the signal was
16006 @item show unwindonsignal
16007 @kindex show unwindonsignal
16008 Show the current setting of stack unwinding in the functions called by
16011 @item set unwind-on-terminating-exception
16012 @kindex set unwind-on-terminating-exception
16013 @cindex unwind stack in called functions with unhandled exceptions
16014 @cindex call dummy stack unwinding on unhandled exception.
16015 Set unwinding of the stack if a C@t{++} exception is raised, but left
16016 unhandled while in a function that @value{GDBN} called in the program being
16017 debugged. If set to on (the default), @value{GDBN} unwinds the stack
16018 it created for the call and restores the context to what it was before
16019 the call. If set to off, @value{GDBN} the exception is delivered to
16020 the default C@t{++} exception handler and the inferior terminated.
16022 @item show unwind-on-terminating-exception
16023 @kindex show unwind-on-terminating-exception
16024 Show the current setting of stack unwinding in the functions called by
16029 @cindex weak alias functions
16030 Sometimes, a function you wish to call is actually a @dfn{weak alias}
16031 for another function. In such case, @value{GDBN} might not pick up
16032 the type information, including the types of the function arguments,
16033 which causes @value{GDBN} to call the inferior function incorrectly.
16034 As a result, the called function will function erroneously and may
16035 even crash. A solution to that is to use the name of the aliased
16039 @section Patching Programs
16041 @cindex patching binaries
16042 @cindex writing into executables
16043 @cindex writing into corefiles
16045 By default, @value{GDBN} opens the file containing your program's
16046 executable code (or the corefile) read-only. This prevents accidental
16047 alterations to machine code; but it also prevents you from intentionally
16048 patching your program's binary.
16050 If you'd like to be able to patch the binary, you can specify that
16051 explicitly with the @code{set write} command. For example, you might
16052 want to turn on internal debugging flags, or even to make emergency
16058 @itemx set write off
16059 If you specify @samp{set write on}, @value{GDBN} opens executable and
16060 core files for both reading and writing; if you specify @kbd{set write
16061 off} (the default), @value{GDBN} opens them read-only.
16063 If you have already loaded a file, you must load it again (using the
16064 @code{exec-file} or @code{core-file} command) after changing @code{set
16065 write}, for your new setting to take effect.
16069 Display whether executable files and core files are opened for writing
16070 as well as reading.
16074 @chapter @value{GDBN} Files
16076 @value{GDBN} needs to know the file name of the program to be debugged,
16077 both in order to read its symbol table and in order to start your
16078 program. To debug a core dump of a previous run, you must also tell
16079 @value{GDBN} the name of the core dump file.
16082 * Files:: Commands to specify files
16083 * Separate Debug Files:: Debugging information in separate files
16084 * MiniDebugInfo:: Debugging information in a special section
16085 * Index Files:: Index files speed up GDB
16086 * Symbol Errors:: Errors reading symbol files
16087 * Data Files:: GDB data files
16091 @section Commands to Specify Files
16093 @cindex symbol table
16094 @cindex core dump file
16096 You may want to specify executable and core dump file names. The usual
16097 way to do this is at start-up time, using the arguments to
16098 @value{GDBN}'s start-up commands (@pxref{Invocation, , Getting In and
16099 Out of @value{GDBN}}).
16101 Occasionally it is necessary to change to a different file during a
16102 @value{GDBN} session. Or you may run @value{GDBN} and forget to
16103 specify a file you want to use. Or you are debugging a remote target
16104 via @code{gdbserver} (@pxref{Server, file, Using the @code{gdbserver}
16105 Program}). In these situations the @value{GDBN} commands to specify
16106 new files are useful.
16109 @cindex executable file
16111 @item file @var{filename}
16112 Use @var{filename} as the program to be debugged. It is read for its
16113 symbols and for the contents of pure memory. It is also the program
16114 executed when you use the @code{run} command. If you do not specify a
16115 directory and the file is not found in the @value{GDBN} working directory,
16116 @value{GDBN} uses the environment variable @code{PATH} as a list of
16117 directories to search, just as the shell does when looking for a program
16118 to run. You can change the value of this variable, for both @value{GDBN}
16119 and your program, using the @code{path} command.
16121 @cindex unlinked object files
16122 @cindex patching object files
16123 You can load unlinked object @file{.o} files into @value{GDBN} using
16124 the @code{file} command. You will not be able to ``run'' an object
16125 file, but you can disassemble functions and inspect variables. Also,
16126 if the underlying BFD functionality supports it, you could use
16127 @kbd{gdb -write} to patch object files using this technique. Note
16128 that @value{GDBN} can neither interpret nor modify relocations in this
16129 case, so branches and some initialized variables will appear to go to
16130 the wrong place. But this feature is still handy from time to time.
16133 @code{file} with no argument makes @value{GDBN} discard any information it
16134 has on both executable file and the symbol table.
16137 @item exec-file @r{[} @var{filename} @r{]}
16138 Specify that the program to be run (but not the symbol table) is found
16139 in @var{filename}. @value{GDBN} searches the environment variable @code{PATH}
16140 if necessary to locate your program. Omitting @var{filename} means to
16141 discard information on the executable file.
16143 @kindex symbol-file
16144 @item symbol-file @r{[} @var{filename} @r{]}
16145 Read symbol table information from file @var{filename}. @code{PATH} is
16146 searched when necessary. Use the @code{file} command to get both symbol
16147 table and program to run from the same file.
16149 @code{symbol-file} with no argument clears out @value{GDBN} information on your
16150 program's symbol table.
16152 The @code{symbol-file} command causes @value{GDBN} to forget the contents of
16153 some breakpoints and auto-display expressions. This is because they may
16154 contain pointers to the internal data recording symbols and data types,
16155 which are part of the old symbol table data being discarded inside
16158 @code{symbol-file} does not repeat if you press @key{RET} again after
16161 When @value{GDBN} is configured for a particular environment, it
16162 understands debugging information in whatever format is the standard
16163 generated for that environment; you may use either a @sc{gnu} compiler, or
16164 other compilers that adhere to the local conventions.
16165 Best results are usually obtained from @sc{gnu} compilers; for example,
16166 using @code{@value{NGCC}} you can generate debugging information for
16169 For most kinds of object files, with the exception of old SVR3 systems
16170 using COFF, the @code{symbol-file} command does not normally read the
16171 symbol table in full right away. Instead, it scans the symbol table
16172 quickly to find which source files and which symbols are present. The
16173 details are read later, one source file at a time, as they are needed.
16175 The purpose of this two-stage reading strategy is to make @value{GDBN}
16176 start up faster. For the most part, it is invisible except for
16177 occasional pauses while the symbol table details for a particular source
16178 file are being read. (The @code{set verbose} command can turn these
16179 pauses into messages if desired. @xref{Messages/Warnings, ,Optional
16180 Warnings and Messages}.)
16182 We have not implemented the two-stage strategy for COFF yet. When the
16183 symbol table is stored in COFF format, @code{symbol-file} reads the
16184 symbol table data in full right away. Note that ``stabs-in-COFF''
16185 still does the two-stage strategy, since the debug info is actually
16189 @cindex reading symbols immediately
16190 @cindex symbols, reading immediately
16191 @item symbol-file @r{[} -readnow @r{]} @var{filename}
16192 @itemx file @r{[} -readnow @r{]} @var{filename}
16193 You can override the @value{GDBN} two-stage strategy for reading symbol
16194 tables by using the @samp{-readnow} option with any of the commands that
16195 load symbol table information, if you want to be sure @value{GDBN} has the
16196 entire symbol table available.
16198 @c FIXME: for now no mention of directories, since this seems to be in
16199 @c flux. 13mar1992 status is that in theory GDB would look either in
16200 @c current dir or in same dir as myprog; but issues like competing
16201 @c GDB's, or clutter in system dirs, mean that in practice right now
16202 @c only current dir is used. FFish says maybe a special GDB hierarchy
16203 @c (eg rooted in val of env var GDBSYMS) could exist for mappable symbol
16207 @item core-file @r{[}@var{filename}@r{]}
16209 Specify the whereabouts of a core dump file to be used as the ``contents
16210 of memory''. Traditionally, core files contain only some parts of the
16211 address space of the process that generated them; @value{GDBN} can access the
16212 executable file itself for other parts.
16214 @code{core-file} with no argument specifies that no core file is
16217 Note that the core file is ignored when your program is actually running
16218 under @value{GDBN}. So, if you have been running your program and you
16219 wish to debug a core file instead, you must kill the subprocess in which
16220 the program is running. To do this, use the @code{kill} command
16221 (@pxref{Kill Process, ,Killing the Child Process}).
16223 @kindex add-symbol-file
16224 @cindex dynamic linking
16225 @item add-symbol-file @var{filename} @var{address}
16226 @itemx add-symbol-file @var{filename} @var{address} @r{[} -readnow @r{]}
16227 @itemx add-symbol-file @var{filename} @var{address} -s @var{section} @var{address} @dots{}
16228 The @code{add-symbol-file} command reads additional symbol table
16229 information from the file @var{filename}. You would use this command
16230 when @var{filename} has been dynamically loaded (by some other means)
16231 into the program that is running. @var{address} should be the memory
16232 address at which the file has been loaded; @value{GDBN} cannot figure
16233 this out for itself. You can additionally specify an arbitrary number
16234 of @samp{-s @var{section} @var{address}} pairs, to give an explicit
16235 section name and base address for that section. You can specify any
16236 @var{address} as an expression.
16238 The symbol table of the file @var{filename} is added to the symbol table
16239 originally read with the @code{symbol-file} command. You can use the
16240 @code{add-symbol-file} command any number of times; the new symbol data
16241 thus read keeps adding to the old. To discard all old symbol data
16242 instead, use the @code{symbol-file} command without any arguments.
16244 @cindex relocatable object files, reading symbols from
16245 @cindex object files, relocatable, reading symbols from
16246 @cindex reading symbols from relocatable object files
16247 @cindex symbols, reading from relocatable object files
16248 @cindex @file{.o} files, reading symbols from
16249 Although @var{filename} is typically a shared library file, an
16250 executable file, or some other object file which has been fully
16251 relocated for loading into a process, you can also load symbolic
16252 information from relocatable @file{.o} files, as long as:
16256 the file's symbolic information refers only to linker symbols defined in
16257 that file, not to symbols defined by other object files,
16259 every section the file's symbolic information refers to has actually
16260 been loaded into the inferior, as it appears in the file, and
16262 you can determine the address at which every section was loaded, and
16263 provide these to the @code{add-symbol-file} command.
16267 Some embedded operating systems, like Sun Chorus and VxWorks, can load
16268 relocatable files into an already running program; such systems
16269 typically make the requirements above easy to meet. However, it's
16270 important to recognize that many native systems use complex link
16271 procedures (@code{.linkonce} section factoring and C@t{++} constructor table
16272 assembly, for example) that make the requirements difficult to meet. In
16273 general, one cannot assume that using @code{add-symbol-file} to read a
16274 relocatable object file's symbolic information will have the same effect
16275 as linking the relocatable object file into the program in the normal
16278 @code{add-symbol-file} does not repeat if you press @key{RET} after using it.
16280 @kindex add-symbol-file-from-memory
16281 @cindex @code{syscall DSO}
16282 @cindex load symbols from memory
16283 @item add-symbol-file-from-memory @var{address}
16284 Load symbols from the given @var{address} in a dynamically loaded
16285 object file whose image is mapped directly into the inferior's memory.
16286 For example, the Linux kernel maps a @code{syscall DSO} into each
16287 process's address space; this DSO provides kernel-specific code for
16288 some system calls. The argument can be any expression whose
16289 evaluation yields the address of the file's shared object file header.
16290 For this command to work, you must have used @code{symbol-file} or
16291 @code{exec-file} commands in advance.
16293 @kindex add-shared-symbol-files
16295 @item add-shared-symbol-files @var{library-file}
16296 @itemx assf @var{library-file}
16297 The @code{add-shared-symbol-files} command can currently be used only
16298 in the Cygwin build of @value{GDBN} on MS-Windows OS, where it is an
16299 alias for the @code{dll-symbols} command (@pxref{Cygwin Native}).
16300 @value{GDBN} automatically looks for shared libraries, however if
16301 @value{GDBN} does not find yours, you can invoke
16302 @code{add-shared-symbol-files}. It takes one argument: the shared
16303 library's file name. @code{assf} is a shorthand alias for
16304 @code{add-shared-symbol-files}.
16307 @item section @var{section} @var{addr}
16308 The @code{section} command changes the base address of the named
16309 @var{section} of the exec file to @var{addr}. This can be used if the
16310 exec file does not contain section addresses, (such as in the
16311 @code{a.out} format), or when the addresses specified in the file
16312 itself are wrong. Each section must be changed separately. The
16313 @code{info files} command, described below, lists all the sections and
16317 @kindex info target
16320 @code{info files} and @code{info target} are synonymous; both print the
16321 current target (@pxref{Targets, ,Specifying a Debugging Target}),
16322 including the names of the executable and core dump files currently in
16323 use by @value{GDBN}, and the files from which symbols were loaded. The
16324 command @code{help target} lists all possible targets rather than
16327 @kindex maint info sections
16328 @item maint info sections
16329 Another command that can give you extra information about program sections
16330 is @code{maint info sections}. In addition to the section information
16331 displayed by @code{info files}, this command displays the flags and file
16332 offset of each section in the executable and core dump files. In addition,
16333 @code{maint info sections} provides the following command options (which
16334 may be arbitrarily combined):
16338 Display sections for all loaded object files, including shared libraries.
16339 @item @var{sections}
16340 Display info only for named @var{sections}.
16341 @item @var{section-flags}
16342 Display info only for sections for which @var{section-flags} are true.
16343 The section flags that @value{GDBN} currently knows about are:
16346 Section will have space allocated in the process when loaded.
16347 Set for all sections except those containing debug information.
16349 Section will be loaded from the file into the child process memory.
16350 Set for pre-initialized code and data, clear for @code{.bss} sections.
16352 Section needs to be relocated before loading.
16354 Section cannot be modified by the child process.
16356 Section contains executable code only.
16358 Section contains data only (no executable code).
16360 Section will reside in ROM.
16362 Section contains data for constructor/destructor lists.
16364 Section is not empty.
16366 An instruction to the linker to not output the section.
16367 @item COFF_SHARED_LIBRARY
16368 A notification to the linker that the section contains
16369 COFF shared library information.
16371 Section contains common symbols.
16374 @kindex set trust-readonly-sections
16375 @cindex read-only sections
16376 @item set trust-readonly-sections on
16377 Tell @value{GDBN} that readonly sections in your object file
16378 really are read-only (i.e.@: that their contents will not change).
16379 In that case, @value{GDBN} can fetch values from these sections
16380 out of the object file, rather than from the target program.
16381 For some targets (notably embedded ones), this can be a significant
16382 enhancement to debugging performance.
16384 The default is off.
16386 @item set trust-readonly-sections off
16387 Tell @value{GDBN} not to trust readonly sections. This means that
16388 the contents of the section might change while the program is running,
16389 and must therefore be fetched from the target when needed.
16391 @item show trust-readonly-sections
16392 Show the current setting of trusting readonly sections.
16395 All file-specifying commands allow both absolute and relative file names
16396 as arguments. @value{GDBN} always converts the file name to an absolute file
16397 name and remembers it that way.
16399 @cindex shared libraries
16400 @anchor{Shared Libraries}
16401 @value{GDBN} supports @sc{gnu}/Linux, MS-Windows, HP-UX, SunOS, SVr4, Irix,
16402 and IBM RS/6000 AIX shared libraries.
16404 On MS-Windows @value{GDBN} must be linked with the Expat library to support
16405 shared libraries. @xref{Expat}.
16407 @value{GDBN} automatically loads symbol definitions from shared libraries
16408 when you use the @code{run} command, or when you examine a core file.
16409 (Before you issue the @code{run} command, @value{GDBN} does not understand
16410 references to a function in a shared library, however---unless you are
16411 debugging a core file).
16413 On HP-UX, if the program loads a library explicitly, @value{GDBN}
16414 automatically loads the symbols at the time of the @code{shl_load} call.
16416 @c FIXME: some @value{GDBN} release may permit some refs to undef
16417 @c FIXME...symbols---eg in a break cmd---assuming they are from a shared
16418 @c FIXME...lib; check this from time to time when updating manual
16420 There are times, however, when you may wish to not automatically load
16421 symbol definitions from shared libraries, such as when they are
16422 particularly large or there are many of them.
16424 To control the automatic loading of shared library symbols, use the
16428 @kindex set auto-solib-add
16429 @item set auto-solib-add @var{mode}
16430 If @var{mode} is @code{on}, symbols from all shared object libraries
16431 will be loaded automatically when the inferior begins execution, you
16432 attach to an independently started inferior, or when the dynamic linker
16433 informs @value{GDBN} that a new library has been loaded. If @var{mode}
16434 is @code{off}, symbols must be loaded manually, using the
16435 @code{sharedlibrary} command. The default value is @code{on}.
16437 @cindex memory used for symbol tables
16438 If your program uses lots of shared libraries with debug info that
16439 takes large amounts of memory, you can decrease the @value{GDBN}
16440 memory footprint by preventing it from automatically loading the
16441 symbols from shared libraries. To that end, type @kbd{set
16442 auto-solib-add off} before running the inferior, then load each
16443 library whose debug symbols you do need with @kbd{sharedlibrary
16444 @var{regexp}}, where @var{regexp} is a regular expression that matches
16445 the libraries whose symbols you want to be loaded.
16447 @kindex show auto-solib-add
16448 @item show auto-solib-add
16449 Display the current autoloading mode.
16452 @cindex load shared library
16453 To explicitly load shared library symbols, use the @code{sharedlibrary}
16457 @kindex info sharedlibrary
16459 @item info share @var{regex}
16460 @itemx info sharedlibrary @var{regex}
16461 Print the names of the shared libraries which are currently loaded
16462 that match @var{regex}. If @var{regex} is omitted then print
16463 all shared libraries that are loaded.
16465 @kindex sharedlibrary
16467 @item sharedlibrary @var{regex}
16468 @itemx share @var{regex}
16469 Load shared object library symbols for files matching a
16470 Unix regular expression.
16471 As with files loaded automatically, it only loads shared libraries
16472 required by your program for a core file or after typing @code{run}. If
16473 @var{regex} is omitted all shared libraries required by your program are
16476 @item nosharedlibrary
16477 @kindex nosharedlibrary
16478 @cindex unload symbols from shared libraries
16479 Unload all shared object library symbols. This discards all symbols
16480 that have been loaded from all shared libraries. Symbols from shared
16481 libraries that were loaded by explicit user requests are not
16485 Sometimes you may wish that @value{GDBN} stops and gives you control
16486 when any of shared library events happen. The best way to do this is
16487 to use @code{catch load} and @code{catch unload} (@pxref{Set
16490 @value{GDBN} also supports the the @code{set stop-on-solib-events}
16491 command for this. This command exists for historical reasons. It is
16492 less useful than setting a catchpoint, because it does not allow for
16493 conditions or commands as a catchpoint does.
16496 @item set stop-on-solib-events
16497 @kindex set stop-on-solib-events
16498 This command controls whether @value{GDBN} should give you control
16499 when the dynamic linker notifies it about some shared library event.
16500 The most common event of interest is loading or unloading of a new
16503 @item show stop-on-solib-events
16504 @kindex show stop-on-solib-events
16505 Show whether @value{GDBN} stops and gives you control when shared
16506 library events happen.
16509 Shared libraries are also supported in many cross or remote debugging
16510 configurations. @value{GDBN} needs to have access to the target's libraries;
16511 this can be accomplished either by providing copies of the libraries
16512 on the host system, or by asking @value{GDBN} to automatically retrieve the
16513 libraries from the target. If copies of the target libraries are
16514 provided, they need to be the same as the target libraries, although the
16515 copies on the target can be stripped as long as the copies on the host are
16518 @cindex where to look for shared libraries
16519 For remote debugging, you need to tell @value{GDBN} where the target
16520 libraries are, so that it can load the correct copies---otherwise, it
16521 may try to load the host's libraries. @value{GDBN} has two variables
16522 to specify the search directories for target libraries.
16525 @cindex prefix for shared library file names
16526 @cindex system root, alternate
16527 @kindex set solib-absolute-prefix
16528 @kindex set sysroot
16529 @item set sysroot @var{path}
16530 Use @var{path} as the system root for the program being debugged. Any
16531 absolute shared library paths will be prefixed with @var{path}; many
16532 runtime loaders store the absolute paths to the shared library in the
16533 target program's memory. If you use @code{set sysroot} to find shared
16534 libraries, they need to be laid out in the same way that they are on
16535 the target, with e.g.@: a @file{/lib} and @file{/usr/lib} hierarchy
16538 If @var{path} starts with the sequence @file{remote:}, @value{GDBN} will
16539 retrieve the target libraries from the remote system. This is only
16540 supported when using a remote target that supports the @code{remote get}
16541 command (@pxref{File Transfer,,Sending files to a remote system}).
16542 The part of @var{path} following the initial @file{remote:}
16543 (if present) is used as system root prefix on the remote file system.
16544 @footnote{If you want to specify a local system root using a directory
16545 that happens to be named @file{remote:}, you need to use some equivalent
16546 variant of the name like @file{./remote:}.}
16548 For targets with an MS-DOS based filesystem, such as MS-Windows and
16549 SymbianOS, @value{GDBN} tries prefixing a few variants of the target
16550 absolute file name with @var{path}. But first, on Unix hosts,
16551 @value{GDBN} converts all backslash directory separators into forward
16552 slashes, because the backslash is not a directory separator on Unix:
16555 c:\foo\bar.dll @result{} c:/foo/bar.dll
16558 Then, @value{GDBN} attempts prefixing the target file name with
16559 @var{path}, and looks for the resulting file name in the host file
16563 c:/foo/bar.dll @result{} /path/to/sysroot/c:/foo/bar.dll
16566 If that does not find the shared library, @value{GDBN} tries removing
16567 the @samp{:} character from the drive spec, both for convenience, and,
16568 for the case of the host file system not supporting file names with
16572 c:/foo/bar.dll @result{} /path/to/sysroot/c/foo/bar.dll
16575 This makes it possible to have a system root that mirrors a target
16576 with more than one drive. E.g., you may want to setup your local
16577 copies of the target system shared libraries like so (note @samp{c} vs
16581 @file{/path/to/sysroot/c/sys/bin/foo.dll}
16582 @file{/path/to/sysroot/c/sys/bin/bar.dll}
16583 @file{/path/to/sysroot/z/sys/bin/bar.dll}
16587 and point the system root at @file{/path/to/sysroot}, so that
16588 @value{GDBN} can find the correct copies of both
16589 @file{c:\sys\bin\foo.dll}, and @file{z:\sys\bin\bar.dll}.
16591 If that still does not find the shared library, @value{GDBN} tries
16592 removing the whole drive spec from the target file name:
16595 c:/foo/bar.dll @result{} /path/to/sysroot/foo/bar.dll
16598 This last lookup makes it possible to not care about the drive name,
16599 if you don't want or need to.
16601 The @code{set solib-absolute-prefix} command is an alias for @code{set
16604 @cindex default system root
16605 @cindex @samp{--with-sysroot}
16606 You can set the default system root by using the configure-time
16607 @samp{--with-sysroot} option. If the system root is inside
16608 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
16609 @samp{--exec-prefix}), then the default system root will be updated
16610 automatically if the installed @value{GDBN} is moved to a new
16613 @kindex show sysroot
16615 Display the current shared library prefix.
16617 @kindex set solib-search-path
16618 @item set solib-search-path @var{path}
16619 If this variable is set, @var{path} is a colon-separated list of
16620 directories to search for shared libraries. @samp{solib-search-path}
16621 is used after @samp{sysroot} fails to locate the library, or if the
16622 path to the library is relative instead of absolute. If you want to
16623 use @samp{solib-search-path} instead of @samp{sysroot}, be sure to set
16624 @samp{sysroot} to a nonexistent directory to prevent @value{GDBN} from
16625 finding your host's libraries. @samp{sysroot} is preferred; setting
16626 it to a nonexistent directory may interfere with automatic loading
16627 of shared library symbols.
16629 @kindex show solib-search-path
16630 @item show solib-search-path
16631 Display the current shared library search path.
16633 @cindex DOS file-name semantics of file names.
16634 @kindex set target-file-system-kind (unix|dos-based|auto)
16635 @kindex show target-file-system-kind
16636 @item set target-file-system-kind @var{kind}
16637 Set assumed file system kind for target reported file names.
16639 Shared library file names as reported by the target system may not
16640 make sense as is on the system @value{GDBN} is running on. For
16641 example, when remote debugging a target that has MS-DOS based file
16642 system semantics, from a Unix host, the target may be reporting to
16643 @value{GDBN} a list of loaded shared libraries with file names such as
16644 @file{c:\Windows\kernel32.dll}. On Unix hosts, there's no concept of
16645 drive letters, so the @samp{c:\} prefix is not normally understood as
16646 indicating an absolute file name, and neither is the backslash
16647 normally considered a directory separator character. In that case,
16648 the native file system would interpret this whole absolute file name
16649 as a relative file name with no directory components. This would make
16650 it impossible to point @value{GDBN} at a copy of the remote target's
16651 shared libraries on the host using @code{set sysroot}, and impractical
16652 with @code{set solib-search-path}. Setting
16653 @code{target-file-system-kind} to @code{dos-based} tells @value{GDBN}
16654 to interpret such file names similarly to how the target would, and to
16655 map them to file names valid on @value{GDBN}'s native file system
16656 semantics. The value of @var{kind} can be @code{"auto"}, in addition
16657 to one of the supported file system kinds. In that case, @value{GDBN}
16658 tries to determine the appropriate file system variant based on the
16659 current target's operating system (@pxref{ABI, ,Configuring the
16660 Current ABI}). The supported file system settings are:
16664 Instruct @value{GDBN} to assume the target file system is of Unix
16665 kind. Only file names starting the forward slash (@samp{/}) character
16666 are considered absolute, and the directory separator character is also
16670 Instruct @value{GDBN} to assume the target file system is DOS based.
16671 File names starting with either a forward slash, or a drive letter
16672 followed by a colon (e.g., @samp{c:}), are considered absolute, and
16673 both the slash (@samp{/}) and the backslash (@samp{\\}) characters are
16674 considered directory separators.
16677 Instruct @value{GDBN} to use the file system kind associated with the
16678 target operating system (@pxref{ABI, ,Configuring the Current ABI}).
16679 This is the default.
16683 @cindex file name canonicalization
16684 @cindex base name differences
16685 When processing file names provided by the user, @value{GDBN}
16686 frequently needs to compare them to the file names recorded in the
16687 program's debug info. Normally, @value{GDBN} compares just the
16688 @dfn{base names} of the files as strings, which is reasonably fast
16689 even for very large programs. (The base name of a file is the last
16690 portion of its name, after stripping all the leading directories.)
16691 This shortcut in comparison is based upon the assumption that files
16692 cannot have more than one base name. This is usually true, but
16693 references to files that use symlinks or similar filesystem
16694 facilities violate that assumption. If your program records files
16695 using such facilities, or if you provide file names to @value{GDBN}
16696 using symlinks etc., you can set @code{basenames-may-differ} to
16697 @code{true} to instruct @value{GDBN} to completely canonicalize each
16698 pair of file names it needs to compare. This will make file-name
16699 comparisons accurate, but at a price of a significant slowdown.
16702 @item set basenames-may-differ
16703 @kindex set basenames-may-differ
16704 Set whether a source file may have multiple base names.
16706 @item show basenames-may-differ
16707 @kindex show basenames-may-differ
16708 Show whether a source file may have multiple base names.
16711 @node Separate Debug Files
16712 @section Debugging Information in Separate Files
16713 @cindex separate debugging information files
16714 @cindex debugging information in separate files
16715 @cindex @file{.debug} subdirectories
16716 @cindex debugging information directory, global
16717 @cindex global debugging information directories
16718 @cindex build ID, and separate debugging files
16719 @cindex @file{.build-id} directory
16721 @value{GDBN} allows you to put a program's debugging information in a
16722 file separate from the executable itself, in a way that allows
16723 @value{GDBN} to find and load the debugging information automatically.
16724 Since debugging information can be very large---sometimes larger
16725 than the executable code itself---some systems distribute debugging
16726 information for their executables in separate files, which users can
16727 install only when they need to debug a problem.
16729 @value{GDBN} supports two ways of specifying the separate debug info
16734 The executable contains a @dfn{debug link} that specifies the name of
16735 the separate debug info file. The separate debug file's name is
16736 usually @file{@var{executable}.debug}, where @var{executable} is the
16737 name of the corresponding executable file without leading directories
16738 (e.g., @file{ls.debug} for @file{/usr/bin/ls}). In addition, the
16739 debug link specifies a 32-bit @dfn{Cyclic Redundancy Check} (CRC)
16740 checksum for the debug file, which @value{GDBN} uses to validate that
16741 the executable and the debug file came from the same build.
16744 The executable contains a @dfn{build ID}, a unique bit string that is
16745 also present in the corresponding debug info file. (This is supported
16746 only on some operating systems, notably those which use the ELF format
16747 for binary files and the @sc{gnu} Binutils.) For more details about
16748 this feature, see the description of the @option{--build-id}
16749 command-line option in @ref{Options, , Command Line Options, ld.info,
16750 The GNU Linker}. The debug info file's name is not specified
16751 explicitly by the build ID, but can be computed from the build ID, see
16755 Depending on the way the debug info file is specified, @value{GDBN}
16756 uses two different methods of looking for the debug file:
16760 For the ``debug link'' method, @value{GDBN} looks up the named file in
16761 the directory of the executable file, then in a subdirectory of that
16762 directory named @file{.debug}, and finally under each one of the global debug
16763 directories, in a subdirectory whose name is identical to the leading
16764 directories of the executable's absolute file name.
16767 For the ``build ID'' method, @value{GDBN} looks in the
16768 @file{.build-id} subdirectory of each one of the global debug directories for
16769 a file named @file{@var{nn}/@var{nnnnnnnn}.debug}, where @var{nn} are the
16770 first 2 hex characters of the build ID bit string, and @var{nnnnnnnn}
16771 are the rest of the bit string. (Real build ID strings are 32 or more
16772 hex characters, not 10.)
16775 So, for example, suppose you ask @value{GDBN} to debug
16776 @file{/usr/bin/ls}, which has a debug link that specifies the
16777 file @file{ls.debug}, and a build ID whose value in hex is
16778 @code{abcdef1234}. If the list of the global debug directories includes
16779 @file{/usr/lib/debug}, then @value{GDBN} will look for the following
16780 debug information files, in the indicated order:
16784 @file{/usr/lib/debug/.build-id/ab/cdef1234.debug}
16786 @file{/usr/bin/ls.debug}
16788 @file{/usr/bin/.debug/ls.debug}
16790 @file{/usr/lib/debug/usr/bin/ls.debug}.
16793 @anchor{debug-file-directory}
16794 Global debugging info directories default to what is set by @value{GDBN}
16795 configure option @option{--with-separate-debug-dir}. During @value{GDBN} run
16796 you can also set the global debugging info directories, and view the list
16797 @value{GDBN} is currently using.
16801 @kindex set debug-file-directory
16802 @item set debug-file-directory @var{directories}
16803 Set the directories which @value{GDBN} searches for separate debugging
16804 information files to @var{directory}. Multiple path components can be set
16805 concatenating them by a path separator.
16807 @kindex show debug-file-directory
16808 @item show debug-file-directory
16809 Show the directories @value{GDBN} searches for separate debugging
16814 @cindex @code{.gnu_debuglink} sections
16815 @cindex debug link sections
16816 A debug link is a special section of the executable file named
16817 @code{.gnu_debuglink}. The section must contain:
16821 A filename, with any leading directory components removed, followed by
16824 zero to three bytes of padding, as needed to reach the next four-byte
16825 boundary within the section, and
16827 a four-byte CRC checksum, stored in the same endianness used for the
16828 executable file itself. The checksum is computed on the debugging
16829 information file's full contents by the function given below, passing
16830 zero as the @var{crc} argument.
16833 Any executable file format can carry a debug link, as long as it can
16834 contain a section named @code{.gnu_debuglink} with the contents
16837 @cindex @code{.note.gnu.build-id} sections
16838 @cindex build ID sections
16839 The build ID is a special section in the executable file (and in other
16840 ELF binary files that @value{GDBN} may consider). This section is
16841 often named @code{.note.gnu.build-id}, but that name is not mandatory.
16842 It contains unique identification for the built files---the ID remains
16843 the same across multiple builds of the same build tree. The default
16844 algorithm SHA1 produces 160 bits (40 hexadecimal characters) of the
16845 content for the build ID string. The same section with an identical
16846 value is present in the original built binary with symbols, in its
16847 stripped variant, and in the separate debugging information file.
16849 The debugging information file itself should be an ordinary
16850 executable, containing a full set of linker symbols, sections, and
16851 debugging information. The sections of the debugging information file
16852 should have the same names, addresses, and sizes as the original file,
16853 but they need not contain any data---much like a @code{.bss} section
16854 in an ordinary executable.
16856 The @sc{gnu} binary utilities (Binutils) package includes the
16857 @samp{objcopy} utility that can produce
16858 the separated executable / debugging information file pairs using the
16859 following commands:
16862 @kbd{objcopy --only-keep-debug foo foo.debug}
16867 These commands remove the debugging
16868 information from the executable file @file{foo} and place it in the file
16869 @file{foo.debug}. You can use the first, second or both methods to link the
16874 The debug link method needs the following additional command to also leave
16875 behind a debug link in @file{foo}:
16878 @kbd{objcopy --add-gnu-debuglink=foo.debug foo}
16881 Ulrich Drepper's @file{elfutils} package, starting with version 0.53, contains
16882 a version of the @code{strip} command such that the command @kbd{strip foo -f
16883 foo.debug} has the same functionality as the two @code{objcopy} commands and
16884 the @code{ln -s} command above, together.
16887 Build ID gets embedded into the main executable using @code{ld --build-id} or
16888 the @value{NGCC} counterpart @code{gcc -Wl,--build-id}. Build ID support plus
16889 compatibility fixes for debug files separation are present in @sc{gnu} binary
16890 utilities (Binutils) package since version 2.18.
16895 @cindex CRC algorithm definition
16896 The CRC used in @code{.gnu_debuglink} is the CRC-32 defined in
16897 IEEE 802.3 using the polynomial:
16899 @c TexInfo requires naked braces for multi-digit exponents for Tex
16900 @c output, but this causes HTML output to barf. HTML has to be set using
16901 @c raw commands. So we end up having to specify this equation in 2
16906 <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>
16907 + <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
16913 @math{x^{32} + x^{26} + x^{23} + x^{22} + x^{16} + x^{12} + x^{11}}
16914 @math{+ x^{10} + x^8 + x^7 + x^5 + x^4 + x^2 + x + 1}
16918 The function is computed byte at a time, taking the least
16919 significant bit of each byte first. The initial pattern
16920 @code{0xffffffff} is used, to ensure leading zeros affect the CRC and
16921 the final result is inverted to ensure trailing zeros also affect the
16924 @emph{Note:} This is the same CRC polynomial as used in handling the
16925 @dfn{Remote Serial Protocol} @code{qCRC} packet (@pxref{Remote Protocol,
16926 , @value{GDBN} Remote Serial Protocol}). However in the
16927 case of the Remote Serial Protocol, the CRC is computed @emph{most}
16928 significant bit first, and the result is not inverted, so trailing
16929 zeros have no effect on the CRC value.
16931 To complete the description, we show below the code of the function
16932 which produces the CRC used in @code{.gnu_debuglink}. Inverting the
16933 initially supplied @code{crc} argument means that an initial call to
16934 this function passing in zero will start computing the CRC using
16937 @kindex gnu_debuglink_crc32
16940 gnu_debuglink_crc32 (unsigned long crc,
16941 unsigned char *buf, size_t len)
16943 static const unsigned long crc32_table[256] =
16945 0x00000000, 0x77073096, 0xee0e612c, 0x990951ba, 0x076dc419,
16946 0x706af48f, 0xe963a535, 0x9e6495a3, 0x0edb8832, 0x79dcb8a4,
16947 0xe0d5e91e, 0x97d2d988, 0x09b64c2b, 0x7eb17cbd, 0xe7b82d07,
16948 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de,
16949 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856,
16950 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9,
16951 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4,
16952 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b,
16953 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3,
16954 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a,
16955 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599,
16956 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924,
16957 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190,
16958 0x01db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x06b6b51f,
16959 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0x0f00f934, 0x9609a88e,
16960 0xe10e9818, 0x7f6a0dbb, 0x086d3d2d, 0x91646c97, 0xe6635c01,
16961 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed,
16962 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950,
16963 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3,
16964 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2,
16965 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a,
16966 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5,
16967 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010,
16968 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f,
16969 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17,
16970 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6,
16971 0x03b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x04db2615,
16972 0x73dc1683, 0xe3630b12, 0x94643b84, 0x0d6d6a3e, 0x7a6a5aa8,
16973 0xe40ecf0b, 0x9309ff9d, 0x0a00ae27, 0x7d079eb1, 0xf00f9344,
16974 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb,
16975 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a,
16976 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5,
16977 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1,
16978 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c,
16979 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef,
16980 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236,
16981 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe,
16982 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31,
16983 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c,
16984 0x026d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x05005713,
16985 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0x0cb61b38, 0x92d28e9b,
16986 0xe5d5be0d, 0x7cdcefb7, 0x0bdbdf21, 0x86d3d2d4, 0xf1d4e242,
16987 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1,
16988 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c,
16989 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278,
16990 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7,
16991 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66,
16992 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9,
16993 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605,
16994 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8,
16995 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b,
16998 unsigned char *end;
17000 crc = ~crc & 0xffffffff;
17001 for (end = buf + len; buf < end; ++buf)
17002 crc = crc32_table[(crc ^ *buf) & 0xff] ^ (crc >> 8);
17003 return ~crc & 0xffffffff;
17008 This computation does not apply to the ``build ID'' method.
17010 @node MiniDebugInfo
17011 @section Debugging information in a special section
17012 @cindex separate debug sections
17013 @cindex @samp{.gnu_debugdata} section
17015 Some systems ship pre-built executables and libraries that have a
17016 special @samp{.gnu_debugdata} section. This feature is called
17017 @dfn{MiniDebugInfo}. This section holds an LZMA-compressed object and
17018 is used to supply extra symbols for backtraces.
17020 The intent of this section is to provide extra minimal debugging
17021 information for use in simple backtraces. It is not intended to be a
17022 replacement for full separate debugging information (@pxref{Separate
17023 Debug Files}). The example below shows the intended use; however,
17024 @value{GDBN} does not currently put restrictions on what sort of
17025 debugging information might be included in the section.
17027 @value{GDBN} has support for this extension. If the section exists,
17028 then it is used provided that no other source of debugging information
17029 can be found, and that @value{GDBN} was configured with LZMA support.
17031 This section can be easily created using @command{objcopy} and other
17032 standard utilities:
17035 # Extract the dynamic symbols from the main binary, there is no need
17036 # to also have these in the normal symbol table
17037 nm -D @var{binary} --format=posix --defined-only \
17038 | awk '@{ print $1 @}' | sort > dynsyms
17040 # Extract all the text (i.e. function) symbols from the debuginfo .
17041 nm @var{binary} --format=posix --defined-only \
17042 | awk '@{ if ($2 == "T" || $2 == "t") print $1 @}' \
17045 # Keep all the function symbols not already in the dynamic symbol
17047 comm -13 dynsyms funcsyms > keep_symbols
17049 # Copy the full debuginfo, keeping only a minimal set of symbols and
17050 # removing some unnecessary sections.
17051 objcopy -S --remove-section .gdb_index --remove-section .comment \
17052 --keep-symbols=keep_symbols @var{binary} mini_debuginfo
17054 # Inject the compressed data into the .gnu_debugdata section of the
17057 objcopy --add-section .gnu_debugdata=mini_debuginfo.xz @var{binary}
17061 @section Index Files Speed Up @value{GDBN}
17062 @cindex index files
17063 @cindex @samp{.gdb_index} section
17065 When @value{GDBN} finds a symbol file, it scans the symbols in the
17066 file in order to construct an internal symbol table. This lets most
17067 @value{GDBN} operations work quickly---at the cost of a delay early
17068 on. For large programs, this delay can be quite lengthy, so
17069 @value{GDBN} provides a way to build an index, which speeds up
17072 The index is stored as a section in the symbol file. @value{GDBN} can
17073 write the index to a file, then you can put it into the symbol file
17074 using @command{objcopy}.
17076 To create an index file, use the @code{save gdb-index} command:
17079 @item save gdb-index @var{directory}
17080 @kindex save gdb-index
17081 Create an index file for each symbol file currently known by
17082 @value{GDBN}. Each file is named after its corresponding symbol file,
17083 with @samp{.gdb-index} appended, and is written into the given
17087 Once you have created an index file you can merge it into your symbol
17088 file, here named @file{symfile}, using @command{objcopy}:
17091 $ objcopy --add-section .gdb_index=symfile.gdb-index \
17092 --set-section-flags .gdb_index=readonly symfile symfile
17095 @value{GDBN} will normally ignore older versions of @file{.gdb_index}
17096 sections that have been deprecated. Usually they are deprecated because
17097 they are missing a new feature or have performance issues.
17098 To tell @value{GDBN} to use a deprecated index section anyway
17099 specify @code{set use-deprecated-index-sections on}.
17100 The default is @code{off}.
17101 This can speed up startup, but may result in some functionality being lost.
17102 @xref{Index Section Format}.
17104 @emph{Warning:} Setting @code{use-deprecated-index-sections} to @code{on}
17105 must be done before gdb reads the file. The following will not work:
17108 $ gdb -ex "set use-deprecated-index-sections on" <program>
17111 Instead you must do, for example,
17114 $ gdb -iex "set use-deprecated-index-sections on" <program>
17117 There are currently some limitation on indices. They only work when
17118 for DWARF debugging information, not stabs. And, they do not
17119 currently work for programs using Ada.
17121 @node Symbol Errors
17122 @section Errors Reading Symbol Files
17124 While reading a symbol file, @value{GDBN} occasionally encounters problems,
17125 such as symbol types it does not recognize, or known bugs in compiler
17126 output. By default, @value{GDBN} does not notify you of such problems, since
17127 they are relatively common and primarily of interest to people
17128 debugging compilers. If you are interested in seeing information
17129 about ill-constructed symbol tables, you can either ask @value{GDBN} to print
17130 only one message about each such type of problem, no matter how many
17131 times the problem occurs; or you can ask @value{GDBN} to print more messages,
17132 to see how many times the problems occur, with the @code{set
17133 complaints} command (@pxref{Messages/Warnings, ,Optional Warnings and
17136 The messages currently printed, and their meanings, include:
17139 @item inner block not inside outer block in @var{symbol}
17141 The symbol information shows where symbol scopes begin and end
17142 (such as at the start of a function or a block of statements). This
17143 error indicates that an inner scope block is not fully contained
17144 in its outer scope blocks.
17146 @value{GDBN} circumvents the problem by treating the inner block as if it had
17147 the same scope as the outer block. In the error message, @var{symbol}
17148 may be shown as ``@code{(don't know)}'' if the outer block is not a
17151 @item block at @var{address} out of order
17153 The symbol information for symbol scope blocks should occur in
17154 order of increasing addresses. This error indicates that it does not
17157 @value{GDBN} does not circumvent this problem, and has trouble
17158 locating symbols in the source file whose symbols it is reading. (You
17159 can often determine what source file is affected by specifying
17160 @code{set verbose on}. @xref{Messages/Warnings, ,Optional Warnings and
17163 @item bad block start address patched
17165 The symbol information for a symbol scope block has a start address
17166 smaller than the address of the preceding source line. This is known
17167 to occur in the SunOS 4.1.1 (and earlier) C compiler.
17169 @value{GDBN} circumvents the problem by treating the symbol scope block as
17170 starting on the previous source line.
17172 @item bad string table offset in symbol @var{n}
17175 Symbol number @var{n} contains a pointer into the string table which is
17176 larger than the size of the string table.
17178 @value{GDBN} circumvents the problem by considering the symbol to have the
17179 name @code{foo}, which may cause other problems if many symbols end up
17182 @item unknown symbol type @code{0x@var{nn}}
17184 The symbol information contains new data types that @value{GDBN} does
17185 not yet know how to read. @code{0x@var{nn}} is the symbol type of the
17186 uncomprehended information, in hexadecimal.
17188 @value{GDBN} circumvents the error by ignoring this symbol information.
17189 This usually allows you to debug your program, though certain symbols
17190 are not accessible. If you encounter such a problem and feel like
17191 debugging it, you can debug @code{@value{GDBP}} with itself, breakpoint
17192 on @code{complain}, then go up to the function @code{read_dbx_symtab}
17193 and examine @code{*bufp} to see the symbol.
17195 @item stub type has NULL name
17197 @value{GDBN} could not find the full definition for a struct or class.
17199 @item const/volatile indicator missing (ok if using g++ v1.x), got@dots{}
17200 The symbol information for a C@t{++} member function is missing some
17201 information that recent versions of the compiler should have output for
17204 @item info mismatch between compiler and debugger
17206 @value{GDBN} could not parse a type specification output by the compiler.
17211 @section GDB Data Files
17213 @cindex prefix for data files
17214 @value{GDBN} will sometimes read an auxiliary data file. These files
17215 are kept in a directory known as the @dfn{data directory}.
17217 You can set the data directory's name, and view the name @value{GDBN}
17218 is currently using.
17221 @kindex set data-directory
17222 @item set data-directory @var{directory}
17223 Set the directory which @value{GDBN} searches for auxiliary data files
17224 to @var{directory}.
17226 @kindex show data-directory
17227 @item show data-directory
17228 Show the directory @value{GDBN} searches for auxiliary data files.
17231 @cindex default data directory
17232 @cindex @samp{--with-gdb-datadir}
17233 You can set the default data directory by using the configure-time
17234 @samp{--with-gdb-datadir} option. If the data directory is inside
17235 @value{GDBN}'s configured binary prefix (set with @samp{--prefix} or
17236 @samp{--exec-prefix}), then the default data directory will be updated
17237 automatically if the installed @value{GDBN} is moved to a new
17240 The data directory may also be specified with the
17241 @code{--data-directory} command line option.
17242 @xref{Mode Options}.
17245 @chapter Specifying a Debugging Target
17247 @cindex debugging target
17248 A @dfn{target} is the execution environment occupied by your program.
17250 Often, @value{GDBN} runs in the same host environment as your program;
17251 in that case, the debugging target is specified as a side effect when
17252 you use the @code{file} or @code{core} commands. When you need more
17253 flexibility---for example, running @value{GDBN} on a physically separate
17254 host, or controlling a standalone system over a serial port or a
17255 realtime system over a TCP/IP connection---you can use the @code{target}
17256 command to specify one of the target types configured for @value{GDBN}
17257 (@pxref{Target Commands, ,Commands for Managing Targets}).
17259 @cindex target architecture
17260 It is possible to build @value{GDBN} for several different @dfn{target
17261 architectures}. When @value{GDBN} is built like that, you can choose
17262 one of the available architectures with the @kbd{set architecture}
17266 @kindex set architecture
17267 @kindex show architecture
17268 @item set architecture @var{arch}
17269 This command sets the current target architecture to @var{arch}. The
17270 value of @var{arch} can be @code{"auto"}, in addition to one of the
17271 supported architectures.
17273 @item show architecture
17274 Show the current target architecture.
17276 @item set processor
17278 @kindex set processor
17279 @kindex show processor
17280 These are alias commands for, respectively, @code{set architecture}
17281 and @code{show architecture}.
17285 * Active Targets:: Active targets
17286 * Target Commands:: Commands for managing targets
17287 * Byte Order:: Choosing target byte order
17290 @node Active Targets
17291 @section Active Targets
17293 @cindex stacking targets
17294 @cindex active targets
17295 @cindex multiple targets
17297 There are multiple classes of targets such as: processes, executable files or
17298 recording sessions. Core files belong to the process class, making core file
17299 and process mutually exclusive. Otherwise, @value{GDBN} can work concurrently
17300 on multiple active targets, one in each class. This allows you to (for
17301 example) start a process and inspect its activity, while still having access to
17302 the executable file after the process finishes. Or if you start process
17303 recording (@pxref{Reverse Execution}) and @code{reverse-step} there, you are
17304 presented a virtual layer of the recording target, while the process target
17305 remains stopped at the chronologically last point of the process execution.
17307 Use the @code{core-file} and @code{exec-file} commands to select a new core
17308 file or executable target (@pxref{Files, ,Commands to Specify Files}). To
17309 specify as a target a process that is already running, use the @code{attach}
17310 command (@pxref{Attach, ,Debugging an Already-running Process}).
17312 @node Target Commands
17313 @section Commands for Managing Targets
17316 @item target @var{type} @var{parameters}
17317 Connects the @value{GDBN} host environment to a target machine or
17318 process. A target is typically a protocol for talking to debugging
17319 facilities. You use the argument @var{type} to specify the type or
17320 protocol of the target machine.
17322 Further @var{parameters} are interpreted by the target protocol, but
17323 typically include things like device names or host names to connect
17324 with, process numbers, and baud rates.
17326 The @code{target} command does not repeat if you press @key{RET} again
17327 after executing the command.
17329 @kindex help target
17331 Displays the names of all targets available. To display targets
17332 currently selected, use either @code{info target} or @code{info files}
17333 (@pxref{Files, ,Commands to Specify Files}).
17335 @item help target @var{name}
17336 Describe a particular target, including any parameters necessary to
17339 @kindex set gnutarget
17340 @item set gnutarget @var{args}
17341 @value{GDBN} uses its own library BFD to read your files. @value{GDBN}
17342 knows whether it is reading an @dfn{executable},
17343 a @dfn{core}, or a @dfn{.o} file; however, you can specify the file format
17344 with the @code{set gnutarget} command. Unlike most @code{target} commands,
17345 with @code{gnutarget} the @code{target} refers to a program, not a machine.
17348 @emph{Warning:} To specify a file format with @code{set gnutarget},
17349 you must know the actual BFD name.
17353 @xref{Files, , Commands to Specify Files}.
17355 @kindex show gnutarget
17356 @item show gnutarget
17357 Use the @code{show gnutarget} command to display what file format
17358 @code{gnutarget} is set to read. If you have not set @code{gnutarget},
17359 @value{GDBN} will determine the file format for each file automatically,
17360 and @code{show gnutarget} displays @samp{The current BFD target is "auto"}.
17363 @cindex common targets
17364 Here are some common targets (available, or not, depending on the GDB
17369 @item target exec @var{program}
17370 @cindex executable file target
17371 An executable file. @samp{target exec @var{program}} is the same as
17372 @samp{exec-file @var{program}}.
17374 @item target core @var{filename}
17375 @cindex core dump file target
17376 A core dump file. @samp{target core @var{filename}} is the same as
17377 @samp{core-file @var{filename}}.
17379 @item target remote @var{medium}
17380 @cindex remote target
17381 A remote system connected to @value{GDBN} via a serial line or network
17382 connection. This command tells @value{GDBN} to use its own remote
17383 protocol over @var{medium} for debugging. @xref{Remote Debugging}.
17385 For example, if you have a board connected to @file{/dev/ttya} on the
17386 machine running @value{GDBN}, you could say:
17389 target remote /dev/ttya
17392 @code{target remote} supports the @code{load} command. This is only
17393 useful if you have some other way of getting the stub to the target
17394 system, and you can put it somewhere in memory where it won't get
17395 clobbered by the download.
17397 @item target sim @r{[}@var{simargs}@r{]} @dots{}
17398 @cindex built-in simulator target
17399 Builtin CPU simulator. @value{GDBN} includes simulators for most architectures.
17407 works; however, you cannot assume that a specific memory map, device
17408 drivers, or even basic I/O is available, although some simulators do
17409 provide these. For info about any processor-specific simulator details,
17410 see the appropriate section in @ref{Embedded Processors, ,Embedded
17415 Some configurations may include these targets as well:
17419 @item target nrom @var{dev}
17420 @cindex NetROM ROM emulator target
17421 NetROM ROM emulator. This target only supports downloading.
17425 Different targets are available on different configurations of @value{GDBN};
17426 your configuration may have more or fewer targets.
17428 Many remote targets require you to download the executable's code once
17429 you've successfully established a connection. You may wish to control
17430 various aspects of this process.
17435 @kindex set hash@r{, for remote monitors}
17436 @cindex hash mark while downloading
17437 This command controls whether a hash mark @samp{#} is displayed while
17438 downloading a file to the remote monitor. If on, a hash mark is
17439 displayed after each S-record is successfully downloaded to the
17443 @kindex show hash@r{, for remote monitors}
17444 Show the current status of displaying the hash mark.
17446 @item set debug monitor
17447 @kindex set debug monitor
17448 @cindex display remote monitor communications
17449 Enable or disable display of communications messages between
17450 @value{GDBN} and the remote monitor.
17452 @item show debug monitor
17453 @kindex show debug monitor
17454 Show the current status of displaying communications between
17455 @value{GDBN} and the remote monitor.
17460 @kindex load @var{filename}
17461 @item load @var{filename}
17463 Depending on what remote debugging facilities are configured into
17464 @value{GDBN}, the @code{load} command may be available. Where it exists, it
17465 is meant to make @var{filename} (an executable) available for debugging
17466 on the remote system---by downloading, or dynamic linking, for example.
17467 @code{load} also records the @var{filename} symbol table in @value{GDBN}, like
17468 the @code{add-symbol-file} command.
17470 If your @value{GDBN} does not have a @code{load} command, attempting to
17471 execute it gets the error message ``@code{You can't do that when your
17472 target is @dots{}}''
17474 The file is loaded at whatever address is specified in the executable.
17475 For some object file formats, you can specify the load address when you
17476 link the program; for other formats, like a.out, the object file format
17477 specifies a fixed address.
17478 @c FIXME! This would be a good place for an xref to the GNU linker doc.
17480 Depending on the remote side capabilities, @value{GDBN} may be able to
17481 load programs into flash memory.
17483 @code{load} does not repeat if you press @key{RET} again after using it.
17487 @section Choosing Target Byte Order
17489 @cindex choosing target byte order
17490 @cindex target byte order
17492 Some types of processors, such as the @acronym{MIPS}, PowerPC, and Renesas SH,
17493 offer the ability to run either big-endian or little-endian byte
17494 orders. Usually the executable or symbol will include a bit to
17495 designate the endian-ness, and you will not need to worry about
17496 which to use. However, you may still find it useful to adjust
17497 @value{GDBN}'s idea of processor endian-ness manually.
17501 @item set endian big
17502 Instruct @value{GDBN} to assume the target is big-endian.
17504 @item set endian little
17505 Instruct @value{GDBN} to assume the target is little-endian.
17507 @item set endian auto
17508 Instruct @value{GDBN} to use the byte order associated with the
17512 Display @value{GDBN}'s current idea of the target byte order.
17516 Note that these commands merely adjust interpretation of symbolic
17517 data on the host, and that they have absolutely no effect on the
17521 @node Remote Debugging
17522 @chapter Debugging Remote Programs
17523 @cindex remote debugging
17525 If you are trying to debug a program running on a machine that cannot run
17526 @value{GDBN} in the usual way, it is often useful to use remote debugging.
17527 For example, you might use remote debugging on an operating system kernel,
17528 or on a small system which does not have a general purpose operating system
17529 powerful enough to run a full-featured debugger.
17531 Some configurations of @value{GDBN} have special serial or TCP/IP interfaces
17532 to make this work with particular debugging targets. In addition,
17533 @value{GDBN} comes with a generic serial protocol (specific to @value{GDBN},
17534 but not specific to any particular target system) which you can use if you
17535 write the remote stubs---the code that runs on the remote system to
17536 communicate with @value{GDBN}.
17538 Other remote targets may be available in your
17539 configuration of @value{GDBN}; use @code{help target} to list them.
17542 * Connecting:: Connecting to a remote target
17543 * File Transfer:: Sending files to a remote system
17544 * Server:: Using the gdbserver program
17545 * Remote Configuration:: Remote configuration
17546 * Remote Stub:: Implementing a remote stub
17550 @section Connecting to a Remote Target
17552 On the @value{GDBN} host machine, you will need an unstripped copy of
17553 your program, since @value{GDBN} needs symbol and debugging information.
17554 Start up @value{GDBN} as usual, using the name of the local copy of your
17555 program as the first argument.
17557 @cindex @code{target remote}
17558 @value{GDBN} can communicate with the target over a serial line, or
17559 over an @acronym{IP} network using @acronym{TCP} or @acronym{UDP}. In
17560 each case, @value{GDBN} uses the same protocol for debugging your
17561 program; only the medium carrying the debugging packets varies. The
17562 @code{target remote} command establishes a connection to the target.
17563 Its arguments indicate which medium to use:
17567 @item target remote @var{serial-device}
17568 @cindex serial line, @code{target remote}
17569 Use @var{serial-device} to communicate with the target. For example,
17570 to use a serial line connected to the device named @file{/dev/ttyb}:
17573 target remote /dev/ttyb
17576 If you're using a serial line, you may want to give @value{GDBN} the
17577 @w{@samp{--baud}} option, or use the @code{set remotebaud} command
17578 (@pxref{Remote Configuration, set remotebaud}) before the
17579 @code{target} command.
17581 @item target remote @code{@var{host}:@var{port}}
17582 @itemx target remote @code{tcp:@var{host}:@var{port}}
17583 @cindex @acronym{TCP} port, @code{target remote}
17584 Debug using a @acronym{TCP} connection to @var{port} on @var{host}.
17585 The @var{host} may be either a host name or a numeric @acronym{IP}
17586 address; @var{port} must be a decimal number. The @var{host} could be
17587 the target machine itself, if it is directly connected to the net, or
17588 it might be a terminal server which in turn has a serial line to the
17591 For example, to connect to port 2828 on a terminal server named
17595 target remote manyfarms:2828
17598 If your remote target is actually running on the same machine as your
17599 debugger session (e.g.@: a simulator for your target running on the
17600 same host), you can omit the hostname. For example, to connect to
17601 port 1234 on your local machine:
17604 target remote :1234
17608 Note that the colon is still required here.
17610 @item target remote @code{udp:@var{host}:@var{port}}
17611 @cindex @acronym{UDP} port, @code{target remote}
17612 Debug using @acronym{UDP} packets to @var{port} on @var{host}. For example, to
17613 connect to @acronym{UDP} port 2828 on a terminal server named @code{manyfarms}:
17616 target remote udp:manyfarms:2828
17619 When using a @acronym{UDP} connection for remote debugging, you should
17620 keep in mind that the `U' stands for ``Unreliable''. @acronym{UDP}
17621 can silently drop packets on busy or unreliable networks, which will
17622 cause havoc with your debugging session.
17624 @item target remote | @var{command}
17625 @cindex pipe, @code{target remote} to
17626 Run @var{command} in the background and communicate with it using a
17627 pipe. The @var{command} is a shell command, to be parsed and expanded
17628 by the system's command shell, @code{/bin/sh}; it should expect remote
17629 protocol packets on its standard input, and send replies on its
17630 standard output. You could use this to run a stand-alone simulator
17631 that speaks the remote debugging protocol, to make net connections
17632 using programs like @code{ssh}, or for other similar tricks.
17634 If @var{command} closes its standard output (perhaps by exiting),
17635 @value{GDBN} will try to send it a @code{SIGTERM} signal. (If the
17636 program has already exited, this will have no effect.)
17640 Once the connection has been established, you can use all the usual
17641 commands to examine and change data. The remote program is already
17642 running; you can use @kbd{step} and @kbd{continue}, and you do not
17643 need to use @kbd{run}.
17645 @cindex interrupting remote programs
17646 @cindex remote programs, interrupting
17647 Whenever @value{GDBN} is waiting for the remote program, if you type the
17648 interrupt character (often @kbd{Ctrl-c}), @value{GDBN} attempts to stop the
17649 program. This may or may not succeed, depending in part on the hardware
17650 and the serial drivers the remote system uses. If you type the
17651 interrupt character once again, @value{GDBN} displays this prompt:
17654 Interrupted while waiting for the program.
17655 Give up (and stop debugging it)? (y or n)
17658 If you type @kbd{y}, @value{GDBN} abandons the remote debugging session.
17659 (If you decide you want to try again later, you can use @samp{target
17660 remote} again to connect once more.) If you type @kbd{n}, @value{GDBN}
17661 goes back to waiting.
17664 @kindex detach (remote)
17666 When you have finished debugging the remote program, you can use the
17667 @code{detach} command to release it from @value{GDBN} control.
17668 Detaching from the target normally resumes its execution, but the results
17669 will depend on your particular remote stub. After the @code{detach}
17670 command, @value{GDBN} is free to connect to another target.
17674 The @code{disconnect} command behaves like @code{detach}, except that
17675 the target is generally not resumed. It will wait for @value{GDBN}
17676 (this instance or another one) to connect and continue debugging. After
17677 the @code{disconnect} command, @value{GDBN} is again free to connect to
17680 @cindex send command to remote monitor
17681 @cindex extend @value{GDBN} for remote targets
17682 @cindex add new commands for external monitor
17684 @item monitor @var{cmd}
17685 This command allows you to send arbitrary commands directly to the
17686 remote monitor. Since @value{GDBN} doesn't care about the commands it
17687 sends like this, this command is the way to extend @value{GDBN}---you
17688 can add new commands that only the external monitor will understand
17692 @node File Transfer
17693 @section Sending files to a remote system
17694 @cindex remote target, file transfer
17695 @cindex file transfer
17696 @cindex sending files to remote systems
17698 Some remote targets offer the ability to transfer files over the same
17699 connection used to communicate with @value{GDBN}. This is convenient
17700 for targets accessible through other means, e.g.@: @sc{gnu}/Linux systems
17701 running @code{gdbserver} over a network interface. For other targets,
17702 e.g.@: embedded devices with only a single serial port, this may be
17703 the only way to upload or download files.
17705 Not all remote targets support these commands.
17709 @item remote put @var{hostfile} @var{targetfile}
17710 Copy file @var{hostfile} from the host system (the machine running
17711 @value{GDBN}) to @var{targetfile} on the target system.
17714 @item remote get @var{targetfile} @var{hostfile}
17715 Copy file @var{targetfile} from the target system to @var{hostfile}
17716 on the host system.
17718 @kindex remote delete
17719 @item remote delete @var{targetfile}
17720 Delete @var{targetfile} from the target system.
17725 @section Using the @code{gdbserver} Program
17728 @cindex remote connection without stubs
17729 @code{gdbserver} is a control program for Unix-like systems, which
17730 allows you to connect your program with a remote @value{GDBN} via
17731 @code{target remote}---but without linking in the usual debugging stub.
17733 @code{gdbserver} is not a complete replacement for the debugging stubs,
17734 because it requires essentially the same operating-system facilities
17735 that @value{GDBN} itself does. In fact, a system that can run
17736 @code{gdbserver} to connect to a remote @value{GDBN} could also run
17737 @value{GDBN} locally! @code{gdbserver} is sometimes useful nevertheless,
17738 because it is a much smaller program than @value{GDBN} itself. It is
17739 also easier to port than all of @value{GDBN}, so you may be able to get
17740 started more quickly on a new system by using @code{gdbserver}.
17741 Finally, if you develop code for real-time systems, you may find that
17742 the tradeoffs involved in real-time operation make it more convenient to
17743 do as much development work as possible on another system, for example
17744 by cross-compiling. You can use @code{gdbserver} to make a similar
17745 choice for debugging.
17747 @value{GDBN} and @code{gdbserver} communicate via either a serial line
17748 or a TCP connection, using the standard @value{GDBN} remote serial
17752 @emph{Warning:} @code{gdbserver} does not have any built-in security.
17753 Do not run @code{gdbserver} connected to any public network; a
17754 @value{GDBN} connection to @code{gdbserver} provides access to the
17755 target system with the same privileges as the user running
17759 @subsection Running @code{gdbserver}
17760 @cindex arguments, to @code{gdbserver}
17761 @cindex @code{gdbserver}, command-line arguments
17763 Run @code{gdbserver} on the target system. You need a copy of the
17764 program you want to debug, including any libraries it requires.
17765 @code{gdbserver} does not need your program's symbol table, so you can
17766 strip the program if necessary to save space. @value{GDBN} on the host
17767 system does all the symbol handling.
17769 To use the server, you must tell it how to communicate with @value{GDBN};
17770 the name of your program; and the arguments for your program. The usual
17774 target> gdbserver @var{comm} @var{program} [ @var{args} @dots{} ]
17777 @var{comm} is either a device name (to use a serial line), or a TCP
17778 hostname and portnumber, or @code{-} or @code{stdio} to use
17779 stdin/stdout of @code{gdbserver}.
17780 For example, to debug Emacs with the argument
17781 @samp{foo.txt} and communicate with @value{GDBN} over the serial port
17785 target> gdbserver /dev/com1 emacs foo.txt
17788 @code{gdbserver} waits passively for the host @value{GDBN} to communicate
17791 To use a TCP connection instead of a serial line:
17794 target> gdbserver host:2345 emacs foo.txt
17797 The only difference from the previous example is the first argument,
17798 specifying that you are communicating with the host @value{GDBN} via
17799 TCP. The @samp{host:2345} argument means that @code{gdbserver} is to
17800 expect a TCP connection from machine @samp{host} to local TCP port 2345.
17801 (Currently, the @samp{host} part is ignored.) You can choose any number
17802 you want for the port number as long as it does not conflict with any
17803 TCP ports already in use on the target system (for example, @code{23} is
17804 reserved for @code{telnet}).@footnote{If you choose a port number that
17805 conflicts with another service, @code{gdbserver} prints an error message
17806 and exits.} You must use the same port number with the host @value{GDBN}
17807 @code{target remote} command.
17809 The @code{stdio} connection is useful when starting @code{gdbserver}
17813 (gdb) target remote | ssh -T hostname gdbserver - hello
17816 The @samp{-T} option to ssh is provided because we don't need a remote pty,
17817 and we don't want escape-character handling. Ssh does this by default when
17818 a command is provided, the flag is provided to make it explicit.
17819 You could elide it if you want to.
17821 Programs started with stdio-connected gdbserver have @file{/dev/null} for
17822 @code{stdin}, and @code{stdout},@code{stderr} are sent back to gdb for
17823 display through a pipe connected to gdbserver.
17824 Both @code{stdout} and @code{stderr} use the same pipe.
17826 @subsubsection Attaching to a Running Program
17827 @cindex attach to a program, @code{gdbserver}
17828 @cindex @option{--attach}, @code{gdbserver} option
17830 On some targets, @code{gdbserver} can also attach to running programs.
17831 This is accomplished via the @code{--attach} argument. The syntax is:
17834 target> gdbserver --attach @var{comm} @var{pid}
17837 @var{pid} is the process ID of a currently running process. It isn't necessary
17838 to point @code{gdbserver} at a binary for the running process.
17841 You can debug processes by name instead of process ID if your target has the
17842 @code{pidof} utility:
17845 target> gdbserver --attach @var{comm} `pidof @var{program}`
17848 In case more than one copy of @var{program} is running, or @var{program}
17849 has multiple threads, most versions of @code{pidof} support the
17850 @code{-s} option to only return the first process ID.
17852 @subsubsection Multi-Process Mode for @code{gdbserver}
17853 @cindex @code{gdbserver}, multiple processes
17854 @cindex multiple processes with @code{gdbserver}
17856 When you connect to @code{gdbserver} using @code{target remote},
17857 @code{gdbserver} debugs the specified program only once. When the
17858 program exits, or you detach from it, @value{GDBN} closes the connection
17859 and @code{gdbserver} exits.
17861 If you connect using @kbd{target extended-remote}, @code{gdbserver}
17862 enters multi-process mode. When the debugged program exits, or you
17863 detach from it, @value{GDBN} stays connected to @code{gdbserver} even
17864 though no program is running. The @code{run} and @code{attach}
17865 commands instruct @code{gdbserver} to run or attach to a new program.
17866 The @code{run} command uses @code{set remote exec-file} (@pxref{set
17867 remote exec-file}) to select the program to run. Command line
17868 arguments are supported, except for wildcard expansion and I/O
17869 redirection (@pxref{Arguments}).
17871 @cindex @option{--multi}, @code{gdbserver} option
17872 To start @code{gdbserver} without supplying an initial command to run
17873 or process ID to attach, use the @option{--multi} command line option.
17874 Then you can connect using @kbd{target extended-remote} and start
17875 the program you want to debug.
17877 In multi-process mode @code{gdbserver} does not automatically exit unless you
17878 use the option @option{--once}. You can terminate it by using
17879 @code{monitor exit} (@pxref{Monitor Commands for gdbserver}). Note that the
17880 conditions under which @code{gdbserver} terminates depend on how @value{GDBN}
17881 connects to it (@kbd{target remote} or @kbd{target extended-remote}). The
17882 @option{--multi} option to @code{gdbserver} has no influence on that.
17884 @subsubsection TCP port allocation lifecycle of @code{gdbserver}
17886 This section applies only when @code{gdbserver} is run to listen on a TCP port.
17888 @code{gdbserver} normally terminates after all of its debugged processes have
17889 terminated in @kbd{target remote} mode. On the other hand, for @kbd{target
17890 extended-remote}, @code{gdbserver} stays running even with no processes left.
17891 @value{GDBN} normally terminates the spawned debugged process on its exit,
17892 which normally also terminates @code{gdbserver} in the @kbd{target remote}
17893 mode. Therefore, when the connection drops unexpectedly, and @value{GDBN}
17894 cannot ask @code{gdbserver} to kill its debugged processes, @code{gdbserver}
17895 stays running even in the @kbd{target remote} mode.
17897 When @code{gdbserver} stays running, @value{GDBN} can connect to it again later.
17898 Such reconnecting is useful for features like @ref{disconnected tracing}. For
17899 completeness, at most one @value{GDBN} can be connected at a time.
17901 @cindex @option{--once}, @code{gdbserver} option
17902 By default, @code{gdbserver} keeps the listening TCP port open, so that
17903 additional connections are possible. However, if you start @code{gdbserver}
17904 with the @option{--once} option, it will stop listening for any further
17905 connection attempts after connecting to the first @value{GDBN} session. This
17906 means no further connections to @code{gdbserver} will be possible after the
17907 first one. It also means @code{gdbserver} will terminate after the first
17908 connection with remote @value{GDBN} has closed, even for unexpectedly closed
17909 connections and even in the @kbd{target extended-remote} mode. The
17910 @option{--once} option allows reusing the same port number for connecting to
17911 multiple instances of @code{gdbserver} running on the same host, since each
17912 instance closes its port after the first connection.
17914 @subsubsection Other Command-Line Arguments for @code{gdbserver}
17916 @cindex @option{--debug}, @code{gdbserver} option
17917 The @option{--debug} option tells @code{gdbserver} to display extra
17918 status information about the debugging process.
17919 @cindex @option{--remote-debug}, @code{gdbserver} option
17920 The @option{--remote-debug} option tells @code{gdbserver} to display
17921 remote protocol debug output. These options are intended for
17922 @code{gdbserver} development and for bug reports to the developers.
17924 @cindex @option{--wrapper}, @code{gdbserver} option
17925 The @option{--wrapper} option specifies a wrapper to launch programs
17926 for debugging. The option should be followed by the name of the
17927 wrapper, then any command-line arguments to pass to the wrapper, then
17928 @kbd{--} indicating the end of the wrapper arguments.
17930 @code{gdbserver} runs the specified wrapper program with a combined
17931 command line including the wrapper arguments, then the name of the
17932 program to debug, then any arguments to the program. The wrapper
17933 runs until it executes your program, and then @value{GDBN} gains control.
17935 You can use any program that eventually calls @code{execve} with
17936 its arguments as a wrapper. Several standard Unix utilities do
17937 this, e.g.@: @code{env} and @code{nohup}. Any Unix shell script ending
17938 with @code{exec "$@@"} will also work.
17940 For example, you can use @code{env} to pass an environment variable to
17941 the debugged program, without setting the variable in @code{gdbserver}'s
17945 $ gdbserver --wrapper env LD_PRELOAD=libtest.so -- :2222 ./testprog
17948 @subsection Connecting to @code{gdbserver}
17950 Run @value{GDBN} on the host system.
17952 First make sure you have the necessary symbol files. Load symbols for
17953 your application using the @code{file} command before you connect. Use
17954 @code{set sysroot} to locate target libraries (unless your @value{GDBN}
17955 was compiled with the correct sysroot using @code{--with-sysroot}).
17957 The symbol file and target libraries must exactly match the executable
17958 and libraries on the target, with one exception: the files on the host
17959 system should not be stripped, even if the files on the target system
17960 are. Mismatched or missing files will lead to confusing results
17961 during debugging. On @sc{gnu}/Linux targets, mismatched or missing
17962 files may also prevent @code{gdbserver} from debugging multi-threaded
17965 Connect to your target (@pxref{Connecting,,Connecting to a Remote Target}).
17966 For TCP connections, you must start up @code{gdbserver} prior to using
17967 the @code{target remote} command. Otherwise you may get an error whose
17968 text depends on the host system, but which usually looks something like
17969 @samp{Connection refused}. Don't use the @code{load}
17970 command in @value{GDBN} when using @code{gdbserver}, since the program is
17971 already on the target.
17973 @subsection Monitor Commands for @code{gdbserver}
17974 @cindex monitor commands, for @code{gdbserver}
17975 @anchor{Monitor Commands for gdbserver}
17977 During a @value{GDBN} session using @code{gdbserver}, you can use the
17978 @code{monitor} command to send special requests to @code{gdbserver}.
17979 Here are the available commands.
17983 List the available monitor commands.
17985 @item monitor set debug 0
17986 @itemx monitor set debug 1
17987 Disable or enable general debugging messages.
17989 @item monitor set remote-debug 0
17990 @itemx monitor set remote-debug 1
17991 Disable or enable specific debugging messages associated with the remote
17992 protocol (@pxref{Remote Protocol}).
17994 @item monitor set libthread-db-search-path [PATH]
17995 @cindex gdbserver, search path for @code{libthread_db}
17996 When this command is issued, @var{path} is a colon-separated list of
17997 directories to search for @code{libthread_db} (@pxref{Threads,,set
17998 libthread-db-search-path}). If you omit @var{path},
17999 @samp{libthread-db-search-path} will be reset to its default value.
18001 The special entry @samp{$pdir} for @samp{libthread-db-search-path} is
18002 not supported in @code{gdbserver}.
18005 Tell gdbserver to exit immediately. This command should be followed by
18006 @code{disconnect} to close the debugging session. @code{gdbserver} will
18007 detach from any attached processes and kill any processes it created.
18008 Use @code{monitor exit} to terminate @code{gdbserver} at the end
18009 of a multi-process mode debug session.
18013 @subsection Tracepoints support in @code{gdbserver}
18014 @cindex tracepoints support in @code{gdbserver}
18016 On some targets, @code{gdbserver} supports tracepoints, fast
18017 tracepoints and static tracepoints.
18019 For fast or static tracepoints to work, a special library called the
18020 @dfn{in-process agent} (IPA), must be loaded in the inferior process.
18021 This library is built and distributed as an integral part of
18022 @code{gdbserver}. In addition, support for static tracepoints
18023 requires building the in-process agent library with static tracepoints
18024 support. At present, the UST (LTTng Userspace Tracer,
18025 @url{http://lttng.org/ust}) tracing engine is supported. This support
18026 is automatically available if UST development headers are found in the
18027 standard include path when @code{gdbserver} is built, or if
18028 @code{gdbserver} was explicitly configured using @option{--with-ust}
18029 to point at such headers. You can explicitly disable the support
18030 using @option{--with-ust=no}.
18032 There are several ways to load the in-process agent in your program:
18035 @item Specifying it as dependency at link time
18037 You can link your program dynamically with the in-process agent
18038 library. On most systems, this is accomplished by adding
18039 @code{-linproctrace} to the link command.
18041 @item Using the system's preloading mechanisms
18043 You can force loading the in-process agent at startup time by using
18044 your system's support for preloading shared libraries. Many Unixes
18045 support the concept of preloading user defined libraries. In most
18046 cases, you do that by specifying @code{LD_PRELOAD=libinproctrace.so}
18047 in the environment. See also the description of @code{gdbserver}'s
18048 @option{--wrapper} command line option.
18050 @item Using @value{GDBN} to force loading the agent at run time
18052 On some systems, you can force the inferior to load a shared library,
18053 by calling a dynamic loader function in the inferior that takes care
18054 of dynamically looking up and loading a shared library. On most Unix
18055 systems, the function is @code{dlopen}. You'll use the @code{call}
18056 command for that. For example:
18059 (@value{GDBP}) call dlopen ("libinproctrace.so", ...)
18062 Note that on most Unix systems, for the @code{dlopen} function to be
18063 available, the program needs to be linked with @code{-ldl}.
18066 On systems that have a userspace dynamic loader, like most Unix
18067 systems, when you connect to @code{gdbserver} using @code{target
18068 remote}, you'll find that the program is stopped at the dynamic
18069 loader's entry point, and no shared library has been loaded in the
18070 program's address space yet, including the in-process agent. In that
18071 case, before being able to use any of the fast or static tracepoints
18072 features, you need to let the loader run and load the shared
18073 libraries. The simplest way to do that is to run the program to the
18074 main procedure. E.g., if debugging a C or C@t{++} program, start
18075 @code{gdbserver} like so:
18078 $ gdbserver :9999 myprogram
18081 Start GDB and connect to @code{gdbserver} like so, and run to main:
18085 (@value{GDBP}) target remote myhost:9999
18086 0x00007f215893ba60 in ?? () from /lib64/ld-linux-x86-64.so.2
18087 (@value{GDBP}) b main
18088 (@value{GDBP}) continue
18091 The in-process tracing agent library should now be loaded into the
18092 process; you can confirm it with the @code{info sharedlibrary}
18093 command, which will list @file{libinproctrace.so} as loaded in the
18094 process. You are now ready to install fast tracepoints, list static
18095 tracepoint markers, probe static tracepoints markers, and start
18098 @node Remote Configuration
18099 @section Remote Configuration
18102 @kindex show remote
18103 This section documents the configuration options available when
18104 debugging remote programs. For the options related to the File I/O
18105 extensions of the remote protocol, see @ref{system,
18106 system-call-allowed}.
18109 @item set remoteaddresssize @var{bits}
18110 @cindex address size for remote targets
18111 @cindex bits in remote address
18112 Set the maximum size of address in a memory packet to the specified
18113 number of bits. @value{GDBN} will mask off the address bits above
18114 that number, when it passes addresses to the remote target. The
18115 default value is the number of bits in the target's address.
18117 @item show remoteaddresssize
18118 Show the current value of remote address size in bits.
18120 @item set remotebaud @var{n}
18121 @cindex baud rate for remote targets
18122 Set the baud rate for the remote serial I/O to @var{n} baud. The
18123 value is used to set the speed of the serial port used for debugging
18126 @item show remotebaud
18127 Show the current speed of the remote connection.
18129 @item set remotebreak
18130 @cindex interrupt remote programs
18131 @cindex BREAK signal instead of Ctrl-C
18132 @anchor{set remotebreak}
18133 If set to on, @value{GDBN} sends a @code{BREAK} signal to the remote
18134 when you type @kbd{Ctrl-c} to interrupt the program running
18135 on the remote. If set to off, @value{GDBN} sends the @samp{Ctrl-C}
18136 character instead. The default is off, since most remote systems
18137 expect to see @samp{Ctrl-C} as the interrupt signal.
18139 @item show remotebreak
18140 Show whether @value{GDBN} sends @code{BREAK} or @samp{Ctrl-C} to
18141 interrupt the remote program.
18143 @item set remoteflow on
18144 @itemx set remoteflow off
18145 @kindex set remoteflow
18146 Enable or disable hardware flow control (@code{RTS}/@code{CTS})
18147 on the serial port used to communicate to the remote target.
18149 @item show remoteflow
18150 @kindex show remoteflow
18151 Show the current setting of hardware flow control.
18153 @item set remotelogbase @var{base}
18154 Set the base (a.k.a.@: radix) of logging serial protocol
18155 communications to @var{base}. Supported values of @var{base} are:
18156 @code{ascii}, @code{octal}, and @code{hex}. The default is
18159 @item show remotelogbase
18160 Show the current setting of the radix for logging remote serial
18163 @item set remotelogfile @var{file}
18164 @cindex record serial communications on file
18165 Record remote serial communications on the named @var{file}. The
18166 default is not to record at all.
18168 @item show remotelogfile.
18169 Show the current setting of the file name on which to record the
18170 serial communications.
18172 @item set remotetimeout @var{num}
18173 @cindex timeout for serial communications
18174 @cindex remote timeout
18175 Set the timeout limit to wait for the remote target to respond to
18176 @var{num} seconds. The default is 2 seconds.
18178 @item show remotetimeout
18179 Show the current number of seconds to wait for the remote target
18182 @cindex limit hardware breakpoints and watchpoints
18183 @cindex remote target, limit break- and watchpoints
18184 @anchor{set remote hardware-watchpoint-limit}
18185 @anchor{set remote hardware-breakpoint-limit}
18186 @item set remote hardware-watchpoint-limit @var{limit}
18187 @itemx set remote hardware-breakpoint-limit @var{limit}
18188 Restrict @value{GDBN} to using @var{limit} remote hardware breakpoint or
18189 watchpoints. A limit of -1, the default, is treated as unlimited.
18191 @cindex limit hardware watchpoints length
18192 @cindex remote target, limit watchpoints length
18193 @anchor{set remote hardware-watchpoint-length-limit}
18194 @item set remote hardware-watchpoint-length-limit @var{limit}
18195 Restrict @value{GDBN} to using @var{limit} bytes for the maximum length of
18196 a remote hardware watchpoint. A limit of -1, the default, is treated
18199 @item show remote hardware-watchpoint-length-limit
18200 Show the current limit (in bytes) of the maximum length of
18201 a remote hardware watchpoint.
18203 @item set remote exec-file @var{filename}
18204 @itemx show remote exec-file
18205 @anchor{set remote exec-file}
18206 @cindex executable file, for remote target
18207 Select the file used for @code{run} with @code{target
18208 extended-remote}. This should be set to a filename valid on the
18209 target system. If it is not set, the target will use a default
18210 filename (e.g.@: the last program run).
18212 @item set remote interrupt-sequence
18213 @cindex interrupt remote programs
18214 @cindex select Ctrl-C, BREAK or BREAK-g
18215 Allow the user to select one of @samp{Ctrl-C}, a @code{BREAK} or
18216 @samp{BREAK-g} as the
18217 sequence to the remote target in order to interrupt the execution.
18218 @samp{Ctrl-C} is a default. Some system prefers @code{BREAK} which
18219 is high level of serial line for some certain time.
18220 Linux kernel prefers @samp{BREAK-g}, a.k.a Magic SysRq g.
18221 It is @code{BREAK} signal followed by character @code{g}.
18223 @item show interrupt-sequence
18224 Show which of @samp{Ctrl-C}, @code{BREAK} or @code{BREAK-g}
18225 is sent by @value{GDBN} to interrupt the remote program.
18226 @code{BREAK-g} is BREAK signal followed by @code{g} and
18227 also known as Magic SysRq g.
18229 @item set remote interrupt-on-connect
18230 @cindex send interrupt-sequence on start
18231 Specify whether interrupt-sequence is sent to remote target when
18232 @value{GDBN} connects to it. This is mostly needed when you debug
18233 Linux kernel. Linux kernel expects @code{BREAK} followed by @code{g}
18234 which is known as Magic SysRq g in order to connect @value{GDBN}.
18236 @item show interrupt-on-connect
18237 Show whether interrupt-sequence is sent
18238 to remote target when @value{GDBN} connects to it.
18242 @item set tcp auto-retry on
18243 @cindex auto-retry, for remote TCP target
18244 Enable auto-retry for remote TCP connections. This is useful if the remote
18245 debugging agent is launched in parallel with @value{GDBN}; there is a race
18246 condition because the agent may not become ready to accept the connection
18247 before @value{GDBN} attempts to connect. When auto-retry is
18248 enabled, if the initial attempt to connect fails, @value{GDBN} reattempts
18249 to establish the connection using the timeout specified by
18250 @code{set tcp connect-timeout}.
18252 @item set tcp auto-retry off
18253 Do not auto-retry failed TCP connections.
18255 @item show tcp auto-retry
18256 Show the current auto-retry setting.
18258 @item set tcp connect-timeout @var{seconds}
18259 @cindex connection timeout, for remote TCP target
18260 @cindex timeout, for remote target connection
18261 Set the timeout for establishing a TCP connection to the remote target to
18262 @var{seconds}. The timeout affects both polling to retry failed connections
18263 (enabled by @code{set tcp auto-retry on}) and waiting for connections
18264 that are merely slow to complete, and represents an approximate cumulative
18267 @item show tcp connect-timeout
18268 Show the current connection timeout setting.
18271 @cindex remote packets, enabling and disabling
18272 The @value{GDBN} remote protocol autodetects the packets supported by
18273 your debugging stub. If you need to override the autodetection, you
18274 can use these commands to enable or disable individual packets. Each
18275 packet can be set to @samp{on} (the remote target supports this
18276 packet), @samp{off} (the remote target does not support this packet),
18277 or @samp{auto} (detect remote target support for this packet). They
18278 all default to @samp{auto}. For more information about each packet,
18279 see @ref{Remote Protocol}.
18281 During normal use, you should not have to use any of these commands.
18282 If you do, that may be a bug in your remote debugging stub, or a bug
18283 in @value{GDBN}. You may want to report the problem to the
18284 @value{GDBN} developers.
18286 For each packet @var{name}, the command to enable or disable the
18287 packet is @code{set remote @var{name}-packet}. The available settings
18290 @multitable @columnfractions 0.28 0.32 0.25
18293 @tab Related Features
18295 @item @code{fetch-register}
18297 @tab @code{info registers}
18299 @item @code{set-register}
18303 @item @code{binary-download}
18305 @tab @code{load}, @code{set}
18307 @item @code{read-aux-vector}
18308 @tab @code{qXfer:auxv:read}
18309 @tab @code{info auxv}
18311 @item @code{symbol-lookup}
18312 @tab @code{qSymbol}
18313 @tab Detecting multiple threads
18315 @item @code{attach}
18316 @tab @code{vAttach}
18319 @item @code{verbose-resume}
18321 @tab Stepping or resuming multiple threads
18327 @item @code{software-breakpoint}
18331 @item @code{hardware-breakpoint}
18335 @item @code{write-watchpoint}
18339 @item @code{read-watchpoint}
18343 @item @code{access-watchpoint}
18347 @item @code{target-features}
18348 @tab @code{qXfer:features:read}
18349 @tab @code{set architecture}
18351 @item @code{library-info}
18352 @tab @code{qXfer:libraries:read}
18353 @tab @code{info sharedlibrary}
18355 @item @code{memory-map}
18356 @tab @code{qXfer:memory-map:read}
18357 @tab @code{info mem}
18359 @item @code{read-sdata-object}
18360 @tab @code{qXfer:sdata:read}
18361 @tab @code{print $_sdata}
18363 @item @code{read-spu-object}
18364 @tab @code{qXfer:spu:read}
18365 @tab @code{info spu}
18367 @item @code{write-spu-object}
18368 @tab @code{qXfer:spu:write}
18369 @tab @code{info spu}
18371 @item @code{read-siginfo-object}
18372 @tab @code{qXfer:siginfo:read}
18373 @tab @code{print $_siginfo}
18375 @item @code{write-siginfo-object}
18376 @tab @code{qXfer:siginfo:write}
18377 @tab @code{set $_siginfo}
18379 @item @code{threads}
18380 @tab @code{qXfer:threads:read}
18381 @tab @code{info threads}
18383 @item @code{get-thread-local-@*storage-address}
18384 @tab @code{qGetTLSAddr}
18385 @tab Displaying @code{__thread} variables
18387 @item @code{get-thread-information-block-address}
18388 @tab @code{qGetTIBAddr}
18389 @tab Display MS-Windows Thread Information Block.
18391 @item @code{search-memory}
18392 @tab @code{qSearch:memory}
18395 @item @code{supported-packets}
18396 @tab @code{qSupported}
18397 @tab Remote communications parameters
18399 @item @code{pass-signals}
18400 @tab @code{QPassSignals}
18401 @tab @code{handle @var{signal}}
18403 @item @code{program-signals}
18404 @tab @code{QProgramSignals}
18405 @tab @code{handle @var{signal}}
18407 @item @code{hostio-close-packet}
18408 @tab @code{vFile:close}
18409 @tab @code{remote get}, @code{remote put}
18411 @item @code{hostio-open-packet}
18412 @tab @code{vFile:open}
18413 @tab @code{remote get}, @code{remote put}
18415 @item @code{hostio-pread-packet}
18416 @tab @code{vFile:pread}
18417 @tab @code{remote get}, @code{remote put}
18419 @item @code{hostio-pwrite-packet}
18420 @tab @code{vFile:pwrite}
18421 @tab @code{remote get}, @code{remote put}
18423 @item @code{hostio-unlink-packet}
18424 @tab @code{vFile:unlink}
18425 @tab @code{remote delete}
18427 @item @code{hostio-readlink-packet}
18428 @tab @code{vFile:readlink}
18431 @item @code{noack-packet}
18432 @tab @code{QStartNoAckMode}
18433 @tab Packet acknowledgment
18435 @item @code{osdata}
18436 @tab @code{qXfer:osdata:read}
18437 @tab @code{info os}
18439 @item @code{query-attached}
18440 @tab @code{qAttached}
18441 @tab Querying remote process attach state.
18443 @item @code{traceframe-info}
18444 @tab @code{qXfer:traceframe-info:read}
18445 @tab Traceframe info
18447 @item @code{install-in-trace}
18448 @tab @code{InstallInTrace}
18449 @tab Install tracepoint in tracing
18451 @item @code{disable-randomization}
18452 @tab @code{QDisableRandomization}
18453 @tab @code{set disable-randomization}
18455 @item @code{conditional-breakpoints-packet}
18456 @tab @code{Z0 and Z1}
18457 @tab @code{Support for target-side breakpoint condition evaluation}
18461 @section Implementing a Remote Stub
18463 @cindex debugging stub, example
18464 @cindex remote stub, example
18465 @cindex stub example, remote debugging
18466 The stub files provided with @value{GDBN} implement the target side of the
18467 communication protocol, and the @value{GDBN} side is implemented in the
18468 @value{GDBN} source file @file{remote.c}. Normally, you can simply allow
18469 these subroutines to communicate, and ignore the details. (If you're
18470 implementing your own stub file, you can still ignore the details: start
18471 with one of the existing stub files. @file{sparc-stub.c} is the best
18472 organized, and therefore the easiest to read.)
18474 @cindex remote serial debugging, overview
18475 To debug a program running on another machine (the debugging
18476 @dfn{target} machine), you must first arrange for all the usual
18477 prerequisites for the program to run by itself. For example, for a C
18482 A startup routine to set up the C runtime environment; these usually
18483 have a name like @file{crt0}. The startup routine may be supplied by
18484 your hardware supplier, or you may have to write your own.
18487 A C subroutine library to support your program's
18488 subroutine calls, notably managing input and output.
18491 A way of getting your program to the other machine---for example, a
18492 download program. These are often supplied by the hardware
18493 manufacturer, but you may have to write your own from hardware
18497 The next step is to arrange for your program to use a serial port to
18498 communicate with the machine where @value{GDBN} is running (the @dfn{host}
18499 machine). In general terms, the scheme looks like this:
18503 @value{GDBN} already understands how to use this protocol; when everything
18504 else is set up, you can simply use the @samp{target remote} command
18505 (@pxref{Targets,,Specifying a Debugging Target}).
18507 @item On the target,
18508 you must link with your program a few special-purpose subroutines that
18509 implement the @value{GDBN} remote serial protocol. The file containing these
18510 subroutines is called a @dfn{debugging stub}.
18512 On certain remote targets, you can use an auxiliary program
18513 @code{gdbserver} instead of linking a stub into your program.
18514 @xref{Server,,Using the @code{gdbserver} Program}, for details.
18517 The debugging stub is specific to the architecture of the remote
18518 machine; for example, use @file{sparc-stub.c} to debug programs on
18521 @cindex remote serial stub list
18522 These working remote stubs are distributed with @value{GDBN}:
18527 @cindex @file{i386-stub.c}
18530 For Intel 386 and compatible architectures.
18533 @cindex @file{m68k-stub.c}
18534 @cindex Motorola 680x0
18536 For Motorola 680x0 architectures.
18539 @cindex @file{sh-stub.c}
18542 For Renesas SH architectures.
18545 @cindex @file{sparc-stub.c}
18547 For @sc{sparc} architectures.
18549 @item sparcl-stub.c
18550 @cindex @file{sparcl-stub.c}
18553 For Fujitsu @sc{sparclite} architectures.
18557 The @file{README} file in the @value{GDBN} distribution may list other
18558 recently added stubs.
18561 * Stub Contents:: What the stub can do for you
18562 * Bootstrapping:: What you must do for the stub
18563 * Debug Session:: Putting it all together
18566 @node Stub Contents
18567 @subsection What the Stub Can Do for You
18569 @cindex remote serial stub
18570 The debugging stub for your architecture supplies these three
18574 @item set_debug_traps
18575 @findex set_debug_traps
18576 @cindex remote serial stub, initialization
18577 This routine arranges for @code{handle_exception} to run when your
18578 program stops. You must call this subroutine explicitly in your
18579 program's startup code.
18581 @item handle_exception
18582 @findex handle_exception
18583 @cindex remote serial stub, main routine
18584 This is the central workhorse, but your program never calls it
18585 explicitly---the setup code arranges for @code{handle_exception} to
18586 run when a trap is triggered.
18588 @code{handle_exception} takes control when your program stops during
18589 execution (for example, on a breakpoint), and mediates communications
18590 with @value{GDBN} on the host machine. This is where the communications
18591 protocol is implemented; @code{handle_exception} acts as the @value{GDBN}
18592 representative on the target machine. It begins by sending summary
18593 information on the state of your program, then continues to execute,
18594 retrieving and transmitting any information @value{GDBN} needs, until you
18595 execute a @value{GDBN} command that makes your program resume; at that point,
18596 @code{handle_exception} returns control to your own code on the target
18600 @cindex @code{breakpoint} subroutine, remote
18601 Use this auxiliary subroutine to make your program contain a
18602 breakpoint. Depending on the particular situation, this may be the only
18603 way for @value{GDBN} to get control. For instance, if your target
18604 machine has some sort of interrupt button, you won't need to call this;
18605 pressing the interrupt button transfers control to
18606 @code{handle_exception}---in effect, to @value{GDBN}. On some machines,
18607 simply receiving characters on the serial port may also trigger a trap;
18608 again, in that situation, you don't need to call @code{breakpoint} from
18609 your own program---simply running @samp{target remote} from the host
18610 @value{GDBN} session gets control.
18612 Call @code{breakpoint} if none of these is true, or if you simply want
18613 to make certain your program stops at a predetermined point for the
18614 start of your debugging session.
18617 @node Bootstrapping
18618 @subsection What You Must Do for the Stub
18620 @cindex remote stub, support routines
18621 The debugging stubs that come with @value{GDBN} are set up for a particular
18622 chip architecture, but they have no information about the rest of your
18623 debugging target machine.
18625 First of all you need to tell the stub how to communicate with the
18629 @item int getDebugChar()
18630 @findex getDebugChar
18631 Write this subroutine to read a single character from the serial port.
18632 It may be identical to @code{getchar} for your target system; a
18633 different name is used to allow you to distinguish the two if you wish.
18635 @item void putDebugChar(int)
18636 @findex putDebugChar
18637 Write this subroutine to write a single character to the serial port.
18638 It may be identical to @code{putchar} for your target system; a
18639 different name is used to allow you to distinguish the two if you wish.
18642 @cindex control C, and remote debugging
18643 @cindex interrupting remote targets
18644 If you want @value{GDBN} to be able to stop your program while it is
18645 running, you need to use an interrupt-driven serial driver, and arrange
18646 for it to stop when it receives a @code{^C} (@samp{\003}, the control-C
18647 character). That is the character which @value{GDBN} uses to tell the
18648 remote system to stop.
18650 Getting the debugging target to return the proper status to @value{GDBN}
18651 probably requires changes to the standard stub; one quick and dirty way
18652 is to just execute a breakpoint instruction (the ``dirty'' part is that
18653 @value{GDBN} reports a @code{SIGTRAP} instead of a @code{SIGINT}).
18655 Other routines you need to supply are:
18658 @item void exceptionHandler (int @var{exception_number}, void *@var{exception_address})
18659 @findex exceptionHandler
18660 Write this function to install @var{exception_address} in the exception
18661 handling tables. You need to do this because the stub does not have any
18662 way of knowing what the exception handling tables on your target system
18663 are like (for example, the processor's table might be in @sc{rom},
18664 containing entries which point to a table in @sc{ram}).
18665 @var{exception_number} is the exception number which should be changed;
18666 its meaning is architecture-dependent (for example, different numbers
18667 might represent divide by zero, misaligned access, etc). When this
18668 exception occurs, control should be transferred directly to
18669 @var{exception_address}, and the processor state (stack, registers,
18670 and so on) should be just as it is when a processor exception occurs. So if
18671 you want to use a jump instruction to reach @var{exception_address}, it
18672 should be a simple jump, not a jump to subroutine.
18674 For the 386, @var{exception_address} should be installed as an interrupt
18675 gate so that interrupts are masked while the handler runs. The gate
18676 should be at privilege level 0 (the most privileged level). The
18677 @sc{sparc} and 68k stubs are able to mask interrupts themselves without
18678 help from @code{exceptionHandler}.
18680 @item void flush_i_cache()
18681 @findex flush_i_cache
18682 On @sc{sparc} and @sc{sparclite} only, write this subroutine to flush the
18683 instruction cache, if any, on your target machine. If there is no
18684 instruction cache, this subroutine may be a no-op.
18686 On target machines that have instruction caches, @value{GDBN} requires this
18687 function to make certain that the state of your program is stable.
18691 You must also make sure this library routine is available:
18694 @item void *memset(void *, int, int)
18696 This is the standard library function @code{memset} that sets an area of
18697 memory to a known value. If you have one of the free versions of
18698 @code{libc.a}, @code{memset} can be found there; otherwise, you must
18699 either obtain it from your hardware manufacturer, or write your own.
18702 If you do not use the GNU C compiler, you may need other standard
18703 library subroutines as well; this varies from one stub to another,
18704 but in general the stubs are likely to use any of the common library
18705 subroutines which @code{@value{NGCC}} generates as inline code.
18708 @node Debug Session
18709 @subsection Putting it All Together
18711 @cindex remote serial debugging summary
18712 In summary, when your program is ready to debug, you must follow these
18717 Make sure you have defined the supporting low-level routines
18718 (@pxref{Bootstrapping,,What You Must Do for the Stub}):
18720 @code{getDebugChar}, @code{putDebugChar},
18721 @code{flush_i_cache}, @code{memset}, @code{exceptionHandler}.
18725 Insert these lines in your program's startup code, before the main
18726 procedure is called:
18733 On some machines, when a breakpoint trap is raised, the hardware
18734 automatically makes the PC point to the instruction after the
18735 breakpoint. If your machine doesn't do that, you may need to adjust
18736 @code{handle_exception} to arrange for it to return to the instruction
18737 after the breakpoint on this first invocation, so that your program
18738 doesn't keep hitting the initial breakpoint instead of making
18742 For the 680x0 stub only, you need to provide a variable called
18743 @code{exceptionHook}. Normally you just use:
18746 void (*exceptionHook)() = 0;
18750 but if before calling @code{set_debug_traps}, you set it to point to a
18751 function in your program, that function is called when
18752 @code{@value{GDBN}} continues after stopping on a trap (for example, bus
18753 error). The function indicated by @code{exceptionHook} is called with
18754 one parameter: an @code{int} which is the exception number.
18757 Compile and link together: your program, the @value{GDBN} debugging stub for
18758 your target architecture, and the supporting subroutines.
18761 Make sure you have a serial connection between your target machine and
18762 the @value{GDBN} host, and identify the serial port on the host.
18765 @c The "remote" target now provides a `load' command, so we should
18766 @c document that. FIXME.
18767 Download your program to your target machine (or get it there by
18768 whatever means the manufacturer provides), and start it.
18771 Start @value{GDBN} on the host, and connect to the target
18772 (@pxref{Connecting,,Connecting to a Remote Target}).
18776 @node Configurations
18777 @chapter Configuration-Specific Information
18779 While nearly all @value{GDBN} commands are available for all native and
18780 cross versions of the debugger, there are some exceptions. This chapter
18781 describes things that are only available in certain configurations.
18783 There are three major categories of configurations: native
18784 configurations, where the host and target are the same, embedded
18785 operating system configurations, which are usually the same for several
18786 different processor architectures, and bare embedded processors, which
18787 are quite different from each other.
18792 * Embedded Processors::
18799 This section describes details specific to particular native
18804 * BSD libkvm Interface:: Debugging BSD kernel memory images
18805 * SVR4 Process Information:: SVR4 process information
18806 * DJGPP Native:: Features specific to the DJGPP port
18807 * Cygwin Native:: Features specific to the Cygwin port
18808 * Hurd Native:: Features specific to @sc{gnu} Hurd
18809 * Darwin:: Features specific to Darwin
18815 On HP-UX systems, if you refer to a function or variable name that
18816 begins with a dollar sign, @value{GDBN} searches for a user or system
18817 name first, before it searches for a convenience variable.
18820 @node BSD libkvm Interface
18821 @subsection BSD libkvm Interface
18824 @cindex kernel memory image
18825 @cindex kernel crash dump
18827 BSD-derived systems (FreeBSD/NetBSD/OpenBSD) have a kernel memory
18828 interface that provides a uniform interface for accessing kernel virtual
18829 memory images, including live systems and crash dumps. @value{GDBN}
18830 uses this interface to allow you to debug live kernels and kernel crash
18831 dumps on many native BSD configurations. This is implemented as a
18832 special @code{kvm} debugging target. For debugging a live system, load
18833 the currently running kernel into @value{GDBN} and connect to the
18837 (@value{GDBP}) @b{target kvm}
18840 For debugging crash dumps, provide the file name of the crash dump as an
18844 (@value{GDBP}) @b{target kvm /var/crash/bsd.0}
18847 Once connected to the @code{kvm} target, the following commands are
18853 Set current context from the @dfn{Process Control Block} (PCB) address.
18856 Set current context from proc address. This command isn't available on
18857 modern FreeBSD systems.
18860 @node SVR4 Process Information
18861 @subsection SVR4 Process Information
18863 @cindex examine process image
18864 @cindex process info via @file{/proc}
18866 Many versions of SVR4 and compatible systems provide a facility called
18867 @samp{/proc} that can be used to examine the image of a running
18868 process using file-system subroutines.
18870 If @value{GDBN} is configured for an operating system with this
18871 facility, the command @code{info proc} is available to report
18872 information about the process running your program, or about any
18873 process running on your system. This includes, as of this writing,
18874 @sc{gnu}/Linux, OSF/1 (Digital Unix), Solaris, and Irix, but
18875 not HP-UX, for example.
18877 This command may also work on core files that were created on a system
18878 that has the @samp{/proc} facility.
18884 @itemx info proc @var{process-id}
18885 Summarize available information about any running process. If a
18886 process ID is specified by @var{process-id}, display information about
18887 that process; otherwise display information about the program being
18888 debugged. The summary includes the debugged process ID, the command
18889 line used to invoke it, its current working directory, and its
18890 executable file's absolute file name.
18892 On some systems, @var{process-id} can be of the form
18893 @samp{[@var{pid}]/@var{tid}} which specifies a certain thread ID
18894 within a process. If the optional @var{pid} part is missing, it means
18895 a thread from the process being debugged (the leading @samp{/} still
18896 needs to be present, or else @value{GDBN} will interpret the number as
18897 a process ID rather than a thread ID).
18899 @item info proc cmdline
18900 @cindex info proc cmdline
18901 Show the original command line of the process. This command is
18902 specific to @sc{gnu}/Linux.
18904 @item info proc cwd
18905 @cindex info proc cwd
18906 Show the current working directory of the process. This command is
18907 specific to @sc{gnu}/Linux.
18909 @item info proc exe
18910 @cindex info proc exe
18911 Show the name of executable of the process. This command is specific
18914 @item info proc mappings
18915 @cindex memory address space mappings
18916 Report the memory address space ranges accessible in the program, with
18917 information on whether the process has read, write, or execute access
18918 rights to each range. On @sc{gnu}/Linux systems, each memory range
18919 includes the object file which is mapped to that range, instead of the
18920 memory access rights to that range.
18922 @item info proc stat
18923 @itemx info proc status
18924 @cindex process detailed status information
18925 These subcommands are specific to @sc{gnu}/Linux systems. They show
18926 the process-related information, including the user ID and group ID;
18927 how many threads are there in the process; its virtual memory usage;
18928 the signals that are pending, blocked, and ignored; its TTY; its
18929 consumption of system and user time; its stack size; its @samp{nice}
18930 value; etc. For more information, see the @samp{proc} man page
18931 (type @kbd{man 5 proc} from your shell prompt).
18933 @item info proc all
18934 Show all the information about the process described under all of the
18935 above @code{info proc} subcommands.
18938 @comment These sub-options of 'info proc' were not included when
18939 @comment procfs.c was re-written. Keep their descriptions around
18940 @comment against the day when someone finds the time to put them back in.
18941 @kindex info proc times
18942 @item info proc times
18943 Starting time, user CPU time, and system CPU time for your program and
18946 @kindex info proc id
18948 Report on the process IDs related to your program: its own process ID,
18949 the ID of its parent, the process group ID, and the session ID.
18952 @item set procfs-trace
18953 @kindex set procfs-trace
18954 @cindex @code{procfs} API calls
18955 This command enables and disables tracing of @code{procfs} API calls.
18957 @item show procfs-trace
18958 @kindex show procfs-trace
18959 Show the current state of @code{procfs} API call tracing.
18961 @item set procfs-file @var{file}
18962 @kindex set procfs-file
18963 Tell @value{GDBN} to write @code{procfs} API trace to the named
18964 @var{file}. @value{GDBN} appends the trace info to the previous
18965 contents of the file. The default is to display the trace on the
18968 @item show procfs-file
18969 @kindex show procfs-file
18970 Show the file to which @code{procfs} API trace is written.
18972 @item proc-trace-entry
18973 @itemx proc-trace-exit
18974 @itemx proc-untrace-entry
18975 @itemx proc-untrace-exit
18976 @kindex proc-trace-entry
18977 @kindex proc-trace-exit
18978 @kindex proc-untrace-entry
18979 @kindex proc-untrace-exit
18980 These commands enable and disable tracing of entries into and exits
18981 from the @code{syscall} interface.
18984 @kindex info pidlist
18985 @cindex process list, QNX Neutrino
18986 For QNX Neutrino only, this command displays the list of all the
18987 processes and all the threads within each process.
18990 @kindex info meminfo
18991 @cindex mapinfo list, QNX Neutrino
18992 For QNX Neutrino only, this command displays the list of all mapinfos.
18996 @subsection Features for Debugging @sc{djgpp} Programs
18997 @cindex @sc{djgpp} debugging
18998 @cindex native @sc{djgpp} debugging
18999 @cindex MS-DOS-specific commands
19002 @sc{djgpp} is a port of the @sc{gnu} development tools to MS-DOS and
19003 MS-Windows. @sc{djgpp} programs are 32-bit protected-mode programs
19004 that use the @dfn{DPMI} (DOS Protected-Mode Interface) API to run on
19005 top of real-mode DOS systems and their emulations.
19007 @value{GDBN} supports native debugging of @sc{djgpp} programs, and
19008 defines a few commands specific to the @sc{djgpp} port. This
19009 subsection describes those commands.
19014 This is a prefix of @sc{djgpp}-specific commands which print
19015 information about the target system and important OS structures.
19018 @cindex MS-DOS system info
19019 @cindex free memory information (MS-DOS)
19020 @item info dos sysinfo
19021 This command displays assorted information about the underlying
19022 platform: the CPU type and features, the OS version and flavor, the
19023 DPMI version, and the available conventional and DPMI memory.
19028 @cindex segment descriptor tables
19029 @cindex descriptor tables display
19031 @itemx info dos ldt
19032 @itemx info dos idt
19033 These 3 commands display entries from, respectively, Global, Local,
19034 and Interrupt Descriptor Tables (GDT, LDT, and IDT). The descriptor
19035 tables are data structures which store a descriptor for each segment
19036 that is currently in use. The segment's selector is an index into a
19037 descriptor table; the table entry for that index holds the
19038 descriptor's base address and limit, and its attributes and access
19041 A typical @sc{djgpp} program uses 3 segments: a code segment, a data
19042 segment (used for both data and the stack), and a DOS segment (which
19043 allows access to DOS/BIOS data structures and absolute addresses in
19044 conventional memory). However, the DPMI host will usually define
19045 additional segments in order to support the DPMI environment.
19047 @cindex garbled pointers
19048 These commands allow to display entries from the descriptor tables.
19049 Without an argument, all entries from the specified table are
19050 displayed. An argument, which should be an integer expression, means
19051 display a single entry whose index is given by the argument. For
19052 example, here's a convenient way to display information about the
19053 debugged program's data segment:
19056 @exdent @code{(@value{GDBP}) info dos ldt $ds}
19057 @exdent @code{0x13f: base=0x11970000 limit=0x0009ffff 32-Bit Data (Read/Write, Exp-up)}
19061 This comes in handy when you want to see whether a pointer is outside
19062 the data segment's limit (i.e.@: @dfn{garbled}).
19064 @cindex page tables display (MS-DOS)
19066 @itemx info dos pte
19067 These two commands display entries from, respectively, the Page
19068 Directory and the Page Tables. Page Directories and Page Tables are
19069 data structures which control how virtual memory addresses are mapped
19070 into physical addresses. A Page Table includes an entry for every
19071 page of memory that is mapped into the program's address space; there
19072 may be several Page Tables, each one holding up to 4096 entries. A
19073 Page Directory has up to 4096 entries, one each for every Page Table
19074 that is currently in use.
19076 Without an argument, @kbd{info dos pde} displays the entire Page
19077 Directory, and @kbd{info dos pte} displays all the entries in all of
19078 the Page Tables. An argument, an integer expression, given to the
19079 @kbd{info dos pde} command means display only that entry from the Page
19080 Directory table. An argument given to the @kbd{info dos pte} command
19081 means display entries from a single Page Table, the one pointed to by
19082 the specified entry in the Page Directory.
19084 @cindex direct memory access (DMA) on MS-DOS
19085 These commands are useful when your program uses @dfn{DMA} (Direct
19086 Memory Access), which needs physical addresses to program the DMA
19089 These commands are supported only with some DPMI servers.
19091 @cindex physical address from linear address
19092 @item info dos address-pte @var{addr}
19093 This command displays the Page Table entry for a specified linear
19094 address. The argument @var{addr} is a linear address which should
19095 already have the appropriate segment's base address added to it,
19096 because this command accepts addresses which may belong to @emph{any}
19097 segment. For example, here's how to display the Page Table entry for
19098 the page where a variable @code{i} is stored:
19101 @exdent @code{(@value{GDBP}) info dos address-pte __djgpp_base_address + (char *)&i}
19102 @exdent @code{Page Table entry for address 0x11a00d30:}
19103 @exdent @code{Base=0x02698000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0xd30}
19107 This says that @code{i} is stored at offset @code{0xd30} from the page
19108 whose physical base address is @code{0x02698000}, and shows all the
19109 attributes of that page.
19111 Note that you must cast the addresses of variables to a @code{char *},
19112 since otherwise the value of @code{__djgpp_base_address}, the base
19113 address of all variables and functions in a @sc{djgpp} program, will
19114 be added using the rules of C pointer arithmetics: if @code{i} is
19115 declared an @code{int}, @value{GDBN} will add 4 times the value of
19116 @code{__djgpp_base_address} to the address of @code{i}.
19118 Here's another example, it displays the Page Table entry for the
19122 @exdent @code{(@value{GDBP}) info dos address-pte *((unsigned *)&_go32_info_block + 3)}
19123 @exdent @code{Page Table entry for address 0x29110:}
19124 @exdent @code{Base=0x00029000 Dirty Acc. Not-Cached Write-Back Usr Read-Write +0x110}
19128 (The @code{+ 3} offset is because the transfer buffer's address is the
19129 3rd member of the @code{_go32_info_block} structure.) The output
19130 clearly shows that this DPMI server maps the addresses in conventional
19131 memory 1:1, i.e.@: the physical (@code{0x00029000} + @code{0x110}) and
19132 linear (@code{0x29110}) addresses are identical.
19134 This command is supported only with some DPMI servers.
19137 @cindex DOS serial data link, remote debugging
19138 In addition to native debugging, the DJGPP port supports remote
19139 debugging via a serial data link. The following commands are specific
19140 to remote serial debugging in the DJGPP port of @value{GDBN}.
19143 @kindex set com1base
19144 @kindex set com1irq
19145 @kindex set com2base
19146 @kindex set com2irq
19147 @kindex set com3base
19148 @kindex set com3irq
19149 @kindex set com4base
19150 @kindex set com4irq
19151 @item set com1base @var{addr}
19152 This command sets the base I/O port address of the @file{COM1} serial
19155 @item set com1irq @var{irq}
19156 This command sets the @dfn{Interrupt Request} (@code{IRQ}) line to use
19157 for the @file{COM1} serial port.
19159 There are similar commands @samp{set com2base}, @samp{set com3irq},
19160 etc.@: for setting the port address and the @code{IRQ} lines for the
19163 @kindex show com1base
19164 @kindex show com1irq
19165 @kindex show com2base
19166 @kindex show com2irq
19167 @kindex show com3base
19168 @kindex show com3irq
19169 @kindex show com4base
19170 @kindex show com4irq
19171 The related commands @samp{show com1base}, @samp{show com1irq} etc.@:
19172 display the current settings of the base address and the @code{IRQ}
19173 lines used by the COM ports.
19176 @kindex info serial
19177 @cindex DOS serial port status
19178 This command prints the status of the 4 DOS serial ports. For each
19179 port, it prints whether it's active or not, its I/O base address and
19180 IRQ number, whether it uses a 16550-style FIFO, its baudrate, and the
19181 counts of various errors encountered so far.
19185 @node Cygwin Native
19186 @subsection Features for Debugging MS Windows PE Executables
19187 @cindex MS Windows debugging
19188 @cindex native Cygwin debugging
19189 @cindex Cygwin-specific commands
19191 @value{GDBN} supports native debugging of MS Windows programs, including
19192 DLLs with and without symbolic debugging information.
19194 @cindex Ctrl-BREAK, MS-Windows
19195 @cindex interrupt debuggee on MS-Windows
19196 MS-Windows programs that call @code{SetConsoleMode} to switch off the
19197 special meaning of the @samp{Ctrl-C} keystroke cannot be interrupted
19198 by typing @kbd{C-c}. For this reason, @value{GDBN} on MS-Windows
19199 supports @kbd{C-@key{BREAK}} as an alternative interrupt key
19200 sequence, which can be used to interrupt the debuggee even if it
19203 There are various additional Cygwin-specific commands, described in
19204 this section. Working with DLLs that have no debugging symbols is
19205 described in @ref{Non-debug DLL Symbols}.
19210 This is a prefix of MS Windows-specific commands which print
19211 information about the target system and important OS structures.
19213 @item info w32 selector
19214 This command displays information returned by
19215 the Win32 API @code{GetThreadSelectorEntry} function.
19216 It takes an optional argument that is evaluated to
19217 a long value to give the information about this given selector.
19218 Without argument, this command displays information
19219 about the six segment registers.
19221 @item info w32 thread-information-block
19222 This command displays thread specific information stored in the
19223 Thread Information Block (readable on the X86 CPU family using @code{$fs}
19224 selector for 32-bit programs and @code{$gs} for 64-bit programs).
19228 This is a Cygwin-specific alias of @code{info shared}.
19230 @kindex dll-symbols
19232 This command loads symbols from a dll similarly to
19233 add-sym command but without the need to specify a base address.
19235 @kindex set cygwin-exceptions
19236 @cindex debugging the Cygwin DLL
19237 @cindex Cygwin DLL, debugging
19238 @item set cygwin-exceptions @var{mode}
19239 If @var{mode} is @code{on}, @value{GDBN} will break on exceptions that
19240 happen inside the Cygwin DLL. If @var{mode} is @code{off},
19241 @value{GDBN} will delay recognition of exceptions, and may ignore some
19242 exceptions which seem to be caused by internal Cygwin DLL
19243 ``bookkeeping''. This option is meant primarily for debugging the
19244 Cygwin DLL itself; the default value is @code{off} to avoid annoying
19245 @value{GDBN} users with false @code{SIGSEGV} signals.
19247 @kindex show cygwin-exceptions
19248 @item show cygwin-exceptions
19249 Displays whether @value{GDBN} will break on exceptions that happen
19250 inside the Cygwin DLL itself.
19252 @kindex set new-console
19253 @item set new-console @var{mode}
19254 If @var{mode} is @code{on} the debuggee will
19255 be started in a new console on next start.
19256 If @var{mode} is @code{off}, the debuggee will
19257 be started in the same console as the debugger.
19259 @kindex show new-console
19260 @item show new-console
19261 Displays whether a new console is used
19262 when the debuggee is started.
19264 @kindex set new-group
19265 @item set new-group @var{mode}
19266 This boolean value controls whether the debuggee should
19267 start a new group or stay in the same group as the debugger.
19268 This affects the way the Windows OS handles
19271 @kindex show new-group
19272 @item show new-group
19273 Displays current value of new-group boolean.
19275 @kindex set debugevents
19276 @item set debugevents
19277 This boolean value adds debug output concerning kernel events related
19278 to the debuggee seen by the debugger. This includes events that
19279 signal thread and process creation and exit, DLL loading and
19280 unloading, console interrupts, and debugging messages produced by the
19281 Windows @code{OutputDebugString} API call.
19283 @kindex set debugexec
19284 @item set debugexec
19285 This boolean value adds debug output concerning execute events
19286 (such as resume thread) seen by the debugger.
19288 @kindex set debugexceptions
19289 @item set debugexceptions
19290 This boolean value adds debug output concerning exceptions in the
19291 debuggee seen by the debugger.
19293 @kindex set debugmemory
19294 @item set debugmemory
19295 This boolean value adds debug output concerning debuggee memory reads
19296 and writes by the debugger.
19300 This boolean values specifies whether the debuggee is called
19301 via a shell or directly (default value is on).
19305 Displays if the debuggee will be started with a shell.
19310 * Non-debug DLL Symbols:: Support for DLLs without debugging symbols
19313 @node Non-debug DLL Symbols
19314 @subsubsection Support for DLLs without Debugging Symbols
19315 @cindex DLLs with no debugging symbols
19316 @cindex Minimal symbols and DLLs
19318 Very often on windows, some of the DLLs that your program relies on do
19319 not include symbolic debugging information (for example,
19320 @file{kernel32.dll}). When @value{GDBN} doesn't recognize any debugging
19321 symbols in a DLL, it relies on the minimal amount of symbolic
19322 information contained in the DLL's export table. This section
19323 describes working with such symbols, known internally to @value{GDBN} as
19324 ``minimal symbols''.
19326 Note that before the debugged program has started execution, no DLLs
19327 will have been loaded. The easiest way around this problem is simply to
19328 start the program --- either by setting a breakpoint or letting the
19329 program run once to completion. It is also possible to force
19330 @value{GDBN} to load a particular DLL before starting the executable ---
19331 see the shared library information in @ref{Files}, or the
19332 @code{dll-symbols} command in @ref{Cygwin Native}. Currently,
19333 explicitly loading symbols from a DLL with no debugging information will
19334 cause the symbol names to be duplicated in @value{GDBN}'s lookup table,
19335 which may adversely affect symbol lookup performance.
19337 @subsubsection DLL Name Prefixes
19339 In keeping with the naming conventions used by the Microsoft debugging
19340 tools, DLL export symbols are made available with a prefix based on the
19341 DLL name, for instance @code{KERNEL32!CreateFileA}. The plain name is
19342 also entered into the symbol table, so @code{CreateFileA} is often
19343 sufficient. In some cases there will be name clashes within a program
19344 (particularly if the executable itself includes full debugging symbols)
19345 necessitating the use of the fully qualified name when referring to the
19346 contents of the DLL. Use single-quotes around the name to avoid the
19347 exclamation mark (``!'') being interpreted as a language operator.
19349 Note that the internal name of the DLL may be all upper-case, even
19350 though the file name of the DLL is lower-case, or vice-versa. Since
19351 symbols within @value{GDBN} are @emph{case-sensitive} this may cause
19352 some confusion. If in doubt, try the @code{info functions} and
19353 @code{info variables} commands or even @code{maint print msymbols}
19354 (@pxref{Symbols}). Here's an example:
19357 (@value{GDBP}) info function CreateFileA
19358 All functions matching regular expression "CreateFileA":
19360 Non-debugging symbols:
19361 0x77e885f4 CreateFileA
19362 0x77e885f4 KERNEL32!CreateFileA
19366 (@value{GDBP}) info function !
19367 All functions matching regular expression "!":
19369 Non-debugging symbols:
19370 0x6100114c cygwin1!__assert
19371 0x61004034 cygwin1!_dll_crt0@@0
19372 0x61004240 cygwin1!dll_crt0(per_process *)
19376 @subsubsection Working with Minimal Symbols
19378 Symbols extracted from a DLL's export table do not contain very much
19379 type information. All that @value{GDBN} can do is guess whether a symbol
19380 refers to a function or variable depending on the linker section that
19381 contains the symbol. Also note that the actual contents of the memory
19382 contained in a DLL are not available unless the program is running. This
19383 means that you cannot examine the contents of a variable or disassemble
19384 a function within a DLL without a running program.
19386 Variables are generally treated as pointers and dereferenced
19387 automatically. For this reason, it is often necessary to prefix a
19388 variable name with the address-of operator (``&'') and provide explicit
19389 type information in the command. Here's an example of the type of
19393 (@value{GDBP}) print 'cygwin1!__argv'
19398 (@value{GDBP}) x 'cygwin1!__argv'
19399 0x10021610: "\230y\""
19402 And two possible solutions:
19405 (@value{GDBP}) print ((char **)'cygwin1!__argv')[0]
19406 $2 = 0x22fd98 "/cygdrive/c/mydirectory/myprogram"
19410 (@value{GDBP}) x/2x &'cygwin1!__argv'
19411 0x610c0aa8 <cygwin1!__argv>: 0x10021608 0x00000000
19412 (@value{GDBP}) x/x 0x10021608
19413 0x10021608: 0x0022fd98
19414 (@value{GDBP}) x/s 0x0022fd98
19415 0x22fd98: "/cygdrive/c/mydirectory/myprogram"
19418 Setting a break point within a DLL is possible even before the program
19419 starts execution. However, under these circumstances, @value{GDBN} can't
19420 examine the initial instructions of the function in order to skip the
19421 function's frame set-up code. You can work around this by using ``*&''
19422 to set the breakpoint at a raw memory address:
19425 (@value{GDBP}) break *&'python22!PyOS_Readline'
19426 Breakpoint 1 at 0x1e04eff0
19429 The author of these extensions is not entirely convinced that setting a
19430 break point within a shared DLL like @file{kernel32.dll} is completely
19434 @subsection Commands Specific to @sc{gnu} Hurd Systems
19435 @cindex @sc{gnu} Hurd debugging
19437 This subsection describes @value{GDBN} commands specific to the
19438 @sc{gnu} Hurd native debugging.
19443 @kindex set signals@r{, Hurd command}
19444 @kindex set sigs@r{, Hurd command}
19445 This command toggles the state of inferior signal interception by
19446 @value{GDBN}. Mach exceptions, such as breakpoint traps, are not
19447 affected by this command. @code{sigs} is a shorthand alias for
19452 @kindex show signals@r{, Hurd command}
19453 @kindex show sigs@r{, Hurd command}
19454 Show the current state of intercepting inferior's signals.
19456 @item set signal-thread
19457 @itemx set sigthread
19458 @kindex set signal-thread
19459 @kindex set sigthread
19460 This command tells @value{GDBN} which thread is the @code{libc} signal
19461 thread. That thread is run when a signal is delivered to a running
19462 process. @code{set sigthread} is the shorthand alias of @code{set
19465 @item show signal-thread
19466 @itemx show sigthread
19467 @kindex show signal-thread
19468 @kindex show sigthread
19469 These two commands show which thread will run when the inferior is
19470 delivered a signal.
19473 @kindex set stopped@r{, Hurd command}
19474 This commands tells @value{GDBN} that the inferior process is stopped,
19475 as with the @code{SIGSTOP} signal. The stopped process can be
19476 continued by delivering a signal to it.
19479 @kindex show stopped@r{, Hurd command}
19480 This command shows whether @value{GDBN} thinks the debuggee is
19483 @item set exceptions
19484 @kindex set exceptions@r{, Hurd command}
19485 Use this command to turn off trapping of exceptions in the inferior.
19486 When exception trapping is off, neither breakpoints nor
19487 single-stepping will work. To restore the default, set exception
19490 @item show exceptions
19491 @kindex show exceptions@r{, Hurd command}
19492 Show the current state of trapping exceptions in the inferior.
19494 @item set task pause
19495 @kindex set task@r{, Hurd commands}
19496 @cindex task attributes (@sc{gnu} Hurd)
19497 @cindex pause current task (@sc{gnu} Hurd)
19498 This command toggles task suspension when @value{GDBN} has control.
19499 Setting it to on takes effect immediately, and the task is suspended
19500 whenever @value{GDBN} gets control. Setting it to off will take
19501 effect the next time the inferior is continued. If this option is set
19502 to off, you can use @code{set thread default pause on} or @code{set
19503 thread pause on} (see below) to pause individual threads.
19505 @item show task pause
19506 @kindex show task@r{, Hurd commands}
19507 Show the current state of task suspension.
19509 @item set task detach-suspend-count
19510 @cindex task suspend count
19511 @cindex detach from task, @sc{gnu} Hurd
19512 This command sets the suspend count the task will be left with when
19513 @value{GDBN} detaches from it.
19515 @item show task detach-suspend-count
19516 Show the suspend count the task will be left with when detaching.
19518 @item set task exception-port
19519 @itemx set task excp
19520 @cindex task exception port, @sc{gnu} Hurd
19521 This command sets the task exception port to which @value{GDBN} will
19522 forward exceptions. The argument should be the value of the @dfn{send
19523 rights} of the task. @code{set task excp} is a shorthand alias.
19525 @item set noninvasive
19526 @cindex noninvasive task options
19527 This command switches @value{GDBN} to a mode that is the least
19528 invasive as far as interfering with the inferior is concerned. This
19529 is the same as using @code{set task pause}, @code{set exceptions}, and
19530 @code{set signals} to values opposite to the defaults.
19532 @item info send-rights
19533 @itemx info receive-rights
19534 @itemx info port-rights
19535 @itemx info port-sets
19536 @itemx info dead-names
19539 @cindex send rights, @sc{gnu} Hurd
19540 @cindex receive rights, @sc{gnu} Hurd
19541 @cindex port rights, @sc{gnu} Hurd
19542 @cindex port sets, @sc{gnu} Hurd
19543 @cindex dead names, @sc{gnu} Hurd
19544 These commands display information about, respectively, send rights,
19545 receive rights, port rights, port sets, and dead names of a task.
19546 There are also shorthand aliases: @code{info ports} for @code{info
19547 port-rights} and @code{info psets} for @code{info port-sets}.
19549 @item set thread pause
19550 @kindex set thread@r{, Hurd command}
19551 @cindex thread properties, @sc{gnu} Hurd
19552 @cindex pause current thread (@sc{gnu} Hurd)
19553 This command toggles current thread suspension when @value{GDBN} has
19554 control. Setting it to on takes effect immediately, and the current
19555 thread is suspended whenever @value{GDBN} gets control. Setting it to
19556 off will take effect the next time the inferior is continued.
19557 Normally, this command has no effect, since when @value{GDBN} has
19558 control, the whole task is suspended. However, if you used @code{set
19559 task pause off} (see above), this command comes in handy to suspend
19560 only the current thread.
19562 @item show thread pause
19563 @kindex show thread@r{, Hurd command}
19564 This command shows the state of current thread suspension.
19566 @item set thread run
19567 This command sets whether the current thread is allowed to run.
19569 @item show thread run
19570 Show whether the current thread is allowed to run.
19572 @item set thread detach-suspend-count
19573 @cindex thread suspend count, @sc{gnu} Hurd
19574 @cindex detach from thread, @sc{gnu} Hurd
19575 This command sets the suspend count @value{GDBN} will leave on a
19576 thread when detaching. This number is relative to the suspend count
19577 found by @value{GDBN} when it notices the thread; use @code{set thread
19578 takeover-suspend-count} to force it to an absolute value.
19580 @item show thread detach-suspend-count
19581 Show the suspend count @value{GDBN} will leave on the thread when
19584 @item set thread exception-port
19585 @itemx set thread excp
19586 Set the thread exception port to which to forward exceptions. This
19587 overrides the port set by @code{set task exception-port} (see above).
19588 @code{set thread excp} is the shorthand alias.
19590 @item set thread takeover-suspend-count
19591 Normally, @value{GDBN}'s thread suspend counts are relative to the
19592 value @value{GDBN} finds when it notices each thread. This command
19593 changes the suspend counts to be absolute instead.
19595 @item set thread default
19596 @itemx show thread default
19597 @cindex thread default settings, @sc{gnu} Hurd
19598 Each of the above @code{set thread} commands has a @code{set thread
19599 default} counterpart (e.g., @code{set thread default pause}, @code{set
19600 thread default exception-port}, etc.). The @code{thread default}
19601 variety of commands sets the default thread properties for all
19602 threads; you can then change the properties of individual threads with
19603 the non-default commands.
19610 @value{GDBN} provides the following commands specific to the Darwin target:
19613 @item set debug darwin @var{num}
19614 @kindex set debug darwin
19615 When set to a non zero value, enables debugging messages specific to
19616 the Darwin support. Higher values produce more verbose output.
19618 @item show debug darwin
19619 @kindex show debug darwin
19620 Show the current state of Darwin messages.
19622 @item set debug mach-o @var{num}
19623 @kindex set debug mach-o
19624 When set to a non zero value, enables debugging messages while
19625 @value{GDBN} is reading Darwin object files. (@dfn{Mach-O} is the
19626 file format used on Darwin for object and executable files.) Higher
19627 values produce more verbose output. This is a command to diagnose
19628 problems internal to @value{GDBN} and should not be needed in normal
19631 @item show debug mach-o
19632 @kindex show debug mach-o
19633 Show the current state of Mach-O file messages.
19635 @item set mach-exceptions on
19636 @itemx set mach-exceptions off
19637 @kindex set mach-exceptions
19638 On Darwin, faults are first reported as a Mach exception and are then
19639 mapped to a Posix signal. Use this command to turn on trapping of
19640 Mach exceptions in the inferior. This might be sometimes useful to
19641 better understand the cause of a fault. The default is off.
19643 @item show mach-exceptions
19644 @kindex show mach-exceptions
19645 Show the current state of exceptions trapping.
19650 @section Embedded Operating Systems
19652 This section describes configurations involving the debugging of
19653 embedded operating systems that are available for several different
19657 * VxWorks:: Using @value{GDBN} with VxWorks
19660 @value{GDBN} includes the ability to debug programs running on
19661 various real-time operating systems.
19664 @subsection Using @value{GDBN} with VxWorks
19670 @kindex target vxworks
19671 @item target vxworks @var{machinename}
19672 A VxWorks system, attached via TCP/IP. The argument @var{machinename}
19673 is the target system's machine name or IP address.
19677 On VxWorks, @code{load} links @var{filename} dynamically on the
19678 current target system as well as adding its symbols in @value{GDBN}.
19680 @value{GDBN} enables developers to spawn and debug tasks running on networked
19681 VxWorks targets from a Unix host. Already-running tasks spawned from
19682 the VxWorks shell can also be debugged. @value{GDBN} uses code that runs on
19683 both the Unix host and on the VxWorks target. The program
19684 @code{@value{GDBP}} is installed and executed on the Unix host. (It may be
19685 installed with the name @code{vxgdb}, to distinguish it from a
19686 @value{GDBN} for debugging programs on the host itself.)
19689 @item VxWorks-timeout @var{args}
19690 @kindex vxworks-timeout
19691 All VxWorks-based targets now support the option @code{vxworks-timeout}.
19692 This option is set by the user, and @var{args} represents the number of
19693 seconds @value{GDBN} waits for responses to rpc's. You might use this if
19694 your VxWorks target is a slow software simulator or is on the far side
19695 of a thin network line.
19698 The following information on connecting to VxWorks was current when
19699 this manual was produced; newer releases of VxWorks may use revised
19702 @findex INCLUDE_RDB
19703 To use @value{GDBN} with VxWorks, you must rebuild your VxWorks kernel
19704 to include the remote debugging interface routines in the VxWorks
19705 library @file{rdb.a}. To do this, define @code{INCLUDE_RDB} in the
19706 VxWorks configuration file @file{configAll.h} and rebuild your VxWorks
19707 kernel. The resulting kernel contains @file{rdb.a}, and spawns the
19708 source debugging task @code{tRdbTask} when VxWorks is booted. For more
19709 information on configuring and remaking VxWorks, see the manufacturer's
19711 @c VxWorks, see the @cite{VxWorks Programmer's Guide}.
19713 Once you have included @file{rdb.a} in your VxWorks system image and set
19714 your Unix execution search path to find @value{GDBN}, you are ready to
19715 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}} (or
19716 @code{vxgdb}, depending on your installation).
19718 @value{GDBN} comes up showing the prompt:
19725 * VxWorks Connection:: Connecting to VxWorks
19726 * VxWorks Download:: VxWorks download
19727 * VxWorks Attach:: Running tasks
19730 @node VxWorks Connection
19731 @subsubsection Connecting to VxWorks
19733 The @value{GDBN} command @code{target} lets you connect to a VxWorks target on the
19734 network. To connect to a target whose host name is ``@code{tt}'', type:
19737 (vxgdb) target vxworks tt
19741 @value{GDBN} displays messages like these:
19744 Attaching remote machine across net...
19749 @value{GDBN} then attempts to read the symbol tables of any object modules
19750 loaded into the VxWorks target since it was last booted. @value{GDBN} locates
19751 these files by searching the directories listed in the command search
19752 path (@pxref{Environment, ,Your Program's Environment}); if it fails
19753 to find an object file, it displays a message such as:
19756 prog.o: No such file or directory.
19759 When this happens, add the appropriate directory to the search path with
19760 the @value{GDBN} command @code{path}, and execute the @code{target}
19763 @node VxWorks Download
19764 @subsubsection VxWorks Download
19766 @cindex download to VxWorks
19767 If you have connected to the VxWorks target and you want to debug an
19768 object that has not yet been loaded, you can use the @value{GDBN}
19769 @code{load} command to download a file from Unix to VxWorks
19770 incrementally. The object file given as an argument to the @code{load}
19771 command is actually opened twice: first by the VxWorks target in order
19772 to download the code, then by @value{GDBN} in order to read the symbol
19773 table. This can lead to problems if the current working directories on
19774 the two systems differ. If both systems have NFS mounted the same
19775 filesystems, you can avoid these problems by using absolute paths.
19776 Otherwise, it is simplest to set the working directory on both systems
19777 to the directory in which the object file resides, and then to reference
19778 the file by its name, without any path. For instance, a program
19779 @file{prog.o} may reside in @file{@var{vxpath}/vw/demo/rdb} in VxWorks
19780 and in @file{@var{hostpath}/vw/demo/rdb} on the host. To load this
19781 program, type this on VxWorks:
19784 -> cd "@var{vxpath}/vw/demo/rdb"
19788 Then, in @value{GDBN}, type:
19791 (vxgdb) cd @var{hostpath}/vw/demo/rdb
19792 (vxgdb) load prog.o
19795 @value{GDBN} displays a response similar to this:
19798 Reading symbol data from wherever/vw/demo/rdb/prog.o... done.
19801 You can also use the @code{load} command to reload an object module
19802 after editing and recompiling the corresponding source file. Note that
19803 this makes @value{GDBN} delete all currently-defined breakpoints,
19804 auto-displays, and convenience variables, and to clear the value
19805 history. (This is necessary in order to preserve the integrity of
19806 debugger's data structures that reference the target system's symbol
19809 @node VxWorks Attach
19810 @subsubsection Running Tasks
19812 @cindex running VxWorks tasks
19813 You can also attach to an existing task using the @code{attach} command as
19817 (vxgdb) attach @var{task}
19821 where @var{task} is the VxWorks hexadecimal task ID. The task can be running
19822 or suspended when you attach to it. Running tasks are suspended at
19823 the time of attachment.
19825 @node Embedded Processors
19826 @section Embedded Processors
19828 This section goes into details specific to particular embedded
19831 @cindex send command to simulator
19832 Whenever a specific embedded processor has a simulator, @value{GDBN}
19833 allows to send an arbitrary command to the simulator.
19836 @item sim @var{command}
19837 @kindex sim@r{, a command}
19838 Send an arbitrary @var{command} string to the simulator. Consult the
19839 documentation for the specific simulator in use for information about
19840 acceptable commands.
19846 * M32R/D:: Renesas M32R/D
19847 * M68K:: Motorola M68K
19848 * MicroBlaze:: Xilinx MicroBlaze
19849 * MIPS Embedded:: MIPS Embedded
19850 * OpenRISC 1000:: OpenRisc 1000
19851 * PowerPC Embedded:: PowerPC Embedded
19852 * PA:: HP PA Embedded
19853 * Sparclet:: Tsqware Sparclet
19854 * Sparclite:: Fujitsu Sparclite
19855 * Z8000:: Zilog Z8000
19858 * Super-H:: Renesas Super-H
19867 @item target rdi @var{dev}
19868 ARM Angel monitor, via RDI library interface to ADP protocol. You may
19869 use this target to communicate with both boards running the Angel
19870 monitor, or with the EmbeddedICE JTAG debug device.
19873 @item target rdp @var{dev}
19878 @value{GDBN} provides the following ARM-specific commands:
19881 @item set arm disassembler
19883 This commands selects from a list of disassembly styles. The
19884 @code{"std"} style is the standard style.
19886 @item show arm disassembler
19888 Show the current disassembly style.
19890 @item set arm apcs32
19891 @cindex ARM 32-bit mode
19892 This command toggles ARM operation mode between 32-bit and 26-bit.
19894 @item show arm apcs32
19895 Display the current usage of the ARM 32-bit mode.
19897 @item set arm fpu @var{fputype}
19898 This command sets the ARM floating-point unit (FPU) type. The
19899 argument @var{fputype} can be one of these:
19903 Determine the FPU type by querying the OS ABI.
19905 Software FPU, with mixed-endian doubles on little-endian ARM
19908 GCC-compiled FPA co-processor.
19910 Software FPU with pure-endian doubles.
19916 Show the current type of the FPU.
19919 This command forces @value{GDBN} to use the specified ABI.
19922 Show the currently used ABI.
19924 @item set arm fallback-mode (arm|thumb|auto)
19925 @value{GDBN} uses the symbol table, when available, to determine
19926 whether instructions are ARM or Thumb. This command controls
19927 @value{GDBN}'s default behavior when the symbol table is not
19928 available. The default is @samp{auto}, which causes @value{GDBN} to
19929 use the current execution mode (from the @code{T} bit in the @code{CPSR}
19932 @item show arm fallback-mode
19933 Show the current fallback instruction mode.
19935 @item set arm force-mode (arm|thumb|auto)
19936 This command overrides use of the symbol table to determine whether
19937 instructions are ARM or Thumb. The default is @samp{auto}, which
19938 causes @value{GDBN} to use the symbol table and then the setting
19939 of @samp{set arm fallback-mode}.
19941 @item show arm force-mode
19942 Show the current forced instruction mode.
19944 @item set debug arm
19945 Toggle whether to display ARM-specific debugging messages from the ARM
19946 target support subsystem.
19948 @item show debug arm
19949 Show whether ARM-specific debugging messages are enabled.
19952 The following commands are available when an ARM target is debugged
19953 using the RDI interface:
19956 @item rdilogfile @r{[}@var{file}@r{]}
19958 @cindex ADP (Angel Debugger Protocol) logging
19959 Set the filename for the ADP (Angel Debugger Protocol) packet log.
19960 With an argument, sets the log file to the specified @var{file}. With
19961 no argument, show the current log file name. The default log file is
19964 @item rdilogenable @r{[}@var{arg}@r{]}
19965 @kindex rdilogenable
19966 Control logging of ADP packets. With an argument of 1 or @code{"yes"}
19967 enables logging, with an argument 0 or @code{"no"} disables it. With
19968 no arguments displays the current setting. When logging is enabled,
19969 ADP packets exchanged between @value{GDBN} and the RDI target device
19970 are logged to a file.
19972 @item set rdiromatzero
19973 @kindex set rdiromatzero
19974 @cindex ROM at zero address, RDI
19975 Tell @value{GDBN} whether the target has ROM at address 0. If on,
19976 vector catching is disabled, so that zero address can be used. If off
19977 (the default), vector catching is enabled. For this command to take
19978 effect, it needs to be invoked prior to the @code{target rdi} command.
19980 @item show rdiromatzero
19981 @kindex show rdiromatzero
19982 Show the current setting of ROM at zero address.
19984 @item set rdiheartbeat
19985 @kindex set rdiheartbeat
19986 @cindex RDI heartbeat
19987 Enable or disable RDI heartbeat packets. It is not recommended to
19988 turn on this option, since it confuses ARM and EPI JTAG interface, as
19989 well as the Angel monitor.
19991 @item show rdiheartbeat
19992 @kindex show rdiheartbeat
19993 Show the setting of RDI heartbeat packets.
19997 @item target sim @r{[}@var{simargs}@r{]} @dots{}
19998 The @value{GDBN} ARM simulator accepts the following optional arguments.
20001 @item --swi-support=@var{type}
20002 Tell the simulator which SWI interfaces to support.
20003 @var{type} may be a comma separated list of the following values.
20004 The default value is @code{all}.
20017 @subsection Renesas M32R/D and M32R/SDI
20020 @kindex target m32r
20021 @item target m32r @var{dev}
20022 Renesas M32R/D ROM monitor.
20024 @kindex target m32rsdi
20025 @item target m32rsdi @var{dev}
20026 Renesas M32R SDI server, connected via parallel port to the board.
20029 The following @value{GDBN} commands are specific to the M32R monitor:
20032 @item set download-path @var{path}
20033 @kindex set download-path
20034 @cindex find downloadable @sc{srec} files (M32R)
20035 Set the default path for finding downloadable @sc{srec} files.
20037 @item show download-path
20038 @kindex show download-path
20039 Show the default path for downloadable @sc{srec} files.
20041 @item set board-address @var{addr}
20042 @kindex set board-address
20043 @cindex M32-EVA target board address
20044 Set the IP address for the M32R-EVA target board.
20046 @item show board-address
20047 @kindex show board-address
20048 Show the current IP address of the target board.
20050 @item set server-address @var{addr}
20051 @kindex set server-address
20052 @cindex download server address (M32R)
20053 Set the IP address for the download server, which is the @value{GDBN}'s
20056 @item show server-address
20057 @kindex show server-address
20058 Display the IP address of the download server.
20060 @item upload @r{[}@var{file}@r{]}
20061 @kindex upload@r{, M32R}
20062 Upload the specified @sc{srec} @var{file} via the monitor's Ethernet
20063 upload capability. If no @var{file} argument is given, the current
20064 executable file is uploaded.
20066 @item tload @r{[}@var{file}@r{]}
20067 @kindex tload@r{, M32R}
20068 Test the @code{upload} command.
20071 The following commands are available for M32R/SDI:
20076 @cindex reset SDI connection, M32R
20077 This command resets the SDI connection.
20081 This command shows the SDI connection status.
20084 @kindex debug_chaos
20085 @cindex M32R/Chaos debugging
20086 Instructs the remote that M32R/Chaos debugging is to be used.
20088 @item use_debug_dma
20089 @kindex use_debug_dma
20090 Instructs the remote to use the DEBUG_DMA method of accessing memory.
20093 @kindex use_mon_code
20094 Instructs the remote to use the MON_CODE method of accessing memory.
20097 @kindex use_ib_break
20098 Instructs the remote to set breakpoints by IB break.
20100 @item use_dbt_break
20101 @kindex use_dbt_break
20102 Instructs the remote to set breakpoints by DBT.
20108 The Motorola m68k configuration includes ColdFire support, and a
20109 target command for the following ROM monitor.
20113 @kindex target dbug
20114 @item target dbug @var{dev}
20115 dBUG ROM monitor for Motorola ColdFire.
20120 @subsection MicroBlaze
20121 @cindex Xilinx MicroBlaze
20122 @cindex XMD, Xilinx Microprocessor Debugger
20124 The MicroBlaze is a soft-core processor supported on various Xilinx
20125 FPGAs, such as Spartan or Virtex series. Boards with these processors
20126 usually have JTAG ports which connect to a host system running the Xilinx
20127 Embedded Development Kit (EDK) or Software Development Kit (SDK).
20128 This host system is used to download the configuration bitstream to
20129 the target FPGA. The Xilinx Microprocessor Debugger (XMD) program
20130 communicates with the target board using the JTAG interface and
20131 presents a @code{gdbserver} interface to the board. By default
20132 @code{xmd} uses port @code{1234}. (While it is possible to change
20133 this default port, it requires the use of undocumented @code{xmd}
20134 commands. Contact Xilinx support if you need to do this.)
20136 Use these GDB commands to connect to the MicroBlaze target processor.
20139 @item target remote :1234
20140 Use this command to connect to the target if you are running @value{GDBN}
20141 on the same system as @code{xmd}.
20143 @item target remote @var{xmd-host}:1234
20144 Use this command to connect to the target if it is connected to @code{xmd}
20145 running on a different system named @var{xmd-host}.
20148 Use this command to download a program to the MicroBlaze target.
20150 @item set debug microblaze @var{n}
20151 Enable MicroBlaze-specific debugging messages if non-zero.
20153 @item show debug microblaze @var{n}
20154 Show MicroBlaze-specific debugging level.
20157 @node MIPS Embedded
20158 @subsection @acronym{MIPS} Embedded
20160 @cindex @acronym{MIPS} boards
20161 @value{GDBN} can use the @acronym{MIPS} remote debugging protocol to talk to a
20162 @acronym{MIPS} board attached to a serial line. This is available when
20163 you configure @value{GDBN} with @samp{--target=mips-elf}.
20166 Use these @value{GDBN} commands to specify the connection to your target board:
20169 @item target mips @var{port}
20170 @kindex target mips @var{port}
20171 To run a program on the board, start up @code{@value{GDBP}} with the
20172 name of your program as the argument. To connect to the board, use the
20173 command @samp{target mips @var{port}}, where @var{port} is the name of
20174 the serial port connected to the board. If the program has not already
20175 been downloaded to the board, you may use the @code{load} command to
20176 download it. You can then use all the usual @value{GDBN} commands.
20178 For example, this sequence connects to the target board through a serial
20179 port, and loads and runs a program called @var{prog} through the
20183 host$ @value{GDBP} @var{prog}
20184 @value{GDBN} is free software and @dots{}
20185 (@value{GDBP}) target mips /dev/ttyb
20186 (@value{GDBP}) load @var{prog}
20190 @item target mips @var{hostname}:@var{portnumber}
20191 On some @value{GDBN} host configurations, you can specify a TCP
20192 connection (for instance, to a serial line managed by a terminal
20193 concentrator) instead of a serial port, using the syntax
20194 @samp{@var{hostname}:@var{portnumber}}.
20196 @item target pmon @var{port}
20197 @kindex target pmon @var{port}
20200 @item target ddb @var{port}
20201 @kindex target ddb @var{port}
20202 NEC's DDB variant of PMON for Vr4300.
20204 @item target lsi @var{port}
20205 @kindex target lsi @var{port}
20206 LSI variant of PMON.
20208 @kindex target r3900
20209 @item target r3900 @var{dev}
20210 Densan DVE-R3900 ROM monitor for Toshiba R3900 Mips.
20212 @kindex target array
20213 @item target array @var{dev}
20214 Array Tech LSI33K RAID controller board.
20220 @value{GDBN} also supports these special commands for @acronym{MIPS} targets:
20223 @item set mipsfpu double
20224 @itemx set mipsfpu single
20225 @itemx set mipsfpu none
20226 @itemx set mipsfpu auto
20227 @itemx show mipsfpu
20228 @kindex set mipsfpu
20229 @kindex show mipsfpu
20230 @cindex @acronym{MIPS} remote floating point
20231 @cindex floating point, @acronym{MIPS} remote
20232 If your target board does not support the @acronym{MIPS} floating point
20233 coprocessor, you should use the command @samp{set mipsfpu none} (if you
20234 need this, you may wish to put the command in your @value{GDBN} init
20235 file). This tells @value{GDBN} how to find the return value of
20236 functions which return floating point values. It also allows
20237 @value{GDBN} to avoid saving the floating point registers when calling
20238 functions on the board. If you are using a floating point coprocessor
20239 with only single precision floating point support, as on the @sc{r4650}
20240 processor, use the command @samp{set mipsfpu single}. The default
20241 double precision floating point coprocessor may be selected using
20242 @samp{set mipsfpu double}.
20244 In previous versions the only choices were double precision or no
20245 floating point, so @samp{set mipsfpu on} will select double precision
20246 and @samp{set mipsfpu off} will select no floating point.
20248 As usual, you can inquire about the @code{mipsfpu} variable with
20249 @samp{show mipsfpu}.
20251 @item set timeout @var{seconds}
20252 @itemx set retransmit-timeout @var{seconds}
20253 @itemx show timeout
20254 @itemx show retransmit-timeout
20255 @cindex @code{timeout}, @acronym{MIPS} protocol
20256 @cindex @code{retransmit-timeout}, @acronym{MIPS} protocol
20257 @kindex set timeout
20258 @kindex show timeout
20259 @kindex set retransmit-timeout
20260 @kindex show retransmit-timeout
20261 You can control the timeout used while waiting for a packet, in the @acronym{MIPS}
20262 remote protocol, with the @code{set timeout @var{seconds}} command. The
20263 default is 5 seconds. Similarly, you can control the timeout used while
20264 waiting for an acknowledgment of a packet with the @code{set
20265 retransmit-timeout @var{seconds}} command. The default is 3 seconds.
20266 You can inspect both values with @code{show timeout} and @code{show
20267 retransmit-timeout}. (These commands are @emph{only} available when
20268 @value{GDBN} is configured for @samp{--target=mips-elf}.)
20270 The timeout set by @code{set timeout} does not apply when @value{GDBN}
20271 is waiting for your program to stop. In that case, @value{GDBN} waits
20272 forever because it has no way of knowing how long the program is going
20273 to run before stopping.
20275 @item set syn-garbage-limit @var{num}
20276 @kindex set syn-garbage-limit@r{, @acronym{MIPS} remote}
20277 @cindex synchronize with remote @acronym{MIPS} target
20278 Limit the maximum number of characters @value{GDBN} should ignore when
20279 it tries to synchronize with the remote target. The default is 10
20280 characters. Setting the limit to -1 means there's no limit.
20282 @item show syn-garbage-limit
20283 @kindex show syn-garbage-limit@r{, @acronym{MIPS} remote}
20284 Show the current limit on the number of characters to ignore when
20285 trying to synchronize with the remote system.
20287 @item set monitor-prompt @var{prompt}
20288 @kindex set monitor-prompt@r{, @acronym{MIPS} remote}
20289 @cindex remote monitor prompt
20290 Tell @value{GDBN} to expect the specified @var{prompt} string from the
20291 remote monitor. The default depends on the target:
20301 @item show monitor-prompt
20302 @kindex show monitor-prompt@r{, @acronym{MIPS} remote}
20303 Show the current strings @value{GDBN} expects as the prompt from the
20306 @item set monitor-warnings
20307 @kindex set monitor-warnings@r{, @acronym{MIPS} remote}
20308 Enable or disable monitor warnings about hardware breakpoints. This
20309 has effect only for the @code{lsi} target. When on, @value{GDBN} will
20310 display warning messages whose codes are returned by the @code{lsi}
20311 PMON monitor for breakpoint commands.
20313 @item show monitor-warnings
20314 @kindex show monitor-warnings@r{, @acronym{MIPS} remote}
20315 Show the current setting of printing monitor warnings.
20317 @item pmon @var{command}
20318 @kindex pmon@r{, @acronym{MIPS} remote}
20319 @cindex send PMON command
20320 This command allows sending an arbitrary @var{command} string to the
20321 monitor. The monitor must be in debug mode for this to work.
20324 @node OpenRISC 1000
20325 @subsection OpenRISC 1000
20326 @cindex OpenRISC 1000
20328 @cindex or1k boards
20329 See OR1k Architecture document (@uref{www.opencores.org}) for more information
20330 about platform and commands.
20334 @kindex target jtag
20335 @item target jtag jtag://@var{host}:@var{port}
20337 Connects to remote JTAG server.
20338 JTAG remote server can be either an or1ksim or JTAG server,
20339 connected via parallel port to the board.
20341 Example: @code{target jtag jtag://localhost:9999}
20344 @item or1ksim @var{command}
20345 If connected to @code{or1ksim} OpenRISC 1000 Architectural
20346 Simulator, proprietary commands can be executed.
20348 @kindex info or1k spr
20349 @item info or1k spr
20350 Displays spr groups.
20352 @item info or1k spr @var{group}
20353 @itemx info or1k spr @var{groupno}
20354 Displays register names in selected group.
20356 @item info or1k spr @var{group} @var{register}
20357 @itemx info or1k spr @var{register}
20358 @itemx info or1k spr @var{groupno} @var{registerno}
20359 @itemx info or1k spr @var{registerno}
20360 Shows information about specified spr register.
20363 @item spr @var{group} @var{register} @var{value}
20364 @itemx spr @var{register @var{value}}
20365 @itemx spr @var{groupno} @var{registerno @var{value}}
20366 @itemx spr @var{registerno @var{value}}
20367 Writes @var{value} to specified spr register.
20370 Some implementations of OpenRISC 1000 Architecture also have hardware trace.
20371 It is very similar to @value{GDBN} trace, except it does not interfere with normal
20372 program execution and is thus much faster. Hardware breakpoints/watchpoint
20373 triggers can be set using:
20376 Load effective address/data
20378 Store effective address/data
20380 Access effective address ($SEA or $LEA) or data ($SDATA/$LDATA)
20385 When triggered, it can capture low level data, like: @code{PC}, @code{LSEA},
20386 @code{LDATA}, @code{SDATA}, @code{READSPR}, @code{WRITESPR}, @code{INSTR}.
20388 @code{htrace} commands:
20389 @cindex OpenRISC 1000 htrace
20392 @item hwatch @var{conditional}
20393 Set hardware watchpoint on combination of Load/Store Effective Address(es)
20394 or Data. For example:
20396 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20398 @code{hwatch ($LEA == my_var) && ($LDATA < 50) || ($SEA == my_var) && ($SDATA >= 50)}
20402 Display information about current HW trace configuration.
20404 @item htrace trigger @var{conditional}
20405 Set starting criteria for HW trace.
20407 @item htrace qualifier @var{conditional}
20408 Set acquisition qualifier for HW trace.
20410 @item htrace stop @var{conditional}
20411 Set HW trace stopping criteria.
20413 @item htrace record [@var{data}]*
20414 Selects the data to be recorded, when qualifier is met and HW trace was
20417 @item htrace enable
20418 @itemx htrace disable
20419 Enables/disables the HW trace.
20421 @item htrace rewind [@var{filename}]
20422 Clears currently recorded trace data.
20424 If filename is specified, new trace file is made and any newly collected data
20425 will be written there.
20427 @item htrace print [@var{start} [@var{len}]]
20428 Prints trace buffer, using current record configuration.
20430 @item htrace mode continuous
20431 Set continuous trace mode.
20433 @item htrace mode suspend
20434 Set suspend trace mode.
20438 @node PowerPC Embedded
20439 @subsection PowerPC Embedded
20441 @cindex DVC register
20442 @value{GDBN} supports using the DVC (Data Value Compare) register to
20443 implement in hardware simple hardware watchpoint conditions of the form:
20446 (@value{GDBP}) watch @var{ADDRESS|VARIABLE} \
20447 if @var{ADDRESS|VARIABLE} == @var{CONSTANT EXPRESSION}
20450 The DVC register will be automatically used when @value{GDBN} detects
20451 such pattern in a condition expression, and the created watchpoint uses one
20452 debug register (either the @code{exact-watchpoints} option is on and the
20453 variable is scalar, or the variable has a length of one byte). This feature
20454 is available in native @value{GDBN} running on a Linux kernel version 2.6.34
20457 When running on PowerPC embedded processors, @value{GDBN} automatically uses
20458 ranged hardware watchpoints, unless the @code{exact-watchpoints} option is on,
20459 in which case watchpoints using only one debug register are created when
20460 watching variables of scalar types.
20462 You can create an artificial array to watch an arbitrary memory
20463 region using one of the following commands (@pxref{Expressions}):
20466 (@value{GDBP}) watch *((char *) @var{address})@@@var{length}
20467 (@value{GDBP}) watch @{char[@var{length}]@} @var{address}
20470 PowerPC embedded processors support masked watchpoints. See the discussion
20471 about the @code{mask} argument in @ref{Set Watchpoints}.
20473 @cindex ranged breakpoint
20474 PowerPC embedded processors support hardware accelerated
20475 @dfn{ranged breakpoints}. A ranged breakpoint stops execution of
20476 the inferior whenever it executes an instruction at any address within
20477 the range it specifies. To set a ranged breakpoint in @value{GDBN},
20478 use the @code{break-range} command.
20480 @value{GDBN} provides the following PowerPC-specific commands:
20483 @kindex break-range
20484 @item break-range @var{start-location}, @var{end-location}
20485 Set a breakpoint for an address range.
20486 @var{start-location} and @var{end-location} can specify a function name,
20487 a line number, an offset of lines from the current line or from the start
20488 location, or an address of an instruction (see @ref{Specify Location},
20489 for a list of all the possible ways to specify a @var{location}.)
20490 The breakpoint will stop execution of the inferior whenever it
20491 executes an instruction at any address within the specified range,
20492 (including @var{start-location} and @var{end-location}.)
20494 @kindex set powerpc
20495 @item set powerpc soft-float
20496 @itemx show powerpc soft-float
20497 Force @value{GDBN} to use (or not use) a software floating point calling
20498 convention. By default, @value{GDBN} selects the calling convention based
20499 on the selected architecture and the provided executable file.
20501 @item set powerpc vector-abi
20502 @itemx show powerpc vector-abi
20503 Force @value{GDBN} to use the specified calling convention for vector
20504 arguments and return values. The valid options are @samp{auto};
20505 @samp{generic}, to avoid vector registers even if they are present;
20506 @samp{altivec}, to use AltiVec registers; and @samp{spe} to use SPE
20507 registers. By default, @value{GDBN} selects the calling convention
20508 based on the selected architecture and the provided executable file.
20510 @item set powerpc exact-watchpoints
20511 @itemx show powerpc exact-watchpoints
20512 Allow @value{GDBN} to use only one debug register when watching a variable
20513 of scalar type, thus assuming that the variable is accessed through the
20514 address of its first byte.
20516 @kindex target dink32
20517 @item target dink32 @var{dev}
20518 DINK32 ROM monitor.
20520 @kindex target ppcbug
20521 @item target ppcbug @var{dev}
20522 @kindex target ppcbug1
20523 @item target ppcbug1 @var{dev}
20524 PPCBUG ROM monitor for PowerPC.
20527 @item target sds @var{dev}
20528 SDS monitor, running on a PowerPC board (such as Motorola's ADS).
20531 @cindex SDS protocol
20532 The following commands specific to the SDS protocol are supported
20536 @item set sdstimeout @var{nsec}
20537 @kindex set sdstimeout
20538 Set the timeout for SDS protocol reads to be @var{nsec} seconds. The
20539 default is 2 seconds.
20541 @item show sdstimeout
20542 @kindex show sdstimeout
20543 Show the current value of the SDS timeout.
20545 @item sds @var{command}
20546 @kindex sds@r{, a command}
20547 Send the specified @var{command} string to the SDS monitor.
20552 @subsection HP PA Embedded
20556 @kindex target op50n
20557 @item target op50n @var{dev}
20558 OP50N monitor, running on an OKI HPPA board.
20560 @kindex target w89k
20561 @item target w89k @var{dev}
20562 W89K monitor, running on a Winbond HPPA board.
20567 @subsection Tsqware Sparclet
20571 @value{GDBN} enables developers to debug tasks running on
20572 Sparclet targets from a Unix host.
20573 @value{GDBN} uses code that runs on
20574 both the Unix host and on the Sparclet target. The program
20575 @code{@value{GDBP}} is installed and executed on the Unix host.
20578 @item remotetimeout @var{args}
20579 @kindex remotetimeout
20580 @value{GDBN} supports the option @code{remotetimeout}.
20581 This option is set by the user, and @var{args} represents the number of
20582 seconds @value{GDBN} waits for responses.
20585 @cindex compiling, on Sparclet
20586 When compiling for debugging, include the options @samp{-g} to get debug
20587 information and @samp{-Ttext} to relocate the program to where you wish to
20588 load it on the target. You may also want to add the options @samp{-n} or
20589 @samp{-N} in order to reduce the size of the sections. Example:
20592 sparclet-aout-gcc prog.c -Ttext 0x12010000 -g -o prog -N
20595 You can use @code{objdump} to verify that the addresses are what you intended:
20598 sparclet-aout-objdump --headers --syms prog
20601 @cindex running, on Sparclet
20603 your Unix execution search path to find @value{GDBN}, you are ready to
20604 run @value{GDBN}. From your Unix host, run @code{@value{GDBP}}
20605 (or @code{sparclet-aout-gdb}, depending on your installation).
20607 @value{GDBN} comes up showing the prompt:
20614 * Sparclet File:: Setting the file to debug
20615 * Sparclet Connection:: Connecting to Sparclet
20616 * Sparclet Download:: Sparclet download
20617 * Sparclet Execution:: Running and debugging
20620 @node Sparclet File
20621 @subsubsection Setting File to Debug
20623 The @value{GDBN} command @code{file} lets you choose with program to debug.
20626 (gdbslet) file prog
20630 @value{GDBN} then attempts to read the symbol table of @file{prog}.
20631 @value{GDBN} locates
20632 the file by searching the directories listed in the command search
20634 If the file was compiled with debug information (option @samp{-g}), source
20635 files will be searched as well.
20636 @value{GDBN} locates
20637 the source files by searching the directories listed in the directory search
20638 path (@pxref{Environment, ,Your Program's Environment}).
20640 to find a file, it displays a message such as:
20643 prog: No such file or directory.
20646 When this happens, add the appropriate directories to the search paths with
20647 the @value{GDBN} commands @code{path} and @code{dir}, and execute the
20648 @code{target} command again.
20650 @node Sparclet Connection
20651 @subsubsection Connecting to Sparclet
20653 The @value{GDBN} command @code{target} lets you connect to a Sparclet target.
20654 To connect to a target on serial port ``@code{ttya}'', type:
20657 (gdbslet) target sparclet /dev/ttya
20658 Remote target sparclet connected to /dev/ttya
20659 main () at ../prog.c:3
20663 @value{GDBN} displays messages like these:
20669 @node Sparclet Download
20670 @subsubsection Sparclet Download
20672 @cindex download to Sparclet
20673 Once connected to the Sparclet target,
20674 you can use the @value{GDBN}
20675 @code{load} command to download the file from the host to the target.
20676 The file name and load offset should be given as arguments to the @code{load}
20678 Since the file format is aout, the program must be loaded to the starting
20679 address. You can use @code{objdump} to find out what this value is. The load
20680 offset is an offset which is added to the VMA (virtual memory address)
20681 of each of the file's sections.
20682 For instance, if the program
20683 @file{prog} was linked to text address 0x1201000, with data at 0x12010160
20684 and bss at 0x12010170, in @value{GDBN}, type:
20687 (gdbslet) load prog 0x12010000
20688 Loading section .text, size 0xdb0 vma 0x12010000
20691 If the code is loaded at a different address then what the program was linked
20692 to, you may need to use the @code{section} and @code{add-symbol-file} commands
20693 to tell @value{GDBN} where to map the symbol table.
20695 @node Sparclet Execution
20696 @subsubsection Running and Debugging
20698 @cindex running and debugging Sparclet programs
20699 You can now begin debugging the task using @value{GDBN}'s execution control
20700 commands, @code{b}, @code{step}, @code{run}, etc. See the @value{GDBN}
20701 manual for the list of commands.
20705 Breakpoint 1 at 0x12010000: file prog.c, line 3.
20707 Starting program: prog
20708 Breakpoint 1, main (argc=1, argv=0xeffff21c) at prog.c:3
20709 3 char *symarg = 0;
20711 4 char *execarg = "hello!";
20716 @subsection Fujitsu Sparclite
20720 @kindex target sparclite
20721 @item target sparclite @var{dev}
20722 Fujitsu sparclite boards, used only for the purpose of loading.
20723 You must use an additional command to debug the program.
20724 For example: target remote @var{dev} using @value{GDBN} standard
20730 @subsection Zilog Z8000
20733 @cindex simulator, Z8000
20734 @cindex Zilog Z8000 simulator
20736 When configured for debugging Zilog Z8000 targets, @value{GDBN} includes
20739 For the Z8000 family, @samp{target sim} simulates either the Z8002 (the
20740 unsegmented variant of the Z8000 architecture) or the Z8001 (the
20741 segmented variant). The simulator recognizes which architecture is
20742 appropriate by inspecting the object code.
20745 @item target sim @var{args}
20747 @kindex target sim@r{, with Z8000}
20748 Debug programs on a simulated CPU. If the simulator supports setup
20749 options, specify them via @var{args}.
20753 After specifying this target, you can debug programs for the simulated
20754 CPU in the same style as programs for your host computer; use the
20755 @code{file} command to load a new program image, the @code{run} command
20756 to run your program, and so on.
20758 As well as making available all the usual machine registers
20759 (@pxref{Registers, ,Registers}), the Z8000 simulator provides three
20760 additional items of information as specially named registers:
20765 Counts clock-ticks in the simulator.
20768 Counts instructions run in the simulator.
20771 Execution time in 60ths of a second.
20775 You can refer to these values in @value{GDBN} expressions with the usual
20776 conventions; for example, @w{@samp{b fputc if $cycles>5000}} sets a
20777 conditional breakpoint that suspends only after at least 5000
20778 simulated clock ticks.
20781 @subsection Atmel AVR
20784 When configured for debugging the Atmel AVR, @value{GDBN} supports the
20785 following AVR-specific commands:
20788 @item info io_registers
20789 @kindex info io_registers@r{, AVR}
20790 @cindex I/O registers (Atmel AVR)
20791 This command displays information about the AVR I/O registers. For
20792 each register, @value{GDBN} prints its number and value.
20799 When configured for debugging CRIS, @value{GDBN} provides the
20800 following CRIS-specific commands:
20803 @item set cris-version @var{ver}
20804 @cindex CRIS version
20805 Set the current CRIS version to @var{ver}, either @samp{10} or @samp{32}.
20806 The CRIS version affects register names and sizes. This command is useful in
20807 case autodetection of the CRIS version fails.
20809 @item show cris-version
20810 Show the current CRIS version.
20812 @item set cris-dwarf2-cfi
20813 @cindex DWARF-2 CFI and CRIS
20814 Set the usage of DWARF-2 CFI for CRIS debugging. The default is @samp{on}.
20815 Change to @samp{off} when using @code{gcc-cris} whose version is below
20818 @item show cris-dwarf2-cfi
20819 Show the current state of using DWARF-2 CFI.
20821 @item set cris-mode @var{mode}
20823 Set the current CRIS mode to @var{mode}. It should only be changed when
20824 debugging in guru mode, in which case it should be set to
20825 @samp{guru} (the default is @samp{normal}).
20827 @item show cris-mode
20828 Show the current CRIS mode.
20832 @subsection Renesas Super-H
20835 For the Renesas Super-H processor, @value{GDBN} provides these
20839 @item set sh calling-convention @var{convention}
20840 @kindex set sh calling-convention
20841 Set the calling-convention used when calling functions from @value{GDBN}.
20842 Allowed values are @samp{gcc}, which is the default setting, and @samp{renesas}.
20843 With the @samp{gcc} setting, functions are called using the @value{NGCC} calling
20844 convention. If the DWARF-2 information of the called function specifies
20845 that the function follows the Renesas calling convention, the function
20846 is called using the Renesas calling convention. If the calling convention
20847 is set to @samp{renesas}, the Renesas calling convention is always used,
20848 regardless of the DWARF-2 information. This can be used to override the
20849 default of @samp{gcc} if debug information is missing, or the compiler
20850 does not emit the DWARF-2 calling convention entry for a function.
20852 @item show sh calling-convention
20853 @kindex show sh calling-convention
20854 Show the current calling convention setting.
20859 @node Architectures
20860 @section Architectures
20862 This section describes characteristics of architectures that affect
20863 all uses of @value{GDBN} with the architecture, both native and cross.
20870 * HPPA:: HP PA architecture
20871 * SPU:: Cell Broadband Engine SPU architecture
20876 @subsection AArch64
20877 @cindex AArch64 support
20879 When @value{GDBN} is debugging the AArch64 architecture, it provides the
20880 following special commands:
20883 @item set debug aarch64
20884 @kindex set debug aarch64
20885 This command determines whether AArch64 architecture-specific debugging
20886 messages are to be displayed.
20888 @item show debug aarch64
20889 Show whether AArch64 debugging messages are displayed.
20894 @subsection x86 Architecture-specific Issues
20897 @item set struct-convention @var{mode}
20898 @kindex set struct-convention
20899 @cindex struct return convention
20900 @cindex struct/union returned in registers
20901 Set the convention used by the inferior to return @code{struct}s and
20902 @code{union}s from functions to @var{mode}. Possible values of
20903 @var{mode} are @code{"pcc"}, @code{"reg"}, and @code{"default"} (the
20904 default). @code{"default"} or @code{"pcc"} means that @code{struct}s
20905 are returned on the stack, while @code{"reg"} means that a
20906 @code{struct} or a @code{union} whose size is 1, 2, 4, or 8 bytes will
20907 be returned in a register.
20909 @item show struct-convention
20910 @kindex show struct-convention
20911 Show the current setting of the convention to return @code{struct}s
20918 See the following section.
20921 @subsection @acronym{MIPS}
20923 @cindex stack on Alpha
20924 @cindex stack on @acronym{MIPS}
20925 @cindex Alpha stack
20926 @cindex @acronym{MIPS} stack
20927 Alpha- and @acronym{MIPS}-based computers use an unusual stack frame, which
20928 sometimes requires @value{GDBN} to search backward in the object code to
20929 find the beginning of a function.
20931 @cindex response time, @acronym{MIPS} debugging
20932 To improve response time (especially for embedded applications, where
20933 @value{GDBN} may be restricted to a slow serial line for this search)
20934 you may want to limit the size of this search, using one of these
20938 @cindex @code{heuristic-fence-post} (Alpha, @acronym{MIPS})
20939 @item set heuristic-fence-post @var{limit}
20940 Restrict @value{GDBN} to examining at most @var{limit} bytes in its
20941 search for the beginning of a function. A value of @var{0} (the
20942 default) means there is no limit. However, except for @var{0}, the
20943 larger the limit the more bytes @code{heuristic-fence-post} must search
20944 and therefore the longer it takes to run. You should only need to use
20945 this command when debugging a stripped executable.
20947 @item show heuristic-fence-post
20948 Display the current limit.
20952 These commands are available @emph{only} when @value{GDBN} is configured
20953 for debugging programs on Alpha or @acronym{MIPS} processors.
20955 Several @acronym{MIPS}-specific commands are available when debugging @acronym{MIPS}
20959 @item set mips abi @var{arg}
20960 @kindex set mips abi
20961 @cindex set ABI for @acronym{MIPS}
20962 Tell @value{GDBN} which @acronym{MIPS} ABI is used by the inferior. Possible
20963 values of @var{arg} are:
20967 The default ABI associated with the current binary (this is the
20977 @item show mips abi
20978 @kindex show mips abi
20979 Show the @acronym{MIPS} ABI used by @value{GDBN} to debug the inferior.
20981 @item set mips compression @var{arg}
20982 @kindex set mips compression
20983 @cindex code compression, @acronym{MIPS}
20984 Tell @value{GDBN} which @acronym{MIPS} compressed
20985 @acronym{ISA, Instruction Set Architecture} encoding is used by the
20986 inferior. @value{GDBN} uses this for code disassembly and other
20987 internal interpretation purposes. This setting is only referred to
20988 when no executable has been associated with the debugging session or
20989 the executable does not provide information about the encoding it uses.
20990 Otherwise this setting is automatically updated from information
20991 provided by the executable.
20993 Possible values of @var{arg} are @samp{mips16} and @samp{micromips}.
20994 The default compressed @acronym{ISA} encoding is @samp{mips16}, as
20995 executables containing @acronym{MIPS16} code frequently are not
20996 identified as such.
20998 This setting is ``sticky''; that is, it retains its value across
20999 debugging sessions until reset either explicitly with this command or
21000 implicitly from an executable.
21002 The compiler and/or assembler typically add symbol table annotations to
21003 identify functions compiled for the @acronym{MIPS16} or
21004 @acronym{microMIPS} @acronym{ISA}s. If these function-scope annotations
21005 are present, @value{GDBN} uses them in preference to the global
21006 compressed @acronym{ISA} encoding setting.
21008 @item show mips compression
21009 @kindex show mips compression
21010 Show the @acronym{MIPS} compressed @acronym{ISA} encoding used by
21011 @value{GDBN} to debug the inferior.
21014 @itemx show mipsfpu
21015 @xref{MIPS Embedded, set mipsfpu}.
21017 @item set mips mask-address @var{arg}
21018 @kindex set mips mask-address
21019 @cindex @acronym{MIPS} addresses, masking
21020 This command determines whether the most-significant 32 bits of 64-bit
21021 @acronym{MIPS} addresses are masked off. The argument @var{arg} can be
21022 @samp{on}, @samp{off}, or @samp{auto}. The latter is the default
21023 setting, which lets @value{GDBN} determine the correct value.
21025 @item show mips mask-address
21026 @kindex show mips mask-address
21027 Show whether the upper 32 bits of @acronym{MIPS} addresses are masked off or
21030 @item set remote-mips64-transfers-32bit-regs
21031 @kindex set remote-mips64-transfers-32bit-regs
21032 This command controls compatibility with 64-bit @acronym{MIPS} targets that
21033 transfer data in 32-bit quantities. If you have an old @acronym{MIPS} 64 target
21034 that transfers 32 bits for some registers, like @sc{sr} and @sc{fsr},
21035 and 64 bits for other registers, set this option to @samp{on}.
21037 @item show remote-mips64-transfers-32bit-regs
21038 @kindex show remote-mips64-transfers-32bit-regs
21039 Show the current setting of compatibility with older @acronym{MIPS} 64 targets.
21041 @item set debug mips
21042 @kindex set debug mips
21043 This command turns on and off debugging messages for the @acronym{MIPS}-specific
21044 target code in @value{GDBN}.
21046 @item show debug mips
21047 @kindex show debug mips
21048 Show the current setting of @acronym{MIPS} debugging messages.
21054 @cindex HPPA support
21056 When @value{GDBN} is debugging the HP PA architecture, it provides the
21057 following special commands:
21060 @item set debug hppa
21061 @kindex set debug hppa
21062 This command determines whether HPPA architecture-specific debugging
21063 messages are to be displayed.
21065 @item show debug hppa
21066 Show whether HPPA debugging messages are displayed.
21068 @item maint print unwind @var{address}
21069 @kindex maint print unwind@r{, HPPA}
21070 This command displays the contents of the unwind table entry at the
21071 given @var{address}.
21077 @subsection Cell Broadband Engine SPU architecture
21078 @cindex Cell Broadband Engine
21081 When @value{GDBN} is debugging the Cell Broadband Engine SPU architecture,
21082 it provides the following special commands:
21085 @item info spu event
21087 Display SPU event facility status. Shows current event mask
21088 and pending event status.
21090 @item info spu signal
21091 Display SPU signal notification facility status. Shows pending
21092 signal-control word and signal notification mode of both signal
21093 notification channels.
21095 @item info spu mailbox
21096 Display SPU mailbox facility status. Shows all pending entries,
21097 in order of processing, in each of the SPU Write Outbound,
21098 SPU Write Outbound Interrupt, and SPU Read Inbound mailboxes.
21101 Display MFC DMA status. Shows all pending commands in the MFC
21102 DMA queue. For each entry, opcode, tag, class IDs, effective
21103 and local store addresses and transfer size are shown.
21105 @item info spu proxydma
21106 Display MFC Proxy-DMA status. Shows all pending commands in the MFC
21107 Proxy-DMA queue. For each entry, opcode, tag, class IDs, effective
21108 and local store addresses and transfer size are shown.
21112 When @value{GDBN} is debugging a combined PowerPC/SPU application
21113 on the Cell Broadband Engine, it provides in addition the following
21117 @item set spu stop-on-load @var{arg}
21119 Set whether to stop for new SPE threads. When set to @code{on}, @value{GDBN}
21120 will give control to the user when a new SPE thread enters its @code{main}
21121 function. The default is @code{off}.
21123 @item show spu stop-on-load
21125 Show whether to stop for new SPE threads.
21127 @item set spu auto-flush-cache @var{arg}
21128 Set whether to automatically flush the software-managed cache. When set to
21129 @code{on}, @value{GDBN} will automatically cause the SPE software-managed
21130 cache to be flushed whenever SPE execution stops. This provides a consistent
21131 view of PowerPC memory that is accessed via the cache. If an application
21132 does not use the software-managed cache, this option has no effect.
21134 @item show spu auto-flush-cache
21135 Show whether to automatically flush the software-managed cache.
21140 @subsection PowerPC
21141 @cindex PowerPC architecture
21143 When @value{GDBN} is debugging the PowerPC architecture, it provides a set of
21144 pseudo-registers to enable inspection of 128-bit wide Decimal Floating Point
21145 numbers stored in the floating point registers. These values must be stored
21146 in two consecutive registers, always starting at an even register like
21147 @code{f0} or @code{f2}.
21149 The pseudo-registers go from @code{$dl0} through @code{$dl15}, and are formed
21150 by joining the even/odd register pairs @code{f0} and @code{f1} for @code{$dl0},
21151 @code{f2} and @code{f3} for @code{$dl1} and so on.
21153 For POWER7 processors, @value{GDBN} provides a set of pseudo-registers, the 64-bit
21154 wide Extended Floating Point Registers (@samp{f32} through @samp{f63}).
21157 @node Controlling GDB
21158 @chapter Controlling @value{GDBN}
21160 You can alter the way @value{GDBN} interacts with you by using the
21161 @code{set} command. For commands controlling how @value{GDBN} displays
21162 data, see @ref{Print Settings, ,Print Settings}. Other settings are
21167 * Editing:: Command editing
21168 * Command History:: Command history
21169 * Screen Size:: Screen size
21170 * Numbers:: Numbers
21171 * ABI:: Configuring the current ABI
21172 * Auto-loading:: Automatically loading associated files
21173 * Messages/Warnings:: Optional warnings and messages
21174 * Debugging Output:: Optional messages about internal happenings
21175 * Other Misc Settings:: Other Miscellaneous Settings
21183 @value{GDBN} indicates its readiness to read a command by printing a string
21184 called the @dfn{prompt}. This string is normally @samp{(@value{GDBP})}. You
21185 can change the prompt string with the @code{set prompt} command. For
21186 instance, when debugging @value{GDBN} with @value{GDBN}, it is useful to change
21187 the prompt in one of the @value{GDBN} sessions so that you can always tell
21188 which one you are talking to.
21190 @emph{Note:} @code{set prompt} does not add a space for you after the
21191 prompt you set. This allows you to set a prompt which ends in a space
21192 or a prompt that does not.
21196 @item set prompt @var{newprompt}
21197 Directs @value{GDBN} to use @var{newprompt} as its prompt string henceforth.
21199 @kindex show prompt
21201 Prints a line of the form: @samp{Gdb's prompt is: @var{your-prompt}}
21204 Versions of @value{GDBN} that ship with Python scripting enabled have
21205 prompt extensions. The commands for interacting with these extensions
21209 @kindex set extended-prompt
21210 @item set extended-prompt @var{prompt}
21211 Set an extended prompt that allows for substitutions.
21212 @xref{gdb.prompt}, for a list of escape sequences that can be used for
21213 substitution. Any escape sequences specified as part of the prompt
21214 string are replaced with the corresponding strings each time the prompt
21220 set extended-prompt Current working directory: \w (gdb)
21223 Note that when an extended-prompt is set, it takes control of the
21224 @var{prompt_hook} hook. @xref{prompt_hook}, for further information.
21226 @kindex show extended-prompt
21227 @item show extended-prompt
21228 Prints the extended prompt. Any escape sequences specified as part of
21229 the prompt string with @code{set extended-prompt}, are replaced with the
21230 corresponding strings each time the prompt is displayed.
21234 @section Command Editing
21236 @cindex command line editing
21238 @value{GDBN} reads its input commands via the @dfn{Readline} interface. This
21239 @sc{gnu} library provides consistent behavior for programs which provide a
21240 command line interface to the user. Advantages are @sc{gnu} Emacs-style
21241 or @dfn{vi}-style inline editing of commands, @code{csh}-like history
21242 substitution, and a storage and recall of command history across
21243 debugging sessions.
21245 You may control the behavior of command line editing in @value{GDBN} with the
21246 command @code{set}.
21249 @kindex set editing
21252 @itemx set editing on
21253 Enable command line editing (enabled by default).
21255 @item set editing off
21256 Disable command line editing.
21258 @kindex show editing
21260 Show whether command line editing is enabled.
21263 @ifset SYSTEM_READLINE
21264 @xref{Command Line Editing, , , rluserman, GNU Readline Library},
21266 @ifclear SYSTEM_READLINE
21267 @xref{Command Line Editing},
21269 for more details about the Readline
21270 interface. Users unfamiliar with @sc{gnu} Emacs or @code{vi} are
21271 encouraged to read that chapter.
21273 @node Command History
21274 @section Command History
21275 @cindex command history
21277 @value{GDBN} can keep track of the commands you type during your
21278 debugging sessions, so that you can be certain of precisely what
21279 happened. Use these commands to manage the @value{GDBN} command
21282 @value{GDBN} uses the @sc{gnu} History library, a part of the Readline
21283 package, to provide the history facility.
21284 @ifset SYSTEM_READLINE
21285 @xref{Using History Interactively, , , history, GNU History Library},
21287 @ifclear SYSTEM_READLINE
21288 @xref{Using History Interactively},
21290 for the detailed description of the History library.
21292 To issue a command to @value{GDBN} without affecting certain aspects of
21293 the state which is seen by users, prefix it with @samp{server }
21294 (@pxref{Server Prefix}). This
21295 means that this command will not affect the command history, nor will it
21296 affect @value{GDBN}'s notion of which command to repeat if @key{RET} is
21297 pressed on a line by itself.
21299 @cindex @code{server}, command prefix
21300 The server prefix does not affect the recording of values into the value
21301 history; to print a value without recording it into the value history,
21302 use the @code{output} command instead of the @code{print} command.
21304 Here is the description of @value{GDBN} commands related to command
21308 @cindex history substitution
21309 @cindex history file
21310 @kindex set history filename
21311 @cindex @env{GDBHISTFILE}, environment variable
21312 @item set history filename @var{fname}
21313 Set the name of the @value{GDBN} command history file to @var{fname}.
21314 This is the file where @value{GDBN} reads an initial command history
21315 list, and where it writes the command history from this session when it
21316 exits. You can access this list through history expansion or through
21317 the history command editing characters listed below. This file defaults
21318 to the value of the environment variable @code{GDBHISTFILE}, or to
21319 @file{./.gdb_history} (@file{./_gdb_history} on MS-DOS) if this variable
21322 @cindex save command history
21323 @kindex set history save
21324 @item set history save
21325 @itemx set history save on
21326 Record command history in a file, whose name may be specified with the
21327 @code{set history filename} command. By default, this option is disabled.
21329 @item set history save off
21330 Stop recording command history in a file.
21332 @cindex history size
21333 @kindex set history size
21334 @cindex @env{HISTSIZE}, environment variable
21335 @item set history size @var{size}
21336 Set the number of commands which @value{GDBN} keeps in its history list.
21337 This defaults to the value of the environment variable
21338 @code{HISTSIZE}, or to 256 if this variable is not set.
21341 History expansion assigns special meaning to the character @kbd{!}.
21342 @ifset SYSTEM_READLINE
21343 @xref{Event Designators, , , history, GNU History Library},
21345 @ifclear SYSTEM_READLINE
21346 @xref{Event Designators},
21350 @cindex history expansion, turn on/off
21351 Since @kbd{!} is also the logical not operator in C, history expansion
21352 is off by default. If you decide to enable history expansion with the
21353 @code{set history expansion on} command, you may sometimes need to
21354 follow @kbd{!} (when it is used as logical not, in an expression) with
21355 a space or a tab to prevent it from being expanded. The readline
21356 history facilities do not attempt substitution on the strings
21357 @kbd{!=} and @kbd{!(}, even when history expansion is enabled.
21359 The commands to control history expansion are:
21362 @item set history expansion on
21363 @itemx set history expansion
21364 @kindex set history expansion
21365 Enable history expansion. History expansion is off by default.
21367 @item set history expansion off
21368 Disable history expansion.
21371 @kindex show history
21373 @itemx show history filename
21374 @itemx show history save
21375 @itemx show history size
21376 @itemx show history expansion
21377 These commands display the state of the @value{GDBN} history parameters.
21378 @code{show history} by itself displays all four states.
21383 @kindex show commands
21384 @cindex show last commands
21385 @cindex display command history
21386 @item show commands
21387 Display the last ten commands in the command history.
21389 @item show commands @var{n}
21390 Print ten commands centered on command number @var{n}.
21392 @item show commands +
21393 Print ten commands just after the commands last printed.
21397 @section Screen Size
21398 @cindex size of screen
21399 @cindex pauses in output
21401 Certain commands to @value{GDBN} may produce large amounts of
21402 information output to the screen. To help you read all of it,
21403 @value{GDBN} pauses and asks you for input at the end of each page of
21404 output. Type @key{RET} when you want to continue the output, or @kbd{q}
21405 to discard the remaining output. Also, the screen width setting
21406 determines when to wrap lines of output. Depending on what is being
21407 printed, @value{GDBN} tries to break the line at a readable place,
21408 rather than simply letting it overflow onto the following line.
21410 Normally @value{GDBN} knows the size of the screen from the terminal
21411 driver software. For example, on Unix @value{GDBN} uses the termcap data base
21412 together with the value of the @code{TERM} environment variable and the
21413 @code{stty rows} and @code{stty cols} settings. If this is not correct,
21414 you can override it with the @code{set height} and @code{set
21421 @kindex show height
21422 @item set height @var{lpp}
21424 @itemx set width @var{cpl}
21426 These @code{set} commands specify a screen height of @var{lpp} lines and
21427 a screen width of @var{cpl} characters. The associated @code{show}
21428 commands display the current settings.
21430 If you specify a height of zero lines, @value{GDBN} does not pause during
21431 output no matter how long the output is. This is useful if output is to a
21432 file or to an editor buffer.
21434 Likewise, you can specify @samp{set width 0} to prevent @value{GDBN}
21435 from wrapping its output.
21437 @item set pagination on
21438 @itemx set pagination off
21439 @kindex set pagination
21440 Turn the output pagination on or off; the default is on. Turning
21441 pagination off is the alternative to @code{set height 0}. Note that
21442 running @value{GDBN} with the @option{--batch} option (@pxref{Mode
21443 Options, -batch}) also automatically disables pagination.
21445 @item show pagination
21446 @kindex show pagination
21447 Show the current pagination mode.
21452 @cindex number representation
21453 @cindex entering numbers
21455 You can always enter numbers in octal, decimal, or hexadecimal in
21456 @value{GDBN} by the usual conventions: octal numbers begin with
21457 @samp{0}, decimal numbers end with @samp{.}, and hexadecimal numbers
21458 begin with @samp{0x}. Numbers that neither begin with @samp{0} or
21459 @samp{0x}, nor end with a @samp{.} are, by default, entered in base
21460 10; likewise, the default display for numbers---when no particular
21461 format is specified---is base 10. You can change the default base for
21462 both input and output with the commands described below.
21465 @kindex set input-radix
21466 @item set input-radix @var{base}
21467 Set the default base for numeric input. Supported choices
21468 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21469 specified either unambiguously or using the current input radix; for
21473 set input-radix 012
21474 set input-radix 10.
21475 set input-radix 0xa
21479 sets the input base to decimal. On the other hand, @samp{set input-radix 10}
21480 leaves the input radix unchanged, no matter what it was, since
21481 @samp{10}, being without any leading or trailing signs of its base, is
21482 interpreted in the current radix. Thus, if the current radix is 16,
21483 @samp{10} is interpreted in hex, i.e.@: as 16 decimal, which doesn't
21486 @kindex set output-radix
21487 @item set output-radix @var{base}
21488 Set the default base for numeric display. Supported choices
21489 for @var{base} are decimal 8, 10, or 16. @var{base} must itself be
21490 specified either unambiguously or using the current input radix.
21492 @kindex show input-radix
21493 @item show input-radix
21494 Display the current default base for numeric input.
21496 @kindex show output-radix
21497 @item show output-radix
21498 Display the current default base for numeric display.
21500 @item set radix @r{[}@var{base}@r{]}
21504 These commands set and show the default base for both input and output
21505 of numbers. @code{set radix} sets the radix of input and output to
21506 the same base; without an argument, it resets the radix back to its
21507 default value of 10.
21512 @section Configuring the Current ABI
21514 @value{GDBN} can determine the @dfn{ABI} (Application Binary Interface) of your
21515 application automatically. However, sometimes you need to override its
21516 conclusions. Use these commands to manage @value{GDBN}'s view of the
21522 @cindex Newlib OS ABI and its influence on the longjmp handling
21524 One @value{GDBN} configuration can debug binaries for multiple operating
21525 system targets, either via remote debugging or native emulation.
21526 @value{GDBN} will autodetect the @dfn{OS ABI} (Operating System ABI) in use,
21527 but you can override its conclusion using the @code{set osabi} command.
21528 One example where this is useful is in debugging of binaries which use
21529 an alternate C library (e.g.@: @sc{uClibc} for @sc{gnu}/Linux) which does
21530 not have the same identifying marks that the standard C library for your
21533 When @value{GDBN} is debugging the AArch64 architecture, it provides a
21534 ``Newlib'' OS ABI. This is useful for handling @code{setjmp} and
21535 @code{longjmp} when debugging binaries that use the @sc{newlib} C library.
21536 The ``Newlib'' OS ABI can be selected by @code{set osabi Newlib}.
21540 Show the OS ABI currently in use.
21543 With no argument, show the list of registered available OS ABI's.
21545 @item set osabi @var{abi}
21546 Set the current OS ABI to @var{abi}.
21549 @cindex float promotion
21551 Generally, the way that an argument of type @code{float} is passed to a
21552 function depends on whether the function is prototyped. For a prototyped
21553 (i.e.@: ANSI/ISO style) function, @code{float} arguments are passed unchanged,
21554 according to the architecture's convention for @code{float}. For unprototyped
21555 (i.e.@: K&R style) functions, @code{float} arguments are first promoted to type
21556 @code{double} and then passed.
21558 Unfortunately, some forms of debug information do not reliably indicate whether
21559 a function is prototyped. If @value{GDBN} calls a function that is not marked
21560 as prototyped, it consults @kbd{set coerce-float-to-double}.
21563 @kindex set coerce-float-to-double
21564 @item set coerce-float-to-double
21565 @itemx set coerce-float-to-double on
21566 Arguments of type @code{float} will be promoted to @code{double} when passed
21567 to an unprototyped function. This is the default setting.
21569 @item set coerce-float-to-double off
21570 Arguments of type @code{float} will be passed directly to unprototyped
21573 @kindex show coerce-float-to-double
21574 @item show coerce-float-to-double
21575 Show the current setting of promoting @code{float} to @code{double}.
21579 @kindex show cp-abi
21580 @value{GDBN} needs to know the ABI used for your program's C@t{++}
21581 objects. The correct C@t{++} ABI depends on which C@t{++} compiler was
21582 used to build your application. @value{GDBN} only fully supports
21583 programs with a single C@t{++} ABI; if your program contains code using
21584 multiple C@t{++} ABI's or if @value{GDBN} can not identify your
21585 program's ABI correctly, you can tell @value{GDBN} which ABI to use.
21586 Currently supported ABI's include ``gnu-v2'', for @code{g++} versions
21587 before 3.0, ``gnu-v3'', for @code{g++} versions 3.0 and later, and
21588 ``hpaCC'' for the HP ANSI C@t{++} compiler. Other C@t{++} compilers may
21589 use the ``gnu-v2'' or ``gnu-v3'' ABI's as well. The default setting is
21594 Show the C@t{++} ABI currently in use.
21597 With no argument, show the list of supported C@t{++} ABI's.
21599 @item set cp-abi @var{abi}
21600 @itemx set cp-abi auto
21601 Set the current C@t{++} ABI to @var{abi}, or return to automatic detection.
21605 @section Automatically loading associated files
21606 @cindex auto-loading
21608 @value{GDBN} sometimes reads files with commands and settings automatically,
21609 without being explicitly told so by the user. We call this feature
21610 @dfn{auto-loading}. While auto-loading is useful for automatically adapting
21611 @value{GDBN} to the needs of your project, it can sometimes produce unexpected
21612 results or introduce security risks (e.g., if the file comes from untrusted
21615 Note that loading of these associated files (including the local @file{.gdbinit}
21616 file) requires accordingly configured @code{auto-load safe-path}
21617 (@pxref{Auto-loading safe path}).
21619 For these reasons, @value{GDBN} includes commands and options to let you
21620 control when to auto-load files and which files should be auto-loaded.
21623 @anchor{set auto-load off}
21624 @kindex set auto-load off
21625 @item set auto-load off
21626 Globally disable loading of all auto-loaded files.
21627 You may want to use this command with the @samp{-iex} option
21628 (@pxref{Option -init-eval-command}) such as:
21630 $ @kbd{gdb -iex "set auto-load off" untrusted-executable corefile}
21633 Be aware that system init file (@pxref{System-wide configuration})
21634 and init files from your home directory (@pxref{Home Directory Init File})
21635 still get read (as they come from generally trusted directories).
21636 To prevent @value{GDBN} from auto-loading even those init files, use the
21637 @option{-nx} option (@pxref{Mode Options}), in addition to
21638 @code{set auto-load no}.
21640 @anchor{show auto-load}
21641 @kindex show auto-load
21642 @item show auto-load
21643 Show whether auto-loading of each specific @samp{auto-load} file(s) is enabled
21647 (gdb) show auto-load
21648 gdb-scripts: Auto-loading of canned sequences of commands scripts is on.
21649 libthread-db: Auto-loading of inferior specific libthread_db is on.
21650 local-gdbinit: Auto-loading of .gdbinit script from current directory
21652 python-scripts: Auto-loading of Python scripts is on.
21653 safe-path: List of directories from which it is safe to auto-load files
21654 is $debugdir:$datadir/auto-load.
21655 scripts-directory: List of directories from which to load auto-loaded scripts
21656 is $debugdir:$datadir/auto-load.
21659 @anchor{info auto-load}
21660 @kindex info auto-load
21661 @item info auto-load
21662 Print whether each specific @samp{auto-load} file(s) have been auto-loaded or
21666 (gdb) info auto-load
21669 Yes /home/user/gdb/gdb-gdb.gdb
21670 libthread-db: No auto-loaded libthread-db.
21671 local-gdbinit: Local .gdbinit file "/home/user/gdb/.gdbinit" has been
21675 Yes /home/user/gdb/gdb-gdb.py
21679 These are various kinds of files @value{GDBN} can automatically load:
21683 @xref{objfile-gdb.py file}, controlled by @ref{set auto-load python-scripts}.
21685 @xref{objfile-gdb.gdb file}, controlled by @ref{set auto-load gdb-scripts}.
21687 @xref{dotdebug_gdb_scripts section},
21688 controlled by @ref{set auto-load python-scripts}.
21690 @xref{Init File in the Current Directory},
21691 controlled by @ref{set auto-load local-gdbinit}.
21693 @xref{libthread_db.so.1 file}, controlled by @ref{set auto-load libthread-db}.
21696 These are @value{GDBN} control commands for the auto-loading:
21698 @multitable @columnfractions .5 .5
21699 @item @xref{set auto-load off}.
21700 @tab Disable auto-loading globally.
21701 @item @xref{show auto-load}.
21702 @tab Show setting of all kinds of files.
21703 @item @xref{info auto-load}.
21704 @tab Show state of all kinds of files.
21705 @item @xref{set auto-load gdb-scripts}.
21706 @tab Control for @value{GDBN} command scripts.
21707 @item @xref{show auto-load gdb-scripts}.
21708 @tab Show setting of @value{GDBN} command scripts.
21709 @item @xref{info auto-load gdb-scripts}.
21710 @tab Show state of @value{GDBN} command scripts.
21711 @item @xref{set auto-load python-scripts}.
21712 @tab Control for @value{GDBN} Python scripts.
21713 @item @xref{show auto-load python-scripts}.
21714 @tab Show setting of @value{GDBN} Python scripts.
21715 @item @xref{info auto-load python-scripts}.
21716 @tab Show state of @value{GDBN} Python scripts.
21717 @item @xref{set auto-load scripts-directory}.
21718 @tab Control for @value{GDBN} auto-loaded scripts location.
21719 @item @xref{show auto-load scripts-directory}.
21720 @tab Show @value{GDBN} auto-loaded scripts location.
21721 @item @xref{set auto-load local-gdbinit}.
21722 @tab Control for init file in the current directory.
21723 @item @xref{show auto-load local-gdbinit}.
21724 @tab Show setting of init file in the current directory.
21725 @item @xref{info auto-load local-gdbinit}.
21726 @tab Show state of init file in the current directory.
21727 @item @xref{set auto-load libthread-db}.
21728 @tab Control for thread debugging library.
21729 @item @xref{show auto-load libthread-db}.
21730 @tab Show setting of thread debugging library.
21731 @item @xref{info auto-load libthread-db}.
21732 @tab Show state of thread debugging library.
21733 @item @xref{set auto-load safe-path}.
21734 @tab Control directories trusted for automatic loading.
21735 @item @xref{show auto-load safe-path}.
21736 @tab Show directories trusted for automatic loading.
21737 @item @xref{add-auto-load-safe-path}.
21738 @tab Add directory trusted for automatic loading.
21742 * Init File in the Current Directory:: @samp{set/show/info auto-load local-gdbinit}
21743 * libthread_db.so.1 file:: @samp{set/show/info auto-load libthread-db}
21744 * objfile-gdb.gdb file:: @samp{set/show/info auto-load gdb-script}
21745 * Auto-loading safe path:: @samp{set/show/info auto-load safe-path}
21746 * Auto-loading verbose mode:: @samp{set/show debug auto-load}
21747 @xref{Python Auto-loading}.
21750 @node Init File in the Current Directory
21751 @subsection Automatically loading init file in the current directory
21752 @cindex auto-loading init file in the current directory
21754 By default, @value{GDBN} reads and executes the canned sequences of commands
21755 from init file (if any) in the current working directory,
21756 see @ref{Init File in the Current Directory during Startup}.
21758 Note that loading of this local @file{.gdbinit} file also requires accordingly
21759 configured @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21762 @anchor{set auto-load local-gdbinit}
21763 @kindex set auto-load local-gdbinit
21764 @item set auto-load local-gdbinit [on|off]
21765 Enable or disable the auto-loading of canned sequences of commands
21766 (@pxref{Sequences}) found in init file in the current directory.
21768 @anchor{show auto-load local-gdbinit}
21769 @kindex show auto-load local-gdbinit
21770 @item show auto-load local-gdbinit
21771 Show whether auto-loading of canned sequences of commands from init file in the
21772 current directory is enabled or disabled.
21774 @anchor{info auto-load local-gdbinit}
21775 @kindex info auto-load local-gdbinit
21776 @item info auto-load local-gdbinit
21777 Print whether canned sequences of commands from init file in the
21778 current directory have been auto-loaded.
21781 @node libthread_db.so.1 file
21782 @subsection Automatically loading thread debugging library
21783 @cindex auto-loading libthread_db.so.1
21785 This feature is currently present only on @sc{gnu}/Linux native hosts.
21787 @value{GDBN} reads in some cases thread debugging library from places specific
21788 to the inferior (@pxref{set libthread-db-search-path}).
21790 The special @samp{libthread-db-search-path} entry @samp{$sdir} is processed
21791 without checking this @samp{set auto-load libthread-db} switch as system
21792 libraries have to be trusted in general. In all other cases of
21793 @samp{libthread-db-search-path} entries @value{GDBN} checks first if @samp{set
21794 auto-load libthread-db} is enabled before trying to open such thread debugging
21797 Note that loading of this debugging library also requires accordingly configured
21798 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21801 @anchor{set auto-load libthread-db}
21802 @kindex set auto-load libthread-db
21803 @item set auto-load libthread-db [on|off]
21804 Enable or disable the auto-loading of inferior specific thread debugging library.
21806 @anchor{show auto-load libthread-db}
21807 @kindex show auto-load libthread-db
21808 @item show auto-load libthread-db
21809 Show whether auto-loading of inferior specific thread debugging library is
21810 enabled or disabled.
21812 @anchor{info auto-load libthread-db}
21813 @kindex info auto-load libthread-db
21814 @item info auto-load libthread-db
21815 Print the list of all loaded inferior specific thread debugging libraries and
21816 for each such library print list of inferior @var{pid}s using it.
21819 @node objfile-gdb.gdb file
21820 @subsection The @file{@var{objfile}-gdb.gdb} file
21821 @cindex auto-loading @file{@var{objfile}-gdb.gdb}
21823 @value{GDBN} tries to load an @file{@var{objfile}-gdb.gdb} file containing
21824 canned sequences of commands (@pxref{Sequences}), as long as @samp{set
21825 auto-load gdb-scripts} is set to @samp{on}.
21827 Note that loading of this script file also requires accordingly configured
21828 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
21830 For more background refer to the similar Python scripts auto-loading
21831 description (@pxref{objfile-gdb.py file}).
21834 @anchor{set auto-load gdb-scripts}
21835 @kindex set auto-load gdb-scripts
21836 @item set auto-load gdb-scripts [on|off]
21837 Enable or disable the auto-loading of canned sequences of commands scripts.
21839 @anchor{show auto-load gdb-scripts}
21840 @kindex show auto-load gdb-scripts
21841 @item show auto-load gdb-scripts
21842 Show whether auto-loading of canned sequences of commands scripts is enabled or
21845 @anchor{info auto-load gdb-scripts}
21846 @kindex info auto-load gdb-scripts
21847 @cindex print list of auto-loaded canned sequences of commands scripts
21848 @item info auto-load gdb-scripts [@var{regexp}]
21849 Print the list of all canned sequences of commands scripts that @value{GDBN}
21853 If @var{regexp} is supplied only canned sequences of commands scripts with
21854 matching names are printed.
21856 @node Auto-loading safe path
21857 @subsection Security restriction for auto-loading
21858 @cindex auto-loading safe-path
21860 As the files of inferior can come from untrusted source (such as submitted by
21861 an application user) @value{GDBN} does not always load any files automatically.
21862 @value{GDBN} provides the @samp{set auto-load safe-path} setting to list
21863 directories trusted for loading files not explicitly requested by user.
21864 Each directory can also be a shell wildcard pattern.
21866 If the path is not set properly you will see a warning and the file will not
21871 Reading symbols from /home/user/gdb/gdb...done.
21872 warning: File "/home/user/gdb/gdb-gdb.gdb" auto-loading has been
21873 declined by your `auto-load safe-path' set
21874 to "$debugdir:$datadir/auto-load".
21875 warning: File "/home/user/gdb/gdb-gdb.py" auto-loading has been
21876 declined by your `auto-load safe-path' set
21877 to "$debugdir:$datadir/auto-load".
21880 The list of trusted directories is controlled by the following commands:
21883 @anchor{set auto-load safe-path}
21884 @kindex set auto-load safe-path
21885 @item set auto-load safe-path @r{[}@var{directories}@r{]}
21886 Set the list of directories (and their subdirectories) trusted for automatic
21887 loading and execution of scripts. You can also enter a specific trusted file.
21888 Each directory can also be a shell wildcard pattern; wildcards do not match
21889 directory separator - see @code{FNM_PATHNAME} for system function @code{fnmatch}
21890 (@pxref{Wildcard Matching, fnmatch, , libc, GNU C Library Reference Manual}).
21891 If you omit @var{directories}, @samp{auto-load safe-path} will be reset to
21892 its default value as specified during @value{GDBN} compilation.
21894 The list of directories uses path separator (@samp{:} on GNU and Unix
21895 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
21896 to the @env{PATH} environment variable.
21898 @anchor{show auto-load safe-path}
21899 @kindex show auto-load safe-path
21900 @item show auto-load safe-path
21901 Show the list of directories trusted for automatic loading and execution of
21904 @anchor{add-auto-load-safe-path}
21905 @kindex add-auto-load-safe-path
21906 @item add-auto-load-safe-path
21907 Add an entry (or list of entries) the list of directories trusted for automatic
21908 loading and execution of scripts. Multiple entries may be delimited by the
21909 host platform path separator in use.
21912 This variable defaults to what @code{--with-auto-load-dir} has been configured
21913 to (@pxref{with-auto-load-dir}). @file{$debugdir} and @file{$datadir}
21914 substitution applies the same as for @ref{set auto-load scripts-directory}.
21915 The default @code{set auto-load safe-path} value can be also overriden by
21916 @value{GDBN} configuration option @option{--with-auto-load-safe-path}.
21918 Setting this variable to @file{/} disables this security protection,
21919 corresponding @value{GDBN} configuration option is
21920 @option{--without-auto-load-safe-path}.
21921 This variable is supposed to be set to the system directories writable by the
21922 system superuser only. Users can add their source directories in init files in
21923 their home directories (@pxref{Home Directory Init File}). See also deprecated
21924 init file in the current directory
21925 (@pxref{Init File in the Current Directory during Startup}).
21927 To force @value{GDBN} to load the files it declined to load in the previous
21928 example, you could use one of the following ways:
21931 @item @file{~/.gdbinit}: @samp{add-auto-load-safe-path ~/src/gdb}
21932 Specify this trusted directory (or a file) as additional component of the list.
21933 You have to specify also any existing directories displayed by
21934 by @samp{show auto-load safe-path} (such as @samp{/usr:/bin} in this example).
21936 @item @kbd{gdb -iex "set auto-load safe-path /usr:/bin:~/src/gdb" @dots{}}
21937 Specify this directory as in the previous case but just for a single
21938 @value{GDBN} session.
21940 @item @kbd{gdb -iex "set auto-load safe-path /" @dots{}}
21941 Disable auto-loading safety for a single @value{GDBN} session.
21942 This assumes all the files you debug during this @value{GDBN} session will come
21943 from trusted sources.
21945 @item @kbd{./configure --without-auto-load-safe-path}
21946 During compilation of @value{GDBN} you may disable any auto-loading safety.
21947 This assumes all the files you will ever debug with this @value{GDBN} come from
21951 On the other hand you can also explicitly forbid automatic files loading which
21952 also suppresses any such warning messages:
21955 @item @kbd{gdb -iex "set auto-load no" @dots{}}
21956 You can use @value{GDBN} command-line option for a single @value{GDBN} session.
21958 @item @file{~/.gdbinit}: @samp{set auto-load no}
21959 Disable auto-loading globally for the user
21960 (@pxref{Home Directory Init File}). While it is improbable, you could also
21961 use system init file instead (@pxref{System-wide configuration}).
21964 This setting applies to the file names as entered by user. If no entry matches
21965 @value{GDBN} tries as a last resort to also resolve all the file names into
21966 their canonical form (typically resolving symbolic links) and compare the
21967 entries again. @value{GDBN} already canonicalizes most of the filenames on its
21968 own before starting the comparison so a canonical form of directories is
21969 recommended to be entered.
21971 @node Auto-loading verbose mode
21972 @subsection Displaying files tried for auto-load
21973 @cindex auto-loading verbose mode
21975 For better visibility of all the file locations where you can place scripts to
21976 be auto-loaded with inferior --- or to protect yourself against accidental
21977 execution of untrusted scripts --- @value{GDBN} provides a feature for printing
21978 all the files attempted to be loaded. Both existing and non-existing files may
21981 For example the list of directories from which it is safe to auto-load files
21982 (@pxref{Auto-loading safe path}) applies also to canonicalized filenames which
21983 may not be too obvious while setting it up.
21986 (gdb) set debug auto-load on
21987 (gdb) file ~/src/t/true
21988 auto-load: Loading canned sequences of commands script "/tmp/true-gdb.gdb"
21989 for objfile "/tmp/true".
21990 auto-load: Updating directories of "/usr:/opt".
21991 auto-load: Using directory "/usr".
21992 auto-load: Using directory "/opt".
21993 warning: File "/tmp/true-gdb.gdb" auto-loading has been declined
21994 by your `auto-load safe-path' set to "/usr:/opt".
21998 @anchor{set debug auto-load}
21999 @kindex set debug auto-load
22000 @item set debug auto-load [on|off]
22001 Set whether to print the filenames attempted to be auto-loaded.
22003 @anchor{show debug auto-load}
22004 @kindex show debug auto-load
22005 @item show debug auto-load
22006 Show whether printing of the filenames attempted to be auto-loaded is turned
22010 @node Messages/Warnings
22011 @section Optional Warnings and Messages
22013 @cindex verbose operation
22014 @cindex optional warnings
22015 By default, @value{GDBN} is silent about its inner workings. If you are
22016 running on a slow machine, you may want to use the @code{set verbose}
22017 command. This makes @value{GDBN} tell you when it does a lengthy
22018 internal operation, so you will not think it has crashed.
22020 Currently, the messages controlled by @code{set verbose} are those
22021 which announce that the symbol table for a source file is being read;
22022 see @code{symbol-file} in @ref{Files, ,Commands to Specify Files}.
22025 @kindex set verbose
22026 @item set verbose on
22027 Enables @value{GDBN} output of certain informational messages.
22029 @item set verbose off
22030 Disables @value{GDBN} output of certain informational messages.
22032 @kindex show verbose
22034 Displays whether @code{set verbose} is on or off.
22037 By default, if @value{GDBN} encounters bugs in the symbol table of an
22038 object file, it is silent; but if you are debugging a compiler, you may
22039 find this information useful (@pxref{Symbol Errors, ,Errors Reading
22044 @kindex set complaints
22045 @item set complaints @var{limit}
22046 Permits @value{GDBN} to output @var{limit} complaints about each type of
22047 unusual symbols before becoming silent about the problem. Set
22048 @var{limit} to zero to suppress all complaints; set it to a large number
22049 to prevent complaints from being suppressed.
22051 @kindex show complaints
22052 @item show complaints
22053 Displays how many symbol complaints @value{GDBN} is permitted to produce.
22057 @anchor{confirmation requests}
22058 By default, @value{GDBN} is cautious, and asks what sometimes seems to be a
22059 lot of stupid questions to confirm certain commands. For example, if
22060 you try to run a program which is already running:
22064 The program being debugged has been started already.
22065 Start it from the beginning? (y or n)
22068 If you are willing to unflinchingly face the consequences of your own
22069 commands, you can disable this ``feature'':
22073 @kindex set confirm
22075 @cindex confirmation
22076 @cindex stupid questions
22077 @item set confirm off
22078 Disables confirmation requests. Note that running @value{GDBN} with
22079 the @option{--batch} option (@pxref{Mode Options, -batch}) also
22080 automatically disables confirmation requests.
22082 @item set confirm on
22083 Enables confirmation requests (the default).
22085 @kindex show confirm
22087 Displays state of confirmation requests.
22091 @cindex command tracing
22092 If you need to debug user-defined commands or sourced files you may find it
22093 useful to enable @dfn{command tracing}. In this mode each command will be
22094 printed as it is executed, prefixed with one or more @samp{+} symbols, the
22095 quantity denoting the call depth of each command.
22098 @kindex set trace-commands
22099 @cindex command scripts, debugging
22100 @item set trace-commands on
22101 Enable command tracing.
22102 @item set trace-commands off
22103 Disable command tracing.
22104 @item show trace-commands
22105 Display the current state of command tracing.
22108 @node Debugging Output
22109 @section Optional Messages about Internal Happenings
22110 @cindex optional debugging messages
22112 @value{GDBN} has commands that enable optional debugging messages from
22113 various @value{GDBN} subsystems; normally these commands are of
22114 interest to @value{GDBN} maintainers, or when reporting a bug. This
22115 section documents those commands.
22118 @kindex set exec-done-display
22119 @item set exec-done-display
22120 Turns on or off the notification of asynchronous commands'
22121 completion. When on, @value{GDBN} will print a message when an
22122 asynchronous command finishes its execution. The default is off.
22123 @kindex show exec-done-display
22124 @item show exec-done-display
22125 Displays the current setting of asynchronous command completion
22128 @cindex gdbarch debugging info
22129 @cindex architecture debugging info
22130 @item set debug arch
22131 Turns on or off display of gdbarch debugging info. The default is off
22133 @item show debug arch
22134 Displays the current state of displaying gdbarch debugging info.
22135 @item set debug aix-thread
22136 @cindex AIX threads
22137 Display debugging messages about inner workings of the AIX thread
22139 @item show debug aix-thread
22140 Show the current state of AIX thread debugging info display.
22141 @item set debug check-physname
22143 Check the results of the ``physname'' computation. When reading DWARF
22144 debugging information for C@t{++}, @value{GDBN} attempts to compute
22145 each entity's name. @value{GDBN} can do this computation in two
22146 different ways, depending on exactly what information is present.
22147 When enabled, this setting causes @value{GDBN} to compute the names
22148 both ways and display any discrepancies.
22149 @item show debug check-physname
22150 Show the current state of ``physname'' checking.
22151 @item set debug dwarf2-die
22152 @cindex DWARF2 DIEs
22153 Dump DWARF2 DIEs after they are read in.
22154 The value is the number of nesting levels to print.
22155 A value of zero turns off the display.
22156 @item show debug dwarf2-die
22157 Show the current state of DWARF2 DIE debugging.
22158 @item set debug dwarf2-read
22159 @cindex DWARF2 Reading
22160 Turns on or off display of debugging messages related to reading
22161 DWARF debug info. The default is off.
22162 @item show debug dwarf2-read
22163 Show the current state of DWARF2 reader debugging.
22164 @item set debug displaced
22165 @cindex displaced stepping debugging info
22166 Turns on or off display of @value{GDBN} debugging info for the
22167 displaced stepping support. The default is off.
22168 @item show debug displaced
22169 Displays the current state of displaying @value{GDBN} debugging info
22170 related to displaced stepping.
22171 @item set debug event
22172 @cindex event debugging info
22173 Turns on or off display of @value{GDBN} event debugging info. The
22175 @item show debug event
22176 Displays the current state of displaying @value{GDBN} event debugging
22178 @item set debug expression
22179 @cindex expression debugging info
22180 Turns on or off display of debugging info about @value{GDBN}
22181 expression parsing. The default is off.
22182 @item show debug expression
22183 Displays the current state of displaying debugging info about
22184 @value{GDBN} expression parsing.
22185 @item set debug frame
22186 @cindex frame debugging info
22187 Turns on or off display of @value{GDBN} frame debugging info. The
22189 @item show debug frame
22190 Displays the current state of displaying @value{GDBN} frame debugging
22192 @item set debug gnu-nat
22193 @cindex @sc{gnu}/Hurd debug messages
22194 Turns on or off debugging messages from the @sc{gnu}/Hurd debug support.
22195 @item show debug gnu-nat
22196 Show the current state of @sc{gnu}/Hurd debugging messages.
22197 @item set debug infrun
22198 @cindex inferior debugging info
22199 Turns on or off display of @value{GDBN} debugging info for running the inferior.
22200 The default is off. @file{infrun.c} contains GDB's runtime state machine used
22201 for implementing operations such as single-stepping the inferior.
22202 @item show debug infrun
22203 Displays the current state of @value{GDBN} inferior debugging.
22204 @item set debug jit
22205 @cindex just-in-time compilation, debugging messages
22206 Turns on or off debugging messages from JIT debug support.
22207 @item show debug jit
22208 Displays the current state of @value{GDBN} JIT debugging.
22209 @item set debug lin-lwp
22210 @cindex @sc{gnu}/Linux LWP debug messages
22211 @cindex Linux lightweight processes
22212 Turns on or off debugging messages from the Linux LWP debug support.
22213 @item show debug lin-lwp
22214 Show the current state of Linux LWP debugging messages.
22215 @item set debug notification
22216 @cindex remote async notification debugging info
22217 Turns on or off debugging messages about remote async notification.
22218 The default is off.
22219 @item show debug notification
22220 Displays the current state of remote async notification debugging messages.
22221 @item set debug observer
22222 @cindex observer debugging info
22223 Turns on or off display of @value{GDBN} observer debugging. This
22224 includes info such as the notification of observable events.
22225 @item show debug observer
22226 Displays the current state of observer debugging.
22227 @item set debug overload
22228 @cindex C@t{++} overload debugging info
22229 Turns on or off display of @value{GDBN} C@t{++} overload debugging
22230 info. This includes info such as ranking of functions, etc. The default
22232 @item show debug overload
22233 Displays the current state of displaying @value{GDBN} C@t{++} overload
22235 @cindex expression parser, debugging info
22236 @cindex debug expression parser
22237 @item set debug parser
22238 Turns on or off the display of expression parser debugging output.
22239 Internally, this sets the @code{yydebug} variable in the expression
22240 parser. @xref{Tracing, , Tracing Your Parser, bison, Bison}, for
22241 details. The default is off.
22242 @item show debug parser
22243 Show the current state of expression parser debugging.
22244 @cindex packets, reporting on stdout
22245 @cindex serial connections, debugging
22246 @cindex debug remote protocol
22247 @cindex remote protocol debugging
22248 @cindex display remote packets
22249 @item set debug remote
22250 Turns on or off display of reports on all packets sent back and forth across
22251 the serial line to the remote machine. The info is printed on the
22252 @value{GDBN} standard output stream. The default is off.
22253 @item show debug remote
22254 Displays the state of display of remote packets.
22255 @item set debug serial
22256 Turns on or off display of @value{GDBN} serial debugging info. The
22258 @item show debug serial
22259 Displays the current state of displaying @value{GDBN} serial debugging
22261 @item set debug solib-frv
22262 @cindex FR-V shared-library debugging
22263 Turns on or off debugging messages for FR-V shared-library code.
22264 @item show debug solib-frv
22265 Display the current state of FR-V shared-library code debugging
22267 @item set debug symtab-create
22268 @cindex symbol table creation
22269 Turns on or off display of debugging messages related to symbol table creation.
22270 The default is off.
22271 @item show debug symtab-create
22272 Show the current state of symbol table creation debugging.
22273 @item set debug target
22274 @cindex target debugging info
22275 Turns on or off display of @value{GDBN} target debugging info. This info
22276 includes what is going on at the target level of GDB, as it happens. The
22277 default is 0. Set it to 1 to track events, and to 2 to also track the
22278 value of large memory transfers. Changes to this flag do not take effect
22279 until the next time you connect to a target or use the @code{run} command.
22280 @item show debug target
22281 Displays the current state of displaying @value{GDBN} target debugging
22283 @item set debug timestamp
22284 @cindex timestampping debugging info
22285 Turns on or off display of timestamps with @value{GDBN} debugging info.
22286 When enabled, seconds and microseconds are displayed before each debugging
22288 @item show debug timestamp
22289 Displays the current state of displaying timestamps with @value{GDBN}
22291 @item set debugvarobj
22292 @cindex variable object debugging info
22293 Turns on or off display of @value{GDBN} variable object debugging
22294 info. The default is off.
22295 @item show debugvarobj
22296 Displays the current state of displaying @value{GDBN} variable object
22298 @item set debug xml
22299 @cindex XML parser debugging
22300 Turns on or off debugging messages for built-in XML parsers.
22301 @item show debug xml
22302 Displays the current state of XML debugging messages.
22305 @node Other Misc Settings
22306 @section Other Miscellaneous Settings
22307 @cindex miscellaneous settings
22310 @kindex set interactive-mode
22311 @item set interactive-mode
22312 If @code{on}, forces @value{GDBN} to assume that GDB was started
22313 in a terminal. In practice, this means that @value{GDBN} should wait
22314 for the user to answer queries generated by commands entered at
22315 the command prompt. If @code{off}, forces @value{GDBN} to operate
22316 in the opposite mode, and it uses the default answers to all queries.
22317 If @code{auto} (the default), @value{GDBN} tries to determine whether
22318 its standard input is a terminal, and works in interactive-mode if it
22319 is, non-interactively otherwise.
22321 In the vast majority of cases, the debugger should be able to guess
22322 correctly which mode should be used. But this setting can be useful
22323 in certain specific cases, such as running a MinGW @value{GDBN}
22324 inside a cygwin window.
22326 @kindex show interactive-mode
22327 @item show interactive-mode
22328 Displays whether the debugger is operating in interactive mode or not.
22331 @node Extending GDB
22332 @chapter Extending @value{GDBN}
22333 @cindex extending GDB
22335 @value{GDBN} provides three mechanisms for extension. The first is based
22336 on composition of @value{GDBN} commands, the second is based on the
22337 Python scripting language, and the third is for defining new aliases of
22340 To facilitate the use of the first two extensions, @value{GDBN} is capable
22341 of evaluating the contents of a file. When doing so, @value{GDBN}
22342 can recognize which scripting language is being used by looking at
22343 the filename extension. Files with an unrecognized filename extension
22344 are always treated as a @value{GDBN} Command Files.
22345 @xref{Command Files,, Command files}.
22347 You can control how @value{GDBN} evaluates these files with the following
22351 @kindex set script-extension
22352 @kindex show script-extension
22353 @item set script-extension off
22354 All scripts are always evaluated as @value{GDBN} Command Files.
22356 @item set script-extension soft
22357 The debugger determines the scripting language based on filename
22358 extension. If this scripting language is supported, @value{GDBN}
22359 evaluates the script using that language. Otherwise, it evaluates
22360 the file as a @value{GDBN} Command File.
22362 @item set script-extension strict
22363 The debugger determines the scripting language based on filename
22364 extension, and evaluates the script using that language. If the
22365 language is not supported, then the evaluation fails.
22367 @item show script-extension
22368 Display the current value of the @code{script-extension} option.
22373 * Sequences:: Canned Sequences of Commands
22374 * Python:: Scripting @value{GDBN} using Python
22375 * Aliases:: Creating new spellings of existing commands
22379 @section Canned Sequences of Commands
22381 Aside from breakpoint commands (@pxref{Break Commands, ,Breakpoint
22382 Command Lists}), @value{GDBN} provides two ways to store sequences of
22383 commands for execution as a unit: user-defined commands and command
22387 * Define:: How to define your own commands
22388 * Hooks:: Hooks for user-defined commands
22389 * Command Files:: How to write scripts of commands to be stored in a file
22390 * Output:: Commands for controlled output
22394 @subsection User-defined Commands
22396 @cindex user-defined command
22397 @cindex arguments, to user-defined commands
22398 A @dfn{user-defined command} is a sequence of @value{GDBN} commands to
22399 which you assign a new name as a command. This is done with the
22400 @code{define} command. User commands may accept up to 10 arguments
22401 separated by whitespace. Arguments are accessed within the user command
22402 via @code{$arg0@dots{}$arg9}. A trivial example:
22406 print $arg0 + $arg1 + $arg2
22411 To execute the command use:
22418 This defines the command @code{adder}, which prints the sum of
22419 its three arguments. Note the arguments are text substitutions, so they may
22420 reference variables, use complex expressions, or even perform inferior
22423 @cindex argument count in user-defined commands
22424 @cindex how many arguments (user-defined commands)
22425 In addition, @code{$argc} may be used to find out how many arguments have
22426 been passed. This expands to a number in the range 0@dots{}10.
22431 print $arg0 + $arg1
22434 print $arg0 + $arg1 + $arg2
22442 @item define @var{commandname}
22443 Define a command named @var{commandname}. If there is already a command
22444 by that name, you are asked to confirm that you want to redefine it.
22445 @var{commandname} may be a bare command name consisting of letters,
22446 numbers, dashes, and underscores. It may also start with any predefined
22447 prefix command. For example, @samp{define target my-target} creates
22448 a user-defined @samp{target my-target} command.
22450 The definition of the command is made up of other @value{GDBN} command lines,
22451 which are given following the @code{define} command. The end of these
22452 commands is marked by a line containing @code{end}.
22455 @kindex end@r{ (user-defined commands)}
22456 @item document @var{commandname}
22457 Document the user-defined command @var{commandname}, so that it can be
22458 accessed by @code{help}. The command @var{commandname} must already be
22459 defined. This command reads lines of documentation just as @code{define}
22460 reads the lines of the command definition, ending with @code{end}.
22461 After the @code{document} command is finished, @code{help} on command
22462 @var{commandname} displays the documentation you have written.
22464 You may use the @code{document} command again to change the
22465 documentation of a command. Redefining the command with @code{define}
22466 does not change the documentation.
22468 @kindex dont-repeat
22469 @cindex don't repeat command
22471 Used inside a user-defined command, this tells @value{GDBN} that this
22472 command should not be repeated when the user hits @key{RET}
22473 (@pxref{Command Syntax, repeat last command}).
22475 @kindex help user-defined
22476 @item help user-defined
22477 List all user-defined commands and all python commands defined in class
22478 COMAND_USER. The first line of the documentation or docstring is
22483 @itemx show user @var{commandname}
22484 Display the @value{GDBN} commands used to define @var{commandname} (but
22485 not its documentation). If no @var{commandname} is given, display the
22486 definitions for all user-defined commands.
22487 This does not work for user-defined python commands.
22489 @cindex infinite recursion in user-defined commands
22490 @kindex show max-user-call-depth
22491 @kindex set max-user-call-depth
22492 @item show max-user-call-depth
22493 @itemx set max-user-call-depth
22494 The value of @code{max-user-call-depth} controls how many recursion
22495 levels are allowed in user-defined commands before @value{GDBN} suspects an
22496 infinite recursion and aborts the command.
22497 This does not apply to user-defined python commands.
22500 In addition to the above commands, user-defined commands frequently
22501 use control flow commands, described in @ref{Command Files}.
22503 When user-defined commands are executed, the
22504 commands of the definition are not printed. An error in any command
22505 stops execution of the user-defined command.
22507 If used interactively, commands that would ask for confirmation proceed
22508 without asking when used inside a user-defined command. Many @value{GDBN}
22509 commands that normally print messages to say what they are doing omit the
22510 messages when used in a user-defined command.
22513 @subsection User-defined Command Hooks
22514 @cindex command hooks
22515 @cindex hooks, for commands
22516 @cindex hooks, pre-command
22519 You may define @dfn{hooks}, which are a special kind of user-defined
22520 command. Whenever you run the command @samp{foo}, if the user-defined
22521 command @samp{hook-foo} exists, it is executed (with no arguments)
22522 before that command.
22524 @cindex hooks, post-command
22526 A hook may also be defined which is run after the command you executed.
22527 Whenever you run the command @samp{foo}, if the user-defined command
22528 @samp{hookpost-foo} exists, it is executed (with no arguments) after
22529 that command. Post-execution hooks may exist simultaneously with
22530 pre-execution hooks, for the same command.
22532 It is valid for a hook to call the command which it hooks. If this
22533 occurs, the hook is not re-executed, thereby avoiding infinite recursion.
22535 @c It would be nice if hookpost could be passed a parameter indicating
22536 @c if the command it hooks executed properly or not. FIXME!
22538 @kindex stop@r{, a pseudo-command}
22539 In addition, a pseudo-command, @samp{stop} exists. Defining
22540 (@samp{hook-stop}) makes the associated commands execute every time
22541 execution stops in your program: before breakpoint commands are run,
22542 displays are printed, or the stack frame is printed.
22544 For example, to ignore @code{SIGALRM} signals while
22545 single-stepping, but treat them normally during normal execution,
22550 handle SIGALRM nopass
22554 handle SIGALRM pass
22557 define hook-continue
22558 handle SIGALRM pass
22562 As a further example, to hook at the beginning and end of the @code{echo}
22563 command, and to add extra text to the beginning and end of the message,
22571 define hookpost-echo
22575 (@value{GDBP}) echo Hello World
22576 <<<---Hello World--->>>
22581 You can define a hook for any single-word command in @value{GDBN}, but
22582 not for command aliases; you should define a hook for the basic command
22583 name, e.g.@: @code{backtrace} rather than @code{bt}.
22584 @c FIXME! So how does Joe User discover whether a command is an alias
22586 You can hook a multi-word command by adding @code{hook-} or
22587 @code{hookpost-} to the last word of the command, e.g.@:
22588 @samp{define target hook-remote} to add a hook to @samp{target remote}.
22590 If an error occurs during the execution of your hook, execution of
22591 @value{GDBN} commands stops and @value{GDBN} issues a prompt
22592 (before the command that you actually typed had a chance to run).
22594 If you try to define a hook which does not match any known command, you
22595 get a warning from the @code{define} command.
22597 @node Command Files
22598 @subsection Command Files
22600 @cindex command files
22601 @cindex scripting commands
22602 A command file for @value{GDBN} is a text file made of lines that are
22603 @value{GDBN} commands. Comments (lines starting with @kbd{#}) may
22604 also be included. An empty line in a command file does nothing; it
22605 does not mean to repeat the last command, as it would from the
22608 You can request the execution of a command file with the @code{source}
22609 command. Note that the @code{source} command is also used to evaluate
22610 scripts that are not Command Files. The exact behavior can be configured
22611 using the @code{script-extension} setting.
22612 @xref{Extending GDB,, Extending GDB}.
22616 @cindex execute commands from a file
22617 @item source [-s] [-v] @var{filename}
22618 Execute the command file @var{filename}.
22621 The lines in a command file are generally executed sequentially,
22622 unless the order of execution is changed by one of the
22623 @emph{flow-control commands} described below. The commands are not
22624 printed as they are executed. An error in any command terminates
22625 execution of the command file and control is returned to the console.
22627 @value{GDBN} first searches for @var{filename} in the current directory.
22628 If the file is not found there, and @var{filename} does not specify a
22629 directory, then @value{GDBN} also looks for the file on the source search path
22630 (specified with the @samp{directory} command);
22631 except that @file{$cdir} is not searched because the compilation directory
22632 is not relevant to scripts.
22634 If @code{-s} is specified, then @value{GDBN} searches for @var{filename}
22635 on the search path even if @var{filename} specifies a directory.
22636 The search is done by appending @var{filename} to each element of the
22637 search path. So, for example, if @var{filename} is @file{mylib/myscript}
22638 and the search path contains @file{/home/user} then @value{GDBN} will
22639 look for the script @file{/home/user/mylib/myscript}.
22640 The search is also done if @var{filename} is an absolute path.
22641 For example, if @var{filename} is @file{/tmp/myscript} and
22642 the search path contains @file{/home/user} then @value{GDBN} will
22643 look for the script @file{/home/user/tmp/myscript}.
22644 For DOS-like systems, if @var{filename} contains a drive specification,
22645 it is stripped before concatenation. For example, if @var{filename} is
22646 @file{d:myscript} and the search path contains @file{c:/tmp} then @value{GDBN}
22647 will look for the script @file{c:/tmp/myscript}.
22649 If @code{-v}, for verbose mode, is given then @value{GDBN} displays
22650 each command as it is executed. The option must be given before
22651 @var{filename}, and is interpreted as part of the filename anywhere else.
22653 Commands that would ask for confirmation if used interactively proceed
22654 without asking when used in a command file. Many @value{GDBN} commands that
22655 normally print messages to say what they are doing omit the messages
22656 when called from command files.
22658 @value{GDBN} also accepts command input from standard input. In this
22659 mode, normal output goes to standard output and error output goes to
22660 standard error. Errors in a command file supplied on standard input do
22661 not terminate execution of the command file---execution continues with
22665 gdb < cmds > log 2>&1
22668 (The syntax above will vary depending on the shell used.) This example
22669 will execute commands from the file @file{cmds}. All output and errors
22670 would be directed to @file{log}.
22672 Since commands stored on command files tend to be more general than
22673 commands typed interactively, they frequently need to deal with
22674 complicated situations, such as different or unexpected values of
22675 variables and symbols, changes in how the program being debugged is
22676 built, etc. @value{GDBN} provides a set of flow-control commands to
22677 deal with these complexities. Using these commands, you can write
22678 complex scripts that loop over data structures, execute commands
22679 conditionally, etc.
22686 This command allows to include in your script conditionally executed
22687 commands. The @code{if} command takes a single argument, which is an
22688 expression to evaluate. It is followed by a series of commands that
22689 are executed only if the expression is true (its value is nonzero).
22690 There can then optionally be an @code{else} line, followed by a series
22691 of commands that are only executed if the expression was false. The
22692 end of the list is marked by a line containing @code{end}.
22696 This command allows to write loops. Its syntax is similar to
22697 @code{if}: the command takes a single argument, which is an expression
22698 to evaluate, and must be followed by the commands to execute, one per
22699 line, terminated by an @code{end}. These commands are called the
22700 @dfn{body} of the loop. The commands in the body of @code{while} are
22701 executed repeatedly as long as the expression evaluates to true.
22705 This command exits the @code{while} loop in whose body it is included.
22706 Execution of the script continues after that @code{while}s @code{end}
22709 @kindex loop_continue
22710 @item loop_continue
22711 This command skips the execution of the rest of the body of commands
22712 in the @code{while} loop in whose body it is included. Execution
22713 branches to the beginning of the @code{while} loop, where it evaluates
22714 the controlling expression.
22716 @kindex end@r{ (if/else/while commands)}
22718 Terminate the block of commands that are the body of @code{if},
22719 @code{else}, or @code{while} flow-control commands.
22724 @subsection Commands for Controlled Output
22726 During the execution of a command file or a user-defined command, normal
22727 @value{GDBN} output is suppressed; the only output that appears is what is
22728 explicitly printed by the commands in the definition. This section
22729 describes three commands useful for generating exactly the output you
22734 @item echo @var{text}
22735 @c I do not consider backslash-space a standard C escape sequence
22736 @c because it is not in ANSI.
22737 Print @var{text}. Nonprinting characters can be included in
22738 @var{text} using C escape sequences, such as @samp{\n} to print a
22739 newline. @strong{No newline is printed unless you specify one.}
22740 In addition to the standard C escape sequences, a backslash followed
22741 by a space stands for a space. This is useful for displaying a
22742 string with spaces at the beginning or the end, since leading and
22743 trailing spaces are otherwise trimmed from all arguments.
22744 To print @samp{@w{ }and foo =@w{ }}, use the command
22745 @samp{echo \@w{ }and foo = \@w{ }}.
22747 A backslash at the end of @var{text} can be used, as in C, to continue
22748 the command onto subsequent lines. For example,
22751 echo This is some text\n\
22752 which is continued\n\
22753 onto several lines.\n
22756 produces the same output as
22759 echo This is some text\n
22760 echo which is continued\n
22761 echo onto several lines.\n
22765 @item output @var{expression}
22766 Print the value of @var{expression} and nothing but that value: no
22767 newlines, no @samp{$@var{nn} = }. The value is not entered in the
22768 value history either. @xref{Expressions, ,Expressions}, for more information
22771 @item output/@var{fmt} @var{expression}
22772 Print the value of @var{expression} in format @var{fmt}. You can use
22773 the same formats as for @code{print}. @xref{Output Formats,,Output
22774 Formats}, for more information.
22777 @item printf @var{template}, @var{expressions}@dots{}
22778 Print the values of one or more @var{expressions} under the control of
22779 the string @var{template}. To print several values, make
22780 @var{expressions} be a comma-separated list of individual expressions,
22781 which may be either numbers or pointers. Their values are printed as
22782 specified by @var{template}, exactly as a C program would do by
22783 executing the code below:
22786 printf (@var{template}, @var{expressions}@dots{});
22789 As in @code{C} @code{printf}, ordinary characters in @var{template}
22790 are printed verbatim, while @dfn{conversion specification} introduced
22791 by the @samp{%} character cause subsequent @var{expressions} to be
22792 evaluated, their values converted and formatted according to type and
22793 style information encoded in the conversion specifications, and then
22796 For example, you can print two values in hex like this:
22799 printf "foo, bar-foo = 0x%x, 0x%x\n", foo, bar-foo
22802 @code{printf} supports all the standard @code{C} conversion
22803 specifications, including the flags and modifiers between the @samp{%}
22804 character and the conversion letter, with the following exceptions:
22808 The argument-ordering modifiers, such as @samp{2$}, are not supported.
22811 The modifier @samp{*} is not supported for specifying precision or
22815 The @samp{'} flag (for separation of digits into groups according to
22816 @code{LC_NUMERIC'}) is not supported.
22819 The type modifiers @samp{hh}, @samp{j}, @samp{t}, and @samp{z} are not
22823 The conversion letter @samp{n} (as in @samp{%n}) is not supported.
22826 The conversion letters @samp{a} and @samp{A} are not supported.
22830 Note that the @samp{ll} type modifier is supported only if the
22831 underlying @code{C} implementation used to build @value{GDBN} supports
22832 the @code{long long int} type, and the @samp{L} type modifier is
22833 supported only if @code{long double} type is available.
22835 As in @code{C}, @code{printf} supports simple backslash-escape
22836 sequences, such as @code{\n}, @samp{\t}, @samp{\\}, @samp{\"},
22837 @samp{\a}, and @samp{\f}, that consist of backslash followed by a
22838 single character. Octal and hexadecimal escape sequences are not
22841 Additionally, @code{printf} supports conversion specifications for DFP
22842 (@dfn{Decimal Floating Point}) types using the following length modifiers
22843 together with a floating point specifier.
22848 @samp{H} for printing @code{Decimal32} types.
22851 @samp{D} for printing @code{Decimal64} types.
22854 @samp{DD} for printing @code{Decimal128} types.
22857 If the underlying @code{C} implementation used to build @value{GDBN} has
22858 support for the three length modifiers for DFP types, other modifiers
22859 such as width and precision will also be available for @value{GDBN} to use.
22861 In case there is no such @code{C} support, no additional modifiers will be
22862 available and the value will be printed in the standard way.
22864 Here's an example of printing DFP types using the above conversion letters:
22866 printf "D32: %Hf - D64: %Df - D128: %DDf\n",1.2345df,1.2E10dd,1.2E1dl
22870 @item eval @var{template}, @var{expressions}@dots{}
22871 Convert the values of one or more @var{expressions} under the control of
22872 the string @var{template} to a command line, and call it.
22877 @section Scripting @value{GDBN} using Python
22878 @cindex python scripting
22879 @cindex scripting with python
22881 You can script @value{GDBN} using the @uref{http://www.python.org/,
22882 Python programming language}. This feature is available only if
22883 @value{GDBN} was configured using @option{--with-python}.
22885 @cindex python directory
22886 Python scripts used by @value{GDBN} should be installed in
22887 @file{@var{data-directory}/python}, where @var{data-directory} is
22888 the data directory as determined at @value{GDBN} startup (@pxref{Data Files}).
22889 This directory, known as the @dfn{python directory},
22890 is automatically added to the Python Search Path in order to allow
22891 the Python interpreter to locate all scripts installed at this location.
22893 Additionally, @value{GDBN} commands and convenience functions which
22894 are written in Python and are located in the
22895 @file{@var{data-directory}/python/gdb/command} or
22896 @file{@var{data-directory}/python/gdb/function} directories are
22897 automatically imported when @value{GDBN} starts.
22900 * Python Commands:: Accessing Python from @value{GDBN}.
22901 * Python API:: Accessing @value{GDBN} from Python.
22902 * Python Auto-loading:: Automatically loading Python code.
22903 * Python modules:: Python modules provided by @value{GDBN}.
22906 @node Python Commands
22907 @subsection Python Commands
22908 @cindex python commands
22909 @cindex commands to access python
22911 @value{GDBN} provides two commands for accessing the Python interpreter,
22912 and one related setting:
22915 @kindex python-interactive
22917 @item python-interactive @r{[}@var{command}@r{]}
22918 @itemx pi @r{[}@var{command}@r{]}
22919 Without an argument, the @code{python-interactive} command can be used
22920 to start an interactive Python prompt. To return to @value{GDBN},
22921 type the @code{EOF} character (e.g., @kbd{Ctrl-D} on an empty prompt).
22923 Alternatively, a single-line Python command can be given as an
22924 argument and evaluated. If the command is an expression, the result
22925 will be printed; otherwise, nothing will be printed. For example:
22928 (@value{GDBP}) python-interactive 2 + 3
22934 @item python @r{[}@var{command}@r{]}
22935 @itemx py @r{[}@var{command}@r{]}
22936 The @code{python} command can be used to evaluate Python code.
22938 If given an argument, the @code{python} command will evaluate the
22939 argument as a Python command. For example:
22942 (@value{GDBP}) python print 23
22946 If you do not provide an argument to @code{python}, it will act as a
22947 multi-line command, like @code{define}. In this case, the Python
22948 script is made up of subsequent command lines, given after the
22949 @code{python} command. This command list is terminated using a line
22950 containing @code{end}. For example:
22953 (@value{GDBP}) python
22955 End with a line saying just "end".
22961 @kindex set python print-stack
22962 @item set python print-stack
22963 By default, @value{GDBN} will print only the message component of a
22964 Python exception when an error occurs in a Python script. This can be
22965 controlled using @code{set python print-stack}: if @code{full}, then
22966 full Python stack printing is enabled; if @code{none}, then Python stack
22967 and message printing is disabled; if @code{message}, the default, only
22968 the message component of the error is printed.
22971 It is also possible to execute a Python script from the @value{GDBN}
22975 @item source @file{script-name}
22976 The script name must end with @samp{.py} and @value{GDBN} must be configured
22977 to recognize the script language based on filename extension using
22978 the @code{script-extension} setting. @xref{Extending GDB, ,Extending GDB}.
22980 @item python execfile ("script-name")
22981 This method is based on the @code{execfile} Python built-in function,
22982 and thus is always available.
22986 @subsection Python API
22988 @cindex programming in python
22990 @cindex python stdout
22991 @cindex python pagination
22992 At startup, @value{GDBN} overrides Python's @code{sys.stdout} and
22993 @code{sys.stderr} to print using @value{GDBN}'s output-paging streams.
22994 A Python program which outputs to one of these streams may have its
22995 output interrupted by the user (@pxref{Screen Size}). In this
22996 situation, a Python @code{KeyboardInterrupt} exception is thrown.
22999 * Basic Python:: Basic Python Functions.
23000 * Exception Handling:: How Python exceptions are translated.
23001 * Values From Inferior:: Python representation of values.
23002 * Types In Python:: Python representation of types.
23003 * Pretty Printing API:: Pretty-printing values.
23004 * Selecting Pretty-Printers:: How GDB chooses a pretty-printer.
23005 * Writing a Pretty-Printer:: Writing a Pretty-Printer.
23006 * Type Printing API:: Pretty-printing types.
23007 * Inferiors In Python:: Python representation of inferiors (processes)
23008 * Events In Python:: Listening for events from @value{GDBN}.
23009 * Threads In Python:: Accessing inferior threads from Python.
23010 * Commands In Python:: Implementing new commands in Python.
23011 * Parameters In Python:: Adding new @value{GDBN} parameters.
23012 * Functions In Python:: Writing new convenience functions.
23013 * Progspaces In Python:: Program spaces.
23014 * Objfiles In Python:: Object files.
23015 * Frames In Python:: Accessing inferior stack frames from Python.
23016 * Blocks In Python:: Accessing frame blocks from Python.
23017 * Symbols In Python:: Python representation of symbols.
23018 * Symbol Tables In Python:: Python representation of symbol tables.
23019 * Breakpoints In Python:: Manipulating breakpoints using Python.
23020 * Finish Breakpoints in Python:: Setting Breakpoints on function return
23022 * Lazy Strings In Python:: Python representation of lazy strings.
23023 * Architectures In Python:: Python representation of architectures.
23027 @subsubsection Basic Python
23029 @cindex python functions
23030 @cindex python module
23032 @value{GDBN} introduces a new Python module, named @code{gdb}. All
23033 methods and classes added by @value{GDBN} are placed in this module.
23034 @value{GDBN} automatically @code{import}s the @code{gdb} module for
23035 use in all scripts evaluated by the @code{python} command.
23037 @findex gdb.PYTHONDIR
23038 @defvar gdb.PYTHONDIR
23039 A string containing the python directory (@pxref{Python}).
23042 @findex gdb.execute
23043 @defun gdb.execute (command @r{[}, from_tty @r{[}, to_string@r{]]})
23044 Evaluate @var{command}, a string, as a @value{GDBN} CLI command.
23045 If a GDB exception happens while @var{command} runs, it is
23046 translated as described in @ref{Exception Handling,,Exception Handling}.
23048 @var{from_tty} specifies whether @value{GDBN} ought to consider this
23049 command as having originated from the user invoking it interactively.
23050 It must be a boolean value. If omitted, it defaults to @code{False}.
23052 By default, any output produced by @var{command} is sent to
23053 @value{GDBN}'s standard output. If the @var{to_string} parameter is
23054 @code{True}, then output will be collected by @code{gdb.execute} and
23055 returned as a string. The default is @code{False}, in which case the
23056 return value is @code{None}. If @var{to_string} is @code{True}, the
23057 @value{GDBN} virtual terminal will be temporarily set to unlimited width
23058 and height, and its pagination will be disabled; @pxref{Screen Size}.
23061 @findex gdb.breakpoints
23062 @defun gdb.breakpoints ()
23063 Return a sequence holding all of @value{GDBN}'s breakpoints.
23064 @xref{Breakpoints In Python}, for more information.
23067 @findex gdb.parameter
23068 @defun gdb.parameter (parameter)
23069 Return the value of a @value{GDBN} parameter. @var{parameter} is a
23070 string naming the parameter to look up; @var{parameter} may contain
23071 spaces if the parameter has a multi-part name. For example,
23072 @samp{print object} is a valid parameter name.
23074 If the named parameter does not exist, this function throws a
23075 @code{gdb.error} (@pxref{Exception Handling}). Otherwise, the
23076 parameter's value is converted to a Python value of the appropriate
23077 type, and returned.
23080 @findex gdb.history
23081 @defun gdb.history (number)
23082 Return a value from @value{GDBN}'s value history (@pxref{Value
23083 History}). @var{number} indicates which history element to return.
23084 If @var{number} is negative, then @value{GDBN} will take its absolute value
23085 and count backward from the last element (i.e., the most recent element) to
23086 find the value to return. If @var{number} is zero, then @value{GDBN} will
23087 return the most recent element. If the element specified by @var{number}
23088 doesn't exist in the value history, a @code{gdb.error} exception will be
23091 If no exception is raised, the return value is always an instance of
23092 @code{gdb.Value} (@pxref{Values From Inferior}).
23095 @findex gdb.parse_and_eval
23096 @defun gdb.parse_and_eval (expression)
23097 Parse @var{expression} as an expression in the current language,
23098 evaluate it, and return the result as a @code{gdb.Value}.
23099 @var{expression} must be a string.
23101 This function can be useful when implementing a new command
23102 (@pxref{Commands In Python}), as it provides a way to parse the
23103 command's argument as an expression. It is also useful simply to
23104 compute values, for example, it is the only way to get the value of a
23105 convenience variable (@pxref{Convenience Vars}) as a @code{gdb.Value}.
23108 @findex gdb.find_pc_line
23109 @defun gdb.find_pc_line (pc)
23110 Return the @code{gdb.Symtab_and_line} object corresponding to the
23111 @var{pc} value. @xref{Symbol Tables In Python}. If an invalid
23112 value of @var{pc} is passed as an argument, then the @code{symtab} and
23113 @code{line} attributes of the returned @code{gdb.Symtab_and_line} object
23114 will be @code{None} and 0 respectively.
23117 @findex gdb.post_event
23118 @defun gdb.post_event (event)
23119 Put @var{event}, a callable object taking no arguments, into
23120 @value{GDBN}'s internal event queue. This callable will be invoked at
23121 some later point, during @value{GDBN}'s event processing. Events
23122 posted using @code{post_event} will be run in the order in which they
23123 were posted; however, there is no way to know when they will be
23124 processed relative to other events inside @value{GDBN}.
23126 @value{GDBN} is not thread-safe. If your Python program uses multiple
23127 threads, you must be careful to only call @value{GDBN}-specific
23128 functions in the main @value{GDBN} thread. @code{post_event} ensures
23132 (@value{GDBP}) python
23136 > def __init__(self, message):
23137 > self.message = message;
23138 > def __call__(self):
23139 > gdb.write(self.message)
23141 >class MyThread1 (threading.Thread):
23143 > gdb.post_event(Writer("Hello "))
23145 >class MyThread2 (threading.Thread):
23147 > gdb.post_event(Writer("World\n"))
23149 >MyThread1().start()
23150 >MyThread2().start()
23152 (@value{GDBP}) Hello World
23157 @defun gdb.write (string @r{[}, stream{]})
23158 Print a string to @value{GDBN}'s paginated output stream. The
23159 optional @var{stream} determines the stream to print to. The default
23160 stream is @value{GDBN}'s standard output stream. Possible stream
23167 @value{GDBN}'s standard output stream.
23172 @value{GDBN}'s standard error stream.
23177 @value{GDBN}'s log stream (@pxref{Logging Output}).
23180 Writing to @code{sys.stdout} or @code{sys.stderr} will automatically
23181 call this function and will automatically direct the output to the
23186 @defun gdb.flush ()
23187 Flush the buffer of a @value{GDBN} paginated stream so that the
23188 contents are displayed immediately. @value{GDBN} will flush the
23189 contents of a stream automatically when it encounters a newline in the
23190 buffer. The optional @var{stream} determines the stream to flush. The
23191 default stream is @value{GDBN}'s standard output stream. Possible
23198 @value{GDBN}'s standard output stream.
23203 @value{GDBN}'s standard error stream.
23208 @value{GDBN}'s log stream (@pxref{Logging Output}).
23212 Flushing @code{sys.stdout} or @code{sys.stderr} will automatically
23213 call this function for the relevant stream.
23216 @findex gdb.target_charset
23217 @defun gdb.target_charset ()
23218 Return the name of the current target character set (@pxref{Character
23219 Sets}). This differs from @code{gdb.parameter('target-charset')} in
23220 that @samp{auto} is never returned.
23223 @findex gdb.target_wide_charset
23224 @defun gdb.target_wide_charset ()
23225 Return the name of the current target wide character set
23226 (@pxref{Character Sets}). This differs from
23227 @code{gdb.parameter('target-wide-charset')} in that @samp{auto} is
23231 @findex gdb.solib_name
23232 @defun gdb.solib_name (address)
23233 Return the name of the shared library holding the given @var{address}
23234 as a string, or @code{None}.
23237 @findex gdb.decode_line
23238 @defun gdb.decode_line @r{[}expression@r{]}
23239 Return locations of the line specified by @var{expression}, or of the
23240 current line if no argument was given. This function returns a Python
23241 tuple containing two elements. The first element contains a string
23242 holding any unparsed section of @var{expression} (or @code{None} if
23243 the expression has been fully parsed). The second element contains
23244 either @code{None} or another tuple that contains all the locations
23245 that match the expression represented as @code{gdb.Symtab_and_line}
23246 objects (@pxref{Symbol Tables In Python}). If @var{expression} is
23247 provided, it is decoded the way that @value{GDBN}'s inbuilt
23248 @code{break} or @code{edit} commands do (@pxref{Specify Location}).
23251 @defun gdb.prompt_hook (current_prompt)
23252 @anchor{prompt_hook}
23254 If @var{prompt_hook} is callable, @value{GDBN} will call the method
23255 assigned to this operation before a prompt is displayed by
23258 The parameter @code{current_prompt} contains the current @value{GDBN}
23259 prompt. This method must return a Python string, or @code{None}. If
23260 a string is returned, the @value{GDBN} prompt will be set to that
23261 string. If @code{None} is returned, @value{GDBN} will continue to use
23262 the current prompt.
23264 Some prompts cannot be substituted in @value{GDBN}. Secondary prompts
23265 such as those used by readline for command input, and annotation
23266 related prompts are prohibited from being changed.
23269 @node Exception Handling
23270 @subsubsection Exception Handling
23271 @cindex python exceptions
23272 @cindex exceptions, python
23274 When executing the @code{python} command, Python exceptions
23275 uncaught within the Python code are translated to calls to
23276 @value{GDBN} error-reporting mechanism. If the command that called
23277 @code{python} does not handle the error, @value{GDBN} will
23278 terminate it and print an error message containing the Python
23279 exception name, the associated value, and the Python call stack
23280 backtrace at the point where the exception was raised. Example:
23283 (@value{GDBP}) python print foo
23284 Traceback (most recent call last):
23285 File "<string>", line 1, in <module>
23286 NameError: name 'foo' is not defined
23289 @value{GDBN} errors that happen in @value{GDBN} commands invoked by
23290 Python code are converted to Python exceptions. The type of the
23291 Python exception depends on the error.
23295 This is the base class for most exceptions generated by @value{GDBN}.
23296 It is derived from @code{RuntimeError}, for compatibility with earlier
23297 versions of @value{GDBN}.
23299 If an error occurring in @value{GDBN} does not fit into some more
23300 specific category, then the generated exception will have this type.
23302 @item gdb.MemoryError
23303 This is a subclass of @code{gdb.error} which is thrown when an
23304 operation tried to access invalid memory in the inferior.
23306 @item KeyboardInterrupt
23307 User interrupt (via @kbd{C-c} or by typing @kbd{q} at a pagination
23308 prompt) is translated to a Python @code{KeyboardInterrupt} exception.
23311 In all cases, your exception handler will see the @value{GDBN} error
23312 message as its value and the Python call stack backtrace at the Python
23313 statement closest to where the @value{GDBN} error occured as the
23316 @findex gdb.GdbError
23317 When implementing @value{GDBN} commands in Python via @code{gdb.Command},
23318 it is useful to be able to throw an exception that doesn't cause a
23319 traceback to be printed. For example, the user may have invoked the
23320 command incorrectly. Use the @code{gdb.GdbError} exception
23321 to handle this case. Example:
23325 >class HelloWorld (gdb.Command):
23326 > """Greet the whole world."""
23327 > def __init__ (self):
23328 > super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
23329 > def invoke (self, args, from_tty):
23330 > argv = gdb.string_to_argv (args)
23331 > if len (argv) != 0:
23332 > raise gdb.GdbError ("hello-world takes no arguments")
23333 > print "Hello, World!"
23336 (gdb) hello-world 42
23337 hello-world takes no arguments
23340 @node Values From Inferior
23341 @subsubsection Values From Inferior
23342 @cindex values from inferior, with Python
23343 @cindex python, working with values from inferior
23345 @cindex @code{gdb.Value}
23346 @value{GDBN} provides values it obtains from the inferior program in
23347 an object of type @code{gdb.Value}. @value{GDBN} uses this object
23348 for its internal bookkeeping of the inferior's values, and for
23349 fetching values when necessary.
23351 Inferior values that are simple scalars can be used directly in
23352 Python expressions that are valid for the value's data type. Here's
23353 an example for an integer or floating-point value @code{some_val}:
23360 As result of this, @code{bar} will also be a @code{gdb.Value} object
23361 whose values are of the same type as those of @code{some_val}.
23363 Inferior values that are structures or instances of some class can
23364 be accessed using the Python @dfn{dictionary syntax}. For example, if
23365 @code{some_val} is a @code{gdb.Value} instance holding a structure, you
23366 can access its @code{foo} element with:
23369 bar = some_val['foo']
23372 Again, @code{bar} will also be a @code{gdb.Value} object.
23374 A @code{gdb.Value} that represents a function can be executed via
23375 inferior function call. Any arguments provided to the call must match
23376 the function's prototype, and must be provided in the order specified
23379 For example, @code{some_val} is a @code{gdb.Value} instance
23380 representing a function that takes two integers as arguments. To
23381 execute this function, call it like so:
23384 result = some_val (10,20)
23387 Any values returned from a function call will be stored as a
23390 The following attributes are provided:
23392 @defvar Value.address
23393 If this object is addressable, this read-only attribute holds a
23394 @code{gdb.Value} object representing the address. Otherwise,
23395 this attribute holds @code{None}.
23398 @cindex optimized out value in Python
23399 @defvar Value.is_optimized_out
23400 This read-only boolean attribute is true if the compiler optimized out
23401 this value, thus it is not available for fetching from the inferior.
23405 The type of this @code{gdb.Value}. The value of this attribute is a
23406 @code{gdb.Type} object (@pxref{Types In Python}).
23409 @defvar Value.dynamic_type
23410 The dynamic type of this @code{gdb.Value}. This uses C@t{++} run-time
23411 type information (@acronym{RTTI}) to determine the dynamic type of the
23412 value. If this value is of class type, it will return the class in
23413 which the value is embedded, if any. If this value is of pointer or
23414 reference to a class type, it will compute the dynamic type of the
23415 referenced object, and return a pointer or reference to that type,
23416 respectively. In all other cases, it will return the value's static
23419 Note that this feature will only work when debugging a C@t{++} program
23420 that includes @acronym{RTTI} for the object in question. Otherwise,
23421 it will just return the static type of the value as in @kbd{ptype foo}
23422 (@pxref{Symbols, ptype}).
23425 @defvar Value.is_lazy
23426 The value of this read-only boolean attribute is @code{True} if this
23427 @code{gdb.Value} has not yet been fetched from the inferior.
23428 @value{GDBN} does not fetch values until necessary, for efficiency.
23432 myval = gdb.parse_and_eval ('somevar')
23435 The value of @code{somevar} is not fetched at this time. It will be
23436 fetched when the value is needed, or when the @code{fetch_lazy}
23440 The following methods are provided:
23442 @defun Value.__init__ (@var{val})
23443 Many Python values can be converted directly to a @code{gdb.Value} via
23444 this object initializer. Specifically:
23447 @item Python boolean
23448 A Python boolean is converted to the boolean type from the current
23451 @item Python integer
23452 A Python integer is converted to the C @code{long} type for the
23453 current architecture.
23456 A Python long is converted to the C @code{long long} type for the
23457 current architecture.
23460 A Python float is converted to the C @code{double} type for the
23461 current architecture.
23463 @item Python string
23464 A Python string is converted to a target string, using the current
23467 @item @code{gdb.Value}
23468 If @code{val} is a @code{gdb.Value}, then a copy of the value is made.
23470 @item @code{gdb.LazyString}
23471 If @code{val} is a @code{gdb.LazyString} (@pxref{Lazy Strings In
23472 Python}), then the lazy string's @code{value} method is called, and
23473 its result is used.
23477 @defun Value.cast (type)
23478 Return a new instance of @code{gdb.Value} that is the result of
23479 casting this instance to the type described by @var{type}, which must
23480 be a @code{gdb.Type} object. If the cast cannot be performed for some
23481 reason, this method throws an exception.
23484 @defun Value.dereference ()
23485 For pointer data types, this method returns a new @code{gdb.Value} object
23486 whose contents is the object pointed to by the pointer. For example, if
23487 @code{foo} is a C pointer to an @code{int}, declared in your C program as
23494 then you can use the corresponding @code{gdb.Value} to access what
23495 @code{foo} points to like this:
23498 bar = foo.dereference ()
23501 The result @code{bar} will be a @code{gdb.Value} object holding the
23502 value pointed to by @code{foo}.
23504 A similar function @code{Value.referenced_value} exists which also
23505 returns @code{gdb.Value} objects corresonding to the values pointed to
23506 by pointer values (and additionally, values referenced by reference
23507 values). However, the behavior of @code{Value.dereference}
23508 differs from @code{Value.referenced_value} by the fact that the
23509 behavior of @code{Value.dereference} is identical to applying the C
23510 unary operator @code{*} on a given value. For example, consider a
23511 reference to a pointer @code{ptrref}, declared in your C@t{++} program
23515 typedef int *intptr;
23519 intptr &ptrref = ptr;
23522 Though @code{ptrref} is a reference value, one can apply the method
23523 @code{Value.dereference} to the @code{gdb.Value} object corresponding
23524 to it and obtain a @code{gdb.Value} which is identical to that
23525 corresponding to @code{val}. However, if you apply the method
23526 @code{Value.referenced_value}, the result would be a @code{gdb.Value}
23527 object identical to that corresponding to @code{ptr}.
23530 py_ptrref = gdb.parse_and_eval ("ptrref")
23531 py_val = py_ptrref.dereference ()
23532 py_ptr = py_ptrref.referenced_value ()
23535 The @code{gdb.Value} object @code{py_val} is identical to that
23536 corresponding to @code{val}, and @code{py_ptr} is identical to that
23537 corresponding to @code{ptr}. In general, @code{Value.dereference} can
23538 be applied whenever the C unary operator @code{*} can be applied
23539 to the corresponding C value. For those cases where applying both
23540 @code{Value.dereference} and @code{Value.referenced_value} is allowed,
23541 the results obtained need not be identical (as we have seen in the above
23542 example). The results are however identical when applied on
23543 @code{gdb.Value} objects corresponding to pointers (@code{gdb.Value}
23544 objects with type code @code{TYPE_CODE_PTR}) in a C/C@t{++} program.
23547 @defun Value.referenced_value ()
23548 For pointer or reference data types, this method returns a new
23549 @code{gdb.Value} object corresponding to the value referenced by the
23550 pointer/reference value. For pointer data types,
23551 @code{Value.dereference} and @code{Value.referenced_value} produce
23552 identical results. The difference between these methods is that
23553 @code{Value.dereference} cannot get the values referenced by reference
23554 values. For example, consider a reference to an @code{int}, declared
23555 in your C@t{++} program as
23563 then applying @code{Value.dereference} to the @code{gdb.Value} object
23564 corresponding to @code{ref} will result in an error, while applying
23565 @code{Value.referenced_value} will result in a @code{gdb.Value} object
23566 identical to that corresponding to @code{val}.
23569 py_ref = gdb.parse_and_eval ("ref")
23570 er_ref = py_ref.dereference () # Results in error
23571 py_val = py_ref.referenced_value () # Returns the referenced value
23574 The @code{gdb.Value} object @code{py_val} is identical to that
23575 corresponding to @code{val}.
23578 @defun Value.dynamic_cast (type)
23579 Like @code{Value.cast}, but works as if the C@t{++} @code{dynamic_cast}
23580 operator were used. Consult a C@t{++} reference for details.
23583 @defun Value.reinterpret_cast (type)
23584 Like @code{Value.cast}, but works as if the C@t{++} @code{reinterpret_cast}
23585 operator were used. Consult a C@t{++} reference for details.
23588 @defun Value.string (@r{[}encoding@r{[}, errors@r{[}, length@r{]]]})
23589 If this @code{gdb.Value} represents a string, then this method
23590 converts the contents to a Python string. Otherwise, this method will
23591 throw an exception.
23593 Strings are recognized in a language-specific way; whether a given
23594 @code{gdb.Value} represents a string is determined by the current
23597 For C-like languages, a value is a string if it is a pointer to or an
23598 array of characters or ints. The string is assumed to be terminated
23599 by a zero of the appropriate width. However if the optional length
23600 argument is given, the string will be converted to that given length,
23601 ignoring any embedded zeros that the string may contain.
23603 If the optional @var{encoding} argument is given, it must be a string
23604 naming the encoding of the string in the @code{gdb.Value}, such as
23605 @code{"ascii"}, @code{"iso-8859-6"} or @code{"utf-8"}. It accepts
23606 the same encodings as the corresponding argument to Python's
23607 @code{string.decode} method, and the Python codec machinery will be used
23608 to convert the string. If @var{encoding} is not given, or if
23609 @var{encoding} is the empty string, then either the @code{target-charset}
23610 (@pxref{Character Sets}) will be used, or a language-specific encoding
23611 will be used, if the current language is able to supply one.
23613 The optional @var{errors} argument is the same as the corresponding
23614 argument to Python's @code{string.decode} method.
23616 If the optional @var{length} argument is given, the string will be
23617 fetched and converted to the given length.
23620 @defun Value.lazy_string (@r{[}encoding @r{[}, length@r{]]})
23621 If this @code{gdb.Value} represents a string, then this method
23622 converts the contents to a @code{gdb.LazyString} (@pxref{Lazy Strings
23623 In Python}). Otherwise, this method will throw an exception.
23625 If the optional @var{encoding} argument is given, it must be a string
23626 naming the encoding of the @code{gdb.LazyString}. Some examples are:
23627 @samp{ascii}, @samp{iso-8859-6} or @samp{utf-8}. If the
23628 @var{encoding} argument is an encoding that @value{GDBN} does
23629 recognize, @value{GDBN} will raise an error.
23631 When a lazy string is printed, the @value{GDBN} encoding machinery is
23632 used to convert the string during printing. If the optional
23633 @var{encoding} argument is not provided, or is an empty string,
23634 @value{GDBN} will automatically select the encoding most suitable for
23635 the string type. For further information on encoding in @value{GDBN}
23636 please see @ref{Character Sets}.
23638 If the optional @var{length} argument is given, the string will be
23639 fetched and encoded to the length of characters specified. If
23640 the @var{length} argument is not provided, the string will be fetched
23641 and encoded until a null of appropriate width is found.
23644 @defun Value.fetch_lazy ()
23645 If the @code{gdb.Value} object is currently a lazy value
23646 (@code{gdb.Value.is_lazy} is @code{True}), then the value is
23647 fetched from the inferior. Any errors that occur in the process
23648 will produce a Python exception.
23650 If the @code{gdb.Value} object is not a lazy value, this method
23653 This method does not return a value.
23657 @node Types In Python
23658 @subsubsection Types In Python
23659 @cindex types in Python
23660 @cindex Python, working with types
23663 @value{GDBN} represents types from the inferior using the class
23666 The following type-related functions are available in the @code{gdb}
23669 @findex gdb.lookup_type
23670 @defun gdb.lookup_type (name @r{[}, block@r{]})
23671 This function looks up a type by name. @var{name} is the name of the
23672 type to look up. It must be a string.
23674 If @var{block} is given, then @var{name} is looked up in that scope.
23675 Otherwise, it is searched for globally.
23677 Ordinarily, this function will return an instance of @code{gdb.Type}.
23678 If the named type cannot be found, it will throw an exception.
23681 If the type is a structure or class type, or an enum type, the fields
23682 of that type can be accessed using the Python @dfn{dictionary syntax}.
23683 For example, if @code{some_type} is a @code{gdb.Type} instance holding
23684 a structure type, you can access its @code{foo} field with:
23687 bar = some_type['foo']
23690 @code{bar} will be a @code{gdb.Field} object; see below under the
23691 description of the @code{Type.fields} method for a description of the
23692 @code{gdb.Field} class.
23694 An instance of @code{Type} has the following attributes:
23697 The type code for this type. The type code will be one of the
23698 @code{TYPE_CODE_} constants defined below.
23701 @defvar Type.sizeof
23702 The size of this type, in target @code{char} units. Usually, a
23703 target's @code{char} type will be an 8-bit byte. However, on some
23704 unusual platforms, this type may have a different size.
23708 The tag name for this type. The tag name is the name after
23709 @code{struct}, @code{union}, or @code{enum} in C and C@t{++}; not all
23710 languages have this concept. If this type has no tag name, then
23711 @code{None} is returned.
23714 The following methods are provided:
23716 @defun Type.fields ()
23717 For structure and union types, this method returns the fields. Range
23718 types have two fields, the minimum and maximum values. Enum types
23719 have one field per enum constant. Function and method types have one
23720 field per parameter. The base types of C@t{++} classes are also
23721 represented as fields. If the type has no fields, or does not fit
23722 into one of these categories, an empty sequence will be returned.
23724 Each field is a @code{gdb.Field} object, with some pre-defined attributes:
23727 This attribute is not available for @code{static} fields (as in
23728 C@t{++} or Java). For non-@code{static} fields, the value is the bit
23729 position of the field. For @code{enum} fields, the value is the
23730 enumeration member's integer representation.
23733 The name of the field, or @code{None} for anonymous fields.
23736 This is @code{True} if the field is artificial, usually meaning that
23737 it was provided by the compiler and not the user. This attribute is
23738 always provided, and is @code{False} if the field is not artificial.
23740 @item is_base_class
23741 This is @code{True} if the field represents a base class of a C@t{++}
23742 structure. This attribute is always provided, and is @code{False}
23743 if the field is not a base class of the type that is the argument of
23744 @code{fields}, or if that type was not a C@t{++} class.
23747 If the field is packed, or is a bitfield, then this will have a
23748 non-zero value, which is the size of the field in bits. Otherwise,
23749 this will be zero; in this case the field's size is given by its type.
23752 The type of the field. This is usually an instance of @code{Type},
23753 but it can be @code{None} in some situations.
23757 @defun Type.array (@var{n1} @r{[}, @var{n2}@r{]})
23758 Return a new @code{gdb.Type} object which represents an array of this
23759 type. If one argument is given, it is the inclusive upper bound of
23760 the array; in this case the lower bound is zero. If two arguments are
23761 given, the first argument is the lower bound of the array, and the
23762 second argument is the upper bound of the array. An array's length
23763 must not be negative, but the bounds can be.
23766 @defun Type.vector (@var{n1} @r{[}, @var{n2}@r{]})
23767 Return a new @code{gdb.Type} object which represents a vector of this
23768 type. If one argument is given, it is the inclusive upper bound of
23769 the vector; in this case the lower bound is zero. If two arguments are
23770 given, the first argument is the lower bound of the vector, and the
23771 second argument is the upper bound of the vector. A vector's length
23772 must not be negative, but the bounds can be.
23774 The difference between an @code{array} and a @code{vector} is that
23775 arrays behave like in C: when used in expressions they decay to a pointer
23776 to the first element whereas vectors are treated as first class values.
23779 @defun Type.const ()
23780 Return a new @code{gdb.Type} object which represents a
23781 @code{const}-qualified variant of this type.
23784 @defun Type.volatile ()
23785 Return a new @code{gdb.Type} object which represents a
23786 @code{volatile}-qualified variant of this type.
23789 @defun Type.unqualified ()
23790 Return a new @code{gdb.Type} object which represents an unqualified
23791 variant of this type. That is, the result is neither @code{const} nor
23795 @defun Type.range ()
23796 Return a Python @code{Tuple} object that contains two elements: the
23797 low bound of the argument type and the high bound of that type. If
23798 the type does not have a range, @value{GDBN} will raise a
23799 @code{gdb.error} exception (@pxref{Exception Handling}).
23802 @defun Type.reference ()
23803 Return a new @code{gdb.Type} object which represents a reference to this
23807 @defun Type.pointer ()
23808 Return a new @code{gdb.Type} object which represents a pointer to this
23812 @defun Type.strip_typedefs ()
23813 Return a new @code{gdb.Type} that represents the real type,
23814 after removing all layers of typedefs.
23817 @defun Type.target ()
23818 Return a new @code{gdb.Type} object which represents the target type
23821 For a pointer type, the target type is the type of the pointed-to
23822 object. For an array type (meaning C-like arrays), the target type is
23823 the type of the elements of the array. For a function or method type,
23824 the target type is the type of the return value. For a complex type,
23825 the target type is the type of the elements. For a typedef, the
23826 target type is the aliased type.
23828 If the type does not have a target, this method will throw an
23832 @defun Type.template_argument (n @r{[}, block@r{]})
23833 If this @code{gdb.Type} is an instantiation of a template, this will
23834 return a new @code{gdb.Type} which represents the type of the
23835 @var{n}th template argument.
23837 If this @code{gdb.Type} is not a template type, this will throw an
23838 exception. Ordinarily, only C@t{++} code will have template types.
23840 If @var{block} is given, then @var{name} is looked up in that scope.
23841 Otherwise, it is searched for globally.
23845 Each type has a code, which indicates what category this type falls
23846 into. The available type categories are represented by constants
23847 defined in the @code{gdb} module:
23850 @findex TYPE_CODE_PTR
23851 @findex gdb.TYPE_CODE_PTR
23852 @item gdb.TYPE_CODE_PTR
23853 The type is a pointer.
23855 @findex TYPE_CODE_ARRAY
23856 @findex gdb.TYPE_CODE_ARRAY
23857 @item gdb.TYPE_CODE_ARRAY
23858 The type is an array.
23860 @findex TYPE_CODE_STRUCT
23861 @findex gdb.TYPE_CODE_STRUCT
23862 @item gdb.TYPE_CODE_STRUCT
23863 The type is a structure.
23865 @findex TYPE_CODE_UNION
23866 @findex gdb.TYPE_CODE_UNION
23867 @item gdb.TYPE_CODE_UNION
23868 The type is a union.
23870 @findex TYPE_CODE_ENUM
23871 @findex gdb.TYPE_CODE_ENUM
23872 @item gdb.TYPE_CODE_ENUM
23873 The type is an enum.
23875 @findex TYPE_CODE_FLAGS
23876 @findex gdb.TYPE_CODE_FLAGS
23877 @item gdb.TYPE_CODE_FLAGS
23878 A bit flags type, used for things such as status registers.
23880 @findex TYPE_CODE_FUNC
23881 @findex gdb.TYPE_CODE_FUNC
23882 @item gdb.TYPE_CODE_FUNC
23883 The type is a function.
23885 @findex TYPE_CODE_INT
23886 @findex gdb.TYPE_CODE_INT
23887 @item gdb.TYPE_CODE_INT
23888 The type is an integer type.
23890 @findex TYPE_CODE_FLT
23891 @findex gdb.TYPE_CODE_FLT
23892 @item gdb.TYPE_CODE_FLT
23893 A floating point type.
23895 @findex TYPE_CODE_VOID
23896 @findex gdb.TYPE_CODE_VOID
23897 @item gdb.TYPE_CODE_VOID
23898 The special type @code{void}.
23900 @findex TYPE_CODE_SET
23901 @findex gdb.TYPE_CODE_SET
23902 @item gdb.TYPE_CODE_SET
23905 @findex TYPE_CODE_RANGE
23906 @findex gdb.TYPE_CODE_RANGE
23907 @item gdb.TYPE_CODE_RANGE
23908 A range type, that is, an integer type with bounds.
23910 @findex TYPE_CODE_STRING
23911 @findex gdb.TYPE_CODE_STRING
23912 @item gdb.TYPE_CODE_STRING
23913 A string type. Note that this is only used for certain languages with
23914 language-defined string types; C strings are not represented this way.
23916 @findex TYPE_CODE_BITSTRING
23917 @findex gdb.TYPE_CODE_BITSTRING
23918 @item gdb.TYPE_CODE_BITSTRING
23919 A string of bits. It is deprecated.
23921 @findex TYPE_CODE_ERROR
23922 @findex gdb.TYPE_CODE_ERROR
23923 @item gdb.TYPE_CODE_ERROR
23924 An unknown or erroneous type.
23926 @findex TYPE_CODE_METHOD
23927 @findex gdb.TYPE_CODE_METHOD
23928 @item gdb.TYPE_CODE_METHOD
23929 A method type, as found in C@t{++} or Java.
23931 @findex TYPE_CODE_METHODPTR
23932 @findex gdb.TYPE_CODE_METHODPTR
23933 @item gdb.TYPE_CODE_METHODPTR
23934 A pointer-to-member-function.
23936 @findex TYPE_CODE_MEMBERPTR
23937 @findex gdb.TYPE_CODE_MEMBERPTR
23938 @item gdb.TYPE_CODE_MEMBERPTR
23939 A pointer-to-member.
23941 @findex TYPE_CODE_REF
23942 @findex gdb.TYPE_CODE_REF
23943 @item gdb.TYPE_CODE_REF
23946 @findex TYPE_CODE_CHAR
23947 @findex gdb.TYPE_CODE_CHAR
23948 @item gdb.TYPE_CODE_CHAR
23951 @findex TYPE_CODE_BOOL
23952 @findex gdb.TYPE_CODE_BOOL
23953 @item gdb.TYPE_CODE_BOOL
23956 @findex TYPE_CODE_COMPLEX
23957 @findex gdb.TYPE_CODE_COMPLEX
23958 @item gdb.TYPE_CODE_COMPLEX
23959 A complex float type.
23961 @findex TYPE_CODE_TYPEDEF
23962 @findex gdb.TYPE_CODE_TYPEDEF
23963 @item gdb.TYPE_CODE_TYPEDEF
23964 A typedef to some other type.
23966 @findex TYPE_CODE_NAMESPACE
23967 @findex gdb.TYPE_CODE_NAMESPACE
23968 @item gdb.TYPE_CODE_NAMESPACE
23969 A C@t{++} namespace.
23971 @findex TYPE_CODE_DECFLOAT
23972 @findex gdb.TYPE_CODE_DECFLOAT
23973 @item gdb.TYPE_CODE_DECFLOAT
23974 A decimal floating point type.
23976 @findex TYPE_CODE_INTERNAL_FUNCTION
23977 @findex gdb.TYPE_CODE_INTERNAL_FUNCTION
23978 @item gdb.TYPE_CODE_INTERNAL_FUNCTION
23979 A function internal to @value{GDBN}. This is the type used to represent
23980 convenience functions.
23983 Further support for types is provided in the @code{gdb.types}
23984 Python module (@pxref{gdb.types}).
23986 @node Pretty Printing API
23987 @subsubsection Pretty Printing API
23989 An example output is provided (@pxref{Pretty Printing}).
23991 A pretty-printer is just an object that holds a value and implements a
23992 specific interface, defined here.
23994 @defun pretty_printer.children (self)
23995 @value{GDBN} will call this method on a pretty-printer to compute the
23996 children of the pretty-printer's value.
23998 This method must return an object conforming to the Python iterator
23999 protocol. Each item returned by the iterator must be a tuple holding
24000 two elements. The first element is the ``name'' of the child; the
24001 second element is the child's value. The value can be any Python
24002 object which is convertible to a @value{GDBN} value.
24004 This method is optional. If it does not exist, @value{GDBN} will act
24005 as though the value has no children.
24008 @defun pretty_printer.display_hint (self)
24009 The CLI may call this method and use its result to change the
24010 formatting of a value. The result will also be supplied to an MI
24011 consumer as a @samp{displayhint} attribute of the variable being
24014 This method is optional. If it does exist, this method must return a
24017 Some display hints are predefined by @value{GDBN}:
24021 Indicate that the object being printed is ``array-like''. The CLI
24022 uses this to respect parameters such as @code{set print elements} and
24023 @code{set print array}.
24026 Indicate that the object being printed is ``map-like'', and that the
24027 children of this value can be assumed to alternate between keys and
24031 Indicate that the object being printed is ``string-like''. If the
24032 printer's @code{to_string} method returns a Python string of some
24033 kind, then @value{GDBN} will call its internal language-specific
24034 string-printing function to format the string. For the CLI this means
24035 adding quotation marks, possibly escaping some characters, respecting
24036 @code{set print elements}, and the like.
24040 @defun pretty_printer.to_string (self)
24041 @value{GDBN} will call this method to display the string
24042 representation of the value passed to the object's constructor.
24044 When printing from the CLI, if the @code{to_string} method exists,
24045 then @value{GDBN} will prepend its result to the values returned by
24046 @code{children}. Exactly how this formatting is done is dependent on
24047 the display hint, and may change as more hints are added. Also,
24048 depending on the print settings (@pxref{Print Settings}), the CLI may
24049 print just the result of @code{to_string} in a stack trace, omitting
24050 the result of @code{children}.
24052 If this method returns a string, it is printed verbatim.
24054 Otherwise, if this method returns an instance of @code{gdb.Value},
24055 then @value{GDBN} prints this value. This may result in a call to
24056 another pretty-printer.
24058 If instead the method returns a Python value which is convertible to a
24059 @code{gdb.Value}, then @value{GDBN} performs the conversion and prints
24060 the resulting value. Again, this may result in a call to another
24061 pretty-printer. Python scalars (integers, floats, and booleans) and
24062 strings are convertible to @code{gdb.Value}; other types are not.
24064 Finally, if this method returns @code{None} then no further operations
24065 are peformed in this method and nothing is printed.
24067 If the result is not one of these types, an exception is raised.
24070 @value{GDBN} provides a function which can be used to look up the
24071 default pretty-printer for a @code{gdb.Value}:
24073 @findex gdb.default_visualizer
24074 @defun gdb.default_visualizer (value)
24075 This function takes a @code{gdb.Value} object as an argument. If a
24076 pretty-printer for this value exists, then it is returned. If no such
24077 printer exists, then this returns @code{None}.
24080 @node Selecting Pretty-Printers
24081 @subsubsection Selecting Pretty-Printers
24083 The Python list @code{gdb.pretty_printers} contains an array of
24084 functions or callable objects that have been registered via addition
24085 as a pretty-printer. Printers in this list are called @code{global}
24086 printers, they're available when debugging all inferiors.
24087 Each @code{gdb.Progspace} contains a @code{pretty_printers} attribute.
24088 Each @code{gdb.Objfile} also contains a @code{pretty_printers}
24091 Each function on these lists is passed a single @code{gdb.Value}
24092 argument and should return a pretty-printer object conforming to the
24093 interface definition above (@pxref{Pretty Printing API}). If a function
24094 cannot create a pretty-printer for the value, it should return
24097 @value{GDBN} first checks the @code{pretty_printers} attribute of each
24098 @code{gdb.Objfile} in the current program space and iteratively calls
24099 each enabled lookup routine in the list for that @code{gdb.Objfile}
24100 until it receives a pretty-printer object.
24101 If no pretty-printer is found in the objfile lists, @value{GDBN} then
24102 searches the pretty-printer list of the current program space,
24103 calling each enabled function until an object is returned.
24104 After these lists have been exhausted, it tries the global
24105 @code{gdb.pretty_printers} list, again calling each enabled function until an
24106 object is returned.
24108 The order in which the objfiles are searched is not specified. For a
24109 given list, functions are always invoked from the head of the list,
24110 and iterated over sequentially until the end of the list, or a printer
24111 object is returned.
24113 For various reasons a pretty-printer may not work.
24114 For example, the underlying data structure may have changed and
24115 the pretty-printer is out of date.
24117 The consequences of a broken pretty-printer are severe enough that
24118 @value{GDBN} provides support for enabling and disabling individual
24119 printers. For example, if @code{print frame-arguments} is on,
24120 a backtrace can become highly illegible if any argument is printed
24121 with a broken printer.
24123 Pretty-printers are enabled and disabled by attaching an @code{enabled}
24124 attribute to the registered function or callable object. If this attribute
24125 is present and its value is @code{False}, the printer is disabled, otherwise
24126 the printer is enabled.
24128 @node Writing a Pretty-Printer
24129 @subsubsection Writing a Pretty-Printer
24130 @cindex writing a pretty-printer
24132 A pretty-printer consists of two parts: a lookup function to detect
24133 if the type is supported, and the printer itself.
24135 Here is an example showing how a @code{std::string} printer might be
24136 written. @xref{Pretty Printing API}, for details on the API this class
24140 class StdStringPrinter(object):
24141 "Print a std::string"
24143 def __init__(self, val):
24146 def to_string(self):
24147 return self.val['_M_dataplus']['_M_p']
24149 def display_hint(self):
24153 And here is an example showing how a lookup function for the printer
24154 example above might be written.
24157 def str_lookup_function(val):
24158 lookup_tag = val.type.tag
24159 if lookup_tag == None:
24161 regex = re.compile("^std::basic_string<char,.*>$")
24162 if regex.match(lookup_tag):
24163 return StdStringPrinter(val)
24167 The example lookup function extracts the value's type, and attempts to
24168 match it to a type that it can pretty-print. If it is a type the
24169 printer can pretty-print, it will return a printer object. If not, it
24170 returns @code{None}.
24172 We recommend that you put your core pretty-printers into a Python
24173 package. If your pretty-printers are for use with a library, we
24174 further recommend embedding a version number into the package name.
24175 This practice will enable @value{GDBN} to load multiple versions of
24176 your pretty-printers at the same time, because they will have
24179 You should write auto-loaded code (@pxref{Python Auto-loading}) such that it
24180 can be evaluated multiple times without changing its meaning. An
24181 ideal auto-load file will consist solely of @code{import}s of your
24182 printer modules, followed by a call to a register pretty-printers with
24183 the current objfile.
24185 Taken as a whole, this approach will scale nicely to multiple
24186 inferiors, each potentially using a different library version.
24187 Embedding a version number in the Python package name will ensure that
24188 @value{GDBN} is able to load both sets of printers simultaneously.
24189 Then, because the search for pretty-printers is done by objfile, and
24190 because your auto-loaded code took care to register your library's
24191 printers with a specific objfile, @value{GDBN} will find the correct
24192 printers for the specific version of the library used by each
24195 To continue the @code{std::string} example (@pxref{Pretty Printing API}),
24196 this code might appear in @code{gdb.libstdcxx.v6}:
24199 def register_printers(objfile):
24200 objfile.pretty_printers.append(str_lookup_function)
24204 And then the corresponding contents of the auto-load file would be:
24207 import gdb.libstdcxx.v6
24208 gdb.libstdcxx.v6.register_printers(gdb.current_objfile())
24211 The previous example illustrates a basic pretty-printer.
24212 There are a few things that can be improved on.
24213 The printer doesn't have a name, making it hard to identify in a
24214 list of installed printers. The lookup function has a name, but
24215 lookup functions can have arbitrary, even identical, names.
24217 Second, the printer only handles one type, whereas a library typically has
24218 several types. One could install a lookup function for each desired type
24219 in the library, but one could also have a single lookup function recognize
24220 several types. The latter is the conventional way this is handled.
24221 If a pretty-printer can handle multiple data types, then its
24222 @dfn{subprinters} are the printers for the individual data types.
24224 The @code{gdb.printing} module provides a formal way of solving these
24225 problems (@pxref{gdb.printing}).
24226 Here is another example that handles multiple types.
24228 These are the types we are going to pretty-print:
24231 struct foo @{ int a, b; @};
24232 struct bar @{ struct foo x, y; @};
24235 Here are the printers:
24239 """Print a foo object."""
24241 def __init__(self, val):
24244 def to_string(self):
24245 return ("a=<" + str(self.val["a"]) +
24246 "> b=<" + str(self.val["b"]) + ">")
24249 """Print a bar object."""
24251 def __init__(self, val):
24254 def to_string(self):
24255 return ("x=<" + str(self.val["x"]) +
24256 "> y=<" + str(self.val["y"]) + ">")
24259 This example doesn't need a lookup function, that is handled by the
24260 @code{gdb.printing} module. Instead a function is provided to build up
24261 the object that handles the lookup.
24264 import gdb.printing
24266 def build_pretty_printer():
24267 pp = gdb.printing.RegexpCollectionPrettyPrinter(
24269 pp.add_printer('foo', '^foo$', fooPrinter)
24270 pp.add_printer('bar', '^bar$', barPrinter)
24274 And here is the autoload support:
24277 import gdb.printing
24279 gdb.printing.register_pretty_printer(
24280 gdb.current_objfile(),
24281 my_library.build_pretty_printer())
24284 Finally, when this printer is loaded into @value{GDBN}, here is the
24285 corresponding output of @samp{info pretty-printer}:
24288 (gdb) info pretty-printer
24295 @node Type Printing API
24296 @subsubsection Type Printing API
24297 @cindex type printing API for Python
24299 @value{GDBN} provides a way for Python code to customize type display.
24300 This is mainly useful for substituting canonical typedef names for
24303 @cindex type printer
24304 A @dfn{type printer} is just a Python object conforming to a certain
24305 protocol. A simple base class implementing the protocol is provided;
24306 see @ref{gdb.types}. A type printer must supply at least:
24308 @defivar type_printer enabled
24309 A boolean which is True if the printer is enabled, and False
24310 otherwise. This is manipulated by the @code{enable type-printer}
24311 and @code{disable type-printer} commands.
24314 @defivar type_printer name
24315 The name of the type printer. This must be a string. This is used by
24316 the @code{enable type-printer} and @code{disable type-printer}
24320 @defmethod type_printer instantiate (self)
24321 This is called by @value{GDBN} at the start of type-printing. It is
24322 only called if the type printer is enabled. This method must return a
24323 new object that supplies a @code{recognize} method, as described below.
24327 When displaying a type, say via the @code{ptype} command, @value{GDBN}
24328 will compute a list of type recognizers. This is done by iterating
24329 first over the per-objfile type printers (@pxref{Objfiles In Python}),
24330 followed by the per-progspace type printers (@pxref{Progspaces In
24331 Python}), and finally the global type printers.
24333 @value{GDBN} will call the @code{instantiate} method of each enabled
24334 type printer. If this method returns @code{None}, then the result is
24335 ignored; otherwise, it is appended to the list of recognizers.
24337 Then, when @value{GDBN} is going to display a type name, it iterates
24338 over the list of recognizers. For each one, it calls the recognition
24339 function, stopping if the function returns a non-@code{None} value.
24340 The recognition function is defined as:
24342 @defmethod type_recognizer recognize (self, type)
24343 If @var{type} is not recognized, return @code{None}. Otherwise,
24344 return a string which is to be printed as the name of @var{type}.
24345 @var{type} will be an instance of @code{gdb.Type} (@pxref{Types In
24349 @value{GDBN} uses this two-pass approach so that type printers can
24350 efficiently cache information without holding on to it too long. For
24351 example, it can be convenient to look up type information in a type
24352 printer and hold it for a recognizer's lifetime; if a single pass were
24353 done then type printers would have to make use of the event system in
24354 order to avoid holding information that could become stale as the
24357 @node Inferiors In Python
24358 @subsubsection Inferiors In Python
24359 @cindex inferiors in Python
24361 @findex gdb.Inferior
24362 Programs which are being run under @value{GDBN} are called inferiors
24363 (@pxref{Inferiors and Programs}). Python scripts can access
24364 information about and manipulate inferiors controlled by @value{GDBN}
24365 via objects of the @code{gdb.Inferior} class.
24367 The following inferior-related functions are available in the @code{gdb}
24370 @defun gdb.inferiors ()
24371 Return a tuple containing all inferior objects.
24374 @defun gdb.selected_inferior ()
24375 Return an object representing the current inferior.
24378 A @code{gdb.Inferior} object has the following attributes:
24380 @defvar Inferior.num
24381 ID of inferior, as assigned by GDB.
24384 @defvar Inferior.pid
24385 Process ID of the inferior, as assigned by the underlying operating
24389 @defvar Inferior.was_attached
24390 Boolean signaling whether the inferior was created using `attach', or
24391 started by @value{GDBN} itself.
24394 A @code{gdb.Inferior} object has the following methods:
24396 @defun Inferior.is_valid ()
24397 Returns @code{True} if the @code{gdb.Inferior} object is valid,
24398 @code{False} if not. A @code{gdb.Inferior} object will become invalid
24399 if the inferior no longer exists within @value{GDBN}. All other
24400 @code{gdb.Inferior} methods will throw an exception if it is invalid
24401 at the time the method is called.
24404 @defun Inferior.threads ()
24405 This method returns a tuple holding all the threads which are valid
24406 when it is called. If there are no valid threads, the method will
24407 return an empty tuple.
24410 @findex Inferior.read_memory
24411 @defun Inferior.read_memory (address, length)
24412 Read @var{length} bytes of memory from the inferior, starting at
24413 @var{address}. Returns a buffer object, which behaves much like an array
24414 or a string. It can be modified and given to the
24415 @code{Inferior.write_memory} function. In @code{Python} 3, the return
24416 value is a @code{memoryview} object.
24419 @findex Inferior.write_memory
24420 @defun Inferior.write_memory (address, buffer @r{[}, length@r{]})
24421 Write the contents of @var{buffer} to the inferior, starting at
24422 @var{address}. The @var{buffer} parameter must be a Python object
24423 which supports the buffer protocol, i.e., a string, an array or the
24424 object returned from @code{Inferior.read_memory}. If given, @var{length}
24425 determines the number of bytes from @var{buffer} to be written.
24428 @findex gdb.search_memory
24429 @defun Inferior.search_memory (address, length, pattern)
24430 Search a region of the inferior memory starting at @var{address} with
24431 the given @var{length} using the search pattern supplied in
24432 @var{pattern}. The @var{pattern} parameter must be a Python object
24433 which supports the buffer protocol, i.e., a string, an array or the
24434 object returned from @code{gdb.read_memory}. Returns a Python @code{Long}
24435 containing the address where the pattern was found, or @code{None} if
24436 the pattern could not be found.
24439 @node Events In Python
24440 @subsubsection Events In Python
24441 @cindex inferior events in Python
24443 @value{GDBN} provides a general event facility so that Python code can be
24444 notified of various state changes, particularly changes that occur in
24447 An @dfn{event} is just an object that describes some state change. The
24448 type of the object and its attributes will vary depending on the details
24449 of the change. All the existing events are described below.
24451 In order to be notified of an event, you must register an event handler
24452 with an @dfn{event registry}. An event registry is an object in the
24453 @code{gdb.events} module which dispatches particular events. A registry
24454 provides methods to register and unregister event handlers:
24456 @defun EventRegistry.connect (object)
24457 Add the given callable @var{object} to the registry. This object will be
24458 called when an event corresponding to this registry occurs.
24461 @defun EventRegistry.disconnect (object)
24462 Remove the given @var{object} from the registry. Once removed, the object
24463 will no longer receive notifications of events.
24466 Here is an example:
24469 def exit_handler (event):
24470 print "event type: exit"
24471 print "exit code: %d" % (event.exit_code)
24473 gdb.events.exited.connect (exit_handler)
24476 In the above example we connect our handler @code{exit_handler} to the
24477 registry @code{events.exited}. Once connected, @code{exit_handler} gets
24478 called when the inferior exits. The argument @dfn{event} in this example is
24479 of type @code{gdb.ExitedEvent}. As you can see in the example the
24480 @code{ExitedEvent} object has an attribute which indicates the exit code of
24483 The following is a listing of the event registries that are available and
24484 details of the events they emit:
24489 Emits @code{gdb.ThreadEvent}.
24491 Some events can be thread specific when @value{GDBN} is running in non-stop
24492 mode. When represented in Python, these events all extend
24493 @code{gdb.ThreadEvent}. Note, this event is not emitted directly; instead,
24494 events which are emitted by this or other modules might extend this event.
24495 Examples of these events are @code{gdb.BreakpointEvent} and
24496 @code{gdb.ContinueEvent}.
24498 @defvar ThreadEvent.inferior_thread
24499 In non-stop mode this attribute will be set to the specific thread which was
24500 involved in the emitted event. Otherwise, it will be set to @code{None}.
24503 Emits @code{gdb.ContinueEvent} which extends @code{gdb.ThreadEvent}.
24505 This event indicates that the inferior has been continued after a stop. For
24506 inherited attribute refer to @code{gdb.ThreadEvent} above.
24508 @item events.exited
24509 Emits @code{events.ExitedEvent} which indicates that the inferior has exited.
24510 @code{events.ExitedEvent} has two attributes:
24511 @defvar ExitedEvent.exit_code
24512 An integer representing the exit code, if available, which the inferior
24513 has returned. (The exit code could be unavailable if, for example,
24514 @value{GDBN} detaches from the inferior.) If the exit code is unavailable,
24515 the attribute does not exist.
24517 @defvar ExitedEvent inferior
24518 A reference to the inferior which triggered the @code{exited} event.
24522 Emits @code{gdb.StopEvent} which extends @code{gdb.ThreadEvent}.
24524 Indicates that the inferior has stopped. All events emitted by this registry
24525 extend StopEvent. As a child of @code{gdb.ThreadEvent}, @code{gdb.StopEvent}
24526 will indicate the stopped thread when @value{GDBN} is running in non-stop
24527 mode. Refer to @code{gdb.ThreadEvent} above for more details.
24529 Emits @code{gdb.SignalEvent} which extends @code{gdb.StopEvent}.
24531 This event indicates that the inferior or one of its threads has received as
24532 signal. @code{gdb.SignalEvent} has the following attributes:
24534 @defvar SignalEvent.stop_signal
24535 A string representing the signal received by the inferior. A list of possible
24536 signal values can be obtained by running the command @code{info signals} in
24537 the @value{GDBN} command prompt.
24540 Also emits @code{gdb.BreakpointEvent} which extends @code{gdb.StopEvent}.
24542 @code{gdb.BreakpointEvent} event indicates that one or more breakpoints have
24543 been hit, and has the following attributes:
24545 @defvar BreakpointEvent.breakpoints
24546 A sequence containing references to all the breakpoints (type
24547 @code{gdb.Breakpoint}) that were hit.
24548 @xref{Breakpoints In Python}, for details of the @code{gdb.Breakpoint} object.
24550 @defvar BreakpointEvent.breakpoint
24551 A reference to the first breakpoint that was hit.
24552 This function is maintained for backward compatibility and is now deprecated
24553 in favor of the @code{gdb.BreakpointEvent.breakpoints} attribute.
24556 @item events.new_objfile
24557 Emits @code{gdb.NewObjFileEvent} which indicates that a new object file has
24558 been loaded by @value{GDBN}. @code{gdb.NewObjFileEvent} has one attribute:
24560 @defvar NewObjFileEvent.new_objfile
24561 A reference to the object file (@code{gdb.Objfile}) which has been loaded.
24562 @xref{Objfiles In Python}, for details of the @code{gdb.Objfile} object.
24567 @node Threads In Python
24568 @subsubsection Threads In Python
24569 @cindex threads in python
24571 @findex gdb.InferiorThread
24572 Python scripts can access information about, and manipulate inferior threads
24573 controlled by @value{GDBN}, via objects of the @code{gdb.InferiorThread} class.
24575 The following thread-related functions are available in the @code{gdb}
24578 @findex gdb.selected_thread
24579 @defun gdb.selected_thread ()
24580 This function returns the thread object for the selected thread. If there
24581 is no selected thread, this will return @code{None}.
24584 A @code{gdb.InferiorThread} object has the following attributes:
24586 @defvar InferiorThread.name
24587 The name of the thread. If the user specified a name using
24588 @code{thread name}, then this returns that name. Otherwise, if an
24589 OS-supplied name is available, then it is returned. Otherwise, this
24590 returns @code{None}.
24592 This attribute can be assigned to. The new value must be a string
24593 object, which sets the new name, or @code{None}, which removes any
24594 user-specified thread name.
24597 @defvar InferiorThread.num
24598 ID of the thread, as assigned by GDB.
24601 @defvar InferiorThread.ptid
24602 ID of the thread, as assigned by the operating system. This attribute is a
24603 tuple containing three integers. The first is the Process ID (PID); the second
24604 is the Lightweight Process ID (LWPID), and the third is the Thread ID (TID).
24605 Either the LWPID or TID may be 0, which indicates that the operating system
24606 does not use that identifier.
24609 A @code{gdb.InferiorThread} object has the following methods:
24611 @defun InferiorThread.is_valid ()
24612 Returns @code{True} if the @code{gdb.InferiorThread} object is valid,
24613 @code{False} if not. A @code{gdb.InferiorThread} object will become
24614 invalid if the thread exits, or the inferior that the thread belongs
24615 is deleted. All other @code{gdb.InferiorThread} methods will throw an
24616 exception if it is invalid at the time the method is called.
24619 @defun InferiorThread.switch ()
24620 This changes @value{GDBN}'s currently selected thread to the one represented
24624 @defun InferiorThread.is_stopped ()
24625 Return a Boolean indicating whether the thread is stopped.
24628 @defun InferiorThread.is_running ()
24629 Return a Boolean indicating whether the thread is running.
24632 @defun InferiorThread.is_exited ()
24633 Return a Boolean indicating whether the thread is exited.
24636 @node Commands In Python
24637 @subsubsection Commands In Python
24639 @cindex commands in python
24640 @cindex python commands
24641 You can implement new @value{GDBN} CLI commands in Python. A CLI
24642 command is implemented using an instance of the @code{gdb.Command}
24643 class, most commonly using a subclass.
24645 @defun Command.__init__ (name, @var{command_class} @r{[}, @var{completer_class} @r{[}, @var{prefix}@r{]]})
24646 The object initializer for @code{Command} registers the new command
24647 with @value{GDBN}. This initializer is normally invoked from the
24648 subclass' own @code{__init__} method.
24650 @var{name} is the name of the command. If @var{name} consists of
24651 multiple words, then the initial words are looked for as prefix
24652 commands. In this case, if one of the prefix commands does not exist,
24653 an exception is raised.
24655 There is no support for multi-line commands.
24657 @var{command_class} should be one of the @samp{COMMAND_} constants
24658 defined below. This argument tells @value{GDBN} how to categorize the
24659 new command in the help system.
24661 @var{completer_class} is an optional argument. If given, it should be
24662 one of the @samp{COMPLETE_} constants defined below. This argument
24663 tells @value{GDBN} how to perform completion for this command. If not
24664 given, @value{GDBN} will attempt to complete using the object's
24665 @code{complete} method (see below); if no such method is found, an
24666 error will occur when completion is attempted.
24668 @var{prefix} is an optional argument. If @code{True}, then the new
24669 command is a prefix command; sub-commands of this command may be
24672 The help text for the new command is taken from the Python
24673 documentation string for the command's class, if there is one. If no
24674 documentation string is provided, the default value ``This command is
24675 not documented.'' is used.
24678 @cindex don't repeat Python command
24679 @defun Command.dont_repeat ()
24680 By default, a @value{GDBN} command is repeated when the user enters a
24681 blank line at the command prompt. A command can suppress this
24682 behavior by invoking the @code{dont_repeat} method. This is similar
24683 to the user command @code{dont-repeat}, see @ref{Define, dont-repeat}.
24686 @defun Command.invoke (argument, from_tty)
24687 This method is called by @value{GDBN} when this command is invoked.
24689 @var{argument} is a string. It is the argument to the command, after
24690 leading and trailing whitespace has been stripped.
24692 @var{from_tty} is a boolean argument. When true, this means that the
24693 command was entered by the user at the terminal; when false it means
24694 that the command came from elsewhere.
24696 If this method throws an exception, it is turned into a @value{GDBN}
24697 @code{error} call. Otherwise, the return value is ignored.
24699 @findex gdb.string_to_argv
24700 To break @var{argument} up into an argv-like string use
24701 @code{gdb.string_to_argv}. This function behaves identically to
24702 @value{GDBN}'s internal argument lexer @code{buildargv}.
24703 It is recommended to use this for consistency.
24704 Arguments are separated by spaces and may be quoted.
24708 print gdb.string_to_argv ("1 2\ \\\"3 '4 \"5' \"6 '7\"")
24709 ['1', '2 "3', '4 "5', "6 '7"]
24714 @cindex completion of Python commands
24715 @defun Command.complete (text, word)
24716 This method is called by @value{GDBN} when the user attempts
24717 completion on this command. All forms of completion are handled by
24718 this method, that is, the @key{TAB} and @key{M-?} key bindings
24719 (@pxref{Completion}), and the @code{complete} command (@pxref{Help,
24722 The arguments @var{text} and @var{word} are both strings. @var{text}
24723 holds the complete command line up to the cursor's location.
24724 @var{word} holds the last word of the command line; this is computed
24725 using a word-breaking heuristic.
24727 The @code{complete} method can return several values:
24730 If the return value is a sequence, the contents of the sequence are
24731 used as the completions. It is up to @code{complete} to ensure that the
24732 contents actually do complete the word. A zero-length sequence is
24733 allowed, it means that there were no completions available. Only
24734 string elements of the sequence are used; other elements in the
24735 sequence are ignored.
24738 If the return value is one of the @samp{COMPLETE_} constants defined
24739 below, then the corresponding @value{GDBN}-internal completion
24740 function is invoked, and its result is used.
24743 All other results are treated as though there were no available
24748 When a new command is registered, it must be declared as a member of
24749 some general class of commands. This is used to classify top-level
24750 commands in the on-line help system; note that prefix commands are not
24751 listed under their own category but rather that of their top-level
24752 command. The available classifications are represented by constants
24753 defined in the @code{gdb} module:
24756 @findex COMMAND_NONE
24757 @findex gdb.COMMAND_NONE
24758 @item gdb.COMMAND_NONE
24759 The command does not belong to any particular class. A command in
24760 this category will not be displayed in any of the help categories.
24762 @findex COMMAND_RUNNING
24763 @findex gdb.COMMAND_RUNNING
24764 @item gdb.COMMAND_RUNNING
24765 The command is related to running the inferior. For example,
24766 @code{start}, @code{step}, and @code{continue} are in this category.
24767 Type @kbd{help running} at the @value{GDBN} prompt to see a list of
24768 commands in this category.
24770 @findex COMMAND_DATA
24771 @findex gdb.COMMAND_DATA
24772 @item gdb.COMMAND_DATA
24773 The command is related to data or variables. For example,
24774 @code{call}, @code{find}, and @code{print} are in this category. Type
24775 @kbd{help data} at the @value{GDBN} prompt to see a list of commands
24778 @findex COMMAND_STACK
24779 @findex gdb.COMMAND_STACK
24780 @item gdb.COMMAND_STACK
24781 The command has to do with manipulation of the stack. For example,
24782 @code{backtrace}, @code{frame}, and @code{return} are in this
24783 category. Type @kbd{help stack} at the @value{GDBN} prompt to see a
24784 list of commands in this category.
24786 @findex COMMAND_FILES
24787 @findex gdb.COMMAND_FILES
24788 @item gdb.COMMAND_FILES
24789 This class is used for file-related commands. For example,
24790 @code{file}, @code{list} and @code{section} are in this category.
24791 Type @kbd{help files} at the @value{GDBN} prompt to see a list of
24792 commands in this category.
24794 @findex COMMAND_SUPPORT
24795 @findex gdb.COMMAND_SUPPORT
24796 @item gdb.COMMAND_SUPPORT
24797 This should be used for ``support facilities'', generally meaning
24798 things that are useful to the user when interacting with @value{GDBN},
24799 but not related to the state of the inferior. For example,
24800 @code{help}, @code{make}, and @code{shell} are in this category. Type
24801 @kbd{help support} at the @value{GDBN} prompt to see a list of
24802 commands in this category.
24804 @findex COMMAND_STATUS
24805 @findex gdb.COMMAND_STATUS
24806 @item gdb.COMMAND_STATUS
24807 The command is an @samp{info}-related command, that is, related to the
24808 state of @value{GDBN} itself. For example, @code{info}, @code{macro},
24809 and @code{show} are in this category. Type @kbd{help status} at the
24810 @value{GDBN} prompt to see a list of commands in this category.
24812 @findex COMMAND_BREAKPOINTS
24813 @findex gdb.COMMAND_BREAKPOINTS
24814 @item gdb.COMMAND_BREAKPOINTS
24815 The command has to do with breakpoints. For example, @code{break},
24816 @code{clear}, and @code{delete} are in this category. Type @kbd{help
24817 breakpoints} at the @value{GDBN} prompt to see a list of commands in
24820 @findex COMMAND_TRACEPOINTS
24821 @findex gdb.COMMAND_TRACEPOINTS
24822 @item gdb.COMMAND_TRACEPOINTS
24823 The command has to do with tracepoints. For example, @code{trace},
24824 @code{actions}, and @code{tfind} are in this category. Type
24825 @kbd{help tracepoints} at the @value{GDBN} prompt to see a list of
24826 commands in this category.
24828 @findex COMMAND_USER
24829 @findex gdb.COMMAND_USER
24830 @item gdb.COMMAND_USER
24831 The command is a general purpose command for the user, and typically
24832 does not fit in one of the other categories.
24833 Type @kbd{help user-defined} at the @value{GDBN} prompt to see
24834 a list of commands in this category, as well as the list of gdb macros
24835 (@pxref{Sequences}).
24837 @findex COMMAND_OBSCURE
24838 @findex gdb.COMMAND_OBSCURE
24839 @item gdb.COMMAND_OBSCURE
24840 The command is only used in unusual circumstances, or is not of
24841 general interest to users. For example, @code{checkpoint},
24842 @code{fork}, and @code{stop} are in this category. Type @kbd{help
24843 obscure} at the @value{GDBN} prompt to see a list of commands in this
24846 @findex COMMAND_MAINTENANCE
24847 @findex gdb.COMMAND_MAINTENANCE
24848 @item gdb.COMMAND_MAINTENANCE
24849 The command is only useful to @value{GDBN} maintainers. The
24850 @code{maintenance} and @code{flushregs} commands are in this category.
24851 Type @kbd{help internals} at the @value{GDBN} prompt to see a list of
24852 commands in this category.
24855 A new command can use a predefined completion function, either by
24856 specifying it via an argument at initialization, or by returning it
24857 from the @code{complete} method. These predefined completion
24858 constants are all defined in the @code{gdb} module:
24861 @findex COMPLETE_NONE
24862 @findex gdb.COMPLETE_NONE
24863 @item gdb.COMPLETE_NONE
24864 This constant means that no completion should be done.
24866 @findex COMPLETE_FILENAME
24867 @findex gdb.COMPLETE_FILENAME
24868 @item gdb.COMPLETE_FILENAME
24869 This constant means that filename completion should be performed.
24871 @findex COMPLETE_LOCATION
24872 @findex gdb.COMPLETE_LOCATION
24873 @item gdb.COMPLETE_LOCATION
24874 This constant means that location completion should be done.
24875 @xref{Specify Location}.
24877 @findex COMPLETE_COMMAND
24878 @findex gdb.COMPLETE_COMMAND
24879 @item gdb.COMPLETE_COMMAND
24880 This constant means that completion should examine @value{GDBN}
24883 @findex COMPLETE_SYMBOL
24884 @findex gdb.COMPLETE_SYMBOL
24885 @item gdb.COMPLETE_SYMBOL
24886 This constant means that completion should be done using symbol names
24890 The following code snippet shows how a trivial CLI command can be
24891 implemented in Python:
24894 class HelloWorld (gdb.Command):
24895 """Greet the whole world."""
24897 def __init__ (self):
24898 super (HelloWorld, self).__init__ ("hello-world", gdb.COMMAND_USER)
24900 def invoke (self, arg, from_tty):
24901 print "Hello, World!"
24906 The last line instantiates the class, and is necessary to trigger the
24907 registration of the command with @value{GDBN}. Depending on how the
24908 Python code is read into @value{GDBN}, you may need to import the
24909 @code{gdb} module explicitly.
24911 @node Parameters In Python
24912 @subsubsection Parameters In Python
24914 @cindex parameters in python
24915 @cindex python parameters
24916 @tindex gdb.Parameter
24918 You can implement new @value{GDBN} parameters using Python. A new
24919 parameter is implemented as an instance of the @code{gdb.Parameter}
24922 Parameters are exposed to the user via the @code{set} and
24923 @code{show} commands. @xref{Help}.
24925 There are many parameters that already exist and can be set in
24926 @value{GDBN}. Two examples are: @code{set follow fork} and
24927 @code{set charset}. Setting these parameters influences certain
24928 behavior in @value{GDBN}. Similarly, you can define parameters that
24929 can be used to influence behavior in custom Python scripts and commands.
24931 @defun Parameter.__init__ (name, @var{command-class}, @var{parameter-class} @r{[}, @var{enum-sequence}@r{]})
24932 The object initializer for @code{Parameter} registers the new
24933 parameter with @value{GDBN}. This initializer is normally invoked
24934 from the subclass' own @code{__init__} method.
24936 @var{name} is the name of the new parameter. If @var{name} consists
24937 of multiple words, then the initial words are looked for as prefix
24938 parameters. An example of this can be illustrated with the
24939 @code{set print} set of parameters. If @var{name} is
24940 @code{print foo}, then @code{print} will be searched as the prefix
24941 parameter. In this case the parameter can subsequently be accessed in
24942 @value{GDBN} as @code{set print foo}.
24944 If @var{name} consists of multiple words, and no prefix parameter group
24945 can be found, an exception is raised.
24947 @var{command-class} should be one of the @samp{COMMAND_} constants
24948 (@pxref{Commands In Python}). This argument tells @value{GDBN} how to
24949 categorize the new parameter in the help system.
24951 @var{parameter-class} should be one of the @samp{PARAM_} constants
24952 defined below. This argument tells @value{GDBN} the type of the new
24953 parameter; this information is used for input validation and
24956 If @var{parameter-class} is @code{PARAM_ENUM}, then
24957 @var{enum-sequence} must be a sequence of strings. These strings
24958 represent the possible values for the parameter.
24960 If @var{parameter-class} is not @code{PARAM_ENUM}, then the presence
24961 of a fourth argument will cause an exception to be thrown.
24963 The help text for the new parameter is taken from the Python
24964 documentation string for the parameter's class, if there is one. If
24965 there is no documentation string, a default value is used.
24968 @defvar Parameter.set_doc
24969 If this attribute exists, and is a string, then its value is used as
24970 the help text for this parameter's @code{set} command. The value is
24971 examined when @code{Parameter.__init__} is invoked; subsequent changes
24975 @defvar Parameter.show_doc
24976 If this attribute exists, and is a string, then its value is used as
24977 the help text for this parameter's @code{show} command. The value is
24978 examined when @code{Parameter.__init__} is invoked; subsequent changes
24982 @defvar Parameter.value
24983 The @code{value} attribute holds the underlying value of the
24984 parameter. It can be read and assigned to just as any other
24985 attribute. @value{GDBN} does validation when assignments are made.
24988 There are two methods that should be implemented in any
24989 @code{Parameter} class. These are:
24991 @defun Parameter.get_set_string (self)
24992 @value{GDBN} will call this method when a @var{parameter}'s value has
24993 been changed via the @code{set} API (for example, @kbd{set foo off}).
24994 The @code{value} attribute has already been populated with the new
24995 value and may be used in output. This method must return a string.
24998 @defun Parameter.get_show_string (self, svalue)
24999 @value{GDBN} will call this method when a @var{parameter}'s
25000 @code{show} API has been invoked (for example, @kbd{show foo}). The
25001 argument @code{svalue} receives the string representation of the
25002 current value. This method must return a string.
25005 When a new parameter is defined, its type must be specified. The
25006 available types are represented by constants defined in the @code{gdb}
25010 @findex PARAM_BOOLEAN
25011 @findex gdb.PARAM_BOOLEAN
25012 @item gdb.PARAM_BOOLEAN
25013 The value is a plain boolean. The Python boolean values, @code{True}
25014 and @code{False} are the only valid values.
25016 @findex PARAM_AUTO_BOOLEAN
25017 @findex gdb.PARAM_AUTO_BOOLEAN
25018 @item gdb.PARAM_AUTO_BOOLEAN
25019 The value has three possible states: true, false, and @samp{auto}. In
25020 Python, true and false are represented using boolean constants, and
25021 @samp{auto} is represented using @code{None}.
25023 @findex PARAM_UINTEGER
25024 @findex gdb.PARAM_UINTEGER
25025 @item gdb.PARAM_UINTEGER
25026 The value is an unsigned integer. The value of 0 should be
25027 interpreted to mean ``unlimited''.
25029 @findex PARAM_INTEGER
25030 @findex gdb.PARAM_INTEGER
25031 @item gdb.PARAM_INTEGER
25032 The value is a signed integer. The value of 0 should be interpreted
25033 to mean ``unlimited''.
25035 @findex PARAM_STRING
25036 @findex gdb.PARAM_STRING
25037 @item gdb.PARAM_STRING
25038 The value is a string. When the user modifies the string, any escape
25039 sequences, such as @samp{\t}, @samp{\f}, and octal escapes, are
25040 translated into corresponding characters and encoded into the current
25043 @findex PARAM_STRING_NOESCAPE
25044 @findex gdb.PARAM_STRING_NOESCAPE
25045 @item gdb.PARAM_STRING_NOESCAPE
25046 The value is a string. When the user modifies the string, escapes are
25047 passed through untranslated.
25049 @findex PARAM_OPTIONAL_FILENAME
25050 @findex gdb.PARAM_OPTIONAL_FILENAME
25051 @item gdb.PARAM_OPTIONAL_FILENAME
25052 The value is a either a filename (a string), or @code{None}.
25054 @findex PARAM_FILENAME
25055 @findex gdb.PARAM_FILENAME
25056 @item gdb.PARAM_FILENAME
25057 The value is a filename. This is just like
25058 @code{PARAM_STRING_NOESCAPE}, but uses file names for completion.
25060 @findex PARAM_ZINTEGER
25061 @findex gdb.PARAM_ZINTEGER
25062 @item gdb.PARAM_ZINTEGER
25063 The value is an integer. This is like @code{PARAM_INTEGER}, except 0
25064 is interpreted as itself.
25067 @findex gdb.PARAM_ENUM
25068 @item gdb.PARAM_ENUM
25069 The value is a string, which must be one of a collection string
25070 constants provided when the parameter is created.
25073 @node Functions In Python
25074 @subsubsection Writing new convenience functions
25076 @cindex writing convenience functions
25077 @cindex convenience functions in python
25078 @cindex python convenience functions
25079 @tindex gdb.Function
25081 You can implement new convenience functions (@pxref{Convenience Vars})
25082 in Python. A convenience function is an instance of a subclass of the
25083 class @code{gdb.Function}.
25085 @defun Function.__init__ (name)
25086 The initializer for @code{Function} registers the new function with
25087 @value{GDBN}. The argument @var{name} is the name of the function,
25088 a string. The function will be visible to the user as a convenience
25089 variable of type @code{internal function}, whose name is the same as
25090 the given @var{name}.
25092 The documentation for the new function is taken from the documentation
25093 string for the new class.
25096 @defun Function.invoke (@var{*args})
25097 When a convenience function is evaluated, its arguments are converted
25098 to instances of @code{gdb.Value}, and then the function's
25099 @code{invoke} method is called. Note that @value{GDBN} does not
25100 predetermine the arity of convenience functions. Instead, all
25101 available arguments are passed to @code{invoke}, following the
25102 standard Python calling convention. In particular, a convenience
25103 function can have default values for parameters without ill effect.
25105 The return value of this method is used as its value in the enclosing
25106 expression. If an ordinary Python value is returned, it is converted
25107 to a @code{gdb.Value} following the usual rules.
25110 The following code snippet shows how a trivial convenience function can
25111 be implemented in Python:
25114 class Greet (gdb.Function):
25115 """Return string to greet someone.
25116 Takes a name as argument."""
25118 def __init__ (self):
25119 super (Greet, self).__init__ ("greet")
25121 def invoke (self, name):
25122 return "Hello, %s!" % name.string ()
25127 The last line instantiates the class, and is necessary to trigger the
25128 registration of the function with @value{GDBN}. Depending on how the
25129 Python code is read into @value{GDBN}, you may need to import the
25130 @code{gdb} module explicitly.
25132 Now you can use the function in an expression:
25135 (gdb) print $greet("Bob")
25139 @node Progspaces In Python
25140 @subsubsection Program Spaces In Python
25142 @cindex progspaces in python
25143 @tindex gdb.Progspace
25145 A program space, or @dfn{progspace}, represents a symbolic view
25146 of an address space.
25147 It consists of all of the objfiles of the program.
25148 @xref{Objfiles In Python}.
25149 @xref{Inferiors and Programs, program spaces}, for more details
25150 about program spaces.
25152 The following progspace-related functions are available in the
25155 @findex gdb.current_progspace
25156 @defun gdb.current_progspace ()
25157 This function returns the program space of the currently selected inferior.
25158 @xref{Inferiors and Programs}.
25161 @findex gdb.progspaces
25162 @defun gdb.progspaces ()
25163 Return a sequence of all the progspaces currently known to @value{GDBN}.
25166 Each progspace is represented by an instance of the @code{gdb.Progspace}
25169 @defvar Progspace.filename
25170 The file name of the progspace as a string.
25173 @defvar Progspace.pretty_printers
25174 The @code{pretty_printers} attribute is a list of functions. It is
25175 used to look up pretty-printers. A @code{Value} is passed to each
25176 function in order; if the function returns @code{None}, then the
25177 search continues. Otherwise, the return value should be an object
25178 which is used to format the value. @xref{Pretty Printing API}, for more
25182 @defvar Progspace.type_printers
25183 The @code{type_printers} attribute is a list of type printer objects.
25184 @xref{Type Printing API}, for more information.
25187 @node Objfiles In Python
25188 @subsubsection Objfiles In Python
25190 @cindex objfiles in python
25191 @tindex gdb.Objfile
25193 @value{GDBN} loads symbols for an inferior from various
25194 symbol-containing files (@pxref{Files}). These include the primary
25195 executable file, any shared libraries used by the inferior, and any
25196 separate debug info files (@pxref{Separate Debug Files}).
25197 @value{GDBN} calls these symbol-containing files @dfn{objfiles}.
25199 The following objfile-related functions are available in the
25202 @findex gdb.current_objfile
25203 @defun gdb.current_objfile ()
25204 When auto-loading a Python script (@pxref{Python Auto-loading}), @value{GDBN}
25205 sets the ``current objfile'' to the corresponding objfile. This
25206 function returns the current objfile. If there is no current objfile,
25207 this function returns @code{None}.
25210 @findex gdb.objfiles
25211 @defun gdb.objfiles ()
25212 Return a sequence of all the objfiles current known to @value{GDBN}.
25213 @xref{Objfiles In Python}.
25216 Each objfile is represented by an instance of the @code{gdb.Objfile}
25219 @defvar Objfile.filename
25220 The file name of the objfile as a string.
25223 @defvar Objfile.pretty_printers
25224 The @code{pretty_printers} attribute is a list of functions. It is
25225 used to look up pretty-printers. A @code{Value} is passed to each
25226 function in order; if the function returns @code{None}, then the
25227 search continues. Otherwise, the return value should be an object
25228 which is used to format the value. @xref{Pretty Printing API}, for more
25232 @defvar Objfile.type_printers
25233 The @code{type_printers} attribute is a list of type printer objects.
25234 @xref{Type Printing API}, for more information.
25237 A @code{gdb.Objfile} object has the following methods:
25239 @defun Objfile.is_valid ()
25240 Returns @code{True} if the @code{gdb.Objfile} object is valid,
25241 @code{False} if not. A @code{gdb.Objfile} object can become invalid
25242 if the object file it refers to is not loaded in @value{GDBN} any
25243 longer. All other @code{gdb.Objfile} methods will throw an exception
25244 if it is invalid at the time the method is called.
25247 @node Frames In Python
25248 @subsubsection Accessing inferior stack frames from Python.
25250 @cindex frames in python
25251 When the debugged program stops, @value{GDBN} is able to analyze its call
25252 stack (@pxref{Frames,,Stack frames}). The @code{gdb.Frame} class
25253 represents a frame in the stack. A @code{gdb.Frame} object is only valid
25254 while its corresponding frame exists in the inferior's stack. If you try
25255 to use an invalid frame object, @value{GDBN} will throw a @code{gdb.error}
25256 exception (@pxref{Exception Handling}).
25258 Two @code{gdb.Frame} objects can be compared for equality with the @code{==}
25262 (@value{GDBP}) python print gdb.newest_frame() == gdb.selected_frame ()
25266 The following frame-related functions are available in the @code{gdb} module:
25268 @findex gdb.selected_frame
25269 @defun gdb.selected_frame ()
25270 Return the selected frame object. (@pxref{Selection,,Selecting a Frame}).
25273 @findex gdb.newest_frame
25274 @defun gdb.newest_frame ()
25275 Return the newest frame object for the selected thread.
25278 @defun gdb.frame_stop_reason_string (reason)
25279 Return a string explaining the reason why @value{GDBN} stopped unwinding
25280 frames, as expressed by the given @var{reason} code (an integer, see the
25281 @code{unwind_stop_reason} method further down in this section).
25284 A @code{gdb.Frame} object has the following methods:
25286 @defun Frame.is_valid ()
25287 Returns true if the @code{gdb.Frame} object is valid, false if not.
25288 A frame object can become invalid if the frame it refers to doesn't
25289 exist anymore in the inferior. All @code{gdb.Frame} methods will throw
25290 an exception if it is invalid at the time the method is called.
25293 @defun Frame.name ()
25294 Returns the function name of the frame, or @code{None} if it can't be
25298 @defun Frame.architecture ()
25299 Returns the @code{gdb.Architecture} object corresponding to the frame's
25300 architecture. @xref{Architectures In Python}.
25303 @defun Frame.type ()
25304 Returns the type of the frame. The value can be one of:
25306 @item gdb.NORMAL_FRAME
25307 An ordinary stack frame.
25309 @item gdb.DUMMY_FRAME
25310 A fake stack frame that was created by @value{GDBN} when performing an
25311 inferior function call.
25313 @item gdb.INLINE_FRAME
25314 A frame representing an inlined function. The function was inlined
25315 into a @code{gdb.NORMAL_FRAME} that is older than this one.
25317 @item gdb.TAILCALL_FRAME
25318 A frame representing a tail call. @xref{Tail Call Frames}.
25320 @item gdb.SIGTRAMP_FRAME
25321 A signal trampoline frame. This is the frame created by the OS when
25322 it calls into a signal handler.
25324 @item gdb.ARCH_FRAME
25325 A fake stack frame representing a cross-architecture call.
25327 @item gdb.SENTINEL_FRAME
25328 This is like @code{gdb.NORMAL_FRAME}, but it is only used for the
25333 @defun Frame.unwind_stop_reason ()
25334 Return an integer representing the reason why it's not possible to find
25335 more frames toward the outermost frame. Use
25336 @code{gdb.frame_stop_reason_string} to convert the value returned by this
25337 function to a string. The value can be one of:
25340 @item gdb.FRAME_UNWIND_NO_REASON
25341 No particular reason (older frames should be available).
25343 @item gdb.FRAME_UNWIND_NULL_ID
25344 The previous frame's analyzer returns an invalid result.
25346 @item gdb.FRAME_UNWIND_OUTERMOST
25347 This frame is the outermost.
25349 @item gdb.FRAME_UNWIND_UNAVAILABLE
25350 Cannot unwind further, because that would require knowing the
25351 values of registers or memory that have not been collected.
25353 @item gdb.FRAME_UNWIND_INNER_ID
25354 This frame ID looks like it ought to belong to a NEXT frame,
25355 but we got it for a PREV frame. Normally, this is a sign of
25356 unwinder failure. It could also indicate stack corruption.
25358 @item gdb.FRAME_UNWIND_SAME_ID
25359 This frame has the same ID as the previous one. That means
25360 that unwinding further would almost certainly give us another
25361 frame with exactly the same ID, so break the chain. Normally,
25362 this is a sign of unwinder failure. It could also indicate
25365 @item gdb.FRAME_UNWIND_NO_SAVED_PC
25366 The frame unwinder did not find any saved PC, but we needed
25367 one to unwind further.
25369 @item gdb.FRAME_UNWIND_FIRST_ERROR
25370 Any stop reason greater or equal to this value indicates some kind
25371 of error. This special value facilitates writing code that tests
25372 for errors in unwinding in a way that will work correctly even if
25373 the list of the other values is modified in future @value{GDBN}
25374 versions. Using it, you could write:
25376 reason = gdb.selected_frame().unwind_stop_reason ()
25377 reason_str = gdb.frame_stop_reason_string (reason)
25378 if reason >= gdb.FRAME_UNWIND_FIRST_ERROR:
25379 print "An error occured: %s" % reason_str
25386 Returns the frame's resume address.
25389 @defun Frame.block ()
25390 Return the frame's code block. @xref{Blocks In Python}.
25393 @defun Frame.function ()
25394 Return the symbol for the function corresponding to this frame.
25395 @xref{Symbols In Python}.
25398 @defun Frame.older ()
25399 Return the frame that called this frame.
25402 @defun Frame.newer ()
25403 Return the frame called by this frame.
25406 @defun Frame.find_sal ()
25407 Return the frame's symtab and line object.
25408 @xref{Symbol Tables In Python}.
25411 @defun Frame.read_var (variable @r{[}, block@r{]})
25412 Return the value of @var{variable} in this frame. If the optional
25413 argument @var{block} is provided, search for the variable from that
25414 block; otherwise start at the frame's current block (which is
25415 determined by the frame's current program counter). @var{variable}
25416 must be a string or a @code{gdb.Symbol} object. @var{block} must be a
25417 @code{gdb.Block} object.
25420 @defun Frame.select ()
25421 Set this frame to be the selected frame. @xref{Stack, ,Examining the
25425 @node Blocks In Python
25426 @subsubsection Accessing frame blocks from Python.
25428 @cindex blocks in python
25431 Within each frame, @value{GDBN} maintains information on each block
25432 stored in that frame. These blocks are organized hierarchically, and
25433 are represented individually in Python as a @code{gdb.Block}.
25434 Please see @ref{Frames In Python}, for a more in-depth discussion on
25435 frames. Furthermore, see @ref{Stack, ,Examining the Stack}, for more
25436 detailed technical information on @value{GDBN}'s book-keeping of the
25439 A @code{gdb.Block} is iterable. The iterator returns the symbols
25440 (@pxref{Symbols In Python}) local to the block. Python programs
25441 should not assume that a specific block object will always contain a
25442 given symbol, since changes in @value{GDBN} features and
25443 infrastructure may cause symbols move across blocks in a symbol
25446 The following block-related functions are available in the @code{gdb}
25449 @findex gdb.block_for_pc
25450 @defun gdb.block_for_pc (pc)
25451 Return the @code{gdb.Block} containing the given @var{pc} value. If the
25452 block cannot be found for the @var{pc} value specified, the function
25453 will return @code{None}.
25456 A @code{gdb.Block} object has the following methods:
25458 @defun Block.is_valid ()
25459 Returns @code{True} if the @code{gdb.Block} object is valid,
25460 @code{False} if not. A block object can become invalid if the block it
25461 refers to doesn't exist anymore in the inferior. All other
25462 @code{gdb.Block} methods will throw an exception if it is invalid at
25463 the time the method is called. The block's validity is also checked
25464 during iteration over symbols of the block.
25467 A @code{gdb.Block} object has the following attributes:
25469 @defvar Block.start
25470 The start address of the block. This attribute is not writable.
25474 The end address of the block. This attribute is not writable.
25477 @defvar Block.function
25478 The name of the block represented as a @code{gdb.Symbol}. If the
25479 block is not named, then this attribute holds @code{None}. This
25480 attribute is not writable.
25483 @defvar Block.superblock
25484 The block containing this block. If this parent block does not exist,
25485 this attribute holds @code{None}. This attribute is not writable.
25488 @defvar Block.global_block
25489 The global block associated with this block. This attribute is not
25493 @defvar Block.static_block
25494 The static block associated with this block. This attribute is not
25498 @defvar Block.is_global
25499 @code{True} if the @code{gdb.Block} object is a global block,
25500 @code{False} if not. This attribute is not
25504 @defvar Block.is_static
25505 @code{True} if the @code{gdb.Block} object is a static block,
25506 @code{False} if not. This attribute is not writable.
25509 @node Symbols In Python
25510 @subsubsection Python representation of Symbols.
25512 @cindex symbols in python
25515 @value{GDBN} represents every variable, function and type as an
25516 entry in a symbol table. @xref{Symbols, ,Examining the Symbol Table}.
25517 Similarly, Python represents these symbols in @value{GDBN} with the
25518 @code{gdb.Symbol} object.
25520 The following symbol-related functions are available in the @code{gdb}
25523 @findex gdb.lookup_symbol
25524 @defun gdb.lookup_symbol (name @r{[}, block @r{[}, domain@r{]]})
25525 This function searches for a symbol by name. The search scope can be
25526 restricted to the parameters defined in the optional domain and block
25529 @var{name} is the name of the symbol. It must be a string. The
25530 optional @var{block} argument restricts the search to symbols visible
25531 in that @var{block}. The @var{block} argument must be a
25532 @code{gdb.Block} object. If omitted, the block for the current frame
25533 is used. The optional @var{domain} argument restricts
25534 the search to the domain type. The @var{domain} argument must be a
25535 domain constant defined in the @code{gdb} module and described later
25538 The result is a tuple of two elements.
25539 The first element is a @code{gdb.Symbol} object or @code{None} if the symbol
25541 If the symbol is found, the second element is @code{True} if the symbol
25542 is a field of a method's object (e.g., @code{this} in C@t{++}),
25543 otherwise it is @code{False}.
25544 If the symbol is not found, the second element is @code{False}.
25547 @findex gdb.lookup_global_symbol
25548 @defun gdb.lookup_global_symbol (name @r{[}, domain@r{]})
25549 This function searches for a global symbol by name.
25550 The search scope can be restricted to by the domain argument.
25552 @var{name} is the name of the symbol. It must be a string.
25553 The optional @var{domain} argument restricts the search to the domain type.
25554 The @var{domain} argument must be a domain constant defined in the @code{gdb}
25555 module and described later in this chapter.
25557 The result is a @code{gdb.Symbol} object or @code{None} if the symbol
25561 A @code{gdb.Symbol} object has the following attributes:
25563 @defvar Symbol.type
25564 The type of the symbol or @code{None} if no type is recorded.
25565 This attribute is represented as a @code{gdb.Type} object.
25566 @xref{Types In Python}. This attribute is not writable.
25569 @defvar Symbol.symtab
25570 The symbol table in which the symbol appears. This attribute is
25571 represented as a @code{gdb.Symtab} object. @xref{Symbol Tables In
25572 Python}. This attribute is not writable.
25575 @defvar Symbol.line
25576 The line number in the source code at which the symbol was defined.
25577 This is an integer.
25580 @defvar Symbol.name
25581 The name of the symbol as a string. This attribute is not writable.
25584 @defvar Symbol.linkage_name
25585 The name of the symbol, as used by the linker (i.e., may be mangled).
25586 This attribute is not writable.
25589 @defvar Symbol.print_name
25590 The name of the symbol in a form suitable for output. This is either
25591 @code{name} or @code{linkage_name}, depending on whether the user
25592 asked @value{GDBN} to display demangled or mangled names.
25595 @defvar Symbol.addr_class
25596 The address class of the symbol. This classifies how to find the value
25597 of a symbol. Each address class is a constant defined in the
25598 @code{gdb} module and described later in this chapter.
25601 @defvar Symbol.needs_frame
25602 This is @code{True} if evaluating this symbol's value requires a frame
25603 (@pxref{Frames In Python}) and @code{False} otherwise. Typically,
25604 local variables will require a frame, but other symbols will not.
25607 @defvar Symbol.is_argument
25608 @code{True} if the symbol is an argument of a function.
25611 @defvar Symbol.is_constant
25612 @code{True} if the symbol is a constant.
25615 @defvar Symbol.is_function
25616 @code{True} if the symbol is a function or a method.
25619 @defvar Symbol.is_variable
25620 @code{True} if the symbol is a variable.
25623 A @code{gdb.Symbol} object has the following methods:
25625 @defun Symbol.is_valid ()
25626 Returns @code{True} if the @code{gdb.Symbol} object is valid,
25627 @code{False} if not. A @code{gdb.Symbol} object can become invalid if
25628 the symbol it refers to does not exist in @value{GDBN} any longer.
25629 All other @code{gdb.Symbol} methods will throw an exception if it is
25630 invalid at the time the method is called.
25633 @defun Symbol.value (@r{[}frame@r{]})
25634 Compute the value of the symbol, as a @code{gdb.Value}. For
25635 functions, this computes the address of the function, cast to the
25636 appropriate type. If the symbol requires a frame in order to compute
25637 its value, then @var{frame} must be given. If @var{frame} is not
25638 given, or if @var{frame} is invalid, then this method will throw an
25642 The available domain categories in @code{gdb.Symbol} are represented
25643 as constants in the @code{gdb} module:
25646 @findex SYMBOL_UNDEF_DOMAIN
25647 @findex gdb.SYMBOL_UNDEF_DOMAIN
25648 @item gdb.SYMBOL_UNDEF_DOMAIN
25649 This is used when a domain has not been discovered or none of the
25650 following domains apply. This usually indicates an error either
25651 in the symbol information or in @value{GDBN}'s handling of symbols.
25652 @findex SYMBOL_VAR_DOMAIN
25653 @findex gdb.SYMBOL_VAR_DOMAIN
25654 @item gdb.SYMBOL_VAR_DOMAIN
25655 This domain contains variables, function names, typedef names and enum
25657 @findex SYMBOL_STRUCT_DOMAIN
25658 @findex gdb.SYMBOL_STRUCT_DOMAIN
25659 @item gdb.SYMBOL_STRUCT_DOMAIN
25660 This domain holds struct, union and enum type names.
25661 @findex SYMBOL_LABEL_DOMAIN
25662 @findex gdb.SYMBOL_LABEL_DOMAIN
25663 @item gdb.SYMBOL_LABEL_DOMAIN
25664 This domain contains names of labels (for gotos).
25665 @findex SYMBOL_VARIABLES_DOMAIN
25666 @findex gdb.SYMBOL_VARIABLES_DOMAIN
25667 @item gdb.SYMBOL_VARIABLES_DOMAIN
25668 This domain holds a subset of the @code{SYMBOLS_VAR_DOMAIN}; it
25669 contains everything minus functions and types.
25670 @findex SYMBOL_FUNCTIONS_DOMAIN
25671 @findex gdb.SYMBOL_FUNCTIONS_DOMAIN
25672 @item gdb.SYMBOL_FUNCTION_DOMAIN
25673 This domain contains all functions.
25674 @findex SYMBOL_TYPES_DOMAIN
25675 @findex gdb.SYMBOL_TYPES_DOMAIN
25676 @item gdb.SYMBOL_TYPES_DOMAIN
25677 This domain contains all types.
25680 The available address class categories in @code{gdb.Symbol} are represented
25681 as constants in the @code{gdb} module:
25684 @findex SYMBOL_LOC_UNDEF
25685 @findex gdb.SYMBOL_LOC_UNDEF
25686 @item gdb.SYMBOL_LOC_UNDEF
25687 If this is returned by address class, it indicates an error either in
25688 the symbol information or in @value{GDBN}'s handling of symbols.
25689 @findex SYMBOL_LOC_CONST
25690 @findex gdb.SYMBOL_LOC_CONST
25691 @item gdb.SYMBOL_LOC_CONST
25692 Value is constant int.
25693 @findex SYMBOL_LOC_STATIC
25694 @findex gdb.SYMBOL_LOC_STATIC
25695 @item gdb.SYMBOL_LOC_STATIC
25696 Value is at a fixed address.
25697 @findex SYMBOL_LOC_REGISTER
25698 @findex gdb.SYMBOL_LOC_REGISTER
25699 @item gdb.SYMBOL_LOC_REGISTER
25700 Value is in a register.
25701 @findex SYMBOL_LOC_ARG
25702 @findex gdb.SYMBOL_LOC_ARG
25703 @item gdb.SYMBOL_LOC_ARG
25704 Value is an argument. This value is at the offset stored within the
25705 symbol inside the frame's argument list.
25706 @findex SYMBOL_LOC_REF_ARG
25707 @findex gdb.SYMBOL_LOC_REF_ARG
25708 @item gdb.SYMBOL_LOC_REF_ARG
25709 Value address is stored in the frame's argument list. Just like
25710 @code{LOC_ARG} except that the value's address is stored at the
25711 offset, not the value itself.
25712 @findex SYMBOL_LOC_REGPARM_ADDR
25713 @findex gdb.SYMBOL_LOC_REGPARM_ADDR
25714 @item gdb.SYMBOL_LOC_REGPARM_ADDR
25715 Value is a specified register. Just like @code{LOC_REGISTER} except
25716 the register holds the address of the argument instead of the argument
25718 @findex SYMBOL_LOC_LOCAL
25719 @findex gdb.SYMBOL_LOC_LOCAL
25720 @item gdb.SYMBOL_LOC_LOCAL
25721 Value is a local variable.
25722 @findex SYMBOL_LOC_TYPEDEF
25723 @findex gdb.SYMBOL_LOC_TYPEDEF
25724 @item gdb.SYMBOL_LOC_TYPEDEF
25725 Value not used. Symbols in the domain @code{SYMBOL_STRUCT_DOMAIN} all
25727 @findex SYMBOL_LOC_BLOCK
25728 @findex gdb.SYMBOL_LOC_BLOCK
25729 @item gdb.SYMBOL_LOC_BLOCK
25731 @findex SYMBOL_LOC_CONST_BYTES
25732 @findex gdb.SYMBOL_LOC_CONST_BYTES
25733 @item gdb.SYMBOL_LOC_CONST_BYTES
25734 Value is a byte-sequence.
25735 @findex SYMBOL_LOC_UNRESOLVED
25736 @findex gdb.SYMBOL_LOC_UNRESOLVED
25737 @item gdb.SYMBOL_LOC_UNRESOLVED
25738 Value is at a fixed address, but the address of the variable has to be
25739 determined from the minimal symbol table whenever the variable is
25741 @findex SYMBOL_LOC_OPTIMIZED_OUT
25742 @findex gdb.SYMBOL_LOC_OPTIMIZED_OUT
25743 @item gdb.SYMBOL_LOC_OPTIMIZED_OUT
25744 The value does not actually exist in the program.
25745 @findex SYMBOL_LOC_COMPUTED
25746 @findex gdb.SYMBOL_LOC_COMPUTED
25747 @item gdb.SYMBOL_LOC_COMPUTED
25748 The value's address is a computed location.
25751 @node Symbol Tables In Python
25752 @subsubsection Symbol table representation in Python.
25754 @cindex symbol tables in python
25756 @tindex gdb.Symtab_and_line
25758 Access to symbol table data maintained by @value{GDBN} on the inferior
25759 is exposed to Python via two objects: @code{gdb.Symtab_and_line} and
25760 @code{gdb.Symtab}. Symbol table and line data for a frame is returned
25761 from the @code{find_sal} method in @code{gdb.Frame} object.
25762 @xref{Frames In Python}.
25764 For more information on @value{GDBN}'s symbol table management, see
25765 @ref{Symbols, ,Examining the Symbol Table}, for more information.
25767 A @code{gdb.Symtab_and_line} object has the following attributes:
25769 @defvar Symtab_and_line.symtab
25770 The symbol table object (@code{gdb.Symtab}) for this frame.
25771 This attribute is not writable.
25774 @defvar Symtab_and_line.pc
25775 Indicates the start of the address range occupied by code for the
25776 current source line. This attribute is not writable.
25779 @defvar Symtab_and_line.last
25780 Indicates the end of the address range occupied by code for the current
25781 source line. This attribute is not writable.
25784 @defvar Symtab_and_line.line
25785 Indicates the current line number for this object. This
25786 attribute is not writable.
25789 A @code{gdb.Symtab_and_line} object has the following methods:
25791 @defun Symtab_and_line.is_valid ()
25792 Returns @code{True} if the @code{gdb.Symtab_and_line} object is valid,
25793 @code{False} if not. A @code{gdb.Symtab_and_line} object can become
25794 invalid if the Symbol table and line object it refers to does not
25795 exist in @value{GDBN} any longer. All other
25796 @code{gdb.Symtab_and_line} methods will throw an exception if it is
25797 invalid at the time the method is called.
25800 A @code{gdb.Symtab} object has the following attributes:
25802 @defvar Symtab.filename
25803 The symbol table's source filename. This attribute is not writable.
25806 @defvar Symtab.objfile
25807 The symbol table's backing object file. @xref{Objfiles In Python}.
25808 This attribute is not writable.
25811 A @code{gdb.Symtab} object has the following methods:
25813 @defun Symtab.is_valid ()
25814 Returns @code{True} if the @code{gdb.Symtab} object is valid,
25815 @code{False} if not. A @code{gdb.Symtab} object can become invalid if
25816 the symbol table it refers to does not exist in @value{GDBN} any
25817 longer. All other @code{gdb.Symtab} methods will throw an exception
25818 if it is invalid at the time the method is called.
25821 @defun Symtab.fullname ()
25822 Return the symbol table's source absolute file name.
25825 @defun Symtab.global_block ()
25826 Return the global block of the underlying symbol table.
25827 @xref{Blocks In Python}.
25830 @defun Symtab.static_block ()
25831 Return the static block of the underlying symbol table.
25832 @xref{Blocks In Python}.
25835 @node Breakpoints In Python
25836 @subsubsection Manipulating breakpoints using Python
25838 @cindex breakpoints in python
25839 @tindex gdb.Breakpoint
25841 Python code can manipulate breakpoints via the @code{gdb.Breakpoint}
25844 @defun Breakpoint.__init__ (spec @r{[}, type @r{[}, wp_class @r{[},internal@r{]]]})
25845 Create a new breakpoint. @var{spec} is a string naming the
25846 location of the breakpoint, or an expression that defines a
25847 watchpoint. The contents can be any location recognized by the
25848 @code{break} command, or in the case of a watchpoint, by the @code{watch}
25849 command. The optional @var{type} denotes the breakpoint to create
25850 from the types defined later in this chapter. This argument can be
25851 either: @code{gdb.BP_BREAKPOINT} or @code{gdb.BP_WATCHPOINT}. @var{type}
25852 defaults to @code{gdb.BP_BREAKPOINT}. The optional @var{internal} argument
25853 allows the breakpoint to become invisible to the user. The breakpoint
25854 will neither be reported when created, nor will it be listed in the
25855 output from @code{info breakpoints} (but will be listed with the
25856 @code{maint info breakpoints} command). The optional @var{wp_class}
25857 argument defines the class of watchpoint to create, if @var{type} is
25858 @code{gdb.BP_WATCHPOINT}. If a watchpoint class is not provided, it is
25859 assumed to be a @code{gdb.WP_WRITE} class.
25862 @defun Breakpoint.stop (self)
25863 The @code{gdb.Breakpoint} class can be sub-classed and, in
25864 particular, you may choose to implement the @code{stop} method.
25865 If this method is defined as a sub-class of @code{gdb.Breakpoint},
25866 it will be called when the inferior reaches any location of a
25867 breakpoint which instantiates that sub-class. If the method returns
25868 @code{True}, the inferior will be stopped at the location of the
25869 breakpoint, otherwise the inferior will continue.
25871 If there are multiple breakpoints at the same location with a
25872 @code{stop} method, each one will be called regardless of the
25873 return status of the previous. This ensures that all @code{stop}
25874 methods have a chance to execute at that location. In this scenario
25875 if one of the methods returns @code{True} but the others return
25876 @code{False}, the inferior will still be stopped.
25878 You should not alter the execution state of the inferior (i.e.@:, step,
25879 next, etc.), alter the current frame context (i.e.@:, change the current
25880 active frame), or alter, add or delete any breakpoint. As a general
25881 rule, you should not alter any data within @value{GDBN} or the inferior
25884 Example @code{stop} implementation:
25887 class MyBreakpoint (gdb.Breakpoint):
25889 inf_val = gdb.parse_and_eval("foo")
25896 The available watchpoint types represented by constants are defined in the
25901 @findex gdb.WP_READ
25903 Read only watchpoint.
25906 @findex gdb.WP_WRITE
25908 Write only watchpoint.
25911 @findex gdb.WP_ACCESS
25912 @item gdb.WP_ACCESS
25913 Read/Write watchpoint.
25916 @defun Breakpoint.is_valid ()
25917 Return @code{True} if this @code{Breakpoint} object is valid,
25918 @code{False} otherwise. A @code{Breakpoint} object can become invalid
25919 if the user deletes the breakpoint. In this case, the object still
25920 exists, but the underlying breakpoint does not. In the cases of
25921 watchpoint scope, the watchpoint remains valid even if execution of the
25922 inferior leaves the scope of that watchpoint.
25925 @defun Breakpoint.delete
25926 Permanently deletes the @value{GDBN} breakpoint. This also
25927 invalidates the Python @code{Breakpoint} object. Any further access
25928 to this object's attributes or methods will raise an error.
25931 @defvar Breakpoint.enabled
25932 This attribute is @code{True} if the breakpoint is enabled, and
25933 @code{False} otherwise. This attribute is writable.
25936 @defvar Breakpoint.silent
25937 This attribute is @code{True} if the breakpoint is silent, and
25938 @code{False} otherwise. This attribute is writable.
25940 Note that a breakpoint can also be silent if it has commands and the
25941 first command is @code{silent}. This is not reported by the
25942 @code{silent} attribute.
25945 @defvar Breakpoint.thread
25946 If the breakpoint is thread-specific, this attribute holds the thread
25947 id. If the breakpoint is not thread-specific, this attribute is
25948 @code{None}. This attribute is writable.
25951 @defvar Breakpoint.task
25952 If the breakpoint is Ada task-specific, this attribute holds the Ada task
25953 id. If the breakpoint is not task-specific (or the underlying
25954 language is not Ada), this attribute is @code{None}. This attribute
25958 @defvar Breakpoint.ignore_count
25959 This attribute holds the ignore count for the breakpoint, an integer.
25960 This attribute is writable.
25963 @defvar Breakpoint.number
25964 This attribute holds the breakpoint's number --- the identifier used by
25965 the user to manipulate the breakpoint. This attribute is not writable.
25968 @defvar Breakpoint.type
25969 This attribute holds the breakpoint's type --- the identifier used to
25970 determine the actual breakpoint type or use-case. This attribute is not
25974 @defvar Breakpoint.visible
25975 This attribute tells whether the breakpoint is visible to the user
25976 when set, or when the @samp{info breakpoints} command is run. This
25977 attribute is not writable.
25980 The available types are represented by constants defined in the @code{gdb}
25984 @findex BP_BREAKPOINT
25985 @findex gdb.BP_BREAKPOINT
25986 @item gdb.BP_BREAKPOINT
25987 Normal code breakpoint.
25989 @findex BP_WATCHPOINT
25990 @findex gdb.BP_WATCHPOINT
25991 @item gdb.BP_WATCHPOINT
25992 Watchpoint breakpoint.
25994 @findex BP_HARDWARE_WATCHPOINT
25995 @findex gdb.BP_HARDWARE_WATCHPOINT
25996 @item gdb.BP_HARDWARE_WATCHPOINT
25997 Hardware assisted watchpoint.
25999 @findex BP_READ_WATCHPOINT
26000 @findex gdb.BP_READ_WATCHPOINT
26001 @item gdb.BP_READ_WATCHPOINT
26002 Hardware assisted read watchpoint.
26004 @findex BP_ACCESS_WATCHPOINT
26005 @findex gdb.BP_ACCESS_WATCHPOINT
26006 @item gdb.BP_ACCESS_WATCHPOINT
26007 Hardware assisted access watchpoint.
26010 @defvar Breakpoint.hit_count
26011 This attribute holds the hit count for the breakpoint, an integer.
26012 This attribute is writable, but currently it can only be set to zero.
26015 @defvar Breakpoint.location
26016 This attribute holds the location of the breakpoint, as specified by
26017 the user. It is a string. If the breakpoint does not have a location
26018 (that is, it is a watchpoint) the attribute's value is @code{None}. This
26019 attribute is not writable.
26022 @defvar Breakpoint.expression
26023 This attribute holds a breakpoint expression, as specified by
26024 the user. It is a string. If the breakpoint does not have an
26025 expression (the breakpoint is not a watchpoint) the attribute's value
26026 is @code{None}. This attribute is not writable.
26029 @defvar Breakpoint.condition
26030 This attribute holds the condition of the breakpoint, as specified by
26031 the user. It is a string. If there is no condition, this attribute's
26032 value is @code{None}. This attribute is writable.
26035 @defvar Breakpoint.commands
26036 This attribute holds the commands attached to the breakpoint. If
26037 there are commands, this attribute's value is a string holding all the
26038 commands, separated by newlines. If there are no commands, this
26039 attribute is @code{None}. This attribute is not writable.
26042 @node Finish Breakpoints in Python
26043 @subsubsection Finish Breakpoints
26045 @cindex python finish breakpoints
26046 @tindex gdb.FinishBreakpoint
26048 A finish breakpoint is a temporary breakpoint set at the return address of
26049 a frame, based on the @code{finish} command. @code{gdb.FinishBreakpoint}
26050 extends @code{gdb.Breakpoint}. The underlying breakpoint will be disabled
26051 and deleted when the execution will run out of the breakpoint scope (i.e.@:
26052 @code{Breakpoint.stop} or @code{FinishBreakpoint.out_of_scope} triggered).
26053 Finish breakpoints are thread specific and must be create with the right
26056 @defun FinishBreakpoint.__init__ (@r{[}frame@r{]} @r{[}, internal@r{]})
26057 Create a finish breakpoint at the return address of the @code{gdb.Frame}
26058 object @var{frame}. If @var{frame} is not provided, this defaults to the
26059 newest frame. The optional @var{internal} argument allows the breakpoint to
26060 become invisible to the user. @xref{Breakpoints In Python}, for further
26061 details about this argument.
26064 @defun FinishBreakpoint.out_of_scope (self)
26065 In some circumstances (e.g.@: @code{longjmp}, C@t{++} exceptions, @value{GDBN}
26066 @code{return} command, @dots{}), a function may not properly terminate, and
26067 thus never hit the finish breakpoint. When @value{GDBN} notices such a
26068 situation, the @code{out_of_scope} callback will be triggered.
26070 You may want to sub-class @code{gdb.FinishBreakpoint} and override this
26074 class MyFinishBreakpoint (gdb.FinishBreakpoint)
26076 print "normal finish"
26079 def out_of_scope ():
26080 print "abnormal finish"
26084 @defvar FinishBreakpoint.return_value
26085 When @value{GDBN} is stopped at a finish breakpoint and the frame
26086 used to build the @code{gdb.FinishBreakpoint} object had debug symbols, this
26087 attribute will contain a @code{gdb.Value} object corresponding to the return
26088 value of the function. The value will be @code{None} if the function return
26089 type is @code{void} or if the return value was not computable. This attribute
26093 @node Lazy Strings In Python
26094 @subsubsection Python representation of lazy strings.
26096 @cindex lazy strings in python
26097 @tindex gdb.LazyString
26099 A @dfn{lazy string} is a string whose contents is not retrieved or
26100 encoded until it is needed.
26102 A @code{gdb.LazyString} is represented in @value{GDBN} as an
26103 @code{address} that points to a region of memory, an @code{encoding}
26104 that will be used to encode that region of memory, and a @code{length}
26105 to delimit the region of memory that represents the string. The
26106 difference between a @code{gdb.LazyString} and a string wrapped within
26107 a @code{gdb.Value} is that a @code{gdb.LazyString} will be treated
26108 differently by @value{GDBN} when printing. A @code{gdb.LazyString} is
26109 retrieved and encoded during printing, while a @code{gdb.Value}
26110 wrapping a string is immediately retrieved and encoded on creation.
26112 A @code{gdb.LazyString} object has the following functions:
26114 @defun LazyString.value ()
26115 Convert the @code{gdb.LazyString} to a @code{gdb.Value}. This value
26116 will point to the string in memory, but will lose all the delayed
26117 retrieval, encoding and handling that @value{GDBN} applies to a
26118 @code{gdb.LazyString}.
26121 @defvar LazyString.address
26122 This attribute holds the address of the string. This attribute is not
26126 @defvar LazyString.length
26127 This attribute holds the length of the string in characters. If the
26128 length is -1, then the string will be fetched and encoded up to the
26129 first null of appropriate width. This attribute is not writable.
26132 @defvar LazyString.encoding
26133 This attribute holds the encoding that will be applied to the string
26134 when the string is printed by @value{GDBN}. If the encoding is not
26135 set, or contains an empty string, then @value{GDBN} will select the
26136 most appropriate encoding when the string is printed. This attribute
26140 @defvar LazyString.type
26141 This attribute holds the type that is represented by the lazy string's
26142 type. For a lazy string this will always be a pointer type. To
26143 resolve this to the lazy string's character type, use the type's
26144 @code{target} method. @xref{Types In Python}. This attribute is not
26148 @node Architectures In Python
26149 @subsubsection Python representation of architectures
26150 @cindex Python architectures
26152 @value{GDBN} uses architecture specific parameters and artifacts in a
26153 number of its various computations. An architecture is represented
26154 by an instance of the @code{gdb.Architecture} class.
26156 A @code{gdb.Architecture} class has the following methods:
26158 @defun Architecture.name ()
26159 Return the name (string value) of the architecture.
26162 @defun Architecture.disassemble (@var{start_pc} @r{[}, @var{end_pc} @r{[}, @var{count}@r{]]})
26163 Return a list of disassembled instructions starting from the memory
26164 address @var{start_pc}. The optional arguments @var{end_pc} and
26165 @var{count} determine the number of instructions in the returned list.
26166 If both the optional arguments @var{end_pc} and @var{count} are
26167 specified, then a list of at most @var{count} disassembled instructions
26168 whose start address falls in the closed memory address interval from
26169 @var{start_pc} to @var{end_pc} are returned. If @var{end_pc} is not
26170 specified, but @var{count} is specified, then @var{count} number of
26171 instructions starting from the address @var{start_pc} are returned. If
26172 @var{count} is not specified but @var{end_pc} is specified, then all
26173 instructions whose start address falls in the closed memory address
26174 interval from @var{start_pc} to @var{end_pc} are returned. If neither
26175 @var{end_pc} nor @var{count} are specified, then a single instruction at
26176 @var{start_pc} is returned. For all of these cases, each element of the
26177 returned list is a Python @code{dict} with the following string keys:
26182 The value corresponding to this key is a Python long integer capturing
26183 the memory address of the instruction.
26186 The value corresponding to this key is a string value which represents
26187 the instruction with assembly language mnemonics. The assembly
26188 language flavor used is the same as that specified by the current CLI
26189 variable @code{disassembly-flavor}. @xref{Machine Code}.
26192 The value corresponding to this key is the length (integer value) of the
26193 instruction in bytes.
26198 @node Python Auto-loading
26199 @subsection Python Auto-loading
26200 @cindex Python auto-loading
26202 When a new object file is read (for example, due to the @code{file}
26203 command, or because the inferior has loaded a shared library),
26204 @value{GDBN} will look for Python support scripts in several ways:
26205 @file{@var{objfile}-gdb.py} (@pxref{objfile-gdb.py file})
26206 and @code{.debug_gdb_scripts} section
26207 (@pxref{dotdebug_gdb_scripts section}).
26209 The auto-loading feature is useful for supplying application-specific
26210 debugging commands and scripts.
26212 Auto-loading can be enabled or disabled,
26213 and the list of auto-loaded scripts can be printed.
26216 @anchor{set auto-load python-scripts}
26217 @kindex set auto-load python-scripts
26218 @item set auto-load python-scripts [on|off]
26219 Enable or disable the auto-loading of Python scripts.
26221 @anchor{show auto-load python-scripts}
26222 @kindex show auto-load python-scripts
26223 @item show auto-load python-scripts
26224 Show whether auto-loading of Python scripts is enabled or disabled.
26226 @anchor{info auto-load python-scripts}
26227 @kindex info auto-load python-scripts
26228 @cindex print list of auto-loaded Python scripts
26229 @item info auto-load python-scripts [@var{regexp}]
26230 Print the list of all Python scripts that @value{GDBN} auto-loaded.
26232 Also printed is the list of Python scripts that were mentioned in
26233 the @code{.debug_gdb_scripts} section and were not found
26234 (@pxref{dotdebug_gdb_scripts section}).
26235 This is useful because their names are not printed when @value{GDBN}
26236 tries to load them and fails. There may be many of them, and printing
26237 an error message for each one is problematic.
26239 If @var{regexp} is supplied only Python scripts with matching names are printed.
26244 (gdb) info auto-load python-scripts
26246 Yes py-section-script.py
26247 full name: /tmp/py-section-script.py
26248 No my-foo-pretty-printers.py
26252 When reading an auto-loaded file, @value{GDBN} sets the
26253 @dfn{current objfile}. This is available via the @code{gdb.current_objfile}
26254 function (@pxref{Objfiles In Python}). This can be useful for
26255 registering objfile-specific pretty-printers.
26258 * objfile-gdb.py file:: The @file{@var{objfile}-gdb.py} file
26259 * dotdebug_gdb_scripts section:: The @code{.debug_gdb_scripts} section
26260 * Which flavor to choose?::
26263 @node objfile-gdb.py file
26264 @subsubsection The @file{@var{objfile}-gdb.py} file
26265 @cindex @file{@var{objfile}-gdb.py}
26267 When a new object file is read, @value{GDBN} looks for
26268 a file named @file{@var{objfile}-gdb.py} (we call it @var{script-name} below),
26269 where @var{objfile} is the object file's real name, formed by ensuring
26270 that the file name is absolute, following all symlinks, and resolving
26271 @code{.} and @code{..} components. If this file exists and is
26272 readable, @value{GDBN} will evaluate it as a Python script.
26274 If this file does not exist, then @value{GDBN} will look for
26275 @var{script-name} file in all of the directories as specified below.
26277 Note that loading of this script file also requires accordingly configured
26278 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26280 For object files using @file{.exe} suffix @value{GDBN} tries to load first the
26281 scripts normally according to its @file{.exe} filename. But if no scripts are
26282 found @value{GDBN} also tries script filenames matching the object file without
26283 its @file{.exe} suffix. This @file{.exe} stripping is case insensitive and it
26284 is attempted on any platform. This makes the script filenames compatible
26285 between Unix and MS-Windows hosts.
26288 @anchor{set auto-load scripts-directory}
26289 @kindex set auto-load scripts-directory
26290 @item set auto-load scripts-directory @r{[}@var{directories}@r{]}
26291 Control @value{GDBN} auto-loaded scripts location. Multiple directory entries
26292 may be delimited by the host platform path separator in use
26293 (@samp{:} on Unix, @samp{;} on MS-Windows and MS-DOS).
26295 Each entry here needs to be covered also by the security setting
26296 @code{set auto-load safe-path} (@pxref{set auto-load safe-path}).
26298 @anchor{with-auto-load-dir}
26299 This variable defaults to @file{$debugdir:$datadir/auto-load}. The default
26300 @code{set auto-load safe-path} value can be also overriden by @value{GDBN}
26301 configuration option @option{--with-auto-load-dir}.
26303 Any reference to @file{$debugdir} will get replaced by
26304 @var{debug-file-directory} value (@pxref{Separate Debug Files}) and any
26305 reference to @file{$datadir} will get replaced by @var{data-directory} which is
26306 determined at @value{GDBN} startup (@pxref{Data Files}). @file{$debugdir} and
26307 @file{$datadir} must be placed as a directory component --- either alone or
26308 delimited by @file{/} or @file{\} directory separators, depending on the host
26311 The list of directories uses path separator (@samp{:} on GNU and Unix
26312 systems, @samp{;} on MS-Windows and MS-DOS) to separate directories, similarly
26313 to the @env{PATH} environment variable.
26315 @anchor{show auto-load scripts-directory}
26316 @kindex show auto-load scripts-directory
26317 @item show auto-load scripts-directory
26318 Show @value{GDBN} auto-loaded scripts location.
26321 @value{GDBN} does not track which files it has already auto-loaded this way.
26322 @value{GDBN} will load the associated script every time the corresponding
26323 @var{objfile} is opened.
26324 So your @file{-gdb.py} file should be careful to avoid errors if it
26325 is evaluated more than once.
26327 @node dotdebug_gdb_scripts section
26328 @subsubsection The @code{.debug_gdb_scripts} section
26329 @cindex @code{.debug_gdb_scripts} section
26331 For systems using file formats like ELF and COFF,
26332 when @value{GDBN} loads a new object file
26333 it will look for a special section named @samp{.debug_gdb_scripts}.
26334 If this section exists, its contents is a list of names of scripts to load.
26336 @value{GDBN} will look for each specified script file first in the
26337 current directory and then along the source search path
26338 (@pxref{Source Path, ,Specifying Source Directories}),
26339 except that @file{$cdir} is not searched, since the compilation
26340 directory is not relevant to scripts.
26342 Entries can be placed in section @code{.debug_gdb_scripts} with,
26343 for example, this GCC macro:
26346 /* Note: The "MS" section flags are to remove duplicates. */
26347 #define DEFINE_GDB_SCRIPT(script_name) \
26349 .pushsection \".debug_gdb_scripts\", \"MS\",@@progbits,1\n\
26351 .asciz \"" script_name "\"\n\
26357 Then one can reference the macro in a header or source file like this:
26360 DEFINE_GDB_SCRIPT ("my-app-scripts.py")
26363 The script name may include directories if desired.
26365 Note that loading of this script file also requires accordingly configured
26366 @code{auto-load safe-path} (@pxref{Auto-loading safe path}).
26368 If the macro is put in a header, any application or library
26369 using this header will get a reference to the specified script.
26371 @node Which flavor to choose?
26372 @subsubsection Which flavor to choose?
26374 Given the multiple ways of auto-loading Python scripts, it might not always
26375 be clear which one to choose. This section provides some guidance.
26377 Benefits of the @file{-gdb.py} way:
26381 Can be used with file formats that don't support multiple sections.
26384 Ease of finding scripts for public libraries.
26386 Scripts specified in the @code{.debug_gdb_scripts} section are searched for
26387 in the source search path.
26388 For publicly installed libraries, e.g., @file{libstdc++}, there typically
26389 isn't a source directory in which to find the script.
26392 Doesn't require source code additions.
26395 Benefits of the @code{.debug_gdb_scripts} way:
26399 Works with static linking.
26401 Scripts for libraries done the @file{-gdb.py} way require an objfile to
26402 trigger their loading. When an application is statically linked the only
26403 objfile available is the executable, and it is cumbersome to attach all the
26404 scripts from all the input libraries to the executable's @file{-gdb.py} script.
26407 Works with classes that are entirely inlined.
26409 Some classes can be entirely inlined, and thus there may not be an associated
26410 shared library to attach a @file{-gdb.py} script to.
26413 Scripts needn't be copied out of the source tree.
26415 In some circumstances, apps can be built out of large collections of internal
26416 libraries, and the build infrastructure necessary to install the
26417 @file{-gdb.py} scripts in a place where @value{GDBN} can find them is
26418 cumbersome. It may be easier to specify the scripts in the
26419 @code{.debug_gdb_scripts} section as relative paths, and add a path to the
26420 top of the source tree to the source search path.
26423 @node Python modules
26424 @subsection Python modules
26425 @cindex python modules
26427 @value{GDBN} comes with several modules to assist writing Python code.
26430 * gdb.printing:: Building and registering pretty-printers.
26431 * gdb.types:: Utilities for working with types.
26432 * gdb.prompt:: Utilities for prompt value substitution.
26436 @subsubsection gdb.printing
26437 @cindex gdb.printing
26439 This module provides a collection of utilities for working with
26443 @item PrettyPrinter (@var{name}, @var{subprinters}=None)
26444 This class specifies the API that makes @samp{info pretty-printer},
26445 @samp{enable pretty-printer} and @samp{disable pretty-printer} work.
26446 Pretty-printers should generally inherit from this class.
26448 @item SubPrettyPrinter (@var{name})
26449 For printers that handle multiple types, this class specifies the
26450 corresponding API for the subprinters.
26452 @item RegexpCollectionPrettyPrinter (@var{name})
26453 Utility class for handling multiple printers, all recognized via
26454 regular expressions.
26455 @xref{Writing a Pretty-Printer}, for an example.
26457 @item FlagEnumerationPrinter (@var{name})
26458 A pretty-printer which handles printing of @code{enum} values. Unlike
26459 @value{GDBN}'s built-in @code{enum} printing, this printer attempts to
26460 work properly when there is some overlap between the enumeration
26461 constants. @var{name} is the name of the printer and also the name of
26462 the @code{enum} type to look up.
26464 @item register_pretty_printer (@var{obj}, @var{printer}, @var{replace}=False)
26465 Register @var{printer} with the pretty-printer list of @var{obj}.
26466 If @var{replace} is @code{True} then any existing copy of the printer
26467 is replaced. Otherwise a @code{RuntimeError} exception is raised
26468 if a printer with the same name already exists.
26472 @subsubsection gdb.types
26475 This module provides a collection of utilities for working with
26476 @code{gdb.Type} objects.
26479 @item get_basic_type (@var{type})
26480 Return @var{type} with const and volatile qualifiers stripped,
26481 and with typedefs and C@t{++} references converted to the underlying type.
26486 typedef const int const_int;
26488 const_int& foo_ref (foo);
26489 int main () @{ return 0; @}
26496 (gdb) python import gdb.types
26497 (gdb) python foo_ref = gdb.parse_and_eval("foo_ref")
26498 (gdb) python print gdb.types.get_basic_type(foo_ref.type)
26502 @item has_field (@var{type}, @var{field})
26503 Return @code{True} if @var{type}, assumed to be a type with fields
26504 (e.g., a structure or union), has field @var{field}.
26506 @item make_enum_dict (@var{enum_type})
26507 Return a Python @code{dictionary} type produced from @var{enum_type}.
26509 @item deep_items (@var{type})
26510 Returns a Python iterator similar to the standard
26511 @code{gdb.Type.iteritems} method, except that the iterator returned
26512 by @code{deep_items} will recursively traverse anonymous struct or
26513 union fields. For example:
26527 Then in @value{GDBN}:
26529 (@value{GDBP}) python import gdb.types
26530 (@value{GDBP}) python struct_a = gdb.lookup_type("struct A")
26531 (@value{GDBP}) python print struct_a.keys ()
26533 (@value{GDBP}) python print [k for k,v in gdb.types.deep_items(struct_a)]
26534 @{['a', 'b0', 'b1']@}
26537 @item get_type_recognizers ()
26538 Return a list of the enabled type recognizers for the current context.
26539 This is called by @value{GDBN} during the type-printing process
26540 (@pxref{Type Printing API}).
26542 @item apply_type_recognizers (recognizers, type_obj)
26543 Apply the type recognizers, @var{recognizers}, to the type object
26544 @var{type_obj}. If any recognizer returns a string, return that
26545 string. Otherwise, return @code{None}. This is called by
26546 @value{GDBN} during the type-printing process (@pxref{Type Printing
26549 @item register_type_printer (locus, printer)
26550 This is a convenience function to register a type printer.
26551 @var{printer} is the type printer to register. It must implement the
26552 type printer protocol. @var{locus} is either a @code{gdb.Objfile}, in
26553 which case the printer is registered with that objfile; a
26554 @code{gdb.Progspace}, in which case the printer is registered with
26555 that progspace; or @code{None}, in which case the printer is
26556 registered globally.
26559 This is a base class that implements the type printer protocol. Type
26560 printers are encouraged, but not required, to derive from this class.
26561 It defines a constructor:
26563 @defmethod TypePrinter __init__ (self, name)
26564 Initialize the type printer with the given name. The new printer
26565 starts in the enabled state.
26571 @subsubsection gdb.prompt
26574 This module provides a method for prompt value-substitution.
26577 @item substitute_prompt (@var{string})
26578 Return @var{string} with escape sequences substituted by values. Some
26579 escape sequences take arguments. You can specify arguments inside
26580 ``@{@}'' immediately following the escape sequence.
26582 The escape sequences you can pass to this function are:
26586 Substitute a backslash.
26588 Substitute an ESC character.
26590 Substitute the selected frame; an argument names a frame parameter.
26592 Substitute a newline.
26594 Substitute a parameter's value; the argument names the parameter.
26596 Substitute a carriage return.
26598 Substitute the selected thread; an argument names a thread parameter.
26600 Substitute the version of GDB.
26602 Substitute the current working directory.
26604 Begin a sequence of non-printing characters. These sequences are
26605 typically used with the ESC character, and are not counted in the string
26606 length. Example: ``\[\e[0;34m\](gdb)\[\e[0m\]'' will return a
26607 blue-colored ``(gdb)'' prompt where the length is five.
26609 End a sequence of non-printing characters.
26615 substitute_prompt (``frame: \f,
26616 print arguments: \p@{print frame-arguments@}'')
26619 @exdent will return the string:
26622 "frame: main, print arguments: scalars"
26627 @section Creating new spellings of existing commands
26628 @cindex aliases for commands
26630 It is often useful to define alternate spellings of existing commands.
26631 For example, if a new @value{GDBN} command defined in Python has
26632 a long name to type, it is handy to have an abbreviated version of it
26633 that involves less typing.
26635 @value{GDBN} itself uses aliases. For example @samp{s} is an alias
26636 of the @samp{step} command even though it is otherwise an ambiguous
26637 abbreviation of other commands like @samp{set} and @samp{show}.
26639 Aliases are also used to provide shortened or more common versions
26640 of multi-word commands. For example, @value{GDBN} provides the
26641 @samp{tty} alias of the @samp{set inferior-tty} command.
26643 You can define a new alias with the @samp{alias} command.
26648 @item alias [-a] [--] @var{ALIAS} = @var{COMMAND}
26652 @var{ALIAS} specifies the name of the new alias.
26653 Each word of @var{ALIAS} must consist of letters, numbers, dashes and
26656 @var{COMMAND} specifies the name of an existing command
26657 that is being aliased.
26659 The @samp{-a} option specifies that the new alias is an abbreviation
26660 of the command. Abbreviations are not shown in command
26661 lists displayed by the @samp{help} command.
26663 The @samp{--} option specifies the end of options,
26664 and is useful when @var{ALIAS} begins with a dash.
26666 Here is a simple example showing how to make an abbreviation
26667 of a command so that there is less to type.
26668 Suppose you were tired of typing @samp{disas}, the current
26669 shortest unambiguous abbreviation of the @samp{disassemble} command
26670 and you wanted an even shorter version named @samp{di}.
26671 The following will accomplish this.
26674 (gdb) alias -a di = disas
26677 Note that aliases are different from user-defined commands.
26678 With a user-defined command, you also need to write documentation
26679 for it with the @samp{document} command.
26680 An alias automatically picks up the documentation of the existing command.
26682 Here is an example where we make @samp{elms} an abbreviation of
26683 @samp{elements} in the @samp{set print elements} command.
26684 This is to show that you can make an abbreviation of any part
26688 (gdb) alias -a set print elms = set print elements
26689 (gdb) alias -a show print elms = show print elements
26690 (gdb) set p elms 20
26692 Limit on string chars or array elements to print is 200.
26695 Note that if you are defining an alias of a @samp{set} command,
26696 and you want to have an alias for the corresponding @samp{show}
26697 command, then you need to define the latter separately.
26699 Unambiguously abbreviated commands are allowed in @var{COMMAND} and
26700 @var{ALIAS}, just as they are normally.
26703 (gdb) alias -a set pr elms = set p ele
26706 Finally, here is an example showing the creation of a one word
26707 alias for a more complex command.
26708 This creates alias @samp{spe} of the command @samp{set print elements}.
26711 (gdb) alias spe = set print elements
26716 @chapter Command Interpreters
26717 @cindex command interpreters
26719 @value{GDBN} supports multiple command interpreters, and some command
26720 infrastructure to allow users or user interface writers to switch
26721 between interpreters or run commands in other interpreters.
26723 @value{GDBN} currently supports two command interpreters, the console
26724 interpreter (sometimes called the command-line interpreter or @sc{cli})
26725 and the machine interface interpreter (or @sc{gdb/mi}). This manual
26726 describes both of these interfaces in great detail.
26728 By default, @value{GDBN} will start with the console interpreter.
26729 However, the user may choose to start @value{GDBN} with another
26730 interpreter by specifying the @option{-i} or @option{--interpreter}
26731 startup options. Defined interpreters include:
26735 @cindex console interpreter
26736 The traditional console or command-line interpreter. This is the most often
26737 used interpreter with @value{GDBN}. With no interpreter specified at runtime,
26738 @value{GDBN} will use this interpreter.
26741 @cindex mi interpreter
26742 The newest @sc{gdb/mi} interface (currently @code{mi2}). Used primarily
26743 by programs wishing to use @value{GDBN} as a backend for a debugger GUI
26744 or an IDE. For more information, see @ref{GDB/MI, ,The @sc{gdb/mi}
26748 @cindex mi2 interpreter
26749 The current @sc{gdb/mi} interface.
26752 @cindex mi1 interpreter
26753 The @sc{gdb/mi} interface included in @value{GDBN} 5.1, 5.2, and 5.3.
26757 @cindex invoke another interpreter
26758 The interpreter being used by @value{GDBN} may not be dynamically
26759 switched at runtime. Although possible, this could lead to a very
26760 precarious situation. Consider an IDE using @sc{gdb/mi}. If a user
26761 enters the command "interpreter-set console" in a console view,
26762 @value{GDBN} would switch to using the console interpreter, rendering
26763 the IDE inoperable!
26765 @kindex interpreter-exec
26766 Although you may only choose a single interpreter at startup, you may execute
26767 commands in any interpreter from the current interpreter using the appropriate
26768 command. If you are running the console interpreter, simply use the
26769 @code{interpreter-exec} command:
26772 interpreter-exec mi "-data-list-register-names"
26775 @sc{gdb/mi} has a similar command, although it is only available in versions of
26776 @value{GDBN} which support @sc{gdb/mi} version 2 (or greater).
26779 @chapter @value{GDBN} Text User Interface
26781 @cindex Text User Interface
26784 * TUI Overview:: TUI overview
26785 * TUI Keys:: TUI key bindings
26786 * TUI Single Key Mode:: TUI single key mode
26787 * TUI Commands:: TUI-specific commands
26788 * TUI Configuration:: TUI configuration variables
26791 The @value{GDBN} Text User Interface (TUI) is a terminal
26792 interface which uses the @code{curses} library to show the source
26793 file, the assembly output, the program registers and @value{GDBN}
26794 commands in separate text windows. The TUI mode is supported only
26795 on platforms where a suitable version of the @code{curses} library
26798 The TUI mode is enabled by default when you invoke @value{GDBN} as
26799 @samp{@value{GDBP} -tui}.
26800 You can also switch in and out of TUI mode while @value{GDBN} runs by
26801 using various TUI commands and key bindings, such as @kbd{C-x C-a}.
26802 @xref{TUI Keys, ,TUI Key Bindings}.
26805 @section TUI Overview
26807 In TUI mode, @value{GDBN} can display several text windows:
26811 This window is the @value{GDBN} command window with the @value{GDBN}
26812 prompt and the @value{GDBN} output. The @value{GDBN} input is still
26813 managed using readline.
26816 The source window shows the source file of the program. The current
26817 line and active breakpoints are displayed in this window.
26820 The assembly window shows the disassembly output of the program.
26823 This window shows the processor registers. Registers are highlighted
26824 when their values change.
26827 The source and assembly windows show the current program position
26828 by highlighting the current line and marking it with a @samp{>} marker.
26829 Breakpoints are indicated with two markers. The first marker
26830 indicates the breakpoint type:
26834 Breakpoint which was hit at least once.
26837 Breakpoint which was never hit.
26840 Hardware breakpoint which was hit at least once.
26843 Hardware breakpoint which was never hit.
26846 The second marker indicates whether the breakpoint is enabled or not:
26850 Breakpoint is enabled.
26853 Breakpoint is disabled.
26856 The source, assembly and register windows are updated when the current
26857 thread changes, when the frame changes, or when the program counter
26860 These windows are not all visible at the same time. The command
26861 window is always visible. The others can be arranged in several
26872 source and assembly,
26875 source and registers, or
26878 assembly and registers.
26881 A status line above the command window shows the following information:
26885 Indicates the current @value{GDBN} target.
26886 (@pxref{Targets, ,Specifying a Debugging Target}).
26889 Gives the current process or thread number.
26890 When no process is being debugged, this field is set to @code{No process}.
26893 Gives the current function name for the selected frame.
26894 The name is demangled if demangling is turned on (@pxref{Print Settings}).
26895 When there is no symbol corresponding to the current program counter,
26896 the string @code{??} is displayed.
26899 Indicates the current line number for the selected frame.
26900 When the current line number is not known, the string @code{??} is displayed.
26903 Indicates the current program counter address.
26907 @section TUI Key Bindings
26908 @cindex TUI key bindings
26910 The TUI installs several key bindings in the readline keymaps
26911 @ifset SYSTEM_READLINE
26912 (@pxref{Command Line Editing, , , rluserman, GNU Readline Library}).
26914 @ifclear SYSTEM_READLINE
26915 (@pxref{Command Line Editing}).
26917 The following key bindings are installed for both TUI mode and the
26918 @value{GDBN} standard mode.
26927 Enter or leave the TUI mode. When leaving the TUI mode,
26928 the curses window management stops and @value{GDBN} operates using
26929 its standard mode, writing on the terminal directly. When reentering
26930 the TUI mode, control is given back to the curses windows.
26931 The screen is then refreshed.
26935 Use a TUI layout with only one window. The layout will
26936 either be @samp{source} or @samp{assembly}. When the TUI mode
26937 is not active, it will switch to the TUI mode.
26939 Think of this key binding as the Emacs @kbd{C-x 1} binding.
26943 Use a TUI layout with at least two windows. When the current
26944 layout already has two windows, the next layout with two windows is used.
26945 When a new layout is chosen, one window will always be common to the
26946 previous layout and the new one.
26948 Think of it as the Emacs @kbd{C-x 2} binding.
26952 Change the active window. The TUI associates several key bindings
26953 (like scrolling and arrow keys) with the active window. This command
26954 gives the focus to the next TUI window.
26956 Think of it as the Emacs @kbd{C-x o} binding.
26960 Switch in and out of the TUI SingleKey mode that binds single
26961 keys to @value{GDBN} commands (@pxref{TUI Single Key Mode}).
26964 The following key bindings only work in the TUI mode:
26969 Scroll the active window one page up.
26973 Scroll the active window one page down.
26977 Scroll the active window one line up.
26981 Scroll the active window one line down.
26985 Scroll the active window one column left.
26989 Scroll the active window one column right.
26993 Refresh the screen.
26996 Because the arrow keys scroll the active window in the TUI mode, they
26997 are not available for their normal use by readline unless the command
26998 window has the focus. When another window is active, you must use
26999 other readline key bindings such as @kbd{C-p}, @kbd{C-n}, @kbd{C-b}
27000 and @kbd{C-f} to control the command window.
27002 @node TUI Single Key Mode
27003 @section TUI Single Key Mode
27004 @cindex TUI single key mode
27006 The TUI also provides a @dfn{SingleKey} mode, which binds several
27007 frequently used @value{GDBN} commands to single keys. Type @kbd{C-x s} to
27008 switch into this mode, where the following key bindings are used:
27011 @kindex c @r{(SingleKey TUI key)}
27015 @kindex d @r{(SingleKey TUI key)}
27019 @kindex f @r{(SingleKey TUI key)}
27023 @kindex n @r{(SingleKey TUI key)}
27027 @kindex q @r{(SingleKey TUI key)}
27029 exit the SingleKey mode.
27031 @kindex r @r{(SingleKey TUI key)}
27035 @kindex s @r{(SingleKey TUI key)}
27039 @kindex u @r{(SingleKey TUI key)}
27043 @kindex v @r{(SingleKey TUI key)}
27047 @kindex w @r{(SingleKey TUI key)}
27052 Other keys temporarily switch to the @value{GDBN} command prompt.
27053 The key that was pressed is inserted in the editing buffer so that
27054 it is possible to type most @value{GDBN} commands without interaction
27055 with the TUI SingleKey mode. Once the command is entered the TUI
27056 SingleKey mode is restored. The only way to permanently leave
27057 this mode is by typing @kbd{q} or @kbd{C-x s}.
27061 @section TUI-specific Commands
27062 @cindex TUI commands
27064 The TUI has specific commands to control the text windows.
27065 These commands are always available, even when @value{GDBN} is not in
27066 the TUI mode. When @value{GDBN} is in the standard mode, most
27067 of these commands will automatically switch to the TUI mode.
27069 Note that if @value{GDBN}'s @code{stdout} is not connected to a
27070 terminal, or @value{GDBN} has been started with the machine interface
27071 interpreter (@pxref{GDB/MI, ,The @sc{gdb/mi} Interface}), most of
27072 these commands will fail with an error, because it would not be
27073 possible or desirable to enable curses window management.
27078 List and give the size of all displayed windows.
27082 Display the next layout.
27085 Display the previous layout.
27088 Display the source window only.
27091 Display the assembly window only.
27094 Display the source and assembly window.
27097 Display the register window together with the source or assembly window.
27101 Make the next window active for scrolling.
27104 Make the previous window active for scrolling.
27107 Make the source window active for scrolling.
27110 Make the assembly window active for scrolling.
27113 Make the register window active for scrolling.
27116 Make the command window active for scrolling.
27120 Refresh the screen. This is similar to typing @kbd{C-L}.
27122 @item tui reg float
27124 Show the floating point registers in the register window.
27126 @item tui reg general
27127 Show the general registers in the register window.
27130 Show the next register group. The list of register groups as well as
27131 their order is target specific. The predefined register groups are the
27132 following: @code{general}, @code{float}, @code{system}, @code{vector},
27133 @code{all}, @code{save}, @code{restore}.
27135 @item tui reg system
27136 Show the system registers in the register window.
27140 Update the source window and the current execution point.
27142 @item winheight @var{name} +@var{count}
27143 @itemx winheight @var{name} -@var{count}
27145 Change the height of the window @var{name} by @var{count}
27146 lines. Positive counts increase the height, while negative counts
27149 @item tabset @var{nchars}
27151 Set the width of tab stops to be @var{nchars} characters.
27154 @node TUI Configuration
27155 @section TUI Configuration Variables
27156 @cindex TUI configuration variables
27158 Several configuration variables control the appearance of TUI windows.
27161 @item set tui border-kind @var{kind}
27162 @kindex set tui border-kind
27163 Select the border appearance for the source, assembly and register windows.
27164 The possible values are the following:
27167 Use a space character to draw the border.
27170 Use @sc{ascii} characters @samp{+}, @samp{-} and @samp{|} to draw the border.
27173 Use the Alternate Character Set to draw the border. The border is
27174 drawn using character line graphics if the terminal supports them.
27177 @item set tui border-mode @var{mode}
27178 @kindex set tui border-mode
27179 @itemx set tui active-border-mode @var{mode}
27180 @kindex set tui active-border-mode
27181 Select the display attributes for the borders of the inactive windows
27182 or the active window. The @var{mode} can be one of the following:
27185 Use normal attributes to display the border.
27191 Use reverse video mode.
27194 Use half bright mode.
27196 @item half-standout
27197 Use half bright and standout mode.
27200 Use extra bright or bold mode.
27202 @item bold-standout
27203 Use extra bright or bold and standout mode.
27208 @chapter Using @value{GDBN} under @sc{gnu} Emacs
27211 @cindex @sc{gnu} Emacs
27212 A special interface allows you to use @sc{gnu} Emacs to view (and
27213 edit) the source files for the program you are debugging with
27216 To use this interface, use the command @kbd{M-x gdb} in Emacs. Give the
27217 executable file you want to debug as an argument. This command starts
27218 @value{GDBN} as a subprocess of Emacs, with input and output through a newly
27219 created Emacs buffer.
27220 @c (Do not use the @code{-tui} option to run @value{GDBN} from Emacs.)
27222 Running @value{GDBN} under Emacs can be just like running @value{GDBN} normally except for two
27227 All ``terminal'' input and output goes through an Emacs buffer, called
27230 This applies both to @value{GDBN} commands and their output, and to the input
27231 and output done by the program you are debugging.
27233 This is useful because it means that you can copy the text of previous
27234 commands and input them again; you can even use parts of the output
27237 All the facilities of Emacs' Shell mode are available for interacting
27238 with your program. In particular, you can send signals the usual
27239 way---for example, @kbd{C-c C-c} for an interrupt, @kbd{C-c C-z} for a
27243 @value{GDBN} displays source code through Emacs.
27245 Each time @value{GDBN} displays a stack frame, Emacs automatically finds the
27246 source file for that frame and puts an arrow (@samp{=>}) at the
27247 left margin of the current line. Emacs uses a separate buffer for
27248 source display, and splits the screen to show both your @value{GDBN} session
27251 Explicit @value{GDBN} @code{list} or search commands still produce output as
27252 usual, but you probably have no reason to use them from Emacs.
27255 We call this @dfn{text command mode}. Emacs 22.1, and later, also uses
27256 a graphical mode, enabled by default, which provides further buffers
27257 that can control the execution and describe the state of your program.
27258 @xref{GDB Graphical Interface,,, Emacs, The @sc{gnu} Emacs Manual}.
27260 If you specify an absolute file name when prompted for the @kbd{M-x
27261 gdb} argument, then Emacs sets your current working directory to where
27262 your program resides. If you only specify the file name, then Emacs
27263 sets your current working directory to the directory associated
27264 with the previous buffer. In this case, @value{GDBN} may find your
27265 program by searching your environment's @code{PATH} variable, but on
27266 some operating systems it might not find the source. So, although the
27267 @value{GDBN} input and output session proceeds normally, the auxiliary
27268 buffer does not display the current source and line of execution.
27270 The initial working directory of @value{GDBN} is printed on the top
27271 line of the GUD buffer and this serves as a default for the commands
27272 that specify files for @value{GDBN} to operate on. @xref{Files,
27273 ,Commands to Specify Files}.
27275 By default, @kbd{M-x gdb} calls the program called @file{gdb}. If you
27276 need to call @value{GDBN} by a different name (for example, if you
27277 keep several configurations around, with different names) you can
27278 customize the Emacs variable @code{gud-gdb-command-name} to run the
27281 In the GUD buffer, you can use these special Emacs commands in
27282 addition to the standard Shell mode commands:
27286 Describe the features of Emacs' GUD Mode.
27289 Execute to another source line, like the @value{GDBN} @code{step} command; also
27290 update the display window to show the current file and location.
27293 Execute to next source line in this function, skipping all function
27294 calls, like the @value{GDBN} @code{next} command. Then update the display window
27295 to show the current file and location.
27298 Execute one instruction, like the @value{GDBN} @code{stepi} command; update
27299 display window accordingly.
27302 Execute until exit from the selected stack frame, like the @value{GDBN}
27303 @code{finish} command.
27306 Continue execution of your program, like the @value{GDBN} @code{continue}
27310 Go up the number of frames indicated by the numeric argument
27311 (@pxref{Arguments, , Numeric Arguments, Emacs, The @sc{gnu} Emacs Manual}),
27312 like the @value{GDBN} @code{up} command.
27315 Go down the number of frames indicated by the numeric argument, like the
27316 @value{GDBN} @code{down} command.
27319 In any source file, the Emacs command @kbd{C-x @key{SPC}} (@code{gud-break})
27320 tells @value{GDBN} to set a breakpoint on the source line point is on.
27322 In text command mode, if you type @kbd{M-x speedbar}, Emacs displays a
27323 separate frame which shows a backtrace when the GUD buffer is current.
27324 Move point to any frame in the stack and type @key{RET} to make it
27325 become the current frame and display the associated source in the
27326 source buffer. Alternatively, click @kbd{Mouse-2} to make the
27327 selected frame become the current one. In graphical mode, the
27328 speedbar displays watch expressions.
27330 If you accidentally delete the source-display buffer, an easy way to get
27331 it back is to type the command @code{f} in the @value{GDBN} buffer, to
27332 request a frame display; when you run under Emacs, this recreates
27333 the source buffer if necessary to show you the context of the current
27336 The source files displayed in Emacs are in ordinary Emacs buffers
27337 which are visiting the source files in the usual way. You can edit
27338 the files with these buffers if you wish; but keep in mind that @value{GDBN}
27339 communicates with Emacs in terms of line numbers. If you add or
27340 delete lines from the text, the line numbers that @value{GDBN} knows cease
27341 to correspond properly with the code.
27343 A more detailed description of Emacs' interaction with @value{GDBN} is
27344 given in the Emacs manual (@pxref{Debuggers,,, Emacs, The @sc{gnu}
27348 @chapter The @sc{gdb/mi} Interface
27350 @unnumberedsec Function and Purpose
27352 @cindex @sc{gdb/mi}, its purpose
27353 @sc{gdb/mi} is a line based machine oriented text interface to
27354 @value{GDBN} and is activated by specifying using the
27355 @option{--interpreter} command line option (@pxref{Mode Options}). It
27356 is specifically intended to support the development of systems which
27357 use the debugger as just one small component of a larger system.
27359 This chapter is a specification of the @sc{gdb/mi} interface. It is written
27360 in the form of a reference manual.
27362 Note that @sc{gdb/mi} is still under construction, so some of the
27363 features described below are incomplete and subject to change
27364 (@pxref{GDB/MI Development and Front Ends, , @sc{gdb/mi} Development and Front Ends}).
27366 @unnumberedsec Notation and Terminology
27368 @cindex notational conventions, for @sc{gdb/mi}
27369 This chapter uses the following notation:
27373 @code{|} separates two alternatives.
27376 @code{[ @var{something} ]} indicates that @var{something} is optional:
27377 it may or may not be given.
27380 @code{( @var{group} )*} means that @var{group} inside the parentheses
27381 may repeat zero or more times.
27384 @code{( @var{group} )+} means that @var{group} inside the parentheses
27385 may repeat one or more times.
27388 @code{"@var{string}"} means a literal @var{string}.
27392 @heading Dependencies
27396 * GDB/MI General Design::
27397 * GDB/MI Command Syntax::
27398 * GDB/MI Compatibility with CLI::
27399 * GDB/MI Development and Front Ends::
27400 * GDB/MI Output Records::
27401 * GDB/MI Simple Examples::
27402 * GDB/MI Command Description Format::
27403 * GDB/MI Breakpoint Commands::
27404 * GDB/MI Catchpoint Commands::
27405 * GDB/MI Program Context::
27406 * GDB/MI Thread Commands::
27407 * GDB/MI Ada Tasking Commands::
27408 * GDB/MI Program Execution::
27409 * GDB/MI Stack Manipulation::
27410 * GDB/MI Variable Objects::
27411 * GDB/MI Data Manipulation::
27412 * GDB/MI Tracepoint Commands::
27413 * GDB/MI Symbol Query::
27414 * GDB/MI File Commands::
27416 * GDB/MI Kod Commands::
27417 * GDB/MI Memory Overlay Commands::
27418 * GDB/MI Signal Handling Commands::
27420 * GDB/MI Target Manipulation::
27421 * GDB/MI File Transfer Commands::
27422 * GDB/MI Miscellaneous Commands::
27425 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27426 @node GDB/MI General Design
27427 @section @sc{gdb/mi} General Design
27428 @cindex GDB/MI General Design
27430 Interaction of a @sc{GDB/MI} frontend with @value{GDBN} involves three
27431 parts---commands sent to @value{GDBN}, responses to those commands
27432 and notifications. Each command results in exactly one response,
27433 indicating either successful completion of the command, or an error.
27434 For the commands that do not resume the target, the response contains the
27435 requested information. For the commands that resume the target, the
27436 response only indicates whether the target was successfully resumed.
27437 Notifications is the mechanism for reporting changes in the state of the
27438 target, or in @value{GDBN} state, that cannot conveniently be associated with
27439 a command and reported as part of that command response.
27441 The important examples of notifications are:
27445 Exec notifications. These are used to report changes in
27446 target state---when a target is resumed, or stopped. It would not
27447 be feasible to include this information in response of resuming
27448 commands, because one resume commands can result in multiple events in
27449 different threads. Also, quite some time may pass before any event
27450 happens in the target, while a frontend needs to know whether the resuming
27451 command itself was successfully executed.
27454 Console output, and status notifications. Console output
27455 notifications are used to report output of CLI commands, as well as
27456 diagnostics for other commands. Status notifications are used to
27457 report the progress of a long-running operation. Naturally, including
27458 this information in command response would mean no output is produced
27459 until the command is finished, which is undesirable.
27462 General notifications. Commands may have various side effects on
27463 the @value{GDBN} or target state beyond their official purpose. For example,
27464 a command may change the selected thread. Although such changes can
27465 be included in command response, using notification allows for more
27466 orthogonal frontend design.
27470 There's no guarantee that whenever an MI command reports an error,
27471 @value{GDBN} or the target are in any specific state, and especially,
27472 the state is not reverted to the state before the MI command was
27473 processed. Therefore, whenever an MI command results in an error,
27474 we recommend that the frontend refreshes all the information shown in
27475 the user interface.
27479 * Context management::
27480 * Asynchronous and non-stop modes::
27484 @node Context management
27485 @subsection Context management
27487 In most cases when @value{GDBN} accesses the target, this access is
27488 done in context of a specific thread and frame (@pxref{Frames}).
27489 Often, even when accessing global data, the target requires that a thread
27490 be specified. The CLI interface maintains the selected thread and frame,
27491 and supplies them to target on each command. This is convenient,
27492 because a command line user would not want to specify that information
27493 explicitly on each command, and because user interacts with
27494 @value{GDBN} via a single terminal, so no confusion is possible as
27495 to what thread and frame are the current ones.
27497 In the case of MI, the concept of selected thread and frame is less
27498 useful. First, a frontend can easily remember this information
27499 itself. Second, a graphical frontend can have more than one window,
27500 each one used for debugging a different thread, and the frontend might
27501 want to access additional threads for internal purposes. This
27502 increases the risk that by relying on implicitly selected thread, the
27503 frontend may be operating on a wrong one. Therefore, each MI command
27504 should explicitly specify which thread and frame to operate on. To
27505 make it possible, each MI command accepts the @samp{--thread} and
27506 @samp{--frame} options, the value to each is @value{GDBN} identifier
27507 for thread and frame to operate on.
27509 Usually, each top-level window in a frontend allows the user to select
27510 a thread and a frame, and remembers the user selection for further
27511 operations. However, in some cases @value{GDBN} may suggest that the
27512 current thread be changed. For example, when stopping on a breakpoint
27513 it is reasonable to switch to the thread where breakpoint is hit. For
27514 another example, if the user issues the CLI @samp{thread} command via
27515 the frontend, it is desirable to change the frontend's selected thread to the
27516 one specified by user. @value{GDBN} communicates the suggestion to
27517 change current thread using the @samp{=thread-selected} notification.
27518 No such notification is available for the selected frame at the moment.
27520 Note that historically, MI shares the selected thread with CLI, so
27521 frontends used the @code{-thread-select} to execute commands in the
27522 right context. However, getting this to work right is cumbersome. The
27523 simplest way is for frontend to emit @code{-thread-select} command
27524 before every command. This doubles the number of commands that need
27525 to be sent. The alternative approach is to suppress @code{-thread-select}
27526 if the selected thread in @value{GDBN} is supposed to be identical to the
27527 thread the frontend wants to operate on. However, getting this
27528 optimization right can be tricky. In particular, if the frontend
27529 sends several commands to @value{GDBN}, and one of the commands changes the
27530 selected thread, then the behaviour of subsequent commands will
27531 change. So, a frontend should either wait for response from such
27532 problematic commands, or explicitly add @code{-thread-select} for
27533 all subsequent commands. No frontend is known to do this exactly
27534 right, so it is suggested to just always pass the @samp{--thread} and
27535 @samp{--frame} options.
27537 @node Asynchronous and non-stop modes
27538 @subsection Asynchronous command execution and non-stop mode
27540 On some targets, @value{GDBN} is capable of processing MI commands
27541 even while the target is running. This is called @dfn{asynchronous
27542 command execution} (@pxref{Background Execution}). The frontend may
27543 specify a preferrence for asynchronous execution using the
27544 @code{-gdb-set target-async 1} command, which should be emitted before
27545 either running the executable or attaching to the target. After the
27546 frontend has started the executable or attached to the target, it can
27547 find if asynchronous execution is enabled using the
27548 @code{-list-target-features} command.
27550 Even if @value{GDBN} can accept a command while target is running,
27551 many commands that access the target do not work when the target is
27552 running. Therefore, asynchronous command execution is most useful
27553 when combined with non-stop mode (@pxref{Non-Stop Mode}). Then,
27554 it is possible to examine the state of one thread, while other threads
27557 When a given thread is running, MI commands that try to access the
27558 target in the context of that thread may not work, or may work only on
27559 some targets. In particular, commands that try to operate on thread's
27560 stack will not work, on any target. Commands that read memory, or
27561 modify breakpoints, may work or not work, depending on the target. Note
27562 that even commands that operate on global state, such as @code{print},
27563 @code{set}, and breakpoint commands, still access the target in the
27564 context of a specific thread, so frontend should try to find a
27565 stopped thread and perform the operation on that thread (using the
27566 @samp{--thread} option).
27568 Which commands will work in the context of a running thread is
27569 highly target dependent. However, the two commands
27570 @code{-exec-interrupt}, to stop a thread, and @code{-thread-info},
27571 to find the state of a thread, will always work.
27573 @node Thread groups
27574 @subsection Thread groups
27575 @value{GDBN} may be used to debug several processes at the same time.
27576 On some platfroms, @value{GDBN} may support debugging of several
27577 hardware systems, each one having several cores with several different
27578 processes running on each core. This section describes the MI
27579 mechanism to support such debugging scenarios.
27581 The key observation is that regardless of the structure of the
27582 target, MI can have a global list of threads, because most commands that
27583 accept the @samp{--thread} option do not need to know what process that
27584 thread belongs to. Therefore, it is not necessary to introduce
27585 neither additional @samp{--process} option, nor an notion of the
27586 current process in the MI interface. The only strictly new feature
27587 that is required is the ability to find how the threads are grouped
27590 To allow the user to discover such grouping, and to support arbitrary
27591 hierarchy of machines/cores/processes, MI introduces the concept of a
27592 @dfn{thread group}. Thread group is a collection of threads and other
27593 thread groups. A thread group always has a string identifier, a type,
27594 and may have additional attributes specific to the type. A new
27595 command, @code{-list-thread-groups}, returns the list of top-level
27596 thread groups, which correspond to processes that @value{GDBN} is
27597 debugging at the moment. By passing an identifier of a thread group
27598 to the @code{-list-thread-groups} command, it is possible to obtain
27599 the members of specific thread group.
27601 To allow the user to easily discover processes, and other objects, he
27602 wishes to debug, a concept of @dfn{available thread group} is
27603 introduced. Available thread group is an thread group that
27604 @value{GDBN} is not debugging, but that can be attached to, using the
27605 @code{-target-attach} command. The list of available top-level thread
27606 groups can be obtained using @samp{-list-thread-groups --available}.
27607 In general, the content of a thread group may be only retrieved only
27608 after attaching to that thread group.
27610 Thread groups are related to inferiors (@pxref{Inferiors and
27611 Programs}). Each inferior corresponds to a thread group of a special
27612 type @samp{process}, and some additional operations are permitted on
27613 such thread groups.
27615 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27616 @node GDB/MI Command Syntax
27617 @section @sc{gdb/mi} Command Syntax
27620 * GDB/MI Input Syntax::
27621 * GDB/MI Output Syntax::
27624 @node GDB/MI Input Syntax
27625 @subsection @sc{gdb/mi} Input Syntax
27627 @cindex input syntax for @sc{gdb/mi}
27628 @cindex @sc{gdb/mi}, input syntax
27630 @item @var{command} @expansion{}
27631 @code{@var{cli-command} | @var{mi-command}}
27633 @item @var{cli-command} @expansion{}
27634 @code{[ @var{token} ] @var{cli-command} @var{nl}}, where
27635 @var{cli-command} is any existing @value{GDBN} CLI command.
27637 @item @var{mi-command} @expansion{}
27638 @code{[ @var{token} ] "-" @var{operation} ( " " @var{option} )*
27639 @code{[} " --" @code{]} ( " " @var{parameter} )* @var{nl}}
27641 @item @var{token} @expansion{}
27642 "any sequence of digits"
27644 @item @var{option} @expansion{}
27645 @code{"-" @var{parameter} [ " " @var{parameter} ]}
27647 @item @var{parameter} @expansion{}
27648 @code{@var{non-blank-sequence} | @var{c-string}}
27650 @item @var{operation} @expansion{}
27651 @emph{any of the operations described in this chapter}
27653 @item @var{non-blank-sequence} @expansion{}
27654 @emph{anything, provided it doesn't contain special characters such as
27655 "-", @var{nl}, """ and of course " "}
27657 @item @var{c-string} @expansion{}
27658 @code{""" @var{seven-bit-iso-c-string-content} """}
27660 @item @var{nl} @expansion{}
27669 The CLI commands are still handled by the @sc{mi} interpreter; their
27670 output is described below.
27673 The @code{@var{token}}, when present, is passed back when the command
27677 Some @sc{mi} commands accept optional arguments as part of the parameter
27678 list. Each option is identified by a leading @samp{-} (dash) and may be
27679 followed by an optional argument parameter. Options occur first in the
27680 parameter list and can be delimited from normal parameters using
27681 @samp{--} (this is useful when some parameters begin with a dash).
27688 We want easy access to the existing CLI syntax (for debugging).
27691 We want it to be easy to spot a @sc{mi} operation.
27694 @node GDB/MI Output Syntax
27695 @subsection @sc{gdb/mi} Output Syntax
27697 @cindex output syntax of @sc{gdb/mi}
27698 @cindex @sc{gdb/mi}, output syntax
27699 The output from @sc{gdb/mi} consists of zero or more out-of-band records
27700 followed, optionally, by a single result record. This result record
27701 is for the most recent command. The sequence of output records is
27702 terminated by @samp{(gdb)}.
27704 If an input command was prefixed with a @code{@var{token}} then the
27705 corresponding output for that command will also be prefixed by that same
27709 @item @var{output} @expansion{}
27710 @code{( @var{out-of-band-record} )* [ @var{result-record} ] "(gdb)" @var{nl}}
27712 @item @var{result-record} @expansion{}
27713 @code{ [ @var{token} ] "^" @var{result-class} ( "," @var{result} )* @var{nl}}
27715 @item @var{out-of-band-record} @expansion{}
27716 @code{@var{async-record} | @var{stream-record}}
27718 @item @var{async-record} @expansion{}
27719 @code{@var{exec-async-output} | @var{status-async-output} | @var{notify-async-output}}
27721 @item @var{exec-async-output} @expansion{}
27722 @code{[ @var{token} ] "*" @var{async-output}}
27724 @item @var{status-async-output} @expansion{}
27725 @code{[ @var{token} ] "+" @var{async-output}}
27727 @item @var{notify-async-output} @expansion{}
27728 @code{[ @var{token} ] "=" @var{async-output}}
27730 @item @var{async-output} @expansion{}
27731 @code{@var{async-class} ( "," @var{result} )* @var{nl}}
27733 @item @var{result-class} @expansion{}
27734 @code{"done" | "running" | "connected" | "error" | "exit"}
27736 @item @var{async-class} @expansion{}
27737 @code{"stopped" | @var{others}} (where @var{others} will be added
27738 depending on the needs---this is still in development).
27740 @item @var{result} @expansion{}
27741 @code{ @var{variable} "=" @var{value}}
27743 @item @var{variable} @expansion{}
27744 @code{ @var{string} }
27746 @item @var{value} @expansion{}
27747 @code{ @var{const} | @var{tuple} | @var{list} }
27749 @item @var{const} @expansion{}
27750 @code{@var{c-string}}
27752 @item @var{tuple} @expansion{}
27753 @code{ "@{@}" | "@{" @var{result} ( "," @var{result} )* "@}" }
27755 @item @var{list} @expansion{}
27756 @code{ "[]" | "[" @var{value} ( "," @var{value} )* "]" | "["
27757 @var{result} ( "," @var{result} )* "]" }
27759 @item @var{stream-record} @expansion{}
27760 @code{@var{console-stream-output} | @var{target-stream-output} | @var{log-stream-output}}
27762 @item @var{console-stream-output} @expansion{}
27763 @code{"~" @var{c-string}}
27765 @item @var{target-stream-output} @expansion{}
27766 @code{"@@" @var{c-string}}
27768 @item @var{log-stream-output} @expansion{}
27769 @code{"&" @var{c-string}}
27771 @item @var{nl} @expansion{}
27774 @item @var{token} @expansion{}
27775 @emph{any sequence of digits}.
27783 All output sequences end in a single line containing a period.
27786 The @code{@var{token}} is from the corresponding request. Note that
27787 for all async output, while the token is allowed by the grammar and
27788 may be output by future versions of @value{GDBN} for select async
27789 output messages, it is generally omitted. Frontends should treat
27790 all async output as reporting general changes in the state of the
27791 target and there should be no need to associate async output to any
27795 @cindex status output in @sc{gdb/mi}
27796 @var{status-async-output} contains on-going status information about the
27797 progress of a slow operation. It can be discarded. All status output is
27798 prefixed by @samp{+}.
27801 @cindex async output in @sc{gdb/mi}
27802 @var{exec-async-output} contains asynchronous state change on the target
27803 (stopped, started, disappeared). All async output is prefixed by
27807 @cindex notify output in @sc{gdb/mi}
27808 @var{notify-async-output} contains supplementary information that the
27809 client should handle (e.g., a new breakpoint information). All notify
27810 output is prefixed by @samp{=}.
27813 @cindex console output in @sc{gdb/mi}
27814 @var{console-stream-output} is output that should be displayed as is in the
27815 console. It is the textual response to a CLI command. All the console
27816 output is prefixed by @samp{~}.
27819 @cindex target output in @sc{gdb/mi}
27820 @var{target-stream-output} is the output produced by the target program.
27821 All the target output is prefixed by @samp{@@}.
27824 @cindex log output in @sc{gdb/mi}
27825 @var{log-stream-output} is output text coming from @value{GDBN}'s internals, for
27826 instance messages that should be displayed as part of an error log. All
27827 the log output is prefixed by @samp{&}.
27830 @cindex list output in @sc{gdb/mi}
27831 New @sc{gdb/mi} commands should only output @var{lists} containing
27837 @xref{GDB/MI Stream Records, , @sc{gdb/mi} Stream Records}, for more
27838 details about the various output records.
27840 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27841 @node GDB/MI Compatibility with CLI
27842 @section @sc{gdb/mi} Compatibility with CLI
27844 @cindex compatibility, @sc{gdb/mi} and CLI
27845 @cindex @sc{gdb/mi}, compatibility with CLI
27847 For the developers convenience CLI commands can be entered directly,
27848 but there may be some unexpected behaviour. For example, commands
27849 that query the user will behave as if the user replied yes, breakpoint
27850 command lists are not executed and some CLI commands, such as
27851 @code{if}, @code{when} and @code{define}, prompt for further input with
27852 @samp{>}, which is not valid MI output.
27854 This feature may be removed at some stage in the future and it is
27855 recommended that front ends use the @code{-interpreter-exec} command
27856 (@pxref{-interpreter-exec}).
27858 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27859 @node GDB/MI Development and Front Ends
27860 @section @sc{gdb/mi} Development and Front Ends
27861 @cindex @sc{gdb/mi} development
27863 The application which takes the MI output and presents the state of the
27864 program being debugged to the user is called a @dfn{front end}.
27866 Although @sc{gdb/mi} is still incomplete, it is currently being used
27867 by a variety of front ends to @value{GDBN}. This makes it difficult
27868 to introduce new functionality without breaking existing usage. This
27869 section tries to minimize the problems by describing how the protocol
27872 Some changes in MI need not break a carefully designed front end, and
27873 for these the MI version will remain unchanged. The following is a
27874 list of changes that may occur within one level, so front ends should
27875 parse MI output in a way that can handle them:
27879 New MI commands may be added.
27882 New fields may be added to the output of any MI command.
27885 The range of values for fields with specified values, e.g.,
27886 @code{in_scope} (@pxref{-var-update}) may be extended.
27888 @c The format of field's content e.g type prefix, may change so parse it
27889 @c at your own risk. Yes, in general?
27891 @c The order of fields may change? Shouldn't really matter but it might
27892 @c resolve inconsistencies.
27895 If the changes are likely to break front ends, the MI version level
27896 will be increased by one. This will allow the front end to parse the
27897 output according to the MI version. Apart from mi0, new versions of
27898 @value{GDBN} will not support old versions of MI and it will be the
27899 responsibility of the front end to work with the new one.
27901 @c Starting with mi3, add a new command -mi-version that prints the MI
27904 The best way to avoid unexpected changes in MI that might break your front
27905 end is to make your project known to @value{GDBN} developers and
27906 follow development on @email{gdb@@sourceware.org} and
27907 @email{gdb-patches@@sourceware.org}.
27908 @cindex mailing lists
27910 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
27911 @node GDB/MI Output Records
27912 @section @sc{gdb/mi} Output Records
27915 * GDB/MI Result Records::
27916 * GDB/MI Stream Records::
27917 * GDB/MI Async Records::
27918 * GDB/MI Breakpoint Information::
27919 * GDB/MI Frame Information::
27920 * GDB/MI Thread Information::
27921 * GDB/MI Ada Exception Information::
27924 @node GDB/MI Result Records
27925 @subsection @sc{gdb/mi} Result Records
27927 @cindex result records in @sc{gdb/mi}
27928 @cindex @sc{gdb/mi}, result records
27929 In addition to a number of out-of-band notifications, the response to a
27930 @sc{gdb/mi} command includes one of the following result indications:
27934 @item "^done" [ "," @var{results} ]
27935 The synchronous operation was successful, @code{@var{results}} are the return
27940 This result record is equivalent to @samp{^done}. Historically, it
27941 was output instead of @samp{^done} if the command has resumed the
27942 target. This behaviour is maintained for backward compatibility, but
27943 all frontends should treat @samp{^done} and @samp{^running}
27944 identically and rely on the @samp{*running} output record to determine
27945 which threads are resumed.
27949 @value{GDBN} has connected to a remote target.
27951 @item "^error" "," @var{c-string}
27953 The operation failed. The @code{@var{c-string}} contains the corresponding
27958 @value{GDBN} has terminated.
27962 @node GDB/MI Stream Records
27963 @subsection @sc{gdb/mi} Stream Records
27965 @cindex @sc{gdb/mi}, stream records
27966 @cindex stream records in @sc{gdb/mi}
27967 @value{GDBN} internally maintains a number of output streams: the console, the
27968 target, and the log. The output intended for each of these streams is
27969 funneled through the @sc{gdb/mi} interface using @dfn{stream records}.
27971 Each stream record begins with a unique @dfn{prefix character} which
27972 identifies its stream (@pxref{GDB/MI Output Syntax, , @sc{gdb/mi} Output
27973 Syntax}). In addition to the prefix, each stream record contains a
27974 @code{@var{string-output}}. This is either raw text (with an implicit new
27975 line) or a quoted C string (which does not contain an implicit newline).
27978 @item "~" @var{string-output}
27979 The console output stream contains text that should be displayed in the
27980 CLI console window. It contains the textual responses to CLI commands.
27982 @item "@@" @var{string-output}
27983 The target output stream contains any textual output from the running
27984 target. This is only present when GDB's event loop is truly
27985 asynchronous, which is currently only the case for remote targets.
27987 @item "&" @var{string-output}
27988 The log stream contains debugging messages being produced by @value{GDBN}'s
27992 @node GDB/MI Async Records
27993 @subsection @sc{gdb/mi} Async Records
27995 @cindex async records in @sc{gdb/mi}
27996 @cindex @sc{gdb/mi}, async records
27997 @dfn{Async} records are used to notify the @sc{gdb/mi} client of
27998 additional changes that have occurred. Those changes can either be a
27999 consequence of @sc{gdb/mi} commands (e.g., a breakpoint modified) or a result of
28000 target activity (e.g., target stopped).
28002 The following is the list of possible async records:
28006 @item *running,thread-id="@var{thread}"
28007 The target is now running. The @var{thread} field tells which
28008 specific thread is now running, and can be @samp{all} if all threads
28009 are running. The frontend should assume that no interaction with a
28010 running thread is possible after this notification is produced.
28011 The frontend should not assume that this notification is output
28012 only once for any command. @value{GDBN} may emit this notification
28013 several times, either for different threads, because it cannot resume
28014 all threads together, or even for a single thread, if the thread must
28015 be stepped though some code before letting it run freely.
28017 @item *stopped,reason="@var{reason}",thread-id="@var{id}",stopped-threads="@var{stopped}",core="@var{core}"
28018 The target has stopped. The @var{reason} field can have one of the
28022 @item breakpoint-hit
28023 A breakpoint was reached.
28024 @item watchpoint-trigger
28025 A watchpoint was triggered.
28026 @item read-watchpoint-trigger
28027 A read watchpoint was triggered.
28028 @item access-watchpoint-trigger
28029 An access watchpoint was triggered.
28030 @item function-finished
28031 An -exec-finish or similar CLI command was accomplished.
28032 @item location-reached
28033 An -exec-until or similar CLI command was accomplished.
28034 @item watchpoint-scope
28035 A watchpoint has gone out of scope.
28036 @item end-stepping-range
28037 An -exec-next, -exec-next-instruction, -exec-step, -exec-step-instruction or
28038 similar CLI command was accomplished.
28039 @item exited-signalled
28040 The inferior exited because of a signal.
28042 The inferior exited.
28043 @item exited-normally
28044 The inferior exited normally.
28045 @item signal-received
28046 A signal was received by the inferior.
28048 The inferior has stopped due to a library being loaded or unloaded.
28049 This can happen when @code{stop-on-solib-events} (@pxref{Files}) is
28050 set or when a @code{catch load} or @code{catch unload} catchpoint is
28051 in use (@pxref{Set Catchpoints}).
28053 The inferior has forked. This is reported when @code{catch fork}
28054 (@pxref{Set Catchpoints}) has been used.
28056 The inferior has vforked. This is reported in when @code{catch vfork}
28057 (@pxref{Set Catchpoints}) has been used.
28058 @item syscall-entry
28059 The inferior entered a system call. This is reported when @code{catch
28060 syscall} (@pxref{Set Catchpoints}) has been used.
28061 @item syscall-entry
28062 The inferior returned from a system call. This is reported when
28063 @code{catch syscall} (@pxref{Set Catchpoints}) has been used.
28065 The inferior called @code{exec}. This is reported when @code{catch exec}
28066 (@pxref{Set Catchpoints}) has been used.
28069 The @var{id} field identifies the thread that directly caused the stop
28070 -- for example by hitting a breakpoint. Depending on whether all-stop
28071 mode is in effect (@pxref{All-Stop Mode}), @value{GDBN} may either
28072 stop all threads, or only the thread that directly triggered the stop.
28073 If all threads are stopped, the @var{stopped} field will have the
28074 value of @code{"all"}. Otherwise, the value of the @var{stopped}
28075 field will be a list of thread identifiers. Presently, this list will
28076 always include a single thread, but frontend should be prepared to see
28077 several threads in the list. The @var{core} field reports the
28078 processor core on which the stop event has happened. This field may be absent
28079 if such information is not available.
28081 @item =thread-group-added,id="@var{id}"
28082 @itemx =thread-group-removed,id="@var{id}"
28083 A thread group was either added or removed. The @var{id} field
28084 contains the @value{GDBN} identifier of the thread group. When a thread
28085 group is added, it generally might not be associated with a running
28086 process. When a thread group is removed, its id becomes invalid and
28087 cannot be used in any way.
28089 @item =thread-group-started,id="@var{id}",pid="@var{pid}"
28090 A thread group became associated with a running program,
28091 either because the program was just started or the thread group
28092 was attached to a program. The @var{id} field contains the
28093 @value{GDBN} identifier of the thread group. The @var{pid} field
28094 contains process identifier, specific to the operating system.
28096 @item =thread-group-exited,id="@var{id}"[,exit-code="@var{code}"]
28097 A thread group is no longer associated with a running program,
28098 either because the program has exited, or because it was detached
28099 from. The @var{id} field contains the @value{GDBN} identifier of the
28100 thread group. @var{code} is the exit code of the inferior; it exists
28101 only when the inferior exited with some code.
28103 @item =thread-created,id="@var{id}",group-id="@var{gid}"
28104 @itemx =thread-exited,id="@var{id}",group-id="@var{gid}"
28105 A thread either was created, or has exited. The @var{id} field
28106 contains the @value{GDBN} identifier of the thread. The @var{gid}
28107 field identifies the thread group this thread belongs to.
28109 @item =thread-selected,id="@var{id}"
28110 Informs that the selected thread was changed as result of the last
28111 command. This notification is not emitted as result of @code{-thread-select}
28112 command but is emitted whenever an MI command that is not documented
28113 to change the selected thread actually changes it. In particular,
28114 invoking, directly or indirectly (via user-defined command), the CLI
28115 @code{thread} command, will generate this notification.
28117 We suggest that in response to this notification, front ends
28118 highlight the selected thread and cause subsequent commands to apply to
28121 @item =library-loaded,...
28122 Reports that a new library file was loaded by the program. This
28123 notification has 4 fields---@var{id}, @var{target-name},
28124 @var{host-name}, and @var{symbols-loaded}. The @var{id} field is an
28125 opaque identifier of the library. For remote debugging case,
28126 @var{target-name} and @var{host-name} fields give the name of the
28127 library file on the target, and on the host respectively. For native
28128 debugging, both those fields have the same value. The
28129 @var{symbols-loaded} field is emitted only for backward compatibility
28130 and should not be relied on to convey any useful information. The
28131 @var{thread-group} field, if present, specifies the id of the thread
28132 group in whose context the library was loaded. If the field is
28133 absent, it means the library was loaded in the context of all present
28136 @item =library-unloaded,...
28137 Reports that a library was unloaded by the program. This notification
28138 has 3 fields---@var{id}, @var{target-name} and @var{host-name} with
28139 the same meaning as for the @code{=library-loaded} notification.
28140 The @var{thread-group} field, if present, specifies the id of the
28141 thread group in whose context the library was unloaded. If the field is
28142 absent, it means the library was unloaded in the context of all present
28145 @item =traceframe-changed,num=@var{tfnum},tracepoint=@var{tpnum}
28146 @itemx =traceframe-changed,end
28147 Reports that the trace frame was changed and its new number is
28148 @var{tfnum}. The number of the tracepoint associated with this trace
28149 frame is @var{tpnum}.
28151 @item =tsv-created,name=@var{name},initial=@var{initial}
28152 Reports that the new trace state variable @var{name} is created with
28153 initial value @var{initial}.
28155 @item =tsv-deleted,name=@var{name}
28156 @itemx =tsv-deleted
28157 Reports that the trace state variable @var{name} is deleted or all
28158 trace state variables are deleted.
28160 @item =tsv-modified,name=@var{name},initial=@var{initial}[,current=@var{current}]
28161 Reports that the trace state variable @var{name} is modified with
28162 the initial value @var{initial}. The current value @var{current} of
28163 trace state variable is optional and is reported if the current
28164 value of trace state variable is known.
28166 @item =breakpoint-created,bkpt=@{...@}
28167 @itemx =breakpoint-modified,bkpt=@{...@}
28168 @itemx =breakpoint-deleted,id=@var{number}
28169 Reports that a breakpoint was created, modified, or deleted,
28170 respectively. Only user-visible breakpoints are reported to the MI
28173 The @var{bkpt} argument is of the same form as returned by the various
28174 breakpoint commands; @xref{GDB/MI Breakpoint Commands}. The
28175 @var{number} is the ordinal number of the breakpoint.
28177 Note that if a breakpoint is emitted in the result record of a
28178 command, then it will not also be emitted in an async record.
28180 @item =record-started,thread-group="@var{id}"
28181 @itemx =record-stopped,thread-group="@var{id}"
28182 Execution log recording was either started or stopped on an
28183 inferior. The @var{id} is the @value{GDBN} identifier of the thread
28184 group corresponding to the affected inferior.
28186 @item =cmd-param-changed,param=@var{param},value=@var{value}
28187 Reports that a parameter of the command @code{set @var{param}} is
28188 changed to @var{value}. In the multi-word @code{set} command,
28189 the @var{param} is the whole parameter list to @code{set} command.
28190 For example, In command @code{set check type on}, @var{param}
28191 is @code{check type} and @var{value} is @code{on}.
28193 @item =memory-changed,thread-group=@var{id},addr=@var{addr},len=@var{len}[,type="code"]
28194 Reports that bytes from @var{addr} to @var{data} + @var{len} were
28195 written in an inferior. The @var{id} is the identifier of the
28196 thread group corresponding to the affected inferior. The optional
28197 @code{type="code"} part is reported if the memory written to holds
28201 @node GDB/MI Breakpoint Information
28202 @subsection @sc{gdb/mi} Breakpoint Information
28204 When @value{GDBN} reports information about a breakpoint, a
28205 tracepoint, a watchpoint, or a catchpoint, it uses a tuple with the
28210 The breakpoint number. For a breakpoint that represents one location
28211 of a multi-location breakpoint, this will be a dotted pair, like
28215 The type of the breakpoint. For ordinary breakpoints this will be
28216 @samp{breakpoint}, but many values are possible.
28219 If the type of the breakpoint is @samp{catchpoint}, then this
28220 indicates the exact type of catchpoint.
28223 This is the breakpoint disposition---either @samp{del}, meaning that
28224 the breakpoint will be deleted at the next stop, or @samp{keep},
28225 meaning that the breakpoint will not be deleted.
28228 This indicates whether the breakpoint is enabled, in which case the
28229 value is @samp{y}, or disabled, in which case the value is @samp{n}.
28230 Note that this is not the same as the field @code{enable}.
28233 The address of the breakpoint. This may be a hexidecimal number,
28234 giving the address; or the string @samp{<PENDING>}, for a pending
28235 breakpoint; or the string @samp{<MULTIPLE>}, for a breakpoint with
28236 multiple locations. This field will not be present if no address can
28237 be determined. For example, a watchpoint does not have an address.
28240 If known, the function in which the breakpoint appears.
28241 If not known, this field is not present.
28244 The name of the source file which contains this function, if known.
28245 If not known, this field is not present.
28248 The full file name of the source file which contains this function, if
28249 known. If not known, this field is not present.
28252 The line number at which this breakpoint appears, if known.
28253 If not known, this field is not present.
28256 If the source file is not known, this field may be provided. If
28257 provided, this holds the address of the breakpoint, possibly followed
28261 If this breakpoint is pending, this field is present and holds the
28262 text used to set the breakpoint, as entered by the user.
28265 Where this breakpoint's condition is evaluated, either @samp{host} or
28269 If this is a thread-specific breakpoint, then this identifies the
28270 thread in which the breakpoint can trigger.
28273 If this breakpoint is restricted to a particular Ada task, then this
28274 field will hold the task identifier.
28277 If the breakpoint is conditional, this is the condition expression.
28280 The ignore count of the breakpoint.
28283 The enable count of the breakpoint.
28285 @item traceframe-usage
28288 @item static-tracepoint-marker-string-id
28289 For a static tracepoint, the name of the static tracepoint marker.
28292 For a masked watchpoint, this is the mask.
28295 A tracepoint's pass count.
28297 @item original-location
28298 The location of the breakpoint as originally specified by the user.
28299 This field is optional.
28302 The number of times the breakpoint has been hit.
28305 This field is only given for tracepoints. This is either @samp{y},
28306 meaning that the tracepoint is installed, or @samp{n}, meaning that it
28310 Some extra data, the exact contents of which are type-dependent.
28314 For example, here is what the output of @code{-break-insert}
28315 (@pxref{GDB/MI Breakpoint Commands}) might be:
28318 -> -break-insert main
28319 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28320 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28321 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28326 @node GDB/MI Frame Information
28327 @subsection @sc{gdb/mi} Frame Information
28329 Response from many MI commands includes an information about stack
28330 frame. This information is a tuple that may have the following
28335 The level of the stack frame. The innermost frame has the level of
28336 zero. This field is always present.
28339 The name of the function corresponding to the frame. This field may
28340 be absent if @value{GDBN} is unable to determine the function name.
28343 The code address for the frame. This field is always present.
28346 The name of the source files that correspond to the frame's code
28347 address. This field may be absent.
28350 The source line corresponding to the frames' code address. This field
28354 The name of the binary file (either executable or shared library) the
28355 corresponds to the frame's code address. This field may be absent.
28359 @node GDB/MI Thread Information
28360 @subsection @sc{gdb/mi} Thread Information
28362 Whenever @value{GDBN} has to report an information about a thread, it
28363 uses a tuple with the following fields:
28367 The numeric id assigned to the thread by @value{GDBN}. This field is
28371 Target-specific string identifying the thread. This field is always present.
28374 Additional information about the thread provided by the target.
28375 It is supposed to be human-readable and not interpreted by the
28376 frontend. This field is optional.
28379 Either @samp{stopped} or @samp{running}, depending on whether the
28380 thread is presently running. This field is always present.
28383 The value of this field is an integer number of the processor core the
28384 thread was last seen on. This field is optional.
28387 @node GDB/MI Ada Exception Information
28388 @subsection @sc{gdb/mi} Ada Exception Information
28390 Whenever a @code{*stopped} record is emitted because the program
28391 stopped after hitting an exception catchpoint (@pxref{Set Catchpoints}),
28392 @value{GDBN} provides the name of the exception that was raised via
28393 the @code{exception-name} field.
28395 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28396 @node GDB/MI Simple Examples
28397 @section Simple Examples of @sc{gdb/mi} Interaction
28398 @cindex @sc{gdb/mi}, simple examples
28400 This subsection presents several simple examples of interaction using
28401 the @sc{gdb/mi} interface. In these examples, @samp{->} means that the
28402 following line is passed to @sc{gdb/mi} as input, while @samp{<-} means
28403 the output received from @sc{gdb/mi}.
28405 Note the line breaks shown in the examples are here only for
28406 readability, they don't appear in the real output.
28408 @subheading Setting a Breakpoint
28410 Setting a breakpoint generates synchronous output which contains detailed
28411 information of the breakpoint.
28414 -> -break-insert main
28415 <- ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28416 enabled="y",addr="0x08048564",func="main",file="myprog.c",
28417 fullname="/home/nickrob/myprog.c",line="68",thread-groups=["i1"],
28422 @subheading Program Execution
28424 Program execution generates asynchronous records and MI gives the
28425 reason that execution stopped.
28431 <- *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
28432 frame=@{addr="0x08048564",func="main",
28433 args=[@{name="argc",value="1"@},@{name="argv",value="0xbfc4d4d4"@}],
28434 file="myprog.c",fullname="/home/nickrob/myprog.c",line="68"@}
28439 <- *stopped,reason="exited-normally"
28443 @subheading Quitting @value{GDBN}
28445 Quitting @value{GDBN} just prints the result class @samp{^exit}.
28453 Please note that @samp{^exit} is printed immediately, but it might
28454 take some time for @value{GDBN} to actually exit. During that time, @value{GDBN}
28455 performs necessary cleanups, including killing programs being debugged
28456 or disconnecting from debug hardware, so the frontend should wait till
28457 @value{GDBN} exits and should only forcibly kill @value{GDBN} if it
28458 fails to exit in reasonable time.
28460 @subheading A Bad Command
28462 Here's what happens if you pass a non-existent command:
28466 <- ^error,msg="Undefined MI command: rubbish"
28471 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28472 @node GDB/MI Command Description Format
28473 @section @sc{gdb/mi} Command Description Format
28475 The remaining sections describe blocks of commands. Each block of
28476 commands is laid out in a fashion similar to this section.
28478 @subheading Motivation
28480 The motivation for this collection of commands.
28482 @subheading Introduction
28484 A brief introduction to this collection of commands as a whole.
28486 @subheading Commands
28488 For each command in the block, the following is described:
28490 @subsubheading Synopsis
28493 -command @var{args}@dots{}
28496 @subsubheading Result
28498 @subsubheading @value{GDBN} Command
28500 The corresponding @value{GDBN} CLI command(s), if any.
28502 @subsubheading Example
28504 Example(s) formatted for readability. Some of the described commands have
28505 not been implemented yet and these are labeled N.A.@: (not available).
28508 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
28509 @node GDB/MI Breakpoint Commands
28510 @section @sc{gdb/mi} Breakpoint Commands
28512 @cindex breakpoint commands for @sc{gdb/mi}
28513 @cindex @sc{gdb/mi}, breakpoint commands
28514 This section documents @sc{gdb/mi} commands for manipulating
28517 @subheading The @code{-break-after} Command
28518 @findex -break-after
28520 @subsubheading Synopsis
28523 -break-after @var{number} @var{count}
28526 The breakpoint number @var{number} is not in effect until it has been
28527 hit @var{count} times. To see how this is reflected in the output of
28528 the @samp{-break-list} command, see the description of the
28529 @samp{-break-list} command below.
28531 @subsubheading @value{GDBN} Command
28533 The corresponding @value{GDBN} command is @samp{ignore}.
28535 @subsubheading Example
28540 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28541 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28542 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28550 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28551 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28552 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28553 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28554 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28555 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28556 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28557 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28558 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28559 line="5",thread-groups=["i1"],times="0",ignore="3"@}]@}
28564 @subheading The @code{-break-catch} Command
28565 @findex -break-catch
28568 @subheading The @code{-break-commands} Command
28569 @findex -break-commands
28571 @subsubheading Synopsis
28574 -break-commands @var{number} [ @var{command1} ... @var{commandN} ]
28577 Specifies the CLI commands that should be executed when breakpoint
28578 @var{number} is hit. The parameters @var{command1} to @var{commandN}
28579 are the commands. If no command is specified, any previously-set
28580 commands are cleared. @xref{Break Commands}. Typical use of this
28581 functionality is tracing a program, that is, printing of values of
28582 some variables whenever breakpoint is hit and then continuing.
28584 @subsubheading @value{GDBN} Command
28586 The corresponding @value{GDBN} command is @samp{commands}.
28588 @subsubheading Example
28593 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",
28594 enabled="y",addr="0x000100d0",func="main",file="hello.c",
28595 fullname="/home/foo/hello.c",line="5",thread-groups=["i1"],
28598 -break-commands 1 "print v" "continue"
28603 @subheading The @code{-break-condition} Command
28604 @findex -break-condition
28606 @subsubheading Synopsis
28609 -break-condition @var{number} @var{expr}
28612 Breakpoint @var{number} will stop the program only if the condition in
28613 @var{expr} is true. The condition becomes part of the
28614 @samp{-break-list} output (see the description of the @samp{-break-list}
28617 @subsubheading @value{GDBN} Command
28619 The corresponding @value{GDBN} command is @samp{condition}.
28621 @subsubheading Example
28625 -break-condition 1 1
28629 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28630 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28631 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28632 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28633 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28634 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28635 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28636 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28637 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28638 line="5",cond="1",thread-groups=["i1"],times="0",ignore="3"@}]@}
28642 @subheading The @code{-break-delete} Command
28643 @findex -break-delete
28645 @subsubheading Synopsis
28648 -break-delete ( @var{breakpoint} )+
28651 Delete the breakpoint(s) whose number(s) are specified in the argument
28652 list. This is obviously reflected in the breakpoint list.
28654 @subsubheading @value{GDBN} Command
28656 The corresponding @value{GDBN} command is @samp{delete}.
28658 @subsubheading Example
28666 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28667 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28668 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28669 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28670 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28671 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28672 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28677 @subheading The @code{-break-disable} Command
28678 @findex -break-disable
28680 @subsubheading Synopsis
28683 -break-disable ( @var{breakpoint} )+
28686 Disable the named @var{breakpoint}(s). The field @samp{enabled} in the
28687 break list is now set to @samp{n} for the named @var{breakpoint}(s).
28689 @subsubheading @value{GDBN} Command
28691 The corresponding @value{GDBN} command is @samp{disable}.
28693 @subsubheading Example
28701 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28702 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28703 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28704 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28705 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28706 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28707 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28708 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="n",
28709 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28710 line="5",thread-groups=["i1"],times="0"@}]@}
28714 @subheading The @code{-break-enable} Command
28715 @findex -break-enable
28717 @subsubheading Synopsis
28720 -break-enable ( @var{breakpoint} )+
28723 Enable (previously disabled) @var{breakpoint}(s).
28725 @subsubheading @value{GDBN} Command
28727 The corresponding @value{GDBN} command is @samp{enable}.
28729 @subsubheading Example
28737 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
28738 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28739 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28740 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28741 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28742 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28743 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28744 body=[bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28745 addr="0x000100d0",func="main",file="hello.c",fullname="/home/foo/hello.c",
28746 line="5",thread-groups=["i1"],times="0"@}]@}
28750 @subheading The @code{-break-info} Command
28751 @findex -break-info
28753 @subsubheading Synopsis
28756 -break-info @var{breakpoint}
28760 Get information about a single breakpoint.
28762 The result is a table of breakpoints. @xref{GDB/MI Breakpoint
28763 Information}, for details on the format of each breakpoint in the
28766 @subsubheading @value{GDBN} Command
28768 The corresponding @value{GDBN} command is @samp{info break @var{breakpoint}}.
28770 @subsubheading Example
28773 @subheading The @code{-break-insert} Command
28774 @findex -break-insert
28776 @subsubheading Synopsis
28779 -break-insert [ -t ] [ -h ] [ -f ] [ -d ] [ -a ]
28780 [ -c @var{condition} ] [ -i @var{ignore-count} ]
28781 [ -p @var{thread-id} ] [ @var{location} ]
28785 If specified, @var{location}, can be one of:
28792 @item filename:linenum
28793 @item filename:function
28797 The possible optional parameters of this command are:
28801 Insert a temporary breakpoint.
28803 Insert a hardware breakpoint.
28805 If @var{location} cannot be parsed (for example if it
28806 refers to unknown files or functions), create a pending
28807 breakpoint. Without this flag, @value{GDBN} will report
28808 an error, and won't create a breakpoint, if @var{location}
28811 Create a disabled breakpoint.
28813 Create a tracepoint. @xref{Tracepoints}. When this parameter
28814 is used together with @samp{-h}, a fast tracepoint is created.
28815 @item -c @var{condition}
28816 Make the breakpoint conditional on @var{condition}.
28817 @item -i @var{ignore-count}
28818 Initialize the @var{ignore-count}.
28819 @item -p @var{thread-id}
28820 Restrict the breakpoint to the specified @var{thread-id}.
28823 @subsubheading Result
28825 @xref{GDB/MI Breakpoint Information}, for details on the format of the
28826 resulting breakpoint.
28828 Note: this format is open to change.
28829 @c An out-of-band breakpoint instead of part of the result?
28831 @subsubheading @value{GDBN} Command
28833 The corresponding @value{GDBN} commands are @samp{break}, @samp{tbreak},
28834 @samp{hbreak}, and @samp{thbreak}. @c and @samp{rbreak}.
28836 @subsubheading Example
28841 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",
28842 fullname="/home/foo/recursive2.c,line="4",thread-groups=["i1"],
28845 -break-insert -t foo
28846 ^done,bkpt=@{number="2",addr="0x00010774",file="recursive2.c",
28847 fullname="/home/foo/recursive2.c,line="11",thread-groups=["i1"],
28851 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28852 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28853 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28854 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28855 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28856 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28857 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28858 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28859 addr="0x0001072c", func="main",file="recursive2.c",
28860 fullname="/home/foo/recursive2.c,"line="4",thread-groups=["i1"],
28862 bkpt=@{number="2",type="breakpoint",disp="del",enabled="y",
28863 addr="0x00010774",func="foo",file="recursive2.c",
28864 fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28867 @c -break-insert -r foo.*
28868 @c ~int foo(int, int);
28869 @c ^done,bkpt=@{number="3",addr="0x00010774",file="recursive2.c,
28870 @c "fullname="/home/foo/recursive2.c",line="11",thread-groups=["i1"],
28875 @subheading The @code{-break-list} Command
28876 @findex -break-list
28878 @subsubheading Synopsis
28884 Displays the list of inserted breakpoints, showing the following fields:
28888 number of the breakpoint
28890 type of the breakpoint: @samp{breakpoint} or @samp{watchpoint}
28892 should the breakpoint be deleted or disabled when it is hit: @samp{keep}
28895 is the breakpoint enabled or no: @samp{y} or @samp{n}
28897 memory location at which the breakpoint is set
28899 logical location of the breakpoint, expressed by function name, file
28901 @item Thread-groups
28902 list of thread groups to which this breakpoint applies
28904 number of times the breakpoint has been hit
28907 If there are no breakpoints or watchpoints, the @code{BreakpointTable}
28908 @code{body} field is an empty list.
28910 @subsubheading @value{GDBN} Command
28912 The corresponding @value{GDBN} command is @samp{info break}.
28914 @subsubheading Example
28919 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
28920 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28921 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28922 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28923 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28924 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28925 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28926 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
28927 addr="0x000100d0",func="main",file="hello.c",line="5",thread-groups=["i1"],
28929 bkpt=@{number="2",type="breakpoint",disp="keep",enabled="y",
28930 addr="0x00010114",func="foo",file="hello.c",fullname="/home/foo/hello.c",
28931 line="13",thread-groups=["i1"],times="0"@}]@}
28935 Here's an example of the result when there are no breakpoints:
28940 ^done,BreakpointTable=@{nr_rows="0",nr_cols="6",
28941 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
28942 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
28943 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
28944 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
28945 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
28946 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
28951 @subheading The @code{-break-passcount} Command
28952 @findex -break-passcount
28954 @subsubheading Synopsis
28957 -break-passcount @var{tracepoint-number} @var{passcount}
28960 Set the passcount for tracepoint @var{tracepoint-number} to
28961 @var{passcount}. If the breakpoint referred to by @var{tracepoint-number}
28962 is not a tracepoint, error is emitted. This corresponds to CLI
28963 command @samp{passcount}.
28965 @subheading The @code{-break-watch} Command
28966 @findex -break-watch
28968 @subsubheading Synopsis
28971 -break-watch [ -a | -r ]
28974 Create a watchpoint. With the @samp{-a} option it will create an
28975 @dfn{access} watchpoint, i.e., a watchpoint that triggers either on a
28976 read from or on a write to the memory location. With the @samp{-r}
28977 option, the watchpoint created is a @dfn{read} watchpoint, i.e., it will
28978 trigger only when the memory location is accessed for reading. Without
28979 either of the options, the watchpoint created is a regular watchpoint,
28980 i.e., it will trigger when the memory location is accessed for writing.
28981 @xref{Set Watchpoints, , Setting Watchpoints}.
28983 Note that @samp{-break-list} will report a single list of watchpoints and
28984 breakpoints inserted.
28986 @subsubheading @value{GDBN} Command
28988 The corresponding @value{GDBN} commands are @samp{watch}, @samp{awatch}, and
28991 @subsubheading Example
28993 Setting a watchpoint on a variable in the @code{main} function:
28998 ^done,wpt=@{number="2",exp="x"@}
29003 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="x"@},
29004 value=@{old="-268439212",new="55"@},
29005 frame=@{func="main",args=[],file="recursive2.c",
29006 fullname="/home/foo/bar/recursive2.c",line="5"@}
29010 Setting a watchpoint on a variable local to a function. @value{GDBN} will stop
29011 the program execution twice: first for the variable changing value, then
29012 for the watchpoint going out of scope.
29017 ^done,wpt=@{number="5",exp="C"@}
29022 *stopped,reason="watchpoint-trigger",
29023 wpt=@{number="5",exp="C"@},value=@{old="-276895068",new="3"@},
29024 frame=@{func="callee4",args=[],
29025 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29026 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29031 *stopped,reason="watchpoint-scope",wpnum="5",
29032 frame=@{func="callee3",args=[@{name="strarg",
29033 value="0x11940 \"A string argument.\""@}],
29034 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29035 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29039 Listing breakpoints and watchpoints, at different points in the program
29040 execution. Note that once the watchpoint goes out of scope, it is
29046 ^done,wpt=@{number="2",exp="C"@}
29049 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29050 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29051 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29052 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29053 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29054 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29055 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29056 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29057 addr="0x00010734",func="callee4",
29058 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29059 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c"line="8",thread-groups=["i1"],
29061 bkpt=@{number="2",type="watchpoint",disp="keep",
29062 enabled="y",addr="",what="C",thread-groups=["i1"],times="0"@}]@}
29067 *stopped,reason="watchpoint-trigger",wpt=@{number="2",exp="C"@},
29068 value=@{old="-276895068",new="3"@},
29069 frame=@{func="callee4",args=[],
29070 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29071 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="13"@}
29074 ^done,BreakpointTable=@{nr_rows="2",nr_cols="6",
29075 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29076 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29077 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29078 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29079 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29080 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29081 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29082 addr="0x00010734",func="callee4",
29083 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29084 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",thread-groups=["i1"],
29086 bkpt=@{number="2",type="watchpoint",disp="keep",
29087 enabled="y",addr="",what="C",thread-groups=["i1"],times="-5"@}]@}
29091 ^done,reason="watchpoint-scope",wpnum="2",
29092 frame=@{func="callee3",args=[@{name="strarg",
29093 value="0x11940 \"A string argument.\""@}],
29094 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29095 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29098 ^done,BreakpointTable=@{nr_rows="1",nr_cols="6",
29099 hdr=[@{width="3",alignment="-1",col_name="number",colhdr="Num"@},
29100 @{width="14",alignment="-1",col_name="type",colhdr="Type"@},
29101 @{width="4",alignment="-1",col_name="disp",colhdr="Disp"@},
29102 @{width="3",alignment="-1",col_name="enabled",colhdr="Enb"@},
29103 @{width="10",alignment="-1",col_name="addr",colhdr="Address"@},
29104 @{width="40",alignment="2",col_name="what",colhdr="What"@}],
29105 body=[bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
29106 addr="0x00010734",func="callee4",
29107 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29108 fullname="/home/foo/devo/gdb/testsuite/gdb.mi/basics.c",line="8",
29109 thread-groups=["i1"],times="1"@}]@}
29114 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29115 @node GDB/MI Catchpoint Commands
29116 @section @sc{gdb/mi} Catchpoint Commands
29118 This section documents @sc{gdb/mi} commands for manipulating
29121 @subheading The @code{-catch-load} Command
29122 @findex -catch-load
29124 @subsubheading Synopsis
29127 -catch-load [ -t ] [ -d ] @var{regexp}
29130 Add a catchpoint for library load events. If the @samp{-t} option is used,
29131 the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29132 Breakpoints}). If the @samp{-d} option is used, the catchpoint is created
29133 in a disabled state. The @samp{regexp} argument is a regular
29134 expression used to match the name of the loaded library.
29137 @subsubheading @value{GDBN} Command
29139 The corresponding @value{GDBN} command is @samp{catch load}.
29141 @subsubheading Example
29144 -catch-load -t foo.so
29145 ^done,bkpt=@{number="1",type="catchpoint",disp="del",enabled="y",
29146 what="load of library matching foo.so",catch-type="load",times="0"@}
29151 @subheading The @code{-catch-unload} Command
29152 @findex -catch-unload
29154 @subsubheading Synopsis
29157 -catch-unload [ -t ] [ -d ] @var{regexp}
29160 Add a catchpoint for library unload events. If the @samp{-t} option is
29161 used, the catchpoint is a temporary one (@pxref{Set Breaks, ,Setting
29162 Breakpoints}). If the @samp{-d} option is used, the catchpoint is
29163 created in a disabled state. The @samp{regexp} argument is a regular
29164 expression used to match the name of the unloaded library.
29166 @subsubheading @value{GDBN} Command
29168 The corresponding @value{GDBN} command is @samp{catch unload}.
29170 @subsubheading Example
29173 -catch-unload -d bar.so
29174 ^done,bkpt=@{number="2",type="catchpoint",disp="keep",enabled="n",
29175 what="load of library matching bar.so",catch-type="unload",times="0"@}
29180 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29181 @node GDB/MI Program Context
29182 @section @sc{gdb/mi} Program Context
29184 @subheading The @code{-exec-arguments} Command
29185 @findex -exec-arguments
29188 @subsubheading Synopsis
29191 -exec-arguments @var{args}
29194 Set the inferior program arguments, to be used in the next
29197 @subsubheading @value{GDBN} Command
29199 The corresponding @value{GDBN} command is @samp{set args}.
29201 @subsubheading Example
29205 -exec-arguments -v word
29212 @subheading The @code{-exec-show-arguments} Command
29213 @findex -exec-show-arguments
29215 @subsubheading Synopsis
29218 -exec-show-arguments
29221 Print the arguments of the program.
29223 @subsubheading @value{GDBN} Command
29225 The corresponding @value{GDBN} command is @samp{show args}.
29227 @subsubheading Example
29232 @subheading The @code{-environment-cd} Command
29233 @findex -environment-cd
29235 @subsubheading Synopsis
29238 -environment-cd @var{pathdir}
29241 Set @value{GDBN}'s working directory.
29243 @subsubheading @value{GDBN} Command
29245 The corresponding @value{GDBN} command is @samp{cd}.
29247 @subsubheading Example
29251 -environment-cd /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29257 @subheading The @code{-environment-directory} Command
29258 @findex -environment-directory
29260 @subsubheading Synopsis
29263 -environment-directory [ -r ] [ @var{pathdir} ]+
29266 Add directories @var{pathdir} to beginning of search path for source files.
29267 If the @samp{-r} option is used, the search path is reset to the default
29268 search path. If directories @var{pathdir} are supplied in addition to the
29269 @samp{-r} option, the search path is first reset and then addition
29271 Multiple directories may be specified, separated by blanks. Specifying
29272 multiple directories in a single command
29273 results in the directories added to the beginning of the
29274 search path in the same order they were presented in the command.
29275 If blanks are needed as
29276 part of a directory name, double-quotes should be used around
29277 the name. In the command output, the path will show up separated
29278 by the system directory-separator character. The directory-separator
29279 character must not be used
29280 in any directory name.
29281 If no directories are specified, the current search path is displayed.
29283 @subsubheading @value{GDBN} Command
29285 The corresponding @value{GDBN} command is @samp{dir}.
29287 @subsubheading Example
29291 -environment-directory /kwikemart/marge/ezannoni/flathead-dev/devo/gdb
29292 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29294 -environment-directory ""
29295 ^done,source-path="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb:$cdir:$cwd"
29297 -environment-directory -r /home/jjohnstn/src/gdb /usr/src
29298 ^done,source-path="/home/jjohnstn/src/gdb:/usr/src:$cdir:$cwd"
29300 -environment-directory -r
29301 ^done,source-path="$cdir:$cwd"
29306 @subheading The @code{-environment-path} Command
29307 @findex -environment-path
29309 @subsubheading Synopsis
29312 -environment-path [ -r ] [ @var{pathdir} ]+
29315 Add directories @var{pathdir} to beginning of search path for object files.
29316 If the @samp{-r} option is used, the search path is reset to the original
29317 search path that existed at gdb start-up. If directories @var{pathdir} are
29318 supplied in addition to the
29319 @samp{-r} option, the search path is first reset and then addition
29321 Multiple directories may be specified, separated by blanks. Specifying
29322 multiple directories in a single command
29323 results in the directories added to the beginning of the
29324 search path in the same order they were presented in the command.
29325 If blanks are needed as
29326 part of a directory name, double-quotes should be used around
29327 the name. In the command output, the path will show up separated
29328 by the system directory-separator character. The directory-separator
29329 character must not be used
29330 in any directory name.
29331 If no directories are specified, the current path is displayed.
29334 @subsubheading @value{GDBN} Command
29336 The corresponding @value{GDBN} command is @samp{path}.
29338 @subsubheading Example
29343 ^done,path="/usr/bin"
29345 -environment-path /kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb /bin
29346 ^done,path="/kwikemart/marge/ezannoni/flathead-dev/ppc-eabi/gdb:/bin:/usr/bin"
29348 -environment-path -r /usr/local/bin
29349 ^done,path="/usr/local/bin:/usr/bin"
29354 @subheading The @code{-environment-pwd} Command
29355 @findex -environment-pwd
29357 @subsubheading Synopsis
29363 Show the current working directory.
29365 @subsubheading @value{GDBN} Command
29367 The corresponding @value{GDBN} command is @samp{pwd}.
29369 @subsubheading Example
29374 ^done,cwd="/kwikemart/marge/ezannoni/flathead-dev/devo/gdb"
29378 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29379 @node GDB/MI Thread Commands
29380 @section @sc{gdb/mi} Thread Commands
29383 @subheading The @code{-thread-info} Command
29384 @findex -thread-info
29386 @subsubheading Synopsis
29389 -thread-info [ @var{thread-id} ]
29392 Reports information about either a specific thread, if
29393 the @var{thread-id} parameter is present, or about all
29394 threads. When printing information about all threads,
29395 also reports the current thread.
29397 @subsubheading @value{GDBN} Command
29399 The @samp{info thread} command prints the same information
29402 @subsubheading Result
29404 The result is a list of threads. The following attributes are
29405 defined for a given thread:
29409 This field exists only for the current thread. It has the value @samp{*}.
29412 The identifier that @value{GDBN} uses to refer to the thread.
29415 The identifier that the target uses to refer to the thread.
29418 Extra information about the thread, in a target-specific format. This
29422 The name of the thread. If the user specified a name using the
29423 @code{thread name} command, then this name is given. Otherwise, if
29424 @value{GDBN} can extract the thread name from the target, then that
29425 name is given. If @value{GDBN} cannot find the thread name, then this
29429 The stack frame currently executing in the thread.
29432 The thread's state. The @samp{state} field may have the following
29437 The thread is stopped. Frame information is available for stopped
29441 The thread is running. There's no frame information for running
29447 If @value{GDBN} can find the CPU core on which this thread is running,
29448 then this field is the core identifier. This field is optional.
29452 @subsubheading Example
29457 @{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
29458 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",
29459 args=[]@},state="running"@},
29460 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
29461 frame=@{level="0",addr="0x0804891f",func="foo",
29462 args=[@{name="i",value="10"@}],
29463 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},
29464 state="running"@}],
29465 current-thread-id="1"
29469 @subheading The @code{-thread-list-ids} Command
29470 @findex -thread-list-ids
29472 @subsubheading Synopsis
29478 Produces a list of the currently known @value{GDBN} thread ids. At the
29479 end of the list it also prints the total number of such threads.
29481 This command is retained for historical reasons, the
29482 @code{-thread-info} command should be used instead.
29484 @subsubheading @value{GDBN} Command
29486 Part of @samp{info threads} supplies the same information.
29488 @subsubheading Example
29493 ^done,thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29494 current-thread-id="1",number-of-threads="3"
29499 @subheading The @code{-thread-select} Command
29500 @findex -thread-select
29502 @subsubheading Synopsis
29505 -thread-select @var{threadnum}
29508 Make @var{threadnum} the current thread. It prints the number of the new
29509 current thread, and the topmost frame for that thread.
29511 This command is deprecated in favor of explicitly using the
29512 @samp{--thread} option to each command.
29514 @subsubheading @value{GDBN} Command
29516 The corresponding @value{GDBN} command is @samp{thread}.
29518 @subsubheading Example
29525 *stopped,reason="end-stepping-range",thread-id="2",line="187",
29526 file="../../../devo/gdb/testsuite/gdb.threads/linux-dp.c"
29530 thread-ids=@{thread-id="3",thread-id="2",thread-id="1"@},
29531 number-of-threads="3"
29534 ^done,new-thread-id="3",
29535 frame=@{level="0",func="vprintf",
29536 args=[@{name="format",value="0x8048e9c \"%*s%c %d %c\\n\""@},
29537 @{name="arg",value="0x2"@}],file="vprintf.c",line="31"@}
29541 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29542 @node GDB/MI Ada Tasking Commands
29543 @section @sc{gdb/mi} Ada Tasking Commands
29545 @subheading The @code{-ada-task-info} Command
29546 @findex -ada-task-info
29548 @subsubheading Synopsis
29551 -ada-task-info [ @var{task-id} ]
29554 Reports information about either a specific Ada task, if the
29555 @var{task-id} parameter is present, or about all Ada tasks.
29557 @subsubheading @value{GDBN} Command
29559 The @samp{info tasks} command prints the same information
29560 about all Ada tasks (@pxref{Ada Tasks}).
29562 @subsubheading Result
29564 The result is a table of Ada tasks. The following columns are
29565 defined for each Ada task:
29569 This field exists only for the current thread. It has the value @samp{*}.
29572 The identifier that @value{GDBN} uses to refer to the Ada task.
29575 The identifier that the target uses to refer to the Ada task.
29578 The identifier of the thread corresponding to the Ada task.
29580 This field should always exist, as Ada tasks are always implemented
29581 on top of a thread. But if @value{GDBN} cannot find this corresponding
29582 thread for any reason, the field is omitted.
29585 This field exists only when the task was created by another task.
29586 In this case, it provides the ID of the parent task.
29589 The base priority of the task.
29592 The current state of the task. For a detailed description of the
29593 possible states, see @ref{Ada Tasks}.
29596 The name of the task.
29600 @subsubheading Example
29604 ^done,tasks=@{nr_rows="3",nr_cols="8",
29605 hdr=[@{width="1",alignment="-1",col_name="current",colhdr=""@},
29606 @{width="3",alignment="1",col_name="id",colhdr="ID"@},
29607 @{width="9",alignment="1",col_name="task-id",colhdr="TID"@},
29608 @{width="4",alignment="1",col_name="thread-id",colhdr=""@},
29609 @{width="4",alignment="1",col_name="parent-id",colhdr="P-ID"@},
29610 @{width="3",alignment="1",col_name="priority",colhdr="Pri"@},
29611 @{width="22",alignment="-1",col_name="state",colhdr="State"@},
29612 @{width="1",alignment="2",col_name="name",colhdr="Name"@}],
29613 body=[@{current="*",id="1",task-id=" 644010",thread-id="1",priority="48",
29614 state="Child Termination Wait",name="main_task"@}]@}
29618 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
29619 @node GDB/MI Program Execution
29620 @section @sc{gdb/mi} Program Execution
29622 These are the asynchronous commands which generate the out-of-band
29623 record @samp{*stopped}. Currently @value{GDBN} only really executes
29624 asynchronously with remote targets and this interaction is mimicked in
29627 @subheading The @code{-exec-continue} Command
29628 @findex -exec-continue
29630 @subsubheading Synopsis
29633 -exec-continue [--reverse] [--all|--thread-group N]
29636 Resumes the execution of the inferior program, which will continue
29637 to execute until it reaches a debugger stop event. If the
29638 @samp{--reverse} option is specified, execution resumes in reverse until
29639 it reaches a stop event. Stop events may include
29642 breakpoints or watchpoints
29644 signals or exceptions
29646 the end of the process (or its beginning under @samp{--reverse})
29648 the end or beginning of a replay log if one is being used.
29650 In all-stop mode (@pxref{All-Stop
29651 Mode}), may resume only one thread, or all threads, depending on the
29652 value of the @samp{scheduler-locking} variable. If @samp{--all} is
29653 specified, all threads (in all inferiors) will be resumed. The @samp{--all} option is
29654 ignored in all-stop mode. If the @samp{--thread-group} options is
29655 specified, then all threads in that thread group are resumed.
29657 @subsubheading @value{GDBN} Command
29659 The corresponding @value{GDBN} corresponding is @samp{continue}.
29661 @subsubheading Example
29668 *stopped,reason="breakpoint-hit",disp="keep",bkptno="2",frame=@{
29669 func="foo",args=[],file="hello.c",fullname="/home/foo/bar/hello.c",
29675 @subheading The @code{-exec-finish} Command
29676 @findex -exec-finish
29678 @subsubheading Synopsis
29681 -exec-finish [--reverse]
29684 Resumes the execution of the inferior program until the current
29685 function is exited. Displays the results returned by the function.
29686 If the @samp{--reverse} option is specified, resumes the reverse
29687 execution of the inferior program until the point where current
29688 function was called.
29690 @subsubheading @value{GDBN} Command
29692 The corresponding @value{GDBN} command is @samp{finish}.
29694 @subsubheading Example
29696 Function returning @code{void}.
29703 *stopped,reason="function-finished",frame=@{func="main",args=[],
29704 file="hello.c",fullname="/home/foo/bar/hello.c",line="7"@}
29708 Function returning other than @code{void}. The name of the internal
29709 @value{GDBN} variable storing the result is printed, together with the
29716 *stopped,reason="function-finished",frame=@{addr="0x000107b0",func="foo",
29717 args=[@{name="a",value="1"],@{name="b",value="9"@}@},
29718 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
29719 gdb-result-var="$1",return-value="0"
29724 @subheading The @code{-exec-interrupt} Command
29725 @findex -exec-interrupt
29727 @subsubheading Synopsis
29730 -exec-interrupt [--all|--thread-group N]
29733 Interrupts the background execution of the target. Note how the token
29734 associated with the stop message is the one for the execution command
29735 that has been interrupted. The token for the interrupt itself only
29736 appears in the @samp{^done} output. If the user is trying to
29737 interrupt a non-running program, an error message will be printed.
29739 Note that when asynchronous execution is enabled, this command is
29740 asynchronous just like other execution commands. That is, first the
29741 @samp{^done} response will be printed, and the target stop will be
29742 reported after that using the @samp{*stopped} notification.
29744 In non-stop mode, only the context thread is interrupted by default.
29745 All threads (in all inferiors) will be interrupted if the
29746 @samp{--all} option is specified. If the @samp{--thread-group}
29747 option is specified, all threads in that group will be interrupted.
29749 @subsubheading @value{GDBN} Command
29751 The corresponding @value{GDBN} command is @samp{interrupt}.
29753 @subsubheading Example
29764 111*stopped,signal-name="SIGINT",signal-meaning="Interrupt",
29765 frame=@{addr="0x00010140",func="foo",args=[],file="try.c",
29766 fullname="/home/foo/bar/try.c",line="13"@}
29771 ^error,msg="mi_cmd_exec_interrupt: Inferior not executing."
29775 @subheading The @code{-exec-jump} Command
29778 @subsubheading Synopsis
29781 -exec-jump @var{location}
29784 Resumes execution of the inferior program at the location specified by
29785 parameter. @xref{Specify Location}, for a description of the
29786 different forms of @var{location}.
29788 @subsubheading @value{GDBN} Command
29790 The corresponding @value{GDBN} command is @samp{jump}.
29792 @subsubheading Example
29795 -exec-jump foo.c:10
29796 *running,thread-id="all"
29801 @subheading The @code{-exec-next} Command
29804 @subsubheading Synopsis
29807 -exec-next [--reverse]
29810 Resumes execution of the inferior program, stopping when the beginning
29811 of the next source line is reached.
29813 If the @samp{--reverse} option is specified, resumes reverse execution
29814 of the inferior program, stopping at the beginning of the previous
29815 source line. If you issue this command on the first line of a
29816 function, it will take you back to the caller of that function, to the
29817 source line where the function was called.
29820 @subsubheading @value{GDBN} Command
29822 The corresponding @value{GDBN} command is @samp{next}.
29824 @subsubheading Example
29830 *stopped,reason="end-stepping-range",line="8",file="hello.c"
29835 @subheading The @code{-exec-next-instruction} Command
29836 @findex -exec-next-instruction
29838 @subsubheading Synopsis
29841 -exec-next-instruction [--reverse]
29844 Executes one machine instruction. If the instruction is a function
29845 call, continues until the function returns. If the program stops at an
29846 instruction in the middle of a source line, the address will be
29849 If the @samp{--reverse} option is specified, resumes reverse execution
29850 of the inferior program, stopping at the previous instruction. If the
29851 previously executed instruction was a return from another function,
29852 it will continue to execute in reverse until the call to that function
29853 (from the current stack frame) is reached.
29855 @subsubheading @value{GDBN} Command
29857 The corresponding @value{GDBN} command is @samp{nexti}.
29859 @subsubheading Example
29863 -exec-next-instruction
29867 *stopped,reason="end-stepping-range",
29868 addr="0x000100d4",line="5",file="hello.c"
29873 @subheading The @code{-exec-return} Command
29874 @findex -exec-return
29876 @subsubheading Synopsis
29882 Makes current function return immediately. Doesn't execute the inferior.
29883 Displays the new current frame.
29885 @subsubheading @value{GDBN} Command
29887 The corresponding @value{GDBN} command is @samp{return}.
29889 @subsubheading Example
29893 200-break-insert callee4
29894 200^done,bkpt=@{number="1",addr="0x00010734",
29895 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29900 000*stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29901 frame=@{func="callee4",args=[],
29902 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29903 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@}
29909 111^done,frame=@{level="0",func="callee3",
29910 args=[@{name="strarg",
29911 value="0x11940 \"A string argument.\""@}],
29912 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
29913 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="18"@}
29918 @subheading The @code{-exec-run} Command
29921 @subsubheading Synopsis
29924 -exec-run [--all | --thread-group N]
29927 Starts execution of the inferior from the beginning. The inferior
29928 executes until either a breakpoint is encountered or the program
29929 exits. In the latter case the output will include an exit code, if
29930 the program has exited exceptionally.
29932 When no option is specified, the current inferior is started. If the
29933 @samp{--thread-group} option is specified, it should refer to a thread
29934 group of type @samp{process}, and that thread group will be started.
29935 If the @samp{--all} option is specified, then all inferiors will be started.
29937 @subsubheading @value{GDBN} Command
29939 The corresponding @value{GDBN} command is @samp{run}.
29941 @subsubheading Examples
29946 ^done,bkpt=@{number="1",addr="0x0001072c",file="recursive2.c",line="4"@}
29951 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",
29952 frame=@{func="main",args=[],file="recursive2.c",
29953 fullname="/home/foo/bar/recursive2.c",line="4"@}
29958 Program exited normally:
29966 *stopped,reason="exited-normally"
29971 Program exited exceptionally:
29979 *stopped,reason="exited",exit-code="01"
29983 Another way the program can terminate is if it receives a signal such as
29984 @code{SIGINT}. In this case, @sc{gdb/mi} displays this:
29988 *stopped,reason="exited-signalled",signal-name="SIGINT",
29989 signal-meaning="Interrupt"
29993 @c @subheading -exec-signal
29996 @subheading The @code{-exec-step} Command
29999 @subsubheading Synopsis
30002 -exec-step [--reverse]
30005 Resumes execution of the inferior program, stopping when the beginning
30006 of the next source line is reached, if the next source line is not a
30007 function call. If it is, stop at the first instruction of the called
30008 function. If the @samp{--reverse} option is specified, resumes reverse
30009 execution of the inferior program, stopping at the beginning of the
30010 previously executed source line.
30012 @subsubheading @value{GDBN} Command
30014 The corresponding @value{GDBN} command is @samp{step}.
30016 @subsubheading Example
30018 Stepping into a function:
30024 *stopped,reason="end-stepping-range",
30025 frame=@{func="foo",args=[@{name="a",value="10"@},
30026 @{name="b",value="0"@}],file="recursive2.c",
30027 fullname="/home/foo/bar/recursive2.c",line="11"@}
30037 *stopped,reason="end-stepping-range",line="14",file="recursive2.c"
30042 @subheading The @code{-exec-step-instruction} Command
30043 @findex -exec-step-instruction
30045 @subsubheading Synopsis
30048 -exec-step-instruction [--reverse]
30051 Resumes the inferior which executes one machine instruction. If the
30052 @samp{--reverse} option is specified, resumes reverse execution of the
30053 inferior program, stopping at the previously executed instruction.
30054 The output, once @value{GDBN} has stopped, will vary depending on
30055 whether we have stopped in the middle of a source line or not. In the
30056 former case, the address at which the program stopped will be printed
30059 @subsubheading @value{GDBN} Command
30061 The corresponding @value{GDBN} command is @samp{stepi}.
30063 @subsubheading Example
30067 -exec-step-instruction
30071 *stopped,reason="end-stepping-range",
30072 frame=@{func="foo",args=[],file="try.c",
30073 fullname="/home/foo/bar/try.c",line="10"@}
30075 -exec-step-instruction
30079 *stopped,reason="end-stepping-range",
30080 frame=@{addr="0x000100f4",func="foo",args=[],file="try.c",
30081 fullname="/home/foo/bar/try.c",line="10"@}
30086 @subheading The @code{-exec-until} Command
30087 @findex -exec-until
30089 @subsubheading Synopsis
30092 -exec-until [ @var{location} ]
30095 Executes the inferior until the @var{location} specified in the
30096 argument is reached. If there is no argument, the inferior executes
30097 until a source line greater than the current one is reached. The
30098 reason for stopping in this case will be @samp{location-reached}.
30100 @subsubheading @value{GDBN} Command
30102 The corresponding @value{GDBN} command is @samp{until}.
30104 @subsubheading Example
30108 -exec-until recursive2.c:6
30112 *stopped,reason="location-reached",frame=@{func="main",args=[],
30113 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="6"@}
30118 @subheading -file-clear
30119 Is this going away????
30122 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30123 @node GDB/MI Stack Manipulation
30124 @section @sc{gdb/mi} Stack Manipulation Commands
30127 @subheading The @code{-stack-info-frame} Command
30128 @findex -stack-info-frame
30130 @subsubheading Synopsis
30136 Get info on the selected frame.
30138 @subsubheading @value{GDBN} Command
30140 The corresponding @value{GDBN} command is @samp{info frame} or @samp{frame}
30141 (without arguments).
30143 @subsubheading Example
30148 ^done,frame=@{level="1",addr="0x0001076c",func="callee3",
30149 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30150 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@}
30154 @subheading The @code{-stack-info-depth} Command
30155 @findex -stack-info-depth
30157 @subsubheading Synopsis
30160 -stack-info-depth [ @var{max-depth} ]
30163 Return the depth of the stack. If the integer argument @var{max-depth}
30164 is specified, do not count beyond @var{max-depth} frames.
30166 @subsubheading @value{GDBN} Command
30168 There's no equivalent @value{GDBN} command.
30170 @subsubheading Example
30172 For a stack with frame levels 0 through 11:
30179 -stack-info-depth 4
30182 -stack-info-depth 12
30185 -stack-info-depth 11
30188 -stack-info-depth 13
30193 @subheading The @code{-stack-list-arguments} Command
30194 @findex -stack-list-arguments
30196 @subsubheading Synopsis
30199 -stack-list-arguments @var{print-values}
30200 [ @var{low-frame} @var{high-frame} ]
30203 Display a list of the arguments for the frames between @var{low-frame}
30204 and @var{high-frame} (inclusive). If @var{low-frame} and
30205 @var{high-frame} are not provided, list the arguments for the whole
30206 call stack. If the two arguments are equal, show the single frame
30207 at the corresponding level. It is an error if @var{low-frame} is
30208 larger than the actual number of frames. On the other hand,
30209 @var{high-frame} may be larger than the actual number of frames, in
30210 which case only existing frames will be returned.
30212 If @var{print-values} is 0 or @code{--no-values}, print only the names of
30213 the variables; if it is 1 or @code{--all-values}, print also their
30214 values; and if it is 2 or @code{--simple-values}, print the name,
30215 type and value for simple data types, and the name and type for arrays,
30216 structures and unions.
30218 Use of this command to obtain arguments in a single frame is
30219 deprecated in favor of the @samp{-stack-list-variables} command.
30221 @subsubheading @value{GDBN} Command
30223 @value{GDBN} does not have an equivalent command. @code{gdbtk} has a
30224 @samp{gdb_get_args} command which partially overlaps with the
30225 functionality of @samp{-stack-list-arguments}.
30227 @subsubheading Example
30234 frame=@{level="0",addr="0x00010734",func="callee4",
30235 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30236 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="8"@},
30237 frame=@{level="1",addr="0x0001076c",func="callee3",
30238 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30239 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="17"@},
30240 frame=@{level="2",addr="0x0001078c",func="callee2",
30241 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30242 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="22"@},
30243 frame=@{level="3",addr="0x000107b4",func="callee1",
30244 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30245 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="27"@},
30246 frame=@{level="4",addr="0x000107e0",func="main",
30247 file="../../../devo/gdb/testsuite/gdb.mi/basics.c",
30248 fullname="/home/foo/bar/devo/gdb/testsuite/gdb.mi/basics.c",line="32"@}]
30250 -stack-list-arguments 0
30253 frame=@{level="0",args=[]@},
30254 frame=@{level="1",args=[name="strarg"]@},
30255 frame=@{level="2",args=[name="intarg",name="strarg"]@},
30256 frame=@{level="3",args=[name="intarg",name="strarg",name="fltarg"]@},
30257 frame=@{level="4",args=[]@}]
30259 -stack-list-arguments 1
30262 frame=@{level="0",args=[]@},
30264 args=[@{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30265 frame=@{level="2",args=[
30266 @{name="intarg",value="2"@},
30267 @{name="strarg",value="0x11940 \"A string argument.\""@}]@},
30268 @{frame=@{level="3",args=[
30269 @{name="intarg",value="2"@},
30270 @{name="strarg",value="0x11940 \"A string argument.\""@},
30271 @{name="fltarg",value="3.5"@}]@},
30272 frame=@{level="4",args=[]@}]
30274 -stack-list-arguments 0 2 2
30275 ^done,stack-args=[frame=@{level="2",args=[name="intarg",name="strarg"]@}]
30277 -stack-list-arguments 1 2 2
30278 ^done,stack-args=[frame=@{level="2",
30279 args=[@{name="intarg",value="2"@},
30280 @{name="strarg",value="0x11940 \"A string argument.\""@}]@}]
30284 @c @subheading -stack-list-exception-handlers
30287 @subheading The @code{-stack-list-frames} Command
30288 @findex -stack-list-frames
30290 @subsubheading Synopsis
30293 -stack-list-frames [ @var{low-frame} @var{high-frame} ]
30296 List the frames currently on the stack. For each frame it displays the
30301 The frame number, 0 being the topmost frame, i.e., the innermost function.
30303 The @code{$pc} value for that frame.
30307 File name of the source file where the function lives.
30308 @item @var{fullname}
30309 The full file name of the source file where the function lives.
30311 Line number corresponding to the @code{$pc}.
30313 The shared library where this function is defined. This is only given
30314 if the frame's function is not known.
30317 If invoked without arguments, this command prints a backtrace for the
30318 whole stack. If given two integer arguments, it shows the frames whose
30319 levels are between the two arguments (inclusive). If the two arguments
30320 are equal, it shows the single frame at the corresponding level. It is
30321 an error if @var{low-frame} is larger than the actual number of
30322 frames. On the other hand, @var{high-frame} may be larger than the
30323 actual number of frames, in which case only existing frames will be returned.
30325 @subsubheading @value{GDBN} Command
30327 The corresponding @value{GDBN} commands are @samp{backtrace} and @samp{where}.
30329 @subsubheading Example
30331 Full stack backtrace:
30337 [frame=@{level="0",addr="0x0001076c",func="foo",
30338 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="11"@},
30339 frame=@{level="1",addr="0x000107a4",func="foo",
30340 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30341 frame=@{level="2",addr="0x000107a4",func="foo",
30342 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30343 frame=@{level="3",addr="0x000107a4",func="foo",
30344 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30345 frame=@{level="4",addr="0x000107a4",func="foo",
30346 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30347 frame=@{level="5",addr="0x000107a4",func="foo",
30348 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30349 frame=@{level="6",addr="0x000107a4",func="foo",
30350 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30351 frame=@{level="7",addr="0x000107a4",func="foo",
30352 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30353 frame=@{level="8",addr="0x000107a4",func="foo",
30354 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30355 frame=@{level="9",addr="0x000107a4",func="foo",
30356 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30357 frame=@{level="10",addr="0x000107a4",func="foo",
30358 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30359 frame=@{level="11",addr="0x00010738",func="main",
30360 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="4"@}]
30364 Show frames between @var{low_frame} and @var{high_frame}:
30368 -stack-list-frames 3 5
30370 [frame=@{level="3",addr="0x000107a4",func="foo",
30371 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30372 frame=@{level="4",addr="0x000107a4",func="foo",
30373 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@},
30374 frame=@{level="5",addr="0x000107a4",func="foo",
30375 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30379 Show a single frame:
30383 -stack-list-frames 3 3
30385 [frame=@{level="3",addr="0x000107a4",func="foo",
30386 file="recursive2.c",fullname="/home/foo/bar/recursive2.c",line="14"@}]
30391 @subheading The @code{-stack-list-locals} Command
30392 @findex -stack-list-locals
30394 @subsubheading Synopsis
30397 -stack-list-locals @var{print-values}
30400 Display the local variable names for the selected frame. If
30401 @var{print-values} is 0 or @code{--no-values}, print only the names of
30402 the variables; if it is 1 or @code{--all-values}, print also their
30403 values; and if it is 2 or @code{--simple-values}, print the name,
30404 type and value for simple data types, and the name and type for arrays,
30405 structures and unions. In this last case, a frontend can immediately
30406 display the value of simple data types and create variable objects for
30407 other data types when the user wishes to explore their values in
30410 This command is deprecated in favor of the
30411 @samp{-stack-list-variables} command.
30413 @subsubheading @value{GDBN} Command
30415 @samp{info locals} in @value{GDBN}, @samp{gdb_get_locals} in @code{gdbtk}.
30417 @subsubheading Example
30421 -stack-list-locals 0
30422 ^done,locals=[name="A",name="B",name="C"]
30424 -stack-list-locals --all-values
30425 ^done,locals=[@{name="A",value="1"@},@{name="B",value="2"@},
30426 @{name="C",value="@{1, 2, 3@}"@}]
30427 -stack-list-locals --simple-values
30428 ^done,locals=[@{name="A",type="int",value="1"@},
30429 @{name="B",type="int",value="2"@},@{name="C",type="int [3]"@}]
30433 @subheading The @code{-stack-list-variables} Command
30434 @findex -stack-list-variables
30436 @subsubheading Synopsis
30439 -stack-list-variables @var{print-values}
30442 Display the names of local variables and function arguments for the selected frame. If
30443 @var{print-values} is 0 or @code{--no-values}, print only the names of
30444 the variables; if it is 1 or @code{--all-values}, print also their
30445 values; and if it is 2 or @code{--simple-values}, print the name,
30446 type and value for simple data types, and the name and type for arrays,
30447 structures and unions.
30449 @subsubheading Example
30453 -stack-list-variables --thread 1 --frame 0 --all-values
30454 ^done,variables=[@{name="x",value="11"@},@{name="s",value="@{a = 1, b = 2@}"@}]
30459 @subheading The @code{-stack-select-frame} Command
30460 @findex -stack-select-frame
30462 @subsubheading Synopsis
30465 -stack-select-frame @var{framenum}
30468 Change the selected frame. Select a different frame @var{framenum} on
30471 This command in deprecated in favor of passing the @samp{--frame}
30472 option to every command.
30474 @subsubheading @value{GDBN} Command
30476 The corresponding @value{GDBN} commands are @samp{frame}, @samp{up},
30477 @samp{down}, @samp{select-frame}, @samp{up-silent}, and @samp{down-silent}.
30479 @subsubheading Example
30483 -stack-select-frame 2
30488 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
30489 @node GDB/MI Variable Objects
30490 @section @sc{gdb/mi} Variable Objects
30494 @subheading Motivation for Variable Objects in @sc{gdb/mi}
30496 For the implementation of a variable debugger window (locals, watched
30497 expressions, etc.), we are proposing the adaptation of the existing code
30498 used by @code{Insight}.
30500 The two main reasons for that are:
30504 It has been proven in practice (it is already on its second generation).
30507 It will shorten development time (needless to say how important it is
30511 The original interface was designed to be used by Tcl code, so it was
30512 slightly changed so it could be used through @sc{gdb/mi}. This section
30513 describes the @sc{gdb/mi} operations that will be available and gives some
30514 hints about their use.
30516 @emph{Note}: In addition to the set of operations described here, we
30517 expect the @sc{gui} implementation of a variable window to require, at
30518 least, the following operations:
30521 @item @code{-gdb-show} @code{output-radix}
30522 @item @code{-stack-list-arguments}
30523 @item @code{-stack-list-locals}
30524 @item @code{-stack-select-frame}
30529 @subheading Introduction to Variable Objects
30531 @cindex variable objects in @sc{gdb/mi}
30533 Variable objects are "object-oriented" MI interface for examining and
30534 changing values of expressions. Unlike some other MI interfaces that
30535 work with expressions, variable objects are specifically designed for
30536 simple and efficient presentation in the frontend. A variable object
30537 is identified by string name. When a variable object is created, the
30538 frontend specifies the expression for that variable object. The
30539 expression can be a simple variable, or it can be an arbitrary complex
30540 expression, and can even involve CPU registers. After creating a
30541 variable object, the frontend can invoke other variable object
30542 operations---for example to obtain or change the value of a variable
30543 object, or to change display format.
30545 Variable objects have hierarchical tree structure. Any variable object
30546 that corresponds to a composite type, such as structure in C, has
30547 a number of child variable objects, for example corresponding to each
30548 element of a structure. A child variable object can itself have
30549 children, recursively. Recursion ends when we reach
30550 leaf variable objects, which always have built-in types. Child variable
30551 objects are created only by explicit request, so if a frontend
30552 is not interested in the children of a particular variable object, no
30553 child will be created.
30555 For a leaf variable object it is possible to obtain its value as a
30556 string, or set the value from a string. String value can be also
30557 obtained for a non-leaf variable object, but it's generally a string
30558 that only indicates the type of the object, and does not list its
30559 contents. Assignment to a non-leaf variable object is not allowed.
30561 A frontend does not need to read the values of all variable objects each time
30562 the program stops. Instead, MI provides an update command that lists all
30563 variable objects whose values has changed since the last update
30564 operation. This considerably reduces the amount of data that must
30565 be transferred to the frontend. As noted above, children variable
30566 objects are created on demand, and only leaf variable objects have a
30567 real value. As result, gdb will read target memory only for leaf
30568 variables that frontend has created.
30570 The automatic update is not always desirable. For example, a frontend
30571 might want to keep a value of some expression for future reference,
30572 and never update it. For another example, fetching memory is
30573 relatively slow for embedded targets, so a frontend might want
30574 to disable automatic update for the variables that are either not
30575 visible on the screen, or ``closed''. This is possible using so
30576 called ``frozen variable objects''. Such variable objects are never
30577 implicitly updated.
30579 Variable objects can be either @dfn{fixed} or @dfn{floating}. For the
30580 fixed variable object, the expression is parsed when the variable
30581 object is created, including associating identifiers to specific
30582 variables. The meaning of expression never changes. For a floating
30583 variable object the values of variables whose names appear in the
30584 expressions are re-evaluated every time in the context of the current
30585 frame. Consider this example:
30590 struct work_state state;
30597 If a fixed variable object for the @code{state} variable is created in
30598 this function, and we enter the recursive call, the variable
30599 object will report the value of @code{state} in the top-level
30600 @code{do_work} invocation. On the other hand, a floating variable
30601 object will report the value of @code{state} in the current frame.
30603 If an expression specified when creating a fixed variable object
30604 refers to a local variable, the variable object becomes bound to the
30605 thread and frame in which the variable object is created. When such
30606 variable object is updated, @value{GDBN} makes sure that the
30607 thread/frame combination the variable object is bound to still exists,
30608 and re-evaluates the variable object in context of that thread/frame.
30610 The following is the complete set of @sc{gdb/mi} operations defined to
30611 access this functionality:
30613 @multitable @columnfractions .4 .6
30614 @item @strong{Operation}
30615 @tab @strong{Description}
30617 @item @code{-enable-pretty-printing}
30618 @tab enable Python-based pretty-printing
30619 @item @code{-var-create}
30620 @tab create a variable object
30621 @item @code{-var-delete}
30622 @tab delete the variable object and/or its children
30623 @item @code{-var-set-format}
30624 @tab set the display format of this variable
30625 @item @code{-var-show-format}
30626 @tab show the display format of this variable
30627 @item @code{-var-info-num-children}
30628 @tab tells how many children this object has
30629 @item @code{-var-list-children}
30630 @tab return a list of the object's children
30631 @item @code{-var-info-type}
30632 @tab show the type of this variable object
30633 @item @code{-var-info-expression}
30634 @tab print parent-relative expression that this variable object represents
30635 @item @code{-var-info-path-expression}
30636 @tab print full expression that this variable object represents
30637 @item @code{-var-show-attributes}
30638 @tab is this variable editable? does it exist here?
30639 @item @code{-var-evaluate-expression}
30640 @tab get the value of this variable
30641 @item @code{-var-assign}
30642 @tab set the value of this variable
30643 @item @code{-var-update}
30644 @tab update the variable and its children
30645 @item @code{-var-set-frozen}
30646 @tab set frozeness attribute
30647 @item @code{-var-set-update-range}
30648 @tab set range of children to display on update
30651 In the next subsection we describe each operation in detail and suggest
30652 how it can be used.
30654 @subheading Description And Use of Operations on Variable Objects
30656 @subheading The @code{-enable-pretty-printing} Command
30657 @findex -enable-pretty-printing
30660 -enable-pretty-printing
30663 @value{GDBN} allows Python-based visualizers to affect the output of the
30664 MI variable object commands. However, because there was no way to
30665 implement this in a fully backward-compatible way, a front end must
30666 request that this functionality be enabled.
30668 Once enabled, this feature cannot be disabled.
30670 Note that if Python support has not been compiled into @value{GDBN},
30671 this command will still succeed (and do nothing).
30673 This feature is currently (as of @value{GDBN} 7.0) experimental, and
30674 may work differently in future versions of @value{GDBN}.
30676 @subheading The @code{-var-create} Command
30677 @findex -var-create
30679 @subsubheading Synopsis
30682 -var-create @{@var{name} | "-"@}
30683 @{@var{frame-addr} | "*" | "@@"@} @var{expression}
30686 This operation creates a variable object, which allows the monitoring of
30687 a variable, the result of an expression, a memory cell or a CPU
30690 The @var{name} parameter is the string by which the object can be
30691 referenced. It must be unique. If @samp{-} is specified, the varobj
30692 system will generate a string ``varNNNNNN'' automatically. It will be
30693 unique provided that one does not specify @var{name} of that format.
30694 The command fails if a duplicate name is found.
30696 The frame under which the expression should be evaluated can be
30697 specified by @var{frame-addr}. A @samp{*} indicates that the current
30698 frame should be used. A @samp{@@} indicates that a floating variable
30699 object must be created.
30701 @var{expression} is any expression valid on the current language set (must not
30702 begin with a @samp{*}), or one of the following:
30706 @samp{*@var{addr}}, where @var{addr} is the address of a memory cell
30709 @samp{*@var{addr}-@var{addr}} --- a memory address range (TBD)
30712 @samp{$@var{regname}} --- a CPU register name
30715 @cindex dynamic varobj
30716 A varobj's contents may be provided by a Python-based pretty-printer. In this
30717 case the varobj is known as a @dfn{dynamic varobj}. Dynamic varobjs
30718 have slightly different semantics in some cases. If the
30719 @code{-enable-pretty-printing} command is not sent, then @value{GDBN}
30720 will never create a dynamic varobj. This ensures backward
30721 compatibility for existing clients.
30723 @subsubheading Result
30725 This operation returns attributes of the newly-created varobj. These
30730 The name of the varobj.
30733 The number of children of the varobj. This number is not necessarily
30734 reliable for a dynamic varobj. Instead, you must examine the
30735 @samp{has_more} attribute.
30738 The varobj's scalar value. For a varobj whose type is some sort of
30739 aggregate (e.g., a @code{struct}), or for a dynamic varobj, this value
30740 will not be interesting.
30743 The varobj's type. This is a string representation of the type, as
30744 would be printed by the @value{GDBN} CLI. If @samp{print object}
30745 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30746 @emph{actual} (derived) type of the object is shown rather than the
30747 @emph{declared} one.
30750 If a variable object is bound to a specific thread, then this is the
30751 thread's identifier.
30754 For a dynamic varobj, this indicates whether there appear to be any
30755 children available. For a non-dynamic varobj, this will be 0.
30758 This attribute will be present and have the value @samp{1} if the
30759 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
30760 then this attribute will not be present.
30763 A dynamic varobj can supply a display hint to the front end. The
30764 value comes directly from the Python pretty-printer object's
30765 @code{display_hint} method. @xref{Pretty Printing API}.
30768 Typical output will look like this:
30771 name="@var{name}",numchild="@var{N}",type="@var{type}",thread-id="@var{M}",
30772 has_more="@var{has_more}"
30776 @subheading The @code{-var-delete} Command
30777 @findex -var-delete
30779 @subsubheading Synopsis
30782 -var-delete [ -c ] @var{name}
30785 Deletes a previously created variable object and all of its children.
30786 With the @samp{-c} option, just deletes the children.
30788 Returns an error if the object @var{name} is not found.
30791 @subheading The @code{-var-set-format} Command
30792 @findex -var-set-format
30794 @subsubheading Synopsis
30797 -var-set-format @var{name} @var{format-spec}
30800 Sets the output format for the value of the object @var{name} to be
30803 @anchor{-var-set-format}
30804 The syntax for the @var{format-spec} is as follows:
30807 @var{format-spec} @expansion{}
30808 @{binary | decimal | hexadecimal | octal | natural@}
30811 The natural format is the default format choosen automatically
30812 based on the variable type (like decimal for an @code{int}, hex
30813 for pointers, etc.).
30815 For a variable with children, the format is set only on the
30816 variable itself, and the children are not affected.
30818 @subheading The @code{-var-show-format} Command
30819 @findex -var-show-format
30821 @subsubheading Synopsis
30824 -var-show-format @var{name}
30827 Returns the format used to display the value of the object @var{name}.
30830 @var{format} @expansion{}
30835 @subheading The @code{-var-info-num-children} Command
30836 @findex -var-info-num-children
30838 @subsubheading Synopsis
30841 -var-info-num-children @var{name}
30844 Returns the number of children of a variable object @var{name}:
30850 Note that this number is not completely reliable for a dynamic varobj.
30851 It will return the current number of children, but more children may
30855 @subheading The @code{-var-list-children} Command
30856 @findex -var-list-children
30858 @subsubheading Synopsis
30861 -var-list-children [@var{print-values}] @var{name} [@var{from} @var{to}]
30863 @anchor{-var-list-children}
30865 Return a list of the children of the specified variable object and
30866 create variable objects for them, if they do not already exist. With
30867 a single argument or if @var{print-values} has a value of 0 or
30868 @code{--no-values}, print only the names of the variables; if
30869 @var{print-values} is 1 or @code{--all-values}, also print their
30870 values; and if it is 2 or @code{--simple-values} print the name and
30871 value for simple data types and just the name for arrays, structures
30874 @var{from} and @var{to}, if specified, indicate the range of children
30875 to report. If @var{from} or @var{to} is less than zero, the range is
30876 reset and all children will be reported. Otherwise, children starting
30877 at @var{from} (zero-based) and up to and excluding @var{to} will be
30880 If a child range is requested, it will only affect the current call to
30881 @code{-var-list-children}, but not future calls to @code{-var-update}.
30882 For this, you must instead use @code{-var-set-update-range}. The
30883 intent of this approach is to enable a front end to implement any
30884 update approach it likes; for example, scrolling a view may cause the
30885 front end to request more children with @code{-var-list-children}, and
30886 then the front end could call @code{-var-set-update-range} with a
30887 different range to ensure that future updates are restricted to just
30890 For each child the following results are returned:
30895 Name of the variable object created for this child.
30898 The expression to be shown to the user by the front end to designate this child.
30899 For example this may be the name of a structure member.
30901 For a dynamic varobj, this value cannot be used to form an
30902 expression. There is no way to do this at all with a dynamic varobj.
30904 For C/C@t{++} structures there are several pseudo children returned to
30905 designate access qualifiers. For these pseudo children @var{exp} is
30906 @samp{public}, @samp{private}, or @samp{protected}. In this case the
30907 type and value are not present.
30909 A dynamic varobj will not report the access qualifying
30910 pseudo-children, regardless of the language. This information is not
30911 available at all with a dynamic varobj.
30914 Number of children this child has. For a dynamic varobj, this will be
30918 The type of the child. If @samp{print object}
30919 (@pxref{Print Settings, set print object}) is set to @code{on}, the
30920 @emph{actual} (derived) type of the object is shown rather than the
30921 @emph{declared} one.
30924 If values were requested, this is the value.
30927 If this variable object is associated with a thread, this is the thread id.
30928 Otherwise this result is not present.
30931 If the variable object is frozen, this variable will be present with a value of 1.
30934 The result may have its own attributes:
30938 A dynamic varobj can supply a display hint to the front end. The
30939 value comes directly from the Python pretty-printer object's
30940 @code{display_hint} method. @xref{Pretty Printing API}.
30943 This is an integer attribute which is nonzero if there are children
30944 remaining after the end of the selected range.
30947 @subsubheading Example
30951 -var-list-children n
30952 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30953 numchild=@var{n},type=@var{type}@},@r{(repeats N times)}]
30955 -var-list-children --all-values n
30956 ^done,numchild=@var{n},children=[child=@{name=@var{name},exp=@var{exp},
30957 numchild=@var{n},value=@var{value},type=@var{type}@},@r{(repeats N times)}]
30961 @subheading The @code{-var-info-type} Command
30962 @findex -var-info-type
30964 @subsubheading Synopsis
30967 -var-info-type @var{name}
30970 Returns the type of the specified variable @var{name}. The type is
30971 returned as a string in the same format as it is output by the
30975 type=@var{typename}
30979 @subheading The @code{-var-info-expression} Command
30980 @findex -var-info-expression
30982 @subsubheading Synopsis
30985 -var-info-expression @var{name}
30988 Returns a string that is suitable for presenting this
30989 variable object in user interface. The string is generally
30990 not valid expression in the current language, and cannot be evaluated.
30992 For example, if @code{a} is an array, and variable object
30993 @code{A} was created for @code{a}, then we'll get this output:
30996 (gdb) -var-info-expression A.1
30997 ^done,lang="C",exp="1"
31001 Here, the values of @code{lang} can be @code{@{"C" | "C++" | "Java"@}}.
31003 Note that the output of the @code{-var-list-children} command also
31004 includes those expressions, so the @code{-var-info-expression} command
31007 @subheading The @code{-var-info-path-expression} Command
31008 @findex -var-info-path-expression
31010 @subsubheading Synopsis
31013 -var-info-path-expression @var{name}
31016 Returns an expression that can be evaluated in the current
31017 context and will yield the same value that a variable object has.
31018 Compare this with the @code{-var-info-expression} command, which
31019 result can be used only for UI presentation. Typical use of
31020 the @code{-var-info-path-expression} command is creating a
31021 watchpoint from a variable object.
31023 This command is currently not valid for children of a dynamic varobj,
31024 and will give an error when invoked on one.
31026 For example, suppose @code{C} is a C@t{++} class, derived from class
31027 @code{Base}, and that the @code{Base} class has a member called
31028 @code{m_size}. Assume a variable @code{c} is has the type of
31029 @code{C} and a variable object @code{C} was created for variable
31030 @code{c}. Then, we'll get this output:
31032 (gdb) -var-info-path-expression C.Base.public.m_size
31033 ^done,path_expr=((Base)c).m_size)
31036 @subheading The @code{-var-show-attributes} Command
31037 @findex -var-show-attributes
31039 @subsubheading Synopsis
31042 -var-show-attributes @var{name}
31045 List attributes of the specified variable object @var{name}:
31048 status=@var{attr} [ ( ,@var{attr} )* ]
31052 where @var{attr} is @code{@{ @{ editable | noneditable @} | TBD @}}.
31054 @subheading The @code{-var-evaluate-expression} Command
31055 @findex -var-evaluate-expression
31057 @subsubheading Synopsis
31060 -var-evaluate-expression [-f @var{format-spec}] @var{name}
31063 Evaluates the expression that is represented by the specified variable
31064 object and returns its value as a string. The format of the string
31065 can be specified with the @samp{-f} option. The possible values of
31066 this option are the same as for @code{-var-set-format}
31067 (@pxref{-var-set-format}). If the @samp{-f} option is not specified,
31068 the current display format will be used. The current display format
31069 can be changed using the @code{-var-set-format} command.
31075 Note that one must invoke @code{-var-list-children} for a variable
31076 before the value of a child variable can be evaluated.
31078 @subheading The @code{-var-assign} Command
31079 @findex -var-assign
31081 @subsubheading Synopsis
31084 -var-assign @var{name} @var{expression}
31087 Assigns the value of @var{expression} to the variable object specified
31088 by @var{name}. The object must be @samp{editable}. If the variable's
31089 value is altered by the assign, the variable will show up in any
31090 subsequent @code{-var-update} list.
31092 @subsubheading Example
31100 ^done,changelist=[@{name="var1",in_scope="true",type_changed="false"@}]
31104 @subheading The @code{-var-update} Command
31105 @findex -var-update
31107 @subsubheading Synopsis
31110 -var-update [@var{print-values}] @{@var{name} | "*"@}
31113 Reevaluate the expressions corresponding to the variable object
31114 @var{name} and all its direct and indirect children, and return the
31115 list of variable objects whose values have changed; @var{name} must
31116 be a root variable object. Here, ``changed'' means that the result of
31117 @code{-var-evaluate-expression} before and after the
31118 @code{-var-update} is different. If @samp{*} is used as the variable
31119 object names, all existing variable objects are updated, except
31120 for frozen ones (@pxref{-var-set-frozen}). The option
31121 @var{print-values} determines whether both names and values, or just
31122 names are printed. The possible values of this option are the same
31123 as for @code{-var-list-children} (@pxref{-var-list-children}). It is
31124 recommended to use the @samp{--all-values} option, to reduce the
31125 number of MI commands needed on each program stop.
31127 With the @samp{*} parameter, if a variable object is bound to a
31128 currently running thread, it will not be updated, without any
31131 If @code{-var-set-update-range} was previously used on a varobj, then
31132 only the selected range of children will be reported.
31134 @code{-var-update} reports all the changed varobjs in a tuple named
31137 Each item in the change list is itself a tuple holding:
31141 The name of the varobj.
31144 If values were requested for this update, then this field will be
31145 present and will hold the value of the varobj.
31148 @anchor{-var-update}
31149 This field is a string which may take one of three values:
31153 The variable object's current value is valid.
31156 The variable object does not currently hold a valid value but it may
31157 hold one in the future if its associated expression comes back into
31161 The variable object no longer holds a valid value.
31162 This can occur when the executable file being debugged has changed,
31163 either through recompilation or by using the @value{GDBN} @code{file}
31164 command. The front end should normally choose to delete these variable
31168 In the future new values may be added to this list so the front should
31169 be prepared for this possibility. @xref{GDB/MI Development and Front Ends, ,@sc{GDB/MI} Development and Front Ends}.
31172 This is only present if the varobj is still valid. If the type
31173 changed, then this will be the string @samp{true}; otherwise it will
31176 When a varobj's type changes, its children are also likely to have
31177 become incorrect. Therefore, the varobj's children are automatically
31178 deleted when this attribute is @samp{true}. Also, the varobj's update
31179 range, when set using the @code{-var-set-update-range} command, is
31183 If the varobj's type changed, then this field will be present and will
31186 @item new_num_children
31187 For a dynamic varobj, if the number of children changed, or if the
31188 type changed, this will be the new number of children.
31190 The @samp{numchild} field in other varobj responses is generally not
31191 valid for a dynamic varobj -- it will show the number of children that
31192 @value{GDBN} knows about, but because dynamic varobjs lazily
31193 instantiate their children, this will not reflect the number of
31194 children which may be available.
31196 The @samp{new_num_children} attribute only reports changes to the
31197 number of children known by @value{GDBN}. This is the only way to
31198 detect whether an update has removed children (which necessarily can
31199 only happen at the end of the update range).
31202 The display hint, if any.
31205 This is an integer value, which will be 1 if there are more children
31206 available outside the varobj's update range.
31209 This attribute will be present and have the value @samp{1} if the
31210 varobj is a dynamic varobj. If the varobj is not a dynamic varobj,
31211 then this attribute will not be present.
31214 If new children were added to a dynamic varobj within the selected
31215 update range (as set by @code{-var-set-update-range}), then they will
31216 be listed in this attribute.
31219 @subsubheading Example
31226 -var-update --all-values var1
31227 ^done,changelist=[@{name="var1",value="3",in_scope="true",
31228 type_changed="false"@}]
31232 @subheading The @code{-var-set-frozen} Command
31233 @findex -var-set-frozen
31234 @anchor{-var-set-frozen}
31236 @subsubheading Synopsis
31239 -var-set-frozen @var{name} @var{flag}
31242 Set the frozenness flag on the variable object @var{name}. The
31243 @var{flag} parameter should be either @samp{1} to make the variable
31244 frozen or @samp{0} to make it unfrozen. If a variable object is
31245 frozen, then neither itself, nor any of its children, are
31246 implicitly updated by @code{-var-update} of
31247 a parent variable or by @code{-var-update *}. Only
31248 @code{-var-update} of the variable itself will update its value and
31249 values of its children. After a variable object is unfrozen, it is
31250 implicitly updated by all subsequent @code{-var-update} operations.
31251 Unfreezing a variable does not update it, only subsequent
31252 @code{-var-update} does.
31254 @subsubheading Example
31258 -var-set-frozen V 1
31263 @subheading The @code{-var-set-update-range} command
31264 @findex -var-set-update-range
31265 @anchor{-var-set-update-range}
31267 @subsubheading Synopsis
31270 -var-set-update-range @var{name} @var{from} @var{to}
31273 Set the range of children to be returned by future invocations of
31274 @code{-var-update}.
31276 @var{from} and @var{to} indicate the range of children to report. If
31277 @var{from} or @var{to} is less than zero, the range is reset and all
31278 children will be reported. Otherwise, children starting at @var{from}
31279 (zero-based) and up to and excluding @var{to} will be reported.
31281 @subsubheading Example
31285 -var-set-update-range V 1 2
31289 @subheading The @code{-var-set-visualizer} command
31290 @findex -var-set-visualizer
31291 @anchor{-var-set-visualizer}
31293 @subsubheading Synopsis
31296 -var-set-visualizer @var{name} @var{visualizer}
31299 Set a visualizer for the variable object @var{name}.
31301 @var{visualizer} is the visualizer to use. The special value
31302 @samp{None} means to disable any visualizer in use.
31304 If not @samp{None}, @var{visualizer} must be a Python expression.
31305 This expression must evaluate to a callable object which accepts a
31306 single argument. @value{GDBN} will call this object with the value of
31307 the varobj @var{name} as an argument (this is done so that the same
31308 Python pretty-printing code can be used for both the CLI and MI).
31309 When called, this object must return an object which conforms to the
31310 pretty-printing interface (@pxref{Pretty Printing API}).
31312 The pre-defined function @code{gdb.default_visualizer} may be used to
31313 select a visualizer by following the built-in process
31314 (@pxref{Selecting Pretty-Printers}). This is done automatically when
31315 a varobj is created, and so ordinarily is not needed.
31317 This feature is only available if Python support is enabled. The MI
31318 command @code{-list-features} (@pxref{GDB/MI Miscellaneous Commands})
31319 can be used to check this.
31321 @subsubheading Example
31323 Resetting the visualizer:
31327 -var-set-visualizer V None
31331 Reselecting the default (type-based) visualizer:
31335 -var-set-visualizer V gdb.default_visualizer
31339 Suppose @code{SomeClass} is a visualizer class. A lambda expression
31340 can be used to instantiate this class for a varobj:
31344 -var-set-visualizer V "lambda val: SomeClass()"
31348 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
31349 @node GDB/MI Data Manipulation
31350 @section @sc{gdb/mi} Data Manipulation
31352 @cindex data manipulation, in @sc{gdb/mi}
31353 @cindex @sc{gdb/mi}, data manipulation
31354 This section describes the @sc{gdb/mi} commands that manipulate data:
31355 examine memory and registers, evaluate expressions, etc.
31357 @c REMOVED FROM THE INTERFACE.
31358 @c @subheading -data-assign
31359 @c Change the value of a program variable. Plenty of side effects.
31360 @c @subsubheading GDB Command
31362 @c @subsubheading Example
31365 @subheading The @code{-data-disassemble} Command
31366 @findex -data-disassemble
31368 @subsubheading Synopsis
31372 [ -s @var{start-addr} -e @var{end-addr} ]
31373 | [ -f @var{filename} -l @var{linenum} [ -n @var{lines} ] ]
31381 @item @var{start-addr}
31382 is the beginning address (or @code{$pc})
31383 @item @var{end-addr}
31385 @item @var{filename}
31386 is the name of the file to disassemble
31387 @item @var{linenum}
31388 is the line number to disassemble around
31390 is the number of disassembly lines to be produced. If it is -1,
31391 the whole function will be disassembled, in case no @var{end-addr} is
31392 specified. If @var{end-addr} is specified as a non-zero value, and
31393 @var{lines} is lower than the number of disassembly lines between
31394 @var{start-addr} and @var{end-addr}, only @var{lines} lines are
31395 displayed; if @var{lines} is higher than the number of lines between
31396 @var{start-addr} and @var{end-addr}, only the lines up to @var{end-addr}
31399 is either 0 (meaning only disassembly), 1 (meaning mixed source and
31400 disassembly), 2 (meaning disassembly with raw opcodes), or 3 (meaning
31401 mixed source and disassembly with raw opcodes).
31404 @subsubheading Result
31406 The result of the @code{-data-disassemble} command will be a list named
31407 @samp{asm_insns}, the contents of this list depend on the @var{mode}
31408 used with the @code{-data-disassemble} command.
31410 For modes 0 and 2 the @samp{asm_insns} list contains tuples with the
31415 The address at which this instruction was disassembled.
31418 The name of the function this instruction is within.
31421 The decimal offset in bytes from the start of @samp{func-name}.
31424 The text disassembly for this @samp{address}.
31427 This field is only present for mode 2. This contains the raw opcode
31428 bytes for the @samp{inst} field.
31432 For modes 1 and 3 the @samp{asm_insns} list contains tuples named
31433 @samp{src_and_asm_line}, each of which has the following fields:
31437 The line number within @samp{file}.
31440 The file name from the compilation unit. This might be an absolute
31441 file name or a relative file name depending on the compile command
31445 Absolute file name of @samp{file}. It is converted to a canonical form
31446 using the source file search path
31447 (@pxref{Source Path, ,Specifying Source Directories})
31448 and after resolving all the symbolic links.
31450 If the source file is not found this field will contain the path as
31451 present in the debug information.
31453 @item line_asm_insn
31454 This is a list of tuples containing the disassembly for @samp{line} in
31455 @samp{file}. The fields of each tuple are the same as for
31456 @code{-data-disassemble} in @var{mode} 0 and 2, so @samp{address},
31457 @samp{func-name}, @samp{offset}, @samp{inst}, and optionally
31462 Note that whatever included in the @samp{inst} field, is not
31463 manipulated directly by @sc{gdb/mi}, i.e., it is not possible to
31466 @subsubheading @value{GDBN} Command
31468 The corresponding @value{GDBN} command is @samp{disassemble}.
31470 @subsubheading Example
31472 Disassemble from the current value of @code{$pc} to @code{$pc + 20}:
31476 -data-disassemble -s $pc -e "$pc + 20" -- 0
31479 @{address="0x000107c0",func-name="main",offset="4",
31480 inst="mov 2, %o0"@},
31481 @{address="0x000107c4",func-name="main",offset="8",
31482 inst="sethi %hi(0x11800), %o2"@},
31483 @{address="0x000107c8",func-name="main",offset="12",
31484 inst="or %o2, 0x140, %o1\t! 0x11940 <_lib_version+8>"@},
31485 @{address="0x000107cc",func-name="main",offset="16",
31486 inst="sethi %hi(0x11800), %o2"@},
31487 @{address="0x000107d0",func-name="main",offset="20",
31488 inst="or %o2, 0x168, %o4\t! 0x11968 <_lib_version+48>"@}]
31492 Disassemble the whole @code{main} function. Line 32 is part of
31496 -data-disassemble -f basics.c -l 32 -- 0
31498 @{address="0x000107bc",func-name="main",offset="0",
31499 inst="save %sp, -112, %sp"@},
31500 @{address="0x000107c0",func-name="main",offset="4",
31501 inst="mov 2, %o0"@},
31502 @{address="0x000107c4",func-name="main",offset="8",
31503 inst="sethi %hi(0x11800), %o2"@},
31505 @{address="0x0001081c",func-name="main",offset="96",inst="ret "@},
31506 @{address="0x00010820",func-name="main",offset="100",inst="restore "@}]
31510 Disassemble 3 instructions from the start of @code{main}:
31514 -data-disassemble -f basics.c -l 32 -n 3 -- 0
31516 @{address="0x000107bc",func-name="main",offset="0",
31517 inst="save %sp, -112, %sp"@},
31518 @{address="0x000107c0",func-name="main",offset="4",
31519 inst="mov 2, %o0"@},
31520 @{address="0x000107c4",func-name="main",offset="8",
31521 inst="sethi %hi(0x11800), %o2"@}]
31525 Disassemble 3 instructions from the start of @code{main} in mixed mode:
31529 -data-disassemble -f basics.c -l 32 -n 3 -- 1
31531 src_and_asm_line=@{line="31",
31532 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31533 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31534 line_asm_insn=[@{address="0x000107bc",
31535 func-name="main",offset="0",inst="save %sp, -112, %sp"@}]@},
31536 src_and_asm_line=@{line="32",
31537 file="../../../src/gdb/testsuite/gdb.mi/basics.c",
31538 fullname="/absolute/path/to/src/gdb/testsuite/gdb.mi/basics.c",
31539 line_asm_insn=[@{address="0x000107c0",
31540 func-name="main",offset="4",inst="mov 2, %o0"@},
31541 @{address="0x000107c4",func-name="main",offset="8",
31542 inst="sethi %hi(0x11800), %o2"@}]@}]
31547 @subheading The @code{-data-evaluate-expression} Command
31548 @findex -data-evaluate-expression
31550 @subsubheading Synopsis
31553 -data-evaluate-expression @var{expr}
31556 Evaluate @var{expr} as an expression. The expression could contain an
31557 inferior function call. The function call will execute synchronously.
31558 If the expression contains spaces, it must be enclosed in double quotes.
31560 @subsubheading @value{GDBN} Command
31562 The corresponding @value{GDBN} commands are @samp{print}, @samp{output}, and
31563 @samp{call}. In @code{gdbtk} only, there's a corresponding
31564 @samp{gdb_eval} command.
31566 @subsubheading Example
31568 In the following example, the numbers that precede the commands are the
31569 @dfn{tokens} described in @ref{GDB/MI Command Syntax, ,@sc{gdb/mi}
31570 Command Syntax}. Notice how @sc{gdb/mi} returns the same tokens in its
31574 211-data-evaluate-expression A
31577 311-data-evaluate-expression &A
31578 311^done,value="0xefffeb7c"
31580 411-data-evaluate-expression A+3
31583 511-data-evaluate-expression "A + 3"
31589 @subheading The @code{-data-list-changed-registers} Command
31590 @findex -data-list-changed-registers
31592 @subsubheading Synopsis
31595 -data-list-changed-registers
31598 Display a list of the registers that have changed.
31600 @subsubheading @value{GDBN} Command
31602 @value{GDBN} doesn't have a direct analog for this command; @code{gdbtk}
31603 has the corresponding command @samp{gdb_changed_register_list}.
31605 @subsubheading Example
31607 On a PPC MBX board:
31615 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",frame=@{
31616 func="main",args=[],file="try.c",fullname="/home/foo/bar/try.c",
31619 -data-list-changed-registers
31620 ^done,changed-registers=["0","1","2","4","5","6","7","8","9",
31621 "10","11","13","14","15","16","17","18","19","20","21","22","23",
31622 "24","25","26","27","28","30","31","64","65","66","67","69"]
31627 @subheading The @code{-data-list-register-names} Command
31628 @findex -data-list-register-names
31630 @subsubheading Synopsis
31633 -data-list-register-names [ ( @var{regno} )+ ]
31636 Show a list of register names for the current target. If no arguments
31637 are given, it shows a list of the names of all the registers. If
31638 integer numbers are given as arguments, it will print a list of the
31639 names of the registers corresponding to the arguments. To ensure
31640 consistency between a register name and its number, the output list may
31641 include empty register names.
31643 @subsubheading @value{GDBN} Command
31645 @value{GDBN} does not have a command which corresponds to
31646 @samp{-data-list-register-names}. In @code{gdbtk} there is a
31647 corresponding command @samp{gdb_regnames}.
31649 @subsubheading Example
31651 For the PPC MBX board:
31654 -data-list-register-names
31655 ^done,register-names=["r0","r1","r2","r3","r4","r5","r6","r7",
31656 "r8","r9","r10","r11","r12","r13","r14","r15","r16","r17","r18",
31657 "r19","r20","r21","r22","r23","r24","r25","r26","r27","r28","r29",
31658 "r30","r31","f0","f1","f2","f3","f4","f5","f6","f7","f8","f9",
31659 "f10","f11","f12","f13","f14","f15","f16","f17","f18","f19","f20",
31660 "f21","f22","f23","f24","f25","f26","f27","f28","f29","f30","f31",
31661 "", "pc","ps","cr","lr","ctr","xer"]
31663 -data-list-register-names 1 2 3
31664 ^done,register-names=["r1","r2","r3"]
31668 @subheading The @code{-data-list-register-values} Command
31669 @findex -data-list-register-values
31671 @subsubheading Synopsis
31674 -data-list-register-values @var{fmt} [ ( @var{regno} )*]
31677 Display the registers' contents. @var{fmt} is the format according to
31678 which the registers' contents are to be returned, followed by an optional
31679 list of numbers specifying the registers to display. A missing list of
31680 numbers indicates that the contents of all the registers must be returned.
31682 Allowed formats for @var{fmt} are:
31699 @subsubheading @value{GDBN} Command
31701 The corresponding @value{GDBN} commands are @samp{info reg}, @samp{info
31702 all-reg}, and (in @code{gdbtk}) @samp{gdb_fetch_registers}.
31704 @subsubheading Example
31706 For a PPC MBX board (note: line breaks are for readability only, they
31707 don't appear in the actual output):
31711 -data-list-register-values r 64 65
31712 ^done,register-values=[@{number="64",value="0xfe00a300"@},
31713 @{number="65",value="0x00029002"@}]
31715 -data-list-register-values x
31716 ^done,register-values=[@{number="0",value="0xfe0043c8"@},
31717 @{number="1",value="0x3fff88"@},@{number="2",value="0xfffffffe"@},
31718 @{number="3",value="0x0"@},@{number="4",value="0xa"@},
31719 @{number="5",value="0x3fff68"@},@{number="6",value="0x3fff58"@},
31720 @{number="7",value="0xfe011e98"@},@{number="8",value="0x2"@},
31721 @{number="9",value="0xfa202820"@},@{number="10",value="0xfa202808"@},
31722 @{number="11",value="0x1"@},@{number="12",value="0x0"@},
31723 @{number="13",value="0x4544"@},@{number="14",value="0xffdfffff"@},
31724 @{number="15",value="0xffffffff"@},@{number="16",value="0xfffffeff"@},
31725 @{number="17",value="0xefffffed"@},@{number="18",value="0xfffffffe"@},
31726 @{number="19",value="0xffffffff"@},@{number="20",value="0xffffffff"@},
31727 @{number="21",value="0xffffffff"@},@{number="22",value="0xfffffff7"@},
31728 @{number="23",value="0xffffffff"@},@{number="24",value="0xffffffff"@},
31729 @{number="25",value="0xffffffff"@},@{number="26",value="0xfffffffb"@},
31730 @{number="27",value="0xffffffff"@},@{number="28",value="0xf7bfffff"@},
31731 @{number="29",value="0x0"@},@{number="30",value="0xfe010000"@},
31732 @{number="31",value="0x0"@},@{number="32",value="0x0"@},
31733 @{number="33",value="0x0"@},@{number="34",value="0x0"@},
31734 @{number="35",value="0x0"@},@{number="36",value="0x0"@},
31735 @{number="37",value="0x0"@},@{number="38",value="0x0"@},
31736 @{number="39",value="0x0"@},@{number="40",value="0x0"@},
31737 @{number="41",value="0x0"@},@{number="42",value="0x0"@},
31738 @{number="43",value="0x0"@},@{number="44",value="0x0"@},
31739 @{number="45",value="0x0"@},@{number="46",value="0x0"@},
31740 @{number="47",value="0x0"@},@{number="48",value="0x0"@},
31741 @{number="49",value="0x0"@},@{number="50",value="0x0"@},
31742 @{number="51",value="0x0"@},@{number="52",value="0x0"@},
31743 @{number="53",value="0x0"@},@{number="54",value="0x0"@},
31744 @{number="55",value="0x0"@},@{number="56",value="0x0"@},
31745 @{number="57",value="0x0"@},@{number="58",value="0x0"@},
31746 @{number="59",value="0x0"@},@{number="60",value="0x0"@},
31747 @{number="61",value="0x0"@},@{number="62",value="0x0"@},
31748 @{number="63",value="0x0"@},@{number="64",value="0xfe00a300"@},
31749 @{number="65",value="0x29002"@},@{number="66",value="0x202f04b5"@},
31750 @{number="67",value="0xfe0043b0"@},@{number="68",value="0xfe00b3e4"@},
31751 @{number="69",value="0x20002b03"@}]
31756 @subheading The @code{-data-read-memory} Command
31757 @findex -data-read-memory
31759 This command is deprecated, use @code{-data-read-memory-bytes} instead.
31761 @subsubheading Synopsis
31764 -data-read-memory [ -o @var{byte-offset} ]
31765 @var{address} @var{word-format} @var{word-size}
31766 @var{nr-rows} @var{nr-cols} [ @var{aschar} ]
31773 @item @var{address}
31774 An expression specifying the address of the first memory word to be
31775 read. Complex expressions containing embedded white space should be
31776 quoted using the C convention.
31778 @item @var{word-format}
31779 The format to be used to print the memory words. The notation is the
31780 same as for @value{GDBN}'s @code{print} command (@pxref{Output Formats,
31783 @item @var{word-size}
31784 The size of each memory word in bytes.
31786 @item @var{nr-rows}
31787 The number of rows in the output table.
31789 @item @var{nr-cols}
31790 The number of columns in the output table.
31793 If present, indicates that each row should include an @sc{ascii} dump. The
31794 value of @var{aschar} is used as a padding character when a byte is not a
31795 member of the printable @sc{ascii} character set (printable @sc{ascii}
31796 characters are those whose code is between 32 and 126, inclusively).
31798 @item @var{byte-offset}
31799 An offset to add to the @var{address} before fetching memory.
31802 This command displays memory contents as a table of @var{nr-rows} by
31803 @var{nr-cols} words, each word being @var{word-size} bytes. In total,
31804 @code{@var{nr-rows} * @var{nr-cols} * @var{word-size}} bytes are read
31805 (returned as @samp{total-bytes}). Should less than the requested number
31806 of bytes be returned by the target, the missing words are identified
31807 using @samp{N/A}. The number of bytes read from the target is returned
31808 in @samp{nr-bytes} and the starting address used to read memory in
31811 The address of the next/previous row or page is available in
31812 @samp{next-row} and @samp{prev-row}, @samp{next-page} and
31815 @subsubheading @value{GDBN} Command
31817 The corresponding @value{GDBN} command is @samp{x}. @code{gdbtk} has
31818 @samp{gdb_get_mem} memory read command.
31820 @subsubheading Example
31822 Read six bytes of memory starting at @code{bytes+6} but then offset by
31823 @code{-6} bytes. Format as three rows of two columns. One byte per
31824 word. Display each word in hex.
31828 9-data-read-memory -o -6 -- bytes+6 x 1 3 2
31829 9^done,addr="0x00001390",nr-bytes="6",total-bytes="6",
31830 next-row="0x00001396",prev-row="0x0000138e",next-page="0x00001396",
31831 prev-page="0x0000138a",memory=[
31832 @{addr="0x00001390",data=["0x00","0x01"]@},
31833 @{addr="0x00001392",data=["0x02","0x03"]@},
31834 @{addr="0x00001394",data=["0x04","0x05"]@}]
31838 Read two bytes of memory starting at address @code{shorts + 64} and
31839 display as a single word formatted in decimal.
31843 5-data-read-memory shorts+64 d 2 1 1
31844 5^done,addr="0x00001510",nr-bytes="2",total-bytes="2",
31845 next-row="0x00001512",prev-row="0x0000150e",
31846 next-page="0x00001512",prev-page="0x0000150e",memory=[
31847 @{addr="0x00001510",data=["128"]@}]
31851 Read thirty two bytes of memory starting at @code{bytes+16} and format
31852 as eight rows of four columns. Include a string encoding with @samp{x}
31853 used as the non-printable character.
31857 4-data-read-memory bytes+16 x 1 8 4 x
31858 4^done,addr="0x000013a0",nr-bytes="32",total-bytes="32",
31859 next-row="0x000013c0",prev-row="0x0000139c",
31860 next-page="0x000013c0",prev-page="0x00001380",memory=[
31861 @{addr="0x000013a0",data=["0x10","0x11","0x12","0x13"],ascii="xxxx"@},
31862 @{addr="0x000013a4",data=["0x14","0x15","0x16","0x17"],ascii="xxxx"@},
31863 @{addr="0x000013a8",data=["0x18","0x19","0x1a","0x1b"],ascii="xxxx"@},
31864 @{addr="0x000013ac",data=["0x1c","0x1d","0x1e","0x1f"],ascii="xxxx"@},
31865 @{addr="0x000013b0",data=["0x20","0x21","0x22","0x23"],ascii=" !\"#"@},
31866 @{addr="0x000013b4",data=["0x24","0x25","0x26","0x27"],ascii="$%&'"@},
31867 @{addr="0x000013b8",data=["0x28","0x29","0x2a","0x2b"],ascii="()*+"@},
31868 @{addr="0x000013bc",data=["0x2c","0x2d","0x2e","0x2f"],ascii=",-./"@}]
31872 @subheading The @code{-data-read-memory-bytes} Command
31873 @findex -data-read-memory-bytes
31875 @subsubheading Synopsis
31878 -data-read-memory-bytes [ -o @var{byte-offset} ]
31879 @var{address} @var{count}
31886 @item @var{address}
31887 An expression specifying the address of the first memory word to be
31888 read. Complex expressions containing embedded white space should be
31889 quoted using the C convention.
31892 The number of bytes to read. This should be an integer literal.
31894 @item @var{byte-offset}
31895 The offsets in bytes relative to @var{address} at which to start
31896 reading. This should be an integer literal. This option is provided
31897 so that a frontend is not required to first evaluate address and then
31898 perform address arithmetics itself.
31902 This command attempts to read all accessible memory regions in the
31903 specified range. First, all regions marked as unreadable in the memory
31904 map (if one is defined) will be skipped. @xref{Memory Region
31905 Attributes}. Second, @value{GDBN} will attempt to read the remaining
31906 regions. For each one, if reading full region results in an errors,
31907 @value{GDBN} will try to read a subset of the region.
31909 In general, every single byte in the region may be readable or not,
31910 and the only way to read every readable byte is to try a read at
31911 every address, which is not practical. Therefore, @value{GDBN} will
31912 attempt to read all accessible bytes at either beginning or the end
31913 of the region, using a binary division scheme. This heuristic works
31914 well for reading accross a memory map boundary. Note that if a region
31915 has a readable range that is neither at the beginning or the end,
31916 @value{GDBN} will not read it.
31918 The result record (@pxref{GDB/MI Result Records}) that is output of
31919 the command includes a field named @samp{memory} whose content is a
31920 list of tuples. Each tuple represent a successfully read memory block
31921 and has the following fields:
31925 The start address of the memory block, as hexadecimal literal.
31928 The end address of the memory block, as hexadecimal literal.
31931 The offset of the memory block, as hexadecimal literal, relative to
31932 the start address passed to @code{-data-read-memory-bytes}.
31935 The contents of the memory block, in hex.
31941 @subsubheading @value{GDBN} Command
31943 The corresponding @value{GDBN} command is @samp{x}.
31945 @subsubheading Example
31949 -data-read-memory-bytes &a 10
31950 ^done,memory=[@{begin="0xbffff154",offset="0x00000000",
31952 contents="01000000020000000300"@}]
31957 @subheading The @code{-data-write-memory-bytes} Command
31958 @findex -data-write-memory-bytes
31960 @subsubheading Synopsis
31963 -data-write-memory-bytes @var{address} @var{contents}
31964 -data-write-memory-bytes @var{address} @var{contents} @r{[}@var{count}@r{]}
31971 @item @var{address}
31972 An expression specifying the address of the first memory word to be
31973 read. Complex expressions containing embedded white space should be
31974 quoted using the C convention.
31976 @item @var{contents}
31977 The hex-encoded bytes to write.
31980 Optional argument indicating the number of bytes to be written. If @var{count}
31981 is greater than @var{contents}' length, @value{GDBN} will repeatedly
31982 write @var{contents} until it fills @var{count} bytes.
31986 @subsubheading @value{GDBN} Command
31988 There's no corresponding @value{GDBN} command.
31990 @subsubheading Example
31994 -data-write-memory-bytes &a "aabbccdd"
32001 -data-write-memory-bytes &a "aabbccdd" 16e
32006 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32007 @node GDB/MI Tracepoint Commands
32008 @section @sc{gdb/mi} Tracepoint Commands
32010 The commands defined in this section implement MI support for
32011 tracepoints. For detailed introduction, see @ref{Tracepoints}.
32013 @subheading The @code{-trace-find} Command
32014 @findex -trace-find
32016 @subsubheading Synopsis
32019 -trace-find @var{mode} [@var{parameters}@dots{}]
32022 Find a trace frame using criteria defined by @var{mode} and
32023 @var{parameters}. The following table lists permissible
32024 modes and their parameters. For details of operation, see @ref{tfind}.
32029 No parameters are required. Stops examining trace frames.
32032 An integer is required as parameter. Selects tracepoint frame with
32035 @item tracepoint-number
32036 An integer is required as parameter. Finds next
32037 trace frame that corresponds to tracepoint with the specified number.
32040 An address is required as parameter. Finds
32041 next trace frame that corresponds to any tracepoint at the specified
32044 @item pc-inside-range
32045 Two addresses are required as parameters. Finds next trace
32046 frame that corresponds to a tracepoint at an address inside the
32047 specified range. Both bounds are considered to be inside the range.
32049 @item pc-outside-range
32050 Two addresses are required as parameters. Finds
32051 next trace frame that corresponds to a tracepoint at an address outside
32052 the specified range. Both bounds are considered to be inside the range.
32055 Line specification is required as parameter. @xref{Specify Location}.
32056 Finds next trace frame that corresponds to a tracepoint at
32057 the specified location.
32061 If @samp{none} was passed as @var{mode}, the response does not
32062 have fields. Otherwise, the response may have the following fields:
32066 This field has either @samp{0} or @samp{1} as the value, depending
32067 on whether a matching tracepoint was found.
32070 The index of the found traceframe. This field is present iff
32071 the @samp{found} field has value of @samp{1}.
32074 The index of the found tracepoint. This field is present iff
32075 the @samp{found} field has value of @samp{1}.
32078 The information about the frame corresponding to the found trace
32079 frame. This field is present only if a trace frame was found.
32080 @xref{GDB/MI Frame Information}, for description of this field.
32084 @subsubheading @value{GDBN} Command
32086 The corresponding @value{GDBN} command is @samp{tfind}.
32088 @subheading -trace-define-variable
32089 @findex -trace-define-variable
32091 @subsubheading Synopsis
32094 -trace-define-variable @var{name} [ @var{value} ]
32097 Create trace variable @var{name} if it does not exist. If
32098 @var{value} is specified, sets the initial value of the specified
32099 trace variable to that value. Note that the @var{name} should start
32100 with the @samp{$} character.
32102 @subsubheading @value{GDBN} Command
32104 The corresponding @value{GDBN} command is @samp{tvariable}.
32106 @subheading -trace-list-variables
32107 @findex -trace-list-variables
32109 @subsubheading Synopsis
32112 -trace-list-variables
32115 Return a table of all defined trace variables. Each element of the
32116 table has the following fields:
32120 The name of the trace variable. This field is always present.
32123 The initial value. This is a 64-bit signed integer. This
32124 field is always present.
32127 The value the trace variable has at the moment. This is a 64-bit
32128 signed integer. This field is absent iff current value is
32129 not defined, for example if the trace was never run, or is
32134 @subsubheading @value{GDBN} Command
32136 The corresponding @value{GDBN} command is @samp{tvariables}.
32138 @subsubheading Example
32142 -trace-list-variables
32143 ^done,trace-variables=@{nr_rows="1",nr_cols="3",
32144 hdr=[@{width="15",alignment="-1",col_name="name",colhdr="Name"@},
32145 @{width="11",alignment="-1",col_name="initial",colhdr="Initial"@},
32146 @{width="11",alignment="-1",col_name="current",colhdr="Current"@}],
32147 body=[variable=@{name="$trace_timestamp",initial="0"@}
32148 variable=@{name="$foo",initial="10",current="15"@}]@}
32152 @subheading -trace-save
32153 @findex -trace-save
32155 @subsubheading Synopsis
32158 -trace-save [-r ] @var{filename}
32161 Saves the collected trace data to @var{filename}. Without the
32162 @samp{-r} option, the data is downloaded from the target and saved
32163 in a local file. With the @samp{-r} option the target is asked
32164 to perform the save.
32166 @subsubheading @value{GDBN} Command
32168 The corresponding @value{GDBN} command is @samp{tsave}.
32171 @subheading -trace-start
32172 @findex -trace-start
32174 @subsubheading Synopsis
32180 Starts a tracing experiments. The result of this command does not
32183 @subsubheading @value{GDBN} Command
32185 The corresponding @value{GDBN} command is @samp{tstart}.
32187 @subheading -trace-status
32188 @findex -trace-status
32190 @subsubheading Synopsis
32196 Obtains the status of a tracing experiment. The result may include
32197 the following fields:
32202 May have a value of either @samp{0}, when no tracing operations are
32203 supported, @samp{1}, when all tracing operations are supported, or
32204 @samp{file} when examining trace file. In the latter case, examining
32205 of trace frame is possible but new tracing experiement cannot be
32206 started. This field is always present.
32209 May have a value of either @samp{0} or @samp{1} depending on whether
32210 tracing experiement is in progress on target. This field is present
32211 if @samp{supported} field is not @samp{0}.
32214 Report the reason why the tracing was stopped last time. This field
32215 may be absent iff tracing was never stopped on target yet. The
32216 value of @samp{request} means the tracing was stopped as result of
32217 the @code{-trace-stop} command. The value of @samp{overflow} means
32218 the tracing buffer is full. The value of @samp{disconnection} means
32219 tracing was automatically stopped when @value{GDBN} has disconnected.
32220 The value of @samp{passcount} means tracing was stopped when a
32221 tracepoint was passed a maximal number of times for that tracepoint.
32222 This field is present if @samp{supported} field is not @samp{0}.
32224 @item stopping-tracepoint
32225 The number of tracepoint whose passcount as exceeded. This field is
32226 present iff the @samp{stop-reason} field has the value of
32230 @itemx frames-created
32231 The @samp{frames} field is a count of the total number of trace frames
32232 in the trace buffer, while @samp{frames-created} is the total created
32233 during the run, including ones that were discarded, such as when a
32234 circular trace buffer filled up. Both fields are optional.
32238 These fields tell the current size of the tracing buffer and the
32239 remaining space. These fields are optional.
32242 The value of the circular trace buffer flag. @code{1} means that the
32243 trace buffer is circular and old trace frames will be discarded if
32244 necessary to make room, @code{0} means that the trace buffer is linear
32248 The value of the disconnected tracing flag. @code{1} means that
32249 tracing will continue after @value{GDBN} disconnects, @code{0} means
32250 that the trace run will stop.
32253 The filename of the trace file being examined. This field is
32254 optional, and only present when examining a trace file.
32258 @subsubheading @value{GDBN} Command
32260 The corresponding @value{GDBN} command is @samp{tstatus}.
32262 @subheading -trace-stop
32263 @findex -trace-stop
32265 @subsubheading Synopsis
32271 Stops a tracing experiment. The result of this command has the same
32272 fields as @code{-trace-status}, except that the @samp{supported} and
32273 @samp{running} fields are not output.
32275 @subsubheading @value{GDBN} Command
32277 The corresponding @value{GDBN} command is @samp{tstop}.
32280 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32281 @node GDB/MI Symbol Query
32282 @section @sc{gdb/mi} Symbol Query Commands
32286 @subheading The @code{-symbol-info-address} Command
32287 @findex -symbol-info-address
32289 @subsubheading Synopsis
32292 -symbol-info-address @var{symbol}
32295 Describe where @var{symbol} is stored.
32297 @subsubheading @value{GDBN} Command
32299 The corresponding @value{GDBN} command is @samp{info address}.
32301 @subsubheading Example
32305 @subheading The @code{-symbol-info-file} Command
32306 @findex -symbol-info-file
32308 @subsubheading Synopsis
32314 Show the file for the symbol.
32316 @subsubheading @value{GDBN} Command
32318 There's no equivalent @value{GDBN} command. @code{gdbtk} has
32319 @samp{gdb_find_file}.
32321 @subsubheading Example
32325 @subheading The @code{-symbol-info-function} Command
32326 @findex -symbol-info-function
32328 @subsubheading Synopsis
32331 -symbol-info-function
32334 Show which function the symbol lives in.
32336 @subsubheading @value{GDBN} Command
32338 @samp{gdb_get_function} in @code{gdbtk}.
32340 @subsubheading Example
32344 @subheading The @code{-symbol-info-line} Command
32345 @findex -symbol-info-line
32347 @subsubheading Synopsis
32353 Show the core addresses of the code for a source line.
32355 @subsubheading @value{GDBN} Command
32357 The corresponding @value{GDBN} command is @samp{info line}.
32358 @code{gdbtk} has the @samp{gdb_get_line} and @samp{gdb_get_file} commands.
32360 @subsubheading Example
32364 @subheading The @code{-symbol-info-symbol} Command
32365 @findex -symbol-info-symbol
32367 @subsubheading Synopsis
32370 -symbol-info-symbol @var{addr}
32373 Describe what symbol is at location @var{addr}.
32375 @subsubheading @value{GDBN} Command
32377 The corresponding @value{GDBN} command is @samp{info symbol}.
32379 @subsubheading Example
32383 @subheading The @code{-symbol-list-functions} Command
32384 @findex -symbol-list-functions
32386 @subsubheading Synopsis
32389 -symbol-list-functions
32392 List the functions in the executable.
32394 @subsubheading @value{GDBN} Command
32396 @samp{info functions} in @value{GDBN}, @samp{gdb_listfunc} and
32397 @samp{gdb_search} in @code{gdbtk}.
32399 @subsubheading Example
32404 @subheading The @code{-symbol-list-lines} Command
32405 @findex -symbol-list-lines
32407 @subsubheading Synopsis
32410 -symbol-list-lines @var{filename}
32413 Print the list of lines that contain code and their associated program
32414 addresses for the given source filename. The entries are sorted in
32415 ascending PC order.
32417 @subsubheading @value{GDBN} Command
32419 There is no corresponding @value{GDBN} command.
32421 @subsubheading Example
32424 -symbol-list-lines basics.c
32425 ^done,lines=[@{pc="0x08048554",line="7"@},@{pc="0x0804855a",line="8"@}]
32431 @subheading The @code{-symbol-list-types} Command
32432 @findex -symbol-list-types
32434 @subsubheading Synopsis
32440 List all the type names.
32442 @subsubheading @value{GDBN} Command
32444 The corresponding commands are @samp{info types} in @value{GDBN},
32445 @samp{gdb_search} in @code{gdbtk}.
32447 @subsubheading Example
32451 @subheading The @code{-symbol-list-variables} Command
32452 @findex -symbol-list-variables
32454 @subsubheading Synopsis
32457 -symbol-list-variables
32460 List all the global and static variable names.
32462 @subsubheading @value{GDBN} Command
32464 @samp{info variables} in @value{GDBN}, @samp{gdb_search} in @code{gdbtk}.
32466 @subsubheading Example
32470 @subheading The @code{-symbol-locate} Command
32471 @findex -symbol-locate
32473 @subsubheading Synopsis
32479 @subsubheading @value{GDBN} Command
32481 @samp{gdb_loc} in @code{gdbtk}.
32483 @subsubheading Example
32487 @subheading The @code{-symbol-type} Command
32488 @findex -symbol-type
32490 @subsubheading Synopsis
32493 -symbol-type @var{variable}
32496 Show type of @var{variable}.
32498 @subsubheading @value{GDBN} Command
32500 The corresponding @value{GDBN} command is @samp{ptype}, @code{gdbtk} has
32501 @samp{gdb_obj_variable}.
32503 @subsubheading Example
32508 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32509 @node GDB/MI File Commands
32510 @section @sc{gdb/mi} File Commands
32512 This section describes the GDB/MI commands to specify executable file names
32513 and to read in and obtain symbol table information.
32515 @subheading The @code{-file-exec-and-symbols} Command
32516 @findex -file-exec-and-symbols
32518 @subsubheading Synopsis
32521 -file-exec-and-symbols @var{file}
32524 Specify the executable file to be debugged. This file is the one from
32525 which the symbol table is also read. If no file is specified, the
32526 command clears the executable and symbol information. If breakpoints
32527 are set when using this command with no arguments, @value{GDBN} will produce
32528 error messages. Otherwise, no output is produced, except a completion
32531 @subsubheading @value{GDBN} Command
32533 The corresponding @value{GDBN} command is @samp{file}.
32535 @subsubheading Example
32539 -file-exec-and-symbols /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32545 @subheading The @code{-file-exec-file} Command
32546 @findex -file-exec-file
32548 @subsubheading Synopsis
32551 -file-exec-file @var{file}
32554 Specify the executable file to be debugged. Unlike
32555 @samp{-file-exec-and-symbols}, the symbol table is @emph{not} read
32556 from this file. If used without argument, @value{GDBN} clears the information
32557 about the executable file. No output is produced, except a completion
32560 @subsubheading @value{GDBN} Command
32562 The corresponding @value{GDBN} command is @samp{exec-file}.
32564 @subsubheading Example
32568 -file-exec-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32575 @subheading The @code{-file-list-exec-sections} Command
32576 @findex -file-list-exec-sections
32578 @subsubheading Synopsis
32581 -file-list-exec-sections
32584 List the sections of the current executable file.
32586 @subsubheading @value{GDBN} Command
32588 The @value{GDBN} command @samp{info file} shows, among the rest, the same
32589 information as this command. @code{gdbtk} has a corresponding command
32590 @samp{gdb_load_info}.
32592 @subsubheading Example
32597 @subheading The @code{-file-list-exec-source-file} Command
32598 @findex -file-list-exec-source-file
32600 @subsubheading Synopsis
32603 -file-list-exec-source-file
32606 List the line number, the current source file, and the absolute path
32607 to the current source file for the current executable. The macro
32608 information field has a value of @samp{1} or @samp{0} depending on
32609 whether or not the file includes preprocessor macro information.
32611 @subsubheading @value{GDBN} Command
32613 The @value{GDBN} equivalent is @samp{info source}
32615 @subsubheading Example
32619 123-file-list-exec-source-file
32620 123^done,line="1",file="foo.c",fullname="/home/bar/foo.c,macro-info="1"
32625 @subheading The @code{-file-list-exec-source-files} Command
32626 @findex -file-list-exec-source-files
32628 @subsubheading Synopsis
32631 -file-list-exec-source-files
32634 List the source files for the current executable.
32636 It will always output both the filename and fullname (absolute file
32637 name) of a source file.
32639 @subsubheading @value{GDBN} Command
32641 The @value{GDBN} equivalent is @samp{info sources}.
32642 @code{gdbtk} has an analogous command @samp{gdb_listfiles}.
32644 @subsubheading Example
32647 -file-list-exec-source-files
32649 @{file=foo.c,fullname=/home/foo.c@},
32650 @{file=/home/bar.c,fullname=/home/bar.c@},
32651 @{file=gdb_could_not_find_fullpath.c@}]
32656 @subheading The @code{-file-list-shared-libraries} Command
32657 @findex -file-list-shared-libraries
32659 @subsubheading Synopsis
32662 -file-list-shared-libraries
32665 List the shared libraries in the program.
32667 @subsubheading @value{GDBN} Command
32669 The corresponding @value{GDBN} command is @samp{info shared}.
32671 @subsubheading Example
32675 @subheading The @code{-file-list-symbol-files} Command
32676 @findex -file-list-symbol-files
32678 @subsubheading Synopsis
32681 -file-list-symbol-files
32686 @subsubheading @value{GDBN} Command
32688 The corresponding @value{GDBN} command is @samp{info file} (part of it).
32690 @subsubheading Example
32695 @subheading The @code{-file-symbol-file} Command
32696 @findex -file-symbol-file
32698 @subsubheading Synopsis
32701 -file-symbol-file @var{file}
32704 Read symbol table info from the specified @var{file} argument. When
32705 used without arguments, clears @value{GDBN}'s symbol table info. No output is
32706 produced, except for a completion notification.
32708 @subsubheading @value{GDBN} Command
32710 The corresponding @value{GDBN} command is @samp{symbol-file}.
32712 @subsubheading Example
32716 -file-symbol-file /kwikemart/marge/ezannoni/TRUNK/mbx/hello.mbx
32722 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32723 @node GDB/MI Memory Overlay Commands
32724 @section @sc{gdb/mi} Memory Overlay Commands
32726 The memory overlay commands are not implemented.
32728 @c @subheading -overlay-auto
32730 @c @subheading -overlay-list-mapping-state
32732 @c @subheading -overlay-list-overlays
32734 @c @subheading -overlay-map
32736 @c @subheading -overlay-off
32738 @c @subheading -overlay-on
32740 @c @subheading -overlay-unmap
32742 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32743 @node GDB/MI Signal Handling Commands
32744 @section @sc{gdb/mi} Signal Handling Commands
32746 Signal handling commands are not implemented.
32748 @c @subheading -signal-handle
32750 @c @subheading -signal-list-handle-actions
32752 @c @subheading -signal-list-signal-types
32756 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
32757 @node GDB/MI Target Manipulation
32758 @section @sc{gdb/mi} Target Manipulation Commands
32761 @subheading The @code{-target-attach} Command
32762 @findex -target-attach
32764 @subsubheading Synopsis
32767 -target-attach @var{pid} | @var{gid} | @var{file}
32770 Attach to a process @var{pid} or a file @var{file} outside of
32771 @value{GDBN}, or a thread group @var{gid}. If attaching to a thread
32772 group, the id previously returned by
32773 @samp{-list-thread-groups --available} must be used.
32775 @subsubheading @value{GDBN} Command
32777 The corresponding @value{GDBN} command is @samp{attach}.
32779 @subsubheading Example
32783 =thread-created,id="1"
32784 *stopped,thread-id="1",frame=@{addr="0xb7f7e410",func="bar",args=[]@}
32790 @subheading The @code{-target-compare-sections} Command
32791 @findex -target-compare-sections
32793 @subsubheading Synopsis
32796 -target-compare-sections [ @var{section} ]
32799 Compare data of section @var{section} on target to the exec file.
32800 Without the argument, all sections are compared.
32802 @subsubheading @value{GDBN} Command
32804 The @value{GDBN} equivalent is @samp{compare-sections}.
32806 @subsubheading Example
32811 @subheading The @code{-target-detach} Command
32812 @findex -target-detach
32814 @subsubheading Synopsis
32817 -target-detach [ @var{pid} | @var{gid} ]
32820 Detach from the remote target which normally resumes its execution.
32821 If either @var{pid} or @var{gid} is specified, detaches from either
32822 the specified process, or specified thread group. There's no output.
32824 @subsubheading @value{GDBN} Command
32826 The corresponding @value{GDBN} command is @samp{detach}.
32828 @subsubheading Example
32838 @subheading The @code{-target-disconnect} Command
32839 @findex -target-disconnect
32841 @subsubheading Synopsis
32847 Disconnect from the remote target. There's no output and the target is
32848 generally not resumed.
32850 @subsubheading @value{GDBN} Command
32852 The corresponding @value{GDBN} command is @samp{disconnect}.
32854 @subsubheading Example
32864 @subheading The @code{-target-download} Command
32865 @findex -target-download
32867 @subsubheading Synopsis
32873 Loads the executable onto the remote target.
32874 It prints out an update message every half second, which includes the fields:
32878 The name of the section.
32880 The size of what has been sent so far for that section.
32882 The size of the section.
32884 The total size of what was sent so far (the current and the previous sections).
32886 The size of the overall executable to download.
32890 Each message is sent as status record (@pxref{GDB/MI Output Syntax, ,
32891 @sc{gdb/mi} Output Syntax}).
32893 In addition, it prints the name and size of the sections, as they are
32894 downloaded. These messages include the following fields:
32898 The name of the section.
32900 The size of the section.
32902 The size of the overall executable to download.
32906 At the end, a summary is printed.
32908 @subsubheading @value{GDBN} Command
32910 The corresponding @value{GDBN} command is @samp{load}.
32912 @subsubheading Example
32914 Note: each status message appears on a single line. Here the messages
32915 have been broken down so that they can fit onto a page.
32920 +download,@{section=".text",section-size="6668",total-size="9880"@}
32921 +download,@{section=".text",section-sent="512",section-size="6668",
32922 total-sent="512",total-size="9880"@}
32923 +download,@{section=".text",section-sent="1024",section-size="6668",
32924 total-sent="1024",total-size="9880"@}
32925 +download,@{section=".text",section-sent="1536",section-size="6668",
32926 total-sent="1536",total-size="9880"@}
32927 +download,@{section=".text",section-sent="2048",section-size="6668",
32928 total-sent="2048",total-size="9880"@}
32929 +download,@{section=".text",section-sent="2560",section-size="6668",
32930 total-sent="2560",total-size="9880"@}
32931 +download,@{section=".text",section-sent="3072",section-size="6668",
32932 total-sent="3072",total-size="9880"@}
32933 +download,@{section=".text",section-sent="3584",section-size="6668",
32934 total-sent="3584",total-size="9880"@}
32935 +download,@{section=".text",section-sent="4096",section-size="6668",
32936 total-sent="4096",total-size="9880"@}
32937 +download,@{section=".text",section-sent="4608",section-size="6668",
32938 total-sent="4608",total-size="9880"@}
32939 +download,@{section=".text",section-sent="5120",section-size="6668",
32940 total-sent="5120",total-size="9880"@}
32941 +download,@{section=".text",section-sent="5632",section-size="6668",
32942 total-sent="5632",total-size="9880"@}
32943 +download,@{section=".text",section-sent="6144",section-size="6668",
32944 total-sent="6144",total-size="9880"@}
32945 +download,@{section=".text",section-sent="6656",section-size="6668",
32946 total-sent="6656",total-size="9880"@}
32947 +download,@{section=".init",section-size="28",total-size="9880"@}
32948 +download,@{section=".fini",section-size="28",total-size="9880"@}
32949 +download,@{section=".data",section-size="3156",total-size="9880"@}
32950 +download,@{section=".data",section-sent="512",section-size="3156",
32951 total-sent="7236",total-size="9880"@}
32952 +download,@{section=".data",section-sent="1024",section-size="3156",
32953 total-sent="7748",total-size="9880"@}
32954 +download,@{section=".data",section-sent="1536",section-size="3156",
32955 total-sent="8260",total-size="9880"@}
32956 +download,@{section=".data",section-sent="2048",section-size="3156",
32957 total-sent="8772",total-size="9880"@}
32958 +download,@{section=".data",section-sent="2560",section-size="3156",
32959 total-sent="9284",total-size="9880"@}
32960 +download,@{section=".data",section-sent="3072",section-size="3156",
32961 total-sent="9796",total-size="9880"@}
32962 ^done,address="0x10004",load-size="9880",transfer-rate="6586",
32969 @subheading The @code{-target-exec-status} Command
32970 @findex -target-exec-status
32972 @subsubheading Synopsis
32975 -target-exec-status
32978 Provide information on the state of the target (whether it is running or
32979 not, for instance).
32981 @subsubheading @value{GDBN} Command
32983 There's no equivalent @value{GDBN} command.
32985 @subsubheading Example
32989 @subheading The @code{-target-list-available-targets} Command
32990 @findex -target-list-available-targets
32992 @subsubheading Synopsis
32995 -target-list-available-targets
32998 List the possible targets to connect to.
33000 @subsubheading @value{GDBN} Command
33002 The corresponding @value{GDBN} command is @samp{help target}.
33004 @subsubheading Example
33008 @subheading The @code{-target-list-current-targets} Command
33009 @findex -target-list-current-targets
33011 @subsubheading Synopsis
33014 -target-list-current-targets
33017 Describe the current target.
33019 @subsubheading @value{GDBN} Command
33021 The corresponding information is printed by @samp{info file} (among
33024 @subsubheading Example
33028 @subheading The @code{-target-list-parameters} Command
33029 @findex -target-list-parameters
33031 @subsubheading Synopsis
33034 -target-list-parameters
33040 @subsubheading @value{GDBN} Command
33044 @subsubheading Example
33048 @subheading The @code{-target-select} Command
33049 @findex -target-select
33051 @subsubheading Synopsis
33054 -target-select @var{type} @var{parameters @dots{}}
33057 Connect @value{GDBN} to the remote target. This command takes two args:
33061 The type of target, for instance @samp{remote}, etc.
33062 @item @var{parameters}
33063 Device names, host names and the like. @xref{Target Commands, ,
33064 Commands for Managing Targets}, for more details.
33067 The output is a connection notification, followed by the address at
33068 which the target program is, in the following form:
33071 ^connected,addr="@var{address}",func="@var{function name}",
33072 args=[@var{arg list}]
33075 @subsubheading @value{GDBN} Command
33077 The corresponding @value{GDBN} command is @samp{target}.
33079 @subsubheading Example
33083 -target-select remote /dev/ttya
33084 ^connected,addr="0xfe00a300",func="??",args=[]
33088 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33089 @node GDB/MI File Transfer Commands
33090 @section @sc{gdb/mi} File Transfer Commands
33093 @subheading The @code{-target-file-put} Command
33094 @findex -target-file-put
33096 @subsubheading Synopsis
33099 -target-file-put @var{hostfile} @var{targetfile}
33102 Copy file @var{hostfile} from the host system (the machine running
33103 @value{GDBN}) to @var{targetfile} on the target system.
33105 @subsubheading @value{GDBN} Command
33107 The corresponding @value{GDBN} command is @samp{remote put}.
33109 @subsubheading Example
33113 -target-file-put localfile remotefile
33119 @subheading The @code{-target-file-get} Command
33120 @findex -target-file-get
33122 @subsubheading Synopsis
33125 -target-file-get @var{targetfile} @var{hostfile}
33128 Copy file @var{targetfile} from the target system to @var{hostfile}
33129 on the host system.
33131 @subsubheading @value{GDBN} Command
33133 The corresponding @value{GDBN} command is @samp{remote get}.
33135 @subsubheading Example
33139 -target-file-get remotefile localfile
33145 @subheading The @code{-target-file-delete} Command
33146 @findex -target-file-delete
33148 @subsubheading Synopsis
33151 -target-file-delete @var{targetfile}
33154 Delete @var{targetfile} from the target system.
33156 @subsubheading @value{GDBN} Command
33158 The corresponding @value{GDBN} command is @samp{remote delete}.
33160 @subsubheading Example
33164 -target-file-delete remotefile
33170 @c %%%%%%%%%%%%%%%%%%%%%%%%%%%% SECTION %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
33171 @node GDB/MI Miscellaneous Commands
33172 @section Miscellaneous @sc{gdb/mi} Commands
33174 @c @subheading -gdb-complete
33176 @subheading The @code{-gdb-exit} Command
33179 @subsubheading Synopsis
33185 Exit @value{GDBN} immediately.
33187 @subsubheading @value{GDBN} Command
33189 Approximately corresponds to @samp{quit}.
33191 @subsubheading Example
33201 @subheading The @code{-exec-abort} Command
33202 @findex -exec-abort
33204 @subsubheading Synopsis
33210 Kill the inferior running program.
33212 @subsubheading @value{GDBN} Command
33214 The corresponding @value{GDBN} command is @samp{kill}.
33216 @subsubheading Example
33221 @subheading The @code{-gdb-set} Command
33224 @subsubheading Synopsis
33230 Set an internal @value{GDBN} variable.
33231 @c IS THIS A DOLLAR VARIABLE? OR SOMETHING LIKE ANNOTATE ?????
33233 @subsubheading @value{GDBN} Command
33235 The corresponding @value{GDBN} command is @samp{set}.
33237 @subsubheading Example
33247 @subheading The @code{-gdb-show} Command
33250 @subsubheading Synopsis
33256 Show the current value of a @value{GDBN} variable.
33258 @subsubheading @value{GDBN} Command
33260 The corresponding @value{GDBN} command is @samp{show}.
33262 @subsubheading Example
33271 @c @subheading -gdb-source
33274 @subheading The @code{-gdb-version} Command
33275 @findex -gdb-version
33277 @subsubheading Synopsis
33283 Show version information for @value{GDBN}. Used mostly in testing.
33285 @subsubheading @value{GDBN} Command
33287 The @value{GDBN} equivalent is @samp{show version}. @value{GDBN} by
33288 default shows this information when you start an interactive session.
33290 @subsubheading Example
33292 @c This example modifies the actual output from GDB to avoid overfull
33298 ~Copyright 2000 Free Software Foundation, Inc.
33299 ~GDB is free software, covered by the GNU General Public License, and
33300 ~you are welcome to change it and/or distribute copies of it under
33301 ~ certain conditions.
33302 ~Type "show copying" to see the conditions.
33303 ~There is absolutely no warranty for GDB. Type "show warranty" for
33305 ~This GDB was configured as
33306 "--host=sparc-sun-solaris2.5.1 --target=ppc-eabi".
33311 @subheading The @code{-list-features} Command
33312 @findex -list-features
33314 Returns a list of particular features of the MI protocol that
33315 this version of gdb implements. A feature can be a command,
33316 or a new field in an output of some command, or even an
33317 important bugfix. While a frontend can sometimes detect presence
33318 of a feature at runtime, it is easier to perform detection at debugger
33321 The command returns a list of strings, with each string naming an
33322 available feature. Each returned string is just a name, it does not
33323 have any internal structure. The list of possible feature names
33329 (gdb) -list-features
33330 ^done,result=["feature1","feature2"]
33333 The current list of features is:
33336 @item frozen-varobjs
33337 Indicates support for the @code{-var-set-frozen} command, as well
33338 as possible presense of the @code{frozen} field in the output
33339 of @code{-varobj-create}.
33340 @item pending-breakpoints
33341 Indicates support for the @option{-f} option to the @code{-break-insert}
33344 Indicates Python scripting support, Python-based
33345 pretty-printing commands, and possible presence of the
33346 @samp{display_hint} field in the output of @code{-var-list-children}
33348 Indicates support for the @code{-thread-info} command.
33349 @item data-read-memory-bytes
33350 Indicates support for the @code{-data-read-memory-bytes} and the
33351 @code{-data-write-memory-bytes} commands.
33352 @item breakpoint-notifications
33353 Indicates that changes to breakpoints and breakpoints created via the
33354 CLI will be announced via async records.
33355 @item ada-task-info
33356 Indicates support for the @code{-ada-task-info} command.
33359 @subheading The @code{-list-target-features} Command
33360 @findex -list-target-features
33362 Returns a list of particular features that are supported by the
33363 target. Those features affect the permitted MI commands, but
33364 unlike the features reported by the @code{-list-features} command, the
33365 features depend on which target GDB is using at the moment. Whenever
33366 a target can change, due to commands such as @code{-target-select},
33367 @code{-target-attach} or @code{-exec-run}, the list of target features
33368 may change, and the frontend should obtain it again.
33372 (gdb) -list-features
33373 ^done,result=["async"]
33376 The current list of features is:
33380 Indicates that the target is capable of asynchronous command
33381 execution, which means that @value{GDBN} will accept further commands
33382 while the target is running.
33385 Indicates that the target is capable of reverse execution.
33386 @xref{Reverse Execution}, for more information.
33390 @subheading The @code{-list-thread-groups} Command
33391 @findex -list-thread-groups
33393 @subheading Synopsis
33396 -list-thread-groups [ --available ] [ --recurse 1 ] [ @var{group} ... ]
33399 Lists thread groups (@pxref{Thread groups}). When a single thread
33400 group is passed as the argument, lists the children of that group.
33401 When several thread group are passed, lists information about those
33402 thread groups. Without any parameters, lists information about all
33403 top-level thread groups.
33405 Normally, thread groups that are being debugged are reported.
33406 With the @samp{--available} option, @value{GDBN} reports thread groups
33407 available on the target.
33409 The output of this command may have either a @samp{threads} result or
33410 a @samp{groups} result. The @samp{thread} result has a list of tuples
33411 as value, with each tuple describing a thread (@pxref{GDB/MI Thread
33412 Information}). The @samp{groups} result has a list of tuples as value,
33413 each tuple describing a thread group. If top-level groups are
33414 requested (that is, no parameter is passed), or when several groups
33415 are passed, the output always has a @samp{groups} result. The format
33416 of the @samp{group} result is described below.
33418 To reduce the number of roundtrips it's possible to list thread groups
33419 together with their children, by passing the @samp{--recurse} option
33420 and the recursion depth. Presently, only recursion depth of 1 is
33421 permitted. If this option is present, then every reported thread group
33422 will also include its children, either as @samp{group} or
33423 @samp{threads} field.
33425 In general, any combination of option and parameters is permitted, with
33426 the following caveats:
33430 When a single thread group is passed, the output will typically
33431 be the @samp{threads} result. Because threads may not contain
33432 anything, the @samp{recurse} option will be ignored.
33435 When the @samp{--available} option is passed, limited information may
33436 be available. In particular, the list of threads of a process might
33437 be inaccessible. Further, specifying specific thread groups might
33438 not give any performance advantage over listing all thread groups.
33439 The frontend should assume that @samp{-list-thread-groups --available}
33440 is always an expensive operation and cache the results.
33444 The @samp{groups} result is a list of tuples, where each tuple may
33445 have the following fields:
33449 Identifier of the thread group. This field is always present.
33450 The identifier is an opaque string; frontends should not try to
33451 convert it to an integer, even though it might look like one.
33454 The type of the thread group. At present, only @samp{process} is a
33458 The target-specific process identifier. This field is only present
33459 for thread groups of type @samp{process} and only if the process exists.
33462 The number of children this thread group has. This field may be
33463 absent for an available thread group.
33466 This field has a list of tuples as value, each tuple describing a
33467 thread. It may be present if the @samp{--recurse} option is
33468 specified, and it's actually possible to obtain the threads.
33471 This field is a list of integers, each identifying a core that one
33472 thread of the group is running on. This field may be absent if
33473 such information is not available.
33476 The name of the executable file that corresponds to this thread group.
33477 The field is only present for thread groups of type @samp{process},
33478 and only if there is a corresponding executable file.
33482 @subheading Example
33486 -list-thread-groups
33487 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2"@}]
33488 -list-thread-groups 17
33489 ^done,threads=[@{id="2",target-id="Thread 0xb7e14b90 (LWP 21257)",
33490 frame=@{level="0",addr="0xffffe410",func="__kernel_vsyscall",args=[]@},state="running"@},
33491 @{id="1",target-id="Thread 0xb7e156b0 (LWP 21254)",
33492 frame=@{level="0",addr="0x0804891f",func="foo",args=[@{name="i",value="10"@}],
33493 file="/tmp/a.c",fullname="/tmp/a.c",line="158"@},state="running"@}]]
33494 -list-thread-groups --available
33495 ^done,groups=[@{id="17",type="process",pid="yyy",num_children="2",cores=[1,2]@}]
33496 -list-thread-groups --available --recurse 1
33497 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33498 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33499 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},..]
33500 -list-thread-groups --available --recurse 1 17 18
33501 ^done,groups=[@{id="17", types="process",pid="yyy",num_children="2",cores=[1,2],
33502 threads=[@{id="1",target-id="Thread 0xb7e14b90",cores=[1]@},
33503 @{id="2",target-id="Thread 0xb7e14b90",cores=[2]@}]@},...]
33506 @subheading The @code{-info-os} Command
33509 @subsubheading Synopsis
33512 -info-os [ @var{type} ]
33515 If no argument is supplied, the command returns a table of available
33516 operating-system-specific information types. If one of these types is
33517 supplied as an argument @var{type}, then the command returns a table
33518 of data of that type.
33520 The types of information available depend on the target operating
33523 @subsubheading @value{GDBN} Command
33525 The corresponding @value{GDBN} command is @samp{info os}.
33527 @subsubheading Example
33529 When run on a @sc{gnu}/Linux system, the output will look something
33535 ^done,OSDataTable=@{nr_rows="9",nr_cols="3",
33536 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="Type"@},
33537 @{width="10",alignment="-1",col_name="col1",colhdr="Description"@},
33538 @{width="10",alignment="-1",col_name="col2",colhdr="Title"@}],
33539 body=[item=@{col0="processes",col1="Listing of all processes",
33540 col2="Processes"@},
33541 item=@{col0="procgroups",col1="Listing of all process groups",
33542 col2="Process groups"@},
33543 item=@{col0="threads",col1="Listing of all threads",
33545 item=@{col0="files",col1="Listing of all file descriptors",
33546 col2="File descriptors"@},
33547 item=@{col0="sockets",col1="Listing of all internet-domain sockets",
33549 item=@{col0="shm",col1="Listing of all shared-memory regions",
33550 col2="Shared-memory regions"@},
33551 item=@{col0="semaphores",col1="Listing of all semaphores",
33552 col2="Semaphores"@},
33553 item=@{col0="msg",col1="Listing of all message queues",
33554 col2="Message queues"@},
33555 item=@{col0="modules",col1="Listing of all loaded kernel modules",
33556 col2="Kernel modules"@}]@}
33559 ^done,OSDataTable=@{nr_rows="190",nr_cols="4",
33560 hdr=[@{width="10",alignment="-1",col_name="col0",colhdr="pid"@},
33561 @{width="10",alignment="-1",col_name="col1",colhdr="user"@},
33562 @{width="10",alignment="-1",col_name="col2",colhdr="command"@},
33563 @{width="10",alignment="-1",col_name="col3",colhdr="cores"@}],
33564 body=[item=@{col0="1",col1="root",col2="/sbin/init",col3="0"@},
33565 item=@{col0="2",col1="root",col2="[kthreadd]",col3="1"@},
33566 item=@{col0="3",col1="root",col2="[ksoftirqd/0]",col3="0"@},
33568 item=@{col0="26446",col1="stan",col2="bash",col3="0"@},
33569 item=@{col0="28152",col1="stan",col2="bash",col3="1"@}]@}
33573 (Note that the MI output here includes a @code{"Title"} column that
33574 does not appear in command-line @code{info os}; this column is useful
33575 for MI clients that want to enumerate the types of data, such as in a
33576 popup menu, but is needless clutter on the command line, and
33577 @code{info os} omits it.)
33579 @subheading The @code{-add-inferior} Command
33580 @findex -add-inferior
33582 @subheading Synopsis
33588 Creates a new inferior (@pxref{Inferiors and Programs}). The created
33589 inferior is not associated with any executable. Such association may
33590 be established with the @samp{-file-exec-and-symbols} command
33591 (@pxref{GDB/MI File Commands}). The command response has a single
33592 field, @samp{thread-group}, whose value is the identifier of the
33593 thread group corresponding to the new inferior.
33595 @subheading Example
33600 ^done,thread-group="i3"
33603 @subheading The @code{-interpreter-exec} Command
33604 @findex -interpreter-exec
33606 @subheading Synopsis
33609 -interpreter-exec @var{interpreter} @var{command}
33611 @anchor{-interpreter-exec}
33613 Execute the specified @var{command} in the given @var{interpreter}.
33615 @subheading @value{GDBN} Command
33617 The corresponding @value{GDBN} command is @samp{interpreter-exec}.
33619 @subheading Example
33623 -interpreter-exec console "break main"
33624 &"During symbol reading, couldn't parse type; debugger out of date?.\n"
33625 &"During symbol reading, bad structure-type format.\n"
33626 ~"Breakpoint 1 at 0x8074fc6: file ../../src/gdb/main.c, line 743.\n"
33631 @subheading The @code{-inferior-tty-set} Command
33632 @findex -inferior-tty-set
33634 @subheading Synopsis
33637 -inferior-tty-set /dev/pts/1
33640 Set terminal for future runs of the program being debugged.
33642 @subheading @value{GDBN} Command
33644 The corresponding @value{GDBN} command is @samp{set inferior-tty} /dev/pts/1.
33646 @subheading Example
33650 -inferior-tty-set /dev/pts/1
33655 @subheading The @code{-inferior-tty-show} Command
33656 @findex -inferior-tty-show
33658 @subheading Synopsis
33664 Show terminal for future runs of program being debugged.
33666 @subheading @value{GDBN} Command
33668 The corresponding @value{GDBN} command is @samp{show inferior-tty}.
33670 @subheading Example
33674 -inferior-tty-set /dev/pts/1
33678 ^done,inferior_tty_terminal="/dev/pts/1"
33682 @subheading The @code{-enable-timings} Command
33683 @findex -enable-timings
33685 @subheading Synopsis
33688 -enable-timings [yes | no]
33691 Toggle the printing of the wallclock, user and system times for an MI
33692 command as a field in its output. This command is to help frontend
33693 developers optimize the performance of their code. No argument is
33694 equivalent to @samp{yes}.
33696 @subheading @value{GDBN} Command
33700 @subheading Example
33708 ^done,bkpt=@{number="1",type="breakpoint",disp="keep",enabled="y",
33709 addr="0x080484ed",func="main",file="myprog.c",
33710 fullname="/home/nickrob/myprog.c",line="73",thread-groups=["i1"],
33712 time=@{wallclock="0.05185",user="0.00800",system="0.00000"@}
33720 *stopped,reason="breakpoint-hit",disp="keep",bkptno="1",thread-id="0",
33721 frame=@{addr="0x080484ed",func="main",args=[@{name="argc",value="1"@},
33722 @{name="argv",value="0xbfb60364"@}],file="myprog.c",
33723 fullname="/home/nickrob/myprog.c",line="73"@}
33728 @chapter @value{GDBN} Annotations
33730 This chapter describes annotations in @value{GDBN}. Annotations were
33731 designed to interface @value{GDBN} to graphical user interfaces or other
33732 similar programs which want to interact with @value{GDBN} at a
33733 relatively high level.
33735 The annotation mechanism has largely been superseded by @sc{gdb/mi}
33739 This is Edition @value{EDITION}, @value{DATE}.
33743 * Annotations Overview:: What annotations are; the general syntax.
33744 * Server Prefix:: Issuing a command without affecting user state.
33745 * Prompting:: Annotations marking @value{GDBN}'s need for input.
33746 * Errors:: Annotations for error messages.
33747 * Invalidation:: Some annotations describe things now invalid.
33748 * Annotations for Running::
33749 Whether the program is running, how it stopped, etc.
33750 * Source Annotations:: Annotations describing source code.
33753 @node Annotations Overview
33754 @section What is an Annotation?
33755 @cindex annotations
33757 Annotations start with a newline character, two @samp{control-z}
33758 characters, and the name of the annotation. If there is no additional
33759 information associated with this annotation, the name of the annotation
33760 is followed immediately by a newline. If there is additional
33761 information, the name of the annotation is followed by a space, the
33762 additional information, and a newline. The additional information
33763 cannot contain newline characters.
33765 Any output not beginning with a newline and two @samp{control-z}
33766 characters denotes literal output from @value{GDBN}. Currently there is
33767 no need for @value{GDBN} to output a newline followed by two
33768 @samp{control-z} characters, but if there was such a need, the
33769 annotations could be extended with an @samp{escape} annotation which
33770 means those three characters as output.
33772 The annotation @var{level}, which is specified using the
33773 @option{--annotate} command line option (@pxref{Mode Options}), controls
33774 how much information @value{GDBN} prints together with its prompt,
33775 values of expressions, source lines, and other types of output. Level 0
33776 is for no annotations, level 1 is for use when @value{GDBN} is run as a
33777 subprocess of @sc{gnu} Emacs, level 3 is the maximum annotation suitable
33778 for programs that control @value{GDBN}, and level 2 annotations have
33779 been made obsolete (@pxref{Limitations, , Limitations of the Annotation
33780 Interface, annotate, GDB's Obsolete Annotations}).
33783 @kindex set annotate
33784 @item set annotate @var{level}
33785 The @value{GDBN} command @code{set annotate} sets the level of
33786 annotations to the specified @var{level}.
33788 @item show annotate
33789 @kindex show annotate
33790 Show the current annotation level.
33793 This chapter describes level 3 annotations.
33795 A simple example of starting up @value{GDBN} with annotations is:
33798 $ @kbd{gdb --annotate=3}
33800 Copyright 2003 Free Software Foundation, Inc.
33801 GDB is free software, covered by the GNU General Public License,
33802 and you are welcome to change it and/or distribute copies of it
33803 under certain conditions.
33804 Type "show copying" to see the conditions.
33805 There is absolutely no warranty for GDB. Type "show warranty"
33807 This GDB was configured as "i386-pc-linux-gnu"
33818 Here @samp{quit} is input to @value{GDBN}; the rest is output from
33819 @value{GDBN}. The three lines beginning @samp{^Z^Z} (where @samp{^Z}
33820 denotes a @samp{control-z} character) are annotations; the rest is
33821 output from @value{GDBN}.
33823 @node Server Prefix
33824 @section The Server Prefix
33825 @cindex server prefix
33827 If you prefix a command with @samp{server } then it will not affect
33828 the command history, nor will it affect @value{GDBN}'s notion of which
33829 command to repeat if @key{RET} is pressed on a line by itself. This
33830 means that commands can be run behind a user's back by a front-end in
33831 a transparent manner.
33833 The @code{server } prefix does not affect the recording of values into
33834 the value history; to print a value without recording it into the
33835 value history, use the @code{output} command instead of the
33836 @code{print} command.
33838 Using this prefix also disables confirmation requests
33839 (@pxref{confirmation requests}).
33842 @section Annotation for @value{GDBN} Input
33844 @cindex annotations for prompts
33845 When @value{GDBN} prompts for input, it annotates this fact so it is possible
33846 to know when to send output, when the output from a given command is
33849 Different kinds of input each have a different @dfn{input type}. Each
33850 input type has three annotations: a @code{pre-} annotation, which
33851 denotes the beginning of any prompt which is being output, a plain
33852 annotation, which denotes the end of the prompt, and then a @code{post-}
33853 annotation which denotes the end of any echo which may (or may not) be
33854 associated with the input. For example, the @code{prompt} input type
33855 features the following annotations:
33863 The input types are
33866 @findex pre-prompt annotation
33867 @findex prompt annotation
33868 @findex post-prompt annotation
33870 When @value{GDBN} is prompting for a command (the main @value{GDBN} prompt).
33872 @findex pre-commands annotation
33873 @findex commands annotation
33874 @findex post-commands annotation
33876 When @value{GDBN} prompts for a set of commands, like in the @code{commands}
33877 command. The annotations are repeated for each command which is input.
33879 @findex pre-overload-choice annotation
33880 @findex overload-choice annotation
33881 @findex post-overload-choice annotation
33882 @item overload-choice
33883 When @value{GDBN} wants the user to select between various overloaded functions.
33885 @findex pre-query annotation
33886 @findex query annotation
33887 @findex post-query annotation
33889 When @value{GDBN} wants the user to confirm a potentially dangerous operation.
33891 @findex pre-prompt-for-continue annotation
33892 @findex prompt-for-continue annotation
33893 @findex post-prompt-for-continue annotation
33894 @item prompt-for-continue
33895 When @value{GDBN} is asking the user to press return to continue. Note: Don't
33896 expect this to work well; instead use @code{set height 0} to disable
33897 prompting. This is because the counting of lines is buggy in the
33898 presence of annotations.
33903 @cindex annotations for errors, warnings and interrupts
33905 @findex quit annotation
33910 This annotation occurs right before @value{GDBN} responds to an interrupt.
33912 @findex error annotation
33917 This annotation occurs right before @value{GDBN} responds to an error.
33919 Quit and error annotations indicate that any annotations which @value{GDBN} was
33920 in the middle of may end abruptly. For example, if a
33921 @code{value-history-begin} annotation is followed by a @code{error}, one
33922 cannot expect to receive the matching @code{value-history-end}. One
33923 cannot expect not to receive it either, however; an error annotation
33924 does not necessarily mean that @value{GDBN} is immediately returning all the way
33927 @findex error-begin annotation
33928 A quit or error annotation may be preceded by
33934 Any output between that and the quit or error annotation is the error
33937 Warning messages are not yet annotated.
33938 @c If we want to change that, need to fix warning(), type_error(),
33939 @c range_error(), and possibly other places.
33942 @section Invalidation Notices
33944 @cindex annotations for invalidation messages
33945 The following annotations say that certain pieces of state may have
33949 @findex frames-invalid annotation
33950 @item ^Z^Zframes-invalid
33952 The frames (for example, output from the @code{backtrace} command) may
33955 @findex breakpoints-invalid annotation
33956 @item ^Z^Zbreakpoints-invalid
33958 The breakpoints may have changed. For example, the user just added or
33959 deleted a breakpoint.
33962 @node Annotations for Running
33963 @section Running the Program
33964 @cindex annotations for running programs
33966 @findex starting annotation
33967 @findex stopping annotation
33968 When the program starts executing due to a @value{GDBN} command such as
33969 @code{step} or @code{continue},
33975 is output. When the program stops,
33981 is output. Before the @code{stopped} annotation, a variety of
33982 annotations describe how the program stopped.
33985 @findex exited annotation
33986 @item ^Z^Zexited @var{exit-status}
33987 The program exited, and @var{exit-status} is the exit status (zero for
33988 successful exit, otherwise nonzero).
33990 @findex signalled annotation
33991 @findex signal-name annotation
33992 @findex signal-name-end annotation
33993 @findex signal-string annotation
33994 @findex signal-string-end annotation
33995 @item ^Z^Zsignalled
33996 The program exited with a signal. After the @code{^Z^Zsignalled}, the
33997 annotation continues:
34003 ^Z^Zsignal-name-end
34007 ^Z^Zsignal-string-end
34012 where @var{name} is the name of the signal, such as @code{SIGILL} or
34013 @code{SIGSEGV}, and @var{string} is the explanation of the signal, such
34014 as @code{Illegal Instruction} or @code{Segmentation fault}.
34015 @var{intro-text}, @var{middle-text}, and @var{end-text} are for the
34016 user's benefit and have no particular format.
34018 @findex signal annotation
34020 The syntax of this annotation is just like @code{signalled}, but @value{GDBN} is
34021 just saying that the program received the signal, not that it was
34022 terminated with it.
34024 @findex breakpoint annotation
34025 @item ^Z^Zbreakpoint @var{number}
34026 The program hit breakpoint number @var{number}.
34028 @findex watchpoint annotation
34029 @item ^Z^Zwatchpoint @var{number}
34030 The program hit watchpoint number @var{number}.
34033 @node Source Annotations
34034 @section Displaying Source
34035 @cindex annotations for source display
34037 @findex source annotation
34038 The following annotation is used instead of displaying source code:
34041 ^Z^Zsource @var{filename}:@var{line}:@var{character}:@var{middle}:@var{addr}
34044 where @var{filename} is an absolute file name indicating which source
34045 file, @var{line} is the line number within that file (where 1 is the
34046 first line in the file), @var{character} is the character position
34047 within the file (where 0 is the first character in the file) (for most
34048 debug formats this will necessarily point to the beginning of a line),
34049 @var{middle} is @samp{middle} if @var{addr} is in the middle of the
34050 line, or @samp{beg} if @var{addr} is at the beginning of the line, and
34051 @var{addr} is the address in the target program associated with the
34052 source which is being displayed. @var{addr} is in the form @samp{0x}
34053 followed by one or more lowercase hex digits (note that this does not
34054 depend on the language).
34056 @node JIT Interface
34057 @chapter JIT Compilation Interface
34058 @cindex just-in-time compilation
34059 @cindex JIT compilation interface
34061 This chapter documents @value{GDBN}'s @dfn{just-in-time} (JIT) compilation
34062 interface. A JIT compiler is a program or library that generates native
34063 executable code at runtime and executes it, usually in order to achieve good
34064 performance while maintaining platform independence.
34066 Programs that use JIT compilation are normally difficult to debug because
34067 portions of their code are generated at runtime, instead of being loaded from
34068 object files, which is where @value{GDBN} normally finds the program's symbols
34069 and debug information. In order to debug programs that use JIT compilation,
34070 @value{GDBN} has an interface that allows the program to register in-memory
34071 symbol files with @value{GDBN} at runtime.
34073 If you are using @value{GDBN} to debug a program that uses this interface, then
34074 it should work transparently so long as you have not stripped the binary. If
34075 you are developing a JIT compiler, then the interface is documented in the rest
34076 of this chapter. At this time, the only known client of this interface is the
34079 Broadly speaking, the JIT interface mirrors the dynamic loader interface. The
34080 JIT compiler communicates with @value{GDBN} by writing data into a global
34081 variable and calling a fuction at a well-known symbol. When @value{GDBN}
34082 attaches, it reads a linked list of symbol files from the global variable to
34083 find existing code, and puts a breakpoint in the function so that it can find
34084 out about additional code.
34087 * Declarations:: Relevant C struct declarations
34088 * Registering Code:: Steps to register code
34089 * Unregistering Code:: Steps to unregister code
34090 * Custom Debug Info:: Emit debug information in a custom format
34094 @section JIT Declarations
34096 These are the relevant struct declarations that a C program should include to
34097 implement the interface:
34107 struct jit_code_entry
34109 struct jit_code_entry *next_entry;
34110 struct jit_code_entry *prev_entry;
34111 const char *symfile_addr;
34112 uint64_t symfile_size;
34115 struct jit_descriptor
34118 /* This type should be jit_actions_t, but we use uint32_t
34119 to be explicit about the bitwidth. */
34120 uint32_t action_flag;
34121 struct jit_code_entry *relevant_entry;
34122 struct jit_code_entry *first_entry;
34125 /* GDB puts a breakpoint in this function. */
34126 void __attribute__((noinline)) __jit_debug_register_code() @{ @};
34128 /* Make sure to specify the version statically, because the
34129 debugger may check the version before we can set it. */
34130 struct jit_descriptor __jit_debug_descriptor = @{ 1, 0, 0, 0 @};
34133 If the JIT is multi-threaded, then it is important that the JIT synchronize any
34134 modifications to this global data properly, which can easily be done by putting
34135 a global mutex around modifications to these structures.
34137 @node Registering Code
34138 @section Registering Code
34140 To register code with @value{GDBN}, the JIT should follow this protocol:
34144 Generate an object file in memory with symbols and other desired debug
34145 information. The file must include the virtual addresses of the sections.
34148 Create a code entry for the file, which gives the start and size of the symbol
34152 Add it to the linked list in the JIT descriptor.
34155 Point the relevant_entry field of the descriptor at the entry.
34158 Set @code{action_flag} to @code{JIT_REGISTER} and call
34159 @code{__jit_debug_register_code}.
34162 When @value{GDBN} is attached and the breakpoint fires, @value{GDBN} uses the
34163 @code{relevant_entry} pointer so it doesn't have to walk the list looking for
34164 new code. However, the linked list must still be maintained in order to allow
34165 @value{GDBN} to attach to a running process and still find the symbol files.
34167 @node Unregistering Code
34168 @section Unregistering Code
34170 If code is freed, then the JIT should use the following protocol:
34174 Remove the code entry corresponding to the code from the linked list.
34177 Point the @code{relevant_entry} field of the descriptor at the code entry.
34180 Set @code{action_flag} to @code{JIT_UNREGISTER} and call
34181 @code{__jit_debug_register_code}.
34184 If the JIT frees or recompiles code without unregistering it, then @value{GDBN}
34185 and the JIT will leak the memory used for the associated symbol files.
34187 @node Custom Debug Info
34188 @section Custom Debug Info
34189 @cindex custom JIT debug info
34190 @cindex JIT debug info reader
34192 Generating debug information in platform-native file formats (like ELF
34193 or COFF) may be an overkill for JIT compilers; especially if all the
34194 debug info is used for is displaying a meaningful backtrace. The
34195 issue can be resolved by having the JIT writers decide on a debug info
34196 format and also provide a reader that parses the debug info generated
34197 by the JIT compiler. This section gives a brief overview on writing
34198 such a parser. More specific details can be found in the source file
34199 @file{gdb/jit-reader.in}, which is also installed as a header at
34200 @file{@var{includedir}/gdb/jit-reader.h} for easy inclusion.
34202 The reader is implemented as a shared object (so this functionality is
34203 not available on platforms which don't allow loading shared objects at
34204 runtime). Two @value{GDBN} commands, @code{jit-reader-load} and
34205 @code{jit-reader-unload} are provided, to be used to load and unload
34206 the readers from a preconfigured directory. Once loaded, the shared
34207 object is used the parse the debug information emitted by the JIT
34211 * Using JIT Debug Info Readers:: How to use supplied readers correctly
34212 * Writing JIT Debug Info Readers:: Creating a debug-info reader
34215 @node Using JIT Debug Info Readers
34216 @subsection Using JIT Debug Info Readers
34217 @kindex jit-reader-load
34218 @kindex jit-reader-unload
34220 Readers can be loaded and unloaded using the @code{jit-reader-load}
34221 and @code{jit-reader-unload} commands.
34224 @item jit-reader-load @var{reader}
34225 Load the JIT reader named @var{reader}. @var{reader} is a shared
34226 object specified as either an absolute or a relative file name. In
34227 the latter case, @value{GDBN} will try to load the reader from a
34228 pre-configured directory, usually @file{@var{libdir}/gdb/} on a UNIX
34229 system (here @var{libdir} is the system library directory, often
34230 @file{/usr/local/lib}).
34232 Only one reader can be active at a time; trying to load a second
34233 reader when one is already loaded will result in @value{GDBN}
34234 reporting an error. A new JIT reader can be loaded by first unloading
34235 the current one using @code{jit-reader-unload} and then invoking
34236 @code{jit-reader-load}.
34238 @item jit-reader-unload
34239 Unload the currently loaded JIT reader.
34243 @node Writing JIT Debug Info Readers
34244 @subsection Writing JIT Debug Info Readers
34245 @cindex writing JIT debug info readers
34247 As mentioned, a reader is essentially a shared object conforming to a
34248 certain ABI. This ABI is described in @file{jit-reader.h}.
34250 @file{jit-reader.h} defines the structures, macros and functions
34251 required to write a reader. It is installed (along with
34252 @value{GDBN}), in @file{@var{includedir}/gdb} where @var{includedir} is
34253 the system include directory.
34255 Readers need to be released under a GPL compatible license. A reader
34256 can be declared as released under such a license by placing the macro
34257 @code{GDB_DECLARE_GPL_COMPATIBLE_READER} in a source file.
34259 The entry point for readers is the symbol @code{gdb_init_reader},
34260 which is expected to be a function with the prototype
34262 @findex gdb_init_reader
34264 extern struct gdb_reader_funcs *gdb_init_reader (void);
34267 @cindex @code{struct gdb_reader_funcs}
34269 @code{struct gdb_reader_funcs} contains a set of pointers to callback
34270 functions. These functions are executed to read the debug info
34271 generated by the JIT compiler (@code{read}), to unwind stack frames
34272 (@code{unwind}) and to create canonical frame IDs
34273 (@code{get_Frame_id}). It also has a callback that is called when the
34274 reader is being unloaded (@code{destroy}). The struct looks like this
34277 struct gdb_reader_funcs
34279 /* Must be set to GDB_READER_INTERFACE_VERSION. */
34280 int reader_version;
34282 /* For use by the reader. */
34285 gdb_read_debug_info *read;
34286 gdb_unwind_frame *unwind;
34287 gdb_get_frame_id *get_frame_id;
34288 gdb_destroy_reader *destroy;
34292 @cindex @code{struct gdb_symbol_callbacks}
34293 @cindex @code{struct gdb_unwind_callbacks}
34295 The callbacks are provided with another set of callbacks by
34296 @value{GDBN} to do their job. For @code{read}, these callbacks are
34297 passed in a @code{struct gdb_symbol_callbacks} and for @code{unwind}
34298 and @code{get_frame_id}, in a @code{struct gdb_unwind_callbacks}.
34299 @code{struct gdb_symbol_callbacks} has callbacks to create new object
34300 files and new symbol tables inside those object files. @code{struct
34301 gdb_unwind_callbacks} has callbacks to read registers off the current
34302 frame and to write out the values of the registers in the previous
34303 frame. Both have a callback (@code{target_read}) to read bytes off the
34304 target's address space.
34306 @node In-Process Agent
34307 @chapter In-Process Agent
34308 @cindex debugging agent
34309 The traditional debugging model is conceptually low-speed, but works fine,
34310 because most bugs can be reproduced in debugging-mode execution. However,
34311 as multi-core or many-core processors are becoming mainstream, and
34312 multi-threaded programs become more and more popular, there should be more
34313 and more bugs that only manifest themselves at normal-mode execution, for
34314 example, thread races, because debugger's interference with the program's
34315 timing may conceal the bugs. On the other hand, in some applications,
34316 it is not feasible for the debugger to interrupt the program's execution
34317 long enough for the developer to learn anything helpful about its behavior.
34318 If the program's correctness depends on its real-time behavior, delays
34319 introduced by a debugger might cause the program to fail, even when the
34320 code itself is correct. It is useful to be able to observe the program's
34321 behavior without interrupting it.
34323 Therefore, traditional debugging model is too intrusive to reproduce
34324 some bugs. In order to reduce the interference with the program, we can
34325 reduce the number of operations performed by debugger. The
34326 @dfn{In-Process Agent}, a shared library, is running within the same
34327 process with inferior, and is able to perform some debugging operations
34328 itself. As a result, debugger is only involved when necessary, and
34329 performance of debugging can be improved accordingly. Note that
34330 interference with program can be reduced but can't be removed completely,
34331 because the in-process agent will still stop or slow down the program.
34333 The in-process agent can interpret and execute Agent Expressions
34334 (@pxref{Agent Expressions}) during performing debugging operations. The
34335 agent expressions can be used for different purposes, such as collecting
34336 data in tracepoints, and condition evaluation in breakpoints.
34338 @anchor{Control Agent}
34339 You can control whether the in-process agent is used as an aid for
34340 debugging with the following commands:
34343 @kindex set agent on
34345 Causes the in-process agent to perform some operations on behalf of the
34346 debugger. Just which operations requested by the user will be done
34347 by the in-process agent depends on the its capabilities. For example,
34348 if you request to evaluate breakpoint conditions in the in-process agent,
34349 and the in-process agent has such capability as well, then breakpoint
34350 conditions will be evaluated in the in-process agent.
34352 @kindex set agent off
34353 @item set agent off
34354 Disables execution of debugging operations by the in-process agent. All
34355 of the operations will be performed by @value{GDBN}.
34359 Display the current setting of execution of debugging operations by
34360 the in-process agent.
34364 * In-Process Agent Protocol::
34367 @node In-Process Agent Protocol
34368 @section In-Process Agent Protocol
34369 @cindex in-process agent protocol
34371 The in-process agent is able to communicate with both @value{GDBN} and
34372 GDBserver (@pxref{In-Process Agent}). This section documents the protocol
34373 used for communications between @value{GDBN} or GDBserver and the IPA.
34374 In general, @value{GDBN} or GDBserver sends commands
34375 (@pxref{IPA Protocol Commands}) and data to in-process agent, and then
34376 in-process agent replies back with the return result of the command, or
34377 some other information. The data sent to in-process agent is composed
34378 of primitive data types, such as 4-byte or 8-byte type, and composite
34379 types, which are called objects (@pxref{IPA Protocol Objects}).
34382 * IPA Protocol Objects::
34383 * IPA Protocol Commands::
34386 @node IPA Protocol Objects
34387 @subsection IPA Protocol Objects
34388 @cindex ipa protocol objects
34390 The commands sent to and results received from agent may contain some
34391 complex data types called @dfn{objects}.
34393 The in-process agent is running on the same machine with @value{GDBN}
34394 or GDBserver, so it doesn't have to handle as much differences between
34395 two ends as remote protocol (@pxref{Remote Protocol}) tries to handle.
34396 However, there are still some differences of two ends in two processes:
34400 word size. On some 64-bit machines, @value{GDBN} or GDBserver can be
34401 compiled as a 64-bit executable, while in-process agent is a 32-bit one.
34403 ABI. Some machines may have multiple types of ABI, @value{GDBN} or
34404 GDBserver is compiled with one, and in-process agent is compiled with
34408 Here are the IPA Protocol Objects:
34412 agent expression object. It represents an agent expression
34413 (@pxref{Agent Expressions}).
34414 @anchor{agent expression object}
34416 tracepoint action object. It represents a tracepoint action
34417 (@pxref{Tracepoint Actions,,Tracepoint Action Lists}) to collect registers,
34418 memory, static trace data and to evaluate expression.
34419 @anchor{tracepoint action object}
34421 tracepoint object. It represents a tracepoint (@pxref{Tracepoints}).
34422 @anchor{tracepoint object}
34426 The following table describes important attributes of each IPA protocol
34429 @multitable @columnfractions .30 .20 .50
34430 @headitem Name @tab Size @tab Description
34431 @item @emph{agent expression object} @tab @tab
34432 @item length @tab 4 @tab length of bytes code
34433 @item byte code @tab @var{length} @tab contents of byte code
34434 @item @emph{tracepoint action for collecting memory} @tab @tab
34435 @item 'M' @tab 1 @tab type of tracepoint action
34436 @item addr @tab 8 @tab if @var{basereg} is @samp{-1}, @var{addr} is the
34437 address of the lowest byte to collect, otherwise @var{addr} is the offset
34438 of @var{basereg} for memory collecting.
34439 @item len @tab 8 @tab length of memory for collecting
34440 @item basereg @tab 4 @tab the register number containing the starting
34441 memory address for collecting.
34442 @item @emph{tracepoint action for collecting registers} @tab @tab
34443 @item 'R' @tab 1 @tab type of tracepoint action
34444 @item @emph{tracepoint action for collecting static trace data} @tab @tab
34445 @item 'L' @tab 1 @tab type of tracepoint action
34446 @item @emph{tracepoint action for expression evaluation} @tab @tab
34447 @item 'X' @tab 1 @tab type of tracepoint action
34448 @item agent expression @tab length of @tab @ref{agent expression object}
34449 @item @emph{tracepoint object} @tab @tab
34450 @item number @tab 4 @tab number of tracepoint
34451 @item address @tab 8 @tab address of tracepoint inserted on
34452 @item type @tab 4 @tab type of tracepoint
34453 @item enabled @tab 1 @tab enable or disable of tracepoint
34454 @item step_count @tab 8 @tab step
34455 @item pass_count @tab 8 @tab pass
34456 @item numactions @tab 4 @tab number of tracepoint actions
34457 @item hit count @tab 8 @tab hit count
34458 @item trace frame usage @tab 8 @tab trace frame usage
34459 @item compiled_cond @tab 8 @tab compiled condition
34460 @item orig_size @tab 8 @tab orig size
34461 @item condition @tab 4 if condition is NULL otherwise length of
34462 @ref{agent expression object}
34463 @tab zero if condition is NULL, otherwise is
34464 @ref{agent expression object}
34465 @item actions @tab variable
34466 @tab numactions number of @ref{tracepoint action object}
34469 @node IPA Protocol Commands
34470 @subsection IPA Protocol Commands
34471 @cindex ipa protocol commands
34473 The spaces in each command are delimiters to ease reading this commands
34474 specification. They don't exist in real commands.
34478 @item FastTrace:@var{tracepoint_object} @var{gdb_jump_pad_head}
34479 Installs a new fast tracepoint described by @var{tracepoint_object}
34480 (@pxref{tracepoint object}). @var{gdb_jump_pad_head}, 8-byte long, is the
34481 head of @dfn{jumppad}, which is used to jump to data collection routine
34486 @item OK @var{target_address} @var{gdb_jump_pad_head} @var{fjump_size} @var{fjump}
34487 @var{target_address} is address of tracepoint in the inferior.
34488 @var{gdb_jump_pad_head} is updated head of jumppad. Both of
34489 @var{target_address} and @var{gdb_jump_pad_head} are 8-byte long.
34490 @var{fjump} contains a sequence of instructions jump to jumppad entry.
34491 @var{fjump_size}, 4-byte long, is the size of @var{fjump}.
34498 Closes the in-process agent. This command is sent when @value{GDBN} or GDBserver
34499 is about to kill inferiors.
34507 @item probe_marker_at:@var{address}
34508 Asks in-process agent to probe the marker at @var{address}.
34515 @item unprobe_marker_at:@var{address}
34516 Asks in-process agent to unprobe the marker at @var{address}.
34520 @chapter Reporting Bugs in @value{GDBN}
34521 @cindex bugs in @value{GDBN}
34522 @cindex reporting bugs in @value{GDBN}
34524 Your bug reports play an essential role in making @value{GDBN} reliable.
34526 Reporting a bug may help you by bringing a solution to your problem, or it
34527 may not. But in any case the principal function of a bug report is to help
34528 the entire community by making the next version of @value{GDBN} work better. Bug
34529 reports are your contribution to the maintenance of @value{GDBN}.
34531 In order for a bug report to serve its purpose, you must include the
34532 information that enables us to fix the bug.
34535 * Bug Criteria:: Have you found a bug?
34536 * Bug Reporting:: How to report bugs
34540 @section Have You Found a Bug?
34541 @cindex bug criteria
34543 If you are not sure whether you have found a bug, here are some guidelines:
34546 @cindex fatal signal
34547 @cindex debugger crash
34548 @cindex crash of debugger
34550 If the debugger gets a fatal signal, for any input whatever, that is a
34551 @value{GDBN} bug. Reliable debuggers never crash.
34553 @cindex error on valid input
34555 If @value{GDBN} produces an error message for valid input, that is a
34556 bug. (Note that if you're cross debugging, the problem may also be
34557 somewhere in the connection to the target.)
34559 @cindex invalid input
34561 If @value{GDBN} does not produce an error message for invalid input,
34562 that is a bug. However, you should note that your idea of
34563 ``invalid input'' might be our idea of ``an extension'' or ``support
34564 for traditional practice''.
34567 If you are an experienced user of debugging tools, your suggestions
34568 for improvement of @value{GDBN} are welcome in any case.
34571 @node Bug Reporting
34572 @section How to Report Bugs
34573 @cindex bug reports
34574 @cindex @value{GDBN} bugs, reporting
34576 A number of companies and individuals offer support for @sc{gnu} products.
34577 If you obtained @value{GDBN} from a support organization, we recommend you
34578 contact that organization first.
34580 You can find contact information for many support companies and
34581 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
34583 @c should add a web page ref...
34586 @ifset BUGURL_DEFAULT
34587 In any event, we also recommend that you submit bug reports for
34588 @value{GDBN}. The preferred method is to submit them directly using
34589 @uref{http://www.gnu.org/software/gdb/bugs/, @value{GDBN}'s Bugs web
34590 page}. Alternatively, the @email{bug-gdb@@gnu.org, e-mail gateway} can
34593 @strong{Do not send bug reports to @samp{info-gdb}, or to
34594 @samp{help-gdb}, or to any newsgroups.} Most users of @value{GDBN} do
34595 not want to receive bug reports. Those that do have arranged to receive
34598 The mailing list @samp{bug-gdb} has a newsgroup @samp{gnu.gdb.bug} which
34599 serves as a repeater. The mailing list and the newsgroup carry exactly
34600 the same messages. Often people think of posting bug reports to the
34601 newsgroup instead of mailing them. This appears to work, but it has one
34602 problem which can be crucial: a newsgroup posting often lacks a mail
34603 path back to the sender. Thus, if we need to ask for more information,
34604 we may be unable to reach you. For this reason, it is better to send
34605 bug reports to the mailing list.
34607 @ifclear BUGURL_DEFAULT
34608 In any event, we also recommend that you submit bug reports for
34609 @value{GDBN} to @value{BUGURL}.
34613 The fundamental principle of reporting bugs usefully is this:
34614 @strong{report all the facts}. If you are not sure whether to state a
34615 fact or leave it out, state it!
34617 Often people omit facts because they think they know what causes the
34618 problem and assume that some details do not matter. Thus, you might
34619 assume that the name of the variable you use in an example does not matter.
34620 Well, probably it does not, but one cannot be sure. Perhaps the bug is a
34621 stray memory reference which happens to fetch from the location where that
34622 name is stored in memory; perhaps, if the name were different, the contents
34623 of that location would fool the debugger into doing the right thing despite
34624 the bug. Play it safe and give a specific, complete example. That is the
34625 easiest thing for you to do, and the most helpful.
34627 Keep in mind that the purpose of a bug report is to enable us to fix the
34628 bug. It may be that the bug has been reported previously, but neither
34629 you nor we can know that unless your bug report is complete and
34632 Sometimes people give a few sketchy facts and ask, ``Does this ring a
34633 bell?'' Those bug reports are useless, and we urge everyone to
34634 @emph{refuse to respond to them} except to chide the sender to report
34637 To enable us to fix the bug, you should include all these things:
34641 The version of @value{GDBN}. @value{GDBN} announces it if you start
34642 with no arguments; you can also print it at any time using @code{show
34645 Without this, we will not know whether there is any point in looking for
34646 the bug in the current version of @value{GDBN}.
34649 The type of machine you are using, and the operating system name and
34653 What compiler (and its version) was used to compile @value{GDBN}---e.g.@:
34654 ``@value{GCC}--2.8.1''.
34657 What compiler (and its version) was used to compile the program you are
34658 debugging---e.g.@: ``@value{GCC}--2.8.1'', or ``HP92453-01 A.10.32.03 HP
34659 C Compiler''. For @value{NGCC}, you can say @kbd{@value{GCC} --version}
34660 to get this information; for other compilers, see the documentation for
34664 The command arguments you gave the compiler to compile your example and
34665 observe the bug. For example, did you use @samp{-O}? To guarantee
34666 you will not omit something important, list them all. A copy of the
34667 Makefile (or the output from make) is sufficient.
34669 If we were to try to guess the arguments, we would probably guess wrong
34670 and then we might not encounter the bug.
34673 A complete input script, and all necessary source files, that will
34677 A description of what behavior you observe that you believe is
34678 incorrect. For example, ``It gets a fatal signal.''
34680 Of course, if the bug is that @value{GDBN} gets a fatal signal, then we
34681 will certainly notice it. But if the bug is incorrect output, we might
34682 not notice unless it is glaringly wrong. You might as well not give us
34683 a chance to make a mistake.
34685 Even if the problem you experience is a fatal signal, you should still
34686 say so explicitly. Suppose something strange is going on, such as, your
34687 copy of @value{GDBN} is out of synch, or you have encountered a bug in
34688 the C library on your system. (This has happened!) Your copy might
34689 crash and ours would not. If you told us to expect a crash, then when
34690 ours fails to crash, we would know that the bug was not happening for
34691 us. If you had not told us to expect a crash, then we would not be able
34692 to draw any conclusion from our observations.
34695 @cindex recording a session script
34696 To collect all this information, you can use a session recording program
34697 such as @command{script}, which is available on many Unix systems.
34698 Just run your @value{GDBN} session inside @command{script} and then
34699 include the @file{typescript} file with your bug report.
34701 Another way to record a @value{GDBN} session is to run @value{GDBN}
34702 inside Emacs and then save the entire buffer to a file.
34705 If you wish to suggest changes to the @value{GDBN} source, send us context
34706 diffs. If you even discuss something in the @value{GDBN} source, refer to
34707 it by context, not by line number.
34709 The line numbers in our development sources will not match those in your
34710 sources. Your line numbers would convey no useful information to us.
34714 Here are some things that are not necessary:
34718 A description of the envelope of the bug.
34720 Often people who encounter a bug spend a lot of time investigating
34721 which changes to the input file will make the bug go away and which
34722 changes will not affect it.
34724 This is often time consuming and not very useful, because the way we
34725 will find the bug is by running a single example under the debugger
34726 with breakpoints, not by pure deduction from a series of examples.
34727 We recommend that you save your time for something else.
34729 Of course, if you can find a simpler example to report @emph{instead}
34730 of the original one, that is a convenience for us. Errors in the
34731 output will be easier to spot, running under the debugger will take
34732 less time, and so on.
34734 However, simplification is not vital; if you do not want to do this,
34735 report the bug anyway and send us the entire test case you used.
34738 A patch for the bug.
34740 A patch for the bug does help us if it is a good one. But do not omit
34741 the necessary information, such as the test case, on the assumption that
34742 a patch is all we need. We might see problems with your patch and decide
34743 to fix the problem another way, or we might not understand it at all.
34745 Sometimes with a program as complicated as @value{GDBN} it is very hard to
34746 construct an example that will make the program follow a certain path
34747 through the code. If you do not send us the example, we will not be able
34748 to construct one, so we will not be able to verify that the bug is fixed.
34750 And if we cannot understand what bug you are trying to fix, or why your
34751 patch should be an improvement, we will not install it. A test case will
34752 help us to understand.
34755 A guess about what the bug is or what it depends on.
34757 Such guesses are usually wrong. Even we cannot guess right about such
34758 things without first using the debugger to find the facts.
34761 @c The readline documentation is distributed with the readline code
34762 @c and consists of the two following files:
34765 @c Use -I with makeinfo to point to the appropriate directory,
34766 @c environment var TEXINPUTS with TeX.
34767 @ifclear SYSTEM_READLINE
34768 @include rluser.texi
34769 @include hsuser.texi
34773 @appendix In Memoriam
34775 The @value{GDBN} project mourns the loss of the following long-time
34780 Fred was a long-standing contributor to @value{GDBN} (1991-2006), and
34781 to Free Software in general. Outside of @value{GDBN}, he was known in
34782 the Amiga world for his series of Fish Disks, and the GeekGadget project.
34784 @item Michael Snyder
34785 Michael was one of the Global Maintainers of the @value{GDBN} project,
34786 with contributions recorded as early as 1996, until 2011. In addition
34787 to his day to day participation, he was a large driving force behind
34788 adding Reverse Debugging to @value{GDBN}.
34791 Beyond their technical contributions to the project, they were also
34792 enjoyable members of the Free Software Community. We will miss them.
34794 @node Formatting Documentation
34795 @appendix Formatting Documentation
34797 @cindex @value{GDBN} reference card
34798 @cindex reference card
34799 The @value{GDBN} 4 release includes an already-formatted reference card, ready
34800 for printing with PostScript or Ghostscript, in the @file{gdb}
34801 subdirectory of the main source directory@footnote{In
34802 @file{gdb-@value{GDBVN}/gdb/refcard.ps} of the version @value{GDBVN}
34803 release.}. If you can use PostScript or Ghostscript with your printer,
34804 you can print the reference card immediately with @file{refcard.ps}.
34806 The release also includes the source for the reference card. You
34807 can format it, using @TeX{}, by typing:
34813 The @value{GDBN} reference card is designed to print in @dfn{landscape}
34814 mode on US ``letter'' size paper;
34815 that is, on a sheet 11 inches wide by 8.5 inches
34816 high. You will need to specify this form of printing as an option to
34817 your @sc{dvi} output program.
34819 @cindex documentation
34821 All the documentation for @value{GDBN} comes as part of the machine-readable
34822 distribution. The documentation is written in Texinfo format, which is
34823 a documentation system that uses a single source file to produce both
34824 on-line information and a printed manual. You can use one of the Info
34825 formatting commands to create the on-line version of the documentation
34826 and @TeX{} (or @code{texi2roff}) to typeset the printed version.
34828 @value{GDBN} includes an already formatted copy of the on-line Info
34829 version of this manual in the @file{gdb} subdirectory. The main Info
34830 file is @file{gdb-@value{GDBVN}/gdb/gdb.info}, and it refers to
34831 subordinate files matching @samp{gdb.info*} in the same directory. If
34832 necessary, you can print out these files, or read them with any editor;
34833 but they are easier to read using the @code{info} subsystem in @sc{gnu}
34834 Emacs or the standalone @code{info} program, available as part of the
34835 @sc{gnu} Texinfo distribution.
34837 If you want to format these Info files yourself, you need one of the
34838 Info formatting programs, such as @code{texinfo-format-buffer} or
34841 If you have @code{makeinfo} installed, and are in the top level
34842 @value{GDBN} source directory (@file{gdb-@value{GDBVN}}, in the case of
34843 version @value{GDBVN}), you can make the Info file by typing:
34850 If you want to typeset and print copies of this manual, you need @TeX{},
34851 a program to print its @sc{dvi} output files, and @file{texinfo.tex}, the
34852 Texinfo definitions file.
34854 @TeX{} is a typesetting program; it does not print files directly, but
34855 produces output files called @sc{dvi} files. To print a typeset
34856 document, you need a program to print @sc{dvi} files. If your system
34857 has @TeX{} installed, chances are it has such a program. The precise
34858 command to use depends on your system; @kbd{lpr -d} is common; another
34859 (for PostScript devices) is @kbd{dvips}. The @sc{dvi} print command may
34860 require a file name without any extension or a @samp{.dvi} extension.
34862 @TeX{} also requires a macro definitions file called
34863 @file{texinfo.tex}. This file tells @TeX{} how to typeset a document
34864 written in Texinfo format. On its own, @TeX{} cannot either read or
34865 typeset a Texinfo file. @file{texinfo.tex} is distributed with GDB
34866 and is located in the @file{gdb-@var{version-number}/texinfo}
34869 If you have @TeX{} and a @sc{dvi} printer program installed, you can
34870 typeset and print this manual. First switch to the @file{gdb}
34871 subdirectory of the main source directory (for example, to
34872 @file{gdb-@value{GDBVN}/gdb}) and type:
34878 Then give @file{gdb.dvi} to your @sc{dvi} printing program.
34880 @node Installing GDB
34881 @appendix Installing @value{GDBN}
34882 @cindex installation
34885 * Requirements:: Requirements for building @value{GDBN}
34886 * Running Configure:: Invoking the @value{GDBN} @file{configure} script
34887 * Separate Objdir:: Compiling @value{GDBN} in another directory
34888 * Config Names:: Specifying names for hosts and targets
34889 * Configure Options:: Summary of options for configure
34890 * System-wide configuration:: Having a system-wide init file
34894 @section Requirements for Building @value{GDBN}
34895 @cindex building @value{GDBN}, requirements for
34897 Building @value{GDBN} requires various tools and packages to be available.
34898 Other packages will be used only if they are found.
34900 @heading Tools/Packages Necessary for Building @value{GDBN}
34902 @item ISO C90 compiler
34903 @value{GDBN} is written in ISO C90. It should be buildable with any
34904 working C90 compiler, e.g.@: GCC.
34908 @heading Tools/Packages Optional for Building @value{GDBN}
34912 @value{GDBN} can use the Expat XML parsing library. This library may be
34913 included with your operating system distribution; if it is not, you
34914 can get the latest version from @url{http://expat.sourceforge.net}.
34915 The @file{configure} script will search for this library in several
34916 standard locations; if it is installed in an unusual path, you can
34917 use the @option{--with-libexpat-prefix} option to specify its location.
34923 Remote protocol memory maps (@pxref{Memory Map Format})
34925 Target descriptions (@pxref{Target Descriptions})
34927 Remote shared library lists (@xref{Library List Format},
34928 or alternatively @pxref{Library List Format for SVR4 Targets})
34930 MS-Windows shared libraries (@pxref{Shared Libraries})
34932 Traceframe info (@pxref{Traceframe Info Format})
34934 Branch trace (@pxref{Branch Trace Format})
34938 @cindex compressed debug sections
34939 @value{GDBN} will use the @samp{zlib} library, if available, to read
34940 compressed debug sections. Some linkers, such as GNU gold, are capable
34941 of producing binaries with compressed debug sections. If @value{GDBN}
34942 is compiled with @samp{zlib}, it will be able to read the debug
34943 information in such binaries.
34945 The @samp{zlib} library is likely included with your operating system
34946 distribution; if it is not, you can get the latest version from
34947 @url{http://zlib.net}.
34950 @value{GDBN}'s features related to character sets (@pxref{Character
34951 Sets}) require a functioning @code{iconv} implementation. If you are
34952 on a GNU system, then this is provided by the GNU C Library. Some
34953 other systems also provide a working @code{iconv}.
34955 If @value{GDBN} is using the @code{iconv} program which is installed
34956 in a non-standard place, you will need to tell @value{GDBN} where to find it.
34957 This is done with @option{--with-iconv-bin} which specifies the
34958 directory that contains the @code{iconv} program.
34960 On systems without @code{iconv}, you can install GNU Libiconv. If you
34961 have previously installed Libiconv, you can use the
34962 @option{--with-libiconv-prefix} option to configure.
34964 @value{GDBN}'s top-level @file{configure} and @file{Makefile} will
34965 arrange to build Libiconv if a directory named @file{libiconv} appears
34966 in the top-most source directory. If Libiconv is built this way, and
34967 if the operating system does not provide a suitable @code{iconv}
34968 implementation, then the just-built library will automatically be used
34969 by @value{GDBN}. One easy way to set this up is to download GNU
34970 Libiconv, unpack it, and then rename the directory holding the
34971 Libiconv source code to @samp{libiconv}.
34974 @node Running Configure
34975 @section Invoking the @value{GDBN} @file{configure} Script
34976 @cindex configuring @value{GDBN}
34977 @value{GDBN} comes with a @file{configure} script that automates the process
34978 of preparing @value{GDBN} for installation; you can then use @code{make} to
34979 build the @code{gdb} program.
34981 @c irrelevant in info file; it's as current as the code it lives with.
34982 @footnote{If you have a more recent version of @value{GDBN} than @value{GDBVN},
34983 look at the @file{README} file in the sources; we may have improved the
34984 installation procedures since publishing this manual.}
34987 The @value{GDBN} distribution includes all the source code you need for
34988 @value{GDBN} in a single directory, whose name is usually composed by
34989 appending the version number to @samp{gdb}.
34991 For example, the @value{GDBN} version @value{GDBVN} distribution is in the
34992 @file{gdb-@value{GDBVN}} directory. That directory contains:
34995 @item gdb-@value{GDBVN}/configure @r{(and supporting files)}
34996 script for configuring @value{GDBN} and all its supporting libraries
34998 @item gdb-@value{GDBVN}/gdb
34999 the source specific to @value{GDBN} itself
35001 @item gdb-@value{GDBVN}/bfd
35002 source for the Binary File Descriptor library
35004 @item gdb-@value{GDBVN}/include
35005 @sc{gnu} include files
35007 @item gdb-@value{GDBVN}/libiberty
35008 source for the @samp{-liberty} free software library
35010 @item gdb-@value{GDBVN}/opcodes
35011 source for the library of opcode tables and disassemblers
35013 @item gdb-@value{GDBVN}/readline
35014 source for the @sc{gnu} command-line interface
35016 @item gdb-@value{GDBVN}/glob
35017 source for the @sc{gnu} filename pattern-matching subroutine
35019 @item gdb-@value{GDBVN}/mmalloc
35020 source for the @sc{gnu} memory-mapped malloc package
35023 The simplest way to configure and build @value{GDBN} is to run @file{configure}
35024 from the @file{gdb-@var{version-number}} source directory, which in
35025 this example is the @file{gdb-@value{GDBVN}} directory.
35027 First switch to the @file{gdb-@var{version-number}} source directory
35028 if you are not already in it; then run @file{configure}. Pass the
35029 identifier for the platform on which @value{GDBN} will run as an
35035 cd gdb-@value{GDBVN}
35036 ./configure @var{host}
35041 where @var{host} is an identifier such as @samp{sun4} or
35042 @samp{decstation}, that identifies the platform where @value{GDBN} will run.
35043 (You can often leave off @var{host}; @file{configure} tries to guess the
35044 correct value by examining your system.)
35046 Running @samp{configure @var{host}} and then running @code{make} builds the
35047 @file{bfd}, @file{readline}, @file{mmalloc}, and @file{libiberty}
35048 libraries, then @code{gdb} itself. The configured source files, and the
35049 binaries, are left in the corresponding source directories.
35052 @file{configure} is a Bourne-shell (@code{/bin/sh}) script; if your
35053 system does not recognize this automatically when you run a different
35054 shell, you may need to run @code{sh} on it explicitly:
35057 sh configure @var{host}
35060 If you run @file{configure} from a directory that contains source
35061 directories for multiple libraries or programs, such as the
35062 @file{gdb-@value{GDBVN}} source directory for version @value{GDBVN},
35064 creates configuration files for every directory level underneath (unless
35065 you tell it not to, with the @samp{--norecursion} option).
35067 You should run the @file{configure} script from the top directory in the
35068 source tree, the @file{gdb-@var{version-number}} directory. If you run
35069 @file{configure} from one of the subdirectories, you will configure only
35070 that subdirectory. That is usually not what you want. In particular,
35071 if you run the first @file{configure} from the @file{gdb} subdirectory
35072 of the @file{gdb-@var{version-number}} directory, you will omit the
35073 configuration of @file{bfd}, @file{readline}, and other sibling
35074 directories of the @file{gdb} subdirectory. This leads to build errors
35075 about missing include files such as @file{bfd/bfd.h}.
35077 You can install @code{@value{GDBP}} anywhere; it has no hardwired paths.
35078 However, you should make sure that the shell on your path (named by
35079 the @samp{SHELL} environment variable) is publicly readable. Remember
35080 that @value{GDBN} uses the shell to start your program---some systems refuse to
35081 let @value{GDBN} debug child processes whose programs are not readable.
35083 @node Separate Objdir
35084 @section Compiling @value{GDBN} in Another Directory
35086 If you want to run @value{GDBN} versions for several host or target machines,
35087 you need a different @code{gdb} compiled for each combination of
35088 host and target. @file{configure} is designed to make this easy by
35089 allowing you to generate each configuration in a separate subdirectory,
35090 rather than in the source directory. If your @code{make} program
35091 handles the @samp{VPATH} feature (@sc{gnu} @code{make} does), running
35092 @code{make} in each of these directories builds the @code{gdb}
35093 program specified there.
35095 To build @code{gdb} in a separate directory, run @file{configure}
35096 with the @samp{--srcdir} option to specify where to find the source.
35097 (You also need to specify a path to find @file{configure}
35098 itself from your working directory. If the path to @file{configure}
35099 would be the same as the argument to @samp{--srcdir}, you can leave out
35100 the @samp{--srcdir} option; it is assumed.)
35102 For example, with version @value{GDBVN}, you can build @value{GDBN} in a
35103 separate directory for a Sun 4 like this:
35107 cd gdb-@value{GDBVN}
35110 ../gdb-@value{GDBVN}/configure sun4
35115 When @file{configure} builds a configuration using a remote source
35116 directory, it creates a tree for the binaries with the same structure
35117 (and using the same names) as the tree under the source directory. In
35118 the example, you'd find the Sun 4 library @file{libiberty.a} in the
35119 directory @file{gdb-sun4/libiberty}, and @value{GDBN} itself in
35120 @file{gdb-sun4/gdb}.
35122 Make sure that your path to the @file{configure} script has just one
35123 instance of @file{gdb} in it. If your path to @file{configure} looks
35124 like @file{../gdb-@value{GDBVN}/gdb/configure}, you are configuring only
35125 one subdirectory of @value{GDBN}, not the whole package. This leads to
35126 build errors about missing include files such as @file{bfd/bfd.h}.
35128 One popular reason to build several @value{GDBN} configurations in separate
35129 directories is to configure @value{GDBN} for cross-compiling (where
35130 @value{GDBN} runs on one machine---the @dfn{host}---while debugging
35131 programs that run on another machine---the @dfn{target}).
35132 You specify a cross-debugging target by
35133 giving the @samp{--target=@var{target}} option to @file{configure}.
35135 When you run @code{make} to build a program or library, you must run
35136 it in a configured directory---whatever directory you were in when you
35137 called @file{configure} (or one of its subdirectories).
35139 The @code{Makefile} that @file{configure} generates in each source
35140 directory also runs recursively. If you type @code{make} in a source
35141 directory such as @file{gdb-@value{GDBVN}} (or in a separate configured
35142 directory configured with @samp{--srcdir=@var{dirname}/gdb-@value{GDBVN}}), you
35143 will build all the required libraries, and then build GDB.
35145 When you have multiple hosts or targets configured in separate
35146 directories, you can run @code{make} on them in parallel (for example,
35147 if they are NFS-mounted on each of the hosts); they will not interfere
35151 @section Specifying Names for Hosts and Targets
35153 The specifications used for hosts and targets in the @file{configure}
35154 script are based on a three-part naming scheme, but some short predefined
35155 aliases are also supported. The full naming scheme encodes three pieces
35156 of information in the following pattern:
35159 @var{architecture}-@var{vendor}-@var{os}
35162 For example, you can use the alias @code{sun4} as a @var{host} argument,
35163 or as the value for @var{target} in a @code{--target=@var{target}}
35164 option. The equivalent full name is @samp{sparc-sun-sunos4}.
35166 The @file{configure} script accompanying @value{GDBN} does not provide
35167 any query facility to list all supported host and target names or
35168 aliases. @file{configure} calls the Bourne shell script
35169 @code{config.sub} to map abbreviations to full names; you can read the
35170 script, if you wish, or you can use it to test your guesses on
35171 abbreviations---for example:
35174 % sh config.sub i386-linux
35176 % sh config.sub alpha-linux
35177 alpha-unknown-linux-gnu
35178 % sh config.sub hp9k700
35180 % sh config.sub sun4
35181 sparc-sun-sunos4.1.1
35182 % sh config.sub sun3
35183 m68k-sun-sunos4.1.1
35184 % sh config.sub i986v
35185 Invalid configuration `i986v': machine `i986v' not recognized
35189 @code{config.sub} is also distributed in the @value{GDBN} source
35190 directory (@file{gdb-@value{GDBVN}}, for version @value{GDBVN}).
35192 @node Configure Options
35193 @section @file{configure} Options
35195 Here is a summary of the @file{configure} options and arguments that
35196 are most often useful for building @value{GDBN}. @file{configure} also has
35197 several other options not listed here. @inforef{What Configure
35198 Does,,configure.info}, for a full explanation of @file{configure}.
35201 configure @r{[}--help@r{]}
35202 @r{[}--prefix=@var{dir}@r{]}
35203 @r{[}--exec-prefix=@var{dir}@r{]}
35204 @r{[}--srcdir=@var{dirname}@r{]}
35205 @r{[}--norecursion@r{]} @r{[}--rm@r{]}
35206 @r{[}--target=@var{target}@r{]}
35211 You may introduce options with a single @samp{-} rather than
35212 @samp{--} if you prefer; but you may abbreviate option names if you use
35217 Display a quick summary of how to invoke @file{configure}.
35219 @item --prefix=@var{dir}
35220 Configure the source to install programs and files under directory
35223 @item --exec-prefix=@var{dir}
35224 Configure the source to install programs under directory
35227 @c avoid splitting the warning from the explanation:
35229 @item --srcdir=@var{dirname}
35230 @strong{Warning: using this option requires @sc{gnu} @code{make}, or another
35231 @code{make} that implements the @code{VPATH} feature.}@*
35232 Use this option to make configurations in directories separate from the
35233 @value{GDBN} source directories. Among other things, you can use this to
35234 build (or maintain) several configurations simultaneously, in separate
35235 directories. @file{configure} writes configuration-specific files in
35236 the current directory, but arranges for them to use the source in the
35237 directory @var{dirname}. @file{configure} creates directories under
35238 the working directory in parallel to the source directories below
35241 @item --norecursion
35242 Configure only the directory level where @file{configure} is executed; do not
35243 propagate configuration to subdirectories.
35245 @item --target=@var{target}
35246 Configure @value{GDBN} for cross-debugging programs running on the specified
35247 @var{target}. Without this option, @value{GDBN} is configured to debug
35248 programs that run on the same machine (@var{host}) as @value{GDBN} itself.
35250 There is no convenient way to generate a list of all available targets.
35252 @item @var{host} @dots{}
35253 Configure @value{GDBN} to run on the specified @var{host}.
35255 There is no convenient way to generate a list of all available hosts.
35258 There are many other options available as well, but they are generally
35259 needed for special purposes only.
35261 @node System-wide configuration
35262 @section System-wide configuration and settings
35263 @cindex system-wide init file
35265 @value{GDBN} can be configured to have a system-wide init file;
35266 this file will be read and executed at startup (@pxref{Startup, , What
35267 @value{GDBN} does during startup}).
35269 Here is the corresponding configure option:
35272 @item --with-system-gdbinit=@var{file}
35273 Specify that the default location of the system-wide init file is
35277 If @value{GDBN} has been configured with the option @option{--prefix=$prefix},
35278 it may be subject to relocation. Two possible cases:
35282 If the default location of this init file contains @file{$prefix},
35283 it will be subject to relocation. Suppose that the configure options
35284 are @option{--prefix=$prefix --with-system-gdbinit=$prefix/etc/gdbinit};
35285 if @value{GDBN} is moved from @file{$prefix} to @file{$install}, the system
35286 init file is looked for as @file{$install/etc/gdbinit} instead of
35287 @file{$prefix/etc/gdbinit}.
35290 By contrast, if the default location does not contain the prefix,
35291 it will not be relocated. E.g.@: if @value{GDBN} has been configured with
35292 @option{--prefix=/usr/local --with-system-gdbinit=/usr/share/gdb/gdbinit},
35293 then @value{GDBN} will always look for @file{/usr/share/gdb/gdbinit},
35294 wherever @value{GDBN} is installed.
35297 If the configured location of the system-wide init file (as given by the
35298 @option{--with-system-gdbinit} option at configure time) is in the
35299 data-directory (as specified by @option{--with-gdb-datadir} at configure
35300 time) or in one of its subdirectories, then @value{GDBN} will look for the
35301 system-wide init file in the directory specified by the
35302 @option{--data-directory} command-line option.
35303 Note that the system-wide init file is only read once, during @value{GDBN}
35304 initialization. If the data-directory is changed after @value{GDBN} has
35305 started with the @code{set data-directory} command, the file will not be
35308 @node Maintenance Commands
35309 @appendix Maintenance Commands
35310 @cindex maintenance commands
35311 @cindex internal commands
35313 In addition to commands intended for @value{GDBN} users, @value{GDBN}
35314 includes a number of commands intended for @value{GDBN} developers,
35315 that are not documented elsewhere in this manual. These commands are
35316 provided here for reference. (For commands that turn on debugging
35317 messages, see @ref{Debugging Output}.)
35320 @kindex maint agent
35321 @kindex maint agent-eval
35322 @item maint agent @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35323 @itemx maint agent-eval @r{[}-at @var{location}@r{,}@r{]} @var{expression}
35324 Translate the given @var{expression} into remote agent bytecodes.
35325 This command is useful for debugging the Agent Expression mechanism
35326 (@pxref{Agent Expressions}). The @samp{agent} version produces an
35327 expression useful for data collection, such as by tracepoints, while
35328 @samp{maint agent-eval} produces an expression that evaluates directly
35329 to a result. For instance, a collection expression for @code{globa +
35330 globb} will include bytecodes to record four bytes of memory at each
35331 of the addresses of @code{globa} and @code{globb}, while discarding
35332 the result of the addition, while an evaluation expression will do the
35333 addition and return the sum.
35334 If @code{-at} is given, generate remote agent bytecode for @var{location}.
35335 If not, generate remote agent bytecode for current frame PC address.
35337 @kindex maint agent-printf
35338 @item maint agent-printf @var{format},@var{expr},...
35339 Translate the given format string and list of argument expressions
35340 into remote agent bytecodes and display them as a disassembled list.
35341 This command is useful for debugging the agent version of dynamic
35342 printf (@pxref{Dynamic Printf}.
35344 @kindex maint info breakpoints
35345 @item @anchor{maint info breakpoints}maint info breakpoints
35346 Using the same format as @samp{info breakpoints}, display both the
35347 breakpoints you've set explicitly, and those @value{GDBN} is using for
35348 internal purposes. Internal breakpoints are shown with negative
35349 breakpoint numbers. The type column identifies what kind of breakpoint
35354 Normal, explicitly set breakpoint.
35357 Normal, explicitly set watchpoint.
35360 Internal breakpoint, used to handle correctly stepping through
35361 @code{longjmp} calls.
35363 @item longjmp resume
35364 Internal breakpoint at the target of a @code{longjmp}.
35367 Temporary internal breakpoint used by the @value{GDBN} @code{until} command.
35370 Temporary internal breakpoint used by the @value{GDBN} @code{finish} command.
35373 Shared library events.
35377 @kindex maint info bfds
35378 @item maint info bfds
35379 This prints information about each @code{bfd} object that is known to
35380 @value{GDBN}. @xref{Top, , BFD, bfd, The Binary File Descriptor Library}.
35382 @kindex set displaced-stepping
35383 @kindex show displaced-stepping
35384 @cindex displaced stepping support
35385 @cindex out-of-line single-stepping
35386 @item set displaced-stepping
35387 @itemx show displaced-stepping
35388 Control whether or not @value{GDBN} will do @dfn{displaced stepping}
35389 if the target supports it. Displaced stepping is a way to single-step
35390 over breakpoints without removing them from the inferior, by executing
35391 an out-of-line copy of the instruction that was originally at the
35392 breakpoint location. It is also known as out-of-line single-stepping.
35395 @item set displaced-stepping on
35396 If the target architecture supports it, @value{GDBN} will use
35397 displaced stepping to step over breakpoints.
35399 @item set displaced-stepping off
35400 @value{GDBN} will not use displaced stepping to step over breakpoints,
35401 even if such is supported by the target architecture.
35403 @cindex non-stop mode, and @samp{set displaced-stepping}
35404 @item set displaced-stepping auto
35405 This is the default mode. @value{GDBN} will use displaced stepping
35406 only if non-stop mode is active (@pxref{Non-Stop Mode}) and the target
35407 architecture supports displaced stepping.
35410 @kindex maint check-symtabs
35411 @item maint check-symtabs
35412 Check the consistency of psymtabs and symtabs.
35414 @kindex maint cplus first_component
35415 @item maint cplus first_component @var{name}
35416 Print the first C@t{++} class/namespace component of @var{name}.
35418 @kindex maint cplus namespace
35419 @item maint cplus namespace
35420 Print the list of possible C@t{++} namespaces.
35422 @kindex maint demangle
35423 @item maint demangle @var{name}
35424 Demangle a C@t{++} or Objective-C mangled @var{name}.
35426 @kindex maint deprecate
35427 @kindex maint undeprecate
35428 @cindex deprecated commands
35429 @item maint deprecate @var{command} @r{[}@var{replacement}@r{]}
35430 @itemx maint undeprecate @var{command}
35431 Deprecate or undeprecate the named @var{command}. Deprecated commands
35432 cause @value{GDBN} to issue a warning when you use them. The optional
35433 argument @var{replacement} says which newer command should be used in
35434 favor of the deprecated one; if it is given, @value{GDBN} will mention
35435 the replacement as part of the warning.
35437 @kindex maint dump-me
35438 @item maint dump-me
35439 @cindex @code{SIGQUIT} signal, dump core of @value{GDBN}
35440 Cause a fatal signal in the debugger and force it to dump its core.
35441 This is supported only on systems which support aborting a program
35442 with the @code{SIGQUIT} signal.
35444 @kindex maint internal-error
35445 @kindex maint internal-warning
35446 @item maint internal-error @r{[}@var{message-text}@r{]}
35447 @itemx maint internal-warning @r{[}@var{message-text}@r{]}
35448 Cause @value{GDBN} to call the internal function @code{internal_error}
35449 or @code{internal_warning} and hence behave as though an internal error
35450 or internal warning has been detected. In addition to reporting the
35451 internal problem, these functions give the user the opportunity to
35452 either quit @value{GDBN} or create a core file of the current
35453 @value{GDBN} session.
35455 These commands take an optional parameter @var{message-text} that is
35456 used as the text of the error or warning message.
35458 Here's an example of using @code{internal-error}:
35461 (@value{GDBP}) @kbd{maint internal-error testing, 1, 2}
35462 @dots{}/maint.c:121: internal-error: testing, 1, 2
35463 A problem internal to GDB has been detected. Further
35464 debugging may prove unreliable.
35465 Quit this debugging session? (y or n) @kbd{n}
35466 Create a core file? (y or n) @kbd{n}
35470 @cindex @value{GDBN} internal error
35471 @cindex internal errors, control of @value{GDBN} behavior
35473 @kindex maint set internal-error
35474 @kindex maint show internal-error
35475 @kindex maint set internal-warning
35476 @kindex maint show internal-warning
35477 @item maint set internal-error @var{action} [ask|yes|no]
35478 @itemx maint show internal-error @var{action}
35479 @itemx maint set internal-warning @var{action} [ask|yes|no]
35480 @itemx maint show internal-warning @var{action}
35481 When @value{GDBN} reports an internal problem (error or warning) it
35482 gives the user the opportunity to both quit @value{GDBN} and create a
35483 core file of the current @value{GDBN} session. These commands let you
35484 override the default behaviour for each particular @var{action},
35485 described in the table below.
35489 You can specify that @value{GDBN} should always (yes) or never (no)
35490 quit. The default is to ask the user what to do.
35493 You can specify that @value{GDBN} should always (yes) or never (no)
35494 create a core file. The default is to ask the user what to do.
35497 @kindex maint packet
35498 @item maint packet @var{text}
35499 If @value{GDBN} is talking to an inferior via the serial protocol,
35500 then this command sends the string @var{text} to the inferior, and
35501 displays the response packet. @value{GDBN} supplies the initial
35502 @samp{$} character, the terminating @samp{#} character, and the
35505 @kindex maint print architecture
35506 @item maint print architecture @r{[}@var{file}@r{]}
35507 Print the entire architecture configuration. The optional argument
35508 @var{file} names the file where the output goes.
35510 @kindex maint print c-tdesc
35511 @item maint print c-tdesc
35512 Print the current target description (@pxref{Target Descriptions}) as
35513 a C source file. The created source file can be used in @value{GDBN}
35514 when an XML parser is not available to parse the description.
35516 @kindex maint print dummy-frames
35517 @item maint print dummy-frames
35518 Prints the contents of @value{GDBN}'s internal dummy-frame stack.
35521 (@value{GDBP}) @kbd{b add}
35523 (@value{GDBP}) @kbd{print add(2,3)}
35524 Breakpoint 2, add (a=2, b=3) at @dots{}
35526 The program being debugged stopped while in a function called from GDB.
35528 (@value{GDBP}) @kbd{maint print dummy-frames}
35529 0x1a57c80: pc=0x01014068 fp=0x0200bddc sp=0x0200bdd6
35530 top=0x0200bdd4 id=@{stack=0x200bddc,code=0x101405c@}
35531 call_lo=0x01014000 call_hi=0x01014001
35535 Takes an optional file parameter.
35537 @kindex maint print registers
35538 @kindex maint print raw-registers
35539 @kindex maint print cooked-registers
35540 @kindex maint print register-groups
35541 @kindex maint print remote-registers
35542 @item maint print registers @r{[}@var{file}@r{]}
35543 @itemx maint print raw-registers @r{[}@var{file}@r{]}
35544 @itemx maint print cooked-registers @r{[}@var{file}@r{]}
35545 @itemx maint print register-groups @r{[}@var{file}@r{]}
35546 @itemx maint print remote-registers @r{[}@var{file}@r{]}
35547 Print @value{GDBN}'s internal register data structures.
35549 The command @code{maint print raw-registers} includes the contents of
35550 the raw register cache; the command @code{maint print
35551 cooked-registers} includes the (cooked) value of all registers,
35552 including registers which aren't available on the target nor visible
35553 to user; the command @code{maint print register-groups} includes the
35554 groups that each register is a member of; and the command @code{maint
35555 print remote-registers} includes the remote target's register numbers
35556 and offsets in the `G' packets. @xref{Registers,, Registers, gdbint,
35557 @value{GDBN} Internals}.
35559 These commands take an optional parameter, a file name to which to
35560 write the information.
35562 @kindex maint print reggroups
35563 @item maint print reggroups @r{[}@var{file}@r{]}
35564 Print @value{GDBN}'s internal register group data structures. The
35565 optional argument @var{file} tells to what file to write the
35568 The register groups info looks like this:
35571 (@value{GDBP}) @kbd{maint print reggroups}
35584 This command forces @value{GDBN} to flush its internal register cache.
35586 @kindex maint print objfiles
35587 @cindex info for known object files
35588 @item maint print objfiles
35589 Print a dump of all known object files. For each object file, this
35590 command prints its name, address in memory, and all of its psymtabs
35593 @kindex maint print section-scripts
35594 @cindex info for known .debug_gdb_scripts-loaded scripts
35595 @item maint print section-scripts [@var{regexp}]
35596 Print a dump of scripts specified in the @code{.debug_gdb_section} section.
35597 If @var{regexp} is specified, only print scripts loaded by object files
35598 matching @var{regexp}.
35599 For each script, this command prints its name as specified in the objfile,
35600 and the full path if known.
35601 @xref{dotdebug_gdb_scripts section}.
35603 @kindex maint print statistics
35604 @cindex bcache statistics
35605 @item maint print statistics
35606 This command prints, for each object file in the program, various data
35607 about that object file followed by the byte cache (@dfn{bcache})
35608 statistics for the object file. The objfile data includes the number
35609 of minimal, partial, full, and stabs symbols, the number of types
35610 defined by the objfile, the number of as yet unexpanded psym tables,
35611 the number of line tables and string tables, and the amount of memory
35612 used by the various tables. The bcache statistics include the counts,
35613 sizes, and counts of duplicates of all and unique objects, max,
35614 average, and median entry size, total memory used and its overhead and
35615 savings, and various measures of the hash table size and chain
35618 @kindex maint print target-stack
35619 @cindex target stack description
35620 @item maint print target-stack
35621 A @dfn{target} is an interface between the debugger and a particular
35622 kind of file or process. Targets can be stacked in @dfn{strata},
35623 so that more than one target can potentially respond to a request.
35624 In particular, memory accesses will walk down the stack of targets
35625 until they find a target that is interested in handling that particular
35628 This command prints a short description of each layer that was pushed on
35629 the @dfn{target stack}, starting from the top layer down to the bottom one.
35631 @kindex maint print type
35632 @cindex type chain of a data type
35633 @item maint print type @var{expr}
35634 Print the type chain for a type specified by @var{expr}. The argument
35635 can be either a type name or a symbol. If it is a symbol, the type of
35636 that symbol is described. The type chain produced by this command is
35637 a recursive definition of the data type as stored in @value{GDBN}'s
35638 data structures, including its flags and contained types.
35640 @kindex maint set dwarf2 always-disassemble
35641 @kindex maint show dwarf2 always-disassemble
35642 @item maint set dwarf2 always-disassemble
35643 @item maint show dwarf2 always-disassemble
35644 Control the behavior of @code{info address} when using DWARF debugging
35647 The default is @code{off}, which means that @value{GDBN} should try to
35648 describe a variable's location in an easily readable format. When
35649 @code{on}, @value{GDBN} will instead display the DWARF location
35650 expression in an assembly-like format. Note that some locations are
35651 too complex for @value{GDBN} to describe simply; in this case you will
35652 always see the disassembly form.
35654 Here is an example of the resulting disassembly:
35657 (gdb) info addr argc
35658 Symbol "argc" is a complex DWARF expression:
35662 For more information on these expressions, see
35663 @uref{http://www.dwarfstd.org/, the DWARF standard}.
35665 @kindex maint set dwarf2 max-cache-age
35666 @kindex maint show dwarf2 max-cache-age
35667 @item maint set dwarf2 max-cache-age
35668 @itemx maint show dwarf2 max-cache-age
35669 Control the DWARF 2 compilation unit cache.
35671 @cindex DWARF 2 compilation units cache
35672 In object files with inter-compilation-unit references, such as those
35673 produced by the GCC option @samp{-feliminate-dwarf2-dups}, the DWARF 2
35674 reader needs to frequently refer to previously read compilation units.
35675 This setting controls how long a compilation unit will remain in the
35676 cache if it is not referenced. A higher limit means that cached
35677 compilation units will be stored in memory longer, and more total
35678 memory will be used. Setting it to zero disables caching, which will
35679 slow down @value{GDBN} startup, but reduce memory consumption.
35681 @kindex maint set profile
35682 @kindex maint show profile
35683 @cindex profiling GDB
35684 @item maint set profile
35685 @itemx maint show profile
35686 Control profiling of @value{GDBN}.
35688 Profiling will be disabled until you use the @samp{maint set profile}
35689 command to enable it. When you enable profiling, the system will begin
35690 collecting timing and execution count data; when you disable profiling or
35691 exit @value{GDBN}, the results will be written to a log file. Remember that
35692 if you use profiling, @value{GDBN} will overwrite the profiling log file
35693 (often called @file{gmon.out}). If you have a record of important profiling
35694 data in a @file{gmon.out} file, be sure to move it to a safe location.
35696 Configuring with @samp{--enable-profiling} arranges for @value{GDBN} to be
35697 compiled with the @samp{-pg} compiler option.
35699 @kindex maint set show-debug-regs
35700 @kindex maint show show-debug-regs
35701 @cindex hardware debug registers
35702 @item maint set show-debug-regs
35703 @itemx maint show show-debug-regs
35704 Control whether to show variables that mirror the hardware debug
35705 registers. Use @code{ON} to enable, @code{OFF} to disable. If
35706 enabled, the debug registers values are shown when @value{GDBN} inserts or
35707 removes a hardware breakpoint or watchpoint, and when the inferior
35708 triggers a hardware-assisted breakpoint or watchpoint.
35710 @kindex maint set show-all-tib
35711 @kindex maint show show-all-tib
35712 @item maint set show-all-tib
35713 @itemx maint show show-all-tib
35714 Control whether to show all non zero areas within a 1k block starting
35715 at thread local base, when using the @samp{info w32 thread-information-block}
35718 @kindex maint space
35719 @cindex memory used by commands
35721 Control whether to display memory usage for each command. If set to a
35722 nonzero value, @value{GDBN} will display how much memory each command
35723 took, following the command's own output. This can also be requested
35724 by invoking @value{GDBN} with the @option{--statistics} command-line
35725 switch (@pxref{Mode Options}).
35728 @cindex time of command execution
35730 Control whether to display the execution time of @value{GDBN} for each command.
35731 If set to a nonzero value, @value{GDBN} will display how much time it
35732 took to execute each command, following the command's own output.
35733 Both CPU time and wallclock time are printed.
35734 Printing both is useful when trying to determine whether the cost is
35735 CPU or, e.g., disk/network, latency.
35736 Note that the CPU time printed is for @value{GDBN} only, it does not include
35737 the execution time of the inferior because there's no mechanism currently
35738 to compute how much time was spent by @value{GDBN} and how much time was
35739 spent by the program been debugged.
35740 This can also be requested by invoking @value{GDBN} with the
35741 @option{--statistics} command-line switch (@pxref{Mode Options}).
35743 @kindex maint translate-address
35744 @item maint translate-address @r{[}@var{section}@r{]} @var{addr}
35745 Find the symbol stored at the location specified by the address
35746 @var{addr} and an optional section name @var{section}. If found,
35747 @value{GDBN} prints the name of the closest symbol and an offset from
35748 the symbol's location to the specified address. This is similar to
35749 the @code{info address} command (@pxref{Symbols}), except that this
35750 command also allows to find symbols in other sections.
35752 If section was not specified, the section in which the symbol was found
35753 is also printed. For dynamically linked executables, the name of
35754 executable or shared library containing the symbol is printed as well.
35758 The following command is useful for non-interactive invocations of
35759 @value{GDBN}, such as in the test suite.
35762 @item set watchdog @var{nsec}
35763 @kindex set watchdog
35764 @cindex watchdog timer
35765 @cindex timeout for commands
35766 Set the maximum number of seconds @value{GDBN} will wait for the
35767 target operation to finish. If this time expires, @value{GDBN}
35768 reports and error and the command is aborted.
35770 @item show watchdog
35771 Show the current setting of the target wait timeout.
35774 @node Remote Protocol
35775 @appendix @value{GDBN} Remote Serial Protocol
35780 * Stop Reply Packets::
35781 * General Query Packets::
35782 * Architecture-Specific Protocol Details::
35783 * Tracepoint Packets::
35784 * Host I/O Packets::
35786 * Notification Packets::
35787 * Remote Non-Stop::
35788 * Packet Acknowledgment::
35790 * File-I/O Remote Protocol Extension::
35791 * Library List Format::
35792 * Library List Format for SVR4 Targets::
35793 * Memory Map Format::
35794 * Thread List Format::
35795 * Traceframe Info Format::
35796 * Branch Trace Format::
35802 There may be occasions when you need to know something about the
35803 protocol---for example, if there is only one serial port to your target
35804 machine, you might want your program to do something special if it
35805 recognizes a packet meant for @value{GDBN}.
35807 In the examples below, @samp{->} and @samp{<-} are used to indicate
35808 transmitted and received data, respectively.
35810 @cindex protocol, @value{GDBN} remote serial
35811 @cindex serial protocol, @value{GDBN} remote
35812 @cindex remote serial protocol
35813 All @value{GDBN} commands and responses (other than acknowledgments
35814 and notifications, see @ref{Notification Packets}) are sent as a
35815 @var{packet}. A @var{packet} is introduced with the character
35816 @samp{$}, the actual @var{packet-data}, and the terminating character
35817 @samp{#} followed by a two-digit @var{checksum}:
35820 @code{$}@var{packet-data}@code{#}@var{checksum}
35824 @cindex checksum, for @value{GDBN} remote
35826 The two-digit @var{checksum} is computed as the modulo 256 sum of all
35827 characters between the leading @samp{$} and the trailing @samp{#} (an
35828 eight bit unsigned checksum).
35830 Implementors should note that prior to @value{GDBN} 5.0 the protocol
35831 specification also included an optional two-digit @var{sequence-id}:
35834 @code{$}@var{sequence-id}@code{:}@var{packet-data}@code{#}@var{checksum}
35837 @cindex sequence-id, for @value{GDBN} remote
35839 That @var{sequence-id} was appended to the acknowledgment. @value{GDBN}
35840 has never output @var{sequence-id}s. Stubs that handle packets added
35841 since @value{GDBN} 5.0 must not accept @var{sequence-id}.
35843 When either the host or the target machine receives a packet, the first
35844 response expected is an acknowledgment: either @samp{+} (to indicate
35845 the package was received correctly) or @samp{-} (to request
35849 -> @code{$}@var{packet-data}@code{#}@var{checksum}
35854 The @samp{+}/@samp{-} acknowledgments can be disabled
35855 once a connection is established.
35856 @xref{Packet Acknowledgment}, for details.
35858 The host (@value{GDBN}) sends @var{command}s, and the target (the
35859 debugging stub incorporated in your program) sends a @var{response}. In
35860 the case of step and continue @var{command}s, the response is only sent
35861 when the operation has completed, and the target has again stopped all
35862 threads in all attached processes. This is the default all-stop mode
35863 behavior, but the remote protocol also supports @value{GDBN}'s non-stop
35864 execution mode; see @ref{Remote Non-Stop}, for details.
35866 @var{packet-data} consists of a sequence of characters with the
35867 exception of @samp{#} and @samp{$} (see @samp{X} packet for additional
35870 @cindex remote protocol, field separator
35871 Fields within the packet should be separated using @samp{,} @samp{;} or
35872 @samp{:}. Except where otherwise noted all numbers are represented in
35873 @sc{hex} with leading zeros suppressed.
35875 Implementors should note that prior to @value{GDBN} 5.0, the character
35876 @samp{:} could not appear as the third character in a packet (as it
35877 would potentially conflict with the @var{sequence-id}).
35879 @cindex remote protocol, binary data
35880 @anchor{Binary Data}
35881 Binary data in most packets is encoded either as two hexadecimal
35882 digits per byte of binary data. This allowed the traditional remote
35883 protocol to work over connections which were only seven-bit clean.
35884 Some packets designed more recently assume an eight-bit clean
35885 connection, and use a more efficient encoding to send and receive
35888 The binary data representation uses @code{7d} (@sc{ascii} @samp{@}})
35889 as an escape character. Any escaped byte is transmitted as the escape
35890 character followed by the original character XORed with @code{0x20}.
35891 For example, the byte @code{0x7d} would be transmitted as the two
35892 bytes @code{0x7d 0x5d}. The bytes @code{0x23} (@sc{ascii} @samp{#}),
35893 @code{0x24} (@sc{ascii} @samp{$}), and @code{0x7d} (@sc{ascii}
35894 @samp{@}}) must always be escaped. Responses sent by the stub
35895 must also escape @code{0x2a} (@sc{ascii} @samp{*}), so that it
35896 is not interpreted as the start of a run-length encoded sequence
35899 Response @var{data} can be run-length encoded to save space.
35900 Run-length encoding replaces runs of identical characters with one
35901 instance of the repeated character, followed by a @samp{*} and a
35902 repeat count. The repeat count is itself sent encoded, to avoid
35903 binary characters in @var{data}: a value of @var{n} is sent as
35904 @code{@var{n}+29}. For a repeat count greater or equal to 3, this
35905 produces a printable @sc{ascii} character, e.g.@: a space (@sc{ascii}
35906 code 32) for a repeat count of 3. (This is because run-length
35907 encoding starts to win for counts 3 or more.) Thus, for example,
35908 @samp{0* } is a run-length encoding of ``0000'': the space character
35909 after @samp{*} means repeat the leading @code{0} @w{@code{32 - 29 =
35912 The printable characters @samp{#} and @samp{$} or with a numeric value
35913 greater than 126 must not be used. Runs of six repeats (@samp{#}) or
35914 seven repeats (@samp{$}) can be expanded using a repeat count of only
35915 five (@samp{"}). For example, @samp{00000000} can be encoded as
35918 The error response returned for some packets includes a two character
35919 error number. That number is not well defined.
35921 @cindex empty response, for unsupported packets
35922 For any @var{command} not supported by the stub, an empty response
35923 (@samp{$#00}) should be returned. That way it is possible to extend the
35924 protocol. A newer @value{GDBN} can tell if a packet is supported based
35927 At a minimum, a stub is required to support the @samp{g} and @samp{G}
35928 commands for register access, and the @samp{m} and @samp{M} commands
35929 for memory access. Stubs that only control single-threaded targets
35930 can implement run control with the @samp{c} (continue), and @samp{s}
35931 (step) commands. Stubs that support multi-threading targets should
35932 support the @samp{vCont} command. All other commands are optional.
35937 The following table provides a complete list of all currently defined
35938 @var{command}s and their corresponding response @var{data}.
35939 @xref{File-I/O Remote Protocol Extension}, for details about the File
35940 I/O extension of the remote protocol.
35942 Each packet's description has a template showing the packet's overall
35943 syntax, followed by an explanation of the packet's meaning. We
35944 include spaces in some of the templates for clarity; these are not
35945 part of the packet's syntax. No @value{GDBN} packet uses spaces to
35946 separate its components. For example, a template like @samp{foo
35947 @var{bar} @var{baz}} describes a packet beginning with the three ASCII
35948 bytes @samp{foo}, followed by a @var{bar}, followed directly by a
35949 @var{baz}. @value{GDBN} does not transmit a space character between the
35950 @samp{foo} and the @var{bar}, or between the @var{bar} and the
35953 @cindex @var{thread-id}, in remote protocol
35954 @anchor{thread-id syntax}
35955 Several packets and replies include a @var{thread-id} field to identify
35956 a thread. Normally these are positive numbers with a target-specific
35957 interpretation, formatted as big-endian hex strings. A @var{thread-id}
35958 can also be a literal @samp{-1} to indicate all threads, or @samp{0} to
35961 In addition, the remote protocol supports a multiprocess feature in
35962 which the @var{thread-id} syntax is extended to optionally include both
35963 process and thread ID fields, as @samp{p@var{pid}.@var{tid}}.
35964 The @var{pid} (process) and @var{tid} (thread) components each have the
35965 format described above: a positive number with target-specific
35966 interpretation formatted as a big-endian hex string, literal @samp{-1}
35967 to indicate all processes or threads (respectively), or @samp{0} to
35968 indicate an arbitrary process or thread. Specifying just a process, as
35969 @samp{p@var{pid}}, is equivalent to @samp{p@var{pid}.-1}. It is an
35970 error to specify all processes but a specific thread, such as
35971 @samp{p-1.@var{tid}}. Note that the @samp{p} prefix is @emph{not} used
35972 for those packets and replies explicitly documented to include a process
35973 ID, rather than a @var{thread-id}.
35975 The multiprocess @var{thread-id} syntax extensions are only used if both
35976 @value{GDBN} and the stub report support for the @samp{multiprocess}
35977 feature using @samp{qSupported}. @xref{multiprocess extensions}, for
35980 Note that all packet forms beginning with an upper- or lower-case
35981 letter, other than those described here, are reserved for future use.
35983 Here are the packet descriptions.
35988 @cindex @samp{!} packet
35989 @anchor{extended mode}
35990 Enable extended mode. In extended mode, the remote server is made
35991 persistent. The @samp{R} packet is used to restart the program being
35997 The remote target both supports and has enabled extended mode.
36001 @cindex @samp{?} packet
36002 Indicate the reason the target halted. The reply is the same as for
36003 step and continue. This packet has a special interpretation when the
36004 target is in non-stop mode; see @ref{Remote Non-Stop}.
36007 @xref{Stop Reply Packets}, for the reply specifications.
36009 @item A @var{arglen},@var{argnum},@var{arg},@dots{}
36010 @cindex @samp{A} packet
36011 Initialized @code{argv[]} array passed into program. @var{arglen}
36012 specifies the number of bytes in the hex encoded byte stream
36013 @var{arg}. See @code{gdbserver} for more details.
36018 The arguments were set.
36024 @cindex @samp{b} packet
36025 (Don't use this packet; its behavior is not well-defined.)
36026 Change the serial line speed to @var{baud}.
36028 JTC: @emph{When does the transport layer state change? When it's
36029 received, or after the ACK is transmitted. In either case, there are
36030 problems if the command or the acknowledgment packet is dropped.}
36032 Stan: @emph{If people really wanted to add something like this, and get
36033 it working for the first time, they ought to modify ser-unix.c to send
36034 some kind of out-of-band message to a specially-setup stub and have the
36035 switch happen "in between" packets, so that from remote protocol's point
36036 of view, nothing actually happened.}
36038 @item B @var{addr},@var{mode}
36039 @cindex @samp{B} packet
36040 Set (@var{mode} is @samp{S}) or clear (@var{mode} is @samp{C}) a
36041 breakpoint at @var{addr}.
36043 Don't use this packet. Use the @samp{Z} and @samp{z} packets instead
36044 (@pxref{insert breakpoint or watchpoint packet}).
36046 @cindex @samp{bc} packet
36049 Backward continue. Execute the target system in reverse. No parameter.
36050 @xref{Reverse Execution}, for more information.
36053 @xref{Stop Reply Packets}, for the reply specifications.
36055 @cindex @samp{bs} packet
36058 Backward single step. Execute one instruction in reverse. No parameter.
36059 @xref{Reverse Execution}, for more information.
36062 @xref{Stop Reply Packets}, for the reply specifications.
36064 @item c @r{[}@var{addr}@r{]}
36065 @cindex @samp{c} packet
36066 Continue. @var{addr} is address to resume. If @var{addr} is omitted,
36067 resume at current address.
36069 This packet is deprecated for multi-threading support. @xref{vCont
36073 @xref{Stop Reply Packets}, for the reply specifications.
36075 @item C @var{sig}@r{[};@var{addr}@r{]}
36076 @cindex @samp{C} packet
36077 Continue with signal @var{sig} (hex signal number). If
36078 @samp{;@var{addr}} is omitted, resume at same address.
36080 This packet is deprecated for multi-threading support. @xref{vCont
36084 @xref{Stop Reply Packets}, for the reply specifications.
36087 @cindex @samp{d} packet
36090 Don't use this packet; instead, define a general set packet
36091 (@pxref{General Query Packets}).
36095 @cindex @samp{D} packet
36096 The first form of the packet is used to detach @value{GDBN} from the
36097 remote system. It is sent to the remote target
36098 before @value{GDBN} disconnects via the @code{detach} command.
36100 The second form, including a process ID, is used when multiprocess
36101 protocol extensions are enabled (@pxref{multiprocess extensions}), to
36102 detach only a specific process. The @var{pid} is specified as a
36103 big-endian hex string.
36113 @item F @var{RC},@var{EE},@var{CF};@var{XX}
36114 @cindex @samp{F} packet
36115 A reply from @value{GDBN} to an @samp{F} packet sent by the target.
36116 This is part of the File-I/O protocol extension. @xref{File-I/O
36117 Remote Protocol Extension}, for the specification.
36120 @anchor{read registers packet}
36121 @cindex @samp{g} packet
36122 Read general registers.
36126 @item @var{XX@dots{}}
36127 Each byte of register data is described by two hex digits. The bytes
36128 with the register are transmitted in target byte order. The size of
36129 each register and their position within the @samp{g} packet are
36130 determined by the @value{GDBN} internal gdbarch functions
36131 @code{DEPRECATED_REGISTER_RAW_SIZE} and @code{gdbarch_register_name}. The
36132 specification of several standard @samp{g} packets is specified below.
36134 When reading registers from a trace frame (@pxref{Analyze Collected
36135 Data,,Using the Collected Data}), the stub may also return a string of
36136 literal @samp{x}'s in place of the register data digits, to indicate
36137 that the corresponding register has not been collected, thus its value
36138 is unavailable. For example, for an architecture with 4 registers of
36139 4 bytes each, the following reply indicates to @value{GDBN} that
36140 registers 0 and 2 have not been collected, while registers 1 and 3
36141 have been collected, and both have zero value:
36145 <- @code{xxxxxxxx00000000xxxxxxxx00000000}
36152 @item G @var{XX@dots{}}
36153 @cindex @samp{G} packet
36154 Write general registers. @xref{read registers packet}, for a
36155 description of the @var{XX@dots{}} data.
36165 @item H @var{op} @var{thread-id}
36166 @cindex @samp{H} packet
36167 Set thread for subsequent operations (@samp{m}, @samp{M}, @samp{g},
36168 @samp{G}, et.al.). @var{op} depends on the operation to be performed:
36169 it should be @samp{c} for step and continue operations (note that this
36170 is deprecated, supporting the @samp{vCont} command is a better
36171 option), @samp{g} for other operations. The thread designator
36172 @var{thread-id} has the format and interpretation described in
36173 @ref{thread-id syntax}.
36184 @c 'H': How restrictive (or permissive) is the thread model. If a
36185 @c thread is selected and stopped, are other threads allowed
36186 @c to continue to execute? As I mentioned above, I think the
36187 @c semantics of each command when a thread is selected must be
36188 @c described. For example:
36190 @c 'g': If the stub supports threads and a specific thread is
36191 @c selected, returns the register block from that thread;
36192 @c otherwise returns current registers.
36194 @c 'G' If the stub supports threads and a specific thread is
36195 @c selected, sets the registers of the register block of
36196 @c that thread; otherwise sets current registers.
36198 @item i @r{[}@var{addr}@r{[},@var{nnn}@r{]]}
36199 @anchor{cycle step packet}
36200 @cindex @samp{i} packet
36201 Step the remote target by a single clock cycle. If @samp{,@var{nnn}} is
36202 present, cycle step @var{nnn} cycles. If @var{addr} is present, cycle
36203 step starting at that address.
36206 @cindex @samp{I} packet
36207 Signal, then cycle step. @xref{step with signal packet}. @xref{cycle
36211 @cindex @samp{k} packet
36214 FIXME: @emph{There is no description of how to operate when a specific
36215 thread context has been selected (i.e.@: does 'k' kill only that
36218 @item m @var{addr},@var{length}
36219 @cindex @samp{m} packet
36220 Read @var{length} bytes of memory starting at address @var{addr}.
36221 Note that @var{addr} may not be aligned to any particular boundary.
36223 The stub need not use any particular size or alignment when gathering
36224 data from memory for the response; even if @var{addr} is word-aligned
36225 and @var{length} is a multiple of the word size, the stub is free to
36226 use byte accesses, or not. For this reason, this packet may not be
36227 suitable for accessing memory-mapped I/O devices.
36228 @cindex alignment of remote memory accesses
36229 @cindex size of remote memory accesses
36230 @cindex memory, alignment and size of remote accesses
36234 @item @var{XX@dots{}}
36235 Memory contents; each byte is transmitted as a two-digit hexadecimal
36236 number. The reply may contain fewer bytes than requested if the
36237 server was able to read only part of the region of memory.
36242 @item M @var{addr},@var{length}:@var{XX@dots{}}
36243 @cindex @samp{M} packet
36244 Write @var{length} bytes of memory starting at address @var{addr}.
36245 @var{XX@dots{}} is the data; each byte is transmitted as a two-digit
36246 hexadecimal number.
36253 for an error (this includes the case where only part of the data was
36258 @cindex @samp{p} packet
36259 Read the value of register @var{n}; @var{n} is in hex.
36260 @xref{read registers packet}, for a description of how the returned
36261 register value is encoded.
36265 @item @var{XX@dots{}}
36266 the register's value
36270 Indicating an unrecognized @var{query}.
36273 @item P @var{n@dots{}}=@var{r@dots{}}
36274 @anchor{write register packet}
36275 @cindex @samp{P} packet
36276 Write register @var{n@dots{}} with value @var{r@dots{}}. The register
36277 number @var{n} is in hexadecimal, and @var{r@dots{}} contains two hex
36278 digits for each byte in the register (target byte order).
36288 @item q @var{name} @var{params}@dots{}
36289 @itemx Q @var{name} @var{params}@dots{}
36290 @cindex @samp{q} packet
36291 @cindex @samp{Q} packet
36292 General query (@samp{q}) and set (@samp{Q}). These packets are
36293 described fully in @ref{General Query Packets}.
36296 @cindex @samp{r} packet
36297 Reset the entire system.
36299 Don't use this packet; use the @samp{R} packet instead.
36302 @cindex @samp{R} packet
36303 Restart the program being debugged. @var{XX}, while needed, is ignored.
36304 This packet is only available in extended mode (@pxref{extended mode}).
36306 The @samp{R} packet has no reply.
36308 @item s @r{[}@var{addr}@r{]}
36309 @cindex @samp{s} packet
36310 Single step. @var{addr} is the address at which to resume. If
36311 @var{addr} is omitted, resume at same address.
36313 This packet is deprecated for multi-threading support. @xref{vCont
36317 @xref{Stop Reply Packets}, for the reply specifications.
36319 @item S @var{sig}@r{[};@var{addr}@r{]}
36320 @anchor{step with signal packet}
36321 @cindex @samp{S} packet
36322 Step with signal. This is analogous to the @samp{C} packet, but
36323 requests a single-step, rather than a normal resumption of execution.
36325 This packet is deprecated for multi-threading support. @xref{vCont
36329 @xref{Stop Reply Packets}, for the reply specifications.
36331 @item t @var{addr}:@var{PP},@var{MM}
36332 @cindex @samp{t} packet
36333 Search backwards starting at address @var{addr} for a match with pattern
36334 @var{PP} and mask @var{MM}. @var{PP} and @var{MM} are 4 bytes.
36335 @var{addr} must be at least 3 digits.
36337 @item T @var{thread-id}
36338 @cindex @samp{T} packet
36339 Find out if the thread @var{thread-id} is alive. @xref{thread-id syntax}.
36344 thread is still alive
36350 Packets starting with @samp{v} are identified by a multi-letter name,
36351 up to the first @samp{;} or @samp{?} (or the end of the packet).
36353 @item vAttach;@var{pid}
36354 @cindex @samp{vAttach} packet
36355 Attach to a new process with the specified process ID @var{pid}.
36356 The process ID is a
36357 hexadecimal integer identifying the process. In all-stop mode, all
36358 threads in the attached process are stopped; in non-stop mode, it may be
36359 attached without being stopped if that is supported by the target.
36361 @c In non-stop mode, on a successful vAttach, the stub should set the
36362 @c current thread to a thread of the newly-attached process. After
36363 @c attaching, GDB queries for the attached process's thread ID with qC.
36364 @c Also note that, from a user perspective, whether or not the
36365 @c target is stopped on attach in non-stop mode depends on whether you
36366 @c use the foreground or background version of the attach command, not
36367 @c on what vAttach does; GDB does the right thing with respect to either
36368 @c stopping or restarting threads.
36370 This packet is only available in extended mode (@pxref{extended mode}).
36376 @item @r{Any stop packet}
36377 for success in all-stop mode (@pxref{Stop Reply Packets})
36379 for success in non-stop mode (@pxref{Remote Non-Stop})
36382 @item vCont@r{[};@var{action}@r{[}:@var{thread-id}@r{]]}@dots{}
36383 @cindex @samp{vCont} packet
36384 @anchor{vCont packet}
36385 Resume the inferior, specifying different actions for each thread.
36386 If an action is specified with no @var{thread-id}, then it is applied to any
36387 threads that don't have a specific action specified; if no default action is
36388 specified then other threads should remain stopped in all-stop mode and
36389 in their current state in non-stop mode.
36390 Specifying multiple
36391 default actions is an error; specifying no actions is also an error.
36392 Thread IDs are specified using the syntax described in @ref{thread-id syntax}.
36394 Currently supported actions are:
36400 Continue with signal @var{sig}. The signal @var{sig} should be two hex digits.
36404 Step with signal @var{sig}. The signal @var{sig} should be two hex digits.
36409 The optional argument @var{addr} normally associated with the
36410 @samp{c}, @samp{C}, @samp{s}, and @samp{S} packets is
36411 not supported in @samp{vCont}.
36413 The @samp{t} action is only relevant in non-stop mode
36414 (@pxref{Remote Non-Stop}) and may be ignored by the stub otherwise.
36415 A stop reply should be generated for any affected thread not already stopped.
36416 When a thread is stopped by means of a @samp{t} action,
36417 the corresponding stop reply should indicate that the thread has stopped with
36418 signal @samp{0}, regardless of whether the target uses some other signal
36419 as an implementation detail.
36421 The stub must support @samp{vCont} if it reports support for
36422 multiprocess extensions (@pxref{multiprocess extensions}). Note that in
36423 this case @samp{vCont} actions can be specified to apply to all threads
36424 in a process by using the @samp{p@var{pid}.-1} form of the
36428 @xref{Stop Reply Packets}, for the reply specifications.
36431 @cindex @samp{vCont?} packet
36432 Request a list of actions supported by the @samp{vCont} packet.
36436 @item vCont@r{[};@var{action}@dots{}@r{]}
36437 The @samp{vCont} packet is supported. Each @var{action} is a supported
36438 command in the @samp{vCont} packet.
36440 The @samp{vCont} packet is not supported.
36443 @item vFile:@var{operation}:@var{parameter}@dots{}
36444 @cindex @samp{vFile} packet
36445 Perform a file operation on the target system. For details,
36446 see @ref{Host I/O Packets}.
36448 @item vFlashErase:@var{addr},@var{length}
36449 @cindex @samp{vFlashErase} packet
36450 Direct the stub to erase @var{length} bytes of flash starting at
36451 @var{addr}. The region may enclose any number of flash blocks, but
36452 its start and end must fall on block boundaries, as indicated by the
36453 flash block size appearing in the memory map (@pxref{Memory Map
36454 Format}). @value{GDBN} groups flash memory programming operations
36455 together, and sends a @samp{vFlashDone} request after each group; the
36456 stub is allowed to delay erase operation until the @samp{vFlashDone}
36457 packet is received.
36467 @item vFlashWrite:@var{addr}:@var{XX@dots{}}
36468 @cindex @samp{vFlashWrite} packet
36469 Direct the stub to write data to flash address @var{addr}. The data
36470 is passed in binary form using the same encoding as for the @samp{X}
36471 packet (@pxref{Binary Data}). The memory ranges specified by
36472 @samp{vFlashWrite} packets preceding a @samp{vFlashDone} packet must
36473 not overlap, and must appear in order of increasing addresses
36474 (although @samp{vFlashErase} packets for higher addresses may already
36475 have been received; the ordering is guaranteed only between
36476 @samp{vFlashWrite} packets). If a packet writes to an address that was
36477 neither erased by a preceding @samp{vFlashErase} packet nor by some other
36478 target-specific method, the results are unpredictable.
36486 for vFlashWrite addressing non-flash memory
36492 @cindex @samp{vFlashDone} packet
36493 Indicate to the stub that flash programming operation is finished.
36494 The stub is permitted to delay or batch the effects of a group of
36495 @samp{vFlashErase} and @samp{vFlashWrite} packets until a
36496 @samp{vFlashDone} packet is received. The contents of the affected
36497 regions of flash memory are unpredictable until the @samp{vFlashDone}
36498 request is completed.
36500 @item vKill;@var{pid}
36501 @cindex @samp{vKill} packet
36502 Kill the process with the specified process ID. @var{pid} is a
36503 hexadecimal integer identifying the process. This packet is used in
36504 preference to @samp{k} when multiprocess protocol extensions are
36505 supported; see @ref{multiprocess extensions}.
36515 @item vRun;@var{filename}@r{[};@var{argument}@r{]}@dots{}
36516 @cindex @samp{vRun} packet
36517 Run the program @var{filename}, passing it each @var{argument} on its
36518 command line. The file and arguments are hex-encoded strings. If
36519 @var{filename} is an empty string, the stub may use a default program
36520 (e.g.@: the last program run). The program is created in the stopped
36523 @c FIXME: What about non-stop mode?
36525 This packet is only available in extended mode (@pxref{extended mode}).
36531 @item @r{Any stop packet}
36532 for success (@pxref{Stop Reply Packets})
36536 @cindex @samp{vStopped} packet
36537 @xref{Notification Packets}.
36539 @item X @var{addr},@var{length}:@var{XX@dots{}}
36541 @cindex @samp{X} packet
36542 Write data to memory, where the data is transmitted in binary.
36543 @var{addr} is address, @var{length} is number of bytes,
36544 @samp{@var{XX}@dots{}} is binary data (@pxref{Binary Data}).
36554 @item z @var{type},@var{addr},@var{kind}
36555 @itemx Z @var{type},@var{addr},@var{kind}
36556 @anchor{insert breakpoint or watchpoint packet}
36557 @cindex @samp{z} packet
36558 @cindex @samp{Z} packets
36559 Insert (@samp{Z}) or remove (@samp{z}) a @var{type} breakpoint or
36560 watchpoint starting at address @var{address} of kind @var{kind}.
36562 Each breakpoint and watchpoint packet @var{type} is documented
36565 @emph{Implementation notes: A remote target shall return an empty string
36566 for an unrecognized breakpoint or watchpoint packet @var{type}. A
36567 remote target shall support either both or neither of a given
36568 @samp{Z@var{type}@dots{}} and @samp{z@var{type}@dots{}} packet pair. To
36569 avoid potential problems with duplicate packets, the operations should
36570 be implemented in an idempotent way.}
36572 @item z0,@var{addr},@var{kind}
36573 @itemx Z0,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}@r{[};cmds:@var{persist},@var{cmd_list}@dots{}@r{]}
36574 @cindex @samp{z0} packet
36575 @cindex @samp{Z0} packet
36576 Insert (@samp{Z0}) or remove (@samp{z0}) a memory breakpoint at address
36577 @var{addr} of type @var{kind}.
36579 A memory breakpoint is implemented by replacing the instruction at
36580 @var{addr} with a software breakpoint or trap instruction. The
36581 @var{kind} is target-specific and typically indicates the size of
36582 the breakpoint in bytes that should be inserted. E.g., the @sc{arm}
36583 and @sc{mips} can insert either a 2 or 4 byte breakpoint. Some
36584 architectures have additional meanings for @var{kind};
36585 @var{cond_list} is an optional list of conditional expressions in bytecode
36586 form that should be evaluated on the target's side. These are the
36587 conditions that should be taken into consideration when deciding if
36588 the breakpoint trigger should be reported back to @var{GDBN}.
36590 The @var{cond_list} parameter is comprised of a series of expressions,
36591 concatenated without separators. Each expression has the following form:
36595 @item X @var{len},@var{expr}
36596 @var{len} is the length of the bytecode expression and @var{expr} is the
36597 actual conditional expression in bytecode form.
36601 The optional @var{cmd_list} parameter introduces commands that may be
36602 run on the target, rather than being reported back to @value{GDBN}.
36603 The parameter starts with a numeric flag @var{persist}; if the flag is
36604 nonzero, then the breakpoint may remain active and the commands
36605 continue to be run even when @value{GDBN} disconnects from the target.
36606 Following this flag is a series of expressions concatenated with no
36607 separators. Each expression has the following form:
36611 @item X @var{len},@var{expr}
36612 @var{len} is the length of the bytecode expression and @var{expr} is the
36613 actual conditional expression in bytecode form.
36617 see @ref{Architecture-Specific Protocol Details}.
36619 @emph{Implementation note: It is possible for a target to copy or move
36620 code that contains memory breakpoints (e.g., when implementing
36621 overlays). The behavior of this packet, in the presence of such a
36622 target, is not defined.}
36634 @item z1,@var{addr},@var{kind}
36635 @itemx Z1,@var{addr},@var{kind}@r{[};@var{cond_list}@dots{}@r{]}
36636 @cindex @samp{z1} packet
36637 @cindex @samp{Z1} packet
36638 Insert (@samp{Z1}) or remove (@samp{z1}) a hardware breakpoint at
36639 address @var{addr}.
36641 A hardware breakpoint is implemented using a mechanism that is not
36642 dependant on being able to modify the target's memory. @var{kind}
36643 and @var{cond_list} have the same meaning as in @samp{Z0} packets.
36645 @emph{Implementation note: A hardware breakpoint is not affected by code
36658 @item z2,@var{addr},@var{kind}
36659 @itemx Z2,@var{addr},@var{kind}
36660 @cindex @samp{z2} packet
36661 @cindex @samp{Z2} packet
36662 Insert (@samp{Z2}) or remove (@samp{z2}) a write watchpoint at @var{addr}.
36663 @var{kind} is interpreted as the number of bytes to watch.
36675 @item z3,@var{addr},@var{kind}
36676 @itemx Z3,@var{addr},@var{kind}
36677 @cindex @samp{z3} packet
36678 @cindex @samp{Z3} packet
36679 Insert (@samp{Z3}) or remove (@samp{z3}) a read watchpoint at @var{addr}.
36680 @var{kind} is interpreted as the number of bytes to watch.
36692 @item z4,@var{addr},@var{kind}
36693 @itemx Z4,@var{addr},@var{kind}
36694 @cindex @samp{z4} packet
36695 @cindex @samp{Z4} packet
36696 Insert (@samp{Z4}) or remove (@samp{z4}) an access watchpoint at @var{addr}.
36697 @var{kind} is interpreted as the number of bytes to watch.
36711 @node Stop Reply Packets
36712 @section Stop Reply Packets
36713 @cindex stop reply packets
36715 The @samp{C}, @samp{c}, @samp{S}, @samp{s}, @samp{vCont},
36716 @samp{vAttach}, @samp{vRun}, @samp{vStopped}, and @samp{?} packets can
36717 receive any of the below as a reply. Except for @samp{?}
36718 and @samp{vStopped}, that reply is only returned
36719 when the target halts. In the below the exact meaning of @dfn{signal
36720 number} is defined by the header @file{include/gdb/signals.h} in the
36721 @value{GDBN} source code.
36723 As in the description of request packets, we include spaces in the
36724 reply templates for clarity; these are not part of the reply packet's
36725 syntax. No @value{GDBN} stop reply packet uses spaces to separate its
36731 The program received signal number @var{AA} (a two-digit hexadecimal
36732 number). This is equivalent to a @samp{T} response with no
36733 @var{n}:@var{r} pairs.
36735 @item T @var{AA} @var{n1}:@var{r1};@var{n2}:@var{r2};@dots{}
36736 @cindex @samp{T} packet reply
36737 The program received signal number @var{AA} (a two-digit hexadecimal
36738 number). This is equivalent to an @samp{S} response, except that the
36739 @samp{@var{n}:@var{r}} pairs can carry values of important registers
36740 and other information directly in the stop reply packet, reducing
36741 round-trip latency. Single-step and breakpoint traps are reported
36742 this way. Each @samp{@var{n}:@var{r}} pair is interpreted as follows:
36746 If @var{n} is a hexadecimal number, it is a register number, and the
36747 corresponding @var{r} gives that register's value. @var{r} is a
36748 series of bytes in target byte order, with each byte given by a
36749 two-digit hex number.
36752 If @var{n} is @samp{thread}, then @var{r} is the @var{thread-id} of
36753 the stopped thread, as specified in @ref{thread-id syntax}.
36756 If @var{n} is @samp{core}, then @var{r} is the hexadecimal number of
36757 the core on which the stop event was detected.
36760 If @var{n} is a recognized @dfn{stop reason}, it describes a more
36761 specific event that stopped the target. The currently defined stop
36762 reasons are listed below. @var{aa} should be @samp{05}, the trap
36763 signal. At most one stop reason should be present.
36766 Otherwise, @value{GDBN} should ignore this @samp{@var{n}:@var{r}} pair
36767 and go on to the next; this allows us to extend the protocol in the
36771 The currently defined stop reasons are:
36777 The packet indicates a watchpoint hit, and @var{r} is the data address, in
36780 @cindex shared library events, remote reply
36782 The packet indicates that the loaded libraries have changed.
36783 @value{GDBN} should use @samp{qXfer:libraries:read} to fetch a new
36784 list of loaded libraries. @var{r} is ignored.
36786 @cindex replay log events, remote reply
36788 The packet indicates that the target cannot continue replaying
36789 logged execution events, because it has reached the end (or the
36790 beginning when executing backward) of the log. The value of @var{r}
36791 will be either @samp{begin} or @samp{end}. @xref{Reverse Execution},
36792 for more information.
36796 @itemx W @var{AA} ; process:@var{pid}
36797 The process exited, and @var{AA} is the exit status. This is only
36798 applicable to certain targets.
36800 The second form of the response, including the process ID of the exited
36801 process, can be used only when @value{GDBN} has reported support for
36802 multiprocess protocol extensions; see @ref{multiprocess extensions}.
36803 The @var{pid} is formatted as a big-endian hex string.
36806 @itemx X @var{AA} ; process:@var{pid}
36807 The process terminated with signal @var{AA}.
36809 The second form of the response, including the process ID of the
36810 terminated process, can be used only when @value{GDBN} has reported
36811 support for multiprocess protocol extensions; see @ref{multiprocess
36812 extensions}. The @var{pid} is formatted as a big-endian hex string.
36814 @item O @var{XX}@dots{}
36815 @samp{@var{XX}@dots{}} is hex encoding of @sc{ascii} data, to be
36816 written as the program's console output. This can happen at any time
36817 while the program is running and the debugger should continue to wait
36818 for @samp{W}, @samp{T}, etc. This reply is not permitted in non-stop mode.
36820 @item F @var{call-id},@var{parameter}@dots{}
36821 @var{call-id} is the identifier which says which host system call should
36822 be called. This is just the name of the function. Translation into the
36823 correct system call is only applicable as it's defined in @value{GDBN}.
36824 @xref{File-I/O Remote Protocol Extension}, for a list of implemented
36827 @samp{@var{parameter}@dots{}} is a list of parameters as defined for
36828 this very system call.
36830 The target replies with this packet when it expects @value{GDBN} to
36831 call a host system call on behalf of the target. @value{GDBN} replies
36832 with an appropriate @samp{F} packet and keeps up waiting for the next
36833 reply packet from the target. The latest @samp{C}, @samp{c}, @samp{S}
36834 or @samp{s} action is expected to be continued. @xref{File-I/O Remote
36835 Protocol Extension}, for more details.
36839 @node General Query Packets
36840 @section General Query Packets
36841 @cindex remote query requests
36843 Packets starting with @samp{q} are @dfn{general query packets};
36844 packets starting with @samp{Q} are @dfn{general set packets}. General
36845 query and set packets are a semi-unified form for retrieving and
36846 sending information to and from the stub.
36848 The initial letter of a query or set packet is followed by a name
36849 indicating what sort of thing the packet applies to. For example,
36850 @value{GDBN} may use a @samp{qSymbol} packet to exchange symbol
36851 definitions with the stub. These packet names follow some
36856 The name must not contain commas, colons or semicolons.
36858 Most @value{GDBN} query and set packets have a leading upper case
36861 The names of custom vendor packets should use a company prefix, in
36862 lower case, followed by a period. For example, packets designed at
36863 the Acme Corporation might begin with @samp{qacme.foo} (for querying
36864 foos) or @samp{Qacme.bar} (for setting bars).
36867 The name of a query or set packet should be separated from any
36868 parameters by a @samp{:}; the parameters themselves should be
36869 separated by @samp{,} or @samp{;}. Stubs must be careful to match the
36870 full packet name, and check for a separator or the end of the packet,
36871 in case two packet names share a common prefix. New packets should not begin
36872 with @samp{qC}, @samp{qP}, or @samp{qL}@footnote{The @samp{qP} and @samp{qL}
36873 packets predate these conventions, and have arguments without any terminator
36874 for the packet name; we suspect they are in widespread use in places that
36875 are difficult to upgrade. The @samp{qC} packet has no arguments, but some
36876 existing stubs (e.g.@: RedBoot) are known to not check for the end of the
36879 Like the descriptions of the other packets, each description here
36880 has a template showing the packet's overall syntax, followed by an
36881 explanation of the packet's meaning. We include spaces in some of the
36882 templates for clarity; these are not part of the packet's syntax. No
36883 @value{GDBN} packet uses spaces to separate its components.
36885 Here are the currently defined query and set packets:
36891 Turn on or off the agent as a helper to perform some debugging operations
36892 delegated from @value{GDBN} (@pxref{Control Agent}).
36894 @item QAllow:@var{op}:@var{val}@dots{}
36895 @cindex @samp{QAllow} packet
36896 Specify which operations @value{GDBN} expects to request of the
36897 target, as a semicolon-separated list of operation name and value
36898 pairs. Possible values for @var{op} include @samp{WriteReg},
36899 @samp{WriteMem}, @samp{InsertBreak}, @samp{InsertTrace},
36900 @samp{InsertFastTrace}, and @samp{Stop}. @var{val} is either 0,
36901 indicating that @value{GDBN} will not request the operation, or 1,
36902 indicating that it may. (The target can then use this to set up its
36903 own internals optimally, for instance if the debugger never expects to
36904 insert breakpoints, it may not need to install its own trap handler.)
36907 @cindex current thread, remote request
36908 @cindex @samp{qC} packet
36909 Return the current thread ID.
36913 @item QC @var{thread-id}
36914 Where @var{thread-id} is a thread ID as documented in
36915 @ref{thread-id syntax}.
36916 @item @r{(anything else)}
36917 Any other reply implies the old thread ID.
36920 @item qCRC:@var{addr},@var{length}
36921 @cindex CRC of memory block, remote request
36922 @cindex @samp{qCRC} packet
36923 Compute the CRC checksum of a block of memory using CRC-32 defined in
36924 IEEE 802.3. The CRC is computed byte at a time, taking the most
36925 significant bit of each byte first. The initial pattern code
36926 @code{0xffffffff} is used to ensure leading zeros affect the CRC.
36928 @emph{Note:} This is the same CRC used in validating separate debug
36929 files (@pxref{Separate Debug Files, , Debugging Information in Separate
36930 Files}). However the algorithm is slightly different. When validating
36931 separate debug files, the CRC is computed taking the @emph{least}
36932 significant bit of each byte first, and the final result is inverted to
36933 detect trailing zeros.
36938 An error (such as memory fault)
36939 @item C @var{crc32}
36940 The specified memory region's checksum is @var{crc32}.
36943 @item QDisableRandomization:@var{value}
36944 @cindex disable address space randomization, remote request
36945 @cindex @samp{QDisableRandomization} packet
36946 Some target operating systems will randomize the virtual address space
36947 of the inferior process as a security feature, but provide a feature
36948 to disable such randomization, e.g.@: to allow for a more deterministic
36949 debugging experience. On such systems, this packet with a @var{value}
36950 of 1 directs the target to disable address space randomization for
36951 processes subsequently started via @samp{vRun} packets, while a packet
36952 with a @var{value} of 0 tells the target to enable address space
36955 This packet is only available in extended mode (@pxref{extended mode}).
36960 The request succeeded.
36963 An error occurred. @var{nn} are hex digits.
36966 An empty reply indicates that @samp{QDisableRandomization} is not supported
36970 This packet is not probed by default; the remote stub must request it,
36971 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
36972 This should only be done on targets that actually support disabling
36973 address space randomization.
36976 @itemx qsThreadInfo
36977 @cindex list active threads, remote request
36978 @cindex @samp{qfThreadInfo} packet
36979 @cindex @samp{qsThreadInfo} packet
36980 Obtain a list of all active thread IDs from the target (OS). Since there
36981 may be too many active threads to fit into one reply packet, this query
36982 works iteratively: it may require more than one query/reply sequence to
36983 obtain the entire list of threads. The first query of the sequence will
36984 be the @samp{qfThreadInfo} query; subsequent queries in the
36985 sequence will be the @samp{qsThreadInfo} query.
36987 NOTE: This packet replaces the @samp{qL} query (see below).
36991 @item m @var{thread-id}
36993 @item m @var{thread-id},@var{thread-id}@dots{}
36994 a comma-separated list of thread IDs
36996 (lower case letter @samp{L}) denotes end of list.
36999 In response to each query, the target will reply with a list of one or
37000 more thread IDs, separated by commas.
37001 @value{GDBN} will respond to each reply with a request for more thread
37002 ids (using the @samp{qs} form of the query), until the target responds
37003 with @samp{l} (lower-case ell, for @dfn{last}).
37004 Refer to @ref{thread-id syntax}, for the format of the @var{thread-id}
37007 @item qGetTLSAddr:@var{thread-id},@var{offset},@var{lm}
37008 @cindex get thread-local storage address, remote request
37009 @cindex @samp{qGetTLSAddr} packet
37010 Fetch the address associated with thread local storage specified
37011 by @var{thread-id}, @var{offset}, and @var{lm}.
37013 @var{thread-id} is the thread ID associated with the
37014 thread for which to fetch the TLS address. @xref{thread-id syntax}.
37016 @var{offset} is the (big endian, hex encoded) offset associated with the
37017 thread local variable. (This offset is obtained from the debug
37018 information associated with the variable.)
37020 @var{lm} is the (big endian, hex encoded) OS/ABI-specific encoding of the
37021 load module associated with the thread local storage. For example,
37022 a @sc{gnu}/Linux system will pass the link map address of the shared
37023 object associated with the thread local storage under consideration.
37024 Other operating environments may choose to represent the load module
37025 differently, so the precise meaning of this parameter will vary.
37029 @item @var{XX}@dots{}
37030 Hex encoded (big endian) bytes representing the address of the thread
37031 local storage requested.
37034 An error occurred. @var{nn} are hex digits.
37037 An empty reply indicates that @samp{qGetTLSAddr} is not supported by the stub.
37040 @item qGetTIBAddr:@var{thread-id}
37041 @cindex get thread information block address
37042 @cindex @samp{qGetTIBAddr} packet
37043 Fetch address of the Windows OS specific Thread Information Block.
37045 @var{thread-id} is the thread ID associated with the thread.
37049 @item @var{XX}@dots{}
37050 Hex encoded (big endian) bytes representing the linear address of the
37051 thread information block.
37054 An error occured. This means that either the thread was not found, or the
37055 address could not be retrieved.
37058 An empty reply indicates that @samp{qGetTIBAddr} is not supported by the stub.
37061 @item qL @var{startflag} @var{threadcount} @var{nextthread}
37062 Obtain thread information from RTOS. Where: @var{startflag} (one hex
37063 digit) is one to indicate the first query and zero to indicate a
37064 subsequent query; @var{threadcount} (two hex digits) is the maximum
37065 number of threads the response packet can contain; and @var{nextthread}
37066 (eight hex digits), for subsequent queries (@var{startflag} is zero), is
37067 returned in the response as @var{argthread}.
37069 Don't use this packet; use the @samp{qfThreadInfo} query instead (see above).
37073 @item qM @var{count} @var{done} @var{argthread} @var{thread}@dots{}
37074 Where: @var{count} (two hex digits) is the number of threads being
37075 returned; @var{done} (one hex digit) is zero to indicate more threads
37076 and one indicates no further threads; @var{argthreadid} (eight hex
37077 digits) is @var{nextthread} from the request packet; @var{thread}@dots{}
37078 is a sequence of thread IDs from the target. @var{threadid} (eight hex
37079 digits). See @code{remote.c:parse_threadlist_response()}.
37083 @cindex section offsets, remote request
37084 @cindex @samp{qOffsets} packet
37085 Get section offsets that the target used when relocating the downloaded
37090 @item Text=@var{xxx};Data=@var{yyy}@r{[};Bss=@var{zzz}@r{]}
37091 Relocate the @code{Text} section by @var{xxx} from its original address.
37092 Relocate the @code{Data} section by @var{yyy} from its original address.
37093 If the object file format provides segment information (e.g.@: @sc{elf}
37094 @samp{PT_LOAD} program headers), @value{GDBN} will relocate entire
37095 segments by the supplied offsets.
37097 @emph{Note: while a @code{Bss} offset may be included in the response,
37098 @value{GDBN} ignores this and instead applies the @code{Data} offset
37099 to the @code{Bss} section.}
37101 @item TextSeg=@var{xxx}@r{[};DataSeg=@var{yyy}@r{]}
37102 Relocate the first segment of the object file, which conventionally
37103 contains program code, to a starting address of @var{xxx}. If
37104 @samp{DataSeg} is specified, relocate the second segment, which
37105 conventionally contains modifiable data, to a starting address of
37106 @var{yyy}. @value{GDBN} will report an error if the object file
37107 does not contain segment information, or does not contain at least
37108 as many segments as mentioned in the reply. Extra segments are
37109 kept at fixed offsets relative to the last relocated segment.
37112 @item qP @var{mode} @var{thread-id}
37113 @cindex thread information, remote request
37114 @cindex @samp{qP} packet
37115 Returns information on @var{thread-id}. Where: @var{mode} is a hex
37116 encoded 32 bit mode; @var{thread-id} is a thread ID
37117 (@pxref{thread-id syntax}).
37119 Don't use this packet; use the @samp{qThreadExtraInfo} query instead
37122 Reply: see @code{remote.c:remote_unpack_thread_info_response()}.
37126 @cindex non-stop mode, remote request
37127 @cindex @samp{QNonStop} packet
37129 Enter non-stop (@samp{QNonStop:1}) or all-stop (@samp{QNonStop:0}) mode.
37130 @xref{Remote Non-Stop}, for more information.
37135 The request succeeded.
37138 An error occurred. @var{nn} are hex digits.
37141 An empty reply indicates that @samp{QNonStop} is not supported by
37145 This packet is not probed by default; the remote stub must request it,
37146 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37147 Use of this packet is controlled by the @code{set non-stop} command;
37148 @pxref{Non-Stop Mode}.
37150 @item QPassSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37151 @cindex pass signals to inferior, remote request
37152 @cindex @samp{QPassSignals} packet
37153 @anchor{QPassSignals}
37154 Each listed @var{signal} should be passed directly to the inferior process.
37155 Signals are numbered identically to continue packets and stop replies
37156 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37157 strictly greater than the previous item. These signals do not need to stop
37158 the inferior, or be reported to @value{GDBN}. All other signals should be
37159 reported to @value{GDBN}. Multiple @samp{QPassSignals} packets do not
37160 combine; any earlier @samp{QPassSignals} list is completely replaced by the
37161 new list. This packet improves performance when using @samp{handle
37162 @var{signal} nostop noprint pass}.
37167 The request succeeded.
37170 An error occurred. @var{nn} are hex digits.
37173 An empty reply indicates that @samp{QPassSignals} is not supported by
37177 Use of this packet is controlled by the @code{set remote pass-signals}
37178 command (@pxref{Remote Configuration, set remote pass-signals}).
37179 This packet is not probed by default; the remote stub must request it,
37180 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37182 @item QProgramSignals: @var{signal} @r{[};@var{signal}@r{]}@dots{}
37183 @cindex signals the inferior may see, remote request
37184 @cindex @samp{QProgramSignals} packet
37185 @anchor{QProgramSignals}
37186 Each listed @var{signal} may be delivered to the inferior process.
37187 Others should be silently discarded.
37189 In some cases, the remote stub may need to decide whether to deliver a
37190 signal to the program or not without @value{GDBN} involvement. One
37191 example of that is while detaching --- the program's threads may have
37192 stopped for signals that haven't yet had a chance of being reported to
37193 @value{GDBN}, and so the remote stub can use the signal list specified
37194 by this packet to know whether to deliver or ignore those pending
37197 This does not influence whether to deliver a signal as requested by a
37198 resumption packet (@pxref{vCont packet}).
37200 Signals are numbered identically to continue packets and stop replies
37201 (@pxref{Stop Reply Packets}). Each @var{signal} list item should be
37202 strictly greater than the previous item. Multiple
37203 @samp{QProgramSignals} packets do not combine; any earlier
37204 @samp{QProgramSignals} list is completely replaced by the new list.
37209 The request succeeded.
37212 An error occurred. @var{nn} are hex digits.
37215 An empty reply indicates that @samp{QProgramSignals} is not supported
37219 Use of this packet is controlled by the @code{set remote program-signals}
37220 command (@pxref{Remote Configuration, set remote program-signals}).
37221 This packet is not probed by default; the remote stub must request it,
37222 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37224 @item qRcmd,@var{command}
37225 @cindex execute remote command, remote request
37226 @cindex @samp{qRcmd} packet
37227 @var{command} (hex encoded) is passed to the local interpreter for
37228 execution. Invalid commands should be reported using the output
37229 string. Before the final result packet, the target may also respond
37230 with a number of intermediate @samp{O@var{output}} console output
37231 packets. @emph{Implementors should note that providing access to a
37232 stubs's interpreter may have security implications}.
37237 A command response with no output.
37239 A command response with the hex encoded output string @var{OUTPUT}.
37241 Indicate a badly formed request.
37243 An empty reply indicates that @samp{qRcmd} is not recognized.
37246 (Note that the @code{qRcmd} packet's name is separated from the
37247 command by a @samp{,}, not a @samp{:}, contrary to the naming
37248 conventions above. Please don't use this packet as a model for new
37251 @item qSearch:memory:@var{address};@var{length};@var{search-pattern}
37252 @cindex searching memory, in remote debugging
37253 @cindex @samp{qSearch:memory} packet
37254 @anchor{qSearch memory}
37255 Search @var{length} bytes at @var{address} for @var{search-pattern}.
37256 @var{address} and @var{length} are encoded in hex.
37257 @var{search-pattern} is a sequence of bytes, hex encoded.
37262 The pattern was not found.
37264 The pattern was found at @var{address}.
37266 A badly formed request or an error was encountered while searching memory.
37268 An empty reply indicates that @samp{qSearch:memory} is not recognized.
37271 @item QStartNoAckMode
37272 @cindex @samp{QStartNoAckMode} packet
37273 @anchor{QStartNoAckMode}
37274 Request that the remote stub disable the normal @samp{+}/@samp{-}
37275 protocol acknowledgments (@pxref{Packet Acknowledgment}).
37280 The stub has switched to no-acknowledgment mode.
37281 @value{GDBN} acknowledges this reponse,
37282 but neither the stub nor @value{GDBN} shall send or expect further
37283 @samp{+}/@samp{-} acknowledgments in the current connection.
37285 An empty reply indicates that the stub does not support no-acknowledgment mode.
37288 @item qSupported @r{[}:@var{gdbfeature} @r{[};@var{gdbfeature}@r{]}@dots{} @r{]}
37289 @cindex supported packets, remote query
37290 @cindex features of the remote protocol
37291 @cindex @samp{qSupported} packet
37292 @anchor{qSupported}
37293 Tell the remote stub about features supported by @value{GDBN}, and
37294 query the stub for features it supports. This packet allows
37295 @value{GDBN} and the remote stub to take advantage of each others'
37296 features. @samp{qSupported} also consolidates multiple feature probes
37297 at startup, to improve @value{GDBN} performance---a single larger
37298 packet performs better than multiple smaller probe packets on
37299 high-latency links. Some features may enable behavior which must not
37300 be on by default, e.g.@: because it would confuse older clients or
37301 stubs. Other features may describe packets which could be
37302 automatically probed for, but are not. These features must be
37303 reported before @value{GDBN} will use them. This ``default
37304 unsupported'' behavior is not appropriate for all packets, but it
37305 helps to keep the initial connection time under control with new
37306 versions of @value{GDBN} which support increasing numbers of packets.
37310 @item @var{stubfeature} @r{[};@var{stubfeature}@r{]}@dots{}
37311 The stub supports or does not support each returned @var{stubfeature},
37312 depending on the form of each @var{stubfeature} (see below for the
37315 An empty reply indicates that @samp{qSupported} is not recognized,
37316 or that no features needed to be reported to @value{GDBN}.
37319 The allowed forms for each feature (either a @var{gdbfeature} in the
37320 @samp{qSupported} packet, or a @var{stubfeature} in the response)
37324 @item @var{name}=@var{value}
37325 The remote protocol feature @var{name} is supported, and associated
37326 with the specified @var{value}. The format of @var{value} depends
37327 on the feature, but it must not include a semicolon.
37329 The remote protocol feature @var{name} is supported, and does not
37330 need an associated value.
37332 The remote protocol feature @var{name} is not supported.
37334 The remote protocol feature @var{name} may be supported, and
37335 @value{GDBN} should auto-detect support in some other way when it is
37336 needed. This form will not be used for @var{gdbfeature} notifications,
37337 but may be used for @var{stubfeature} responses.
37340 Whenever the stub receives a @samp{qSupported} request, the
37341 supplied set of @value{GDBN} features should override any previous
37342 request. This allows @value{GDBN} to put the stub in a known
37343 state, even if the stub had previously been communicating with
37344 a different version of @value{GDBN}.
37346 The following values of @var{gdbfeature} (for the packet sent by @value{GDBN})
37351 This feature indicates whether @value{GDBN} supports multiprocess
37352 extensions to the remote protocol. @value{GDBN} does not use such
37353 extensions unless the stub also reports that it supports them by
37354 including @samp{multiprocess+} in its @samp{qSupported} reply.
37355 @xref{multiprocess extensions}, for details.
37358 This feature indicates that @value{GDBN} supports the XML target
37359 description. If the stub sees @samp{xmlRegisters=} with target
37360 specific strings separated by a comma, it will report register
37364 This feature indicates whether @value{GDBN} supports the
37365 @samp{qRelocInsn} packet (@pxref{Tracepoint Packets,,Relocate
37366 instruction reply packet}).
37369 Stubs should ignore any unknown values for
37370 @var{gdbfeature}. Any @value{GDBN} which sends a @samp{qSupported}
37371 packet supports receiving packets of unlimited length (earlier
37372 versions of @value{GDBN} may reject overly long responses). Additional values
37373 for @var{gdbfeature} may be defined in the future to let the stub take
37374 advantage of new features in @value{GDBN}, e.g.@: incompatible
37375 improvements in the remote protocol---the @samp{multiprocess} feature is
37376 an example of such a feature. The stub's reply should be independent
37377 of the @var{gdbfeature} entries sent by @value{GDBN}; first @value{GDBN}
37378 describes all the features it supports, and then the stub replies with
37379 all the features it supports.
37381 Similarly, @value{GDBN} will silently ignore unrecognized stub feature
37382 responses, as long as each response uses one of the standard forms.
37384 Some features are flags. A stub which supports a flag feature
37385 should respond with a @samp{+} form response. Other features
37386 require values, and the stub should respond with an @samp{=}
37389 Each feature has a default value, which @value{GDBN} will use if
37390 @samp{qSupported} is not available or if the feature is not mentioned
37391 in the @samp{qSupported} response. The default values are fixed; a
37392 stub is free to omit any feature responses that match the defaults.
37394 Not all features can be probed, but for those which can, the probing
37395 mechanism is useful: in some cases, a stub's internal
37396 architecture may not allow the protocol layer to know some information
37397 about the underlying target in advance. This is especially common in
37398 stubs which may be configured for multiple targets.
37400 These are the currently defined stub features and their properties:
37402 @multitable @columnfractions 0.35 0.2 0.12 0.2
37403 @c NOTE: The first row should be @headitem, but we do not yet require
37404 @c a new enough version of Texinfo (4.7) to use @headitem.
37406 @tab Value Required
37410 @item @samp{PacketSize}
37415 @item @samp{qXfer:auxv:read}
37420 @item @samp{qXfer:btrace:read}
37425 @item @samp{qXfer:features:read}
37430 @item @samp{qXfer:libraries:read}
37435 @item @samp{qXfer:memory-map:read}
37440 @item @samp{qXfer:sdata:read}
37445 @item @samp{qXfer:spu:read}
37450 @item @samp{qXfer:spu:write}
37455 @item @samp{qXfer:siginfo:read}
37460 @item @samp{qXfer:siginfo:write}
37465 @item @samp{qXfer:threads:read}
37470 @item @samp{qXfer:traceframe-info:read}
37475 @item @samp{qXfer:uib:read}
37480 @item @samp{qXfer:fdpic:read}
37485 @item @samp{Qbtrace:off}
37490 @item @samp{Qbtrace:bts}
37495 @item @samp{QNonStop}
37500 @item @samp{QPassSignals}
37505 @item @samp{QStartNoAckMode}
37510 @item @samp{multiprocess}
37515 @item @samp{ConditionalBreakpoints}
37520 @item @samp{ConditionalTracepoints}
37525 @item @samp{ReverseContinue}
37530 @item @samp{ReverseStep}
37535 @item @samp{TracepointSource}
37540 @item @samp{QAgent}
37545 @item @samp{QAllow}
37550 @item @samp{QDisableRandomization}
37555 @item @samp{EnableDisableTracepoints}
37560 @item @samp{QTBuffer:size}
37565 @item @samp{tracenz}
37570 @item @samp{BreakpointCommands}
37577 These are the currently defined stub features, in more detail:
37580 @cindex packet size, remote protocol
37581 @item PacketSize=@var{bytes}
37582 The remote stub can accept packets up to at least @var{bytes} in
37583 length. @value{GDBN} will send packets up to this size for bulk
37584 transfers, and will never send larger packets. This is a limit on the
37585 data characters in the packet, including the frame and checksum.
37586 There is no trailing NUL byte in a remote protocol packet; if the stub
37587 stores packets in a NUL-terminated format, it should allow an extra
37588 byte in its buffer for the NUL. If this stub feature is not supported,
37589 @value{GDBN} guesses based on the size of the @samp{g} packet response.
37591 @item qXfer:auxv:read
37592 The remote stub understands the @samp{qXfer:auxv:read} packet
37593 (@pxref{qXfer auxiliary vector read}).
37595 @item qXfer:btrace:read
37596 The remote stub understands the @samp{qXfer:btrace:read}
37597 packet (@pxref{qXfer btrace read}).
37599 @item qXfer:features:read
37600 The remote stub understands the @samp{qXfer:features:read} packet
37601 (@pxref{qXfer target description read}).
37603 @item qXfer:libraries:read
37604 The remote stub understands the @samp{qXfer:libraries:read} packet
37605 (@pxref{qXfer library list read}).
37607 @item qXfer:libraries-svr4:read
37608 The remote stub understands the @samp{qXfer:libraries-svr4:read} packet
37609 (@pxref{qXfer svr4 library list read}).
37611 @item qXfer:memory-map:read
37612 The remote stub understands the @samp{qXfer:memory-map:read} packet
37613 (@pxref{qXfer memory map read}).
37615 @item qXfer:sdata:read
37616 The remote stub understands the @samp{qXfer:sdata:read} packet
37617 (@pxref{qXfer sdata read}).
37619 @item qXfer:spu:read
37620 The remote stub understands the @samp{qXfer:spu:read} packet
37621 (@pxref{qXfer spu read}).
37623 @item qXfer:spu:write
37624 The remote stub understands the @samp{qXfer:spu:write} packet
37625 (@pxref{qXfer spu write}).
37627 @item qXfer:siginfo:read
37628 The remote stub understands the @samp{qXfer:siginfo:read} packet
37629 (@pxref{qXfer siginfo read}).
37631 @item qXfer:siginfo:write
37632 The remote stub understands the @samp{qXfer:siginfo:write} packet
37633 (@pxref{qXfer siginfo write}).
37635 @item qXfer:threads:read
37636 The remote stub understands the @samp{qXfer:threads:read} packet
37637 (@pxref{qXfer threads read}).
37639 @item qXfer:traceframe-info:read
37640 The remote stub understands the @samp{qXfer:traceframe-info:read}
37641 packet (@pxref{qXfer traceframe info read}).
37643 @item qXfer:uib:read
37644 The remote stub understands the @samp{qXfer:uib:read}
37645 packet (@pxref{qXfer unwind info block}).
37647 @item qXfer:fdpic:read
37648 The remote stub understands the @samp{qXfer:fdpic:read}
37649 packet (@pxref{qXfer fdpic loadmap read}).
37652 The remote stub understands the @samp{QNonStop} packet
37653 (@pxref{QNonStop}).
37656 The remote stub understands the @samp{QPassSignals} packet
37657 (@pxref{QPassSignals}).
37659 @item QStartNoAckMode
37660 The remote stub understands the @samp{QStartNoAckMode} packet and
37661 prefers to operate in no-acknowledgment mode. @xref{Packet Acknowledgment}.
37664 @anchor{multiprocess extensions}
37665 @cindex multiprocess extensions, in remote protocol
37666 The remote stub understands the multiprocess extensions to the remote
37667 protocol syntax. The multiprocess extensions affect the syntax of
37668 thread IDs in both packets and replies (@pxref{thread-id syntax}), and
37669 add process IDs to the @samp{D} packet and @samp{W} and @samp{X}
37670 replies. Note that reporting this feature indicates support for the
37671 syntactic extensions only, not that the stub necessarily supports
37672 debugging of more than one process at a time. The stub must not use
37673 multiprocess extensions in packet replies unless @value{GDBN} has also
37674 indicated it supports them in its @samp{qSupported} request.
37676 @item qXfer:osdata:read
37677 The remote stub understands the @samp{qXfer:osdata:read} packet
37678 ((@pxref{qXfer osdata read}).
37680 @item ConditionalBreakpoints
37681 The target accepts and implements evaluation of conditional expressions
37682 defined for breakpoints. The target will only report breakpoint triggers
37683 when such conditions are true (@pxref{Conditions, ,Break Conditions}).
37685 @item ConditionalTracepoints
37686 The remote stub accepts and implements conditional expressions defined
37687 for tracepoints (@pxref{Tracepoint Conditions}).
37689 @item ReverseContinue
37690 The remote stub accepts and implements the reverse continue packet
37694 The remote stub accepts and implements the reverse step packet
37697 @item TracepointSource
37698 The remote stub understands the @samp{QTDPsrc} packet that supplies
37699 the source form of tracepoint definitions.
37702 The remote stub understands the @samp{QAgent} packet.
37705 The remote stub understands the @samp{QAllow} packet.
37707 @item QDisableRandomization
37708 The remote stub understands the @samp{QDisableRandomization} packet.
37710 @item StaticTracepoint
37711 @cindex static tracepoints, in remote protocol
37712 The remote stub supports static tracepoints.
37714 @item InstallInTrace
37715 @anchor{install tracepoint in tracing}
37716 The remote stub supports installing tracepoint in tracing.
37718 @item EnableDisableTracepoints
37719 The remote stub supports the @samp{QTEnable} (@pxref{QTEnable}) and
37720 @samp{QTDisable} (@pxref{QTDisable}) packets that allow tracepoints
37721 to be enabled and disabled while a trace experiment is running.
37723 @item QTBuffer:size
37724 The remote stub supports the @samp{QTBuffer:size} (@pxref{QTBuffer-size})
37725 packet that allows to change the size of the trace buffer.
37728 @cindex string tracing, in remote protocol
37729 The remote stub supports the @samp{tracenz} bytecode for collecting strings.
37730 See @ref{Bytecode Descriptions} for details about the bytecode.
37732 @item BreakpointCommands
37733 @cindex breakpoint commands, in remote protocol
37734 The remote stub supports running a breakpoint's command list itself,
37735 rather than reporting the hit to @value{GDBN}.
37738 The remote stub understands the @samp{Qbtrace:off} packet.
37741 The remote stub understands the @samp{Qbtrace:bts} packet.
37746 @cindex symbol lookup, remote request
37747 @cindex @samp{qSymbol} packet
37748 Notify the target that @value{GDBN} is prepared to serve symbol lookup
37749 requests. Accept requests from the target for the values of symbols.
37754 The target does not need to look up any (more) symbols.
37755 @item qSymbol:@var{sym_name}
37756 The target requests the value of symbol @var{sym_name} (hex encoded).
37757 @value{GDBN} may provide the value by using the
37758 @samp{qSymbol:@var{sym_value}:@var{sym_name}} message, described
37762 @item qSymbol:@var{sym_value}:@var{sym_name}
37763 Set the value of @var{sym_name} to @var{sym_value}.
37765 @var{sym_name} (hex encoded) is the name of a symbol whose value the
37766 target has previously requested.
37768 @var{sym_value} (hex) is the value for symbol @var{sym_name}. If
37769 @value{GDBN} cannot supply a value for @var{sym_name}, then this field
37775 The target does not need to look up any (more) symbols.
37776 @item qSymbol:@var{sym_name}
37777 The target requests the value of a new symbol @var{sym_name} (hex
37778 encoded). @value{GDBN} will continue to supply the values of symbols
37779 (if available), until the target ceases to request them.
37784 @itemx QTDisconnected
37791 @itemx qTMinFTPILen
37793 @xref{Tracepoint Packets}.
37795 @item qThreadExtraInfo,@var{thread-id}
37796 @cindex thread attributes info, remote request
37797 @cindex @samp{qThreadExtraInfo} packet
37798 Obtain a printable string description of a thread's attributes from
37799 the target OS. @var{thread-id} is a thread ID;
37800 see @ref{thread-id syntax}. This
37801 string may contain anything that the target OS thinks is interesting
37802 for @value{GDBN} to tell the user about the thread. The string is
37803 displayed in @value{GDBN}'s @code{info threads} display. Some
37804 examples of possible thread extra info strings are @samp{Runnable}, or
37805 @samp{Blocked on Mutex}.
37809 @item @var{XX}@dots{}
37810 Where @samp{@var{XX}@dots{}} is a hex encoding of @sc{ascii} data,
37811 comprising the printable string containing the extra information about
37812 the thread's attributes.
37815 (Note that the @code{qThreadExtraInfo} packet's name is separated from
37816 the command by a @samp{,}, not a @samp{:}, contrary to the naming
37817 conventions above. Please don't use this packet as a model for new
37836 @xref{Tracepoint Packets}.
37838 @item qXfer:@var{object}:read:@var{annex}:@var{offset},@var{length}
37839 @cindex read special object, remote request
37840 @cindex @samp{qXfer} packet
37841 @anchor{qXfer read}
37842 Read uninterpreted bytes from the target's special data area
37843 identified by the keyword @var{object}. Request @var{length} bytes
37844 starting at @var{offset} bytes into the data. The content and
37845 encoding of @var{annex} is specific to @var{object}; it can supply
37846 additional details about what data to access.
37848 Here are the specific requests of this form defined so far. All
37849 @samp{qXfer:@var{object}:read:@dots{}} requests use the same reply
37850 formats, listed below.
37853 @item qXfer:auxv:read::@var{offset},@var{length}
37854 @anchor{qXfer auxiliary vector read}
37855 Access the target's @dfn{auxiliary vector}. @xref{OS Information,
37856 auxiliary vector}. Note @var{annex} must be empty.
37858 This packet is not probed by default; the remote stub must request it,
37859 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37861 @item qXfer:btrace:read:@var{annex}:@var{offset},@var{length}
37862 @anchor{qXfer btrace read}
37864 Return a description of the current branch trace.
37865 @xref{Branch Trace Format}. The annex part of the generic @samp{qXfer}
37866 packet may have one of the following values:
37870 Returns all available branch trace.
37873 Returns all available branch trace if the branch trace changed since
37874 the last read request.
37877 This packet is not probed by default; the remote stub must request it
37878 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37880 @item qXfer:features:read:@var{annex}:@var{offset},@var{length}
37881 @anchor{qXfer target description read}
37882 Access the @dfn{target description}. @xref{Target Descriptions}. The
37883 annex specifies which XML document to access. The main description is
37884 always loaded from the @samp{target.xml} annex.
37886 This packet is not probed by default; the remote stub must request it,
37887 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37889 @item qXfer:libraries:read:@var{annex}:@var{offset},@var{length}
37890 @anchor{qXfer library list read}
37891 Access the target's list of loaded libraries. @xref{Library List Format}.
37892 The annex part of the generic @samp{qXfer} packet must be empty
37893 (@pxref{qXfer read}).
37895 Targets which maintain a list of libraries in the program's memory do
37896 not need to implement this packet; it is designed for platforms where
37897 the operating system manages the list of loaded libraries.
37899 This packet is not probed by default; the remote stub must request it,
37900 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37902 @item qXfer:libraries-svr4:read:@var{annex}:@var{offset},@var{length}
37903 @anchor{qXfer svr4 library list read}
37904 Access the target's list of loaded libraries when the target is an SVR4
37905 platform. @xref{Library List Format for SVR4 Targets}. The annex part
37906 of the generic @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37908 This packet is optional for better performance on SVR4 targets.
37909 @value{GDBN} uses memory read packets to read the SVR4 library list otherwise.
37911 This packet is not probed by default; the remote stub must request it,
37912 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37914 @item qXfer:memory-map:read::@var{offset},@var{length}
37915 @anchor{qXfer memory map read}
37916 Access the target's @dfn{memory-map}. @xref{Memory Map Format}. The
37917 annex part of the generic @samp{qXfer} packet must be empty
37918 (@pxref{qXfer read}).
37920 This packet is not probed by default; the remote stub must request it,
37921 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37923 @item qXfer:sdata:read::@var{offset},@var{length}
37924 @anchor{qXfer sdata read}
37926 Read contents of the extra collected static tracepoint marker
37927 information. The annex part of the generic @samp{qXfer} packet must
37928 be empty (@pxref{qXfer read}). @xref{Tracepoint Actions,,Tracepoint
37931 This packet is not probed by default; the remote stub must request it,
37932 by supplying an appropriate @samp{qSupported} response
37933 (@pxref{qSupported}).
37935 @item qXfer:siginfo:read::@var{offset},@var{length}
37936 @anchor{qXfer siginfo read}
37937 Read contents of the extra signal information on the target
37938 system. The annex part of the generic @samp{qXfer} packet must be
37939 empty (@pxref{qXfer read}).
37941 This packet is not probed by default; the remote stub must request it,
37942 by supplying an appropriate @samp{qSupported} response
37943 (@pxref{qSupported}).
37945 @item qXfer:spu:read:@var{annex}:@var{offset},@var{length}
37946 @anchor{qXfer spu read}
37947 Read contents of an @code{spufs} file on the target system. The
37948 annex specifies which file to read; it must be of the form
37949 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
37950 in the target process, and @var{name} identifes the @code{spufs} file
37951 in that context to be accessed.
37953 This packet is not probed by default; the remote stub must request it,
37954 by supplying an appropriate @samp{qSupported} response
37955 (@pxref{qSupported}).
37957 @item qXfer:threads:read::@var{offset},@var{length}
37958 @anchor{qXfer threads read}
37959 Access the list of threads on target. @xref{Thread List Format}. The
37960 annex part of the generic @samp{qXfer} packet must be empty
37961 (@pxref{qXfer read}).
37963 This packet is not probed by default; the remote stub must request it,
37964 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37966 @item qXfer:traceframe-info:read::@var{offset},@var{length}
37967 @anchor{qXfer traceframe info read}
37969 Return a description of the current traceframe's contents.
37970 @xref{Traceframe Info Format}. The annex part of the generic
37971 @samp{qXfer} packet must be empty (@pxref{qXfer read}).
37973 This packet is not probed by default; the remote stub must request it,
37974 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37976 @item qXfer:uib:read:@var{pc}:@var{offset},@var{length}
37977 @anchor{qXfer unwind info block}
37979 Return the unwind information block for @var{pc}. This packet is used
37980 on OpenVMS/ia64 to ask the kernel unwind information.
37982 This packet is not probed by default.
37984 @item qXfer:fdpic:read:@var{annex}:@var{offset},@var{length}
37985 @anchor{qXfer fdpic loadmap read}
37986 Read contents of @code{loadmap}s on the target system. The
37987 annex, either @samp{exec} or @samp{interp}, specifies which @code{loadmap},
37988 executable @code{loadmap} or interpreter @code{loadmap} to read.
37990 This packet is not probed by default; the remote stub must request it,
37991 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
37993 @item qXfer:osdata:read::@var{offset},@var{length}
37994 @anchor{qXfer osdata read}
37995 Access the target's @dfn{operating system information}.
37996 @xref{Operating System Information}.
38003 Data @var{data} (@pxref{Binary Data}) has been read from the
38004 target. There may be more data at a higher address (although
38005 it is permitted to return @samp{m} even for the last valid
38006 block of data, as long as at least one byte of data was read).
38007 @var{data} may have fewer bytes than the @var{length} in the
38011 Data @var{data} (@pxref{Binary Data}) has been read from the target.
38012 There is no more data to be read. @var{data} may have fewer bytes
38013 than the @var{length} in the request.
38016 The @var{offset} in the request is at the end of the data.
38017 There is no more data to be read.
38020 The request was malformed, or @var{annex} was invalid.
38023 The offset was invalid, or there was an error encountered reading the data.
38024 @var{nn} is a hex-encoded @code{errno} value.
38027 An empty reply indicates the @var{object} string was not recognized by
38028 the stub, or that the object does not support reading.
38031 @item qXfer:@var{object}:write:@var{annex}:@var{offset}:@var{data}@dots{}
38032 @cindex write data into object, remote request
38033 @anchor{qXfer write}
38034 Write uninterpreted bytes into the target's special data area
38035 identified by the keyword @var{object}, starting at @var{offset} bytes
38036 into the data. @var{data}@dots{} is the binary-encoded data
38037 (@pxref{Binary Data}) to be written. The content and encoding of @var{annex}
38038 is specific to @var{object}; it can supply additional details about what data
38041 Here are the specific requests of this form defined so far. All
38042 @samp{qXfer:@var{object}:write:@dots{}} requests use the same reply
38043 formats, listed below.
38046 @item qXfer:siginfo:write::@var{offset}:@var{data}@dots{}
38047 @anchor{qXfer siginfo write}
38048 Write @var{data} to the extra signal information on the target system.
38049 The annex part of the generic @samp{qXfer} packet must be
38050 empty (@pxref{qXfer write}).
38052 This packet is not probed by default; the remote stub must request it,
38053 by supplying an appropriate @samp{qSupported} response
38054 (@pxref{qSupported}).
38056 @item qXfer:spu:write:@var{annex}:@var{offset}:@var{data}@dots{}
38057 @anchor{qXfer spu write}
38058 Write @var{data} to an @code{spufs} file on the target system. The
38059 annex specifies which file to write; it must be of the form
38060 @file{@var{id}/@var{name}}, where @var{id} specifies an SPU context ID
38061 in the target process, and @var{name} identifes the @code{spufs} file
38062 in that context to be accessed.
38064 This packet is not probed by default; the remote stub must request it,
38065 by supplying an appropriate @samp{qSupported} response (@pxref{qSupported}).
38071 @var{nn} (hex encoded) is the number of bytes written.
38072 This may be fewer bytes than supplied in the request.
38075 The request was malformed, or @var{annex} was invalid.
38078 The offset was invalid, or there was an error encountered writing the data.
38079 @var{nn} is a hex-encoded @code{errno} value.
38082 An empty reply indicates the @var{object} string was not
38083 recognized by the stub, or that the object does not support writing.
38086 @item qXfer:@var{object}:@var{operation}:@dots{}
38087 Requests of this form may be added in the future. When a stub does
38088 not recognize the @var{object} keyword, or its support for
38089 @var{object} does not recognize the @var{operation} keyword, the stub
38090 must respond with an empty packet.
38092 @item qAttached:@var{pid}
38093 @cindex query attached, remote request
38094 @cindex @samp{qAttached} packet
38095 Return an indication of whether the remote server attached to an
38096 existing process or created a new process. When the multiprocess
38097 protocol extensions are supported (@pxref{multiprocess extensions}),
38098 @var{pid} is an integer in hexadecimal format identifying the target
38099 process. Otherwise, @value{GDBN} will omit the @var{pid} field and
38100 the query packet will be simplified as @samp{qAttached}.
38102 This query is used, for example, to know whether the remote process
38103 should be detached or killed when a @value{GDBN} session is ended with
38104 the @code{quit} command.
38109 The remote server attached to an existing process.
38111 The remote server created a new process.
38113 A badly formed request or an error was encountered.
38117 Enable branch tracing for the current thread using bts tracing.
38122 Branch tracing has been enabled.
38124 A badly formed request or an error was encountered.
38128 Disable branch tracing for the current thread.
38133 Branch tracing has been disabled.
38135 A badly formed request or an error was encountered.
38140 @node Architecture-Specific Protocol Details
38141 @section Architecture-Specific Protocol Details
38143 This section describes how the remote protocol is applied to specific
38144 target architectures. Also see @ref{Standard Target Features}, for
38145 details of XML target descriptions for each architecture.
38148 * ARM-Specific Protocol Details::
38149 * MIPS-Specific Protocol Details::
38152 @node ARM-Specific Protocol Details
38153 @subsection @acronym{ARM}-specific Protocol Details
38156 * ARM Breakpoint Kinds::
38159 @node ARM Breakpoint Kinds
38160 @subsubsection @acronym{ARM} Breakpoint Kinds
38161 @cindex breakpoint kinds, @acronym{ARM}
38163 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38168 16-bit Thumb mode breakpoint.
38171 32-bit Thumb mode (Thumb-2) breakpoint.
38174 32-bit @acronym{ARM} mode breakpoint.
38178 @node MIPS-Specific Protocol Details
38179 @subsection @acronym{MIPS}-specific Protocol Details
38182 * MIPS Register packet Format::
38183 * MIPS Breakpoint Kinds::
38186 @node MIPS Register packet Format
38187 @subsubsection @acronym{MIPS} Register Packet Format
38188 @cindex register packet format, @acronym{MIPS}
38190 The following @code{g}/@code{G} packets have previously been defined.
38191 In the below, some thirty-two bit registers are transferred as
38192 sixty-four bits. Those registers should be zero/sign extended (which?)
38193 to fill the space allocated. Register bytes are transferred in target
38194 byte order. The two nibbles within a register byte are transferred
38195 most-significant -- least-significant.
38200 All registers are transferred as thirty-two bit quantities in the order:
38201 32 general-purpose; sr; lo; hi; bad; cause; pc; 32 floating-point
38202 registers; fsr; fir; fp.
38205 All registers are transferred as sixty-four bit quantities (including
38206 thirty-two bit registers such as @code{sr}). The ordering is the same
38211 @node MIPS Breakpoint Kinds
38212 @subsubsection @acronym{MIPS} Breakpoint Kinds
38213 @cindex breakpoint kinds, @acronym{MIPS}
38215 These breakpoint kinds are defined for the @samp{Z0} and @samp{Z1} packets.
38220 16-bit @acronym{MIPS16} mode breakpoint.
38223 16-bit @acronym{microMIPS} mode breakpoint.
38226 32-bit standard @acronym{MIPS} mode breakpoint.
38229 32-bit @acronym{microMIPS} mode breakpoint.
38233 @node Tracepoint Packets
38234 @section Tracepoint Packets
38235 @cindex tracepoint packets
38236 @cindex packets, tracepoint
38238 Here we describe the packets @value{GDBN} uses to implement
38239 tracepoints (@pxref{Tracepoints}).
38243 @item QTDP:@var{n}:@var{addr}:@var{ena}:@var{step}:@var{pass}[:F@var{flen}][:X@var{len},@var{bytes}]@r{[}-@r{]}
38244 @cindex @samp{QTDP} packet
38245 Create a new tracepoint, number @var{n}, at @var{addr}. If @var{ena}
38246 is @samp{E}, then the tracepoint is enabled; if it is @samp{D}, then
38247 the tracepoint is disabled. @var{step} is the tracepoint's step
38248 count, and @var{pass} is its pass count. If an @samp{F} is present,
38249 then the tracepoint is to be a fast tracepoint, and the @var{flen} is
38250 the number of bytes that the target should copy elsewhere to make room
38251 for the tracepoint. If an @samp{X} is present, it introduces a
38252 tracepoint condition, which consists of a hexadecimal length, followed
38253 by a comma and hex-encoded bytes, in a manner similar to action
38254 encodings as described below. If the trailing @samp{-} is present,
38255 further @samp{QTDP} packets will follow to specify this tracepoint's
38261 The packet was understood and carried out.
38263 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38265 The packet was not recognized.
38268 @item QTDP:-@var{n}:@var{addr}:@r{[}S@r{]}@var{action}@dots{}@r{[}-@r{]}
38269 Define actions to be taken when a tracepoint is hit. @var{n} and
38270 @var{addr} must be the same as in the initial @samp{QTDP} packet for
38271 this tracepoint. This packet may only be sent immediately after
38272 another @samp{QTDP} packet that ended with a @samp{-}. If the
38273 trailing @samp{-} is present, further @samp{QTDP} packets will follow,
38274 specifying more actions for this tracepoint.
38276 In the series of action packets for a given tracepoint, at most one
38277 can have an @samp{S} before its first @var{action}. If such a packet
38278 is sent, it and the following packets define ``while-stepping''
38279 actions. Any prior packets define ordinary actions --- that is, those
38280 taken when the tracepoint is first hit. If no action packet has an
38281 @samp{S}, then all the packets in the series specify ordinary
38282 tracepoint actions.
38284 The @samp{@var{action}@dots{}} portion of the packet is a series of
38285 actions, concatenated without separators. Each action has one of the
38291 Collect the registers whose bits are set in @var{mask}. @var{mask} is
38292 a hexadecimal number whose @var{i}'th bit is set if register number
38293 @var{i} should be collected. (The least significant bit is numbered
38294 zero.) Note that @var{mask} may be any number of digits long; it may
38295 not fit in a 32-bit word.
38297 @item M @var{basereg},@var{offset},@var{len}
38298 Collect @var{len} bytes of memory starting at the address in register
38299 number @var{basereg}, plus @var{offset}. If @var{basereg} is
38300 @samp{-1}, then the range has a fixed address: @var{offset} is the
38301 address of the lowest byte to collect. The @var{basereg},
38302 @var{offset}, and @var{len} parameters are all unsigned hexadecimal
38303 values (the @samp{-1} value for @var{basereg} is a special case).
38305 @item X @var{len},@var{expr}
38306 Evaluate @var{expr}, whose length is @var{len}, and collect memory as
38307 it directs. @var{expr} is an agent expression, as described in
38308 @ref{Agent Expressions}. Each byte of the expression is encoded as a
38309 two-digit hex number in the packet; @var{len} is the number of bytes
38310 in the expression (and thus one-half the number of hex digits in the
38315 Any number of actions may be packed together in a single @samp{QTDP}
38316 packet, as long as the packet does not exceed the maximum packet
38317 length (400 bytes, for many stubs). There may be only one @samp{R}
38318 action per tracepoint, and it must precede any @samp{M} or @samp{X}
38319 actions. Any registers referred to by @samp{M} and @samp{X} actions
38320 must be collected by a preceding @samp{R} action. (The
38321 ``while-stepping'' actions are treated as if they were attached to a
38322 separate tracepoint, as far as these restrictions are concerned.)
38327 The packet was understood and carried out.
38329 @xref{Tracepoint Packets,,Relocate instruction reply packet}.
38331 The packet was not recognized.
38334 @item QTDPsrc:@var{n}:@var{addr}:@var{type}:@var{start}:@var{slen}:@var{bytes}
38335 @cindex @samp{QTDPsrc} packet
38336 Specify a source string of tracepoint @var{n} at address @var{addr}.
38337 This is useful to get accurate reproduction of the tracepoints
38338 originally downloaded at the beginning of the trace run. @var{type}
38339 is the name of the tracepoint part, such as @samp{cond} for the
38340 tracepoint's conditional expression (see below for a list of types), while
38341 @var{bytes} is the string, encoded in hexadecimal.
38343 @var{start} is the offset of the @var{bytes} within the overall source
38344 string, while @var{slen} is the total length of the source string.
38345 This is intended for handling source strings that are longer than will
38346 fit in a single packet.
38347 @c Add detailed example when this info is moved into a dedicated
38348 @c tracepoint descriptions section.
38350 The available string types are @samp{at} for the location,
38351 @samp{cond} for the conditional, and @samp{cmd} for an action command.
38352 @value{GDBN} sends a separate packet for each command in the action
38353 list, in the same order in which the commands are stored in the list.
38355 The target does not need to do anything with source strings except
38356 report them back as part of the replies to the @samp{qTfP}/@samp{qTsP}
38359 Although this packet is optional, and @value{GDBN} will only send it
38360 if the target replies with @samp{TracepointSource} @xref{General
38361 Query Packets}, it makes both disconnected tracing and trace files
38362 much easier to use. Otherwise the user must be careful that the
38363 tracepoints in effect while looking at trace frames are identical to
38364 the ones in effect during the trace run; even a small discrepancy
38365 could cause @samp{tdump} not to work, or a particular trace frame not
38368 @item QTDV:@var{n}:@var{value}
38369 @cindex define trace state variable, remote request
38370 @cindex @samp{QTDV} packet
38371 Create a new trace state variable, number @var{n}, with an initial
38372 value of @var{value}, which is a 64-bit signed integer. Both @var{n}
38373 and @var{value} are encoded as hexadecimal values. @value{GDBN} has
38374 the option of not using this packet for initial values of zero; the
38375 target should simply create the trace state variables as they are
38376 mentioned in expressions.
38378 @item QTFrame:@var{n}
38379 @cindex @samp{QTFrame} packet
38380 Select the @var{n}'th tracepoint frame from the buffer, and use the
38381 register and memory contents recorded there to answer subsequent
38382 request packets from @value{GDBN}.
38384 A successful reply from the stub indicates that the stub has found the
38385 requested frame. The response is a series of parts, concatenated
38386 without separators, describing the frame we selected. Each part has
38387 one of the following forms:
38391 The selected frame is number @var{n} in the trace frame buffer;
38392 @var{f} is a hexadecimal number. If @var{f} is @samp{-1}, then there
38393 was no frame matching the criteria in the request packet.
38396 The selected trace frame records a hit of tracepoint number @var{t};
38397 @var{t} is a hexadecimal number.
38401 @item QTFrame:pc:@var{addr}
38402 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38403 currently selected frame whose PC is @var{addr};
38404 @var{addr} is a hexadecimal number.
38406 @item QTFrame:tdp:@var{t}
38407 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38408 currently selected frame that is a hit of tracepoint @var{t}; @var{t}
38409 is a hexadecimal number.
38411 @item QTFrame:range:@var{start}:@var{end}
38412 Like @samp{QTFrame:@var{n}}, but select the first tracepoint frame after the
38413 currently selected frame whose PC is between @var{start} (inclusive)
38414 and @var{end} (inclusive); @var{start} and @var{end} are hexadecimal
38417 @item QTFrame:outside:@var{start}:@var{end}
38418 Like @samp{QTFrame:range:@var{start}:@var{end}}, but select the first
38419 frame @emph{outside} the given range of addresses (exclusive).
38422 @cindex @samp{qTMinFTPILen} packet
38423 This packet requests the minimum length of instruction at which a fast
38424 tracepoint (@pxref{Set Tracepoints}) may be placed. For instance, on
38425 the 32-bit x86 architecture, it is possible to use a 4-byte jump, but
38426 it depends on the target system being able to create trampolines in
38427 the first 64K of memory, which might or might not be possible for that
38428 system. So the reply to this packet will be 4 if it is able to
38435 The minimum instruction length is currently unknown.
38437 The minimum instruction length is @var{length}, where @var{length} is greater
38438 or equal to 1. @var{length} is a hexadecimal number. A reply of 1 means
38439 that a fast tracepoint may be placed on any instruction regardless of size.
38441 An error has occurred.
38443 An empty reply indicates that the request is not supported by the stub.
38447 @cindex @samp{QTStart} packet
38448 Begin the tracepoint experiment. Begin collecting data from
38449 tracepoint hits in the trace frame buffer. This packet supports the
38450 @samp{qRelocInsn} reply (@pxref{Tracepoint Packets,,Relocate
38451 instruction reply packet}).
38454 @cindex @samp{QTStop} packet
38455 End the tracepoint experiment. Stop collecting trace frames.
38457 @item QTEnable:@var{n}:@var{addr}
38459 @cindex @samp{QTEnable} packet
38460 Enable tracepoint @var{n} at address @var{addr} in a started tracepoint
38461 experiment. If the tracepoint was previously disabled, then collection
38462 of data from it will resume.
38464 @item QTDisable:@var{n}:@var{addr}
38466 @cindex @samp{QTDisable} packet
38467 Disable tracepoint @var{n} at address @var{addr} in a started tracepoint
38468 experiment. No more data will be collected from the tracepoint unless
38469 @samp{QTEnable:@var{n}:@var{addr}} is subsequently issued.
38472 @cindex @samp{QTinit} packet
38473 Clear the table of tracepoints, and empty the trace frame buffer.
38475 @item QTro:@var{start1},@var{end1}:@var{start2},@var{end2}:@dots{}
38476 @cindex @samp{QTro} packet
38477 Establish the given ranges of memory as ``transparent''. The stub
38478 will answer requests for these ranges from memory's current contents,
38479 if they were not collected as part of the tracepoint hit.
38481 @value{GDBN} uses this to mark read-only regions of memory, like those
38482 containing program code. Since these areas never change, they should
38483 still have the same contents they did when the tracepoint was hit, so
38484 there's no reason for the stub to refuse to provide their contents.
38486 @item QTDisconnected:@var{value}
38487 @cindex @samp{QTDisconnected} packet
38488 Set the choice to what to do with the tracing run when @value{GDBN}
38489 disconnects from the target. A @var{value} of 1 directs the target to
38490 continue the tracing run, while 0 tells the target to stop tracing if
38491 @value{GDBN} is no longer in the picture.
38494 @cindex @samp{qTStatus} packet
38495 Ask the stub if there is a trace experiment running right now.
38497 The reply has the form:
38501 @item T@var{running}@r{[};@var{field}@r{]}@dots{}
38502 @var{running} is a single digit @code{1} if the trace is presently
38503 running, or @code{0} if not. It is followed by semicolon-separated
38504 optional fields that an agent may use to report additional status.
38508 If the trace is not running, the agent may report any of several
38509 explanations as one of the optional fields:
38514 No trace has been run yet.
38516 @item tstop[:@var{text}]:0
38517 The trace was stopped by a user-originated stop command. The optional
38518 @var{text} field is a user-supplied string supplied as part of the
38519 stop command (for instance, an explanation of why the trace was
38520 stopped manually). It is hex-encoded.
38523 The trace stopped because the trace buffer filled up.
38525 @item tdisconnected:0
38526 The trace stopped because @value{GDBN} disconnected from the target.
38528 @item tpasscount:@var{tpnum}
38529 The trace stopped because tracepoint @var{tpnum} exceeded its pass count.
38531 @item terror:@var{text}:@var{tpnum}
38532 The trace stopped because tracepoint @var{tpnum} had an error. The
38533 string @var{text} is available to describe the nature of the error
38534 (for instance, a divide by zero in the condition expression).
38535 @var{text} is hex encoded.
38538 The trace stopped for some other reason.
38542 Additional optional fields supply statistical and other information.
38543 Although not required, they are extremely useful for users monitoring
38544 the progress of a trace run. If a trace has stopped, and these
38545 numbers are reported, they must reflect the state of the just-stopped
38550 @item tframes:@var{n}
38551 The number of trace frames in the buffer.
38553 @item tcreated:@var{n}
38554 The total number of trace frames created during the run. This may
38555 be larger than the trace frame count, if the buffer is circular.
38557 @item tsize:@var{n}
38558 The total size of the trace buffer, in bytes.
38560 @item tfree:@var{n}
38561 The number of bytes still unused in the buffer.
38563 @item circular:@var{n}
38564 The value of the circular trace buffer flag. @code{1} means that the
38565 trace buffer is circular and old trace frames will be discarded if
38566 necessary to make room, @code{0} means that the trace buffer is linear
38569 @item disconn:@var{n}
38570 The value of the disconnected tracing flag. @code{1} means that
38571 tracing will continue after @value{GDBN} disconnects, @code{0} means
38572 that the trace run will stop.
38576 @item qTP:@var{tp}:@var{addr}
38577 @cindex tracepoint status, remote request
38578 @cindex @samp{qTP} packet
38579 Ask the stub for the current state of tracepoint number @var{tp} at
38580 address @var{addr}.
38584 @item V@var{hits}:@var{usage}
38585 The tracepoint has been hit @var{hits} times so far during the trace
38586 run, and accounts for @var{usage} in the trace buffer. Note that
38587 @code{while-stepping} steps are not counted as separate hits, but the
38588 steps' space consumption is added into the usage number.
38592 @item qTV:@var{var}
38593 @cindex trace state variable value, remote request
38594 @cindex @samp{qTV} packet
38595 Ask the stub for the value of the trace state variable number @var{var}.
38600 The value of the variable is @var{value}. This will be the current
38601 value of the variable if the user is examining a running target, or a
38602 saved value if the variable was collected in the trace frame that the
38603 user is looking at. Note that multiple requests may result in
38604 different reply values, such as when requesting values while the
38605 program is running.
38608 The value of the variable is unknown. This would occur, for example,
38609 if the user is examining a trace frame in which the requested variable
38614 @cindex @samp{qTfP} packet
38616 @cindex @samp{qTsP} packet
38617 These packets request data about tracepoints that are being used by
38618 the target. @value{GDBN} sends @code{qTfP} to get the first piece
38619 of data, and multiple @code{qTsP} to get additional pieces. Replies
38620 to these packets generally take the form of the @code{QTDP} packets
38621 that define tracepoints. (FIXME add detailed syntax)
38624 @cindex @samp{qTfV} packet
38626 @cindex @samp{qTsV} packet
38627 These packets request data about trace state variables that are on the
38628 target. @value{GDBN} sends @code{qTfV} to get the first vari of data,
38629 and multiple @code{qTsV} to get additional variables. Replies to
38630 these packets follow the syntax of the @code{QTDV} packets that define
38631 trace state variables.
38637 @cindex @samp{qTfSTM} packet
38638 @cindex @samp{qTsSTM} packet
38639 These packets request data about static tracepoint markers that exist
38640 in the target program. @value{GDBN} sends @code{qTfSTM} to get the
38641 first piece of data, and multiple @code{qTsSTM} to get additional
38642 pieces. Replies to these packets take the following form:
38646 @item m @var{address}:@var{id}:@var{extra}
38648 @item m @var{address}:@var{id}:@var{extra},@var{address}:@var{id}:@var{extra}@dots{}
38649 a comma-separated list of markers
38651 (lower case letter @samp{L}) denotes end of list.
38653 An error occurred. @var{nn} are hex digits.
38655 An empty reply indicates that the request is not supported by the
38659 @var{address} is encoded in hex.
38660 @var{id} and @var{extra} are strings encoded in hex.
38662 In response to each query, the target will reply with a list of one or
38663 more markers, separated by commas. @value{GDBN} will respond to each
38664 reply with a request for more markers (using the @samp{qs} form of the
38665 query), until the target responds with @samp{l} (lower-case ell, for
38668 @item qTSTMat:@var{address}
38670 @cindex @samp{qTSTMat} packet
38671 This packets requests data about static tracepoint markers in the
38672 target program at @var{address}. Replies to this packet follow the
38673 syntax of the @samp{qTfSTM} and @code{qTsSTM} packets that list static
38674 tracepoint markers.
38676 @item QTSave:@var{filename}
38677 @cindex @samp{QTSave} packet
38678 This packet directs the target to save trace data to the file name
38679 @var{filename} in the target's filesystem. @var{filename} is encoded
38680 as a hex string; the interpretation of the file name (relative vs
38681 absolute, wild cards, etc) is up to the target.
38683 @item qTBuffer:@var{offset},@var{len}
38684 @cindex @samp{qTBuffer} packet
38685 Return up to @var{len} bytes of the current contents of trace buffer,
38686 starting at @var{offset}. The trace buffer is treated as if it were
38687 a contiguous collection of traceframes, as per the trace file format.
38688 The reply consists as many hex-encoded bytes as the target can deliver
38689 in a packet; it is not an error to return fewer than were asked for.
38690 A reply consisting of just @code{l} indicates that no bytes are
38693 @item QTBuffer:circular:@var{value}
38694 This packet directs the target to use a circular trace buffer if
38695 @var{value} is 1, or a linear buffer if the value is 0.
38697 @item QTBuffer:size:@var{size}
38698 @anchor{QTBuffer-size}
38699 @cindex @samp{QTBuffer size} packet
38700 This packet directs the target to make the trace buffer be of size
38701 @var{size} if possible. A value of @code{-1} tells the target to
38702 use whatever size it prefers.
38704 @item QTNotes:@r{[}@var{type}:@var{text}@r{]}@r{[};@var{type}:@var{text}@r{]}@dots{}
38705 @cindex @samp{QTNotes} packet
38706 This packet adds optional textual notes to the trace run. Allowable
38707 types include @code{user}, @code{notes}, and @code{tstop}, the
38708 @var{text} fields are arbitrary strings, hex-encoded.
38712 @subsection Relocate instruction reply packet
38713 When installing fast tracepoints in memory, the target may need to
38714 relocate the instruction currently at the tracepoint address to a
38715 different address in memory. For most instructions, a simple copy is
38716 enough, but, for example, call instructions that implicitly push the
38717 return address on the stack, and relative branches or other
38718 PC-relative instructions require offset adjustment, so that the effect
38719 of executing the instruction at a different address is the same as if
38720 it had executed in the original location.
38722 In response to several of the tracepoint packets, the target may also
38723 respond with a number of intermediate @samp{qRelocInsn} request
38724 packets before the final result packet, to have @value{GDBN} handle
38725 this relocation operation. If a packet supports this mechanism, its
38726 documentation will explicitly say so. See for example the above
38727 descriptions for the @samp{QTStart} and @samp{QTDP} packets. The
38728 format of the request is:
38731 @item qRelocInsn:@var{from};@var{to}
38733 This requests @value{GDBN} to copy instruction at address @var{from}
38734 to address @var{to}, possibly adjusted so that executing the
38735 instruction at @var{to} has the same effect as executing it at
38736 @var{from}. @value{GDBN} writes the adjusted instruction to target
38737 memory starting at @var{to}.
38742 @item qRelocInsn:@var{adjusted_size}
38743 Informs the stub the relocation is complete. @var{adjusted_size} is
38744 the length in bytes of resulting relocated instruction sequence.
38746 A badly formed request was detected, or an error was encountered while
38747 relocating the instruction.
38750 @node Host I/O Packets
38751 @section Host I/O Packets
38752 @cindex Host I/O, remote protocol
38753 @cindex file transfer, remote protocol
38755 The @dfn{Host I/O} packets allow @value{GDBN} to perform I/O
38756 operations on the far side of a remote link. For example, Host I/O is
38757 used to upload and download files to a remote target with its own
38758 filesystem. Host I/O uses the same constant values and data structure
38759 layout as the target-initiated File-I/O protocol. However, the
38760 Host I/O packets are structured differently. The target-initiated
38761 protocol relies on target memory to store parameters and buffers.
38762 Host I/O requests are initiated by @value{GDBN}, and the
38763 target's memory is not involved. @xref{File-I/O Remote Protocol
38764 Extension}, for more details on the target-initiated protocol.
38766 The Host I/O request packets all encode a single operation along with
38767 its arguments. They have this format:
38771 @item vFile:@var{operation}: @var{parameter}@dots{}
38772 @var{operation} is the name of the particular request; the target
38773 should compare the entire packet name up to the second colon when checking
38774 for a supported operation. The format of @var{parameter} depends on
38775 the operation. Numbers are always passed in hexadecimal. Negative
38776 numbers have an explicit minus sign (i.e.@: two's complement is not
38777 used). Strings (e.g.@: filenames) are encoded as a series of
38778 hexadecimal bytes. The last argument to a system call may be a
38779 buffer of escaped binary data (@pxref{Binary Data}).
38783 The valid responses to Host I/O packets are:
38787 @item F @var{result} [, @var{errno}] [; @var{attachment}]
38788 @var{result} is the integer value returned by this operation, usually
38789 non-negative for success and -1 for errors. If an error has occured,
38790 @var{errno} will be included in the result. @var{errno} will have a
38791 value defined by the File-I/O protocol (@pxref{Errno Values}). For
38792 operations which return data, @var{attachment} supplies the data as a
38793 binary buffer. Binary buffers in response packets are escaped in the
38794 normal way (@pxref{Binary Data}). See the individual packet
38795 documentation for the interpretation of @var{result} and
38799 An empty response indicates that this operation is not recognized.
38803 These are the supported Host I/O operations:
38806 @item vFile:open: @var{pathname}, @var{flags}, @var{mode}
38807 Open a file at @var{pathname} and return a file descriptor for it, or
38808 return -1 if an error occurs. @var{pathname} is a string,
38809 @var{flags} is an integer indicating a mask of open flags
38810 (@pxref{Open Flags}), and @var{mode} is an integer indicating a mask
38811 of mode bits to use if the file is created (@pxref{mode_t Values}).
38812 @xref{open}, for details of the open flags and mode values.
38814 @item vFile:close: @var{fd}
38815 Close the open file corresponding to @var{fd} and return 0, or
38816 -1 if an error occurs.
38818 @item vFile:pread: @var{fd}, @var{count}, @var{offset}
38819 Read data from the open file corresponding to @var{fd}. Up to
38820 @var{count} bytes will be read from the file, starting at @var{offset}
38821 relative to the start of the file. The target may read fewer bytes;
38822 common reasons include packet size limits and an end-of-file
38823 condition. The number of bytes read is returned. Zero should only be
38824 returned for a successful read at the end of the file, or if
38825 @var{count} was zero.
38827 The data read should be returned as a binary attachment on success.
38828 If zero bytes were read, the response should include an empty binary
38829 attachment (i.e.@: a trailing semicolon). The return value is the
38830 number of target bytes read; the binary attachment may be longer if
38831 some characters were escaped.
38833 @item vFile:pwrite: @var{fd}, @var{offset}, @var{data}
38834 Write @var{data} (a binary buffer) to the open file corresponding
38835 to @var{fd}. Start the write at @var{offset} from the start of the
38836 file. Unlike many @code{write} system calls, there is no
38837 separate @var{count} argument; the length of @var{data} in the
38838 packet is used. @samp{vFile:write} returns the number of bytes written,
38839 which may be shorter than the length of @var{data}, or -1 if an
38842 @item vFile:unlink: @var{pathname}
38843 Delete the file at @var{pathname} on the target. Return 0,
38844 or -1 if an error occurs. @var{pathname} is a string.
38846 @item vFile:readlink: @var{filename}
38847 Read value of symbolic link @var{filename} on the target. Return
38848 the number of bytes read, or -1 if an error occurs.
38850 The data read should be returned as a binary attachment on success.
38851 If zero bytes were read, the response should include an empty binary
38852 attachment (i.e.@: a trailing semicolon). The return value is the
38853 number of target bytes read; the binary attachment may be longer if
38854 some characters were escaped.
38859 @section Interrupts
38860 @cindex interrupts (remote protocol)
38862 When a program on the remote target is running, @value{GDBN} may
38863 attempt to interrupt it by sending a @samp{Ctrl-C}, @code{BREAK} or
38864 a @code{BREAK} followed by @code{g},
38865 control of which is specified via @value{GDBN}'s @samp{interrupt-sequence}.
38867 The precise meaning of @code{BREAK} is defined by the transport
38868 mechanism and may, in fact, be undefined. @value{GDBN} does not
38869 currently define a @code{BREAK} mechanism for any of the network
38870 interfaces except for TCP, in which case @value{GDBN} sends the
38871 @code{telnet} BREAK sequence.
38873 @samp{Ctrl-C}, on the other hand, is defined and implemented for all
38874 transport mechanisms. It is represented by sending the single byte
38875 @code{0x03} without any of the usual packet overhead described in
38876 the Overview section (@pxref{Overview}). When a @code{0x03} byte is
38877 transmitted as part of a packet, it is considered to be packet data
38878 and does @emph{not} represent an interrupt. E.g., an @samp{X} packet
38879 (@pxref{X packet}), used for binary downloads, may include an unescaped
38880 @code{0x03} as part of its packet.
38882 @code{BREAK} followed by @code{g} is also known as Magic SysRq g.
38883 When Linux kernel receives this sequence from serial port,
38884 it stops execution and connects to gdb.
38886 Stubs are not required to recognize these interrupt mechanisms and the
38887 precise meaning associated with receipt of the interrupt is
38888 implementation defined. If the target supports debugging of multiple
38889 threads and/or processes, it should attempt to interrupt all
38890 currently-executing threads and processes.
38891 If the stub is successful at interrupting the
38892 running program, it should send one of the stop
38893 reply packets (@pxref{Stop Reply Packets}) to @value{GDBN} as a result
38894 of successfully stopping the program in all-stop mode, and a stop reply
38895 for each stopped thread in non-stop mode.
38896 Interrupts received while the
38897 program is stopped are discarded.
38899 @node Notification Packets
38900 @section Notification Packets
38901 @cindex notification packets
38902 @cindex packets, notification
38904 The @value{GDBN} remote serial protocol includes @dfn{notifications},
38905 packets that require no acknowledgment. Both the GDB and the stub
38906 may send notifications (although the only notifications defined at
38907 present are sent by the stub). Notifications carry information
38908 without incurring the round-trip latency of an acknowledgment, and so
38909 are useful for low-impact communications where occasional packet loss
38912 A notification packet has the form @samp{% @var{data} #
38913 @var{checksum}}, where @var{data} is the content of the notification,
38914 and @var{checksum} is a checksum of @var{data}, computed and formatted
38915 as for ordinary @value{GDBN} packets. A notification's @var{data}
38916 never contains @samp{$}, @samp{%} or @samp{#} characters. Upon
38917 receiving a notification, the recipient sends no @samp{+} or @samp{-}
38918 to acknowledge the notification's receipt or to report its corruption.
38920 Every notification's @var{data} begins with a name, which contains no
38921 colon characters, followed by a colon character.
38923 Recipients should silently ignore corrupted notifications and
38924 notifications they do not understand. Recipients should restart
38925 timeout periods on receipt of a well-formed notification, whether or
38926 not they understand it.
38928 Senders should only send the notifications described here when this
38929 protocol description specifies that they are permitted. In the
38930 future, we may extend the protocol to permit existing notifications in
38931 new contexts; this rule helps older senders avoid confusing newer
38934 (Older versions of @value{GDBN} ignore bytes received until they see
38935 the @samp{$} byte that begins an ordinary packet, so new stubs may
38936 transmit notifications without fear of confusing older clients. There
38937 are no notifications defined for @value{GDBN} to send at the moment, but we
38938 assume that most older stubs would ignore them, as well.)
38940 Each notification is comprised of three parts:
38942 @item @var{name}:@var{event}
38943 The notification packet is sent by the side that initiates the
38944 exchange (currently, only the stub does that), with @var{event}
38945 carrying the specific information about the notification.
38946 @var{name} is the name of the notification.
38948 The acknowledge sent by the other side, usually @value{GDBN}, to
38949 acknowledge the exchange and request the event.
38952 The purpose of an asynchronous notification mechanism is to report to
38953 @value{GDBN} that something interesting happened in the remote stub.
38955 The remote stub may send notification @var{name}:@var{event}
38956 at any time, but @value{GDBN} acknowledges the notification when
38957 appropriate. The notification event is pending before @value{GDBN}
38958 acknowledges. Only one notification at a time may be pending; if
38959 additional events occur before @value{GDBN} has acknowledged the
38960 previous notification, they must be queued by the stub for later
38961 synchronous transmission in response to @var{ack} packets from
38962 @value{GDBN}. Because the notification mechanism is unreliable,
38963 the stub is permitted to resend a notification if it believes
38964 @value{GDBN} may not have received it.
38966 Specifically, notifications may appear when @value{GDBN} is not
38967 otherwise reading input from the stub, or when @value{GDBN} is
38968 expecting to read a normal synchronous response or a
38969 @samp{+}/@samp{-} acknowledgment to a packet it has sent.
38970 Notification packets are distinct from any other communication from
38971 the stub so there is no ambiguity.
38973 After receiving a notification, @value{GDBN} shall acknowledge it by
38974 sending a @var{ack} packet as a regular, synchronous request to the
38975 stub. Such acknowledgment is not required to happen immediately, as
38976 @value{GDBN} is permitted to send other, unrelated packets to the
38977 stub first, which the stub should process normally.
38979 Upon receiving a @var{ack} packet, if the stub has other queued
38980 events to report to @value{GDBN}, it shall respond by sending a
38981 normal @var{event}. @value{GDBN} shall then send another @var{ack}
38982 packet to solicit further responses; again, it is permitted to send
38983 other, unrelated packets as well which the stub should process
38986 If the stub receives a @var{ack} packet and there are no additional
38987 @var{event} to report, the stub shall return an @samp{OK} response.
38988 At this point, @value{GDBN} has finished processing a notification
38989 and the stub has completed sending any queued events. @value{GDBN}
38990 won't accept any new notifications until the final @samp{OK} is
38991 received . If further notification events occur, the stub shall send
38992 a new notification, @value{GDBN} shall accept the notification, and
38993 the process shall be repeated.
38995 The process of asynchronous notification can be illustrated by the
38998 <- @code{%%Stop:T0505:98e7ffbf;04:4ce6ffbf;08:b1b6e54c;thread:p7526.7526;core:0;}
39001 <- @code{T0505:68f37db7;04:40f37db7;08:63850408;thread:p7526.7528;core:0;}
39003 <- @code{T0505:68e3fdb6;04:40e3fdb6;08:63850408;thread:p7526.7529;core:0;}
39008 The following notifications are defined:
39009 @multitable @columnfractions 0.12 0.12 0.38 0.38
39018 @tab @var{reply}. The @var{reply} has the form of a stop reply, as
39019 described in @ref{Stop Reply Packets}. Refer to @ref{Remote Non-Stop},
39020 for information on how these notifications are acknowledged by
39022 @tab Report an asynchronous stop event in non-stop mode.
39026 @node Remote Non-Stop
39027 @section Remote Protocol Support for Non-Stop Mode
39029 @value{GDBN}'s remote protocol supports non-stop debugging of
39030 multi-threaded programs, as described in @ref{Non-Stop Mode}. If the stub
39031 supports non-stop mode, it should report that to @value{GDBN} by including
39032 @samp{QNonStop+} in its @samp{qSupported} response (@pxref{qSupported}).
39034 @value{GDBN} typically sends a @samp{QNonStop} packet only when
39035 establishing a new connection with the stub. Entering non-stop mode
39036 does not alter the state of any currently-running threads, but targets
39037 must stop all threads in any already-attached processes when entering
39038 all-stop mode. @value{GDBN} uses the @samp{?} packet as necessary to
39039 probe the target state after a mode change.
39041 In non-stop mode, when an attached process encounters an event that
39042 would otherwise be reported with a stop reply, it uses the
39043 asynchronous notification mechanism (@pxref{Notification Packets}) to
39044 inform @value{GDBN}. In contrast to all-stop mode, where all threads
39045 in all processes are stopped when a stop reply is sent, in non-stop
39046 mode only the thread reporting the stop event is stopped. That is,
39047 when reporting a @samp{S} or @samp{T} response to indicate completion
39048 of a step operation, hitting a breakpoint, or a fault, only the
39049 affected thread is stopped; any other still-running threads continue
39050 to run. When reporting a @samp{W} or @samp{X} response, all running
39051 threads belonging to other attached processes continue to run.
39053 In non-stop mode, the target shall respond to the @samp{?} packet as
39054 follows. First, any incomplete stop reply notification/@samp{vStopped}
39055 sequence in progress is abandoned. The target must begin a new
39056 sequence reporting stop events for all stopped threads, whether or not
39057 it has previously reported those events to @value{GDBN}. The first
39058 stop reply is sent as a synchronous reply to the @samp{?} packet, and
39059 subsequent stop replies are sent as responses to @samp{vStopped} packets
39060 using the mechanism described above. The target must not send
39061 asynchronous stop reply notifications until the sequence is complete.
39062 If all threads are running when the target receives the @samp{?} packet,
39063 or if the target is not attached to any process, it shall respond
39066 @node Packet Acknowledgment
39067 @section Packet Acknowledgment
39069 @cindex acknowledgment, for @value{GDBN} remote
39070 @cindex packet acknowledgment, for @value{GDBN} remote
39071 By default, when either the host or the target machine receives a packet,
39072 the first response expected is an acknowledgment: either @samp{+} (to indicate
39073 the package was received correctly) or @samp{-} (to request retransmission).
39074 This mechanism allows the @value{GDBN} remote protocol to operate over
39075 unreliable transport mechanisms, such as a serial line.
39077 In cases where the transport mechanism is itself reliable (such as a pipe or
39078 TCP connection), the @samp{+}/@samp{-} acknowledgments are redundant.
39079 It may be desirable to disable them in that case to reduce communication
39080 overhead, or for other reasons. This can be accomplished by means of the
39081 @samp{QStartNoAckMode} packet; @pxref{QStartNoAckMode}.
39083 When in no-acknowledgment mode, neither the stub nor @value{GDBN} shall send or
39084 expect @samp{+}/@samp{-} protocol acknowledgments. The packet
39085 and response format still includes the normal checksum, as described in
39086 @ref{Overview}, but the checksum may be ignored by the receiver.
39088 If the stub supports @samp{QStartNoAckMode} and prefers to operate in
39089 no-acknowledgment mode, it should report that to @value{GDBN}
39090 by including @samp{QStartNoAckMode+} in its response to @samp{qSupported};
39091 @pxref{qSupported}.
39092 If @value{GDBN} also supports @samp{QStartNoAckMode} and it has not been
39093 disabled via the @code{set remote noack-packet off} command
39094 (@pxref{Remote Configuration}),
39095 @value{GDBN} may then send a @samp{QStartNoAckMode} packet to the stub.
39096 Only then may the stub actually turn off packet acknowledgments.
39097 @value{GDBN} sends a final @samp{+} acknowledgment of the stub's @samp{OK}
39098 response, which can be safely ignored by the stub.
39100 Note that @code{set remote noack-packet} command only affects negotiation
39101 between @value{GDBN} and the stub when subsequent connections are made;
39102 it does not affect the protocol acknowledgment state for any current
39104 Since @samp{+}/@samp{-} acknowledgments are enabled by default when a
39105 new connection is established,
39106 there is also no protocol request to re-enable the acknowledgments
39107 for the current connection, once disabled.
39112 Example sequence of a target being re-started. Notice how the restart
39113 does not get any direct output:
39118 @emph{target restarts}
39121 <- @code{T001:1234123412341234}
39125 Example sequence of a target being stepped by a single instruction:
39128 -> @code{G1445@dots{}}
39133 <- @code{T001:1234123412341234}
39137 <- @code{1455@dots{}}
39141 @node File-I/O Remote Protocol Extension
39142 @section File-I/O Remote Protocol Extension
39143 @cindex File-I/O remote protocol extension
39146 * File-I/O Overview::
39147 * Protocol Basics::
39148 * The F Request Packet::
39149 * The F Reply Packet::
39150 * The Ctrl-C Message::
39152 * List of Supported Calls::
39153 * Protocol-specific Representation of Datatypes::
39155 * File-I/O Examples::
39158 @node File-I/O Overview
39159 @subsection File-I/O Overview
39160 @cindex file-i/o overview
39162 The @dfn{File I/O remote protocol extension} (short: File-I/O) allows the
39163 target to use the host's file system and console I/O to perform various
39164 system calls. System calls on the target system are translated into a
39165 remote protocol packet to the host system, which then performs the needed
39166 actions and returns a response packet to the target system.
39167 This simulates file system operations even on targets that lack file systems.
39169 The protocol is defined to be independent of both the host and target systems.
39170 It uses its own internal representation of datatypes and values. Both
39171 @value{GDBN} and the target's @value{GDBN} stub are responsible for
39172 translating the system-dependent value representations into the internal
39173 protocol representations when data is transmitted.
39175 The communication is synchronous. A system call is possible only when
39176 @value{GDBN} is waiting for a response from the @samp{C}, @samp{c}, @samp{S}
39177 or @samp{s} packets. While @value{GDBN} handles the request for a system call,
39178 the target is stopped to allow deterministic access to the target's
39179 memory. Therefore File-I/O is not interruptible by target signals. On
39180 the other hand, it is possible to interrupt File-I/O by a user interrupt
39181 (@samp{Ctrl-C}) within @value{GDBN}.
39183 The target's request to perform a host system call does not finish
39184 the latest @samp{C}, @samp{c}, @samp{S} or @samp{s} action. That means,
39185 after finishing the system call, the target returns to continuing the
39186 previous activity (continue, step). No additional continue or step
39187 request from @value{GDBN} is required.
39190 (@value{GDBP}) continue
39191 <- target requests 'system call X'
39192 target is stopped, @value{GDBN} executes system call
39193 -> @value{GDBN} returns result
39194 ... target continues, @value{GDBN} returns to wait for the target
39195 <- target hits breakpoint and sends a Txx packet
39198 The protocol only supports I/O on the console and to regular files on
39199 the host file system. Character or block special devices, pipes,
39200 named pipes, sockets or any other communication method on the host
39201 system are not supported by this protocol.
39203 File I/O is not supported in non-stop mode.
39205 @node Protocol Basics
39206 @subsection Protocol Basics
39207 @cindex protocol basics, file-i/o
39209 The File-I/O protocol uses the @code{F} packet as the request as well
39210 as reply packet. Since a File-I/O system call can only occur when
39211 @value{GDBN} is waiting for a response from the continuing or stepping target,
39212 the File-I/O request is a reply that @value{GDBN} has to expect as a result
39213 of a previous @samp{C}, @samp{c}, @samp{S} or @samp{s} packet.
39214 This @code{F} packet contains all information needed to allow @value{GDBN}
39215 to call the appropriate host system call:
39219 A unique identifier for the requested system call.
39222 All parameters to the system call. Pointers are given as addresses
39223 in the target memory address space. Pointers to strings are given as
39224 pointer/length pair. Numerical values are given as they are.
39225 Numerical control flags are given in a protocol-specific representation.
39229 At this point, @value{GDBN} has to perform the following actions.
39233 If the parameters include pointer values to data needed as input to a
39234 system call, @value{GDBN} requests this data from the target with a
39235 standard @code{m} packet request. This additional communication has to be
39236 expected by the target implementation and is handled as any other @code{m}
39240 @value{GDBN} translates all value from protocol representation to host
39241 representation as needed. Datatypes are coerced into the host types.
39244 @value{GDBN} calls the system call.
39247 It then coerces datatypes back to protocol representation.
39250 If the system call is expected to return data in buffer space specified
39251 by pointer parameters to the call, the data is transmitted to the
39252 target using a @code{M} or @code{X} packet. This packet has to be expected
39253 by the target implementation and is handled as any other @code{M} or @code{X}
39258 Eventually @value{GDBN} replies with another @code{F} packet which contains all
39259 necessary information for the target to continue. This at least contains
39266 @code{errno}, if has been changed by the system call.
39273 After having done the needed type and value coercion, the target continues
39274 the latest continue or step action.
39276 @node The F Request Packet
39277 @subsection The @code{F} Request Packet
39278 @cindex file-i/o request packet
39279 @cindex @code{F} request packet
39281 The @code{F} request packet has the following format:
39284 @item F@var{call-id},@var{parameter@dots{}}
39286 @var{call-id} is the identifier to indicate the host system call to be called.
39287 This is just the name of the function.
39289 @var{parameter@dots{}} are the parameters to the system call.
39290 Parameters are hexadecimal integer values, either the actual values in case
39291 of scalar datatypes, pointers to target buffer space in case of compound
39292 datatypes and unspecified memory areas, or pointer/length pairs in case
39293 of string parameters. These are appended to the @var{call-id} as a
39294 comma-delimited list. All values are transmitted in ASCII
39295 string representation, pointer/length pairs separated by a slash.
39301 @node The F Reply Packet
39302 @subsection The @code{F} Reply Packet
39303 @cindex file-i/o reply packet
39304 @cindex @code{F} reply packet
39306 The @code{F} reply packet has the following format:
39310 @item F@var{retcode},@var{errno},@var{Ctrl-C flag};@var{call-specific attachment}
39312 @var{retcode} is the return code of the system call as hexadecimal value.
39314 @var{errno} is the @code{errno} set by the call, in protocol-specific
39316 This parameter can be omitted if the call was successful.
39318 @var{Ctrl-C flag} is only sent if the user requested a break. In this
39319 case, @var{errno} must be sent as well, even if the call was successful.
39320 The @var{Ctrl-C flag} itself consists of the character @samp{C}:
39327 or, if the call was interrupted before the host call has been performed:
39334 assuming 4 is the protocol-specific representation of @code{EINTR}.
39339 @node The Ctrl-C Message
39340 @subsection The @samp{Ctrl-C} Message
39341 @cindex ctrl-c message, in file-i/o protocol
39343 If the @samp{Ctrl-C} flag is set in the @value{GDBN}
39344 reply packet (@pxref{The F Reply Packet}),
39345 the target should behave as if it had
39346 gotten a break message. The meaning for the target is ``system call
39347 interrupted by @code{SIGINT}''. Consequentially, the target should actually stop
39348 (as with a break message) and return to @value{GDBN} with a @code{T02}
39351 It's important for the target to know in which
39352 state the system call was interrupted. There are two possible cases:
39356 The system call hasn't been performed on the host yet.
39359 The system call on the host has been finished.
39363 These two states can be distinguished by the target by the value of the
39364 returned @code{errno}. If it's the protocol representation of @code{EINTR}, the system
39365 call hasn't been performed. This is equivalent to the @code{EINTR} handling
39366 on POSIX systems. In any other case, the target may presume that the
39367 system call has been finished --- successfully or not --- and should behave
39368 as if the break message arrived right after the system call.
39370 @value{GDBN} must behave reliably. If the system call has not been called
39371 yet, @value{GDBN} may send the @code{F} reply immediately, setting @code{EINTR} as
39372 @code{errno} in the packet. If the system call on the host has been finished
39373 before the user requests a break, the full action must be finished by
39374 @value{GDBN}. This requires sending @code{M} or @code{X} packets as necessary.
39375 The @code{F} packet may only be sent when either nothing has happened
39376 or the full action has been completed.
39379 @subsection Console I/O
39380 @cindex console i/o as part of file-i/o
39382 By default and if not explicitly closed by the target system, the file
39383 descriptors 0, 1 and 2 are connected to the @value{GDBN} console. Output
39384 on the @value{GDBN} console is handled as any other file output operation
39385 (@code{write(1, @dots{})} or @code{write(2, @dots{})}). Console input is handled
39386 by @value{GDBN} so that after the target read request from file descriptor
39387 0 all following typing is buffered until either one of the following
39392 The user types @kbd{Ctrl-c}. The behaviour is as explained above, and the
39394 system call is treated as finished.
39397 The user presses @key{RET}. This is treated as end of input with a trailing
39401 The user types @kbd{Ctrl-d}. This is treated as end of input. No trailing
39402 character (neither newline nor @samp{Ctrl-D}) is appended to the input.
39406 If the user has typed more characters than fit in the buffer given to
39407 the @code{read} call, the trailing characters are buffered in @value{GDBN} until
39408 either another @code{read(0, @dots{})} is requested by the target, or debugging
39409 is stopped at the user's request.
39412 @node List of Supported Calls
39413 @subsection List of Supported Calls
39414 @cindex list of supported file-i/o calls
39431 @unnumberedsubsubsec open
39432 @cindex open, file-i/o system call
39437 int open(const char *pathname, int flags);
39438 int open(const char *pathname, int flags, mode_t mode);
39442 @samp{Fopen,@var{pathptr}/@var{len},@var{flags},@var{mode}}
39445 @var{flags} is the bitwise @code{OR} of the following values:
39449 If the file does not exist it will be created. The host
39450 rules apply as far as file ownership and time stamps
39454 When used with @code{O_CREAT}, if the file already exists it is
39455 an error and open() fails.
39458 If the file already exists and the open mode allows
39459 writing (@code{O_RDWR} or @code{O_WRONLY} is given) it will be
39460 truncated to zero length.
39463 The file is opened in append mode.
39466 The file is opened for reading only.
39469 The file is opened for writing only.
39472 The file is opened for reading and writing.
39476 Other bits are silently ignored.
39480 @var{mode} is the bitwise @code{OR} of the following values:
39484 User has read permission.
39487 User has write permission.
39490 Group has read permission.
39493 Group has write permission.
39496 Others have read permission.
39499 Others have write permission.
39503 Other bits are silently ignored.
39506 @item Return value:
39507 @code{open} returns the new file descriptor or -1 if an error
39514 @var{pathname} already exists and @code{O_CREAT} and @code{O_EXCL} were used.
39517 @var{pathname} refers to a directory.
39520 The requested access is not allowed.
39523 @var{pathname} was too long.
39526 A directory component in @var{pathname} does not exist.
39529 @var{pathname} refers to a device, pipe, named pipe or socket.
39532 @var{pathname} refers to a file on a read-only filesystem and
39533 write access was requested.
39536 @var{pathname} is an invalid pointer value.
39539 No space on device to create the file.
39542 The process already has the maximum number of files open.
39545 The limit on the total number of files open on the system
39549 The call was interrupted by the user.
39555 @unnumberedsubsubsec close
39556 @cindex close, file-i/o system call
39565 @samp{Fclose,@var{fd}}
39567 @item Return value:
39568 @code{close} returns zero on success, or -1 if an error occurred.
39574 @var{fd} isn't a valid open file descriptor.
39577 The call was interrupted by the user.
39583 @unnumberedsubsubsec read
39584 @cindex read, file-i/o system call
39589 int read(int fd, void *buf, unsigned int count);
39593 @samp{Fread,@var{fd},@var{bufptr},@var{count}}
39595 @item Return value:
39596 On success, the number of bytes read is returned.
39597 Zero indicates end of file. If count is zero, read
39598 returns zero as well. On error, -1 is returned.
39604 @var{fd} is not a valid file descriptor or is not open for
39608 @var{bufptr} is an invalid pointer value.
39611 The call was interrupted by the user.
39617 @unnumberedsubsubsec write
39618 @cindex write, file-i/o system call
39623 int write(int fd, const void *buf, unsigned int count);
39627 @samp{Fwrite,@var{fd},@var{bufptr},@var{count}}
39629 @item Return value:
39630 On success, the number of bytes written are returned.
39631 Zero indicates nothing was written. On error, -1
39638 @var{fd} is not a valid file descriptor or is not open for
39642 @var{bufptr} is an invalid pointer value.
39645 An attempt was made to write a file that exceeds the
39646 host-specific maximum file size allowed.
39649 No space on device to write the data.
39652 The call was interrupted by the user.
39658 @unnumberedsubsubsec lseek
39659 @cindex lseek, file-i/o system call
39664 long lseek (int fd, long offset, int flag);
39668 @samp{Flseek,@var{fd},@var{offset},@var{flag}}
39670 @var{flag} is one of:
39674 The offset is set to @var{offset} bytes.
39677 The offset is set to its current location plus @var{offset}
39681 The offset is set to the size of the file plus @var{offset}
39685 @item Return value:
39686 On success, the resulting unsigned offset in bytes from
39687 the beginning of the file is returned. Otherwise, a
39688 value of -1 is returned.
39694 @var{fd} is not a valid open file descriptor.
39697 @var{fd} is associated with the @value{GDBN} console.
39700 @var{flag} is not a proper value.
39703 The call was interrupted by the user.
39709 @unnumberedsubsubsec rename
39710 @cindex rename, file-i/o system call
39715 int rename(const char *oldpath, const char *newpath);
39719 @samp{Frename,@var{oldpathptr}/@var{len},@var{newpathptr}/@var{len}}
39721 @item Return value:
39722 On success, zero is returned. On error, -1 is returned.
39728 @var{newpath} is an existing directory, but @var{oldpath} is not a
39732 @var{newpath} is a non-empty directory.
39735 @var{oldpath} or @var{newpath} is a directory that is in use by some
39739 An attempt was made to make a directory a subdirectory
39743 A component used as a directory in @var{oldpath} or new
39744 path is not a directory. Or @var{oldpath} is a directory
39745 and @var{newpath} exists but is not a directory.
39748 @var{oldpathptr} or @var{newpathptr} are invalid pointer values.
39751 No access to the file or the path of the file.
39755 @var{oldpath} or @var{newpath} was too long.
39758 A directory component in @var{oldpath} or @var{newpath} does not exist.
39761 The file is on a read-only filesystem.
39764 The device containing the file has no room for the new
39768 The call was interrupted by the user.
39774 @unnumberedsubsubsec unlink
39775 @cindex unlink, file-i/o system call
39780 int unlink(const char *pathname);
39784 @samp{Funlink,@var{pathnameptr}/@var{len}}
39786 @item Return value:
39787 On success, zero is returned. On error, -1 is returned.
39793 No access to the file or the path of the file.
39796 The system does not allow unlinking of directories.
39799 The file @var{pathname} cannot be unlinked because it's
39800 being used by another process.
39803 @var{pathnameptr} is an invalid pointer value.
39806 @var{pathname} was too long.
39809 A directory component in @var{pathname} does not exist.
39812 A component of the path is not a directory.
39815 The file is on a read-only filesystem.
39818 The call was interrupted by the user.
39824 @unnumberedsubsubsec stat/fstat
39825 @cindex fstat, file-i/o system call
39826 @cindex stat, file-i/o system call
39831 int stat(const char *pathname, struct stat *buf);
39832 int fstat(int fd, struct stat *buf);
39836 @samp{Fstat,@var{pathnameptr}/@var{len},@var{bufptr}}@*
39837 @samp{Ffstat,@var{fd},@var{bufptr}}
39839 @item Return value:
39840 On success, zero is returned. On error, -1 is returned.
39846 @var{fd} is not a valid open file.
39849 A directory component in @var{pathname} does not exist or the
39850 path is an empty string.
39853 A component of the path is not a directory.
39856 @var{pathnameptr} is an invalid pointer value.
39859 No access to the file or the path of the file.
39862 @var{pathname} was too long.
39865 The call was interrupted by the user.
39871 @unnumberedsubsubsec gettimeofday
39872 @cindex gettimeofday, file-i/o system call
39877 int gettimeofday(struct timeval *tv, void *tz);
39881 @samp{Fgettimeofday,@var{tvptr},@var{tzptr}}
39883 @item Return value:
39884 On success, 0 is returned, -1 otherwise.
39890 @var{tz} is a non-NULL pointer.
39893 @var{tvptr} and/or @var{tzptr} is an invalid pointer value.
39899 @unnumberedsubsubsec isatty
39900 @cindex isatty, file-i/o system call
39905 int isatty(int fd);
39909 @samp{Fisatty,@var{fd}}
39911 @item Return value:
39912 Returns 1 if @var{fd} refers to the @value{GDBN} console, 0 otherwise.
39918 The call was interrupted by the user.
39923 Note that the @code{isatty} call is treated as a special case: it returns
39924 1 to the target if the file descriptor is attached
39925 to the @value{GDBN} console, 0 otherwise. Implementing through system calls
39926 would require implementing @code{ioctl} and would be more complex than
39931 @unnumberedsubsubsec system
39932 @cindex system, file-i/o system call
39937 int system(const char *command);
39941 @samp{Fsystem,@var{commandptr}/@var{len}}
39943 @item Return value:
39944 If @var{len} is zero, the return value indicates whether a shell is
39945 available. A zero return value indicates a shell is not available.
39946 For non-zero @var{len}, the value returned is -1 on error and the
39947 return status of the command otherwise. Only the exit status of the
39948 command is returned, which is extracted from the host's @code{system}
39949 return value by calling @code{WEXITSTATUS(retval)}. In case
39950 @file{/bin/sh} could not be executed, 127 is returned.
39956 The call was interrupted by the user.
39961 @value{GDBN} takes over the full task of calling the necessary host calls
39962 to perform the @code{system} call. The return value of @code{system} on
39963 the host is simplified before it's returned
39964 to the target. Any termination signal information from the child process
39965 is discarded, and the return value consists
39966 entirely of the exit status of the called command.
39968 Due to security concerns, the @code{system} call is by default refused
39969 by @value{GDBN}. The user has to allow this call explicitly with the
39970 @code{set remote system-call-allowed 1} command.
39973 @item set remote system-call-allowed
39974 @kindex set remote system-call-allowed
39975 Control whether to allow the @code{system} calls in the File I/O
39976 protocol for the remote target. The default is zero (disabled).
39978 @item show remote system-call-allowed
39979 @kindex show remote system-call-allowed
39980 Show whether the @code{system} calls are allowed in the File I/O
39984 @node Protocol-specific Representation of Datatypes
39985 @subsection Protocol-specific Representation of Datatypes
39986 @cindex protocol-specific representation of datatypes, in file-i/o protocol
39989 * Integral Datatypes::
39991 * Memory Transfer::
39996 @node Integral Datatypes
39997 @unnumberedsubsubsec Integral Datatypes
39998 @cindex integral datatypes, in file-i/o protocol
40000 The integral datatypes used in the system calls are @code{int},
40001 @code{unsigned int}, @code{long}, @code{unsigned long},
40002 @code{mode_t}, and @code{time_t}.
40004 @code{int}, @code{unsigned int}, @code{mode_t} and @code{time_t} are
40005 implemented as 32 bit values in this protocol.
40007 @code{long} and @code{unsigned long} are implemented as 64 bit types.
40009 @xref{Limits}, for corresponding MIN and MAX values (similar to those
40010 in @file{limits.h}) to allow range checking on host and target.
40012 @code{time_t} datatypes are defined as seconds since the Epoch.
40014 All integral datatypes transferred as part of a memory read or write of a
40015 structured datatype e.g.@: a @code{struct stat} have to be given in big endian
40018 @node Pointer Values
40019 @unnumberedsubsubsec Pointer Values
40020 @cindex pointer values, in file-i/o protocol
40022 Pointers to target data are transmitted as they are. An exception
40023 is made for pointers to buffers for which the length isn't
40024 transmitted as part of the function call, namely strings. Strings
40025 are transmitted as a pointer/length pair, both as hex values, e.g.@:
40032 which is a pointer to data of length 18 bytes at position 0x1aaf.
40033 The length is defined as the full string length in bytes, including
40034 the trailing null byte. For example, the string @code{"hello world"}
40035 at address 0x123456 is transmitted as
40041 @node Memory Transfer
40042 @unnumberedsubsubsec Memory Transfer
40043 @cindex memory transfer, in file-i/o protocol
40045 Structured data which is transferred using a memory read or write (for
40046 example, a @code{struct stat}) is expected to be in a protocol-specific format
40047 with all scalar multibyte datatypes being big endian. Translation to
40048 this representation needs to be done both by the target before the @code{F}
40049 packet is sent, and by @value{GDBN} before
40050 it transfers memory to the target. Transferred pointers to structured
40051 data should point to the already-coerced data at any time.
40055 @unnumberedsubsubsec struct stat
40056 @cindex struct stat, in file-i/o protocol
40058 The buffer of type @code{struct stat} used by the target and @value{GDBN}
40059 is defined as follows:
40063 unsigned int st_dev; /* device */
40064 unsigned int st_ino; /* inode */
40065 mode_t st_mode; /* protection */
40066 unsigned int st_nlink; /* number of hard links */
40067 unsigned int st_uid; /* user ID of owner */
40068 unsigned int st_gid; /* group ID of owner */
40069 unsigned int st_rdev; /* device type (if inode device) */
40070 unsigned long st_size; /* total size, in bytes */
40071 unsigned long st_blksize; /* blocksize for filesystem I/O */
40072 unsigned long st_blocks; /* number of blocks allocated */
40073 time_t st_atime; /* time of last access */
40074 time_t st_mtime; /* time of last modification */
40075 time_t st_ctime; /* time of last change */
40079 The integral datatypes conform to the definitions given in the
40080 appropriate section (see @ref{Integral Datatypes}, for details) so this
40081 structure is of size 64 bytes.
40083 The values of several fields have a restricted meaning and/or
40089 A value of 0 represents a file, 1 the console.
40092 No valid meaning for the target. Transmitted unchanged.
40095 Valid mode bits are described in @ref{Constants}. Any other
40096 bits have currently no meaning for the target.
40101 No valid meaning for the target. Transmitted unchanged.
40106 These values have a host and file system dependent
40107 accuracy. Especially on Windows hosts, the file system may not
40108 support exact timing values.
40111 The target gets a @code{struct stat} of the above representation and is
40112 responsible for coercing it to the target representation before
40115 Note that due to size differences between the host, target, and protocol
40116 representations of @code{struct stat} members, these members could eventually
40117 get truncated on the target.
40119 @node struct timeval
40120 @unnumberedsubsubsec struct timeval
40121 @cindex struct timeval, in file-i/o protocol
40123 The buffer of type @code{struct timeval} used by the File-I/O protocol
40124 is defined as follows:
40128 time_t tv_sec; /* second */
40129 long tv_usec; /* microsecond */
40133 The integral datatypes conform to the definitions given in the
40134 appropriate section (see @ref{Integral Datatypes}, for details) so this
40135 structure is of size 8 bytes.
40138 @subsection Constants
40139 @cindex constants, in file-i/o protocol
40141 The following values are used for the constants inside of the
40142 protocol. @value{GDBN} and target are responsible for translating these
40143 values before and after the call as needed.
40154 @unnumberedsubsubsec Open Flags
40155 @cindex open flags, in file-i/o protocol
40157 All values are given in hexadecimal representation.
40169 @node mode_t Values
40170 @unnumberedsubsubsec mode_t Values
40171 @cindex mode_t values, in file-i/o protocol
40173 All values are given in octal representation.
40190 @unnumberedsubsubsec Errno Values
40191 @cindex errno values, in file-i/o protocol
40193 All values are given in decimal representation.
40218 @code{EUNKNOWN} is used as a fallback error value if a host system returns
40219 any error value not in the list of supported error numbers.
40222 @unnumberedsubsubsec Lseek Flags
40223 @cindex lseek flags, in file-i/o protocol
40232 @unnumberedsubsubsec Limits
40233 @cindex limits, in file-i/o protocol
40235 All values are given in decimal representation.
40238 INT_MIN -2147483648
40240 UINT_MAX 4294967295
40241 LONG_MIN -9223372036854775808
40242 LONG_MAX 9223372036854775807
40243 ULONG_MAX 18446744073709551615
40246 @node File-I/O Examples
40247 @subsection File-I/O Examples
40248 @cindex file-i/o examples
40250 Example sequence of a write call, file descriptor 3, buffer is at target
40251 address 0x1234, 6 bytes should be written:
40254 <- @code{Fwrite,3,1234,6}
40255 @emph{request memory read from target}
40258 @emph{return "6 bytes written"}
40262 Example sequence of a read call, file descriptor 3, buffer is at target
40263 address 0x1234, 6 bytes should be read:
40266 <- @code{Fread,3,1234,6}
40267 @emph{request memory write to target}
40268 -> @code{X1234,6:XXXXXX}
40269 @emph{return "6 bytes read"}
40273 Example sequence of a read call, call fails on the host due to invalid
40274 file descriptor (@code{EBADF}):
40277 <- @code{Fread,3,1234,6}
40281 Example sequence of a read call, user presses @kbd{Ctrl-c} before syscall on
40285 <- @code{Fread,3,1234,6}
40290 Example sequence of a read call, user presses @kbd{Ctrl-c} after syscall on
40294 <- @code{Fread,3,1234,6}
40295 -> @code{X1234,6:XXXXXX}
40299 @node Library List Format
40300 @section Library List Format
40301 @cindex library list format, remote protocol
40303 On some platforms, a dynamic loader (e.g.@: @file{ld.so}) runs in the
40304 same process as your application to manage libraries. In this case,
40305 @value{GDBN} can use the loader's symbol table and normal memory
40306 operations to maintain a list of shared libraries. On other
40307 platforms, the operating system manages loaded libraries.
40308 @value{GDBN} can not retrieve the list of currently loaded libraries
40309 through memory operations, so it uses the @samp{qXfer:libraries:read}
40310 packet (@pxref{qXfer library list read}) instead. The remote stub
40311 queries the target's operating system and reports which libraries
40314 The @samp{qXfer:libraries:read} packet returns an XML document which
40315 lists loaded libraries and their offsets. Each library has an
40316 associated name and one or more segment or section base addresses,
40317 which report where the library was loaded in memory.
40319 For the common case of libraries that are fully linked binaries, the
40320 library should have a list of segments. If the target supports
40321 dynamic linking of a relocatable object file, its library XML element
40322 should instead include a list of allocated sections. The segment or
40323 section bases are start addresses, not relocation offsets; they do not
40324 depend on the library's link-time base addresses.
40326 @value{GDBN} must be linked with the Expat library to support XML
40327 library lists. @xref{Expat}.
40329 A simple memory map, with one loaded library relocated by a single
40330 offset, looks like this:
40334 <library name="/lib/libc.so.6">
40335 <segment address="0x10000000"/>
40340 Another simple memory map, with one loaded library with three
40341 allocated sections (.text, .data, .bss), looks like this:
40345 <library name="sharedlib.o">
40346 <section address="0x10000000"/>
40347 <section address="0x20000000"/>
40348 <section address="0x30000000"/>
40353 The format of a library list is described by this DTD:
40356 <!-- library-list: Root element with versioning -->
40357 <!ELEMENT library-list (library)*>
40358 <!ATTLIST library-list version CDATA #FIXED "1.0">
40359 <!ELEMENT library (segment*, section*)>
40360 <!ATTLIST library name CDATA #REQUIRED>
40361 <!ELEMENT segment EMPTY>
40362 <!ATTLIST segment address CDATA #REQUIRED>
40363 <!ELEMENT section EMPTY>
40364 <!ATTLIST section address CDATA #REQUIRED>
40367 In addition, segments and section descriptors cannot be mixed within a
40368 single library element, and you must supply at least one segment or
40369 section for each library.
40371 @node Library List Format for SVR4 Targets
40372 @section Library List Format for SVR4 Targets
40373 @cindex library list format, remote protocol
40375 On SVR4 platforms @value{GDBN} can use the symbol table of a dynamic loader
40376 (e.g.@: @file{ld.so}) and normal memory operations to maintain a list of
40377 shared libraries. Still a special library list provided by this packet is
40378 more efficient for the @value{GDBN} remote protocol.
40380 The @samp{qXfer:libraries-svr4:read} packet returns an XML document which lists
40381 loaded libraries and their SVR4 linker parameters. For each library on SVR4
40382 target, the following parameters are reported:
40386 @code{name}, the absolute file name from the @code{l_name} field of
40387 @code{struct link_map}.
40389 @code{lm} with address of @code{struct link_map} used for TLS
40390 (Thread Local Storage) access.
40392 @code{l_addr}, the displacement as read from the field @code{l_addr} of
40393 @code{struct link_map}. For prelinked libraries this is not an absolute
40394 memory address. It is a displacement of absolute memory address against
40395 address the file was prelinked to during the library load.
40397 @code{l_ld}, which is memory address of the @code{PT_DYNAMIC} segment
40400 Additionally the single @code{main-lm} attribute specifies address of
40401 @code{struct link_map} used for the main executable. This parameter is used
40402 for TLS access and its presence is optional.
40404 @value{GDBN} must be linked with the Expat library to support XML
40405 SVR4 library lists. @xref{Expat}.
40407 A simple memory map, with two loaded libraries (which do not use prelink),
40411 <library-list-svr4 version="1.0" main-lm="0xe4f8f8">
40412 <library name="/lib/ld-linux.so.2" lm="0xe4f51c" l_addr="0xe2d000"
40414 <library name="/lib/libc.so.6" lm="0xe4fbe8" l_addr="0x154000"
40416 </library-list-svr>
40419 The format of an SVR4 library list is described by this DTD:
40422 <!-- library-list-svr4: Root element with versioning -->
40423 <!ELEMENT library-list-svr4 (library)*>
40424 <!ATTLIST library-list-svr4 version CDATA #FIXED "1.0">
40425 <!ATTLIST library-list-svr4 main-lm CDATA #IMPLIED>
40426 <!ELEMENT library EMPTY>
40427 <!ATTLIST library name CDATA #REQUIRED>
40428 <!ATTLIST library lm CDATA #REQUIRED>
40429 <!ATTLIST library l_addr CDATA #REQUIRED>
40430 <!ATTLIST library l_ld CDATA #REQUIRED>
40433 @node Memory Map Format
40434 @section Memory Map Format
40435 @cindex memory map format
40437 To be able to write into flash memory, @value{GDBN} needs to obtain a
40438 memory map from the target. This section describes the format of the
40441 The memory map is obtained using the @samp{qXfer:memory-map:read}
40442 (@pxref{qXfer memory map read}) packet and is an XML document that
40443 lists memory regions.
40445 @value{GDBN} must be linked with the Expat library to support XML
40446 memory maps. @xref{Expat}.
40448 The top-level structure of the document is shown below:
40451 <?xml version="1.0"?>
40452 <!DOCTYPE memory-map
40453 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40454 "http://sourceware.org/gdb/gdb-memory-map.dtd">
40460 Each region can be either:
40465 A region of RAM starting at @var{addr} and extending for @var{length}
40469 <memory type="ram" start="@var{addr}" length="@var{length}"/>
40474 A region of read-only memory:
40477 <memory type="rom" start="@var{addr}" length="@var{length}"/>
40482 A region of flash memory, with erasure blocks @var{blocksize}
40486 <memory type="flash" start="@var{addr}" length="@var{length}">
40487 <property name="blocksize">@var{blocksize}</property>
40493 Regions must not overlap. @value{GDBN} assumes that areas of memory not covered
40494 by the memory map are RAM, and uses the ordinary @samp{M} and @samp{X}
40495 packets to write to addresses in such ranges.
40497 The formal DTD for memory map format is given below:
40500 <!-- ................................................... -->
40501 <!-- Memory Map XML DTD ................................ -->
40502 <!-- File: memory-map.dtd .............................. -->
40503 <!-- .................................... .............. -->
40504 <!-- memory-map.dtd -->
40505 <!-- memory-map: Root element with versioning -->
40506 <!ELEMENT memory-map (memory | property)>
40507 <!ATTLIST memory-map version CDATA #FIXED "1.0.0">
40508 <!ELEMENT memory (property)>
40509 <!-- memory: Specifies a memory region,
40510 and its type, or device. -->
40511 <!ATTLIST memory type CDATA #REQUIRED
40512 start CDATA #REQUIRED
40513 length CDATA #REQUIRED
40514 device CDATA #IMPLIED>
40515 <!-- property: Generic attribute tag -->
40516 <!ELEMENT property (#PCDATA | property)*>
40517 <!ATTLIST property name CDATA #REQUIRED>
40520 @node Thread List Format
40521 @section Thread List Format
40522 @cindex thread list format
40524 To efficiently update the list of threads and their attributes,
40525 @value{GDBN} issues the @samp{qXfer:threads:read} packet
40526 (@pxref{qXfer threads read}) and obtains the XML document with
40527 the following structure:
40530 <?xml version="1.0"?>
40532 <thread id="id" core="0">
40533 ... description ...
40538 Each @samp{thread} element must have the @samp{id} attribute that
40539 identifies the thread (@pxref{thread-id syntax}). The
40540 @samp{core} attribute, if present, specifies which processor core
40541 the thread was last executing on. The content of the of @samp{thread}
40542 element is interpreted as human-readable auxilliary information.
40544 @node Traceframe Info Format
40545 @section Traceframe Info Format
40546 @cindex traceframe info format
40548 To be able to know which objects in the inferior can be examined when
40549 inspecting a tracepoint hit, @value{GDBN} needs to obtain the list of
40550 memory ranges, registers and trace state variables that have been
40551 collected in a traceframe.
40553 This list is obtained using the @samp{qXfer:traceframe-info:read}
40554 (@pxref{qXfer traceframe info read}) packet and is an XML document.
40556 @value{GDBN} must be linked with the Expat library to support XML
40557 traceframe info discovery. @xref{Expat}.
40559 The top-level structure of the document is shown below:
40562 <?xml version="1.0"?>
40563 <!DOCTYPE traceframe-info
40564 PUBLIC "+//IDN gnu.org//DTD GDB Memory Map V1.0//EN"
40565 "http://sourceware.org/gdb/gdb-traceframe-info.dtd">
40571 Each traceframe block can be either:
40576 A region of collected memory starting at @var{addr} and extending for
40577 @var{length} bytes from there:
40580 <memory start="@var{addr}" length="@var{length}"/>
40585 The formal DTD for the traceframe info format is given below:
40588 <!ELEMENT traceframe-info (memory)* >
40589 <!ATTLIST traceframe-info version CDATA #FIXED "1.0">
40591 <!ELEMENT memory EMPTY>
40592 <!ATTLIST memory start CDATA #REQUIRED
40593 length CDATA #REQUIRED>
40596 @node Branch Trace Format
40597 @section Branch Trace Format
40598 @cindex branch trace format
40600 In order to display the branch trace of an inferior thread,
40601 @value{GDBN} needs to obtain the list of branches. This list is
40602 represented as list of sequential code blocks that are connected via
40603 branches. The code in each block has been executed sequentially.
40605 This list is obtained using the @samp{qXfer:btrace:read}
40606 (@pxref{qXfer btrace read}) packet and is an XML document.
40608 @value{GDBN} must be linked with the Expat library to support XML
40609 traceframe info discovery. @xref{Expat}.
40611 The top-level structure of the document is shown below:
40614 <?xml version="1.0"?>
40616 PUBLIC "+//IDN gnu.org//DTD GDB Branch Trace V1.0//EN"
40617 "http://sourceware.org/gdb/gdb-btrace.dtd">
40626 A block of sequentially executed instructions starting at @var{begin}
40627 and ending at @var{end}:
40630 <block begin="@var{begin}" end="@var{end}"/>
40635 The formal DTD for the branch trace format is given below:
40638 <!ELEMENT btrace (block)* >
40639 <!ATTLIST btrace version CDATA #FIXED "1.0">
40641 <!ELEMENT block EMPTY>
40642 <!ATTLIST block begin CDATA #REQUIRED
40643 end CDATA #REQUIRED>
40646 @include agentexpr.texi
40648 @node Target Descriptions
40649 @appendix Target Descriptions
40650 @cindex target descriptions
40652 One of the challenges of using @value{GDBN} to debug embedded systems
40653 is that there are so many minor variants of each processor
40654 architecture in use. It is common practice for vendors to start with
40655 a standard processor core --- ARM, PowerPC, or @acronym{MIPS}, for example ---
40656 and then make changes to adapt it to a particular market niche. Some
40657 architectures have hundreds of variants, available from dozens of
40658 vendors. This leads to a number of problems:
40662 With so many different customized processors, it is difficult for
40663 the @value{GDBN} maintainers to keep up with the changes.
40665 Since individual variants may have short lifetimes or limited
40666 audiences, it may not be worthwhile to carry information about every
40667 variant in the @value{GDBN} source tree.
40669 When @value{GDBN} does support the architecture of the embedded system
40670 at hand, the task of finding the correct architecture name to give the
40671 @command{set architecture} command can be error-prone.
40674 To address these problems, the @value{GDBN} remote protocol allows a
40675 target system to not only identify itself to @value{GDBN}, but to
40676 actually describe its own features. This lets @value{GDBN} support
40677 processor variants it has never seen before --- to the extent that the
40678 descriptions are accurate, and that @value{GDBN} understands them.
40680 @value{GDBN} must be linked with the Expat library to support XML
40681 target descriptions. @xref{Expat}.
40684 * Retrieving Descriptions:: How descriptions are fetched from a target.
40685 * Target Description Format:: The contents of a target description.
40686 * Predefined Target Types:: Standard types available for target
40688 * Standard Target Features:: Features @value{GDBN} knows about.
40691 @node Retrieving Descriptions
40692 @section Retrieving Descriptions
40694 Target descriptions can be read from the target automatically, or
40695 specified by the user manually. The default behavior is to read the
40696 description from the target. @value{GDBN} retrieves it via the remote
40697 protocol using @samp{qXfer} requests (@pxref{General Query Packets,
40698 qXfer}). The @var{annex} in the @samp{qXfer} packet will be
40699 @samp{target.xml}. The contents of the @samp{target.xml} annex are an
40700 XML document, of the form described in @ref{Target Description
40703 Alternatively, you can specify a file to read for the target description.
40704 If a file is set, the target will not be queried. The commands to
40705 specify a file are:
40708 @cindex set tdesc filename
40709 @item set tdesc filename @var{path}
40710 Read the target description from @var{path}.
40712 @cindex unset tdesc filename
40713 @item unset tdesc filename
40714 Do not read the XML target description from a file. @value{GDBN}
40715 will use the description supplied by the current target.
40717 @cindex show tdesc filename
40718 @item show tdesc filename
40719 Show the filename to read for a target description, if any.
40723 @node Target Description Format
40724 @section Target Description Format
40725 @cindex target descriptions, XML format
40727 A target description annex is an @uref{http://www.w3.org/XML/, XML}
40728 document which complies with the Document Type Definition provided in
40729 the @value{GDBN} sources in @file{gdb/features/gdb-target.dtd}. This
40730 means you can use generally available tools like @command{xmllint} to
40731 check that your feature descriptions are well-formed and valid.
40732 However, to help people unfamiliar with XML write descriptions for
40733 their targets, we also describe the grammar here.
40735 Target descriptions can identify the architecture of the remote target
40736 and (for some architectures) provide information about custom register
40737 sets. They can also identify the OS ABI of the remote target.
40738 @value{GDBN} can use this information to autoconfigure for your
40739 target, or to warn you if you connect to an unsupported target.
40741 Here is a simple target description:
40744 <target version="1.0">
40745 <architecture>i386:x86-64</architecture>
40750 This minimal description only says that the target uses
40751 the x86-64 architecture.
40753 A target description has the following overall form, with [ ] marking
40754 optional elements and @dots{} marking repeatable elements. The elements
40755 are explained further below.
40758 <?xml version="1.0"?>
40759 <!DOCTYPE target SYSTEM "gdb-target.dtd">
40760 <target version="1.0">
40761 @r{[}@var{architecture}@r{]}
40762 @r{[}@var{osabi}@r{]}
40763 @r{[}@var{compatible}@r{]}
40764 @r{[}@var{feature}@dots{}@r{]}
40769 The description is generally insensitive to whitespace and line
40770 breaks, under the usual common-sense rules. The XML version
40771 declaration and document type declaration can generally be omitted
40772 (@value{GDBN} does not require them), but specifying them may be
40773 useful for XML validation tools. The @samp{version} attribute for
40774 @samp{<target>} may also be omitted, but we recommend
40775 including it; if future versions of @value{GDBN} use an incompatible
40776 revision of @file{gdb-target.dtd}, they will detect and report
40777 the version mismatch.
40779 @subsection Inclusion
40780 @cindex target descriptions, inclusion
40783 @cindex <xi:include>
40786 It can sometimes be valuable to split a target description up into
40787 several different annexes, either for organizational purposes, or to
40788 share files between different possible target descriptions. You can
40789 divide a description into multiple files by replacing any element of
40790 the target description with an inclusion directive of the form:
40793 <xi:include href="@var{document}"/>
40797 When @value{GDBN} encounters an element of this form, it will retrieve
40798 the named XML @var{document}, and replace the inclusion directive with
40799 the contents of that document. If the current description was read
40800 using @samp{qXfer}, then so will be the included document;
40801 @var{document} will be interpreted as the name of an annex. If the
40802 current description was read from a file, @value{GDBN} will look for
40803 @var{document} as a file in the same directory where it found the
40804 original description.
40806 @subsection Architecture
40807 @cindex <architecture>
40809 An @samp{<architecture>} element has this form:
40812 <architecture>@var{arch}</architecture>
40815 @var{arch} is one of the architectures from the set accepted by
40816 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40819 @cindex @code{<osabi>}
40821 This optional field was introduced in @value{GDBN} version 7.0.
40822 Previous versions of @value{GDBN} ignore it.
40824 An @samp{<osabi>} element has this form:
40827 <osabi>@var{abi-name}</osabi>
40830 @var{abi-name} is an OS ABI name from the same selection accepted by
40831 @w{@code{set osabi}} (@pxref{ABI, ,Configuring the Current ABI}).
40833 @subsection Compatible Architecture
40834 @cindex @code{<compatible>}
40836 This optional field was introduced in @value{GDBN} version 7.0.
40837 Previous versions of @value{GDBN} ignore it.
40839 A @samp{<compatible>} element has this form:
40842 <compatible>@var{arch}</compatible>
40845 @var{arch} is one of the architectures from the set accepted by
40846 @code{set architecture} (@pxref{Targets, ,Specifying a Debugging Target}).
40848 A @samp{<compatible>} element is used to specify that the target
40849 is able to run binaries in some other than the main target architecture
40850 given by the @samp{<architecture>} element. For example, on the
40851 Cell Broadband Engine, the main architecture is @code{powerpc:common}
40852 or @code{powerpc:common64}, but the system is able to run binaries
40853 in the @code{spu} architecture as well. The way to describe this
40854 capability with @samp{<compatible>} is as follows:
40857 <architecture>powerpc:common</architecture>
40858 <compatible>spu</compatible>
40861 @subsection Features
40864 Each @samp{<feature>} describes some logical portion of the target
40865 system. Features are currently used to describe available CPU
40866 registers and the types of their contents. A @samp{<feature>} element
40870 <feature name="@var{name}">
40871 @r{[}@var{type}@dots{}@r{]}
40877 Each feature's name should be unique within the description. The name
40878 of a feature does not matter unless @value{GDBN} has some special
40879 knowledge of the contents of that feature; if it does, the feature
40880 should have its standard name. @xref{Standard Target Features}.
40884 Any register's value is a collection of bits which @value{GDBN} must
40885 interpret. The default interpretation is a two's complement integer,
40886 but other types can be requested by name in the register description.
40887 Some predefined types are provided by @value{GDBN} (@pxref{Predefined
40888 Target Types}), and the description can define additional composite types.
40890 Each type element must have an @samp{id} attribute, which gives
40891 a unique (within the containing @samp{<feature>}) name to the type.
40892 Types must be defined before they are used.
40895 Some targets offer vector registers, which can be treated as arrays
40896 of scalar elements. These types are written as @samp{<vector>} elements,
40897 specifying the array element type, @var{type}, and the number of elements,
40901 <vector id="@var{id}" type="@var{type}" count="@var{count}"/>
40905 If a register's value is usefully viewed in multiple ways, define it
40906 with a union type containing the useful representations. The
40907 @samp{<union>} element contains one or more @samp{<field>} elements,
40908 each of which has a @var{name} and a @var{type}:
40911 <union id="@var{id}">
40912 <field name="@var{name}" type="@var{type}"/>
40918 If a register's value is composed from several separate values, define
40919 it with a structure type. There are two forms of the @samp{<struct>}
40920 element; a @samp{<struct>} element must either contain only bitfields
40921 or contain no bitfields. If the structure contains only bitfields,
40922 its total size in bytes must be specified, each bitfield must have an
40923 explicit start and end, and bitfields are automatically assigned an
40924 integer type. The field's @var{start} should be less than or
40925 equal to its @var{end}, and zero represents the least significant bit.
40928 <struct id="@var{id}" size="@var{size}">
40929 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40934 If the structure contains no bitfields, then each field has an
40935 explicit type, and no implicit padding is added.
40938 <struct id="@var{id}">
40939 <field name="@var{name}" type="@var{type}"/>
40945 If a register's value is a series of single-bit flags, define it with
40946 a flags type. The @samp{<flags>} element has an explicit @var{size}
40947 and contains one or more @samp{<field>} elements. Each field has a
40948 @var{name}, a @var{start}, and an @var{end}. Only single-bit flags
40952 <flags id="@var{id}" size="@var{size}">
40953 <field name="@var{name}" start="@var{start}" end="@var{end}"/>
40958 @subsection Registers
40961 Each register is represented as an element with this form:
40964 <reg name="@var{name}"
40965 bitsize="@var{size}"
40966 @r{[}regnum="@var{num}"@r{]}
40967 @r{[}save-restore="@var{save-restore}"@r{]}
40968 @r{[}type="@var{type}"@r{]}
40969 @r{[}group="@var{group}"@r{]}/>
40973 The components are as follows:
40978 The register's name; it must be unique within the target description.
40981 The register's size, in bits.
40984 The register's number. If omitted, a register's number is one greater
40985 than that of the previous register (either in the current feature or in
40986 a preceding feature); the first register in the target description
40987 defaults to zero. This register number is used to read or write
40988 the register; e.g.@: it is used in the remote @code{p} and @code{P}
40989 packets, and registers appear in the @code{g} and @code{G} packets
40990 in order of increasing register number.
40993 Whether the register should be preserved across inferior function
40994 calls; this must be either @code{yes} or @code{no}. The default is
40995 @code{yes}, which is appropriate for most registers except for
40996 some system control registers; this is not related to the target's
41000 The type of the register. @var{type} may be a predefined type, a type
41001 defined in the current feature, or one of the special types @code{int}
41002 and @code{float}. @code{int} is an integer type of the correct size
41003 for @var{bitsize}, and @code{float} is a floating point type (in the
41004 architecture's normal floating point format) of the correct size for
41005 @var{bitsize}. The default is @code{int}.
41008 The register group to which this register belongs. @var{group} must
41009 be either @code{general}, @code{float}, or @code{vector}. If no
41010 @var{group} is specified, @value{GDBN} will not display the register
41011 in @code{info registers}.
41015 @node Predefined Target Types
41016 @section Predefined Target Types
41017 @cindex target descriptions, predefined types
41019 Type definitions in the self-description can build up composite types
41020 from basic building blocks, but can not define fundamental types. Instead,
41021 standard identifiers are provided by @value{GDBN} for the fundamental
41022 types. The currently supported types are:
41031 Signed integer types holding the specified number of bits.
41038 Unsigned integer types holding the specified number of bits.
41042 Pointers to unspecified code and data. The program counter and
41043 any dedicated return address register may be marked as code
41044 pointers; printing a code pointer converts it into a symbolic
41045 address. The stack pointer and any dedicated address registers
41046 may be marked as data pointers.
41049 Single precision IEEE floating point.
41052 Double precision IEEE floating point.
41055 The 12-byte extended precision format used by ARM FPA registers.
41058 The 10-byte extended precision format used by x87 registers.
41061 32bit @sc{eflags} register used by x86.
41064 32bit @sc{mxcsr} register used by x86.
41068 @node Standard Target Features
41069 @section Standard Target Features
41070 @cindex target descriptions, standard features
41072 A target description must contain either no registers or all the
41073 target's registers. If the description contains no registers, then
41074 @value{GDBN} will assume a default register layout, selected based on
41075 the architecture. If the description contains any registers, the
41076 default layout will not be used; the standard registers must be
41077 described in the target description, in such a way that @value{GDBN}
41078 can recognize them.
41080 This is accomplished by giving specific names to feature elements
41081 which contain standard registers. @value{GDBN} will look for features
41082 with those names and verify that they contain the expected registers;
41083 if any known feature is missing required registers, or if any required
41084 feature is missing, @value{GDBN} will reject the target
41085 description. You can add additional registers to any of the
41086 standard features --- @value{GDBN} will display them just as if
41087 they were added to an unrecognized feature.
41089 This section lists the known features and their expected contents.
41090 Sample XML documents for these features are included in the
41091 @value{GDBN} source tree, in the directory @file{gdb/features}.
41093 Names recognized by @value{GDBN} should include the name of the
41094 company or organization which selected the name, and the overall
41095 architecture to which the feature applies; so e.g.@: the feature
41096 containing ARM core registers is named @samp{org.gnu.gdb.arm.core}.
41098 The names of registers are not case sensitive for the purpose
41099 of recognizing standard features, but @value{GDBN} will only display
41100 registers using the capitalization used in the description.
41103 * AArch64 Features::
41108 * PowerPC Features::
41113 @node AArch64 Features
41114 @subsection AArch64 Features
41115 @cindex target descriptions, AArch64 features
41117 The @samp{org.gnu.gdb.aarch64.core} feature is required for AArch64
41118 targets. It should contain registers @samp{x0} through @samp{x30},
41119 @samp{sp}, @samp{pc}, and @samp{cpsr}.
41121 The @samp{org.gnu.gdb.aarch64.fpu} feature is optional. If present,
41122 it should contain registers @samp{v0} through @samp{v31}, @samp{fpsr},
41126 @subsection ARM Features
41127 @cindex target descriptions, ARM features
41129 The @samp{org.gnu.gdb.arm.core} feature is required for non-M-profile
41131 It should contain registers @samp{r0} through @samp{r13}, @samp{sp},
41132 @samp{lr}, @samp{pc}, and @samp{cpsr}.
41134 For M-profile targets (e.g. Cortex-M3), the @samp{org.gnu.gdb.arm.core}
41135 feature is replaced by @samp{org.gnu.gdb.arm.m-profile}. It should contain
41136 registers @samp{r0} through @samp{r13}, @samp{sp}, @samp{lr}, @samp{pc},
41139 The @samp{org.gnu.gdb.arm.fpa} feature is optional. If present, it
41140 should contain registers @samp{f0} through @samp{f7} and @samp{fps}.
41142 The @samp{org.gnu.gdb.xscale.iwmmxt} feature is optional. If present,
41143 it should contain at least registers @samp{wR0} through @samp{wR15} and
41144 @samp{wCGR0} through @samp{wCGR3}. The @samp{wCID}, @samp{wCon},
41145 @samp{wCSSF}, and @samp{wCASF} registers are optional.
41147 The @samp{org.gnu.gdb.arm.vfp} feature is optional. If present, it
41148 should contain at least registers @samp{d0} through @samp{d15}. If
41149 they are present, @samp{d16} through @samp{d31} should also be included.
41150 @value{GDBN} will synthesize the single-precision registers from
41151 halves of the double-precision registers.
41153 The @samp{org.gnu.gdb.arm.neon} feature is optional. It does not
41154 need to contain registers; it instructs @value{GDBN} to display the
41155 VFP double-precision registers as vectors and to synthesize the
41156 quad-precision registers from pairs of double-precision registers.
41157 If this feature is present, @samp{org.gnu.gdb.arm.vfp} must also
41158 be present and include 32 double-precision registers.
41160 @node i386 Features
41161 @subsection i386 Features
41162 @cindex target descriptions, i386 features
41164 The @samp{org.gnu.gdb.i386.core} feature is required for i386/amd64
41165 targets. It should describe the following registers:
41169 @samp{eax} through @samp{edi} plus @samp{eip} for i386
41171 @samp{rax} through @samp{r15} plus @samp{rip} for amd64
41173 @samp{eflags}, @samp{cs}, @samp{ss}, @samp{ds}, @samp{es},
41174 @samp{fs}, @samp{gs}
41176 @samp{st0} through @samp{st7}
41178 @samp{fctrl}, @samp{fstat}, @samp{ftag}, @samp{fiseg}, @samp{fioff},
41179 @samp{foseg}, @samp{fooff} and @samp{fop}
41182 The register sets may be different, depending on the target.
41184 The @samp{org.gnu.gdb.i386.sse} feature is optional. It should
41185 describe registers:
41189 @samp{xmm0} through @samp{xmm7} for i386
41191 @samp{xmm0} through @samp{xmm15} for amd64
41196 The @samp{org.gnu.gdb.i386.avx} feature is optional and requires the
41197 @samp{org.gnu.gdb.i386.sse} feature. It should
41198 describe the upper 128 bits of @sc{ymm} registers:
41202 @samp{ymm0h} through @samp{ymm7h} for i386
41204 @samp{ymm0h} through @samp{ymm15h} for amd64
41207 The @samp{org.gnu.gdb.i386.linux} feature is optional. It should
41208 describe a single register, @samp{orig_eax}.
41210 @node MIPS Features
41211 @subsection @acronym{MIPS} Features
41212 @cindex target descriptions, @acronym{MIPS} features
41214 The @samp{org.gnu.gdb.mips.cpu} feature is required for @acronym{MIPS} targets.
41215 It should contain registers @samp{r0} through @samp{r31}, @samp{lo},
41216 @samp{hi}, and @samp{pc}. They may be 32-bit or 64-bit depending
41219 The @samp{org.gnu.gdb.mips.cp0} feature is also required. It should
41220 contain at least the @samp{status}, @samp{badvaddr}, and @samp{cause}
41221 registers. They may be 32-bit or 64-bit depending on the target.
41223 The @samp{org.gnu.gdb.mips.fpu} feature is currently required, though
41224 it may be optional in a future version of @value{GDBN}. It should
41225 contain registers @samp{f0} through @samp{f31}, @samp{fcsr}, and
41226 @samp{fir}. They may be 32-bit or 64-bit depending on the target.
41228 The @samp{org.gnu.gdb.mips.dsp} feature is optional. It should
41229 contain registers @samp{hi1} through @samp{hi3}, @samp{lo1} through
41230 @samp{lo3}, and @samp{dspctl}. The @samp{dspctl} register should
41231 be 32-bit and the rest may be 32-bit or 64-bit depending on the target.
41233 The @samp{org.gnu.gdb.mips.linux} feature is optional. It should
41234 contain a single register, @samp{restart}, which is used by the
41235 Linux kernel to control restartable syscalls.
41237 @node M68K Features
41238 @subsection M68K Features
41239 @cindex target descriptions, M68K features
41242 @item @samp{org.gnu.gdb.m68k.core}
41243 @itemx @samp{org.gnu.gdb.coldfire.core}
41244 @itemx @samp{org.gnu.gdb.fido.core}
41245 One of those features must be always present.
41246 The feature that is present determines which flavor of m68k is
41247 used. The feature that is present should contain registers
41248 @samp{d0} through @samp{d7}, @samp{a0} through @samp{a5}, @samp{fp},
41249 @samp{sp}, @samp{ps} and @samp{pc}.
41251 @item @samp{org.gnu.gdb.coldfire.fp}
41252 This feature is optional. If present, it should contain registers
41253 @samp{fp0} through @samp{fp7}, @samp{fpcontrol}, @samp{fpstatus} and
41257 @node PowerPC Features
41258 @subsection PowerPC Features
41259 @cindex target descriptions, PowerPC features
41261 The @samp{org.gnu.gdb.power.core} feature is required for PowerPC
41262 targets. It should contain registers @samp{r0} through @samp{r31},
41263 @samp{pc}, @samp{msr}, @samp{cr}, @samp{lr}, @samp{ctr}, and
41264 @samp{xer}. They may be 32-bit or 64-bit depending on the target.
41266 The @samp{org.gnu.gdb.power.fpu} feature is optional. It should
41267 contain registers @samp{f0} through @samp{f31} and @samp{fpscr}.
41269 The @samp{org.gnu.gdb.power.altivec} feature is optional. It should
41270 contain registers @samp{vr0} through @samp{vr31}, @samp{vscr},
41273 The @samp{org.gnu.gdb.power.vsx} feature is optional. It should
41274 contain registers @samp{vs0h} through @samp{vs31h}. @value{GDBN}
41275 will combine these registers with the floating point registers
41276 (@samp{f0} through @samp{f31}) and the altivec registers (@samp{vr0}
41277 through @samp{vr31}) to present the 128-bit wide registers @samp{vs0}
41278 through @samp{vs63}, the set of vector registers for POWER7.
41280 The @samp{org.gnu.gdb.power.spe} feature is optional. It should
41281 contain registers @samp{ev0h} through @samp{ev31h}, @samp{acc}, and
41282 @samp{spefscr}. SPE targets should provide 32-bit registers in
41283 @samp{org.gnu.gdb.power.core} and provide the upper halves in
41284 @samp{ev0h} through @samp{ev31h}. @value{GDBN} will combine
41285 these to present registers @samp{ev0} through @samp{ev31} to the
41288 @node TIC6x Features
41289 @subsection TMS320C6x Features
41290 @cindex target descriptions, TIC6x features
41291 @cindex target descriptions, TMS320C6x features
41292 The @samp{org.gnu.gdb.tic6x.core} feature is required for TMS320C6x
41293 targets. It should contain registers @samp{A0} through @samp{A15},
41294 registers @samp{B0} through @samp{B15}, @samp{CSR} and @samp{PC}.
41296 The @samp{org.gnu.gdb.tic6x.gp} feature is optional. It should
41297 contain registers @samp{A16} through @samp{A31} and @samp{B16}
41298 through @samp{B31}.
41300 The @samp{org.gnu.gdb.tic6x.c6xp} feature is optional. It should
41301 contain registers @samp{TSR}, @samp{ILC} and @samp{RILC}.
41303 @node Operating System Information
41304 @appendix Operating System Information
41305 @cindex operating system information
41311 Users of @value{GDBN} often wish to obtain information about the state of
41312 the operating system running on the target---for example the list of
41313 processes, or the list of open files. This section describes the
41314 mechanism that makes it possible. This mechanism is similar to the
41315 target features mechanism (@pxref{Target Descriptions}), but focuses
41316 on a different aspect of target.
41318 Operating system information is retrived from the target via the
41319 remote protocol, using @samp{qXfer} requests (@pxref{qXfer osdata
41320 read}). The object name in the request should be @samp{osdata}, and
41321 the @var{annex} identifies the data to be fetched.
41324 @appendixsection Process list
41325 @cindex operating system information, process list
41327 When requesting the process list, the @var{annex} field in the
41328 @samp{qXfer} request should be @samp{processes}. The returned data is
41329 an XML document. The formal syntax of this document is defined in
41330 @file{gdb/features/osdata.dtd}.
41332 An example document is:
41335 <?xml version="1.0"?>
41336 <!DOCTYPE target SYSTEM "osdata.dtd">
41337 <osdata type="processes">
41339 <column name="pid">1</column>
41340 <column name="user">root</column>
41341 <column name="command">/sbin/init</column>
41342 <column name="cores">1,2,3</column>
41347 Each item should include a column whose name is @samp{pid}. The value
41348 of that column should identify the process on the target. The
41349 @samp{user} and @samp{command} columns are optional, and will be
41350 displayed by @value{GDBN}. The @samp{cores} column, if present,
41351 should contain a comma-separated list of cores that this process
41352 is running on. Target may provide additional columns,
41353 which @value{GDBN} currently ignores.
41355 @node Trace File Format
41356 @appendix Trace File Format
41357 @cindex trace file format
41359 The trace file comes in three parts: a header, a textual description
41360 section, and a trace frame section with binary data.
41362 The header has the form @code{\x7fTRACE0\n}. The first byte is
41363 @code{0x7f} so as to indicate that the file contains binary data,
41364 while the @code{0} is a version number that may have different values
41367 The description section consists of multiple lines of @sc{ascii} text
41368 separated by newline characters (@code{0xa}). The lines may include a
41369 variety of optional descriptive or context-setting information, such
41370 as tracepoint definitions or register set size. @value{GDBN} will
41371 ignore any line that it does not recognize. An empty line marks the end
41374 @c FIXME add some specific types of data
41376 The trace frame section consists of a number of consecutive frames.
41377 Each frame begins with a two-byte tracepoint number, followed by a
41378 four-byte size giving the amount of data in the frame. The data in
41379 the frame consists of a number of blocks, each introduced by a
41380 character indicating its type (at least register, memory, and trace
41381 state variable). The data in this section is raw binary, not a
41382 hexadecimal or other encoding; its endianness matches the target's
41385 @c FIXME bi-arch may require endianness/arch info in description section
41388 @item R @var{bytes}
41389 Register block. The number and ordering of bytes matches that of a
41390 @code{g} packet in the remote protocol. Note that these are the
41391 actual bytes, in target order and @value{GDBN} register order, not a
41392 hexadecimal encoding.
41394 @item M @var{address} @var{length} @var{bytes}...
41395 Memory block. This is a contiguous block of memory, at the 8-byte
41396 address @var{address}, with a 2-byte length @var{length}, followed by
41397 @var{length} bytes.
41399 @item V @var{number} @var{value}
41400 Trace state variable block. This records the 8-byte signed value
41401 @var{value} of trace state variable numbered @var{number}.
41405 Future enhancements of the trace file format may include additional types
41408 @node Index Section Format
41409 @appendix @code{.gdb_index} section format
41410 @cindex .gdb_index section format
41411 @cindex index section format
41413 This section documents the index section that is created by @code{save
41414 gdb-index} (@pxref{Index Files}). The index section is
41415 DWARF-specific; some knowledge of DWARF is assumed in this
41418 The mapped index file format is designed to be directly
41419 @code{mmap}able on any architecture. In most cases, a datum is
41420 represented using a little-endian 32-bit integer value, called an
41421 @code{offset_type}. Big endian machines must byte-swap the values
41422 before using them. Exceptions to this rule are noted. The data is
41423 laid out such that alignment is always respected.
41425 A mapped index consists of several areas, laid out in order.
41429 The file header. This is a sequence of values, of @code{offset_type}
41430 unless otherwise noted:
41434 The version number, currently 8. Versions 1, 2 and 3 are obsolete.
41435 Version 4 uses a different hashing function from versions 5 and 6.
41436 Version 6 includes symbols for inlined functions, whereas versions 4
41437 and 5 do not. Version 7 adds attributes to the CU indices in the
41438 symbol table. Version 8 specifies that symbols from DWARF type units
41439 (@samp{DW_TAG_type_unit}) refer to the type unit's symbol table and not the
41440 compilation unit (@samp{DW_TAG_comp_unit}) using the type.
41442 @value{GDBN} will only read version 4, 5, or 6 indices
41443 by specifying @code{set use-deprecated-index-sections on}.
41444 GDB has a workaround for potentially broken version 7 indices so it is
41445 currently not flagged as deprecated.
41448 The offset, from the start of the file, of the CU list.
41451 The offset, from the start of the file, of the types CU list. Note
41452 that this area can be empty, in which case this offset will be equal
41453 to the next offset.
41456 The offset, from the start of the file, of the address area.
41459 The offset, from the start of the file, of the symbol table.
41462 The offset, from the start of the file, of the constant pool.
41466 The CU list. This is a sequence of pairs of 64-bit little-endian
41467 values, sorted by the CU offset. The first element in each pair is
41468 the offset of a CU in the @code{.debug_info} section. The second
41469 element in each pair is the length of that CU. References to a CU
41470 elsewhere in the map are done using a CU index, which is just the
41471 0-based index into this table. Note that if there are type CUs, then
41472 conceptually CUs and type CUs form a single list for the purposes of
41476 The types CU list. This is a sequence of triplets of 64-bit
41477 little-endian values. In a triplet, the first value is the CU offset,
41478 the second value is the type offset in the CU, and the third value is
41479 the type signature. The types CU list is not sorted.
41482 The address area. The address area consists of a sequence of address
41483 entries. Each address entry has three elements:
41487 The low address. This is a 64-bit little-endian value.
41490 The high address. This is a 64-bit little-endian value. Like
41491 @code{DW_AT_high_pc}, the value is one byte beyond the end.
41494 The CU index. This is an @code{offset_type} value.
41498 The symbol table. This is an open-addressed hash table. The size of
41499 the hash table is always a power of 2.
41501 Each slot in the hash table consists of a pair of @code{offset_type}
41502 values. The first value is the offset of the symbol's name in the
41503 constant pool. The second value is the offset of the CU vector in the
41506 If both values are 0, then this slot in the hash table is empty. This
41507 is ok because while 0 is a valid constant pool index, it cannot be a
41508 valid index for both a string and a CU vector.
41510 The hash value for a table entry is computed by applying an
41511 iterative hash function to the symbol's name. Starting with an
41512 initial value of @code{r = 0}, each (unsigned) character @samp{c} in
41513 the string is incorporated into the hash using the formula depending on the
41518 The formula is @code{r = r * 67 + c - 113}.
41520 @item Versions 5 to 7
41521 The formula is @code{r = r * 67 + tolower (c) - 113}.
41524 The terminating @samp{\0} is not incorporated into the hash.
41526 The step size used in the hash table is computed via
41527 @code{((hash * 17) & (size - 1)) | 1}, where @samp{hash} is the hash
41528 value, and @samp{size} is the size of the hash table. The step size
41529 is used to find the next candidate slot when handling a hash
41532 The names of C@t{++} symbols in the hash table are canonicalized. We
41533 don't currently have a simple description of the canonicalization
41534 algorithm; if you intend to create new index sections, you must read
41538 The constant pool. This is simply a bunch of bytes. It is organized
41539 so that alignment is correct: CU vectors are stored first, followed by
41542 A CU vector in the constant pool is a sequence of @code{offset_type}
41543 values. The first value is the number of CU indices in the vector.
41544 Each subsequent value is the index and symbol attributes of a CU in
41545 the CU list. This element in the hash table is used to indicate which
41546 CUs define the symbol and how the symbol is used.
41547 See below for the format of each CU index+attributes entry.
41549 A string in the constant pool is zero-terminated.
41552 Attributes were added to CU index values in @code{.gdb_index} version 7.
41553 If a symbol has multiple uses within a CU then there is one
41554 CU index+attributes value for each use.
41556 The format of each CU index+attributes entry is as follows
41562 This is the index of the CU in the CU list.
41564 These bits are reserved for future purposes and must be zero.
41566 The kind of the symbol in the CU.
41570 This value is reserved and should not be used.
41571 By reserving zero the full @code{offset_type} value is backwards compatible
41572 with previous versions of the index.
41574 The symbol is a type.
41576 The symbol is a variable or an enum value.
41578 The symbol is a function.
41580 Any other kind of symbol.
41582 These values are reserved.
41586 This bit is zero if the value is global and one if it is static.
41588 The determination of whether a symbol is global or static is complicated.
41589 The authorative reference is the file @file{dwarf2read.c} in
41590 @value{GDBN} sources.
41594 This pseudo-code describes the computation of a symbol's kind and
41595 global/static attributes in the index.
41598 is_external = get_attribute (die, DW_AT_external);
41599 language = get_attribute (cu_die, DW_AT_language);
41602 case DW_TAG_typedef:
41603 case DW_TAG_base_type:
41604 case DW_TAG_subrange_type:
41608 case DW_TAG_enumerator:
41610 is_static = (language != CPLUS && language != JAVA);
41612 case DW_TAG_subprogram:
41614 is_static = ! (is_external || language == ADA);
41616 case DW_TAG_constant:
41618 is_static = ! is_external;
41620 case DW_TAG_variable:
41622 is_static = ! is_external;
41624 case DW_TAG_namespace:
41628 case DW_TAG_class_type:
41629 case DW_TAG_interface_type:
41630 case DW_TAG_structure_type:
41631 case DW_TAG_union_type:
41632 case DW_TAG_enumeration_type:
41634 is_static = (language != CPLUS && language != JAVA);
41643 @node GNU Free Documentation License
41644 @appendix GNU Free Documentation License
41647 @node Concept Index
41648 @unnumbered Concept Index
41652 @node Command and Variable Index
41653 @unnumbered Command, Variable, and Function Index
41658 % I think something like @@colophon should be in texinfo. In the
41660 \long\def\colophon{\hbox to0pt{}\vfill
41661 \centerline{The body of this manual is set in}
41662 \centerline{\fontname\tenrm,}
41663 \centerline{with headings in {\bf\fontname\tenbf}}
41664 \centerline{and examples in {\tt\fontname\tentt}.}
41665 \centerline{{\it\fontname\tenit\/},}
41666 \centerline{{\bf\fontname\tenbf}, and}
41667 \centerline{{\sl\fontname\tensl\/}}
41668 \centerline{are used for emphasis.}\vfill}
41670 % Blame: doc@@cygnus.com, 1991.